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Master the very latest clinical and technical information on the full range of anterior cruciate ligament reconstruction techniques. Both inside the remarkably user-friendly printed version of this Expert Consult title and on its fully searchable web site, you'll find detailed coverage of hamstring, allograft and bone-tendon-bone (BTB) ACL reconstruction (including single versus double bundle techniques), and hamstring graft harvesting; plus fixation devices, rehabilitation, revision ACLR surgery, and much more!
  • A "dream team" of ACL surgeons provides the advanced guidance you need to overcome the toughest challenges in this area.
  • A comparison of the full range of graft options for ACL reconstruction makes it easier to choose the best approach for each patient.
  • State-of-the-art information on the latest principles and technical considerations helps you avoid complications.
  • ‘How to' principles of post-op rehabilitation and revision ACL surgery optimize patient outcome.
  • Access to the full contents of the book online enables you to consult it from any computer and perform rapid searches.
  • Also available in an upgradeable premium online version including fully searchable text PLUS timely updates.

Sujets

Livres
Savoirs
Medecine
Médecine
Contusión
Surgical incision
Knee pain
Screw
Autologous chondrocyte implantation
Liver
Dissociated Vertical Deviation
Surgical suture
Surgical staple
Extension (kinesiology)
Anterior cruciate ligament injury
Bone density
Vitality
Tricalcium phosphate
Literature review
Arthropathy
Bone grafting
Polylactic acid
Chondromalacia patellae
Medical device
Acute pancreatitis
Allotransplantation
Orthopedics
Transmission (medicine)
Hypertrophy
Anterior cruciate ligament
Posterior cruciate ligament
Deep vein thrombosis
Sterility
Osteoarthritis
Stiffness
Orthopedic surgery
Device
Cannula
Soft tissue
Stripper
Myotomy
Software release life cycle
Pulmonary embolism
Physical exercise
Fixative
Complex regional pain syndrome
Infection
Volleyball
Physical therapy
Polymer
Osteoporosis
Mechanics
Magnetic resonance imaging
Growth factor
General surgery
Collagen
Band
Arthritis
Americium
Fractures
Japan
Proprioception
Proven
Lead
Mandrillus leucophaeus
Femur
Athlete
Force
Confidentialité
Hammer
Release
Gore-Tex
Flexion
Torque
Surface
Copyright
Sport

Informations

Publié par
Date de parution 27 décembre 2007
Nombre de lectures 1
EAN13 9781437721218
Langue English
Poids de l'ouvrage 27 Mo

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The Anterior Cruciate
Ligament
Reconstruction and Basic Science
Chadwick C. Prodromos, MD
President, Illinois Sports Medicine and Orthopaedic Centers
Assistant Professor, Orthopaedic Surgery Section of Sports Medicine, Rush University
Medical Center, Chicago, Illinois
S a u n d e r sTable of Contents
Cover image
Title page
Copyright
Dedication
About this Book
Acknowledgments
List of Contributors
Section I – Anterior Cruciate Ligament Injury
Part A: Anatomy, Physiology, Biomechanics, Epidemiology
Chapter 1: Anatomy and Biomechanics of the Anterior Cruciate Ligament
Introduction
Anterior Cruciate Ligament Anatomy
Biomechanics
Conclusion
Chapter 2: Mechanisms of Noncontact Anterior Cruciate Ligament Injuries
Chapter 3: Risk and Gender Factors for Noncontact Anterior Cruciate Ligament
Injury
Introduction
Environmental Risk FactorsAnatomical Risk Factors
Hormonal Risk Factors
Neuromuscular Risk Factors
Familial Tendency to Noncontact Anterior Cruciate Ligament Injury
Summary
Chapter 4: The Incidence of Anterior Cruciate Ligament Injury as a Function of
Gender, Sport, and Injury-Reduction Programs
Introduction
Purpose
Methods
Exposures
Data Conversions
Individual Sports
The Overall Risk of Anterior Cruciate Ligament Tear
Female–Male Injury Risk Ratio
Anterior Cruciate Ligament Tear-Prevention Programs
Implications for Future Anterior Cruciate Ligament Injury-Reduction Research
Conclusions
Chapter 5: Analysis of Anterior Cruciate Ligament Injury-Prevention Programs for
the Female Athlete
Introduction
Anterior cruciate ligament Injury-Prevention Studies
Areas for Further Research
Conclusion
Part B: Clinical
Chapter 6: Diagnosis of Anterior Cruciate Ligament Tear
Introduction
Diagnosis in the Acute Versus the Chronic Setting
Partial TearsHistory
Physical Exam
Conclusions
Chapter 7: Nonoperative Management of Anterior Cruciate Ligament Deficient
Patients
Anterior Cruciate Ligament Deficiency: The Need for Muscle Strengthening
Importance of the Hamstrings, Especially in Soccer Players: Our Research
Review of the Literature on the Role of the Quadriceps and Hamstrings in Anterior
cruciate ligament Deficient Knees
Bracing in anterior cruciate ligament Deficient Patients: Is It Effective?
Rehabilitation
Summary
Chapter 8: Arthrosis Following Anterior Cruciate Ligament Tear and Reconstruction
Introduction
Pathophysiology of Osteoarthritis Following Anterior Cruciate Ligament Injury
Natural History of the Untreated Anterior Cruciate Ligament Deficient Knee
Arthrosis Following Anterior Cruciate Ligament Reconstruction
Conclusion
Section II – Anterior Cruciate Ligament Reconstruction
Chapter 9: The Economics of Anterior Cruciate Ligament Reconstruction
Background
Purpose
Whose Costs are being Considered?
Sources of Cost Information
Third-Party Payer Payments
Institutional Fixed Costs
Conclusions
Part A: Graft Mechanical Properties
Chapter 10: The Relative Strengths of Anterior Cruciate Ligament Autografts andChapter 10: The Relative Strengths of Anterior Cruciate Ligament Autografts and
Allografts
Introduction
Methods
Comparison of Graft Strengths
Effect of Ligamentization
Allograft Strengths
Quadriceps Tendon Graft Strength
Relative Strength of Hamstring and Bone–patellar tendon–bone Grafts
Overall Relative Graft Strengths
Conclusions
Chapter 11: Why Synthetic Grafts Failed
History of Synthetic Grafts for Anterior Cruciate Ligament Reconstruction
Types of Synthetic Grafts
Causes of Failure of Synthetic Grafts
Other Problems with Synthetic Grafts
The Future
Part B: Autograft Harvest Techniques
Chapter 12: Hamstring Harvest Technique for Anterior Cruciate Ligament
Reconstruction
Abstract
Technique of Hamstring Graft Harvest
Skin Incision
Exposure of the Tendon
Tendon Release
Stripping of the Tendon
Preparation of the Graft
Tips for Harvesting the Hamstring Grafts to avoid complications
Chapter 13: Posterior Mini-Incision Hamstring Harvest Approach for AnteriorCruciate Ligament Reconstruction
Overview
Anatomy
Surgical Technique
Harvest Problems with the Traditional Approach and Solutions Using the Combined
Posterior/Anterior Mini-Incision Approach
Clinical Experience
Who Should Use this Technique?
Chapter 14: Technique for Harvesting a Mid-Third Patella Tendon Graft for Anterior
Cruciate Ligament Reconstruction
Introduction
Skin Incision
Exposure
Taking the Graft
Fashioning the Graft
Closure
Chapter 15: The Central Quadriceps Free Tendon for Anterior Cruciate Ligament
Reconstruction
Introduction
Technique
Troubleshooting Central Quadriceps Free Tendon Harvest
Fixation of the Central Quadriceps Free Tendon Graft
Part C: Hamstring Graft Configurations
Chapter 16: Hamstring Anterior Cruciate Ligament Reconstruction with a
Quadrupled or Tripled Semitendinosus Tendon Graft
Introduction
Scientific Rationale for a Quadrupled Construct
Surgical Technique
ConclusionChapter 17: 2ST/2Gr, 4ST, and 3ST/2Gr Techniques: Deciding Which Hamstring
Configuration to Use
Introduction
The Parameters for Choosing A Hamstring Graft Configuration
Graft Preparation Techniques
Troubleshooting
Five Strand Using 3ST/2Gr
Four-Strand St Graft Preparation Technique
Conclusions
Part D: Principles of Tunnel Formation
Single Femoral-Tunnel Formation
Chapter 18: Use of the Transtibial Technique to Avoid Posterior Cruciate Ligament
and Roof Impingement of an Anterior Cruciate Ligament Graft
Introduction
Definition, Complications, and Diagnosis of Posterior Cruciate Ligament
Impingement
Definition, Complications, and Diagnosis of Roof Impingement
The Tibial Tunnel: The Key Tunnel in the Transtibial Technique
Rationale for Widening the Notch to Prevent Posterior Cruciate Ligament
Impingement
Principle for Avoiding Posterior Cruciate Ligament and Roof Impingement
Surgical Technique for Avoiding Posterior Cruciate Ligament and Roof Impingement
and Replicating the Tension Pattern of the Intact Anterior Cruciate Ligament
Validation of Tibial Guide
Summary
Chapter 19: The Anteromedial Portal for Anterior Cruciate Ligament Reconstruction
Introduction
Advantages
Technique
Possible ComplicationsChapter 20: The Retrodrill Technique for Anterior Cruciate Ligament Reconstruction
Introduction
Femoral Tunnel Placement
Surgical Technique
Preliminary Results and Conclusions
Chapter 21: Femoral Tunnel Placement to Restore Normal Knee Laxity After Anterior
Cruciate Ligament Reconstruction
Introduction
Functional Anatomy of the Anterior Cruciate Ligament Related to Graft Tunnels
Anterior Cruciate Ligament Isometry and Reconstruction
Anatomical Single-Bundle Anterior Cruciate Ligament Reconstruction
Anatomical Double-Bundle Anterior Cruciate Ligament Reconstruction
Discussion
Double Anteromedial and Posterolateral Femoral-Tunnel Formation
Chapter 22: Anatomical Double-Bundle Anterior Cruciate Ligament Reconstruction
Procedure Using the Semitendinosus and Gracilis Tendons
Introduction
Procedure
Clinical Results
Chapter 23: Anatomical Anterior Cruciate Ligament Reconstruction with
DoubleBundle, Double-Stranded Hamstring Autografts: A Four-Tunnel Technique
Introduction
Surgical Procedure
Discussion
Conclusion
Chapter 24: Anatomical Double-Bundle Anterior Cruciate Ligament Reconstruction
with a Semitendinosus Hamstring Tendon Graft
Introduction
Anatomy of the Anterior Cruciate LigamentScientific Rationale
Surgical Technique
Preliminary Results
Other Applications
Special Considerations
TroubleShooting
Chapter 25: Anatomical Double-Bundle Reconstruction of the Anterior Cruciate
Ligament
Introduction
Preoperative Considerations
Surgical Technique
Postoperative Considerations
Conclusion
Notchplasty and Navigation
Chapter 26: Notchplasty
Anatomy
Indications and Potential Risks
Techniques and Avoiding Complications
Chapter 27: Computer-Assisted Navigation for Anterior Cruciate Ligament
Reconstruction
Rationale
Need for Precision in Tunnel Placement
Current Accuracy without Navigation
Techniques of Computer-Assisted Navigation
Results
Discussion
Part E: Fixation Biomechanics
Chapter 28: Biomechanics of Intratunnel Anterior Cruciate Ligament Graft FixationIntroduction
Limitations of Biomechanical Studies
Bone Mineral Density
Bone–Patellar Tendon–Bone Fixation
Guidelines and Recommendations for Intratunnel Fixation of Bone–Tendon–Bone
Grafts
Soft Tissue Grafts
Alternative Intratunnel Tibial Fixation Techniques
Future Directions
Chapter 29: High-Stiffness, Slippage-Resistant Cortical Fixation Has Many
Advantages over Intratunnel Fixation
Introduction
Fixation Stiffness and Slippage: Critical Factors in Restoring Anterior Laxity
Definition and Examples of High- and Low-Stiffness Fixation
Comment About Intratunnel Fixation with an Interference Screw
Example of Stiffness Principle
Biological and Mechanical Advantages of Cortical Fixation Over Intratunnel Fixation
Preferred Fixation Technique
Conclusion
Chapter 30: Tibial Fixation for Anterior Cruciate Ligament Hamstring Grafts: 10
Techniques that Improve Fixation
Introduction
Technique 1: Graft Preparation
Technique 2: Pretension and Cycling of the Grafts
Technique 3: Maximize Length of the Tibial Tunnel
Technique 4: Limited débridement of Articular Edge of Tibial Tunnel
Technique 5: Distal Tunnel Fixation
Technique 6: Bone Grafting of Tibial Tunnel
Technique 7: Rigid Interosseous Compression with Interference Screw
Technique 8: Cross-Pin Fixation of Interference Screw System
Technique 9: Utilization of Bioabsorbable MaterialsTechnique 10: Modified Physical Therapy for the First 2 Months After Surgery
Part F: Fixation Devices and Methods of Soft-Tissue Graft Femoral Fixation
Suspensory Cortical
Chapter 31: Endobutton Anterior Cruciate Ligament Reconstruction Femoral Fixation
Introduction
Biomechanics
Clinical Results
Surgical Technique
Troubleshooting
The Xtendobutton
Conclusions
Chapter 32: Cortical Screw Post Femoral Fixation Using Whipstitches, Fabric Loop, or
Endobutton: The Universal Salvage
Background
Biomechanics
Surgical Technique
The Femoral Post Technique Can Salvage the Following Situations
Conclusions
Chapter 33: EZLoc Femoral Fixation of a Soft Tissue Graft
Abstract
Introduction
Reliable Surgical Technique with Minimal Steps
EZLoc and the Skeletally Immature Patient
EZLoc and Drilling through the Femoral Cortex
Revision Surgery with the EZLoc
Troubleshooting the EZLoc
ConclusionCross-Pin
Chapter 34: Stratis ST Femoral Fixation System
Introduction
Design Rationale of the Stratis ST
Technique
Removal of Implant
Pearls and Pitfalls
Chapter 35: Pinn-ACL CrossPin System for Femoral Graft Fixation
Introduction
Instruments and Implant Design
Surgical Technique with Hamstring Tendons
Tips and Tricks
Troubleshooting
Video Technique
Chapter 36: TransFix Anterior Cruciate Ligament Femoral Fixation
Background
Biomechanical and Clinical Results
Surgical Technique
Troubleshooting and Common Problems
Conclusion
Chapter 37: Stryker Biosteon Cross-Pin Femoral Fixation for Soft-Tissue Anterior
Cruciate Ligament Reconstruction
Introduction
Why Hydroxyapatite?
Surgical Technique
Postoperative Care
Biomechanical Performance of Stryker Biosteon Cross-Pin
Results
ConclusionsChapter 38: Anterior Cruciate Ligament Reconstruction Utilizing the Rigidfix for
Femoral-Sided Fixation
Background
Surgical Technique
TroubleShooting
Postsurgical Care
Results
Interference Screw–Based
Chapter 39: Hamstring Tendon Interference Screw Fixation
Biomechanical and Biological Considerations
Technical Considerations
Chapter 40: Anatomical Retroscrew Anterior Cruciate Ligament Fixation: Single- and
Double-Bundle Anterior Cruciate Ligament Reconstruction with Retroscrew
Biointerference in a Single Femoral Socket
Operative Technique: Single Femoral Socket, Single-Bundle Graft
Operative Technique: Single Femoral Socket, Double-Bundle Graft
Part G: Soft-Tissue Graft Tibial Fixation
Cortical
Chapter 41: Fastlok Device for Tibial Fixation of a Tripled or Quadrupled
Semitendinosus Autograft for Anterior Cruciate Ligament Reconstruction
Introduction
Scientific Rationale
Surgical Technique
Results
Troubleshooting
Conclusions
Chapter 42: Whipstitch-Post Tibial Fixation for Anterior Cruciate Ligament
ReconstructionBiomechanics
Clinical Results
Surgical Technique
Troubleshooting
Conclusions
Chapter 43: WasherLoc and Bone Dowel Tibial Fixation of a Soft-Tissue Graft
Introduction
WasherLoc and Bone Dowel Surgical Technique
WasherLoc Resists Slippage Under Cyclical Load
Bone Dowel Limits Tunnel Widening at 1 to 2 Years
Conclusion
Chapter 44: Double-Spike Plate: Cortical Fixation Device Enabling Graft Fixation
Under Optional Tension
Background and Basic Concept
Specifications and Instruments for Use
Rationale for Maintaining the Tension During Graft Fixation to the Tibia
In Vitro Biomechanical Data Using Porcine Tibiae and Bovine Flexor Tendons
Easy, Secure, and Consistent Pullout Anterior Cruciate Ligament Graft Fixation with
Double-Spike Plates
Tension Achieved Immediately After Anterior Cruciate Ligament Reconstruction
Troubleshooting
Interference Screw–Based
Chapter 45: Anterior Cruciate Ligament Hamstring Graft Fixation with BioScrew
XtraLok Tibial Fixation Device
Introduction
Fixation of the Graft in the Tibial Tunnel
Results
XtraLok Tips and Troubleshooting
Chapter 46: Intratunnel Tibial Fixation of Soft-Tissue Anterior Cruciate LigamentGrafts: Graft Sleeve and Tapered Screw
Introduction
Basic Science
Surgical Technique
Postoperative Management
Use of the Graft Sleeve With Tibialis Tendon Allografts
Pearls and Pitfalls of the Technique
Results
Future of the Technique
Chapter 47: Hamstring Anterior Cruciate Ligament Reconstruction with IntraFix
Tibial Fastener
Introduction
Surgical Technique
Postoperative Management
Results
Conclusion
Part H: Bone–Patellar Tendon–Bone Fixation: Femur or Tibia
Chapter 48: Interference Screw Fixation in Bone–Patellar Tendon–Bone Anterior
Cruciate Ligament Reconstruction
Introduction
Graft Preparation
Screw Selection
Bone Tunnel Preparation
Relative Position of Screw and Graft within Tunnel
Parallelism and Divergence
Graft–Tunnel Mismatch
Extremes of Bone Density
Conclusion
Chapter 49: Anterior Cruciate Ligament Reconstruction Using a Mini-ArthrotomyTechnique with Either an Ipsilateral or a Contralateral Autogenous Patellar Tendon
Graft
Introduction
Preoperative planning
Technique
Comments
Chapter 50: Bone–Patellar Tendon–Bone Anterior Cruciate Ligament Reconstruction
Using the Endobutton Continuous Loop Bone–Tendon–Bone Fixation System
Technique Overview
Technique in Detail
Revision Anterior Cruciate Ligament Surgery
Troubleshooting
Results
Summary
Part I: Newer Interference Screw Materials
Chapter 51: Milagro (Beta-Tricalcium Phosphate, Polylactide Co-Glycolide
Biocomposite) Interference Screw for Anterior Cruciate Ligament Reconstruction
Introduction
Biomechanical and Biochemical Data
Basic Science of Beta-Tricalcium Phosphate copolymers
Clinical Information
Pearls
Chapter 52: Improving Biodegradable Interference Screw Properties by Combining
Polymers
Introduction
Biomechanical Results
Clinical Results
Conclusions
Part J: Graft TensioningChapter 53: Graft Tensioning in Anterior Cruciate Ligament Reconstruction
Introduction
In Vitro Biomechanical Studies on Graft Tensioning
In Vivo studies with Animal Anterior Cruciate Ligament Reconstruction Models
Randomized Clinical Trials on the Effect of Initial Graft Tension on the Outcome
after Anterior Cruciate Ligament Reconstruction
Chapter 54: Tensioning Anterior Cruciate Ligament Grafts
Introduction
Native Anterior Cruciate Ligament Tension
Basic Science and Graft Histology
Graft-Specific Tensioning
Stress Relaxation, Preconditioning, and Pretensioning
Knee Fixation Angle
Tensioning Devices and Strategies
Part K: Ligamentization and Graft-Tunnel Healing
Chapter 55: Graft Remodeling and Ligamentization After Anterior Cruciate Ligament
Reconstruction
Early Graft-Healing Phase
Proliferation Phase of Graft Healing
Ligamentization Phase of Graft Healing
Chapter 56: Graft-Tunnel Healing
Human Studies
Animal Studies
Future Directions
Conclusions
Part L: Revision Anterior Cruciate Ligament Reconstruction
Chapter 57: Revision Anterior Cruciate Ligament Reconstruction Using Autologous
Hamstring TendonsIntroduction
Failure Analysis
Hardware Management
Tunnel Management
Graft Selection and Fixation
Chapter 58: Revision Anterior Cruciate Ligament Reconstruction
Introduction
Causes Of Failure of Primary Procedure
Treatment Options
Definition of knee instability
Surgical procedure
Graft Choice: Autograft Versus Allograft
Graft Fixation: Cortical or Apertural
Postoperative rehabilitation
Our experience with a two-stage revision Anterior Cruciate Ligament reconstruction
Review of literature
Part M: Anterior Cruciate Ligament Reconstruction for Skeletally Immature
Patients or Partial Tears
Chapter 59: Anterior Cruciate Ligament Reconstruction in Skeletally Immature
Patients
Natural History
Assessing Skeletal Maturity
Normal Growth and Development
Basic Science Research on Physeal Injury
Risk Factors for Iatrogenic Growth Disturbance
Treatment Options
Treatment and Recommendations
Transepiphyseal Anterior Cruciate Ligament Reconstruction
Physeal-Sparing ACL Reconstruction with the Iliotibial Band
Transphyseal Anterior Cruciate Ligament ReconstructionChapter 60: Anterior Cruciate Ligament Reconstruction of Partial Tears:
Reconstructing One Bundle
Introduction
Preoperative Considerations
Surgical Technique
Rehabilitation
Complications
Results
Conclusion
Part N: Treatment of Associated Ligament Injuries or Cartilage Deficiency
Chapter 61: Anterior Cruciate Ligament Injury Combined with Medial Collateral
Ligament, Posterior Cruciate Ligament, and/or Lateral-Side Injury
Introduction
Ligament Healing
Clinical Examination
Associated Neurovascular Injury
Imaging
Treatment Philosophy (Principles)
Summary
Chapter 62: Treatment of Meniscus Tears with Anterior Cruciate Ligament
Reconstruction
Introduction
Meniscus Tears to Leave in Situ
Meniscus Tears to Repair
Conclusions
Chapter 63: Anterior Cruciate Ligament Reconstruction Combined with High-Tibial
Osteotomy, Autologous Chondrocyte Implantation, Microfracture, Osteochondral,
and/or Meniscal Allograft Transplantation
Introduction
IndividualizationSurgeon Factors
Success Rates
Patient Expectations
Restoration of Motion
Anterior Cruciate Ligament Reconstruction and Microfracture
Anterior Cruciate Ligament Reconstruction and Autologous Chondrocyte
Implantations
Anterior Cruciate Ligament Reconstruction and Meniscal Allograft Implantation
Anterior Cruciate Ligament Reconstruction and Osteochondral Allograft or
Osteochondral Autograft Transfer System
Anterior Cruciate Ligament Reconstruction and High-Tibial Osteotomy
Multiple Cartilage Restorative Procedures
Cartilage Preservation Versus Arthroplasty
Conclusions
Part O: Rehabilitation
Chapter 64: Anterior Cruciate Ligament Strain Behavior During Rehabilitation
Exercises
Description of the Devices, Methods, and Approaches Used to Measure Anterior
Cruciate Ligament Biomechanics in Vivo
Review of Studies That Have Characterized Anterior Cruciate Ligament Strain
Behavior During Rehabilitation Exercises
Review of Studies That Have Measured the Strain of the Bone–Patellar Tendon–
Bone Graft
Review of Studies Investigating how Functional Knee Bracing Affects Anterior
Cruciate Ligament Strain Behavior
Summary
Chapter 65: Principles of Anterior Cruciate Ligament Rehabilitation
Introduction
Preoperative Rehabilitation
Postoperative Rehabilitation
Comment
SummaryChapter 66: The Stability-Conservative Anterior Cruciate Ligament Reconstruction
Rehabilitation Protocol
Introduction
History
Symmetric Stability After Anterior Cruciate Ligament Reconstruction is Not Assured
Why Protect The Graft in The First 3 Months Postoperatively?
Muscular Inhibition After Anterior Cruciate Ligament Reconstruction
Cyclical Loading Does Cause Laxity
Why Avoid Hyperextension?
Why Insist on Full Extension and How to Achieve it
Why Avoid Full Flexion?
The Timing of Strengthening in Physical Therapy
Quadriceps Strengthening
Hamstring Strengthening
Adductor/Abductor Strengthening
The Gastrocnemius and Triceps Surae
Stairs
Lower Extremity Cyclical Loading
Gait Training
Proprioception
Hamstring Versus Bone–Patellar Tendon–bone
Allograft Rehabilitation
Home Versus Clinic Therapy
Equipment
Strength Testing
Results
Summary of Protocol
Chapter 67: Hamstring Regeneration Following Harvest for Anterior Cruciate
Ligament Reconstruction: A Review of the Current Literature
Radiographic Studies
Functional StudiesHistological Studies
Animal Models
Future Directions
Conclusions
Chapter 68: Proprioception and Anterior Cruciate Ligament Reconstruction
Part P: Stability Results
Chapter 69: Stability Results After Anterior Cruciate Ligament Reconstruction
Study Criteria
Statistical Methods
Results
Conclusions
Part Q: Complications
Chapter 70: Infections in Anterior Cruciate Ligament Surgery
Introduction
Prevalence of Infection
Pathogenesis: Predisposing Factors
Diagnosis
Management Protocol
Allografts and Infections in Anterior Cruciate Ligament Surgery
Intraoperative Graft Contamination
Chapter 71: Allograft Complications and Risk Factors
Introduction
Areas of Morbidity
Potential Causes of Increased Laxity
Potential Causes of Infection and Disease Transmission
Conclusions
Chapter 72: Stiffness: Prevention and TreatmentEtiology
Treatment
Conclusions
Chapter 73: Osteoporosis After Anterior Cruciate Ligament Reconstruction?
Anterior Cruciate Ligament Injuries and their Treatment
Peak Bone Mass and Natural Bone Losses
Osteoporosis
Bone Loss and Musculoskeletal Injuries
Anterior Cruciate Ligament Surgery and the Effect on Bone Tissue
Surgery: A Risk Factor for Osteoporosis?
Chapter 74: Tunnel Widening After Anterior Cruciate Ligament Reconstruction
Introduction
Methods of Analyzing Tunnel Widening
Specific Factors Associated With Increased Tunnel Widening
Adverse Effects
Conclusions
Chapter 75: Numbness/Saphenous Nerve
Introduction
Bone–Tendon–Bone Autograft
Hamstring Autograft
Clinical Examination
Anatomical Investigations
Discussion
Chapter 76: Hardware Complications After Anterior Cruciate Ligament
Reconstruction
Introduction
Interference Screws
Endobutton
Cross-Pin FixationTibia Fixation
Skeletally Immature Patients
Conclusion
Chapter 77: Vascular Complications After Anterior Cruciate Ligament Reconstruction
Arterial Complications
Venous Complications
Chapter 78: Fracture Complications After Anterior Cruciate Ligament Reconstruction
Femur Fracture
Patella Fracture
Tibia Fracture
Chapter 79: Anterior Knee Problems After Anterior Cruciate Ligament
Reconstruction
Introduction
Anterior Knee Problems Related To the Graft
Anterior Knee Problems Related to the Procedure
Anterior Knee Problems Related to Rehabilitation
How to Reduce Anterior Knee Symptoms After Anterior Cruciate Ligament
Reconstruction
Part R: Gait Analysis and Tissue Engineering
Chapter 80: Gait Analysis in Anterior Cruciate Ligament Deficient and Reconstructed
Knees
Introduction
Importance of in Vivo Biomechanical Research to Quantify Success of Surgical
Techniques
Advanced Theoretical Considerations
Recommendations for Future Work: How Gait Analysis can Guide the Development
of Surgical Techniques
Summary
Chapter 81: Growth Factors and Other New Methods for Graft-Healing EnhancementBasic Knowledge to Enhance the Graft Remodeling in Anterior Cruciate Ligament
Reconstruction
Enhancement of Graft Healing with Growth Factors
Enhancement of Graft Healing with Gene Therapy
Enhancement of Graft Healing with Cell-Based Therapy
Summary
IndexCopyright
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THE ANTERIOR CRUCIATE LIGAMENT: Basic Edition: 978-1-4160-3834-4
RECONSTRUCTION AND BASIC SCIENCE Premium Edition: 978-1-4160-5332-3
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The anterior cruciate ligament : reconstruction and basic science / [edited by]Chadwick C. Prodromos.—1st ed.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-1-4160-3834-4
1. Anterior cruciate ligament—Surgery. I. Prodromos, Chadwick C.
[DNLM: 1. Anterior Cruciate Ligament—surgery. 2. Anterior Cruciate Ligament—
injuries. 3. Orthopedic Procedures—methods. 4. Reconstructive Surgical Procedures
—methods. 5. Tissue Transplantation—methods. WE 870 A6275 2008]
RD561.A593 2008
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This book is dedicated to my family: first and foremost to my mother, who inspired
me to enter medicine and taught me the paramount importance of family through her
dedication to hers; then to my wife, Marilyn, and my two daughters, Lexy and
Stephany. The only negative part of editing and writing this book was taking precious
time away from them. Finally, to my sister, Althea, who has supported me in all my
endeavors.


About this Book
Why this Book Is Needed
The anterior cruciate ligament (A CL) is one of the most wri en about topics in
Orthopaedics, such that it has become very difficult for most Orthopaedists to stay
current through regular casual reading of the literature. Yet until now there has not
been a comprehensive A CL text. This book fills that gap. We have a empted to
present the essence of the world’s accumulated clinically relevant A CL-related
knowledge in 81 concise chapters.
About the Associate Editors and Contributors
The associate editors listed on the cover and the other contributors are a “dream
team” of leading A CL surgeons and scientists from around the world who were
chosen based on their accomplishments and research on the specific topic of their
chapter. Other distinguished surgeons are being continually added as special
contributors of new “hot topics” for the ACL website.
Fixation Devices and Troubleshooting
Each of the leading A CL reconstruction fixation devices has its own chapter wri en
by its creator or one of its most skilled users. Each such chapter presents scientific
rationale, technique, results, and, most importantly, a troubleshooting section. Every
surgeon encounters technical problems during cases, but we know of no other source
for the practicing surgeon to find the best way to get out of them. Most device
information comes to surgeons from company representatives who do provide a
useful service; but the chapters in this text, along with the many videos, provide a
more in-depth alternative. Through partnership with the leading sports medicine
companies, new devices will be introduced on the website along with expert
orthopaedic evaluations—“peer reviewed marketing.”
The Technique of ACL Reconstruction
The best techniques for each component of A CL reconstruction: harvest, fixation,
tunnels, notchplasty, and so forth, are collected and presented. This information leads
directly to good outcomes.
Choices
After technique, ACL surgery is all about choices: interference versus cortical fixation,
bone–patella tendon–bone versus hamstring, auto versus allograft, accelerated versus
protected rehab, anterior versus posterior hamstring harvest, metal versus bio versus
osteoconductive, single versus double bundle, and so on. I nformation on both sides
of each argument is presented to allow the surgeon to make each choice a well-

informed one.
Related Topics
The expert treatment of related pathology—cartilage and ligamentous—is essential
for the A CL surgeon, and is presented here. There are also 10 chapters on different
types of complications, much of it probably unfamiliar to many. There is original
research on the incidence of A CL tears, economics, and stability results. N ew
horizons, including four double bundle techniques, navigation, and tissue
engineering are also presented, along with biomechanical information and much
more.
The DVD
D ozens of surgical technique videos of the component techniques that make up A CL
reconstruction, and a few additional topics, comprise the included D VD . S ome videos
were created especially for this D VD , others represent classics from the A A OS and
elsewhere. A ll are the best we know of on the given topic and form the only such
large collection of ACL videos.
The Website
The dedicated website includes an e edition of the book. At this writing there are 10
additional chapters not included in the print version on new “hot topics,” such as
quadriceps tendon A CL reconstruction results, and more will be added as new
advances or controversies emerge. There are also product introductions in
partnership with industry, useful links, course offerings, and much more. The website
also includes the “Ask the Experts” and “ACL Database” features described below.
Ask the Experts
The contributors to this book have all agreed to field questions from Orthopaedic
S urgeons with website passwords on their particular topics, or others. These e-mailed
queries are directed to a central question center, distributed to the appropriate
surgeon, and then answered confidentially to the surgeon who posed the question.
The idea is to assist surgeons everywhere to be er treat their patients by ge ing help
from the best when they need it.
Staying Current: The ACL Database
The book’s short gestation period has ensured that each chapter is up-to-date at
publication. However, through the book’s website, significant new A CL-related
knowledge is being added each quarter to keep it that way. This is how it works:
Beginning in J anuary 2007, every month the 50 or so new A CL-related article
references published in the world’s peer reviewed literature have been appended to
the bibliography for the most relevant chapter(s) or sections of the text to which they
relate. Presentations and even posters from the major sports medicine meetings are
similarly categorized each month. Thus, the A CL database presents a continually
updated compendium of essentially all the world’s new A CL-related knowledge as it
is being created, organized by topic. This is an ideal research tool for any A CL-related
topic about which you need to know.A c k n o w l e d g m e n t s
The special contributors listed on the cover of the book have been involved in this
project from the beginning and have supported its development with their time and
energy simply because they believed in the worthwhile nature of the project. There
are none brighter or more dedicated. I am grateful to them and to all the other
esteemed contributing authors: the “dream team” of A CL scientists and surgeons
described on the preceding page. I was confident that they would produce the
outstanding works of scholarship that they have, but I was continually surprised at
how easy to work with these illustrious scientists and surgeons all were and how they
respected the time deadlines and constraints of space and organizational structure of
the project. This clearly comes from being passionate about their ideas and their work
and is reflected in the high quality of the chapters. I would also like to especially
thank one of those contributors, Bert Zarins, for all he taught me about both sports
medicine and life as my fellowship mentor many years ago.
Kim Murphy and all of the people at Elsevier have been a great pleasure to deal
with. S he showed enthusiasm and creativity for the project from the beginning and
continues to do so. They have also worked diligently to help avoid delays so that the
book will be up to date at its publication.
Finally, the staff at our clinic and my family have all been wonderful about the time
diverted from them to this book.List of Contributors
Keiichi Akita, MD, PhD, U nit of Clinical Anatomy, Graduate School, Tokyo Medical and
Dental University, Tokyo, Japan
Arturo Almazan, MD
Orthopedic Sports Medicine and Arthroscopy Department, National Institute of
Rehabilitation
Associate Professor, Sports Medicine Residency Program, National Autonomous University
of Mexico, Mexico City, Mexico
Andrew A. Amis, PhD , D Sc(Eng), FIMech, E Professor, D epartments of Mechanical
Engineering and Musculoskeletal Surgery, Imperial College London, London, England
Allen F. Anderson, MD , D irector, Lipscomb Clinic Research and Education Foundation,
Tennessee Orthopedic Alliance, Nashville, Tennessee
Christian N . Anderson, MD , Resident, D epartment of O rthopaedic Surgery, Vanderbilt
University Medical Center, Nashville, Tennessee
John C. Anderson, MD
Pacific Orthopaedics and Sports Medicine
Medical Staff, Portland Adventist Medical Center Portland, Oregon
F. Alan Barber, MD , FAC,S Fellowship D irector, Plano O rthopedic and Sports Medicine
Center, Plano, Texas
G ene R. Barre( , MD , Codirector of Knee Service, Mississippi Sports Medicine and
Orthopaedic Center, Jackson, Mississippi
Guy Bellier, MD, Cabinet Goethe, Institut de l'Appareil Locomoteur Nollet, Paris, France
Manfred Bernard, MD, Priv.-Doz., Klinik Sanssouci, Berlin, Germany
Bruce D . Beynnon, PhD , Associate Professor, McClure Musculoskeletal Research Center,
D epartment of O rthopaedics and Rehabilitation, College of Medicine, U niversity of Vermont,
Burlington, Vermont
Robert H . Brophy, MD , Fellow, Shoulder/Sports Medicine, H ospital for Special Surgery,
New York, New York
Charles H. Brown, Jr., MD, Medical D irector, Abu D habi Knee and Sports Injury Centre,
Abu Dhabi, United Arab Emirates
Taylor D. Brown, MD, Bone and Joint Center of Houston, Houston, Texas
Anthony Buoncristiani, MD , Fellow, D epartment of O rthopaedic Surgery, U niversity of
Pittsburgh Medical Center, Pittsburgh, Pennsylvania
D avid Caborn, MD , D epartment of O rthopaedic Surgery, U niversity of Louisville,
Louisville, Kentucky
Guglielmo Cerullo, MD, Clinica Valle Giulia, Roma, Italy=
=
N eal C. Chen, MD , Clinical Fellow, Sports Medicine and Shoulder Service, H ospital for
Special Surgery, New York, New York
Pascal Christel, MD , PhD, Professor of O rthopaedic Surgery, Institut de l'Appareil
Locomoteur Nollet, Paris, France
Vassilis Chouliaras, MD, O rthopaedic Sports Medicine Center, D epartment of
Orthopaedic Surgery, University of Ioannina, Ioannina, Greece
Massimo Cipolla, MD, Clinica Valle Giulia, Roma, Italy
Philippe Colombet, MD, Clinique du Sport de Bordeaux, Mérignac, France
N ader D arwich, MD , D eputy Medical D irector, Abu D habi Knee and Sports Injury
Centre, Abu Dhabi, United Arab Emirates
Laura Deriu, MD, Department of Orthopaedics, Catholic University, Rome, Italy
Patrick D jian, MD, Cabinet Goethe, Institut de l'Appareil Locomoteur N ollet, Paris,
France
Apostolos P. D imitroulias, MD , O rthopaedic Surgeon, U niversity H ospital of Larissa,
Larissa, Greece
Lars Ejerhed, MD , PhD, D epartment of O rthopaedics, N orthern Älvsborg County
Hospital, Uddevalla Hospital, Trollhättan Uddevalla, Sweden
Carlo Fabbriciani, MD , Professor and Chairman of O rthopaedics and Traumatology,
Department of Orthopaedics, Catholic University, Rome, Italy
Julian A. Feller, FRACS
Associate Professor, Musculoskeletal Research Centre, La Trobe University
Orthopaedic Surgeon, La Trobe University Medical Centre, Melbourne, Victoria, Australia
Mario Ferre( i, MD, Research Fellow, D epartment of O rthopaedic Surgery, U niversity of
Pittsburgh Medical Center, Pittsburgh, Pennsylvania
Jean Pierre Franceschi, MD, Hôpital de la Conception, Marseille, France
Ramces Francisco, MD , O rthopaedic Surgeon/Affiliate, O rthopaedic Arthroscopic
Surgery International, Clinica Zucchi, Milan, Italy
Vittorio Franco, MD, Clinica Valle Giulia, Roma, Italy
Stuart E. Fromm, MD , Black H ills O rthopaedic and Spine Center, Rapid City, South
Dakota
Freddie H . Fu, MD , D Sc (H on), D Ps (H o,n ) D avid Silver Professor and Chairman,
D epartment of O rthopaedic Surgery, U niversity of Pi sburgh Medical Center, Pi sburgh,
Pennsylvania
John P. Fulkerson, MD
Orthopedic Associates of Hartford, P.C.
Clinical Professor and Sports Medicine Fellowship Director, Department of Orthopedic
Surgery, University of Connecticut, Farmington, Connecticut
William E. G arre( , Jr., MD , PhD, D uke Sports Medicine Center, D urham, N orth
Carolina
Anastasios Georgoulis, MD
Professor of Orthopaedic Surgery
Chief, Orthopaedic Sports Medicine Center, Department of Orthopaedic Surgery, University
of Ioannina, Ioannina, GreeceG eorge G iakas, BSc, PhD, D epartment of Sports Science, U niversity of Thessaly, Karyes,
Trikala, Greece
Enrico Giannì, MD, Clinica Valle Giulia, Roma, Italy
Thomas J. G ill, MD , Assistant Professor, D epartment of O rthopedic Surgery, H arvard
Medical School, Boston, Massachusetts
Alberto G obbi, MD , D irector, O rthopaedic Arthroscopic Surgery International, Clinica
Zucchi, Milan, Italy
Steven Gorin, DO, Institute of Sports Medicine and Orthopaedics, P.A. Aventura, Florida
Tinker G ray, MA, EL,S Research D irector, Shelbourne Knee Center at Methodist
Hospital, Indianapolis, Indiana
Letha Y. Griffin, MD, PhD, Peachtree Orthopaedic Clinic, Atlanta, Georgia
David R. Guelich, MD, Chicago Orthopaedics and Sports Medicine, Chicago, Illinois
Yung H an, MD , Resident, McGill U niversity O rthopaedic Surgery Residency Program,
Montreal, Canada
Michael E. Hantes, MD, Consultant O rthopaedic Surgeon, U niversity H ospital of Larisa,
Larisa, Greece
Aaron H ecker, MA , Bioskills Laboratory Manager, Smith and N ephew, Mansfield,
Massachusetts
Stephen M. Howell, MD
Professor, Department of Mechanical Engineering
Member of Biomedical Graduate Group, University of California at Davis, Sacramento,
California
Mark R. H utchinson, MD , Professor of O rthopaedics and Sports Medicine, U niversity of
Illinois at Chicago, Chicago, Illinois
R.P.A. Janssen, MD, O rthopaedic Surgeon, D epartment of O rthopaedic Surgery and
Traumatology, Máxima Medical Center, Veldhoven, Netherlands
Timo Järvelä, MD, PhD
Department of Orthopaedics and Traumatology, Tampere City Hospital
Tampere University, Tampere, Finland
Department of Orthopaedics Surgery, University of Pittsburgh Medical Center, Pittsburgh,
Pennsylvania
Markku Järvinen, MD , PhD, Tampere U niversity; D epartment of Trauma,
Musculoskeletal Surgery, and Rehabilitation, Tampere U niversity H ospital, Tampere,
Finland
D on Johnson, MD , FRC,S D irector, Sports Medicine Clinic, Carleton U niversity,
Ottawa, Ontario, Canada
Brian T. Joyce, BA, Research Coordinator, Illinois Sports Medicine and O rthopaedic
Centers, Glenview, Illinois
Auvo Kaikkonen, MD, PhD, Inion Oy; Tampere University, Tampere, Finland
Anastassios Karistinos, MD , Assistant Professor, D epartment of O rthopaedic Surgery,
Baylor College of Medicine, Houston, Texas
Jüri Kartus, MD , PhD, D epartment of O rthopaedics, N orra Älvsborg/U ddevalla
Hospital, Trollhättan, SwedenJohn F. Keating, BA, MB, BCh, BAO, MPhil, FRCSI, FRC, S E Cdonsultant O rthopaedic
Surgeon, D epartment of Trauma and O rthopaedics, Royal Infirmary of Edinburgh,
Edinburgh, United Kingdom
James Kercher, MD, Emory School of Medicine, Emory University, Atlanta, Georgia
Petteri Kousa, MD, PhD
Department of Orthopaedics; Department of Surgery, University of Tampere, Tampere
University Hospital, Tampere, Finland
Department of Orthopaedics and Rehabilitation, McClure Musculoskeletal Research Center
Department of Orthopaedics and Rehabilitation, College of Medicine, University of Vermont,
Burlington, Vermont
Jason Koh, MD, Northwestern Medical Faculty Foundation, Chicago, Illinois
Michael Kuhn, MD
Clinical Instructor, Surgery, Uniformed Services University, Bethesda, Maryland
Fellow, Department of Orthopaedic Surgery and Sports Medicine, New England Baptist
Hospital, Boston, Massachusetts
Bert R. Mandelbaum, MD , Santa Monica and O rthopaedic and Sports Medicine
Foundation, Santa Monica, California
Robert G. Marx, MD, MSc, FRCSC
Associate Professor of Orthopedic Surgery and Public Health, Weill Medical College of
Cornell University
Attending Orthopedic Surgeon
Director, Foster Center for Clinical Outcome Research, Hospital for Special Surgery, New
York, New York
Brian P. McKeon, MD
Assistant Clinical Professor of Orthopedics, Tufts University
Head Team Physician, Boston Celtics, Boston Sports and Shoulder Center, Chestnut Hill,
Massachusetts
G iuseppe Milano, MD , Associate Professor, D epartment of O rthopedics, Catholic
University, Rome, Italy
Mark D. Miller, MD
Professor, Department of Orthopaedic Surgery, Director of Sports Medicine, University of
Virginia
Team Physician, James Madison University, Charlottesville, Virginia
Kai Mithoefer, MD
Clinical Instructor in Orthopedic Surgery, Harvard Medical School
Harvard Vanguard Orthopedics and Sports Medicine, Brigham and Women’s Hospital,
Boston, Massachusetts
Tomoyuki Mochizuki, MD , PhD, Section of O rthopedic Surgery, D ivision of Cartilege
Regeneration, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
Anna-Stina Moisala, MD, Tampere University, Tampere, Finland
Craig D. Morgan, MD, The Morgan-Kalman Clinic, Wilmington, Delaware
Constantina Moraiti, MD , D epartment of O rthopaedic Surgery, O rthopaedic Sports
Medicine Center of Ioannina, University of Ioannina, Ioannina, Greece
Takeshi Muneta, MD , PhD , Section of O rthopedic Surgery, D ivision of Cartilege
Regeneration, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan:
Brian J. Murphy, MD, Freeworld Imaging, Miami, Florida
Janne T. N urmi, D VM, PhD, Inion O y; Faculty of Veterinary Medicine, D epartment of
Clinical Veterinary Sciences, University of Helsinki, Tampere, Finland
N icholas E. Ohly, MBBS, MRCSE, d Specialist Registrar, D epartment of Trauma and
Orthopaedics, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom
An( i Paakkala, MD , PhD , D epartment of Radiology, Tampere U niversity H ospital,
Tampere, Finland
Lonnie E. Paulos, MD
Professor, Orthopedic Surgery, Baylor College of Medicine
Codirector, The Roger Clemens Institute for Sports Medicine and Human Performance,
Houston, Texas
H ans H . Paessler, MD , ATO S Clinic, Center of Knee Surgery, Foot Surgery and Sports
Trauma, Heidelberg, Germany
H emant G . Pandit, FRCS (Orth, ) N orth H ampshire H ospital, N uffield O rthopaedic
Centre, Oxford, United Kingdom
Michael J. Pa akis, MD, Professor and Chairman, D epartment of O rthopaedic Surgery,
Keck School of Medicine, U niversity of Southern California;LAC+U SC Medical Center, Los
Angeles, California
Chadwick C. Prodromos, MD
President, Illinois Sports Medicine and Orthopaedic Centers
Assistant Professor, Orthopaedic Surgery, Section of Sports Medicine, Rush University
Medical Center, Chicago, Illinois
Giancarlo Puddu, MD, Clinica Valle Giulia, Roma, Italy
Paul Re, MD, D irector, Sports Medicine Emerson H ospital O rthopaedic Affiliates,
Concord, Massachusetts
John Richmond, MD , Chairman, D epartment of O rthopaedics, N ew England Baptist
Hospital, Boston, Massachusetts
Andrew Riff, BS, Medical Student, Georgetown U niversity School of Medicine,
Washington, DC
Stavros Ristanis, MD , PhD, O rthopaedic Sports Medicine Center, D epartment of
Orthopaedic Surgery, University of Ioannina, Ioannina, Greece
James Robinson, MD , Imperial College of Science, Technology and Medicine, London,
United Kingdom
Julie Rogowski, BS, Professional Education Coordinator, Illinois Sports Medicine and
Orthopaedic Centers, Glenview, Illinois
Abdou Sbihi, MD, Hôpital de la Conception, Marseille, France
Sven U lrich Scheffler, MD , Sports Medicine and Arthroscopy Service, D epartment of
O rthopaedics and Traumatology, Center for Musculoskeletal Surgery, Charité, Campus
Mitte, University Medicine Berlin, Berlin, Germany
K. Donald Shelbourne, MD
Shelbourne Knee Center at Methodist Hospital
Associate Professor, Department of Orthopaedics, Indiana University School of Medicine,
Indianapolis, Indiana
Kelvin Shi, MS, Statistician, Forest Labs, Inc., New York, New York=
Konsei Shino, MD , PhD, Faculty of Comprehensive Rehabilitation, O saka Prefecture
University, Osaka, Japan
H olly J. Silvers, MPT, D irector of Research, Santa Monica O rthopaedic and Sports
Medicine Research Foundation, Santa Monica, California
Joseph H. Sklar, MD
Assistant Clinical Professor, Tufts University School of Medicine
New England Orthopaedic Surgeons, Springfield, Massachusetts
James R. Slauterbeck, MD , Associate Professor, McClure Musculoskeletal Research
Center, D epartment of O rthopaedics and Rehabilitation, College of Medicine, U niversity of
Vermont, Burlington, Vermont
James S. Starman, MD, Research Fellow, Department of Orthopaedic Surgery, University
of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
N icholas Stergiou, PhD , H PER Biomechanics Laboratory, U niversity of N ebraska at
Omaha, Omaha, Nebraska
Neil P. Thomas, BSC, MB, BS, FRCS
North Hampshire Hospital, Basingstoke, United Kingdom
Hampshire Clinic, Wessex Knee Unit, Hampshire, United Kingdom
Fotios Paul Tjoumakaris, MD , A ending Physician, D epartment of O rthopaedics, Cape
Regional Medical Center, Cape May Court House, New Jersey
H arukazu Tohyama, MD , PhD, Associate Professor, D epartment of Sports Medicine,
Hokkaido University School of Medicine, Sapporo, Japan
Elias Tsepis, BSc, PT, MSc, PhD, Associate Professor, Physical Therapy, Supreme
Technological Institution of Patra at Aigio, Patra, Greece
Frank N orman U nterhauser, MD , Center for Musculoskeletal Surgery, Clinic for
Trauma and Reconstructive Surgery, Charité, Campus Mitte, Berlin, Germany
G eorge Vagenas, BSc, PhD , N ational and Kapodistrian U niversity of Athens, Faculty of
Physical Education and Sport Science, Illioupolis, Attiki, Greece
Michael Wagner, MD, Sports Traumatology and Arthroscopy Service, Center for
Musculoskeletal Surgery, Berlin, Germany
Tony Wanich, MD, O rthopaedic Resident, D epartment of O rthopaedic Surgery, H ospital
for Special Surgery, New York, New York
Russell F. Warren, MD
Professor of Orthopaedics, Weill Medical College of Cornell University
Surgeon-in-Chief, Hospital for Special Surgery, New York, New York
Kate E. Webster, PhD , Research Fellow, Musculoskeletal Research Centre, La Trobe
University, Melbourne, Victoria, Australia
Andreas Weiler, MD , PhD, H ead of Sports Traumatology and Arthroscopy Service,
Center for Musculoskeletal Surgery, Berlin, Germany
Kazunori Yasuda, MD , PhD , Professor and Chairman, D epartment of Sports Medicine
and Joint Surgery, Hokkaido University School of Medicine, Sapporo, Japan
Bing Yu, PhD , Associate Professor, D ivision of Physical Therapy, D epartment of Allied
H ealth Sciences, The U niversity of N orth Carolina at Chapel H ill, Chapel H ill, N orth
Carolina
Charalampos G. Zalavras, MD=
Associate Professor, Department of Orthopaedic Surgery, Keck School of Medicine,
University of Southern California
LAC+USC Medical Center, Los Angeles, California
Bertram Zarins, MD , Augustus Thorndike Clinical Professor of O rthopaedic Surgery,
H arvard Medical School;Chief, Sports Medicine Service, Massachuse s General H ospital,
Boston, MassachusettsS E C T I ON I – A NT E RI OR C RUC I AT E
L I G A M E NT I NJ URY
OUT L INE
Chapter 1: Anatomy and Biomechanics of the Anterior Cruciate Ligament
Chapter 2: Mechanisms of Noncontact Anterior Cruciate Ligament Injuries
Chapter 3: Risk and Gender Factors for Noncontact Anterior Cruciate Ligament
Injury
Chapter 4: The Incidence of Anterior Cruciate Ligament Injury as a Function of
Gender, Sport, and Injury-Reduction Programs
Chapter 5: Analysis of Anterior Cruciate Ligament Injury-Prevention Programs for
the Female Athlete
Chapter 6: Diagnosis of Anterior Cruciate Ligament Tear
Chapter 7: Nonoperative Management of Anterior Cruciate Ligament Deficient
Patients
Chapter 8: Arthrosis Following Anterior Cruciate Ligament Tear and
ReconstructionPA RT A
Anatomy, Physiology,
Biomechanics,
Epidemiology
OUT L INE
Chapter 1: Anatomy and Biomechanics of the Anterior Cruciate Ligament
Chapter 2: Mechanisms of Noncontact Anterior Cruciate Ligament Injuries
Chapter 3: Risk and Gender Factors for Noncontact Anterior Cruciate Ligament
Injury
Chapter 4: The Incidence of Anterior Cruciate Ligament Injury as a Function of
Gender, Sport, and Injury-Reduction Programs
Chapter 5: Analysis of Anterior Cruciate Ligament Injury-Prevention Programs for
the Female AthleteC H A P T E R 1
Anatomy and Biomechanics of the
Anterior Cruciate Ligament
James S. Starman, Mario Ferretti, Timo Järvelä, Anthony Buoncristiani and Freddie H. Fu
Introduction
A nterior cruciate ligament (A CL) reconstruction is the sixth most common procedure performed
in orthopaedics, and it is estimated that between 75,000 and 100,000 A CL repair procedures are
1,2performed annually in the United S tates alone. The A CL has therefore been intensively
studied, and outcomes of A CL surgery have received considerable a- ention. This has included
research on surgical technique factors such as tunnel position, graft choices, and fixation
methods, as well as postoperative rehabilitation protocols.
Traditional single-bundle A CL reconstruction has focused on reconstruction of one portion of
the A CL, the anteromedial (A M) bundle, and although outcomes are generally good, with success
3,4rates between 69% and 95%, there remains room for improvement. A prospective study of a
cohort of A CL reconstructed patients 7 years after surgery revealed degenerative radiographic
changes in 95% of patients, and only 47% were able to return to their previous activity level
5following A CL reconstruction. However, it should be noted that some studies of long-term
follow-up have more encouraging results. J arvela et al demonstrated tibiofemoral degenerative
changes in only 18% of patients at 7 years follow-up post A CL reconstruction with bone–patella–
6bone grafts. I n addition, Roe et al reported on a cohort of patients reconstructed with bone–
patellar tendon–bone grafts and found an incidence of 45% with degenerative radiographic
changes at 7 years follow-up, as well as an incidence of 14% with degenerative changes in a group
7with hamstring grafts.
A thorough review of the anatomy and biomechanics of the normal A CL reveals key points
regarding its complex role in stabilization of the knee joint. I mproved awareness of the anatomy
and biomechanical properties of the normal A CL may lead to improvements in techniques for
A CL reconstruction and an associated improvement in outcomes over traditional results. This
chapter describes the normal anatomy of the two bundles of the A CL and reviews the
biomechanical contributions of each bundle.
Anterior Cruciate Ligament Anatomy
Historical Descriptions
One of the earliest known descriptions of the human A CL was made around 3000b c, wri- en on
an Egyptian papyrus scroll. D uring the Roman era, the earliest description of the ligament using
its modern name was made by Claudius Galen of Pergamon (199–129 bc), who described the
“ligamenta genu cruciate.” I n 1543 the first known formal anatomical study of the human A CL
was completed by Andreas Vesalius in his book De Humani Corporis Fabrica Libris Septum.
Two bundles of the A CL were described for the first time in 1938 by Palmer et al, followed by
8–10A bbo- et al in 1944 and Girgis et al in 1975. Each author described an A M bundle and a
posterolateral (PL) bundle, named for the relative location of the tibial insertion sites of each
bundle. More recently, in 1979 and again in 1991, N orwood et al and A mis et al, respectively,
11,12described a third bundle of the A CL anatomy, the intermediate (I M) bundle. A lthough it
may be said that a two-bundle description of the A CL anatomy is an oversimplification of thecomplete anatomy, many studies have been based on this functional division, and it has been
accepted as a reasonable way to understand the anatomy and biomechanics of the ligament. The
I M bundle is most similar to the A M bundle in both anatomical and biomechanical
considerations, and for the purposes of this chapter it is therefore considered as part of the A M
bundle.
Anatomy of the Anteromedial and Posterolateral Bundles
The A CL is a structure composed of numerous fascicles of dense connective tissue that connect
the distal femur and the proximal tibia. Histological studies have demonstrated that a septum of
vascularized connective tissue is present that separates the A M and PL bundles (Fig. 1-1). I n
addition, it has been shown that the histological properties of the ligament are variable at
different stages in A CL development. At the time of fetal A CL development, the A CL is observed
to be hypercellular with circular, oval, and fusiform-shaped cells. Later, in the adult A CL, the
histology reveals a relatively hypocellular pa- ern with predominantly fibroblast cells with
13,14spindle-shaped nuclei.
FIG. 1-1 Fetal anterior cruciate ligament, sagittal cut. Arrows indicate the
septum of vascularized connective tissue dividing the anteromedial (AM) and
posterolateral (PL) bundles.
The ligament finds its origin on the medial surface of the lateral femoral condyle (LFC), runs an
oblique course within the knee joint from lateral and posterior to medial and anterior, and inserts
into a broad area of the central tibial plateau. The cross-sectional area of the ligament varies
2significantly throughout its course from approximately 44 mm at the midsubstance to more than
10,15,16three times as much at both its origin and insertion. The total length of the ligament is
17approximately 31 to 38 mm and varies by as much as 10% throughout a normal range of motion.
Anterior Cruciate Ligament Development
A CL formation has been observed in fetal development as early as 8 weeks, corresponding to
18,19O’Rahilly stages 20 and 21. A leading hypothesis holds that the A CL originates as a ventral
condensation of the fetal blastoma and gradually migrates posteriorly with the formation of the
20intercondylar space. The menisci are derived from the same blastoma condensation as the A CL,21a finding that is consistent with the hypothesis that these structures function in concert.
A nother proposed mechanism of fetal A CL formation is from a confluence between ligamentous
22collagen fibers and fibers of the periosteum. Following the initial formation of the ligament, no
major organizational or compositional changes are observed throughout the remainder of fetal
19development.
Two distinct bundles of the A CL are present at 16 weeks of gestation (Fig. 1-2). I n arthroscopy,
the A M and PL bundles can also be appreciated, particularly with the knee held in 90 to 120
degrees of flexion (Fig. 1-3). Finally, cadaveric dissection also reveals two anatomical bundles of
the A CL (Fig. 1-4). I n summary, there is a considerable amount of interindividual variability with
respect to the relative sizes of the AM and PL bundles, as seen in fetal, arthroscopic, and cadaveric
studies; however, all individuals with an intact ACL have both bundles of ligament.
FIG. 1-2 16-week fetus demonstrating two bundles of the anterior cruciate
ligament with the knee in extension (A, sagittal view with medial femoral
condyle removed) and flexion (B, frontal view). AM, Anteromedial; LFC, lateral
femoral condyle; PL, posterolateral.FIG. 1-3 Arthroscopic view of anteromedial (AM) and posterolateral (PL)
bundles in 14-year-old female. Left knee, 110 degrees flexion. LFC, Lateral
femoral condyle.
FIG. 1-4 Two distinct bundles of ACL present in cadaveric specimen. Left
knee, 90 degrees flexion. AM, Anteromedial; LFC, lateral femoral condyle;
PL, posterolateral.Insertion Site Anatomy
A natomical studies have characterized the individual contributions of both the A M and PL
bundles to the overall A CL architecture. Odensten and Gillquist described the femoral origin of
23the A CL as an ovoid area measuring 18 mm in length and 11 mm in width. Within this area, the
A M bundle occupies a position located on the proximal portion of the medial wall of the LFC, and
the PL bundle occupies a more distal position near the anterior articular cartilage surface of the
LFC (Fig. 1-5, A). Harner et al studied the digitized origin and insertion of the A M and PL bundles
in five cadavers and concluded that each bundle occupies approximately 50% of the total femoral
2 2 16origin, with cross-sectional areas of 47 ± 13 mm and 49 ± 13 mm for AM and PL, respectively.
FIG. 1-5 A, Femoral insertion sites of anteromedial (AM) and posterolateral
(PL) bundles (right knee, medial femoral condyle removed). B, Tibial insertion
sites of AM and PL bundles (right knee tibial plateau, menisci removed). Lat
men, Lateral meniscus; MM, medial meniscus.
On the tibia, the insertions of the A M and PL bundles are located between the medial and
lateral tibial spine over a broad area stretching as far posterior as the posterior root of the lateral
meniscus. The full A CL insertion has been described as an oval area measuring 11 mm in
10,15,24diameter in the coronal plane and 17 mm in the sagi- al plane. Within this area the A M
bundle insertion can be found in an anterior and medial position, whereas the PL bundle
insertion is located more posteriorly and laterally (Fig. 1-5, B). Posteriorly, fibers of the PL bundle
are in close approximation to the posterior root of the lateral meniscus and, in some individuals,
may a- ach to the meniscus itself (Fig. 1-6). The overall size of the tibial insertion is approximately
120% of the femoral origin; however, as is the case with the femoral origin, the two bundles share
2approximately equal tibial insertion site areas: the A M bundle occupies 56 ± 21 mm , and the PL
2 16bundle occupies 53 ± 21 mm .FIG. 1-6 Posterolateral (PL) bundle tibial insertion is located just anterior to
the posterior root of the lateral meniscus (Lat men). Left knee, arthroscopic
view.
The size and length of each bundle is also unique. The A M bundle is approximately 38 mm in
10,15,17length. The PL bundle has been less well studied. Kummer and Yamamoto measured the
25PL bundle in 50 cadavers and determined an average length of 17.8 mm. However, the A M and
PL bundles have a similar diameter.
Crossing Pattern
Based on their anatomical positions, the A M and PL bundles change alignment as the knee moves
from extension to flexion. The femoral insertion sites are oriented vertically when the knee is in
zero degrees, and the two bundles of the A CL are oriented in parallel (Fig. 1-7). A s the knee
moves into 90 degrees of flexion, the A M bundle insertion site on the femur rotates posteriorly
and inferiorly, in contrast to the femoral insertion of the PL bundle, which rotates anteriorly and
superiorly. This change in alignment of the insertion sites leads to a horizontal plane of insertions
for the A M and PL bundle with the knee in 90 degrees of flexion (Fig. 1-8). The change in insertion
site alignment causes the two bundles to twist around each other and become crossed. A s the
knee is flexed, the PL bundle can be seen anterior to the A M bundle at its femoral insertion (Fig.
1-9).FIG. 1-7 Crossing pattern of anteromedial (AM) and posterolateral (PL)
bundles. With the knee in extension, the AM and PL bundles are parallel (A,
left knee, medial femoral condyle removed) and the insertion sites are
oriented vertically (B).
FIG. 1-8 Crossing pattern of anteromedial (AM) and posterolateral (PL)
bundles. With the knee in flexion, the AM and PL bundles are crossed (A, left
knee, medial femoral condyle removed) and the insertion sites are oriented
horizontally (B).FIG. 1-9 Arthroscopic view and computer model of anteromedial (AM) and
posterolateral (PL) bundle crossing pattern in extension (top) and flexion
(bottom). The PL bundle is obscured in extension but becomes visible in
flexion as it moves anteriorly on the femoral side. LFC, Lateral femoral
condyle.
Tensioning Pattern
The change in alignment of the A M and PL femoral insertion sites allows the A CL to twist around
itself as it is moved through a complete range of motion. Clearly, this crossing pa- ern, along with
the differences in the length of each bundle, has implications for the tensioning pa- ern of the
overall ligament and each individual bundle. I n a study by Gabriel et al, forces were measured in
each bundle during an anterior load of 134N over several flexion angles, as well as for a combined
26rotatory load of 10 N m valgus and 5 N m internal tibial torque. The results showed that the PL
bundle is tightest in extension (in situ force of 67 ± 30N ) and becomes relaxed as the knee is
flexed, whereas the A M bundle is more relaxed in extension, and reaches a maximum tightness as
12,26the knee approaches 60 degrees of flexion (in situ forces of 90 ± 17N ). This tensioning pa- ern
also can be observed grossly in cadaveric and arthroscopic views of the bundles (Fig. 1-10). The PL
bundle is also observed to tighten during internal and external rotation.FIG. 1-10 Arthroscopic views of an anterior cruciate ligament (ACL)-injured
left knee with an intact posterolateral (PL) bundle and torn anteromedial
bundle (removed). In extension, the PL bundle is tensioned maximally and
appears taut (A), and in 90 degrees flexion, the PL bundle is more relaxed
(B).
I n summary, the A CL consists of two distinct bundles, the A M and PL bundles, and these
bundles contribute synergistically to the stability of the knee. The alignment of the insertion sites
of A M and PL on the femur allows the ligament to become crossed as the knee is flexed and can
be observed as a vertical alignment of the femoral insertion sites during extension and a
horizontal alignment of femoral insertion sites during flexion. We will now turn our a- ention to
biomechanics for a review of the role of the ACL and the specific contributions of each bundle.
Biomechanics
Historical Studies
The field of biomechanics has a long history, with the earliest known considerations dating
back to Chinese and Greek literature around 400 to 500 bc. The first modern work in biomechanics
was completed during the 1500s to 1700s by well-known figures such as Galileo, D aVinci, Borelli,
Hooke, and N ewton. Orthopaedic biomechanics was initially advanced during the 1940s and 1950s
by the work of Eadweard Muybridge, A rthur S teindler, Verne I nman, Henry Lissner, and A . H.
Hirsch. S ince the 1960s, the information learned from biomechanical studies in orthopedics has
been applied to refine clinical treatment approaches.
Anterior-Posterior Translation Control
The dynamic nature of the two bundles of the A CL during knee flexion demonstrates the complex
role of the A CL in stabilization of the knee joint. However, initial biomechanical studies of the
27,28A CL focused mainly on its function of resisting anterior tibial translation. From this work we
know that the in situ forces of the A CL vary considerably during a normal range of motion of the
knee joint. With a 110N anterior tibial load applied, the A CL demonstrates high in situ forces
between 0 and 30 degrees flexion, with a maximum occurring at 15 degrees. I n situ forces are at
their lowest point between 60 and 90 degrees, with a minimum occurring at 90 degrees.
A s mentioned earlier, recent studies have also been completed to evaluate the individual roles
of each bundle of the A CL in anterior-posterior translation. These studies have shown that the
A M bundle has relatively constant levels of in situ forces during knee flexion, whereas the PL
bundle is more variable, with high in situ forces at 0, 15, and 30 degrees of flexion but rapidly
28decreasing in situ forces beyond this angle.
Rotational Stability
Clinical experience has suggested that biomechanical considerations of anterior-posteriortranslation alone do not correlate with subjective evaluations of knee stability and that a more
29complete evaluation of the role of rotational stability is relevant. Therefore, in recent years
26,30,31closer a- ention has been given to the rotational stabilizing function of the A CL. I ncluded
in the study by Gabriel et al was an analysis of a combined rotatory load of 10 N m valgus and
5 N m internal tibial torque at 15 and 30 degrees flexion. For the PL bundle, in situ forces of 21N
were recorded at 15 degrees and 14N at 30 degrees. For the A M bundle, in situ forces were 30N
and 35N , respectively. This demonstrates that the both the A M and PL bundles contribute to
rotational stability of the knee at these angles.
I n addition to biomechanical studies, recent studies using in vivo kinematics analysis have
assessed rotational stability in the A CL during various functional activities such as walking,
32–34running, and cu- ing. A ndriacchi et al studied the in vivo kinematics of normal and A
CLdeficient subjects during four phases of walking and determined that an A CL-deficient knee is
positioned differently than a normal knee. D uring walking, the intact A CL maintains a balance of
rotation during the interval of swing phase to heel strike. However, in the A CL-deficient knee, an
increased internal rotation occurs between these phases of walking, which is maintained through
30the stance phase. A study of running and cu- ing in A CL-deficient patients demonstrated
normal anterior-posterior stability during running but abnormal rotational movements compared
34with subjects with an intact ACL.
Finally, a magnetic resonance imaging (MRI )-based study of the in vivo kinematics of the
normal A CL during weight-bearing knee flexion has demonstrated that several components of
A CL kinematics change during weight-bearing knee flexion. First, as the flexion angle increases,
axial rotation (or twist) of the A CL increases as well. At full extension the A CL is internally
twisted by approximately 10 degrees; however, this increases to approximately 20 degrees when
the knee is moved to 30 degrees flexion, and it increases to approximately 40 degrees with the
knee at 60 to 90 degrees flexion. S econd, the orientation of the ligament within the joint space
changes with the flexion angle. A s the knee flexion angle increases, so does the lateral angulation
of the ligament. Therefore, the ligament may possess a lateral force component, functioning to
32,33constrain internal tibial rotation.
I n summary, the A CL provides an important part of rotational stability during both low- and
high-demand activities by helping to maintain the normal position of the tibiofemoral contact, a
role that is shared by both bundles of the ligament.
Biomechanics Considerations in Anterior Cruciate Ligament Surgery
Based on the aforementioned research into the role of rotational stability, work has been
completed to assess the ability of different surgical techniques in restoring both anterior-posterior
translation of the knee and rotational stability. Yagi et al performed a study comparing a
singlebundle reconstruction with the femoral tunnel placed at the 11- or 1-o’clock position with
anatomical double-bundle A CL reconstruction and the femoral tunnels placed based on the
35insertion site anatomy of the transected A CL. I n this study, the double-bundle A CL
reconstruction was be- er able to resist anterior tibial translation at full extension and 30 degrees
flexion, compared with the single-bundle technique. A dditionally, when a combined internal
tibial and valgus torque was applied at 15 and 30 degrees flexion, the double-bundle A CL
reconstruction had a response closer to the intact A CL compared with the single-bundle
technique.
Yamamoto et al compared the double-bundle A CL reconstruction with a lateral single-bundle
reconstruction, with the femoral tunnel placed approximately at a 10-o’clock position for the right
36knee. The double-bundle anatomical reconstruction be- er restored the anterior tibial
translation at 60 degrees and 90 degrees flexion when compared with the single-bundle
36technique.
Finally, Tashman et al performed an in vivo kinematics analysis of normal and single-bundle
31reconstructed knees. S ubjects with a normal A CL were compared with a group of single-bundle
A CL reconstructed patients to evaluate anterior-posterior translation and knee rotation during
downhill jogging. S ingle-bundle A CL reconstructed patients had fully restored anterior-posteriortranslation as compared with subjects with a normal A CL but were found to lack normal
31rotational kinematics. Because the single-bundle reconstruction is an approximation of the
position of the A M bundle, it can be concluded that part of the rotational stability is derived from
the actions of the PL bundle.
I n summary, Yagi et al and Yamamoto et al have demonstrated that normal anterior-posterior
translation may be restored using traditional single-bundle reconstruction techniques. However,
35,36it is not possible to restore rotational stability using this approach. I n addition, Tashman et
al have shown that single-bundle reconstruction is not capable of restoring normal rotational
36kinematics. A natomical double-bundle reconstruction, in contrast, offers an opportunity to
restore both components of normal knee stability as demonstrated in cadaveric biomechanics
studies, and it is possible that this will soon be demonstrated in an in vivo kinematics model as
35,36well.
Conclusion
The anatomy of the A CL shows that the ligament consists of two distinct and functional bundles,
the A M and PL bundles. These two bundles have unique points of a- achment in the knee, and
this leads to their complex spatial relationship throughout knee flexion, as well as their different
roles in biomechanics and knee stability. I t is important to take the anatomical properties of the
A CL into consideration when performing A CL surgery. This may lead to a more accurate
restoration of knee kinematics to the native state and improvements in long-term outcomes.
However, although the current body of knowledge of the anatomy and biomechanics of the A CL
is extensive, it remains incomplete. Future work in areas such as in vivo kinematics will allow for a
more complete understanding of rotational stability and knee motion during complex
movements.
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tunnel placement. Am J Sports Med. 2004; 32:1825–1832.C H A P T E R 2
Mechanisms of Noncontact
Anterior Cruciate Ligament
Injuries
William E. Garrett, Jr. and Bing Yu
A s in the prevention of other injuries in sports, understanding injury mechanisms
is a key component of preventing noncontact anterior cruciate ligament (A CL)
1injuries. The research effort to determine risk factors of sustaining noncontact A CL
injuries is increasing as the concerns of increased incidents and cost for treatment, as
well as serious consequences of noncontact A CL injuries, are growing. Prospective
cohort studies are commonly used in epidemiological research designs for
2determining risk factors of injuries and diseases and are being used to determine
3risk factors of sustaining noncontact A CL injuries. The results of epidemiological
studies with cohort designs, however, are descriptive in nature and lack
cause-and2effect relationship between identified risk factors and the injury. Without a good
understanding of the injury mechanisms, the risk factors of sustaining noncontact
A CL injuries identified from epidemiological studies could be misinterpreted and
could lead to the selection of nonoptimal injury prevention programs.
I njuries of the A CL frequently occur in athletic movements such as stopping or
quickly changing directions. These kinds of movements often are awkward and
offbalance maneuvers. Video analysis often shows a hard landing with the knee near full
extension in these movements as the athlete experienced a sensation of the knee
collapsing into a valgus position. The quadriceps muscles are likely to be the major
source of the anterior shear force that causes the rupture of the A CL in these
movements. However, we have not been accustomed to considering the fact that our
own muscles can create injuries. A lthough a valgus moment applied to the knee can
create enough deformation to cause an injury of the A CL, few noncontact A CL
injuries involve serious injuries to the medial collateral ligament (MCL) that would
occur if the knee sustained sufficient valgus moment loading to injure the A CL. This
chapter will examine biomechanical studies relating to A CL injury and explore strains
induced by the quadriceps muscles near full knee extension and by valgus moment
loading.
Mechanically, A CL injury occurs when an excessive tension force is applied on the
A CL. A noncontact A CL injury occurs when a person self-generates great forces or
moments at the knee that applied excessive loading on the A CL. A n understanding of
the mechanisms of A CL loading during active human movements, therefore, is
crucial for understanding the mechanisms of noncontact A CL injuries and risk
4factors of sustaining noncontact A CL injuries. Berns et al investigated the effects of>
>
combined knee loading on A CL strain on 13 cadaver knees. The strain of the
anteromedial (A M) bundle of the A CL was recorded using liquid mercury strain
gauges at 0 and 30 degrees knee flexion. The results of this study showed that anterior
shear force on the proximal end of the tibia was the primary determinant of the strain
in the A M bundle of the A CL, whereas neither pure knee internal-external rotation
moment nor pure knee valgus-varus moment had significant effects on the strain of
the A M bundle of the A CL. The results of this study further showed that anterior
shear force at the proximal end of the tibia combined with a knee valgus moment
resulted in a significantly greater strain in the A M bundle of the A CL than did the
anterior shear force at the proximal end of the tibia alone.
5Markolf et al also investigated effects of anterior shear force at the proximal end of
the tibia and knee valgus, varus, internal rotation, and external rotation moments on
the A CL loading of cadaver knees. A 100N anterior shear force and 10-N m knee
valgus, varus, internal rotation, and external rotation moments were added to cadaver
knees. The A CL loading was recorded as the knee was extended from 90 degrees
flexion to 5 degrees hyperextension. The results of this study showed that an anterior
shear force on the tibia generated significant A CL loading, whereas the knee valgus,
varus, and internal rotation moments also generated significant A CL loading only
when the A CL was loaded by the anterior shear force at the proximal end of the tibia.
The results of this study further showed that the A CL loading due to the anterior
shear force combined with either a valgus or a varus moment to the knee was greater
than that due to the anterior shear force alone, whereas the A CL loading due to the
anterior shear force combined with a knee external rotation moment was lower than
that due to anterior shear force alone. The knee valgus and external rotation moment
loading are elements of dynamic valgus that many current A CL injury prevention
3 5programs are trying to avoid. The results of the study by Markolf et al also showed
that A CL loading due to the combined knee varus and internal rotation moment
loading was greater than that due to either knee varus moment loading or internal
rotation moment loading alone and that the A CL loading due to combined knee
valgus and external rotation moment loading was lower than that due to either knee
valgus or external rotation moment loading alone. Finally, the results of this study
showed that the A CL loading due to the anterior shear force and knee valgus, varus,
and internal rotation moments increased as the knee flexion angle decreased.
6Fleming et al studied the effects of weight bearing and tibia external loading on
A CL strain. They implanted a differential variable reluctance transducer to the A M
bundle of the A CL of 11 subjects. A CL strains were measured in vivo when a
subject’s leg was a ached to a knee loading fixture that allowed independent
application of anterior-posterior shear force, valgus-varus moments, and
internalexternal rotation moments to the tibia and simulation of weight-bearing conditions.
The anterior shear force was applied on the proximal end of the tibia from 0N to 130N
in 10-N increments. The valgus-varus moments were applied to the knee from
−10 N m to 10 N m in 1-N m increments. The internal-external rotation moments were
applied to the knee from −9 N m to 9 N m in 1-N m increments. The knee flexion angle
was fixed at 20 degrees during the test. The results of this study showed that A CL
strain significantly increased as the anterior shear force at the proximal end of the
tibia and the knee internal rotation moment increased, whereas knee valgus-varus
and external rotation moments had li le effects on A CL strain under the
weightbearing condition.
The previously mentioned studies consistently showed that the anterior shear force>
at the proximal end of the tibia is a major contributor to A CL loading, whereas the
knee valgus, varus, and internal rotation moments may increase A CL loading when
an anterior shear force at the proximal end of the tibia is applied. A ccording to these
A CL loading mechanisms, a small knee flexion angle, a strong quadriceps muscle
contraction, or a great posterior ground reaction force can increase ACL loading.
Quadriceps muscles are the major contributor to the anterior shear force at the
7proximal end of the tibia through the patella tendon. D eMorat et al demonstrated
that a 4500-N quadriceps muscle force could create A CL injuries at 20 degrees knee
flexion. Eleven cadaver knee specimens were fixed to a knee simulator and loaded
with 4500-N quadriceps muscle force. Quadriceps muscle contraction tests at 400 N
(Q-400 tests) and KT-1000 tests were performed before and after the 4500-N
quadriceps muscle force loading. Tibia anterior translations were recorded during the
Q-400 and KT-1000 tests. A ll cadaver knee specimens were dissected after all tests to
determine the A CL injury states. S ix of the 11 specimens had confirmed A CL injuries
(three complete A CL tears and three partial tears). A ll specimens showed increased
tibia anterior translation in Q-400 and KT-1000 tests. The result of this study also
showed that quadriceps muscle contraction caused not only tibia anterior translation
but also tibia internal rotation.
D ecreasing knee flexion angle increases the anterior shear force at the proximal end
of the tibia by increasing the patella tendon–tibia shaft angle. With a given
quadriceps muscle force, the anterior shear force at the proximal end of the tibia is
determined by the patella tendon–tibia shaft angle, defined as the angle between the
8patella tendon and the longitudinal axis of the tibia. With a given quadriceps muscle
force, the greater the patella tendon–tibia shaft angle, the greater the anterior shear
8force on the tibia. N unley et al studied the relationship between the patella tendon–
tibia shaft angle and knee flexion angle with weight bearing. Ten male and 10 female
university students without known history of lower extremity injuries were recruited
as the subjects. S agi al plane x-ray films were taken for each subject at 0, 15, 30, 45,
60, 75, and 90 degrees knee flexion, bearing 50% of body weight. Patella tendon–tibia
shaft angles were measured from the x-ray films. Regression analyses were performed
to determine the relationship between patella tendon–tibia shaft angle and knee
flexion angle and to compare the relationship between genders. The results showed
that the patella tendon–tibia shaft angle was a function of the knee flexion angle, with
the patella tendon–tibia shaft angle increasing as the knee flexion angle decreased,
and that on average the patella tendon–tibia shaft angle was 4 degrees greater in
females than in males. The relationship between the patella tendon–tibia shaft angle
8and knee flexion angle obtained by N unley et al was consistent with those from
other studies on the patella tendon–tibia shaft angle under non–weight-bearing
9–11conditions.
D ecreasing the knee flexion angle also increases A CL loading by increasing the
ACL elevation angle and deviation angle, defined as the angle between the longitudinal
axis of the A CL and the tibia plateau and the angle between the projection of the
longitudinal axis of the A CL on the tibia plateau and the posterior direction of the
12tibia, respectively. The resultant force along the longitudinal axis of the A CL equals
the anterior shear force on the A CL divided by the cosines of the A CL elevation and
deviation angles. The greater the A CL elevation and deviation angles, the greater the
12A CL loading with a given anterior shear force on the A CL. Li et al determined the
in vivo A CL elevation and deviation angles as functions of the knee flexion angle with>
weight bearing. Five young and healthy volunteers were recruited as the subjects. The
A CL elevation and deviation angles at 0, 30, 60, and 90 degrees knee flexion with
weight bearing were obtained using individualized dual-orthogonal fluoroscopic
images and magnetic resonance imaging (MRI )-based, three-dimensional (3D )
models. The results of this study showed that both the A CL elevation and deviation
angles increased as the knee flexion angle decreased.
S everal studies show that A CL loading increases as the knee flexion angle
13decreases. A rms et al studied the biomechanics of A CL rehabilitation and
reconstruction and found that quadriceps muscle contraction significantly strained
the A CL from 0 to 45 degrees knee flexion but did not strain the A CL when knee
14flexion was greater than 60 degrees. Beynnon et al measured the in vivo A CL strain
during rehabilitation exercises and found that isometric quadriceps muscle
contraction resulted in a significant increase in A CL strain at 15 and 30 degrees knee
flexions but resulted in no change in A CL strain relative to the relaxed muscle
15,16condition at 60 and 90 degrees knee flexion. Li et al investigated the quadriceps
and hamstring muscle loading on A CL loading and showed that the in situ A CL
loading increased as the knee flexion angle decreased when quadriceps muscles were
loaded, regardless of the hamstring muscle loading conditions.
Literature also shows that individuals at high risk of sustaining noncontact A CL
injuries have a smaller knee flexion angle during athletic tasks than do individuals at
low risk. Epidemiological studies show that female athletes are at higher risk of
17–24sustaining noncontact A CL injuries than their male counterparts. Recent
biomechanical studies demonstrated that female recreational athletes exhibited small
25,26knee flexion angles in running, jumping, and cu ing tasks. S tudies also
demonstrate that female adolescent athletes had a sharply increased A CL injury rate
27,28after age 13 years. A recent biomechanical study showed that female adolescent
soccer players started decreasing their knee flexion angle during a stop-jump task
29after age 13 years. Taken together, these results suggest that small knee flexion
angle during landing tasks may be a risk factor of sustaining noncontact A CL
injuries.
I ncreasing peak posterior ground reaction forces during athletic tasks increases
A CL loading by inducing an increased quadriceps muscle contraction. A posterior
ground reaction force creates a flexion moment relative to the knee, which needs to be
30balanced by a knee extension moment generated by the quadriceps muscles. A s
previously described, the quadriceps muscle contraction adds an anterior shear force
on the proximal end of the tibia through the patella tendon. The greater the posterior
ground reaction force, the greater the quadriceps muscle force and the greater the
30 31 32ACL loading. Cerulli et al and Lamontagne et al recently recorded in vivo A CL
strain in a hop-landing task. A differential variable reluctance transducer was
implemented on the middle portion of the A M bundle of the A CLs of three subjects
through surgical procedures. S ubjects then performed the hop-landing task in a
biomechanics laboratory. Force plate, electromyography (EMG), and in vivo A CL
strain were recorded simultaneously. The results of this study showed that the peak
A CL strain occurred at the impact peak vertical ground reaction force shortly after
30initial contact between foot and ground. Yu et al demonstrated that peak impact
vertical and posterior ground reaction forces occurred essentially at the same time.
Taken together, these results suggest that a hard landing with a great impact>
>
posterior ground reaction force may be a risk factor of sustaining noncontact A CL
injuries.
Literature shows that individuals at a high risk of sustaining noncontact A CL
injuries have greater peak posterior ground reaction forces in athletic tasks. Chappell
26et al studied the lower extremity kinetics as well as kinematics of university-age
recreational athletes during landings of stop-jump tasks. Their results showed that
female recreational athletes had greater peak resultant proximal tibia anterior shear
force and knee joint resultant extension moment during landings of stop-jump tasks
than did male recreational athletes. Yu et al studied the immediate effects of a newly
designed knee brace with a constraint to knee extension during a stop-jump
29–29btask. Their results showed that the university-age female recreational athletes
had greater peak posterior ground reaction force during the landing of the stop-jump
30task than did their malecounterparts. Yu et al showed that the resultant peak
proximal tibia anterior shear force was positively correlated to the peak posterior
ground reaction force.
Hamstring co-contractions protecting the A CL have been a longstanding clinical
concept because hamstring muscles provide a posterior shear force on the tibia that is
supposed to reduce the anterior shear force on the tibia from the patellar tendon and
thus unload the A CL. Recent scientific studies, however, did not support this concept.
15Li et al showed in a cadaver study that hamstring co-contraction did not
significantly decrease tibia anterior translation when the knee flexion angle was less
14than 30 degrees. Beynnon et al found that the isometric hamstring co-contraction of
the hamstring muscles did reduce in vivo A CL strain between 15 and 60 degrees knee
33flexion. Kingma et al found that hamstring muscle activation increased only 1.3 to
2.0 times, whereas knee extension moment increased 2.7 to 3.4 times with a knee
flexion angle between 5 and 50 degrees, which did not suggest a hamstring
34 35recruitment pa ern to reduce the A CL loading. O’Connor, Pandy et al, and Yu et
29al all studied A CL loading using a modeling and computer simulation approach
and showed that the hamstring muscles did not reduce A CL loading at all when the
knee flexion angle was small.
A lthough biomechanical studies showed that the knee valgus moment was not a
3major mechanism of A CL loading, a recent epidemiological study by Hewe et al
reported that external knee valgus moment in a vertical drop landing–jump task was a
predictor of A CL injuries. A total of 205 high school soccer, basketball, and volleyball
players were followed for three competition seasons. Knee flexion and valgus angles
at initial foot contact with the ground and the maximum knee flexion and valgus
angles and maximum moments during the stance phase of the vertical drop landing–
jump task were recorded prospectively for every subject. A total of nine subjects
sustained A CL injuries after three competition seasons. The results of this study
showed that knee abduction angle at landing was 8 degrees greater in A CL-injured
than in uninjured athletes and that A CL-injured athletes had a 2.5 times greater peak
external knee valgus moment and 20% higher peak vertical ground reaction force than
did uninjured athletes. The results further showed that peak external knee valgus
moment predicted A CL injury status with 73% specificity, 78% sensitivity, and a
2predictive R value of 0.88. The results of this study appear to suggest an association
between knee valgus angle and moment with ACL injuries.
However, we may have to be cautious when interpreting the association of knee>
>
valgus angle and moment with noncontact A CL injuries observed in the study by
3Hewe et al. The observed preinjury knee valgus moments of the nine subjects who
suffered A CL injuries in this study were less than 0.12 N m/body weight/standing
height. The average body weight and stranding height of the injured subjects in this
study were 62 kg and 1.68 m, respectively. This means that the preinjury knee valgus
moments of the nine injured subjects in this study were less than 12.5 N m. These
4knee valgus moment loadings were similar to those in the studies by Berns et al,
5 6Markolf et al, and Fleming et al, which demonstrated that knee valgus loading did
not significantly affect A CL loading unless a significant proximal tibia anterior shear
force was applied. Furthermore, several other studies in the current literature
demonstrate that knee valgus moment loading alone cannot injure the A CL when the
36MCL is intact. Bendjaballah et al studied the effects of knee valgus-varus moment
loading on cruciate and collateral ligament loadings using a finite element model.
Their results suggest that cruciate ligaments are not major valgus-varus moment
37loading bearing structures when collateral ligaments are intact. Matsumoto et al
investigated the roles of the ACL and MCL in preventing knee valgus instability using
cadaver knees. Their results demonstrate that the MCL is the major structure to stop
38medial knee space opening. Mazzocca et al tested the effect of knee valgus loading
on MCL and A CL injuries. They found that the response of the A CL strain to knee
valgus moment loading was minimal when the MCL was intact but significantly
increased after the MCL rupture began due to knee valgus moment loading. Their
results show that the A CL still had about 60% of its original strength after complete
MCL ruptures with medial knee space openings greater than 15 mm due to knee
valgus moment loading. This study clearly demonstrates that a complete ACL rupture
due to knee valgus moment loading without a complete MCL rupture (grade I I I
injury) is unlikely, whereas clinical observations show that the majority of noncontact
39A CL injuries do not have significant MCL injuries. A recent study by Fayad et al
showed that only 5 of a total of 84 contact and noncontact A CL injuries had complete
MCL ruptures. Taken together, these studies suggest that knee valgus moment
loading alone is not likely to be a major A CL loading mechanism that can result in
A CL rupture or a major risk factor of sustaining noncontact A CL injuries. More
scientific studies are needed before we can confidently interpret the association of
knee valgus angle and moment with noncontact A CL injuries as a sole risk factor of
sustaining noncontact ACL injuries.
I n summary, the current literature clearly suggests that sagi al plane biomechanics
are the major mechanism of A CL loading. D ecreased knee flexion angle and
increased quadriceps muscle force and posterior ground reaction force causing an
increased knee extension moment are requirements for increased A CL loading.
A lthough the external knee valgus moment has been demonstrated to be associated
with A CL injuries, the current literature contains no evidence that knee valgus-varus
and internal-external rotation moments can produce noncontact A CL injuries in and
of themselves without these high sagittal plane forces.
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363.This page contains the following errors:
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C H A P T E R 3
Risk and Gender Factors for
Noncontact Anterior Cruciate
Ligament Injury
Letha Y. Griffin and James Kercher
Introduction
I n the past decade, there has been an increased emphasis on injury prevention in sports.
However, a significant difficulty with designing prevention programs for anterior cruciate
ligament (A CL) injury is our incomplete understanding of risk factors and mechanism of
injury.
Two different schemes exist for classifying risk factors. Risk factors can be divided into
intrinsic factors, meaning those unique to the individual such as anatomy, muscle strength,
and balance, and extrinsic factors, which are external influences on the body including such
factors as shoe-surface interactions, braces, and weather conditions. Risk factors can also be
categorized as environmental, anatomical, hormonal, neuromuscular, and genetic. The la0 er
classification scheme will be the basis for this discussion.
Environmental Risk Factors
Many environmental risk factors specific to A CL injury have been studied, including
weather and playing conditions, shoe-surface interaction, footwear, and bracing. These
variables are important because they represent potentially avoidable risk factors.
The foot plant, the shoe, the surface, and the shoe-surface interaction are critical factors in
noncontact A CL injuries. Basic physics describes static and kinetic frictional forces between
two bodies. Energy is dissipated once the static frictional force is overcome, allowing
movement. This is termed sliding, which causes a shift from static to kinetic frictional force
that is more readily overcome. I t is logical to assume that during foot plant, characteristics
that increase static frictional force between the foot and ground will create higher-energy
forces in the lower extremity.
1Certain studies have examined surface conditions relating to A CL injuries. Olsen et al
2and Torg et al both studied team handball and found an increased risk of A CL injury while
playing on synthetic floors versus traditional parquet floors. Both believed that the
3 4increased friction of synthetic flooring was the cause. Orchard et al, Heidt et al, and
5S cranton et al all reported higher rainfall and cooler temperatures were related todecreased A CL injuries and theorized that dry, hot weather conditions promote increased
frictional forces on the playing field, thus in turn resulting in increased injury rates.
6Lambson et al in a 3-year prospective study looked at footwear to evaluate torsional
resistance of modern football cleats. They compared four styles of football shoes and found
that the edge design, a design having longer irregular cleats at the periphery and many
smaller cleats interiorly, was associated with higher ACL injury rates.
Bracing Pros and Cons
Prophylactic and functional (postreconstructive) knee bracing has long been a controversial
subject. Over the past 20 years, a0 itudes have fluctuated regarding the effectiveness of
braces in preventing knee injury in the uninjured athlete, the A CL deficient athlete, and the
7A CL reconstructed athlete. A study by D ecoster and Vailas on brace prescriptions pa0 erns
noted that there has been a decreasing tendency for orthopaedic surgeons to prescribe A CL
braces. The authors also noted that a primary factor influencing brace prescription by
7orthopaedists was the activity level of the patient.
8 9Early studies on prophylactic brace wear by TeiA et al and Rovere et al indicated no
benefit to brace wear. These authors cited increased rates of knee injury in some athletes
using prophylactic knee braces. I n contrast, two other studies—the West Point study by
10S itler et al involving 1396 cadets at the U.S . Military A cademy who played intramural
11tackle football and the Big Ten Conference study by A lbright et al involving 987 N CA A
football players—concluded that prophylactic knee braces were effective in reducing injury.
S ince these studies, there has been a paucity of data to support prophylactic bracing for
A CL injury protection, but it is believed that braces may provide some advantage to
12,13reducing medial collateral ligament (MCL) injury.
Braces are commonly prescribed following A CL injury or reconstruction; however, li0 le
evidence supports their physiological or biomechanical efficacy. I n a prospective
14randomized clinical trial of functional bracing for A CL deficient athletes, S wirtun et al
found that subjectively, patients had initial sense of increased stability, but these
investigators were unable to find objective benefits. I n contrast, Kocher et al studied the use
of braces to prevent reinjury in 180 A CL deficient alpine skiers and found reinjury occurred
15in 2% of the braced skiers compared with 13% of the unbraced “control” skiers.
Risberg et al investigated the effect of knee bracing after A CL reconstruction in a
prospective clinical trial of 60 patients randomized postoperatively (30 braced and 30
16without brace) with 2 years of follow-up. They found no evidence that bracing affected
knee joint laxity, range of motion, muscle strength, functional knee tests, patient
satisfaction, or pain in braced athletes compared with athletes who did not use a brace
following A CL reconstruction. Furthermore, they found prolonged bracing, which they
defined as brace wear 1 to 2 years postoperatively, produced decreases in quadriceps muscle
strength. McD evi0 et al in a prospective, randomized multicenter study of 100 subjects
likewise found no significant differences between braced and nonbraced subjects following
17ACL reconstruction.
I t has been theorized that damage to the A CL can disrupt mechanoreceptors in the knee
18 19leading to decreased proprioception. Birmingham et al has suggested that brace wear
may help to correct this deficit somewhat, but benefits do not carry over to more demanding
tasks. To examine knee proprioception, researchers have studied the threshold for detection
of passive knee motion and found that brace application to the A CL deficient limb does not
20,21improve the threshold to detect passive range of motion.
A lthough the preponderance of evidence would suggest that braces are ineffective in
protecting the A CL deficient or reconstructed athletic knee, many patients still wish for abrace because they subjectively report that braces increase their confidence during sports
participation.
Anatomical Risk Factors
Recognition of disparities in noncontact A CL injury rates between men and women has led
to much debate on the association of gender-specific anatomical differences as potential
injury risk factors. Proposed anatomical risk factors include increased quadriceps femoris
angle (Q angle), ligamentous laxity in apparent knee valgus, femoral notch size, A CL
geometry, subtalar joint pronation, and body mass index (BMI).
Association Between Q Angle and Injury Risk
The Q angle, which typically ranges from 12 to 15 degrees, is formed by the intersection of
two lines, one from the anterior superior iliac spine to the midpoint of the patella and
another from the tibial tubercle to the same reference point on the patella. I t has been
proposed that an increased Q angle may be associated with an increased risk for knee injury
because excessive lateral forces could negatively influence the knee’s mechanical
22,23alignment.
24,25Females have been reported to have larger Q angles than their male counterparts ;
however, in a trigonometric evaluation, Grelsamer et al reported a mean difference of only
2.3 degrees between the Q angles of men and women and furthermore found that men and
26 25women of equal height demonstrated similar Q angles. S hambaugh et al studied the
relationship between lower extremity alignment and injury rates in recreational basketball
players and found larger Q angles in athletes who sustained knee injures. I n contrast, other
22,27,28 29authors have not been able to relate injury to Q angle. Guerra et al reported that
quadriceps contraction alters Q angle measurements, thus making it difficult to establish a
direct link between static Q angle measurements and injury.
Notch Width as a Risk Factor
S tructural characteristics of the distal femur and femoral intercondylar notch as well as A CL
geometry and the A CL relationship to the intercondylar notch have been implicated as
anthropometric factors associated with A CL injury rate disparity between males and
females. I t has been postulated that a smaller notch, termed notch stenosis, may cause
impingement to the A CL and put it at increased risk of injury, or possibly a smaller notch
may imply a smaller A CL leading to decreased load to failure. A lthough these factors have
30–38 39,40been heavily studied using plain radiography, computed tomography (CT),
41,42 43-45 37magnetic resonance imaging (MRI), and cadaveric and in vitro analysis, a lack of
consistent measurement techniques and findings has made it difficult to interpret results.
Therefore there is still no consensus relating morphology of the intercondylar notch to A CL
injury rates. A chronological summary of the data is listed in Table 3-1.
Table 3-1
Studies Evaluating Notch Size as an Anterior Cruciate Ligament (ACL) Injury Risk
Factor
Year Author Study Design Conclusion Comments
1987 Anderson et Analysis of the Retrospective Significant Notchplasty for
al39 intercondylar study. association those with
notch by Compared between documented
computed bilateral ACL anterior stenosis
tomography tears, outletunilateral stenosisYear Author Study Design Conclusion Comments
tears, and and
normal knees unilateral
in males and and
females bilateral
using ACL tears.
computed No gender
tomography differences
(CT) scan. found.
1987 Houseworth et The Retrospective Narrowed Positive
al40 intercondylar study using posterior association
notch in computer arch of the between
acute tears of graphic notch may notch and
the anterior analysis of predispose injury but
cruciate notch-view a knee to no comment
ligament radiographs ACL tear. on gender
in 50 patients
with an acute
ACL injury
and 50
normal
knees.
1988 Souryal et al112 Bilaterality in Retrospective NWI was Positive
ACL injuries: analysis of significantly association
associated 1120 patients less for between
intercondylar with ACL bilateral notch and
notch ruptures. group injury but
stenosis Devised compared no comment
notch width with on gender
index (NWI) unilateral
to compare and normal
notch widths knees.
on
radiographs.
1993 Souryal et al38 Intercondylar Prospective Athletes with
notch size in blind study stenotic
ACL injuries of 902 high notch have
in athletes school greater risk
athletes. for
ACL injuries noncontact
were ACL injury.
recorded and Limit of
correlated “critical
with NWI. stenosis”
was NWI ofC H A P T E R 4
The Incidence of Anterior Cruciate Ligament Injury as
a Function of Gender, Sport, and Injury-Reduction
Programs
Chadwick C. Prodromos, Yung Han, Julie Rogowski, Brian T. Joyce and Kelvin Shi
Introduction
A lthough many studies have examined the incidence of anterior cruciate ligament (A CL) tears for given populations, an overall understanding
of the real incidences is difficult to ascertain due to the breadth of the data and the disparate manner in which it is reported. The overall
number of A CL tears appears to be increasing. This is caused in part by the increased participation of females in high-risk sports, as females
clearly have an overall higher incidence of A CL tears than males. This realization has spawned the creation of training programs designed to
decrease the incidence of A CL tears in females. The increase in A CL tears is also fueled by the increase in sports participation, from seasonal
to yearlong, by athletes of both genders. This results in an increased number of exposures per year above that which was present for
singlesport athletes in the past. S ome sports appear to have higher risks of A CL tears than others, but these differences have not been well
understood. Knowing the relative and absolute risks of A CL tear as a function of these parameters serves to focus a- ention on preventive
strategies, where it is most needed. It also allows athletes and parents to understand the risks of participation in various sports.
Purpose
Our purpose was to acquire and review all of the relevant peer-reviewed published data on the incidence of A CL tears for the purpose of
comparing the incidence of ACL tears in the following ways:
1. Among sports
2. Between females and males
3. Between those who have completed a program to decrease the incidence of ACL tears and those who have not
Methods
A computerized search of all papers in the peer-reviewed literature that had a possibility of dealing with the incidence of A CL tears was
performed using a variety of indexing terms. S earches were then carried out by individual sports. This produced 793 articles that had some
relation to knee or A CL injuries. These articles were reviewed, and bibliographies were cross-referenced for other papers, which were also
reviewed for the purpose of identifying studies that had actual numerical incidences of complete A CL tears; this eliminated the overwhelming
majority of papers. However, 33 papers were found that did have such quantitative data, and they form the basis for this chapter. Of these 33
papers, 25 had data that either used, or could be converted into, the preferred A CL injury incidence reporting method, namely: “A CL
tears/1000 exposures.” A n exposure is defined as either a practice or a game. These studies are listed in Table 4-1. They are divided by sport and
then subdivided by level of competition, gender, and whether an A CL injury-reduction training program had been applied. The ratio of injury
of females versus males is also listed for studies in which there were cohorts for both genders. These data form the basis for the analyses
present in this chapter.
Table 4-1
ACL Tear Rate by Sport, Gender, and Injury Training*
Male ACL ACL ACLSport Level Subgroup Author Exposures Female Exposures Male
andFemale Tears Tears Tears
Basketball Professional WNBA Trojian22 0.20 9 45,036
Professional† NBA Lombardo23 0.21 15
College NCAA Mihata15 0.17 1393 8,068,016 0.28 1061 3,733,209 0.08 332
NCAA Agel13 0.18 682 3,889,954 0.29 514 1,797,730 0.08 168
Collegiate Harmon36 0.18 359 1,972,170 0.30 275 925,501 0.08 84
NCAA Arendt14 0.17 238 1,375,974 0.30 189 639,898 0.07 49
Naval: Gwinn17 0.28 6 21,734 0.48 5 10,452 0.09 1
collegiate
Naval: Gwinn17 0.14 5 35,226 0.00 0 1360 0.15 5
intramural
Naval: all levels Gwinn17 0.19 11 56,960 0.42 5 11,812 0.13 6
High school Gomez25 0.13 11 84,341.66
Messina24 0.05 15 290,636 0.09 11 120,751 0.02 4
Untrained Pfeiffer19 0.11 2 18,076
Trained 0.48 3 6302
Untrained Hewett21 0.29 3 10,370
Trained 0.42 2 4757 Soccer Adults‡ German Faude20 0.65 11 16,830 Male ACL ACL ACLSport Level Subgroup Author Exposures Female Exposures Malenational andFemale Tears Tears Tears
league
Adults Competitive: Soderman21a 0.18 4.0 22,134
trained
Adults Competitive: 0.04 1.0 27,846
untrained
Adults† Recreational Bjordal18 0.07 131 1,837,455.83
College NCAA Mihata15 0.21 1295 6,283,785 0.32 871 2,736,615 0.12 424
NCAA Agel13 0.21 586 2,840,568 0.33 394 1,208,994 0.12 192
Collegiate Harmon36 0.20 317 1,605,004 0.32 194 604,430 0.12 123
NCAA Arendt14 0.19 178 934,971 0.31 97 308,748 0.13 81
Naval: Gwinn17 0.32 6 18,916 0.77 5 6508 0.08 1
collegiate
Naval: Gwinn17 0.46 12 26,204 2.70 2 742 0.39 10
intramural
Naval: all levels Gwinn17 0.40 18 45,120 0.97 7 7250 0.29 11
High school Untrained Mandelbaum16 0.49 67 137,448
Trained 0.09 6 67,860
Untrained Pfeiffer19 0.11 1 9357
Trained 0.00 0 5913
Untrained Hewett21 0.22 2 9017
Trained 0.00 0 4517
Alpine skiing All ages General Deibert12 0.40 1448 3,641,041
population
Adults General Warme11 0.63 1615 2,550,000
population
Employees Oates9 0.02 19 1,196,496
Employees Viola10 0.04 31 726,836 0.04 10 227,766 0.04 21
Lacrosse College NCAA Mihata15 0.18 315 1,783,903 0.18 146 799,611 0.17 169
American Adults Professional Scranton37 0.07 61
football
High school§ DeLee28 0.11 37
Handball Adults Elite athletes Myklebust31 0.33 28 84,690 0.56 23 40,799 0.11 5
Adults Recreational Seil32 0.24 5
Adults¶ Untrained Petersen30 0.86 5 5815
Trained 1.60 1 625
Young Competitive Wedderkopp38 0.09 4 42,442.42
adults#
Australian Adults Professional: Orchard33 0.82 83
football† 2001
Rugby College Collegiate Levy29 0.36 21 58,296
Naval: Gwinn17 0.22 7 31,263 0.35 3 8475 0.18 4
collegiate
Volleyball High school Untrained Pfeiffer19 0.00 0 11,229
Trained 0.00 0 5739
Untrained Hewett21 0.00 0 3751
Trained 0.00 0 7938
Wrestling College Naval: Gwinn17 0.25 3 11,888 0.77 1 1,306 0.19 2
collegiate
Indoor soccer All ages** General Lindenfeld26 2.78 10 3600 5.21 8 1536 0.97 2
population
All ages†† General Putukian27 5.30 1 190 5.0 2
population*Incidences are expressed as complete ACL tears/1000 exposures.
†Games only.
‡Assumed 1.5 games and 2.25 practices.
§Data was converted by information given by the author.
Assumed 2.25 practices.
¶Per hour, we assumed an exposure for team handball to be 2 hours combined practices and games.
#Assumed season: 1 year; games; 50 minutes.
**Games only: games were 45 minutes, so total player hours were divided by 0.75.
††Games only: exposure is player hours then multiplied the incidence by 1000.
Table 4-2 aggregates like subgroups from Table 4-1 and provides mean injury rates weighted according to the number of exposures. Table 4-3
1–8lists the remaining studies, which use methods other than “tears/1000 exposures” . Table 4-4 aggregates the like populations from studies
that compared incidences by gender. Table 4-5 lists all the studies that involved training regimens designed to reduce ACL tear incidence.Table 4-2
Weighted Means for Groups*
Male and ACL ACL ACL Total
Sport Level Exposures Female Exposures Male Exposures
Female Tears Tears Tears Exposures
Basketball Professional 0.20 9 45,036 0.21 15 70,185
Collegiate 0.17 2694 15,420,034 0.29 2049 7,119,962 0.08 645 8,300,072
High school: 0.10 27 233,538.66 0.02 4 169,885
untrained
High school: 0.45 5 11,069
trained
Soccer German National 0.65 11 16,830 15,949,747.66
League
Adult 0.04 1 27,846
competitive:
untrained
Adult 0.18 4 22,134
competitive:
trained
Adult 0.07 2412 11,754,568
recreational
Collegiate 0.21 2412 11,754,568 0.32 1570 4,873,287 0.12 842 6,881,281
High school: 0.45 70 155,822
untrained
High school: 0.08 6.0 78,290
trained
13,892,945.83
Alpine skiing Employees 0.03 50 1,923,332 0.04 10 227,766 0.04 21 499,070
General 0.49 3063 6,191,041
population
8,114,373
Lacrosse Collegiate 0.18 315 1,783,903 0.18 146 799,611 0.17 169 984,292
1,783,903
American Professional 0.07 61 895,908
football High school 0.11 37 331,561
1,227,469
Handball Elite athletes 0.33 28 84,690 0.56 23 40,799 0.11 5 43,891
Adult 0.86 5 5815 0.24 5 20,462.67
recreational:
untrained
Adult 1.6 1 625
recreational:
trained
Young adults 0.09 4 42,442.42
154,035.09
Australian Professional 0.82 83 100,820
football
100,820
Rugby Collegiate 0.22 7 31,263 0.36 24 66,771 0.18 4 22,788
89,559
Volleyball High school: 0.00 0.00 14,980
untrained
High school: 0.00 0.00 13,677
trained
28,657
Wrestling Collegiate 0.25 3 11,888 0.77 1 1306 0.19 2 10,582
11,888
Indoor soccer General 2.78 14 3600 5.21 9 7126 1.88 5 2664
population
4390
*Incidences are expressed as complete ACL tears/1000 exposures.Table 4-3
Studies not Expressed in ACL Tears/1000 Exposures
Basketball Basketball Basketball Soccer Handball Handball Handball Handball
Author Deitch6 Deitch6 Deitch6 Heidt4 Myklebust31 Myklebust31 Myklebust31 Myklebust31
Year 2006 2006 2006 2000 2003 1997 1997 1997
Level NBA & NBA WNBA High school Amateur/semi- Amateur/semi- Amateur/semi-
Amateur/semiWNBA professional professional professional professional
Details 1996–2002 1997–2002 14- to 18- 1998–1999; 1989–1991 1989–1991 1989–1991
(minus seasons year-old females, upper seasons; two seasons; two seasons; two
strike- females division, seasons, three seasons, three seasons, three
shortened (1 year, 2 Norway, one upper upper upper
1998– seasons) season divisions in divisions in divisions in
1999) Norway Norway Norway
Criteria for Did not Did not Did not Not Arthroscopy Arthroscopy Arthroscopy Arthroscopy
ACL injury specify specify specify specified
definition
Sex M&F M F F F M&F M F
Total ACL 36 22 14 8 29 87 33 54
injury
Game ACL 19 10 9 23
injury
Practice ACL 17 12 5 6
injury
Total number 1145 702 443 258 942 3392 1696 1696
of
participants
Years 6 6 6 1 1 2 2 2
Total player 516 942 6784 3392 3392
seasons
Total player 15,447
game hours
Total player 193,389
practice
hours
Total player 208,836
game and
practice
hours
Number of
games
Total player 93,400 70,420 22,980 15,547
games
ACL 31.4 31.3 31.6 31.0 30.8 25.6 19.5 31.8
injury/1000
players
ACL 5.2 5.2 5.3 31.0 30.8 12.8 9.7 15.9
injury/1000
player years
ACL
injury/1000
games
ACL 1.49
injury/1000
player
game hours
ACL 0.031
injury/1000
player
practice
hours
ACL 0.14
injury/1000
player
game and
practicehours
Basketball Basketball Basketball Soccer Handball Handball Handball Handball
ACL 0.20 0.14 0.39 1.49
injury/1000
player
games
ACL 15.5 30.8 12.8 9.7 15.9
injury/1000
player
seasons
Table 4-4
Ratios of Female to Male ACL Tear Rates*
ACL ACLSport Level Subgroup Author Female Exposures Male Exposures Female/Male P Value
Tear Tear
Basketball College NCAA Mihata15 0.28 1061 3,733,209 0.08 332 4,334,807 3.50
NCAA Agel13 0.29 514 1,797,730 0.08 168 2,092,224 3.63
Collegiate Harmon36 0.30 275 925,501 0.08 84 1,046,669 3.75
NCAA Arendt14 0.30 189 639,898 0.07 49 736,076 4.29
Naval: collegiate Gwinn17 0.48 5 10,452 0.09 1 11,282 5.33
Naval: Gwinn17 0.00 0 1360 0.15 5 33,866 0.00
intramural
Naval: all levels Gwinn17 0.42 5 11,812 0.13 6 45,148 3.23
Mean 0.29 0.08 3.63
High Messina24 0.09 11 120,751 0.02 4 169,885 4.50
school
Mean 0.28 0.08 3.50
Soccer College NCAA Mihata15 0.32 871 2,736,615 0.12 424 3,547,170 2.67
NCAA Agel13 0.33 394 1,208,994 0.12 192 1,631,574 2.75
Collegiate Harmon36 0.32 194 604,430 0.12 123 1,000,574 2.67
NCAA Arendt14 0.31 97 308,748 0.13 81 626,223 2.38
Naval: collegiate Gwinn17 0.77 5 6508 0.08 1 12,408 9.63
Naval: Gwinn17 2.70 2 742 0.39 10 25,462 6.92
intramural
Naval: all levels Gwinn17 0.97 7 7250 0.29 11 37,870 3.34
Mean 0.32 0.12 2.67
Alpine Employees Viola10 0.04 10 227,766 0.04 21 499,070 1.00 0.91
skiing
Lacrosse College NCAA Mihata15 0.18 148 799,611 0.17 169 984,292 1.06
Mean 0.18 0.17 1.05 0.59
Handball Adults Elite athletes Myklebust31 0.56 23 40,799 0.11 5 43,891 5.09
Rugby College Naval: collegiate Gwinn17 0.35 3 8475 0.18 4 22,788 1.94 0.36
Wrestling College Naval: collegiate Gwinn17 0.77 1 1306 0.19 2 10,582 4.05 0.25
Indoor All ages General Lindenfeld26 5.21 8 1536 0.97 2 2064 5.37
soccer population
General Putukian27 5.20 1 190 5.00 3 600 1.04
population
Mean 5.21 1.88 2.77 0.04
*Incidences are expressed as complete ACL tears/1000 exposures.Table 4-5
Effect of ACL Reduction Training Program on Tear Rate*
ACL ACL Change
Sport Level Author Subgroup Female Exposures Subgroup Female Exposures P Value
Tear Tear (T–UT)
Basketball High school Hewett21 Untrained 0.29 3 10,370 Trained 0.42 2 4767 13%
Pfeiffer19 Untrained 0.11 2 18,076 Trained 0.48 3 6302 37%
Mean 0.18 0.45 0.15
Soccer Competitive Soderman21a Untrained 0.04 1 27,846 Trained 0.18 4 22,134 14%
adults
High school Hewett21 Untrained 0.22 2 9017 Trained 0.00 0 4517 –22%
Mandelbaum16 Untrained 0.49 67 137,448 Trained 0.09 6 67,860 –40%
Pfeiffer19 Untrained 0.11 1 9357 Trained 0.00 0 5913 –11%
Mean 0.45 0.08 –24% 0.0001
Volleyball High school Hewett21 Untrained 0.00 0 3751 Trained 0.00 0 7938 0%
Pfeiffer19 Untrained 0.00 0 11,229 Trained 0.00 0 5739 0%
Mean 0.00 0.00
*Incidences are expressed as complete ACL tear rate/1000 exposures.
Exposures
I n all of these studies it is important to remain cognizant of the number of exposures in the given study. The variance in the number of
exposure between the studies is very large. The largest study has more than 8 million exposures and the smallest has only 600, a difference of
more than 10,000 to 1 in the statistical power of the studies. These differences are so important that we have highlighted all the studies with
exposures of more than 100,000 to make it easier for the reader to recognize those incidence studies of greatest statistical power.
Data Conversions
A number of studies report their incidence by dividing the number of A CL tears by hours of participation instead of practices. I n these studies
the hourly incidence was therefore used to calculate an incidence per 1000 exposures by converting hours to practices or games and adjusting
the incidence accordingly. D oing so allowed these series to be used in the comparative analysis with the other studies, which used the tear per
exposure methodology. Without this method, a large number of useful studies would have been lost from the analysis. I f an exact practice
28length was not listed, we assumed a practice length of 2.25 hours. I n the study by D eLee, the data were presented in tears per hour, but exact
data were given on number of practices and games and their lengths, so the data could be directly transformed into tears per 1000 exposures.
Individual Sports
Alpine Skiing
The alpine skiing data are notable for the large disparity in incidence between ski lodge employees, who are assumed to be expert skiers, and
9,10recreational skiers. The two studies of ski lodge employees by Oates and Viola show rates of 0.02 and 0.04, respectively. The two general
11,12population studies by Warme and D eibert show tenfold higher rates of 0.63 and 0.40, respectively. A lthough the rate for the expert skiers
is the lowest for any of the high-risk sports studied, the rate for the recreational skiers is overall one of the highest (P
The lower risk among the expert skiers is presumably a combination of increased skill and increased fitness in this group. The expert group
is also remarkable for being one of only two cohorts for which the rate of injury is the same for males and females.
10The lack of a gender difference in the large study by Viola is also remarkable. A side from lacrosse, alpine skiing is the only sport studied
with a large enough number of exposures to generate reliable numbers to find this lack of a gender difference.
Soccer
13–21The soccer data are dominated by the three extremely large studies of Mihata, A gel, and A rendt. These data are remarkable for their
amazing similarity. The female rates in the Mihata, A gel, and A rendt studies are 0.32, 0.33, and 0.31, respectively; the male rates are 0.12, 0.12,
16and 0.13, respectively. The female–male ratios are all also in the 2.5 to 1 range. The overall female to male difference was highly significant (P
which showed a 24% reduction in A CL tear incidence. I t should be noted that the one adult study showed no reduction in A CL tear incidence
21awith training.
Basketball
A s was the case with soccer, the basketball rates are dominated by the three large studies of Mihata, A gel, and A rendt.* A lso similar to soccer,
the basketball numbers are amazingly similar among the studies. The female rates are 0.28, 0.29, and 0.30. The male rates are 0.08, 0.08, and
0.07. The female to male ratios are 3.5, 3.6, and 4.2. The overall difference in rate between females and males was highly significant (P
Indoor Soccer
The two studies of indoor soccer are included for the sake of completeness, but with only about 3600 total exposures, they have negligible
27,28statistical power by comparison to the more than 10 million soccer exposures by the three large studies cited earlier for outdoor soccer.
Thus the very high female incidence of 5.2 tears per 1000 exposures, more than 10 times the outdoor rate, should be interpreted with caution,
although the difference between females and males was statistically significant (P = 0.04). N onetheless it is of interest that two separate studies
arrived at almost identically high rates. I f these increased rates were real, there would be two obvious potential causes: first, the fact that this
study included only games, not practices, implying a higher risk with competition. S econd, the fact that indoor soccer is played on artificial
turf, whereas outdoor soccer is played on grass, may upwardly influence the injury rate.
Volleyball19,21The two volleyball studies have only 28,000 exposures, again too small to make reliable incidence conclusions. However, it is remarkable
that no A CL tears were recorded in either study. Basketball and soccer are often included with volleyball as high-risk sports for females. The
rates of the six cohorts for basketball and soccer from each of the three large cited studies are all clustered between 0.28 and 0.33. I f the average
rate of 0.30 is applied to the 28,000 volleyball exposures, about 9 A CL tears would be expected. The fact that none were recorded may support a
lower incidence of ACL tears in volleyball than in soccer and basketball.
Football
29The one large football study, all in high school males, produced an injury rate of 0.11. This is very similar to the male rate found in college
soccer (0.12) and basketball (0.08). With more than 331,000 exposures, this study is of high statistical power.
Rugby
The 0.35 and 0.36 rates for women and the 0.18 rate for men from the two published studies are very similar to the 0.32 rate for women and 0.12
17,30rate for men found in soccer. This is not unexpected given the similarities of the sports, which involve running and pivoting on a grass
surface. I t is of interest that the higher level of contact in rugby did not produce a higher A CL tear rate. The 89,000 total exposures are a
significant number, although far less than the soccer exposure numbers. Further supporting the validity of the data, however, is the fact that
two separate rugby studies produced almost identical ACL tear incidences.
Wrestling
17With just under 12,000 exposures, the one wrestling study is of low power. It showed a rate of 0.77 in females and 0.19 in males.
Lacrosse
15There is one published study with usable data for our analysis. The 0.17 rate of A CL tear for men is similar to that of soccer, rugby, and
basketball. The female rate of 0.18, however, is substantially lower than the female rates for these three sports. With 1,783,903 exposures, this
study is of high statistical power. Lacrosse stands as the only sport aside from alpine skiing for which the rates for males and females are
roughly the same. There is no obvious explanation. The argument has been made that the carrying of the stick is A CL tear protective and may
be at least part of the reason for the lower injury rate in females. However, if this were true there would be no obvious explanation for the fact
that such an effect does not serve to lower the rate in males compared with other similar sports.
Handball
30,31The two published female cohorts both have very high incidences of 0.56 and 0.86. The two male cohorts of 0.24 and 0.11 are relatively
31,32unremarkable. The gender difference is significant (P
Australian Rules Football
33The one large published study with usable data showed a quite high A CL tear rate of 0.82 per 1000 exposures (games only in this study). This
is quite high in relation to other sports for males. The 100,000 exposures represent a substantial number, although not as large as some studies.
I t is interesting to note that the indoor soccer study, which was also a games-only study, also had an unusually high tear rate of 0.97. This
suggests the possibility that games have a higher risk of A CL tear than practices, although there are far too li- le data to make this conclusion.
I f this is not a contributing factor, other explanations would include an intrinsically high rate for Australian Rules football or that the rate is
high due to chance in this modest-sized study.
The Overall Risk of Anterior Cruciate Ligament Tear
This chapter has focused on the rate per exposure in determining A CL risk. However, the number of exposures is equally, if not more,
important. The proliferation of club teams for high-risk sports, especially soccer, thus combines a relatively high-incidence sport with a high
yearly number of exposures, leading to an overall high risk. The year-round club soccer player’s A CL tear risk will be much higher than the
now nearly extinct three-sport athlete of years past, many of whom would have engaged in at least one lower-risk sport such as softball,
34baseball, tennis, or swimming during the year. Hewe- ’s prospective study, for example, found a 4.4% 1-year chance of A CL tear in girls
engaged in high-risk sports. For the injury rate of about 0.3 seen in girls’ basketball and soccer, a 5% yearly A CL risk would be seen after 167
1yearly exposures–not an excessive number for a year-round player. Equipped with the incidence contained in this chapter, one need only plug
in a putative number of yearly exposures to generate an approximate risk of yearly ACL tear.
Female–Male Injury Risk Ratio
The female–male ratio for the five sports for which there are reliable data is as follows: basketball, 3.5; soccer, 2.67; rugby, 2.0; lacrosse, 1.05;
expert alpine skiers, 1.0. S occer and basketball dwarf the other sports in level of participation and are the sports usually thought of when this
topic is discussed. For these two sports, the increased risk versus males is overall about 3 to 1. This is obviously a higher rate of A CL tear in
35females versus males but is much less than the rates of 6 or even 8 to 1 that are sometimes cited.
Anterior Cruciate Ligament Tear-Prevention Programs
The published data have shown A CL injury-prevention programs to be effective in high school soccer. The data in this study, however, have
shown no significant benefit in other sports. I n this regard, Pfeiffer et al speculate that significant benefit may require strength and possibly
19flexibility training in addition to landing and agility training.
Implications for Future Anterior Cruciate Ligament Injury-Reduction Research
The most striking finding in this study is the 16-fold reduction in alpine skiing injury rate in expert versus recreational skiers, with no
difference between males and females. This, combined with the success of female A CL tear reduction programs and the lack of a difference in
tear rates in lacrosse, indicates that biological differences between males and females are probably far less important than proper technique. I t
also squarely highlights basketball as the major sport with both the largest gender disparity, at 3.5 females to 1 male, and the only one that
thus far has not proven amenable to reduction of the female rate. A dditional study of technical factors contributing to female basketball A CL
tears should thus be a high priority for future research.
Conclusions
The following conclusions can be made:
1. Females have a roughly 3.5 times greater risk of ACL tear than males in basketball and 2.7 times greater risk in soccer–not the six to eight
times increased risk sometimes cited.2. ACL tear reduction programs have thus far only proven effective in high school soccer but not in basketball.
3. Recreational alpine skiers have a 16-fold higher incidence of tears than expert skiers.
4. Expert alpine skiers and lacrosse players are the only studied athletes in whom females do not have a higher incidence of ACL tears
compared with males.
5. For males, the incidence of ACL tear is similar in football, soccer, and basketball.
6. Volleyball may be a low-risk sport, not high-risk as previously thought, for ACL tear.
7. The approximate yearly risk for ACL tear can be calculated from the data in this chapter. The risk for a year-round female club soccer player
would appear to be roughly 5% per year.
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21a. Soderman, K, Werner, S, Pietila, T, et al. Balance board training: Prevention of traumatic injuries of the lower extremities in female
soccer players? Knee Surg Sports Traumatol Arthrosc. 2000; 8:356–363.
22. Trojian, TH, Collins, S. The anterior cruciate ligament tear rate varies by race in professional women’s basketball. Am J Sports Med. 2006;
10:1–4.
23. Lombardo, S, Sethi, PM, Starkey, C. Intercondylar notch stenosis is not a risk factor for anterior cruciate ligament tears in professional
male basketball players. Am J Sports Med. 2005; 33:29–34.
24. Messina, DF, Farney, WC, DeLee, JC. The incidence of injury in Texas high school basketball. Am J Sports Med. 1999; 27:294–299.
25. Gomez, E, DeLee, JC, Farney, WC. Incidence of injury in Texas girls’ high school basketball. Am J Sports Med. 1996; 24:684–687.
26. Lindenfeld, TN, Schmitt, DJ, Hendy, MP, et al. Incidence of injury in indoor soccer. Am J Sports Med. 1994; 22:364–371.
27. Putukian, M, Knowles, WK, Swere, S, et al. Injuries in indoor soccer. Am J Sports Med. 1996; 24:317–322.
28. DeLee, JC, Farney, WC. Incidence of injury in Texas high school football. Am J Sports Med. 1992; 20:575–580.
29. Levy, AS, Wetzler, MJ, Lewars, M, et al. Knee injuries in women collegiate rugby players. Am J Sports Med. 1997; 25:360–362.
30. Petersen, W, Braun, C, Bock, W, et al. A controlled prospective case control study of a prevention training program in female team
handball players: the German experience. Arch Orthop Trauma Surg. 2005; 9:614–621.
31. Myklebust, G, Maehlum, S, Holm, I, et al. A prospective cohort study of anterior cruciate ligament injuries in elite Norwegian team
handball. Scand J Med Sci Sports. 1998; 8:149–153.
32. Seil, R, Rupp, S, Tempelhof, S, et al. Sports injuries in team handball. Am J Sports Med. 1998; 26:681–687.
33. Orchard, J, Seward, H, McGivern, J, et al. Intrinsic and extrinsic risk factors for anterior cruciate ligament injury in Australian
footballers. Am J Sports Med. 2001; 29:196–200.
34. Hewett, TE, Myer, GD, Ford, KR, et al. Biomechanical measures of neuromuscular control and valgus loading of the knee predict
anterior cruciate ligament injury risk in female athletes. Am J Sports Med. 2005; 33:492–501.
35. Toth, AP, Cordasco, FA. Anterior cruciate ligament injuries in the female athlete. J Gend Specif Med. 2001; 4:25–34.
36. Harmon, KG, Dick, R. The relationship of skill level to anterior cruciate ligament injury. Clin J Sport Med. 1998; 8:260–265.
37. Scranton, PE, Jr., Whitesel, JP, Powell, JW, et al. A review of selected noncontact anterior cruciate ligament injuries in the National
Football League. Foot Ankle Int. 1997; 18:772–776.
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1997; 7:342–347.
*References 13–15, 17, 19, 21–25.C H A P T E R 5
Analysis of Anterior Cruciate Ligament
InjuryPrevention Programs for the Female Athlete
Holly J. Silvers, Robert H. Brophy and Bert R. Mandelbaum
Introduction
The anterior cruciate ligament (A CL) is a crucial stabilizer of the tibiofem oral joint, preventing anterior translation of the tibia on the femur
during weight-bearing activities. The A CL works collectively with the posterior cruciate ligament (PCL) to stabilize the knee during dynamic
movement. The PCL is a* ached to the posterior portion of the intercondylar eminence of the tibia and passes forward to a* ach to the medial
condyle of the femur. The medial collateral ligament (MCL) is a* ached to the medial femoral condyle and the medial surface of the tibia. The
lateral collateral ligament (LCL) is a* ached to the lateral femoral condyle and the lateral portion of the head of the fibula. The MCL and the
LCL are extracapsular ligaments and provide stability to the knee joint in the frontal plane during varus and valgus loads.
S ince the passage of the Title I X Educational A mendment, there has been an exponential increase of female participation in sports at both
1 2the collegiate (fivefold increase over the last 30 years) and high-school (tenfold increase over the last 30 years) levels. A lthough participation
in organized sports has many physical and psychological benefits, including decreases in obesity, hypertension, diabetes mellitus, and
3coronary heart disease, this increase has subsequently led to an increase in sports-related injuries. While identifying risk factors with regard
to sports-related injury, researchers have found an increased rate of ligamentous knee injuries, especially of the A CL, in female athletes
4–9compared with their male counterparts participating in similar activities. A mong athletes in pivoting and jumping sports, adolescent
6,10,11females face a fourfold to sixfold increased risk of ACL injury compared with their male counterparts.
The A CL is at risk for injury during activities that require pivoting, decelerating, or landing from a jump, such as soccer, basketball,
12volleyball, and team handball, as well as A merican football and downhill skiing. A n estimated 80,000 to 250,000 A CL injuries occur annually
12,13in the United S tates alone. The highest incidence of these injuries occurs typically in young athletes between the ages of 15 to 25, which
3constitutes nearly 50% of all reported A CL injuries. Furthermore, the incidence among female athletes exceeds their male counterparts by a
12,13,14twofold to eightfold frequency A rendt and D ick examined the increased incidence of A CL injury among N CA A D ivision I athletes
15participating in basketball and soccer over a 5-year period. These two sports were chosen due to the fact that there is a strong similarity
between the men’s and women’s games with regard to rules, training and development, style of play, type of playing surface, and the intensity
of the competition. The injury rate was recorded and analyzed per athlete-exposure, where one practice session or game was defined as one
exposure. The average A CL injury rate was 0.31 per 1000 athlete-exposures for female soccer and 0.29 per 1000 athlete-exposures for female
basketball, compared with 0.13 for male soccer and 0.07 for male basketball per 1000 athlete-exposures. These epidemiological data for A CL
6injury rates statistically signify the blatant discrepancy that exists between genders.
A CL rupture is a severe ligamentous knee injury, leading to functional instability in the short term and degenerative joint disease in the long
term. I njury to the ligament can lead to prolonged absence from both work and sport and can initiate the early onset of degenerative
15,16osteoarthritis. A lthough A CL reconstructive procedures are readily available, the injury is painful and costly and can be debilitating. I n
14,17the United S tates, at least 50,000 A CL reconstructions are performed each year at a cost of about $17,000 per procedure. The direct medical
cost for reconstructive surgeries alone is just under $1 billion per year ($850,000,000). This figure does not include initial treatment costs of all
A CL injuries, the rehabilitation costs after reconstruction, or the costs of conservative treatment and rehabilitation of those injuries that are
18not repaired. Complete A CL injuries can lead to chronic knee pathology, including instability, secondary injury to the menisci and articular
cartilage, and an early onset of osteoarthritis. A pproximately 66% of all patients with complete A CL injury incur damage to the menisci and the
articular cartilage of the femur, patella, and/or tibia. This injury, coupled with the risk of secondary injury, can significantly decrease the ability
of patients to complete their activities of daily living and affect their quality of life. The surgical reconstruction of a ruptured A CL can
18asignificantly reduce the risk of secondary injury. S eiF et al noted that 65% of A CL deficient patients sustained a secondary meniscal injury
within 2.5 years of the initial date of injury.
D ata show that despite surgical treatment of this injury, patients frequently develop pos* raumatic arthritis of the knee.* D espite the most
earnest efforts of orthopaedic surgeons to preserve the integrity of the knee joint during A CL reconstructive surgery, A CL reconstructed
individuals continue to report with early onset of osteoarthritis. Lohmander et al completed a 12-year longitudinal study to follow up on female
10athletes who previously underwent A CL reconstruction after sustaining an injury while playing soccer. They found that 55 women (82%) had
radiographic changes in their index knee and 34 (51%) fulfilled the criterion for radiographic knee osteoarthritis. The mean age for the subjects
involved with this study was 31.
Gillquist et al noted that the prevalence of radiographic knee gonarthrosis is significantly higher in the injured knee compared with the
16unaffected contralateral limb. The implications of this research are ominous—hence the increased need for the prevention of these injuries
7from occurring in the first place.
A multidisciplinary meeting was held in Hunt Valley, Maryland, in 1999 involving biomechanists, physicians, certified athletic trainers, and
physical therapists to delineate specific risk factors thought to be directly correlated to the increased incidence of A CL injuries in the female
5athlete. The identified risk factors included anatomy, hormones, environment, and biomechanics. This meeting spurred the development of
various A CL injury-prevention programs and led to increased interest and financial funding in this area of research. This group of researchers
reconvened in Atlanta, Georgia, in J anuary 2005 to reevaluate the identified risk factors and to determine what progress has been made since
the inaugural meeting in 1999.
Anterior cruciate ligament Injury-Prevention Studies
A growing number of injury-prevention programs targeted at reducing the risk of ligamentous knee injury in general and A CL injury in
particular have been reported in the literature. A lthough a number of risk factors for A CL injury have been proposed, only the biomechanical
2,14risk factors have been examined in sufficient depth to support the design and evaluation of prevention interventions.
5D uring passive motion, tension in the A CL decreases from 0 to 35 degrees and then increases again with further flexion. Thus, a
combination of maximal A CL tension and anterior tibial translation force occurs with quadriceps firing and joint compressive loading at or
near full extension. Contraction of the hamstrings decreases A CL strain in all positions. However, co-contraction of the hamstrings is not7enough to overcome the strain produced by the quadriceps.
A s the knee moves into extension, female athletes take a significantly longer time to activate their hamstrings than do their male
8,9counterparts. At initial contact, males take approximately 150 ms to achieve their peak flexion angle compared with females, who take
approximately 200 ms. Landing from a jump, in-line deceleration, and pivoting all involve eccentric contraction of the quadriceps to prevent the
4–6extended knee from collapsing into flexion. In laboratory studies, multiple authors have demonstrated significant anterior translation of the
tibia with quadriceps contraction, particularly at 0 to 45 degrees of flexion. This anterior translation force is even greater when the quadriceps
4contraction is combined with a joint compressive force. These findings are the basis for A CL prevention strategies that emphasize proper
biomechanics to address proper landing kinematics (hip and knee flexion while avoiding genu valgum), increase peak flexion angles, and
improve hamstring activation and strength.
Most prevention programs a* empt to alter dynamic loading of the tibiofemoral joint through neuromuscular and proprioceptive training.
The studies to date that focused on biomechanical modifications have resulted in the reduction of lower-extremity injuries in athletes.
However, the studies vary widely both in their approach to injury prevention and the validity of the study design. Most studies to date have
been nonrandomized, and very few have been conducted as randomized, controlled trials.
N evertheless, a number of common elements tie these programs together. Most include one or more of the following: traditional stretching,
strengthening, awareness of high-risk positions, technique modification, aerobic conditioning, sports-specific agility, proprioceptive and
balance training, and plyometrics. The relation of these components to specific risk factors for ACL injury has been summarized in Table 5-1.
Table 5-1
Potential Biomechanical Deficits and Suggested Interventions
Position Intervention Strategy Method of Intervention
Extended knee at initial contact Knee flexion Concentric hamstring control and soft landing
Extended hip at initial contact Hip flexion Iliopsoas and rectus femoral control and soft landing
Knee valgus with tibial-femoral Address dynamic control, decrease dynamic Lateral hip control upon landing
loading valgus
Balance deficits Proprioception drills Dynamic balance training
Skill deficiency Improve agility Agility drills to address deceleration techniques and core
stability
Results of Studies Published to Date
I n an a* empt to analyze existing A CL prevention programs, the studies are grouped and reviewed by their approach to injury prevention,
25beginning with the more global interventions and working up to the more comprehensive programs. E* linger et al looked at the
effectiveness of an educational program to prevent A CL injury among downhill skiers by increasing awareness of injury mechanism and
avoidance. S everal studies have looked at the effect of isolated proprioception training on A CL injury risk, whereas a slightly more involved
approach included neuromuscular training in landing and cu* ing techniques. A nother pair of studies looked at the efficacy of technique
training coupled with strengthening. S everal more studies used a combination of neuromuscular training modalities. Finally, a number of
studies have used a comprehensive approach to prevention of A CL injury, working on strength, flexibility, and agility as well as proprioception
and plyometric training. The studies to date are summarized in Table 5-2.Table 5-2
Summary of Anterior Cruciate Ligament Prevention Studies
Study Design Sport N Gender Training Modalities
Int Control Education Strength Proprio Plyo Agility
Type of Isolated Ettlinger, 1995 P/NR/C Skiing 4000 na M/F ×
Intervention
Cahill, 1978 P/NR American 1227 1254 M ×
Program football
Caraffa, 1996 P/NR S 300† 300† M ×
Soderman, 2000 P/R S 121 100 F ×
Combination Hening, 1990 P/NR BB na na F × ×
Wedderkopp, P/R/C TH 111 126 F × × ×
1999
Pfeiffer, 2004 P/NR S/VB/BB 577 862 F × ×
Hewett, 1999 P/NR S/VB/BB 366 463 F* × × ×
Myklebust, 2003 P/NR TH 855 942 F × × ×
Comprehensive Heidt, 2000 P/R S 42 258 F × × × ×
Olsen, 2005 P/R/C TH 958 879 M/F × × × ×
Mandelbaum, P/NR S 1041 1905 F × × × ×
2005
Gilchrist, 2004 P/R/C S 575 854 F × × × ×
P, Prospective; R, randomized; N R, nonrandomized; C, controlled; S, soccer; V B, volleyball; B B, basketball; T H, team handball.
*Study also included male controls.
†Estimate.
Education
25E* linger et al used a relatively simple approach to prevention of A CL injury in downhill skiers, a* empting to modify high-risk–related
behavior through education and increased awareness. I n this prospective nonrandomized trial, 4000 on-slope alpine ski instructors and
patrollers in 20 ski areas completed training and reporting requirements during the 1993–1994 ski season. The training kit included a 19-minute
A CL awareness training videotape that showed 10 recorded A CL injuries sustained by alpine skiers of various levels, as well as various wri* en
materials. The videotape used guided discovery, allowing viewers to visualize carefully selected stimuli and incorporate this information into
their skiing to avoid high-risk behavior and manage high-risk situations to reduce the risk of A CL injury. Participants also underwent an
awareness training session that included proper body positioning, understanding of the phantom-foot A CL injury mechanism, and strategies
to avoid high-risk positions as well as effective reaction strategies.
The two seasons prior to the intervention season served as historical controls, and area employees had sustained an average of 31 serious
A CL sprains per season. D uring the intervention season, employees sustained 16 serious A CL sprains, 6 in the untrained group and 10 in the
trained group, which was a 62% reduction compared with the normalized expected number of 26.6 ACL injuries in the trained individuals (P
This study demonstrates that educational efforts and visual aids to increase awareness effectively reduce the number of significant A CL
injuries in an alpine skiing population. A significant aspect of this study was the lack of physical biomechanical intervention. Based on the
success of other intervention studies, it would be interesting to look at the effect of a similar awareness program combined with specific
biomechanical training for alpine skiers.
Isolated Strengthening and Conditioning
26Cahill and Griffith looked at the effect of incorporating weight training into preseason conditioning for high-school American football teams.
Over the 4 years of the study, they noted a reduction in reported knee injuries and knee injuries that required surgery in the intervention
group.
Isolated Proprioceptive Training
27Two studies have looked at the effect of isolated proprioceptive training on A CL injury risk, both in soccer players. Caraffa et al conducted a
nonrandomized prospective study with 600 semi-professional and amateur soccer players in Umbria and Marche, I taly. Twenty teams (10
amateur and 10 semi-professional teams; Group A) underwent proprioceptive preseason training in addition to their regular training session.
The control group (Group B) consisted of 20 teams (10 amateur and 10 semi-professional teams) and continued training in their usual fashion.
The intervention group (A) was subjected to a five-phase progressive balance training program consisting of the following: no balance board,
rectangular balance board, round balance board, combination (rectangular/round), and a biomechanical ankle platform system (BA PS ) board(Camp J ackson, MI ). The duration/frequency was 20 minutes per day for 2 to 6 days per week, including a minimum of 3 times per week during
the season. The groups were followed for 3 years, and the senior author evaluated all players with a potential knee injury.
Group A (intervention) reported 10 arthroscopically confirmed A CL injuries over three seasons (0.15 A CL injuries per team/season)
compared with Group B (control), which reported 70 such injuries (1.15 ACL injuries per team/season) (P
28S oderman et al conducted a randomized, prospective controlled trial looking at the effectiveness of a balance board training program to
reduce injuries in female soccer players. A total of 13 teams in the S wedish second and third division participated in the study, with seven
teams (N = 121 players enrolled, 62 completed) in the intervention group and six teams (N = 100 players enrolled, 78 completed) in the age- and
skill-matched control group through one outdoor season. The intervention consisted of a 10- to 15-minute balance board training program in
addition to regularly scheduled games and practices. The players were instructed to complete the program daily for 30 days and continue with
three sessions per week thereafter. Injuries were assessed with regard to number, incidence, type, and location.
The intervention group had more major injuries (8) compared with the control group (1) (P = 0.02) and a total of four A CL injuries were
reported in the intervention group compared with one in the control group. A lthough a major limitation of this study was the 37% dropout
rate, balance board training alone did not decrease the incidence of ACL injury in this cohort.
Based on these two studies, the role for isolated proprioceptive training in efforts to prevent A CL injury is unclear. A major concern is that
the training methods used in both of these studies involve a large commitment both in terms of training time and financial cost of equipment,
which may decrease compliance with regard to large-scale injury-prevention efforts.
Neuromuscular Training: Technique
I njury prevention has also been considered with the design of a neuromuscular training program to modulate existing athletic technique.
29Henning implemented a prevention study in two NCAA Division I female basketball programs over the course of 8 years. Henning proposed
that the increased rate of A CL injury in female athletes was primarily functional, being related to knee position and muscle action during
dynamic movement. I n knee extension, the quadriceps exerts a significant anterior translational force on the tibia, thus imparting a shear force
on the A CL. Conversely, as the knee moves into flexion, the anterior translational force on the tibia is decreased, thereby decreasing the torque
on the ACL secondary to the contraction of the hamstrings. In order to decrease the risk of ACL injury, Henning proposed that the athletes cut,
land, and decelerate with knee and hip flexion. I n addition, he proposed a rounded cut maneuver instead of a sharp or more acute angle during
the cut cycle. He also proposed that a one-step stop deceleration pa* ern should be avoided and a three-step quick stop be instituted instead.
This intervention program was geared at changing player technique, stressing knee flexion upon landing, using accelerated rounded turns, and
decelerating with a multistep stop. This protocol was completed on the basketball court without any additional equipment requirements.
29The intervention group was noted to have an 89% reduction in the rate of occurrence of A CL injuries. S adly, D r. Henning’s death in 1991
prevented the publication of this research. However, his research served as the crucial foundation of numerous prevention programs that
ensued.
Neuromuscular Training: Technique and Strengthening
31Henning’s concept of athletic modulation has been widely accepted and expounded. Wedderkopp et al tested a program including functional
strengthening and balance training (use of an ankle disc for 10 to 15 minutes at all practice sessions). Teams were randomized into two groups,
with a total of 11 teams (N = 111) in the intervention group and 11 teams (N = 126) in the control group.
The group using the ankle disc incurred 14 injuries compared with 66 injuries in the control group (P
32Pfeiffer et al developed the Knee Ligament I njury-Prevention (KLI P) program, involving 15 minutes of strengthening and plyometric
activities, for female high-school soccer, volleyball (VB), and basketball (BB) players. I n the first season of a 2-year, nonrandomized prospective
study, 43 schools participated in the program (17 BB: N = 191; 11 soccer: N = 189; 15 VB: N = 197) and 69 schools served as the control group (28
BB: N = 319; 14 soccer: N = 244; 27 VB: N = 299). The study design included a training session for the coaches and athletic trainers and weekly
compliance checks for athlete participation for both games and practices. N o significant difference between the two groups was found after
one season: there were three arthroscopically confirmed A CL injuries reported in the intervention athletes (incidence rate 0.167) compared
with four (incidence rate 0.078) in the control group. A necdotally, there were no noncontact A CL injuries in the intervention soccer and
volleyball players; all of the injuries in the intervention group occurred among basketball players. Possible explanations for the lack of impact
include the abridged duration of this intervention program (9 weeks) and the fact that the program was conducted post-training.
N euromuscular fatigue at the end of training may directly affect biomechanical technique of the athlete and limit any potential protective
benefit of ACL injury-prevention programs.
Neuromuscular Training: Varied
Other studies have incorporated additional dimensions of neuromuscular training into A CL prevention efforts. The Cincinnati S portsmetric
33includes flexibility, strengthening (through weight training), and plyometric activities over a duration of 60 to 90 minutes. Hewe* et al
researched the effect of this program on the incidence of knee injury in high school–age soccer, volleyball, and basketball athletes. Forty-three
teams (N = 1263 athletes), including 15 female teams (N = 366), implemented the program, and 15 additional female teams (N = 463) served as
the same-sex untrained control. Thirteen male sports teams (N = 434) served as the male control group. Coaches and trainers implemented the
program based on a videotape and manual. The program was performed 3 days per week on alternate days. S eventy percent of the intervention
athletes (248/366) completed the entire 6-week program, and the remainder completed at least 4 weeks of training to be included in the study.
The incidence of serious knee injuries (N = 14) in the female control group was 0.43 per 1000 player-exposures, compared with 0.12 in the
female intervention group (P = 0.05) and 0.09 in the male control group. The intervention group also had a lower rate of noncontact injuries (P =
0.01) and noncontact A CL injuries (P = 0.05). The incidence of noncontact knee injury was 0.35 per 1000 player-exposures in the control group,
compared with 0 in the intervention group and 0.05 in the male control group.
When the data were stratified according to sport, no A CL injuries were reported in volleyball players. A mong the soccer athletes, there were
five A CL injuries reported among the female control athletes (0.56 per 1000 player-exposures), none among the female intervention athletes,
and one among the male control group (0.12 per 1000 player-exposures). A mong the basketball players, eight A CL injuries were reported; five
among the female control athletes (0.48 per 1000 player-exposures), two among the trained athletes (0.42 per 1000 player-exposures), and one
among the male controls (0.08 per 1000 player-exposures).
When the data were stratified with regard to sport, the distribution of athletes varied widely. The intervention female group included 185
volleyball players, 97 soccer players, and 84 basketball players. The control female group included 81 volleyball players, 193 soccer players, and
189 basketball players. The male control group included 209 soccer players and 225 basketball players. The discrepancy within gender and
respective sport cohorts weakens the strength of the study’s conclusion. I n addition, the number of A CL injuries reported throughout this
2,5,34prospective study was lower compared with historical controls.
35A CL injuries have also been problematic for European team handball players. Myklebust et al conducted a nonrandomized prospective
study looking at 900 D ivisions I –I I I competitive female handball players over a 3-year period in N orway. S ixty teams (942 players in the 1998–
1999 season) served as the control athletes (CA s), and 58 teams (855 players in the 1999–2000 season) and 52 teams (850 players in the 2000–
2001 season) served as the intervention athletes (I A s). The intervention consisted of a 15-minute program focused on landing, cu* ing, and
planting technique with 5 minutes spent on each of three exercise components: floor, balance mat, and wobble board. The program was 5
weeks long, with different exercises introduced each week. The program was to be completed three times per week during the first 5 to 7 weeks
and then once per week during the season. A physical therapist was designated to each team to assess compliance during the secondintervention season (2000–2001). S pecial equipment included an instructional videotape, a poster delineating the tasks to be completed, six
balance mats, and six balance boards.
Teams were required to conduct a minimum of 15 training sessions over the 5- to 7-week period with a minimum of 75% player participation.
Only 15 (26%) of the 58 teams from season 2 and 15 (29%) of the 52 teams from season 3 completed the necessary number of sessions, although
compliance was higher among the elite division teams (42% and 50%, respectively).
Overall, there were 29 A CL injuries during the control season, 23 injuries during the first intervention season (odds ratio [OR], 0.87;
confidence interval [CI ], 0.50–1.52; P = 0.62) and 17 injuries during the second intervention season (OR, 0.64; CI , 0.35–1.18; P = 0.15). However,
during the second intervention season, 14 A CL injuries occurred in players with no training (2.2%) compared with 3 A CL injuries in the players
who completed training (1.1%) (P = 0.31). I n the elite division alone, 4 A CL injuries occurred in the players with no training (8.9%) compared
with 1 ACL injury in those who completed training (0.6%) (P = 0.0134).
This intervention included elements of plyometric activities, proprioception, and agilities but did not include any elements of strength.
Limitations of the study include nonrandomization of the subjects, insufficient power, and control data that were collected during an earlier
season. S trengths of the study include measures of compliance by a medical clinician (physical therapist) and the use of an educational
videotape and poster. The study suggests that the inclusion of a neuromuscular balance–based training program may impart some protective
benefit to the ACL.
Neuromuscular Training: Comprehensive
A number of comprehensive A CL injury programs have been proposed in the literature. These programs incorporate a full range of
34neuromuscular training, including strengthening, flexibility, agility, proprioception, and plyometrics. Heidt et al developed the Frappier
A cceleration Program (FA P) as a 7-week preseason training program to address A CL injuries in the high-school–age female soccer population.
Three hundred female soccer players were followed over the course of 1 year (one high-school season and one club/select season). The control
group included 258 athletes, whereas the intervention group included 42 athletes. The Frappier A cceleration Program consisted of
sportsspecific aerobic conditioning, plyometrics, sports cord resistance drills, strength training, and flexibility that was individually customized by
sport, player position, and specific deficits. The plyometric progression was from unidirectional to bidirectional to multidirectional and vertical
challenge (2-inch increments using foam obstacles). I njuries were defined as a player missing practice or a game, and athletic exposures were
not recorded in this study.
Although there was a significant reduction in injuries, from 91 (37%) in the control group to 7 (14%) in the intervention group (P
36Olsen et al studied a program designed to prevent lower limb injury in youth team handball. European team handball clubs (120 teams;
intervention = 61 teams, 958 players; control = 59 teams, 879 players) participated in an 8-month intervention program that consisted of four
sets of exercise lasting 15 to 20 minutes. The training consisted of warm-up exercises (jogging, backward running, forward running, sideways
running, and speed work), technique (plant, cut, and jump shot landing), balance (passing, squats, bouncing, perturbation), and strength and
power (squats, bounding, jumps, hamstrings). Each club was instructed on how to perform the program and was issued a training handbook,
five wobble boards (N orpro, N orway), and five balance mats (A irex, S wiF erland). The program focused on proper biomechanics during
landing, core stability, and inter-rater feedback between team members. The intervention teams consisted of 16- to 17-year-old males and
females who completed 15 consecutive training sessions at the start of the season, followed by 1 training session per week for the remainder of
the season.
There were 66 (6.9% of players) lower limb injuries reported in the intervention group (I G) compared with 115 (13.1%) in the control group
(CG) (relative risk, 0.51; 95% CI, 0.36–73; P
Many of these intervention programs require special equipment, specialized training, or significant time commitment. I n 1999 an expert
panel convened by the S anta Monica (California) Orthopedic and S ports Medicine Research Foundation designed the A CL “PEP Program:
Prevent I njury and Enhance Performance.” This prevention program consists of warm-up, stretching, strengthening, plyometrics, and
sportspecific agilities to address potential deficits in the strength and coordination of the stabilizing muscles around the knee joint. I t was designed
as an alternative warm-up so that the desired activities could be performed on the field during practice without specialized equipment for ease
of implementation. The program consists of an educational videotape or D VD that demonstrates proper and improper biomechanical
37technique of each prescribed therapeutic exercise. An entire team can complete the 19 components in less than 20 minutes.
A n early nonrandomized study among highly competitive 14- to 18-year-old female club soccer players using the program demonstrated
37promising results. D uring the first year of the study (2000), 1041 female club soccer players (52 teams) performed the PEP program, and 1902
players (95 teams) served as the age- and skill-matched controls. There were 2 A CL tears (0.2 A CL injuries per athlete-exposure) in enrolled
subjects versus 32 A CL tears (1.7 A CL injuries per athlete-exposure) in the control group—an 88% decrease in A CL ligament injury. I n year 2
(2001) of the study, four A CL tears were reported in the intervention group, with an incidence rate of 0.47 injuries per athlete-exposure.
Thirtyfive A CL tears were reported in the control group, with an incidence rate of 1.8 injuries per athlete-exposure. This corresponds to an overall
74% reduction in ACL tears in the intervention group compared with an age- and skill-matched control group in year 2.
The limitations of this study include nonrandomization of the subjects, no consistent direct oversight of the intervention, and compliance
measurements that were only completed in a small subset of intervention teams.
The strengths of the PEP Program include the fact that it is an on-field warm-up program that requires only traditional soccer equipment
(cones and soccer ball). I t is completed two to three times per week over the course of the 12-week soccer season and is 20 minutes in duration.
I t includes progressive strength, flexibility, agility, plyometric, and proprioceptive activities to address the deficits most commonly
demonstrated in the female population. D eceleration pa* erns are addressed, stressing the multistep deceleration pa* ern and proper landing
technique, and it encourages knee and hip flexion while landing on the ball of the foot and avoiding genu valgum by using the abductors and
lateral hip musculature. I n addition, because the program is designed as a warm-up, compliance rates are higher and the element of
neuromuscular fatigue does not affect the performance of the therapeutic exercises.
This aforementioned study was followed by a randomized controlled trial using the PEP Program in D ivision I N CA A women’s soccer teams
38in the 2002 fall season. S ixty-one teams with 1429 athletes completed the study, with 854 athletes participating on 35 control teams and 575
athletes participating on 26 intervention teams. N o significant differences were noted between intervention and control athletes with regard to
age, height, weight, or history of past ACL injuries.
A fter using the PEP Program during one season, there were 8 A CL injuries in the intervention athletes (I A) (rate of 0.14) versus 18 in control
athletes (CA) (rate of 0.25) (P = 0.15). There were no A CL injuries reported in I A during practices versus 6 in CA (0.10) (P = 0.01). D uring game
situations, the difference was nonsignificant (I A , 7; CA , 12; P = 0.76). N oncontact A CL injuries occurred at more than three times the rate in CA
(N = 10; 0.14) than in I A (N = 2; 0.04) (P = 0.06). Control athletes with a prior history of A CL injury suffered a reoccurrence five times more
frequently than the I A group (0.10 versus 0.02; P = 0.06); this difference reached significance when limited to noncontact A CL injuries during
the season (0.06 versus 0.00; P
Overall, these studies provide evidence that prevention-training programs have a quantifiable effect on A CL injury risk. This has been
demonstrated in male and female athletes from various sports and across different age groups. Only three of the reviewed studies showed no
effect of training on A CL injury risk; two of them were significantly underpowered and the third implemented the prevention program
posttraining and for a relatively short duration (9 weeks). Eight studies demonstrate a significant decrease in A CL injury risk for some or all of the
study population. Prospective studies of comprehensive prevention programs in large cohorts have been particularly encouraging.
Nevertheless, a number of important questions remain.Areas for Further Research
Program Specifics
Practically, a cost-benefit analysis needs to be considered prior to initiating an injury-prevention program on a large scale. First, what
equipment, if any, is necessary, and at what cost? Extensive and more expensive equipment is necessary for programs such as the Frappier
34 33 30 31,34,35A cceleration Program, the Cincinnati S portsmetric program, and the various programs using some form of a balance board. ,
37,38 29Other successful programs such as PEP and the Henning program do not have such prohibitive requirements. S econdly, what is the
minimal time commitment needed to provide adequate protection? How long and how frequent should training sessions be? When should
these programs be introduced? What is the minimum duration of an injury-prevention program, or does it need to be continued, perhaps at a
lesser frequency throughout the course of the season? When initiating a neuromuscular intervention program, it takes approximately 4 to 6
weeks to impart a benefit onto the athlete. Most of the programs studied to date have a relatively intense start-up period for 4 to 6 weeks
followed by less frequent, and in some cases, no additional training.
Timing of Intervention
D oes the age of the athlete ma* er, and would intervention at an earlier age provide longer-lasting and perhaps be* er protection, or will
“booster” training be necessary throughout the career of any athlete at risk? The young female athlete 15 to 25 years of age is known to be at
particularly high risk for A CL injury and may need different treatment than other populations. The S anta Monica Orthopedic Group is
currently collaborating with the University of S outhern California to delineate the appropriate age to introduce such programs and to
determine what elements of the program effectively change faulty biomechanical patterns.
How Do These Programs Work?
More broadly, what is the optimal A CL injury-prevention program? I n order to answer this question, it becomes necessary to determine the
precise biomechanical adaptations that develop in athletes as a result of participating in these programs. The “pathokinetic chain” of increased
hip adduction moment, decreased hip abduction control, and increased hip adduction angles is surmised to place the lower extremity in a
valgus position. With increased internal rotation moment and motion at the knee joint, possibly in combination with ground reaction force, the
ACL may be overloaded to failure. How do the injury-prevention programs make this less likely to occur? Although further clinical studies may
offer some insight into the optimal prevention program, a definitive answer will remain elusive until the biomechanical implications of
clinically successful intervention programs are studied and better understood.
Individual Versus Population-Based Programs
Once the specific responsive adaptations resulting from an injury-prevention program are known, will screening become possible? I f an athlete
already exhibits the biomechanical behaviors that are known to result from injury-prevention training, is there any benefit to completing or
continuing the program? Can individuals be assessed and undergo tailored interventions as opposed to a global program? A s we continue our
research efforts to further delineate the mechanism(s) of A CL injury, it may be possible to “red flag” specific individuals who demonstrate
biomechanical pa* erns that may directly correlate to an increased risk of A CL injury. I n addition, the age of exposure to a neuromuscular
training program may be a key piece of the prevention puzzle. I f the program is instituted prior to the onset of puberty and, perhaps, prior to
faulty biomechanical patterns being neuromuscularly ingrained, can we avoid the development of these patterns in the first place?
Effect on Performance
A nother important issue is the effect of A CL injury-prevention programs on athletic performance. This is particularly important when the
relatively poor compliance with some of the injury-prevention programs reviewed previously is compared with the much higher rates of
39–43compliance, upwards of 80% to 90%, that have been reported with training targeted toward improving performance.
Recent studies have begun to assess this issue, and the results are encouraging. In 1996, before the program had been found to decrease ACL
44injury risk, Hewe* et al reported that the S portsmetric program increased vertical jump, improved control of dynamic loading of the knee,
45and increased hamstring strength, power, and peak torque in female volleyball players. Wilkerson et al looked at the impact of the Cincinnati
S portsmetric program on performance in a small cohort of female collegiate basketball players. They found significantly increased hamstring
43strength in the intervention group but no other changes in either group. Meyer et al looked at the effect of an enhanced training program
based on the Cincinnati S portsmetric program on performance. I n this study, female athletes demonstrated increased strength and power and
47improved knee biomechanics after training compared with no change in the control group. Paterno et al created their own program of
exercises similar to those described in the literature for injury prevention and found improved single-limb total stability and anteroposterior
48 35stability. There was no control group in this study. Holm et al looked at the influence of the program used by Myklebust on female team
handball players and found an improvement in dynamic balance but no other significant changes. A gain, there was no control group for this
study. Thus, although these studies suggest there may be some improvement in performance from participation in A CL injury-prevention
programs, further study, particularly with larger, well-designed studies, is needed to more precisely assess the impact of such programs on
performance.
Conclusion
There appears to be a quantifiable reduction in A CL risk for athletes, particularly females, who complete well-designed injury-prevention
programs. Most of these programs a* empt to alter dynamic loading of the tibiofemoral joint through neuromuscular and proprioceptive
training. A n emphasis on proper landing technique, landing softly on the forefoot and rolling back to the rearfoot, engaging knee and hip
flexion upon landing and with lateral (cu* ing) maneuvers; avoiding excessive genu valgum at the knee upon landing and squa* ing; increasing
hamstring, gluteus medius, and hip abductor strength; and addressing proper deceleration techniques are activities that seem to be inherent in
each of the aforementioned A CL prevention protocols. Further electromyography and biomechanical analysis is warranted to be* er
understand and identify the mechanism(s) of ACL injury and the activities that offer a protective effect to the ACL.
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C l i n i c a l
OUT L INE
Chapter 6: Diagnosis of Anterior Cruciate Ligament Tear
Chapter 7: Nonoperative Management of Anterior Cruciate Ligament Deficient
Patients
Chapter 8: Arthrosis Following Anterior Cruciate Ligament Tear and
ReconstructionC H A P T E R 6
Diagnosis of Anterior Cruciate
Ligament Tear
Chadwick C. Prodromos and Brian J. Murphy
Introduction
The overwhelming majority of orthopaedists are very skilled in the diagnosis of
anterior cruciate ligament (A CL) tears. However, acute A CL tear is perhaps the most
underdiagnosed orthopaedic condition that usually requires surgery because most
tears present to emergency room or primary care providers who cannot necessarily be
expected to make the diagnosis. The history and exam and diagnostic tests are less
reliable than commonly thought, and the presentation is often not “classic.” Failure
to refer to an orthopaedist in these cases, or failure of the patient to actually see the
referred-to orthopaedist, results in underdiagnosis and delays in diagnosis that can
extend over months or years.
Diagnosis in the Acute Versus the Chronic Setting
D iagnosis of complete A CL tears differs in some respects in the acute versus the
chronic state regarding the history, physical exam, and diagnostic tests. This chapter
will discuss the acute versus chronic diagnostic dichotomy for each of these
diagnostic modalities. I n the acute se/ ing the diagnosis is primarily of the A CL tear
itself, whereas in the chronic se/ ing the diagnosis more often includes the signs and
symptoms of secondary damage. Because the most important aspect of A CL
reconstruction is the prevention or mitigation of subsequent meniscal and articular
damage to the knee, it is paramount that A CL tears are diagnosed and treated acutely
before such further damage occurs.
Partial Tears
This chapter deals primarily with complete ACL tears. Traditionally, partial tears have
been found to produce a smaller degree of anteroposterior (A P) laxity than complete
tears on Lachman or instrumented Lachman testing, as described later. Until the
present time, the only alternatives have been nonoperative treatment or complete
reconstruction, which would necessitate ablation of the remaining ligament. Given
these alternatives, nonsurgical treatment has been the usual alternative if less than
150% of the ligament was torn. With more awareness of A CL double-bundle anatomy,
2single-bundle repairs that preserve the remaining ligament have been developed.
These repairs have been used in some cases of single-bundle partial A CL tear.
Lachman testing and arthrometer testing in these cases appear to show 2- to 3-mm
asymmetry in anteromedial (A M) bundle tears and 1- to 2-mm asymmetry in3posterolateral (PL) bundle tears. A rthroscopy is required for definite anatomical
diagnosis. The pivot shift is of much greater value in the anesthetized versus the
awake patient. D iagnostic criteria as well as surgical indications and techniques in
these cases continue to evolve.
History
Acute
4–10The history and mechanism of A CL tear are familiar to all orthopaedists. The
history most commonly entails twisting, landing, or a valgus blow to the knee.
However, almost any history of knee trauma can be associated with A CL tear. These
atypical histories may represent unusual mechanisms or inaccurate remembrances by
the patient. The important point is never to eliminate A CL tear from the differential
diagnosis based on the history. Classically, swelling is marked within a few hours.
However, some A CL tears never produce more than minimal swelling, even acutely.
Patients often hear or feel a “pop,” but many do not. S imilarly, patients may have felt
the knee “go out of place,” or felt their “leg go one way and the body another” but
often they have not felt these sensations. Pain may be severe and persisting or may be
mild and transient.
N onorthopaedists are aware that A CL tear is a serious injury and are often misled
into thinking that the injury “is only a sprain” because the history and exam are much
less dramatic than they are expecting for such a serious injury. Team physicians
should therefore perform a Lachman test on any knee injury during a game because
A CL tears in the heat of competition are often not obvious by the athlete’s historical
account and sometimes produce li/ le pain initially before swelling sets in. This
underdiagnosis by history is particularly true in emergency rooms (ERs), where the
diagnosis of A CL tear may not be made by the emergency physician. Patients will
often feel that the injury is not serious, especially if they do not have a concomitant
meniscal tear, which would have produced its own set of symptoms. This is
particularly true if the injury is called a “sprain,” such that the patient in many cases
feels that there is no need for orthopaedic follow-up. Because magnetic resonance
imaging (MRI) will usually not be ordered at this time, the diagnosis is easily missed.
Patients with meniscal or articular cartilage damage will usually have continued
symptomatology from their cartilage damage and are more likely to follow-up.
Patients with bucket-handle tears and locked knees will virtually always seek further
care and be diagnosed accurately by the exam or MRI, or at arthroscopy.
Chronic
Chronic A CL tears often present because of pain from a meniscal tear or articular
cartilage damage. Patients may or may not give a history of instability. Classically
instability will occur during pivoting, but the symptoms can take almost any form. I t
can be confused with patellar instability, particularly in adolescents, as well as
meniscal tear. A ny symptom of instability should cause the orthopaedist to rule in or
rule out ACL tear.
Physical Exam
Pivot Shift
The pivot shift is a specific but very insensitive test for A CL tear in the11,12nonanesthetized patient. I t is also subject to great interobserver error. Because
the pivot shift is often quite painful when positive, has low sensitivity, and usually
adds nothing beyond the Lachman test, I (C. Prodromos) use it only rarely for the
diagnosis of A CL tear in the office. I do use it routinely in the 1- and 2-year follow-up
exams, where its negativity confirms that ACL reconstruction has been successful.
Lachman Test
13The Lachman test, the anterior drawer test in approximately 20 degrees of flexion, is
11the most reliable exam test for A CL tear but is far more reliable in the chronic case,
when secondary restraints have stretched and there is less hamstring spasm, than in
the acute case. A fter 21 years of sports medicine practice, I still find the Lachman
inconclusive with some frequency in the acute se/ ing, particular in regards to the
differential between partial and complete tear, because of persisting hamstring
spasm. The firmness of the endpoint may be particularly hard to evaluate. The
examiner may or may not be successful in relaxing the hamstrings. Palpating them
posteriorly and simultaneously while asking the patient to relax them is often
effective. I t is important that the patient is in the supine, not si/ ing, position, and he
or she should be instructed to relax the entire body to help relax the knee. The
Lachman test should be considered definitive only if it is clearly negative with a firm
endpoint. It is important that the examiner be able to differentiate between a negative
Lachman test and a false negative caused by this hamstring spasm to avoid missing a
torn ACL.
Anterior Cruciate Ligament Versus Posterior Cruciate Ligament Tear
A posterior cruciate ligament (PCL) tear produces increased A P laxity and can mimic
an A CL tear. Classically there will be increased A P laxity, but with a firm anterior
endpoint, with a PCL tear. However, this can also be seen with a healed partial A CL
tear. I f there is a question of A CL versus PCL tear, then MRI or the quadriceps active
14test should be used to differentiate the two. I n addition, it is wise to always
arthroscopically inspect the knee before any graft harvesting takes place to make
certain that the ACL is in fact completely torn.
Valgus Laxity
I n patients with coexisting medial collateral ligament insufficiency, and hence valgus
laxity, the Lachman test can be false positive. Rotation of the lax proximal medial
tibial plateau can mimic translation of the entire proximal tibia if rotation is not
carefully controlled by the examiner during the exam. Thus, when the examiner is
aware that valgus laxity exists, he or she should pay particular a/ ention to controlling
tibial rotation during the test to minimize this possibility. This can be challenging in
patients with large-girth lower extremities.
Locking
15,16“Pseudolocking” may be seen classically with partial tears. However, a knee with
a 20-degree or so persisting flexion contracture (i.e., pseudolocking) can occasionally
be seen with isolated complete A CL tear from hamstring spasm alone. True locking is
seen with A CL tear in combination with displaced bucket-handle meniscal tears. I n
these cases the “locking” is actually reflex hamstring spasm in response to extension
in the presence of the displaced meniscal tear. Thus, the Lachman test is always17difficult to perform and frequently false negative because of the hamstring spasm.
Hemarthrosis
The presence of a large hemarthrosis is much more highly associated with A CL tear
18–21 22in adults than in children. Patellar dislocation and fracture are other leading
causes of hemarthrosis. The former can usually be accurately diagnosed by physical
exam, the la/ er by radiography. A rthrocentesis is usually not indicated. I ts only
diagnostic value is in determining whether a large effusion is a hemarthrosis. I n most
of these cases, an MRI will be ordered, which will provide much more information
and spare the patient the pain of the arthrocentesis. I f the effusion is sufficiently
tense, hemarthrosis may be indicated for pain relief. I f MRI is unavailable and the
exam is equivocal, then arthrocentesis may be useful. A 16-gauge needle is preferable,
but an 18-gauge needle may be used.
Patellofemoral Injury
A lthough concomitant A CL tear and patellar dislocation or injury is unusual, it does
23occur. The presence of physical exam signs of acute patellar instability should not
cause the examiner to fail to test for ACL instability.
KT-1000 or Other Instrumented Lachman Test
24–29The KT-1000 (Figs. 6-1 and 6-2) maximum manual examination is a highly
accurate method for definitive diagnosis of A CL tear that is heavily relied on in our
clinic. When it indicates a complete A CL tear, we generally do not order an MRI scan.
A side-to-side difference of more than 4 mm, particularly with an absolute value of 10
30or more, is nearly 100% specific for complete A CL tear if the examiner is
experienced in its use. The more difficult differential may be between complete and
partial A CL tear. We have found partial A CL tears to usually have a laxity of 2 or
3 mm. When it is greater, a complete tear has almost always existed. Others have
31found a slightly larger range. Larger differences, up to 4 and perhaps 5 mm, can be
seen after A CL reconstruction without graft discontinuity. I t is important to point out
that the maximum manual test is more reliable than other methods. A 20-lb pull in
particular will understate the amount of laxity. The 30-lb pull will as well, but to a
32lesser extent. Other arthrometers are in use, particularly in Europe, with reportedly
33good results. We have no experience with them.FIG. 6-1 Maximum manual examination is the most accurate
KT1000 testing mode.
FIG. 6-2 Most complete tears will have a reading of 10 mm or
more as well as a side-to-side difference of 4 mm or more on
maximum manual testing.
A s described earlier, PCL tears can mimic A CL tears. The “quadriceps active
14test” performed with the KT-1000 has been shown to reliably differentiate the two.
Examination Under Anesthesia
The examination under anesthesia (EUA) dramatically increases the sensitivity of the12pivot shift test. The accuracy of the KT-1000 is also improved. We may perform both
just prior to arthroscopy when the diagnosis is in doubt. The differential in question
is usually between a partial and complete A CL tear. EUA may appear to be
unnecessary because arthroscopic examination can seemingly determine whether a
complete tear exists. However, with partial tears the EUA is a valuable supplement to
the arthroscopic findings in determining whether reconstruction is needed. The
difference between a partially torn but substantially intact A CL that would do well
with conservative treatment versus a completely torn A CL that has scarred in with
fibrofa/ y tissue and is essentially functionless is not always obvious arthroscopically.
I n these circumstances the EUA is very helpful in helping to determine proper
treatment.
Radiographs
Radiographs are typically negative; however, certain radiographic signs may be
present. These include the lateral tibial rim or “segond” fracture and posterior lateral
34tibial plateau fracture or lateral femoral condyle impaction fracture. Tibial spine
peaking is common in chronic tears but is a nonspecific sign. Tibial eminence fracture
is seen occasionally in the skeletally immature and rarely in the skeletally mature
(Figs. 6-3 and 6-4). Radiographic signs of a hemarthrosis are usually present.FIG. 6-3 A rare tibial eminence avulsion ( a r r o w ) in an adult,
producing instability equivalent to interstitial anterior cruciate
ligament (ACL) tear.FIG. 6-4 A rare tibial eminence avulsion ( a r r o w ) in an adult,
producing instability equivalent to interstitial anterior cruciate
ligament (ACL) tear.
Magnetic Resonance Imaging
S ensitivity rates of 80% to 81% for arthroscopically proven complete A CL tears have
30,35been reported using MRI . Others have reported accuracy rates of more than
36,37 3890% and sensitivity and specificity over 95%. However, Tsai et al found only a
3967% specificity rate for complete tear. The MRI was very sensitive for detecting
some A CL injury, but it was much less specific for differentiating the complete from
the partial tear. This is an important distinction because the former is usually a
surgical lesion, whereas the latter is usually not.
A lthough MRI is a useful test, a negative MRI should not rule out an A CL tear thatotherwise seems present clinically. The best course of action in such circumstances is
to either obtain a KT-1000 exam by a reliable operator and/or to proceed to
examination under anesthesia using the pivot shift and Lachman tests and to direct
arthroscopic examination if necessary.
The normal A CL is both distinctly seen and appears taut (Fig. 6-5). The torn A CL is
indistinct and appears lax (Fig. 6-6). Bone bruises (Fig. 6-7) in the lateral compartment
40,41are seen in roughly half of acute A CL tears. Their absence should thus not be
relied on to rule out A CL tear. A fracture of the posterior lip of the tibia is another
characteristic finding (Fig. 6-8). Transchondral fracture with intact articular cartilage
is sometimes also seen (Fig. 6-9).
FIG. 6-5 The a r r o w points to a normal anterior cruciate ligament
(ACL) on an oblique sagittal T2 weighted image. Note that the
ACL is taut and well defined.FIG. 6-6 The a r r o w points to a completely torn anterior cruciate
ligament (ACL), which appears ill defined and lax within the
intercondylar notch on sagittal T2 weighted image.FIG. 6-7 The a r r o w s point to some areas of hypointensity on a
T1 weighted coronal image, which are consistent with lateral
compartmental bone contusions in this patient with complete
anterior cruciate ligament (ACL) tear.FIG. 6-8 Sagittal proton density image. The a r r o w points to
oblique transchondral fracture of the posterior tibia without
evidence of step-off of the articular plate in this patient with
complete anterior cruciate ligament (ACL) tear.FIG. 6-9 Inversion recovery coronal image. The a r r o w points to
buckled black subchondral cortex. Below is intact articular
cartilage. The white starburst area above is subchondral bone
edema in this patient with complete anterior cruciate ligament
(ACL) tear.
High-field MRI machines generally produce be/ er accuracy for A CL tears than
lowfield MRI machines and should be obtained where possible. I f the only available
high-field MRI machine is closed-field and the patient is claustrophobic, oral
diazepam may be given. This will enable many such claustrophobic patients to
undergo a closed test, especially if they understand that the improved quality of the
images is worth their trouble. Finally, the skill of the radiologist is extremely
important. The same study can be interpreted as positive or negative depending on
the radiologist’s experience. A skilled radiologist can be of great help to the
orthopaedist in interpreting difficult cases. False-positive MRI s are less common but
also occur. One study found MRI to add no diagnostic accuracy beyond history,
42physical exam, and radiographs (but not KT-1000) for all A CL tears. We believe this
is greater clinical diagnostic accuracy than most orthopaedists, including the author,
would achieve.
Conclusions
1. Lachman testing is the most accurate physical exam test for ACL tear diagnosis in
the nonanesthetized patient.2. KT-1000 or other instrumented Lachman test in the hands of an experienced user is
a highly accurate method of examination for ACL tear.
3. MRI is a very good test but is less accurate than commonly thought, particularly
regarding the differentiation of partial from complete tears. In suspected complete
tears with negative MRIs, examination under anesthesia using both the Lachman
and pivot shift tests, instrumented Lachman testing, and/or arthroscopic
examination should be performed.
4. Very high diagnostic accuracy rates can be obtained by a synthesis of the history,
physical exam, and plain radiographs in obvious cases and the addition of MRI,
examination under anesthesia, and/or instrumented Lachman testing in
questionable cases.
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C H A P T E R 7
Nonoperative Management of
Anterior Cruciate Ligament Deficient
Patients
Elias Tsepis, George Vagenas, Giannis Giakas, Stavros Ristanis and Anastasios Georgoulis
Anterior Cruciate Ligament Deficiency: The Need for Muscle
Strengthening
The knee joint’s location in the middle of the lower limb kinetic chain is imposed to high loads,
1,2which reach multiple the body mass, particularly in the single stance phase of sport activities.
3–5Rupture of the anterior cruciate ligament (A CL) destabilizes the knee joint, thus making A CL
deficient knees prone to repeated subluxations, which form a potential cause for secondary
6–8damage to the joint. S ubsequently, dynamic stabilization through the quadriceps and
9,10hamstrings becomes very crucial for the protection of the injured knee. A part from its
mechanical role, the A CL functions as a sensory organ due to the mechanoreceptors within its
11substance. A fter its rupture, this function is lost, and therefore optimization of the lower limb
muscle properties becomes increasingly important in order to compensate for the resulting
anterior and rotational knee instability.
Exercise in A CL deficient patients aims at the improvement of various aspects of muscle
properties including reflexes, strength, endurance, and coordination with other muscles.
Functional exercise that reeducates the neuromuscular coordination holds the central role in
rehabilitation programs, as growing evidence supports the development of preprogrammed
compensatory muscle activation strategies for efficient shear force dissipation during injured
12–16knee loading. However, the fundamental issue of the need for strength testing and the value
of strengthening exercises still leaves room for investigation.
A mong the criteria for progression of A CL rehabilitation is the level of quadriceps and
17,18hamstring weakness. S trength testing and exercise have been traditionally incorporated into
musculoskeletal rehabilitation regimens. A lthough the connection between the level of
19–22quadriceps strength and functional status has been disputed, some studies support the
interrelation between functional performance of the knee and thigh muscle strength. I t is of
clinical importance for A CL rehabilitation that patients with greater than normal strength in the
23injured limb seem to reduce abnormalities during low- and high-stress activities. Quadriceps
strength appears to determine the functional ability of the A CL deficient or operated limb to a
24,25 26great degree. I ts weakness coincides with low functional performance and pathological
27gait pa ern. I n addition, functional improvement in A CL deficient athletes after training
23,28followed the same pattern as the strength of both the quadriceps and hamstrings.
Likewise, increase in hamstring strength after functional exercise incorporating strengthening,
stretching, and plyometric drills paralleled a decrease in peak landing forces, and hence safer
29 10,30landing. Hamstring strength has also been associated with the level of knee function and
31performance, and increasing the hamstring–quadriceps (H:Q) strength ratio has be come a rule
32,33in order to promote dynamic control of the A CL deficient knee. Even more, this
34improvement has been connected with the return to physical activity after A CL injury, and the=
23,28strength of both thigh muscle groups reflects the functional improvement and the ability to
34return to physical activity.
I t appears that changes in muscle strength might be a global reflection of muscle properties,
35including neural changes. I t seems that adequate strength ensures that a solid basis is built for
other refined neuromuscular properties. I n other words, adequate strength secures the proper
background for the development of global muscle properties. Therefore, it appears that objective
evaluation of strength has a valuable position in the functional assessment after A CL injury, and
in combination with our findings, it could be suggested that therapeutic intervention should
minimize strength weakness, which persists over time when not addressed.
Importance of the Hamstrings, Especially in Soccer Players: Our
Research
Our group recently investigated the connection of thigh muscle strength with the level of knee
performance and the chronic stage of the injury in A CL deficient athletes. I n order to reveal the
net effect of A CL rupture on muscle strength, we examined amateur soccer players who abstained
from structured rehabilitation in an attempt to exclude interference of exercise with the results.
The first study focused on revealing a possible connection of quadriceps and hamstring
30strength deficits with the level of knee function determined by Lysholm score. Three groups of
A CL deficient amateur soccer players were examined at different levels of knee function and were
compared with a group of controls matched for the preinjury level of activity. The median
Lysholm scores of the low, intermediate, and high knee functioning groups were 64.5, 76, and 86
points, respectively. Weakness depicted by the contrast to the healthy condition was significant in
all cases and ranged from 19% to 35% according to the muscle or the patient group. Regarding the
side-to-side deficit, these major muscle groups did not follow the same pa ern. The strength
asymmetry of the quadriceps was consistently significant even in the high functioning knees,
being greater than 14%, in contrast to the hamstrings, which revealed acceptable symmetry within
the normal levels (about 2% to less than 6%) at the high and intermediate knee function groups.
Only the poorly functioning athletes had a significant 19% deficit (Fig. 7-1), which places
hamstring strength asymmetry (H asymmetry) as a discriminating factor for knee functionality.=
FIG. 7-1 The percentage of extensor and flexor deficit in each experimental
group formed according to the level of knee function (L1, L2, and L3: high,
intermediate, and low Lysholm score, respectively) and the percentage of
asymmetry in the control group (dominant versus nondominant knee).
The importance of assessing H asymmetry is highlighted in our recent study that examined
different groups of amateur athletes involved in cu ing and twisting sports such as soccer,
36basketball, and handball at different times since A CL rupture. We tested the quadriceps and
hamstring strength of 36 patients with unilateral A CL deficiency who were divided into three
equal groups with mean times for chronicity of about 4, 11, and 57 months for short term,
intermediate term, and long term, respectively. We investigated how the strength weakness
evolved with time, using the strength of matched healthy controls as a baseline score.
A dditionally, we questioned whether the quadriceps’ and hamstrings’ side-to-side asymmetry in
strength would be consistently significant in all stages of chronicity.
A s in the previous study, significant weakness was evident in both muscles in all patient
groups, ranging from 21% to 32%. Considering the side-to-side asymmetry of A CL deficient
knees, the quadriceps deficit persisted through time, whereas the hamstrings regained symmetry
even after 1 year without organized rehabilitation. Regarding the side-to-side strength differences,
they tended to lower with time, but in the case of quadriceps, they varied from 10% to 23%,
whereas the hamstrings were significantly asymmetric only in the short-term group (14%) and
acquired acceptable symmetry within 1 year postinjury (Fig. 7-2).=
=
=
FIG. 7-2 The percentage of extensor and flexor deficit in each experimental
group (injured versus intact knee: short term, intermediate, long term) and the
percentage of asymmetry in the control group (dominant versus nondominant
knee).
Both studies show a trend for hamstring symmetry much more emphatically than the
quadriceps as function improved or as the distance from the incidence of rupture increased. The
strength asymmetry evident only in the worst-functioning group and the short-term group might
reveal a natural compensatory reaction for A CL deficiency because no patients followed a
structured rehabilitation program. A supplementary finding of both studies was that the strength
of the healthy side was considerably affected by the disuse, which was depicted on the mean
reduction to the level of performance by a mean of 3 to 3.5 degrees Tegner. This raises the issues
of ensuring not to neglect the intact side as well and counseling patients to maintain activity with
safe exercise after injury.
The quadriceps muscle is affected to a greater degree after A CL injury possibly because of (1)
postinjury neural inhibition due to the loss of afferent feedback from A CL to gamma motor
37,38 39,40neurons and (2) the adaptation toward a “quadriceps avoidance gait” pa ern to prevent
41,42anterior subluxation, which unloads the limb, promoting quadriceps weakness in A CL
12deficient patients. The greater atrophy of the quadriceps (10% versus 4%) reported even 1 year
7postinjury may also add to the explanation of their higher deficit compared with the hamstrings.
I n contrast, evidence exists that the hamstrings are recruited in weight-bearing activities in a
5,43subconscious a empt to counteract anterior shear forces. This stimulus might have assisted
with the improvements in our patients. Evidence in the literature also supports the development
of subtle electrophysiological modifications in A CL deficient patients that retune the hamstrings
and preprogram their muscle activation strategies to optimize shear force dissipation during
14–16injured knee loading.
In another study, we investigated the quality of muscle contraction when ACL deficient patients
performed maximal exercise via the smoothness of the torque curve throughout knee extension
44and flexion. Our methodology comprised transformation of each torque-time curve pa ern into
the frequency domain (power spectrum) via fast Fourier transform in order to quantify the
smoothness of the isokinetic curve (Fig. 7-3). Each curve of biological signal that is not a perfect
sine is actually the sum of other curves, and therefore it can be analyzed into its fundamental
components. Our biological interpretation of this method is based on the notion that disturbed
motion is generally connected to poor level of joint functionality. Irregular torque output has been45,46connected to other pathologies such as anterior knee pain. I n contrast, smoothness of torque
47generation is indicative of enhanced force control. The frequency contained at three levels of the
total power of the signal (90%, 95%, and 99%) was calculated in order to exclude noise from the
100% power level but still include enough harmonics. Both extension and flexion isokinetic curves
demonstrated increased irregularities as expressed by the higher-frequency contents by 18.8%,
10.6%, and 40.0% for knee extension and 49.5%, 24.5%, and 16.3% for knee flexion, according to the
power level of assessment (Fig. 7-4). A lthough the results regarding quadriceps were expected on
the basis of previous reports using different methodologies, the hamstrings’ increased
irregularity had not been reported elsewhere. This finding might be of functional importance and
open a future area of investigation.
FIG. 7-3 A characteristic extensor (A) and flexor (B) isokinetic curve of the
intact knee (blue line) and the anterior cruciate ligament (ACL) deficient knee
(red line), demonstrating the side-to-side difference to the torque-time curve
smoothness.=
=
=
=
FIG. 7-4 Example of transformation of the isokinetic data of knee extension
from the time domain (A) to frequency domain (B). The arrow shows the
frequency content calculated for 99% of the signal power.
The higher oscillations characterizing the isokinetic curve of the A CL deficient knee, which is
expressed in increased frequency contents, may be a ributed to mechanical and/or
neuromuscular factors. I ncreased anterior gliding of the tibia during knee extension might
37,38account for the mechanical part. Quadriceps inhibition and poorly coordinated activation
43,48within the hamstrings must explain the neural aspects of abnormalities of mechanical
output. This loss of smoothness in extension-flexion might be clinically important and should be
investigated further. Quantification of irregularity of the extension-flexion curve is an innovative
approach and could be a valuable tool in the assessment of ACL deficient knees.
Review of the Literature on the Role of the Quadriceps and
Hamstrings in Anterior cruciate ligament Deficient Knees
19,30,36,49The quadriceps is the muscle group suffering the most dramatic effects after A CL tear.
For this reason, in addition to its functional importance for normal gait, it a racts most of the
a ention from clinicians and researchers. Quadriceps torque deficit is more than double
10,18hamstring deficit, which is a ributed to its susceptibility for quick atrophy due to disuse and
37,38neural inhibition. Marked weakness of the quadriceps prevents the knee from functioning
30normally, and given that this weakness is exaggerated in many cases, it should be managed
adequately. I f the voluntary deficit measured via superimposed electrical burst to the maximal
voluntary contraction exceeds 5%, treatment with electrical stimulation effectively ameliorates
50loss of the quadriceps strength and should be implemented from the early stages. A lthough in
A CL deficient knees there is no graft to be stressed due to the anterior instability of the tibia
9,42,51caused by quadriceps contraction particularly near extension, this might be harmful for
other capsuloligamentous structures.
I n contrast, the hamstrings are properly located to counteract anterior tibial instability at
52–54flexion angles exceeding 30 degrees. However, doubts exist regarding the efficacy of the
53,55hamstrings to counterbalance shear loading of the knee, based on two concerns: first,
whether the magnitude of the posteriorly directed muscle force is enough to counteract shear
41,54,56forces in the functionally more important knee angles near extension, and second,
whether reflex activation of the hamstrings during abrupt perturbations of the knee is fast enough
57,58to develop tension in time with the peak external destabilizing moment.
Considering the development of the properly directed stabilizing force, studies on
55,59 54,60 53,61,62cadavers, animals, and mathematical models support that beyond 30 degrees of
knee flexion, the posteriorly directed vector of hamstring force becomes adequate in stabilizing=
the A CL deficient knee (Fig. 7-5). I n addition, it should not be underestimated that even when the
line of pool of the hamstrings is inefficient, co-contraction could increase joint stability due to
63joint compression and widening of the pressure distribution along the articular surfaces of the
64knee. A dditionally, it has been reported that the hamstrings cause greater stiffness to the A CL
65deficient knee than they do to the intact knee.
FIG. 7-5 As the knee flexes from A to B, the anti-shear vector of the
hamstring force (solid line) increases.
Regarding the question of the timely activation of the hamstrings, an overfocus on their reflex
66–68latency of 40 to 50 ms, which is a medium latency response, may be misleading in regard to
their efficacy to prevent instability. Growing evidence in the literature supports the development
12–16of preprogrammed compensatory muscle activation strategies. These strategies suggest that
subtle electrophysiological modifications of the subjects are implemented by deficient patients
after A CL injury to optimize shear force dissipation during injured knee loading. Hence,
feedforward mechanisms can be adopted that initiate hamstring co-contraction during the expectation
13,16,69,70of knee loading, not only as a reflex response. Therefore the hamstrings should be well
conditioned in order to have a greater potential to enhance knee stability.
Bracing in anterior cruciate ligament Deficient Patients: Is It
Effective?
The use of functional knee braces is a common practice for enhancing knee stability after rupture
of the A CL or reconstruction, with contradictory opinions about their importance in knee
71–73unloading. A favorable change of firing pa ern for the hamstrings was observed more often
69when A CL deficient patients performed single-leg landings wearing a brace and in skiers
74during periods of increased knee flexion. The greater biceps femoris activity was exhibited by
75the more unstable knees. Lam et al found that wearing a functional brace improved hamstring
reflex responses in A CL deficient knees after fatigue induced by repeated extension and flexion
against spring resistance. A lthough their protocol did not replicate a functional weight-bearing
condition, it gives a potentially useful message that bracing in A CL deficient knees may enhance
76protection. Wojtys et al showed that braces can decrease anterior tibial translation by a large
margin.
I n contrast, other findings have shown a slowing of hamstring muscle reaction times with
76 71,77bracing or decreased activation.