A Thesis entitled
Influence of Externally Applied Moments and Loads on Knee Kinematics:
A Cadaveric Study of Single- and Multi-Axis Loading of the Knee by
Richard C. Ditto
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Bioengineering
Vijay K. Goel, Ph.D., Committee Chair
Constantine K. Demetropoulos, Ph.D., Committee Member
Scott C. Molitor, Ph.D., Committee Member
Patricia R. Komuniecki, Ph.D., Dean
College of Graduate Studies
The University of Toledo
May 2013

Copyright 2013, Richard C. Ditto
This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author.

An Abstract of
Influence of Externally Applied Moments and Loads on Knee Kinematics:
A Cadaveric Study of Single- and Multi-Axis Loading of the Knee by
Richard C. Ditto
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Bioengineering
The University of Toledo
May 2013
Anterior cruciate ligament injuries are severe sports injuries which tend to occur in younger populations. These injuries are quite prevalent, affecting 1 in 3000 Americans. Studies have shown female athletes are two-to-eight times more susceptible to
ACL injuries than their male counterparts. ACL injuries are devastating to young athletes and often require a year of rehabilitation and pose a significantly greater risk for developing knee osteoarthritis. Many advances have been made with regard to surgical instrumentation and techniques, as well as rehabilitation programs, but none of these improvements have been proven to reduce the odds of developing osteoarthritis after ACL injury. The aims of the current study were to evaluate cadaveric knee kinematics to better understand ACL injury modalities.
In this study, a total of 18 cadaveric knee specimens (age 44 ± 8 years, 10 female and
8 male, 10 right and 8 left limbs) were tested under 65 loading conditions with and without Tekscan digital pressure sensors inserted between the tibial plateau and the meniscus. The tests were performed on a force couple testing system (FCTS) with simulated quadriceps (300 N) and hamstrings (180 N) muscle loads along with a joint compressive force (150 N). Similar trends were observed between knee kinematics obtained from this study and results obtained from previous studies. No significant iii

differences in knee kinematics were observed between the specimens with and without
Tekscan sensors. This study suggests the FCTS is a validated method for investigating in vitro knee kinematics and biomechanics.
iv

This thesis, along with any engineering accomplishment in my life, is dedicated to the memory of Alex Merlino, a great friend who possessed a tremendous engineering mind. We know you’re watching over us, Alex, and words can’t describe how much we all miss you.

I would like to sincerely thank my co-advisors, Dr.
Vijay Goel and Dr.
Dean
Demetropoulos, for their great advice and continual support throughout my time with The University of Toledo. During my short stint at Toledo, Dr. Goel’s door was always open and he was always willing to impart useful wisdom from his years as an expert in the orthopedic and spine realms. I’m gratefully indebted to Dr.
Demetropoulos for providing me the opportunity to participate on this project. I’d also like to thank Dean for the countless hours he spent in the lab with his graduate students.
I’d also like to thank Ata Kiapour for his untiring efforts in Matlab programming, data analysis, and manual labor. I truly had a blast working with you Ata, and I hope we can collaborate on future projects later in life.
I’d also like to thank the rest of the research team. To Dr. Tim Hewett, Dr. Carmen
Quatmann, and Sam Wordeman - Thanks for doing the ground work of this project and allowing me to play a role in the cadaveric portion of the research. I’d also like to thank Dr. Jason Levine for his presence on my committee and his willingness to participate with the study.
Finally, I’d like to thank my parents and sister for the endless amounts of encouragement and support they’ve shown throughout my life. I’m so blessed to be part of such a tight knit family full of love, good looks, and intelligence.
vi

Abstract
Acknowledgments
Contents
List of Tables
List of Figures
List of Abbreviations xiii xvi
1 Introduction
1.1
Knee Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2
ACL Injury Risk Factors . . . . . . . . . . . . . . . . . . . . . . . . .
1.3
ACL Injury Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . .
1.4
Treatment Options for ACL Injuries . . . . . . . . . . . . . . . . . . .
1.4.1
Conservative Treatment . . . . . . . . . . . . . . . . . . . . .
1.4.2
Surgical Treatment . . . . . . . . . . . . . . . . . . . . . . . .
1.4.2.1
Surgical Approaches . . . . . . . . . . . . . . . . . .
1.4.2.2
Graft Selection . . . . . . . . . . . . . . . . . . . . .
10
1.4.2.3
Surgical Instrumentation . . . . . . . . . . . . . . . .
12
1.5
Overview of Thesis Study . . . . . . . . . . . . . . . . . . . . . . . .
19
7
7
7
7
5
6
1
1 vii xi iii vi vii

2 Literature Review 20
2.1
ACL Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
2.2
Methods Used to Study ACL Injuries . . . . . . . . . . . . . . . . . .
21
2.2.1
In Vivo Studies . . . . . . . . . . . . . . . . . . . . . . . . . .
21
2.2.2
Video Analysis Studies . . . . . . . . . . . . . . . . . . . . . .
22
2.2.3
Physical Exam Studies . . . . . . . . . . . . . . . . . . . . . .
22
2.2.4
Mathematical Modeling Studies . . . . . . . . . . . . . . . . .
23
2.2.5
Cadaveric Studies . . . . . . . . . . . . . . . . . . . . . . . . .
24
2.2.5.1
Kinematics After Serial Dissections . . . . . . . . . .
24
2.2.6
Robotic Testing Systems . . . . . . . . . . . . . . . . . . . . .
25
2.3
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
3 Methods and Materials 29
3.1
Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . . . .
29
3.2
Test Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
3.3
Loading Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
3.4
Data Acquisition, Processing and Analysis . . . . . . . . . . . . . . .
34
4 Results 36
4.1
Kinematics Under Tibial Translation Loads and Rotatory Moments .
36
4.1.1
One-Plane Loading Scenarios . . . . . . . . . . . . . . . . . .
37
4.1.1.1
Anterior/Posterior Tibial Shear . . . . . . . . . . . .
37
4.1.1.2
Internal/External Tibial Rotation . . . . . . . . . . .
37
4.1.1.3
Varus/Valgus Tibial Rotation . . . . . . . . . . . . .
38
4.1.2
Two-Plane Loading Scenarios . . . . . . . . . . . . . . . . . .
38
4.1.2.1
A-P Tib Shear + I-E Tib Rotation . . . . . . . . . .
38
4.1.2.2
A-P Tib Shear + V-V Tib Rotation . . . . . . . . .
39
4.1.2.3
I-E Tib Rotation + 7.5 Nm V-V Tib Rotation . . . .
39 viii

4.1.2.4
I-E Tib Rotation + 15 Nm V-V Tib Rotation . . . .
39
4.1.3
Three-Plane Loading Scenarios . . . . . . . . . . . . . . . . .
40
4.1.3.1
A-P Tib Shear + I-E Tib Rotation + 7.5 Nm V-V Tib
Rotation . . . . . . . . . . . . . . . . . . . . . . . . .
40
4.1.3.2
A-P Tib Shear + I-E Tib Rotation + 15 Nm V-V Tib
Rotation . . . . . . . . . . . . . . . . . . . . . . . . .
41
4.2
Effect of Tekscan Insertion . . . . . . . . . . . . . . . . . . . . . . . .
41
4.3
In Vitro Kinematic Data Validation . . . . . . . . . . . . . . . . . . .
42
4.3.1
FCTS vs Robotic Testing Systems . . . . . . . . . . . . . . . .
42
4.3.2
Serial Dissection - Manually Applied Loads . . . . . . . . . . .
43
4.3.3
Robotic Testing - Pure Anterior Shear and Combined Valgus with Internal Rotation . . . . . . . . . . . . . . . . . . . . . .
44
4.3.4
Robotic Testing - Effect of Passive Muscle Loads . . . . . . .
45
4.3.5
Robotic Testing - Effect of Posterior Shear Combined with External Rotation . . . . . . . . . . . . . . . . . . . . . . . . . .
46
5 Analysis and Discussion 48
5.1
Maximum In Vitro Tibial Translations and Rotations . . . . . . . . .
48
5.1.1
Anterior Tibial Translation . . . . . . . . . . . . . . . . . . . .
49
5.1.2
Posterior Tibial Translation . . . . . . . . . . . . . . . . . . .
51
5.1.3
Internal Tibial Rotation . . . . . . . . . . . . . . . . . . . . .
53
5.1.4
External Tibial Rotation . . . . . . . . . . . . . . . . . . . . .
55
5.1.5
Valgus Tibial Rotation . . . . . . . . . . . . . . . . . . . . . .
57
5.1.6
Varus Tibial Rotation . . . . . . . . . . . . . . . . . . . . . .
60
5.2
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
62
5.3
Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
63
References 64 ix

A In Vitro Loading Conditions 72
B In Vitro Kinematic Results 76
B.1 One-Plane: Ant/Post Tib Shear . . . . . . . . . . . . . . . . . . . . .
76
B.2 One-Plane: Int/Ext Tib Rot . . . . . . . . . . . . . . . . . . . . . . .
78
B.3 One-Plane: Var/Val Tib Rot . . . . . . . . . . . . . . . . . . . . . . .
80
B.4 Two-Plane: A-P Tib Shear & I-E Tib Rot . . . . . . . . . . . . . . .
82
B.5 Two-Plane: A-P Tib Shear & V-V Tib Rot . . . . . . . . . . . . . . .
84
B.6 Two-Plane: I-E Tib Rot & V-V Tib Rot . . . . . . . . . . . . . . . .
86
B.6.1
7.5 Nm Valgus . . . . . . . . . . . . . . . . . . . . . . . . . .
86
B.6.2
15.0 Nm Valgus . . . . . . . . . . . . . . . . . . . . . . . . . .
88
B.7 Three-Plane: A-P Tib Shear, I-E Tib Rot & V-V Tib Rot . . . . . .
90
B.7.1
7.5 Nm Valgus . . . . . . . . . . . . . . . . . . . . . . . . . .
90
B.7.2
15.0 Nm Valgus . . . . . . . . . . . . . . . . . . . . . . . . . .
92 x

2.1
Markolf’s Data [2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
2.2
Yamamoto’s Data [51] . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
2.3
Li’s Data [52] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
2.4
Harner’s Data [53] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
4.1
Markolf’s Data [2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
4.2
Demetropoulos’s Data . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
4.3
Yamamoto’s Data [51] . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
4.4
Demetropoulos’s Data . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
4.5
Li’s Data [52] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
46
4.6
Demetropoulos’s Data . . . . . . . . . . . . . . . . . . . . . . . . . . . .
46
4.7
Harner’s Data [53] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
4.8
Demetropoulos’s Data . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
5.1
Anterior Tibial Translation Data Under Four Loading Conditions . . . .
49
5.2
Posterior Tibial Translation Data Under Four Loading Conditions . . .
52
5.3
Internal Tibial Rotation Data Under Four Loading Conditions . . . . .
54
5.4
External Tibial Rotation Data Under Four Loading Conditions . . . . .
56
5.5
Valgus Tibial Rotation Data Under Five Loading Conditions . . . . . .
58
5.6
Varus Tibial Rotation Data Under Five Loading Conditions . . . . . . .
61
A.1 List of One-Plane Loading Conditions . . . . . . . . . . . . . . . . . . .
73
A.2 List of Two-Plane Loading Conditions . . . . . . . . . . . . . . . . . . .
74 xi

A.3 List of Three-Plane Loading Conditions . . . . . . . . . . . . . . . . . .
75 xii

1-1 Anterior view of knee anatomy . . . . . . . . . . . . . . . . . . . . . . .
1-2 Bahr and Krosshaug - ACL Injury Causation . . . . . . . . . . . . . . .
1-3 Tunnel Drilling Techniques . . . . . . . . . . . . . . . . . . . . . . . . . .
1-4 Single & Double Bundle Reconstruction . . . . . . . . . . . . . . . . . .
1-5 BPTB Graft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
1-6 DLSTG Hamstring Graft . . . . . . . . . . . . . . . . . . . . . . . . . .
11
1-7 Femoral Fixation: Button-Like Suspensory Devices . . . . . . . . . . . .
13
1-8 Femoral Fixation: Cross Pin Suspensory Devices . . . . . . . . . . . . .
14
1-9 ACL Graft Fixation: Interference Screws . . . . . . . . . . . . . . . . . .
15
1-10 Cayenne Medical R AperFix R Device . . . . . . . . . . . . . . . . . . . .
16
1-11 Tibial Distal Fixation Devices . . . . . . . . . . . . . . . . . . . . . . . .
17
1-12 Arthrex R RetroScrew R Aperture Interference Screw . . . . . . . . . . .
18
8
9
2
6
2-1 Physical Exam Methods . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
2-2 Robotic Testing System with Universal Force-Moment Sensor (UFS) . .
26
3-1 Schematic of custom external fixation frame [54] . . . . . . . . . . . . .
30
3-2 Schematic of Tekscan sensor, K-scan 4000 [54] . . . . . . . . . . . . . .
31
3-3 Six Degree-of-Freedom FCTS with a Lower Extremity Cadaveric Specimen 32
3-4 Schematic of Optotrak marker array [54] . . . . . . . . . . . . . . . . . .
33
4-1 Tekscan Versus Intact Kinematics . . . . . . . . . . . . . . . . . . . . . .
42
5-1 Anterior Tibial Translation Data Under Four Loading Conditions . . . .
50 xiii

5-2 Posterior Tibial Translation Data Under Four Loading Conditions . . .
52
5-3 Internal Tibial Rotation Data Under Four Loading Conditions . . . . .
54
5-4 External Tibial Rotation Data Under Four Loading Conditions . . . . .
56
5-5 Valgus Tibial Rotation Under Four Loading Conditions . . . . . . . . .
59
5-6 Valgus Tibial Rotation Data Under Four Loading Conditions . . . . . .
61
B-1 One-Plane: Ant/Post Tib Shear - Ant/Post Tib Translation . . . . . . .
76
B-2 One-Plane: Ant/Post Tib Shear - Int/Ext Tib Rotation . . . . . . . . .
77
B-3 One-Plane: Ant/Post Tib Shear - Var/Val Tib Rotation . . . . . . . . .
77
B-4 One-Plane: Int/Ext Rot - Ant/Post Tib Translation . . . . . . . . . . .
78
B-5 One-Plane: Int/Ext Rot - Int/Ext Tib Rotation . . . . . . . . . . . . .
79
B-6 One-Plane: Int/Ext Rot - Var/Val Tib Rotation . . . . . . . . . . . . .
79
B-7 One-Plane: Var/Val Rot - Ant/Post Tib Translation . . . . . . . . . . .
80
B-8 One-Plane: Var/Val Rot - Int/Ext Tib Rotation . . . . . . . . . . . . .
81
B-9 One-Plane: Var/Val Rot - Var/Val Tib Rotation . . . . . . . . . . . . .
81
B-10 Two-Plane: Ant Shear + Int/Ext Rot - Ant/Post Tib Translation . . .
82
B-11 Two-Plane: Ant Shear + Int/Ext Rot - Int/Ext Tib Rotation . . . . . .
83
B-12 Two-Plane: Ant Shear + Int/Ext Rot - Var/Val Tib Rotation . . . . . .
83
B-13 Two-Plane: Ant Shear + Var/Val Rot - Ant/Post Tib Translation . . .
84
B-14 Two-Plane: Ant Shear + Var/Val Rot - Int/Ext Tib Rotation . . . . . .
85
B-15 Two-Plane: Ant Shear + Var/Val Rot - Var/Val Tib Rotation . . . . .
85
B-16 Two-Plane: Int/Ext Rot + 7.5 Nm Var/Val Rot - Ant/Post Tib Translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
86
B-17 Two-Plane: Int/Ext Rot + 7.5 Nm Var/Val Rot - Int/Ext Tib Rotation 87
B-18 Two-Plane: Int/Ext Rot + 7.5 Nm Var/Val Rot - Var/Val Tib Rotation 87
B-19 Two-Plane: Int/Ext Rot + 15 Nm Var/Val Rot - Ant/Post Tib Translation 88
B-20 Two-Plane: Int/Ext Rot + 15 Nm Var/Val Rot - Int/Ext Tib Rotation 89 xiv

B-21 Two-Plane: Int/Ext Rot + 15 Nm Var/Val Rot - Var/Val Tib Rotation 89
B-22 Three-Plane: Ant/Post Tib Translation . . . . . . . . . . . . . . . . . .
90
B-23 Three-Plane: Int/Ext Tib Rotation . . . . . . . . . . . . . . . . . . . .
91
B-24 Three-Plane: Var/Val Tib Rotation . . . . . . . . . . . . . . . . . . . .
91
B-25 Three-Plane: Ant/Post Tib Translation . . . . . . . . . . . . . . . . . .
92
B-26 Three-Plane: Int/Ext Tib Rotation . . . . . . . . . . . . . . . . . . . .
93
B-27 Three-Plane: Var/Val Tib Rotation . . . . . . . . . . . . . . . . . . . .
93 xv

3D . . . . . . . . . . . . . . . . . . . . Three-Dimensional
ACL . . . . . . . . . . . . . . . . . . . Anterior Cruciate Ligament
AL . . . . . . . . . . . . . . . . . . . . Anterolateral Bundle of the Posterior Cruciate Ligament
AM . . . . . . . . . . . . . . . . . . . Anteromedial Bundle of the Anterior Cruciate Ligament
Ant . . . . . . . . . . . . . . . . . . . Anterior
ATT . . . . . . . . . . . . . . . . . . Anterior Tibial Translation
BMI . . . . . . . . . . . . . . . . . . . Body Mass Index
BPTB . . . . . . . . . . . . . . . . . Bone-Patellar Tendon-Bone Graft
BTB . . . . . . . . . . . . . . . . . . Bone-Tendon-Bone Graft
Deg . . . . . . . . . . . . . . . . . . . Degrees
DLSTG . . . . . . . . . . . . . . . Double-Looped Semitendinosus and Gracilis dMCL . . . . . . . . . . . . . . . . . Deep Medial Collateral Ligament
EMG . . . . . . . . . . . . . . . . . . Electromyography
Ext . . . . . . . . . . . . . . . . . . . . External
FCTS . . . . . . . . . . . . . . . . . Force Couple Testing System
Ham . . . . . . . . . . . . . . . . . . Hamstrings
Int . . . . . . . . . . . . . . . . . . . . Internal irLED . . . . . . . . . . . . . . . . . Infrared Light Emitting Diode
LCL . . . . . . . . . . . . . . . . . . . Lateral Collateral Ligament
MCL . . . . . . . . . . . . . . . . . . Medial Collateral Ligament
MRI . . . . . . . . . . . . . . . . . . . Magnetic Resonance Imaging
PCL . . . . . . . . . . . . . . . . . . . Posterior Cruciate Ligament
PL . . . . . . . . . . . . . . . . . . . . Posterolateral Bundle of the Anterior Cruciate Ligament
PLC . . . . . . . . . . . . . . . . . . . Posterolateral Corner
PM . . . . . . . . . . . . . . . . . . . . Posteromedial Bundle of the Posterior Cruciate Ligament
Post . . . . . . . . . . . . . . . . . . . Posterior
PTT . . . . . . . . . . . . . . . . . . Posterior Tibial Translation
Quad . . . . . . . . . . . . . . . . . . Quadriceps
Rot . . . . . . . . . . . . . . . . . . . . Rotation sMCL . . . . . . . . . . . . . . . . . Superficial Medial Collateral Ligament
Trans . . . . . . . . . . . . . . . . . . Translation xvi

UFS . . . . . . . . . . . . . . . . . . . Universal Force Sensor
Val . . . . . . . . . . . . . . . . . . . . Valgus
Var . . . . . . . . . . . . . . . . . . . . Varus xvii

This chapter will provide some background information relevant to the study and a summary of key elements.
Among the topics discussed will be knee anatomy, knee biomechanics, anterior cruciate ligament (ACL) injury risk factors, ACL injury mechanisms, and current developments in ACL injury prevention programs. Finally, a comprehensive review of ACL injury treatment options will be reviewed, and the purpose and design of this study will be presented.
The knee is the largest joint in the human body and consists of four bones: the femur, tibia, fibula, and patella (Figure 1-1). There are three articulations which occur in the knee: 1) between the femur and tibia; 2) between the femur and patella; and 3) between the tibia and fibula. The femur and tibia are the main weight-bearing bones of the knee joint, which supports nearly the whole weight of the body. Because it must support such high loads, the articulating bony surfaces of the knee are covered with a layer of smooth hyaline cartilage with a very low coefficient of friction which enables the bones to move smoothly against one another. The meniscus, a fibrocartilage pad located between the articulating surfaces of the femur and tibia, cushions the interaction between the femur and tibia and also helps lubricate the knee joint [3].
1

The meniscus is comprised of two parts: 1) medial meniscus; and 2) lateral meniscus.
The medial meniscus is larger and less mobile than the lateral meniscus, and the two menisci are connected via the transverse ligament on the anterior side and the posterior meniscofemoral ligament on the posterior side.
Figure 1-1: Anterior view of knee anatomy
Although the patella and fibula do not bear much load, they each serve an important functional purpose. The patella is directly connected to the quadriceps muscles via the quadriceps tendon, and it serves to transmit force from the quadriceps muscle to the patellar tendon. The fibula is located on the lateral side of the tibia and provides a surface for lateral muscle and ligament attachment. These soft tissue structures play an important role in the transverse plane rotational stabilization of the human knee.
The knee joint is encapsulated by a thin, fibrous articular capsule which provides stability to the knee joint and seals the joint space. This capsule attaches to the tibia, patella, femur, and patellar ligament and is lined with the synovial membrane, which secretes synovial fluid. Synovial fluid, in conjunction with the hyaline cartilage
2

on the articulating surfaces of the femur and tibia, lubricates the joint and allows for smooth motion between the bones.
In addition to the bony structures of the knee joint, there are many soft tissue structures which provide stabilization and allow the joint to move through typical ranges of motion. There are four main ligaments which each play a critical role in the knee:
1) anterior cruciate ligament (ACL); 2) posterior cruciate ligament (PCL); 3) medial collateral ligament (MCL); and 4) lateral collateral ligament (LCL).
The ACL is composed of two bundles: 1) the anteromedial (AM) bundle; and 2) the posterolateral (PL) bundle. The ACL has a femoral insertion point on the posterolateral intercondylar fossa and is directed anteriorly, medially, and distally to its oval-shaped tibial insertion point, located at the anterior aspect of the medial tibial plateau [4]. Cadaveric studies conducted using serial dissection methods have estimated that approximately 85% of knee restraint in the sagittal plane is derived from the ACL [1, 2].
The PCL, which obliquely crosses the ACL within the synovium, also consists of two bundles: 1) the anterolateral (AL) bundle; and 2) the posteromedial (PM) bundle.
The PCL has a femoral insertion point on the anterolateral intercondylar fossa and is directed posteriorly, laterally, and distally to its tibial insertion point, located at the posterior intercondylar area of the tibial plateau. The PCL works synergistically with the ACL to restrain sagittal plane translation of the tibia relative to the femur, although it is mainly responsible for posterior translation [5].
The MCL is a broad, flat, membranous band originating from the medial femoral epicondyle and inserting medially on the tibia immediately below the adductor tubercle.
The MCL is typically divided into two layers: 1) the superficial medial collateral lig-
3

ament (sMCL); and 2) the deep medial collateral ligament (dMCL). The role of the
MCL in terms of joint stability is restraining the amount of medial knee joint opening in response to abduction loads, also called valgus loads.
The LCL is a rounded, more narrow ligament than the MCL, and connects the lateral epicondyle of the femur to the head of the fibula. Unlike the MCL, the LCL is not connected with either the capsular ligament or the lateral meniscus, which decreases its susceptibility to injury [6]. The role of the LCL in terms of joint stability is reinforcing the posterolateral corner (PLC) of the knee and restraining the knee in response to adduction loads [6, 7].
The musculature of the knee is also critical to its stability and functionality. The skeletal muscles which play the largest role in the knee joint are the hamstrings muscles, the quadriceps muscles, and the gastrocnemius muscle. There are three main hamstrings muscles: 1) biceps femoris; 2) semitendinosus; and 3) semimembranosus. The hamstrings originate from the tuberosity of the ischium and insert on the proximal tibia and fibula. The hamstrings muscles function as an antagonist to the quadriceps muscles and are responsible for knee flexion and hip extension.
There are four main quadriceps muscles: 1) rectus femoris; 2) vastus lateralis; 3) vastus medialis; and 4) vastus intermedius. The quadriceps muscles wrap around the patella and unite at the proximal patella to form the patellar tendon, which attaches the patella to the tibial tuberosity. The quadriceps muscles serve as an antagonist to the hamstrings muscles and are responsible for knee extension and hip flexion.
The gastrocnemius muscle is a very powerful superficial pennate muscle located in the posterior part of the lower leg. It originates from slightly above the articular surfaces of the medial and lateral femoral epicondyles and inserts on the calcaneus
4

bone where it forms the Achilles tendon. The gastrocnemius muscle is responsible for plantar flexing the foot at the ankle joint and flexing the leg at the knee joint.
Throughout the past twenty years, many studies have been conducted to investigate potential risk factors for ACL injury. Several studies have examined the correlation between anatomical and hormonal factors and ACL injury occurrence. Anatomical factors such as Q-angle (quadriceps femoral angle), body mass index (BMI), femoral intercondylar notch width, and ACL geometry have been the primary focus of this research [8, 9, 10]. Biomechanical risk factors such as altered muscle activation patterns and movements during pivoting, jumping, cutting, and pivoting have also been investigated [11].
Hormonal effects have also been studied as possible risk factors for ACL injury because hormonal differences between genders may help explain the gap in ACL injury prevalence between males and females [12, 13, 14]. Hormones might play a role in ligament loading properties, particularly on the molecular level where ligament synthesis and degradation is thought to be dependent on hormonal influences.
Epidemiologic studies have also been conducted to show the effect of Title IX of the
Education Assistance Act and the direct increase of adolescent female knee injuries
[15, 16, 17]. Before the passage of Title IX in 1972, the number of females participating in organized high school sports was estimated to be 320,000. That number has ballooned to over three million females participating in organized high school sports annually. With a much larger female population currently participating in athletics, the ACL injury prevalence has become much more apparent. Bahr and Krosshaug developed a comprehensive description of internal and external risk factors which play
5

Figure 1-2: Bahr and Krosshaug - ACL Injury Causation [18] a role in ACL injuries (Figure 1-2).
Most ACL injuries occur via non-contact mechanisms during movements such as rapid deceleration or lateral pivoting [19]. Studies coupling video analysis with biomechanical data suggest that when lower extremity abduction loads are combined with high risk movements, there may be increased ACL strain and a higher risk of ligament injury [20, 21].
The literature is populated with studies indicating different scenarios which subject the ACL to high forces [11, 22]. Although these scenarios and test setups may vary, there is evidence which suggest ACL injuries may occur under multi-planar loading conditions in the sagittal, transverse, and coronal plane [23]. Understanding which
6

loading conditions are most likely to cause ACL rupture is quite complex and may change for each person based on the hormonal and anatomical risk factors discussed earlier.
Surgery may not be necessary to treat grade I or II ACL injuries, as long as the patients’ knee joints do not exhibit significant instability [24]. Patients must be endure a well-planned rehabilitation regime to return to normal preinjury activity levels, which should last approximately twenty weeks. Bracing should also be considered to add stability to the injured knee. If patients continue to experience knee instability or endure second knee injuries, surgical intervention may be required.
There is agreement throughout the medical community that the knee should be ’quiet’ at the time of ACL reconstruction to minimize the risk of post-operative arthrofibrosis
[25]. At the time of surgical intervention, the knee should have minimal effusion, good quadriceps control, a normal gait, and the ability for full hyperextension. There are many schools of thought in the realm of ACL reconstruction, especially with regard to surgical approaches, graft selection, and surgical instrumentation. A comprehensive description of current solutions will be presented.
1.4.2.1
Surgical Approaches
The most vital factor in determining the efficacy of an ACL reconstruction is the anatomic placement of bone tunnels. In an ability to recreate the native anatomy,
7

there are two main techniques used to create anatomical insertion points for the ACL graft material: 1) the transtibial technique; and 2) the anteromedial portal technique
(Figure 1-3 ).
Transtibial Versus Anteromedial Portal Technique
When utilizing a transtibial technique, the surgeon drills the femoral bone tunnel through the tibial bone tunnel [25]. The benefit of drilling the femoral tunnel transtibially is reproducibility. As long as the tibial bone tunnel is properly drilled, the surgeon should be able to access the femoral insertion point of the native ACL and place an anatomic femoral tunnel. In some cases, the intercondylar notch may need to be widened to access the femoral insertion of the native ACL. The main disadvantage of the transtibial technique is the risk that the femoral tunnel will be drilled too vertically, leading to a non-anatomic repair.
Figure 1-3: (A) Transtibial Technique and (B) Anteromedial Portal
Technique
8

There has been a relatively recent movement to anteromedial portal techniques, in which the femoral tunnel is fashioned independent of the tibial tunnel through the anteromedial portal [25]. The benefit of this technique is that the location of the femoral tunnel is completely dependent upon the surgeon’s preference and ability.
This benefit is also a subsequent drawback.
Less experienced surgeons may not approximate the location of the femoral bone tunnel appropriately, whereas proper use of an anatomic transtibial guide should position the femoral tunnel automatically with correct tibial tunnel placement.
Single Bundle Versus Double Bundle Reconstruction
Figure 1-4: (A) Single Bundle and (B) Double Bundle Reconstruction
The native ACL is comprised of two bundles, the anteromedial (AM) bundle and the posterolateral (PL) bundle. Growing interest in performing a more anatomic ACL reconstruction has led to the development of double bundle ACL reconstructions, in which two tibial holes and two femoral holes are drilled to mimic the bundles of the intact ACL (Figure 1-4 ). There seem to be obvious benefits to the double bundle technique’s anatomical argument, but there are contradicting reports in the literature
9

about double bundle repair benefits in terms of kinematics and healing. There are several drawbacks of the double bundle technique: 1) surgical time; 2) difficult tunnel placement; and 3) additional cost of surgical implants/grafts.
1.4.2.2
Graft Selection
Bone-Patellar Tendon-Bone (BPTB) Graft
Bone-patellar tendon-bone (BPTB) autograft (Figure 1-5) used to be the “gold standard” graft choice for ACL reconstruction, but that may no longer be the case with the emergence of soft tissue grafts [25]. BPTB grafts provide better healing than their soft tissue counterparts because they promote bone-to-bone contact, whereas soft tissue grafts promote bone-to-tissue contact.
Figure 1-5: BPTB Graft
10

Soft Tissue Graft
The use of soft tissue grafts such as hamstrings tendons has become more prevalent in recent years (Figure 1-6). Double-looped semitendinosus and gracilis (DLSTG) grafts are the most commonly utilized soft tissue choice for ACL reconstruction.
These grafts provide slower initial healing, but only require a single incision and have been shown to have a lower incidence of postoperative anterior knee pain [26].
Figure 1-6: DLSTG Hamstring Graft
11

Allograft Options
Ligament allotransplantation provides another graft option for ACL reconstruction procedures. Allograft ligaments may be bone-tendon-bone (BTB) grafts or soft tissue grafts harvested from the donor. The primary benefit of allograft solutions is the lack of donor site morbidity, which may decrease postoperative pain levels. As with all implantable materials, there is a chance of the host mounting an immune response against the allograft material, termed rejection. There is also a minor chance of disease transmission via allograft tissue. The risks of disease transmission are extremely low, and have been estimated to occur in between 1 in 173,000 to 1 in 1,000,000 allograft procedures [27].
1.4.2.3
Surgical Instrumentation
When the ACL is surgically reconstructed, bone tunnels are drilled in the tibia and femur and the replacement graft is fixated within those bone tunnels. Current fixation options will be briefly reviewed and discussed.
Femoral Fixation
Femoral Suspensory Fixation Devices
There are two main types of suspensory femoral fixation: 1) button-like; and 2) cross pins. Button-like fixations such as the Smith & Nephew R EndoButton
TM
, Arthrex R
RetroButton
TM
, and Biomet R Sports Medicine ToggleLoc
TM with ZipLoop
TM
Technology (Figure 1-7) rely on an implantable button resting on the lateral femoral cortex to suspend the graft in the bone tunnel. The benefit of these devices is they are easy to implant and revise in the event of a graft failure. Button-like suspensory devices
12

have been criticized for bungee-like effects and slippage, but graft displacement is minimal when the implant properly engages the femoral cortex [28].
Figure 1-7: Button-Like Suspensory Devices:
(A) Smith & Nephew R EndoButton
TM
(B) Arthrex R RetroButton
TM
(C) Biomet R Sports Medicine ToggleLoc
TM
Technology with ZipLoop
TM
Cross pin devices such as the Arthrex R TransFix
TM
, Depuy Mitek R RigidFix R , and
Biomet R Sports Medicine AXL
TM
Cannulated Cross Pin and Bone Mulch
TM
Screw
(Figure 1-8) rely on the graft to be looped over the cross pin, which is inserted via a Ushaped guide and a transverse femoral tunnel. The benefit of these cross pin devices is their rigidity and overall strength; however, in some cases it may be difficult to properly loop the graft over the cross pin intra-operatively.
13

Figure 1-8: Cross Pin Suspensory Devices:
(A) Arthrex R TransFix
TM
(B) Depuy Mitek
(C) Biomet R
R RigidFix R
Sports Medicine Bone Mulch
TM
(D) Biomet R Sports Medicine AXL
TM
Screw
Cannulated Cross Pin
14

Femoral Aperture Fixation Devices
There is a school of thought that suspensory femoral fixation methods allow too much distance between graft fixation points, which may lead to increased knee laxity under normal loading conditions. To achieve aperture fixation toward the femoral insertion point of the native ACL, surgeons typically utilize interference screws (Figure 1-9) which offer graft compression in the bone tunnel. The benefits of these devices are ease of use and graft compression against the cancellous bone in the tunnel. The argument against interference screws is that the threads of the screws cut into the graft and could actually inhibit the biologic healing of the graft and potentially cause the implant-graft construct to fail at lower loads.
Figure 1-9: (A) Titanium and (B) Polylactic Acid (PLA) Interference Screws
15

In recent years, several hybrid technologies have been developed which combine the perks of both suspensory devices and aperture fixation methods. The AperFix R , made by Cayenne Medical R (Figure 1-10), is an aperture fixation device where the graft is looped through the implant. Wings on the implant expand within the bone tunnel, fixing the graft within the bone tunnel near the insertion site of the native
ACL. Further clinical studies on patient outcomes will be required to determine the long-term efficacy of this device.
Figure 1-10: Cayenne Medical R AperFix R Device
16

Tibial Fixation
Tibial Distal Fixation Devices
Most ACL reconstructions are performed with distal fixation options on the tibial side [29]. This is because distal fixation methods are easy to use and do not require retrograde drilling in the tibial plateau like aperture fixation devices. Standard interference screws are often used because they are relatively inexpensive compared to newer implants and instrument systems like the Depuy Mitek R IntraFix
TM
, the
Arthrex R GraftBolt R , and the Biomet R Sports Medicine TunneLoc
TM
(Figure 1-11).
Figure 1-11: Tibial Distal Fixation Devices:
(A) Depuy Mitek R IntraFix
TM
(B) Arthrex R GraftBolt
TM
(C) Biomet R Sports Medicine TunneLoc
TM
Fixation Device
The IntraFix
TM and GraftBolt R implants are classified as two-piece sheath-and-screw systems, in which a sheath is first inserted into the tibial tunnel with the graft circumferentially distributed around its diameter. Next, a screw is inserted to expand the
17

sheath and compress the graft against the walls of the tibial bone tunnel. Biomet R
Sports Medicine’s TunneLoc
TM implant and instrument system is classified as a tibial nail system, which is inserted by impacting an oversized nail with the graft circumferentially distributed around its diameter into the tibial bone tunnel. The TunneLoc
TM insertion tool is the first of its kind to utilize a graft tensioning instrument, which allows the surgeon to apply a determined amount of tension to the graft before implant insertion. This tension removes the creep from the viscoelastic ACL graft and provides satisfactory intraoperative stiffness. Long-term clinical studies will need to be conducted to determine the efficacy of these newer distal fixation devices, but this sector of the ACL reconstruction market looks very promising.
Tibial Aperture Fixation Devices
Aperture fixation devices are also used for tibial fixation during ACL reconstruction.
The goal of these devices is to fix the graft near the tibial footprint of the native ACL.
The most common device for this type of fixation is a reverse threaded interference screw which is inserted into a pre-drilled retrograde hole made in the tibial plateau
(Figure 1-12). There is still concern with damaging the graft during this procedure, so care must be taken when orienting the implant.
Figure 1-12: Arthrex R RetroScrew R Aperture Interference Screw
18

In order to investigate ACL injury mechanisms in vitro , a force couple test system
(FCTS) was developed to control knee kinematics and apply loading scenarios to cadaveric specimens. The purpose of this thesis project was to validate the in vitro knee kinematics produced by the FCTS with other readily available data in the literature.
Two prevalent methods have previously been used to conduct in vitro knee kinematic experiments: 1) serial dissections; and 2) knee robotic systems. While all cadaveric models have limitations, these two types of systems have been crucial in developing the theory behind the FCTS.
The FCTS utilizes a system of pulleys and cables to apply a pure moment to the tibia about the center of rotation of the knee. It is this pure moment which flexes and extends the knee in the sagittal plane. Loads may be applied by hanging static weights to a custom fixture attached to the tibia to simulate in vivo loading conditions. If the knee kinematics produced by the FCTS are within the accepted range in the literature, the assumption may be made that the FCTS loads the knee and its soft tissue structures appropriately during flexion-extension cycles. Future studies may then be conducted to investigate variables such as ligament strain and pressure distribution between the femoral condyles and tibial plateau.
19

This chapter reviews the literature relating to anterior cruciate ligament (ACL) injuries and the role knee kinematics plays in these injuries. A comprehensive discussion of kinematic studies will be presented, and relevant data utilized for validating the model used in this study will be discussed.
Anterior cruciate ligament injuries are severe sports injuries which tend to occur in younger populations. These injuries are quite prevalent, affecting 1 in 3000 Americans
[30]. Studies have shown female athletes are two-to-eight times more susceptible to
ACL injuries than their male counterparts [15]. ACL injuries are devastating to young athletes and often require a year of rehabilitation and a significantly greater risk for developing knee osteoarthritis [31]. Many advances have been made with regard to surgical instrumentation and techniques, as well as rehabilitation programs, but none of these improvements have been proven to reduce the odds of developing osteoarthritis after ACL injury [32, 33].
The knee pain and instability associated with ACL injuries is also accompanied by a financial burden.
Assuming a cost of $17,000 per patient for surgery and the
20

subsequent rehabilitation, the approximate cost for ACL treatment in the United
States is $1.7 billion per year [17]. Development of an effective ACL injury prevention program would provide young athletes the chance to participate in sports and avoid the long-term onset of knee osteoarthritis.
Using laboratory methods such as EMG and motion analysis, researchers can study high risk movements which may occur during ACL injury. These studies do not actually replicate ACL injuries, but they provide insight into the kinematics and net kinetics at the knee joint during specific movements designed to mimic those which occur during injury. Several in vivo studies have been conducted to examine the differences between males and females during high risk movements to determine possible mechanisms of ACL injury [20, 34, 35, 36].
In a review article by Hewett et al., extrinsic and intrinsic mechanisms of ACL injury were investigated [11]. Extrinsic factors such as the effects of bracing, shoe-surface interaction, and contact versus noncontact injuries were reviewed. Intrinsic factors such as anatomical differences, hormonal differences, and neuromuscular activities were also reviewed. These intrinsic factors play a strong role in controlling in vivo knee kinematics. While there are many contradicting reports on exactly how these factors correlate with ACL injuries, they should be considered when analyzing any knee ligament injury.
21

Video analysis tools have shown that 70% of ACL injuries occur via non-contact mechanisms [37, 38, 39]. These mechanisms typically involve high risk movements such as lateral cuts, pivoting motions, and sudden decelerations. While these studies provide useful evidence on a macro-scale, it is difficult to estimate joint kinematics from uncalibrated video systems. Without proper kinematics, it is impossible to quantify the kinetics and in vivo loads on the knee structures during the ACL injury.
Physical exam tests such as Lachman’s, anterior drawer, and the pivot shift test are used to determine the stabilizing effect of the intact ACL versus the ACL-deficient knee [40, 41]. Knee arthrometers may be used to quantify ligament functionality and integrity [42].
Figure 2-1: Physical Exam Methods:
(A) Lachman Test
(B) KT Arthrometer R - MEDmetric R Corporation
22

Clinical imaging has also been used in conjunction with physical exam studies. Radiography, fluoroscopy, and magnetic resonance imaging (MRI) have been employed in vivo to study knee injury mechanisms. These imaging modalities have demonstrated that the femoral intercondylar notch width and tibial plateau slope may correlate to ACL injuries [43]. Clinical imaging has also demonstrated that bone bruises of the lateral femoral condyle or posterolateral portions of the tibial plateau are often present after ACL injury. Research has been performed to speculate relationships between bruise location and pattern and ACL injury mechanisms [44, 45]. These studies are merely speculations since it is impossible to determine whether the bone bruises occurred before, during, or after ACL injury.
Mathematical modeling is a useful tool in examining internal joint biomechanics. In these studies, geometric models are developed and in vivo and/or in vitro biomechanical data is entered into the model to analyze kinematics and kinetics during quasi-static and dynamic movements [46, 47, 48].
The computational models in these studies vary in terms of complexity of knee ligaments. Some studies employed one-dimensional modeling, which can predict some joint kinematics, but this type of modeling does not take into account the threedimensional stresses and strains occurring throughout the ligaments [49]. Another option is to utilize three-dimensional knee ligament modeling; however, it is quite challenging to develop and validate these models [50]. Because it is difficult to develop three-dimensional ligament models, most studies utilize one-dimensional ligaments which are easier to validate with in vivo or in vitro data.
23

Cadaveric studies have been used extensively to explore knee anatomy and biomechanics, including knee ligament functionality and injury mechanisms. These studies have ranged from experiments on knee kinematics after serial dissections to robotic testing which simulates dynamic movements. Cadaveric studies are limited because they do not necessarily reflect in vivo kinematics and kinetics; however, they are useful in determining the passive biomechanical characteristics of knee structures.
2.2.5.1
Kinematics After Serial Dissections
A cadaveric study by Markolf et al. evaluated the total knee joint laxity for anteriorposterior tibiofemoral translation, internal-external rotational laxity, and varus-valgus rotational laxity at 0, 20, 45, 90, and 135 degrees of knee flexion [2]. In this study, there were three loading scenarios applied to the tibia near the tibial tubercle. First, an isolated 100 N anterior shear force and an isolated 100 N posterior shear force were applied. Second, an 8 Nm varus and valgus rotation moment was applied. Third, an 8
Nm internal and external rotation moments was applied to each specimen. Table 4.1
contains the kinematic data for intact knees at different flexion angles under the given loading conditions. This study was the first to quantify the stiffness and laxity contributions of different knee structures, and it provides intact knee kinematics which will validate the force couple testing system (FCTS) discussed later in this thesis.
Another important cadaveric study by Butler et al. evaluated the ligamentous restraints to anterior-posterior drawer in the human knee and determined the ACL is the responsible for approximately 85% of the restraint in anterior-posterior displacement of the human knee [1]. This number was calculated by randomizing the order
24

Table 2.1: Markolf’s Data [2]
Knee Flexion A-P Tibial Disp Var-Val Bending Tibial Torsion
Angle (Degrees) Laxity (mm) Laxity (Degrees) Laxity (Degrees)
0
◦
10
◦
20
◦
45
◦
2.0
4.8
± 2.0
3.9
±
—
±
0.5
2.5
1.9
± 1.7
4.5
± 1.9
5.4
6.0
±
±
2.1
2.4
10.1
± 4.0
19.5
± 4.9
24.5
26.7
±
±
4.9
5.8
ligaments were dissected and measuring the effect removing each ligament caused on sagittal plane knee kinematics. Since this study only conducted testing in the sagittal plane, its kinematic data will not be used to validate the force couple testing system
(FCTS) discussed later in this thesis.
In recent years, robotic testing systems have been useful in recreating approximate knee kinematics in cadaveric models. These systems utilize a universal force-moment sensor (UFS) and a six degree-of-freedom robot to move specimens through flexionextension cycles. The main limitation of these test apparatuses is that the knee kinematics they reproduce are approximations. Figure 2-2 depicts a standard knee robotic testing system. Notice the tibia is severed mid-shaft and connected directly to the UFS and may only move in conjunction with the robot. While the robot has six degrees of free motion, the tibia of the specimen does not possess six degrees of freedom since it is fixed at the UFS. Nevertheless, these types of robotic systems have provided valuable evidence of in situ ligament forces and strains and continue to provide information regarding ACL injury mechanisms.
25

Figure 2-2: Robotic Testing System with Universal Force-Moment Sensor
(UFS)
A cadaveric study by Yamamoto et al. evaluated knee stability and graft function after ACL reconstruction and determined the kinematics of the intact knee under two external loading conditions: 1) 134 N anterior tibial load; and 2) combined rotatory loads of 10 Nm valgus and 5 Nm internal tibial torques [51]. Table 4.3 contains the kinematic data for intact knees at different flexion angles under the given loading conditions. Since this thesis focuses on reproducing intact knee kinematics, we will focus on Yamamoto’s data regarding intact knee kinematics.
A cadaveric study by Li et al. evaluated the importance of quadriceps and hamstring muscle loading on knee kinematics and in situ forces in the ACL and determined the kinematics of the intact knee under two passive muscle loading conditions: 1) isolated
200 N quadriceps load; and 2) combined 200 N quadriceps load and 80 N hamstrings load [52]. Table 4.5 contains the kinematic data for intact knees at different flexion angles under the two different passive muscle loading conditions.
26

Knee Flexion
Angle (Degrees)
0
◦
15
◦
30
◦
60
◦
90
◦
Table 2.2: Yamamoto’s Data [51]
134 N Anterior Shear
Tibial Load
Anterior Tibial
Translation (mm)
5.1
± 1.4
7.1
± 1.9
7.7
± 2.7
7.6
± 2.4
6.1
± 2.6
10 Nm Valgus and
5 Nm Internal Tibial Torque
Anterior Tibial
Translation(mm)
6.6
—
4.9
± 2.2
±
—
—
2.6
Internal Tibial
Rotation (Degrees)
15.3
18.1
—
±
±
—
—
6.5
7.1
Table 2.3: Li’s Data [52]
Flexion
Angle
0
15
30
◦
60
◦
90
◦
120
◦
◦
◦
Ant(+)/Post(-)
Tibial Trans. (mm)
Quad Quad/Ham
Lat(+)/Med(-)
Tibial Trans. (mm)
Quad Quad/Ham
— — —
— — —
5.3
± 2.1
4.3
± 1.5
2.4
± 1.3
—
— -1.2
—
± 0.7
-0.8
± 1.1
-2.0
± 1.4
—
—
—
—
—
—
—
—
-1.2
± 1.4
Int(+)/Ext(-)
Tibial Rot. (Deg)
Quad Quad/Ham
— —
— —
7.5
± 4.3
5.1
± 2.3
—
—
—
—
-1.2
± 2.1
-1.3
± 2.4
A cadaveric study by Harner et al. evaluated both isolated and combined posterior cruciate ligament (PCL) injuries [53]. In this study, intact knee kinematics were determined under three loading scenarios: 1) isolated 134 N posterior tibial load; 2) isolated 5 Nm external torque; and 3) combined 67 N posterior tibial load and 2.5
Nm external torque. Table 4.7 contains the kinematic data for intact knees at 30
◦ and 90
◦ of flexion.
27

Table 2.4: Harner’s Data [53]
67 N Posterior Shear Tibial Load and 2.5 Nm External Rotation
Knee Flexion Posterior Tibial External (Axial)
Angle (Degrees) Translation (mm) Rotation (deg)
30
◦
90
◦
4.8
4.7
±
±
2.6
1.1
9.2
10.1
±
±
3.4
2.7
Many methodological appraoches used to describe ACL injury mechanisms have been reviewed. These approaches include in vivo studies, video analysis, physical examinations like the Lachman’s and pivot shift test, mathematical modeling studies, and also in vitro cadaveric studies. None of these methodologies alone has provided strong results for the underlying mechanisms of non-contact ACL injuries, but the combination of all these approaches may provide useful clues to non-contact ACL injury mechanisms. The data from the cadaveric studies discussed in this literature review will be used to validate the kinematic data collected during the current study.
28

This chapter details the steps of the procedure for obtaining in vitro knee kinematic data. Explanations of the data processing protocol are also presented.
Eighteen fresh frozen cadaveric lower extremity specimens (age 44 ± 8 years, 10 female and 8 male, 10 right and 8 left limbs) were used. Specimens were originally excised at the hip joint with all muscular and ligamentous structures intact, and they were obtained from MedCure (Portland, OR) and Science Care (Phoenix, AZ).
An orthopedic surgeon screened all specimens to exclude those specimens with any evidence of prior surgery, abnormal joint laxity or significant joint pathology due to disease. Each specimen was sectioned at the mid-shaft of the femur, 30 cm proximal to the knee joint line, and potted in polyester resin. The quadriceps (rectus femoris) and hamstrings (semitendinosus and biceps femoris) tendons were isolated and sutured inside metal tendon grips to allow for the application of simulated passive muscle loads without slippage during loading.
A custom external fixation frame (Figure 3-1) was mounted anteriorly on the tibia using three tibial attachment screws and a threaded rod placed through the tibia in
29

Figure 3-1: Schematic of custom external fixation frame [54] the sagittal plane. The frame was comprised of two Ilizarov external fixator rings attached to two parallel vertical bars. Each of these bars were directly attached to one lightweight pulley, which served as an attachment point for four loading cables.
Since the location of the pulleys plays a large role in the kinematics produced by force couple testing, the center of each pulley was placed as close to the approximate center of rotation of the knee as possible. By properly positioning each pulley, the motion of the pulleys during testing was reduced.
After specimens endured the first set of loading conditions, the anterior horn of the medial and lateral meniscus was dissected away from the tibial plateau, and digital electronic pressure sensors (K-scan 4000, Tekscan, Boston, MA) (Figure 3-2) were placed into the medial and lateral compartments of the knee, below the menisci.
These sensors provide data regarding the pressure distribution of the tibio-femoral joint, and may assist in finite element model validation in later studies. Once the
30

Figure 3-2: Schematic of Tekscan sensor, K-scan 4000 [54]
Tekscan sensors were oriented properly in the joint, the previous loading profile was repeated on the same specimen.
A custom designed 6-Degree of Freedom Force Couple Testing System (FCTS) (Figure 3-3) was used to produce an unconstrained pure moment through servo-electric actuators (Parker Hannifin Corporation, Cleveland, Ohio) which drive a cable-pulley system. A system of lightweight, low-friction pulleys were used to load the knees through a pre-determined range of motion which consisted of approximately five degrees of hyperextension through slightly over ninety degrees of flexion. The application of unconstrained pure moments in a 6-degree of freedom testing system has been utilized extensively in spinal biomechanics and may be used to establish the passive response of other complex joints such as the knee, ankle, and elbow.
31

Figure 3-3: Six Degree-of-Freedom FCTS with a Lower Extremity Cadaveric
Specimen
When characterizing joint kinematics, it is critical to consider the native motion of the intact joint and compare that to the motion of the joint following surgery. By utilizing an FCTS system, the native geometry of the joint determines the kinematic response to a physiologic loading scenario. Many researchers in previous studies have devised sophisticated methods which attempt to reproduce physiologic motion under active control. These systems often include at least one universal force sensor(UFS) and may also include simulated muscle loads and contractions. Complex algorithmic approaches such as these are dependent on the response time of the system and require tuning to replicate physiologic motion using motion and load feedback. Even after physiologic loading is approximated, it is very technically challenging to simulate an unknown kinematic condition such as the insertion of implantation.
32

Simulated passive muscle loads were applied via a loading system located above the testing frame. This passive loading system consisted of an adjustable weight stack which applied a constant tension of 300 N to the quadriceps tendon and 180 N to the hamstrings tendon. These muscle loads stabilized the knee joint by providing compression across the tibio-femoral joint. Similar methods have been pursued in previous studies [52]. The loading pulleys were positioned to simulate the line of action of the quadriceps and hamstrings muscles.
Figure 3-4: Schematic of Optotrak marker array [54]
In order to measure knee kinematics, an Optotrak 3D motion tracking system (Northern Digital Corporation, Waterloo, Ontario, Canada) was used to track the motion of the femur, patella, and tibia with respect to the loading frame. Active irLED optical markers were rigidly attached to each bone, as well as the loading frame, to properly track relative motion in the testing space (Figures 3-4).
After all the optical markers and Tekscan (if necesary) were attached, the specimen was mounted on the FCTS and the muscle loads nad loading conditions were applied.
The suspended leg was then flexed and extended through the pre-determined range
33

of motion four times by applying a pure moment at the center of rotation of the knee joint. The first two cycles were performed to condition the specimen for the particular loading condition, while the third cycle was used for data collection. A fourth flexion-extension cycle was conducted to avoid artifacts which may have been caused by ending the test at the end of the third cycle.
Each specimen endured two sets of sixty-six randomized loading conditions. In the first set of loading conditions, the knee capsule was intact; however, the second set of loading conditions utilized digital electronic pressure sensors to determine the pressure distribution of the tibio-femoral joint. The insertion of these pressure sensors required release of the anterior horn of the lateral and medial menisci, which could affect knee kinematics. Kinematic data between the two sets of loading conditions will provide insight into the effect the insertion of pressure sensors had on knee kinematics.
The set of sixty-five randomized loading conditions consisted of various varus-valgus rotations, internal-external rotations, and anterior-posterior shear loads (Appendix
A).
An electronic trigger was used to synchronize data collection with the Tekscan and
Optotrak sytem, as well as the six-axis load cell located in the center of the testing frame. Data was collected for the duration of the four flexion-extension cycles at a sampling rate of 100 Hz. For this kinematic analysis, Tekscan data was not processed or analyzed; however, kinematic data was analyzed using Matlab (The MathWorks
Inc., Natick, MA).
34

The laxity profile of the knee was generated using the tibial Optotrak marker data to track the motion of the tibia with respect to the femur and the initial position of the femur in one translation and two rotations: anterior-posterior tibial translation, internal-external tibial rotation, and varus-valgus tibial rotation. The femur was fixed in the six-axis load cell in the center of the test frame, and the initial position of the tibia in 0 degrees of flexion was determined by the resting position of the tibia before the first test of the loading profile was conducted. Flexion angle of the knee was calculated by analyzing the sagittal plane position of the Optotrak markers on the tibia with respect to the initial location of the femur. Internal-external tibial rotation and varus-valgus tibial rotation were calculated by analyzing the position of the Optotrak markers on the tibia with respect to the initial location of the tibia.
In order to calculate anterior tibial translation, each test was compared to the the baseline kinematic test (0 N Anterior Shear/0 Nm Valgus Rotation/0 Nm Internal
Rotation) through the third extension-flexion cycle. Only sagittal plane coordinates were considered for this calculation. The Optotrak marker positions of the baseline test were projected onto the test being evaluated and the magnitudes of the vectors were subtracted to determine anterior tibial translation. During one planar loading conditions, anterior tibial translation values were fairly consistent between specimens, but two- and three- planar loading conditions resulted in standard deviations which were quite high. This issue will be addressed later in the results and discussion sections.
35

This chapter presents the results from the in vitro study described in the previous chapter. These results will compare the kinematic data collected in this study to the kinematic data of studies discussed in the literature review [2, 51, 52, 53]. In addition, kinematic data from the intact knees will be compared to that of the specimens with the Tekscan pressure sensors inserted into the tibio-femoral joints. The results include the range of motion and relative rotational motion of the tibia with respect to its initial position under each loading condition.
Figures associated with the in vitro results discussed in this section may be found in
Appendix B, located near the end of this thesis.
36

4.1.1.1
Anterior/Posterior Tibial Shear
The application of anterior-posterior tibial shear loads resulted in substantial anterior or posterior tibial translation at low flexion angles of 0 to 10 degrees (Figure B-1).
Greater anterior tibial shear loads translated to more anterior tibial translation at low flexion angles of 0 to 10 degrees, while greater posterior tibial shear loads resulted in more posterior tibial translation at similar flexion angles.
The application of one-plane anterior-posterior tibial shear loads resulted in minimal internal or external tibial rotation throughout the entire extension to flexion cycle
(Figure B-2). This series of loading conditions also resulted in minimal varus or valgus tibial rotation throughout the entire extension to flexion cycle (Figure B-3).
4.1.1.2
Internal/External Tibial Rotation
The application of internal-external tibial rotation moments resulted in substantial internal or external tibial rotation throughout the entire extension to flexion cycle
(Figure B-5). At lower flexion angles, tibial rotation values were greater than at flexion angles greater than 30 degrees. This is due to the fact that the rotation moments were applied relative to the global coordinate system, so internal rotation moments became valgus moments at higher flexion angles and external rotation moments became varus moments at higher flexion angles. This relationship may be seen by comparing Figure B-5 and Figure B-6.
Since the standard deviation of anterior tibial translation values was high throughout the study, it was difficult to determine the relationship between one-plane internalexternal tibial rotation moments and anterior tibial translation. The trends in the data suggest increasing external tibial rotation moments causes posterior tibal transla-
37

tion at low flexion angles from 0 to 30 degrees of flexion, while internal tibial rotation moments lead to slight anterior tibial translation at similar flexion angles (Figure
B-4).
4.1.1.3
Varus/Valgus Tibial Rotation
The application of one-plane varus-valgus tibial rotation moments resulted in minimal tibial rotation and translation at low flexion angles from 0 to 30 degrees. Examining the trends in Figure B-7 shows that varus-valgus tibial rotation moments do not effect anterior-posterior tibial translation at low flexion angles. Similarly, Figure B-8 and Figure B-9 show varus-valgus tibial rotation moments have little effect on tibial rotation at low flexion angles for internal-external rotation and varus-valgus rotation, respectively.
4.1.2.1
A-P Tib Shear + I-E Tib Rotation
The combination of an anterior tibial shear load with varying internal-external tibial rotation moments resulted in substantial anterior tibial translation and internalexternal tibial rotation (Figure B-10 and Figure B-11). While the anterior tibial translation data had a relatively high standard deviation, the trends in the figures seem to suggest higher internal rotation moments combined with anterior tibial shear loads result in greater anterior tibial translation. Conversely, the trends seem to suggest higher external rotation moments combined with anterior tibial shear loads result in greater posterior tibial translation.
38

4.1.2.2
A-P Tib Shear + V-V Tib Rotation
The combination of an anterior tibial shear load with varying valgus tibial rotation moments resulted in minimal changes in anterior tibial translation and internalexternal tibial rotation throughout the entire extension to flexion cycle (Figure B-13 and Figure B-14). Increasing valgus tibial rotation moments also caused minimal changes in varus-valgus tibial rotation at low flexion angles from 0 to 30 degrees. In deeper knee flexion, the anterior shear tibial load became a joint compressive force and the original joint compressive force become posterior tibial shear, which caused substantial valgus rotation (Figure B-15).
4.1.2.3
I-E Tib Rotation + 7.5 Nm V-V Tib Rotation
The combination of various internal tibial rotation moments with a constant 7.5 Nm valgus tibial rotation moment resulted in little anterior tibial translation at low flexion angles; however, the combination of external tibial rotation moments with the same valgus moment led to substantial posterior tibial translation (Figure B-16). Altering the internal-external tibial rotation moments under this two-plane loading scenario produces similar internal-tibial rotations as one-plane loading scenarios comprised of only internal-external tibial rotation moments (Figure B-17).
With regard to varus-valgus tibial rotation, there is little difference in tibial rotation between the groups at low flexion angles (Figure B-18). This is not the case at flexion angles greater than 15-20 degrees, where initially applied internal-external tibial rotation moments begin to serve as varus-valgus tibial rotation moments.
4.1.2.4
I-E Tib Rotation + 15 Nm V-V Tib Rotation
The combination of various internal-external tibial rotation moments with a constant
15 Nm valgus tibial rotation moment resulted in little anterior tibial translation at
39

low flexion angles. The trends in the data seem to suggest that the combination of valgus and internal tibial rotation moments leads to greater anterior tibial translation, while valgus and external tibial rotation leads to greater posterior tibial translation
(Figure B-19). Varying the internal-external tibial rotation moments under this twoplane loading scenario produces similar internal-tibial rotations as one-plane loading scenarios comprised of only internal-external tibial rotation moments (Figure B-20).
With regard to varus-valgus tibial rotation, there is little difference in tibial rotation between the groups at low flexion angles (Figure B-21). This is not the case at flexion angles greater than 15-20 degrees, where initially applied internal-external tibial rotation moments begin to serve as varus-valgus tibial rotation moments.
4.1.3.1
A-P Tib Shear + I-E Tib Rotation + 7.5 Nm V-V Tib Rotation
Three plane loading consisting of a consant anterior tibial shear load (134 N), a constant valgus tibial rotation moment (7.5 Nm), and varying internal-external tibial rotation moments (15 Nm internal to 15 Nm external) provided further insight into multi-planar knee kinematics. The trends in the data seem to suggest that higher interal tibial rotation moments lead to greater anterior tibial translation throughout the extension-to-flexion cycle, while higher external tibial rotation moments lead to greater posterior tibial translation throughout the same extension-to-flexion cycle
(Figure B-22).
In terms of internal-external tibial rotation, the application of internal tibial rotation moments lead to internal tibial rotation, and vice versa (Figure B-23). With regard to varus-valgus tibial rotation, the various internal-external tibial rotation moments do not play a large role at low flexion angles; however, these internal-external tibial
40

rotation moments begin to translate into varus-valgus tibial rotation moments at flexion angles greater than 15-20 degrees (Figure B-24).
4.1.3.2
A-P Tib Shear + I-E Tib Rotation + 15 Nm V-V Tib Rotation
Three plane loading consisting of a consant anterior tibial shear load (134 N), a constant valgus tibial rotation moment (15 Nm), and varying internal-external tibial rotation moments (15 Nm internal to 15 Nm external) provided further insight into multi-planar knee kinematics. The trends in the data seem to suggest that higher interal tibial rotation moments lead to greater anterior tibial translation throughout the extension-to-flexion cycle, while higher external tibial rotation moments lead to greater posterior tibial translation throughout the same extension-to-flexion cycle
(Figure B-25).
In terms of internal-external tibial rotation, the application of internal tibial rotation moments lead to internal tibial rotation, and vice versa (Figure B-26). With regard to varus-valgus tibial rotation, the various internal-external tibial rotation moments do not play a large role at low flexion angles; however, these internal-external tibial rotation moments begin to translate into varus-valgus tibial rotation moments at flexion angles greater than 15-20 degrees (Figure B-27).
There were no noteworthy differences between knee kinematics before and after
Tekscan insertion. Figure 4-1 shows the similarities between analogous tests. The minimal differences in kinematics between the specimens with and without Tekscan pressure film will allow the Tekscan data to be used in later experiments, specifically related to finite element analysis and ligament strain.
41

Figure 4-1: Tibial axial rotation angles (solid lines represent experiments without Tekscan and dotted lines represent analogous experiments with Tekscan)
This section will compare data from previous studies (serial dissection and robotic testing) with the results from the current FCTS study. Statistical analyses cannot be used to compare the following data sets because of differences in experiment design, including specimen selection and test apparatus utilization.
Before comparing results from the current study with previous literature, it is critical to consider the differences between the FCTS utilized in this study and the Robotic
(UFS) Systems used by others. When characterizing joint kinematics, it is critical to consider the native motion of the intact joint and compare that to the motion of the joint following surgery. By utilizing an unconstrained 6-degree of freedom FCTS
42

system, a pure moment is applied to the specimen using a system of lightweight, low-friction pulleys. Because the kinematics are determined by the native geometry of the joint, a passive kinematic response to physiologic loading may be determined.
Many researchers in previous studies have devised sophisticated methods which attempt to reproduce physiologic motion under active control. These systems often include at least one universal force sensor(UFS) and may also include simulated muscle loads and contractions. Complex algorithmic approaches such as these are dependent on the response time of the system and require tuning to replicate physiologic motion using motion and load feedback. Even after physiologic loading is approximated, it is very technically challenging to simulate an unknown kinematic condition such as the insertion of an implant. The constrained motion produced by robotic test systems, along with the complexity of algorithm development and validation, are a clear disadvantage for UFS systems compared to the Force Couple Test System (FCST) utlized in this study.
Markolf et al. conducted a cadaveric study to examine combined loading scenarios thought to generate high ligament forces. This study examined 14 specimens and investigated ACL forces at various flexion angles for an isolated anterior tibial shear load (100 N), and isolated valgus moment (29 Nm), an isolated varus moment (29
Nm), and a combined anterior tibial shear load (100 N) with an internal (8 Nm), external (8 Nm), valgus (29 Nm), and varus (29 Nm) moment.
The kinematic data collected in this study showed similar results for the 100 N anterior tibial shear load, as well as the 8 Nm internal and external tibial rotation. In these two categories, the reported cadaveric means (Tables 4.1 and 4.2) of the current study
43

Table 4.1: Markolf’s Data [2]
Knee Flexion A-P Tibial Disp Tibial Torsion
Angle (Degrees) Laxity (mm) Laxity (Degrees)
0
◦
10
◦
20
◦
2.0
±
—
0.5
4.8
± 2.0
10.1
9.5
24.5
±
±
±
4.0
4.9
4.9
Table 4.2: Demetropoulos’s Data
Knee Flexion A-P Tibial Disp Tibial Torsion
Angle (Degrees) Laxity (mm) Laxity (Degrees)
0
◦
10
◦
20
◦
1.6
0.7
-0.5
±
±
±
3.6
2.4
2.2
21.4
25.2
25.7
±
±
±
9.7
6.2
6.4
were within one standard deviation of Markolf’s data. The loading protocol in this study involved varus-valgus moments of up to 15 Nm, which cannot be adequately compared with Markolf’s 29 Nm varus-valgus moment.
Yamamoto et al. conducted a cadaveric study to investigate the effect of femoral tunnel placement during ACL reconstruction. This study examined 10 specimens and investigated knee kinematics and in situ ACL forces for intact and ACL-deficient knees, as well as two reconstruction methods. The intact knee kinematics from Yamamoto’s study (Table 4.3) compare favorably with the intact knee kinematics calculated in the current study (Table 4.4).
44

Knee Flexion
Angle (Degrees)
0
◦
15
◦
30
◦
Table 4.3: Yamamoto’s Data [51]
134 N Anterior Shear
Tibial Load
Anterior Tibial
Translation (mm)
5.1
± 1.4
7.1
± 1.9
7.7
± 2.7
5 Nm Internal Tibial Torque
Anterior Tibial
Translation(mm)
4.9
6.6
—
±
±
10 Nm Valgus and
2.2
2.6
Internal Tibial
Rotation (Degrees)
—
15.3
± 6.5
18.1
± 7.1
Knee Flexion
Angle (Degrees)
0
◦
15
◦
30
◦
Table 4.4: Demetropoulos’s Data
134 N Anterior Shear
Tibial Load
Anterior Tibial
Translation (mm)
1.6
± 3.6
0.3
± 1.9
-0.9
± 1.9
5 Nm Internal Tibial Torque
Anterior Tibial
Translation(mm)
2.5
4.6
6.5
±
±
±
7.5 Nm Valgus and
3.6
3.5
3.5
Internal Tibial
Rotation (Degrees)
5.9
± 4.8
6.7
± 5.1
4.9
± 5.6
There is a substantial difference in the anterior tibial translation values when 134
N anterior shear loads were applied in each study; however, this may be attributed to distinct differences in testing machines. Yamamoto’s test setup did not utilize passive muscle loads for the quadriceps (300 N) and the hamstrings (180 N) or a joint compressive force (150 N) like the current study. Another difference in the test machines is the application of loads. In Yamamoto’s study, external loads are applied on a local coordinate system, while the FCTS utilized in the current study applies external loads on a global coordinate system.
Li et al. conducted a cadaveric study to investigate the importance of quadriceps and hamstrings muscle loading on knee kinematics and in situ forces in the ACL. This
45

Flexion
Angle
0
15
30
◦
◦
◦
Table 4.5: Li’s Data [52]
Ant(+)/Post(-)
Tibial Trans. (mm)
Quad Quad/Ham
Int(+)/Ext(-)
Tibial Rot. (Deg)
Quad Quad/Ham
—
—
—
—
—
—
—
—
5.3
± 2.1
4.3
± 1.5
7.5
± 4.3
5.1
± 2.3
Table 4.6: Demetropoulos’s Data
Flexion Ant(+)/Post(-) Int(+)/Ext(-)
Angle Tibial Trans. (mm) Tibial Rot. (Deg)
Quad/Ham Quad/Ham
0
◦
15
◦
30
◦
0.6
1.9
4.4
±
±
±
4.3
4.6
5.4
2.2
4.4
6.9
±
±
±
3.8
5.0
6.2
study examined 10 specimens and determined intact knee kinematics without passive muscle loading, as well as with an isolated 200 N quadriceps load. An additional series of tests was conducted with an agonist 80 N hamstring load also. In the current study, passive muscle loads were applied throughout all testing, so comparing the current study’s data with that collected by Li et al. may shed light on the differences between the current study and other studies throughout the literature.
Harner at al. conducted a cadaveric study to investigate the relationship between poterolateral structure deficiency and graft failure in PCL reconstruction. This study
46

Table 4.7: Harner’s Data [53]
67 N Posterior Shear Tibial Load and 2.5 Nm External Rotation
Knee Flexion Posterior Tibial External (Axial)
Angle (Degrees) Translation (mm) Rotation (deg)
30
◦
4.8
± 2.6
9.2
± 3.4
Table 4.8: Demetropoulos’s Data
67 N Posterior Shear 5 Nm External Rotation
Knee Flexion PTT (mm) External (Axial) PTT (mm) External (Axial)
Angle (Degrees) Rotation (deg) Rotation (deg)
30
◦
3.1
± 4.6
-1.4
± 4.9
0.9
± 5.0
4.4
± 6.8
examined 10 specimens and investigated knee kinematics and in situ graft forces for combined posterior cruciate ligament and posterolateral structure deficiency. The intact knee kinematics from Harner’s study (Table 4.7) compare favorably with the intact knee kinematics calculated in the current study (Table 4.8).
Harner’s study utilized a combined loading profile consisting of a 67 N posterior shear tibial load and a 2.5 Nm external rotation moment. In the current study, this exact loading profile was not tested. Instead, it is possible to compare the results from two separate tests to Harner’s intact knee data. When a 67 N posterior tibial shear load was applied in the current study the results were within one standard deviation of Harner’s data with regard to posterior tibial translation. Similarly, when a 5 Nm external rotation moment was applied in the current study, it fell within one standard deviation of Harner’s data with regard to external rotation.
47

This chapter will attempt to explain the results of the in vitro study and draw comparisons and conclusions. It will also present some limitations for the study and opportunities for future work.
This section will attempt to determine the loading conditions which seemed to produce the greatest amount of kinematic translations and rotations in each of six directions: 1) anterior tibial translation; 2) posterior tibial translation; 3) internal tibial rotation; 4) external tibial rotation; 5) valgus tibial rotation; and 6) varus tibial rotation. There are several studies which suggest that combined loading mechanisms produce the highest amount of ACL strain, ultimately leading to rupture of the ligament. While ACL strain is not directly addressed in this thesis, the kinematic motion of the tibia may provide a starting point to determine the loading profiles which ultimately lead to higher ACL strains.
48

The main role of the anterior cruciate ligament is to constrain the anterior tibial translation of the tibia. Secondary and tertiary roles of the ACL center around rotatory instability, particularly internal tibial rotation The role of anterior tibial translation in defining ACL knee pathology is well-documented throughout the literature and in clinical practice [1, 2]. The Lachman test is a clinical examination in which a physician aims to determine the existence of knee pathology by applying an anterior-posterior tibial shear load and measuring or approximating the knee laxity or tibial translation in the anterior-posterior direction. Data for the four in vitro tests exhibiting the highest levels of anterior tibial translation may be found in Table 5.1 and Figure 5-1.
There were no noteworthy differences between any of the four tests in this group at any flexion angle between 0 and 30 degrees. The loading profiles which included an internal tibial rotation moment had substantially higher standard deviations, which may have contributed to the similarities amongst groups.
Table 5.1: Anterior Tibial Translation Data Under Four Loading Conditions
Knee Flexion
268 Ant Shear 134 Ant Shear 134 Ant Shear 134 Ant Shear
0 Int Rot
0 Valgus
15 Int Rot
0 Valgus
0 Int Rot
15 Valgus
15 Int Rot
15 Valgus
ATT(mm) ATT(mm) ATT(mm) Angle (Degrees) ATT(mm)
0
◦
5
◦
10
◦
15
◦
20
◦
25
◦
30
◦
4.2
2.3
0.9
0.5
-0.4
-1.0
-1.2
±
±
±
±
±
±
±
6.1
5.2
3.8
3.1
2.7
2.7
2.6
7.3 (n=1)
6.2
1.4
2.4
1.3
0.6
0.1
±
±
±
±
±
±
21.4
19.9
18.5
17.0
16.2
15.3
0.0
0.3
-0.4
-1.8
-2.3
-2.8
-2.9
±
±
±
±
±
±
±
7.0
7.9
8.2
9.5
9.8
9.5
9.2
2.4
5.2
1.2
0.8
-0.1
-0.7
-0.8
±
±
±
±
±
±
±
14.2
15.5
15.9
14.2
12.5
11.4
10.8
49

Figure 5-1: Anterior Tibial Translation Data Under Four Loading Conditions
50

The posterior cruciate ligament works synergistically with the anterior cruciate ligament to stabilize the knee. The main role of the posterior cruciate ligament is to constrain the posterior tibial translation of the tibia. Secondary and tertiary roles of the PCL center around rotatory instability, particularly external tibial rotation. As the flexion angle of the knee and posterior tibial translation increase, the load on the
PCL also increases. During this time, there is laxity in the ACL since it is relatively unloaded in high flexion angles. While posterior tibial translation is not a prevalent motion during ACL rupture, our understanding of loading conditions resulting in high posterior tibial translation allows the creation of an envelope around the one-plane loading conditions used in the study.
Data for the four in vitro tests exhibiting the highest levels of posterior tibial translation may be found in Table 5.2 and Figure 5-2. There were no noteworthy differences between any of the four tests in this group at any flexion angle between 0 and 30 degrees. The loading profiles which included an external tibial rotation moment had substantially higher standard deviations, which may have contributed to the similarities amongst groups.
51

Table 5.2: Posterior Tibial Translation Data Under Four Loading Conditions
Knee Flexion
Angle (Degrees)
0
◦
5
◦
10
◦
15
◦
20
◦
25
◦
30
◦
201 Post Shear 0 Post Shear 134 Ant Shear 0 Post Shear
0 Ext Rot 15 Ext Rot 15 Ext Rot 10 Ext Rot
0 Valgus
PTT(mm)
0 Valgus
PTT(mm)
0 Valgus
PTT(mm)
7.5 Valgus
PTT(mm)
6.4
± 4.9
4.0
± 5.2
4.0
± 6.0
4.0
± 6.2
3.9
± 6.1
3.7
± 5.6
3.5
± 5.1
5.4
± 22.6
8.2
± 26.2
9.8
± 27.6
9.5
± 28.8
9.9
± 28.6
10.0
± 28.1
10.3
± 26.8
0.3
± 20.9
6.7
± 22.1
8.5
± 23.0
9.0
± 23.5
9.8
± 23.4
10.3
± 22.8
10.5
± 21.5
1.6
± 21.8
4.5
± 23.2
4.7
± 24.6
6.5
± 26.0
7.7
± 25.8
8.3
± 25.6
9.3
± 24.0
Figure 5-2: Posterior Tibial Translation Data Under Four Loading Conditions
52

The main secondary role of the anterior cruciate ligament is to work with the medial collateral ligament to constrain the internal rotation of the tibia. The role of internal tibial translation in defining ACL knee pathology is well-documented throughout the literature and in clinical practice [40, 41]. The pivot shift test is a clinical examination in which a physician aims to determine the existence of anterolateral knee instability by applying a combined internal tibial rotation and valgus tibial rotation. If the physician feels an anterior subluxation during extension or if the tibia’s position on the femur reduces as the knee is flexed in the range of 30 to 40 degrees, the test is positive for a torn ACL, posterolateral capsule, or IT band.
Data for the four in vitro tests exhibiting the highest levels of internal tibial rotation may be found in Table 5.3 and Figure 5-3. There are two important trends in this particular data set. First, a combined loading condition with anterior shear and internal tibial rotation experienced, on average, less internal rotation than an isolated internal tibial rotation moment. Trends in the data suggest the possibility that anterior tibial shear loading leads to less internal tibial rotation. The second trend in this data set is that the combination of valgus tibial rotation moments with internal tibial rotation moments leads to significantly less internal rotation from flexion angles of 0 to 30 degrees than an isolated internal tibial rotation moment.
53

Table 5.3: Internal Tibial Rotation Data Under Four Loading Conditions
Knee Flexion
0 Ant Shear 0 Ant Shear 134 Ant Shear 134 Ant Shear
15 Int Rot
0 Valgus
10 Int Rot
15 Valgus
15 Int Rot
0 Valgus
15 Int Rot
15 Valgus
Angle (Degrees) Int Rot(Deg) Int Rot(Deg) Int Rot(Deg) Int Rot(Deg)
0
◦
5
◦
10
◦
15
◦
20
◦
25
◦
30
◦
17.3
17.5
18.4
19.2
19.6
19.8
19.7
±
±
±
±
±
±
±
5.2
5.0
5.0
5.0
5.2
5.3
5.7
10.2
10.5
10.7
10.5
10.0
9.3
8.4
±
±
±
±
±
±
±
4.5
4.6
4.7
4.9
5.1
5.4
5.7
12.7
14.2
14.5
14.9
15.1
15.1
15.0
±
±
±
±
±
±
±
8.1
7.3
7.5
7.7
7.8
8.0
8.0
11.6
12.5
12.6
12.7
12.6
12.4
12.1
±
±
±
±
±
±
±
7.2
7.2
7.4
7.6
7.8
7.9
8.0
Figure 5-3: Internal Tibial Rotation Data Under Four Loading Conditions
54

Since the anterior cruciate ligament is responsible for stabilizing the knee against internal tibial rotation, the posterior cruciate ligament works in conjunction with the lateral collateral ligament to stabilize the knee against external tibial rotation.
Since the PCL is responsible for stability during external tibial rotation, this motion decreases the load on the ACL. This means that external tibial rotation is not a prevalent motion during ACL rupture, which has been previously discussed in the literature; however, analyzing knee kinematics under external tibial rotatory moments may improve our understanding of knee kinematics under other loading conditions
[17, 20].
Data for the four in vitro tests exhibiting the highest levels of external tibial rotation may be found in Table 5.4 and Figure 5-4. The trends exhibited in this data set are similar to that of the internal tibial rotation data in the previous section. The external rotation of an isolated 15 Nm external tibial rotation moment was greater than the external rotation produced by a combined 10 Nm external rotation moment and 15 Nm valgus moment, as well as a combined 134 N anterior tibial shear load and
15 Nm external rotation moment, at low flexion angles from 0 to 10 degrees. There were no other noteworthy differences between the groups from flexion angles of 0 to
30 degrees.
55

Table 5.4: External Tibial Rotation Data Under Four Loading Conditions
Knee Flexion
0 Ant Shear 0 Ant Shear 134 Ant Shear 134 Ant Shear
15 Ext Rot 10 Ext Rot 15 Ext Rot 15 Ext Rot
0 Valgus 15 Valgus 0 Valgus 15 Valgus
Angle (Degrees) Ext Rot(Deg) Ext Rot(Deg) Ext Rot(Deg) Ext Rot(Deg)
0
◦
5
◦
10
◦
15
◦
20
◦
25
◦
30
◦
16.9
16.9
16.4
15.9
15.4
±
±
±
±
±
4.4
4.6
16.9
± 4.8
16.7
± 5.0
5.3
5.7
6.2
13.1
13.7
±
±
2.8
2.9
13.8
± 3.1
14.0
± 3.4
14.1
14.1
13.9
±
±
±
3.8
4.1
4.5
12.7
12.7
12.7
± 7.9
12.6
± 8.0
12.5
12.2
11.9
±
±
±
±
±
8.0
7.8
8.1
8.3
8.4
14.1
14.6
14.9
14.7
±
±
±
±
7.7
6.9
14.8
± 7.0
15.0
± 7.0
15.0
± 7.1
7.0
7.1
Figure 5-4: External Tibial Rotation Data Under Four Loading Conditions
56

The third component of the pivot-shift test, valgus tibial rotation, may also play a role in ACL rupture. There are conflicting reports in the literature regarding the role of valgus tibial rotation in ACL rupture [20]. One school of thought supports the theory that ACL rupture occurs under a combined anterior tibial shear load and internal tibial rotation moment; however, the protocol for the standard pivot shift test tells us that this is not necessarily the case. During a pivot shift test, the examiner applies a combined internal tibial rotation and valgus tibial rotation and feels for anterior subluxation during extension. If valgus tibial rotation did not play a role during ACL rupture, then why would it be an important component of the pivot shift test, which attempts to translate and rotate the tibia against the constraints of the native ACL?
From understanding the basic principles of the pivot shift test, it is clear that valgus tibial rotation plays a role in ACL rupture. Further analysis and future investigations may seek to determine the magnitude of the role of valgus tibial rotation during ACL injury.
Data for the five in vitro tests exhibiting the highest levels of valgus tibial rotation may be found in Table 5.5 and Figure 5-5. At very low flexion angles (0 to 5 degrees) there were no significant differences between the five loading conditions. Once flexion angles increased to 10 degrees, loading conditions composed of an external tibial rotation moment exhibited significantly higher valgus tibial rotation than those without external tibial rotation moments. There were no noteworthy differences amongst the groups with external tibial rotation moments or amongst the groups without external tibial rotation moments at flexion angles from 0 to 30 degrees. While this seems counterintuitive, it is important to remember that the muscle loads and joint reaction forces employed by this test setup are much different from the other studies used to validate the data [2, 51, 52, 53]. The quadriceps (200 N) and hamstrings
57

(80 N) muscle loads were quite high, so larger valgus tibial rotation moments would have been necessary to overcome these constraints and force valgus rotation at low flexion angles. In this study, ± 15 Nm valgus tibial rotation moments were applied; however, Markolf et al used a ± 40 Nm valgus tibial rotation moment during the serial dissection study used to validate our data [2].
Table 5.5: Valgus Tibial Rotation Data Under Five Loading Conditions
Knee 0 Ant Shear 0 Ant Shear 0 Ant Shear 134 Ant Shear 134 Ant Shear
Flexion 0 Ext Rot 15 Ext Rot 10 Ext Rot 0 Ext Rot 15 Ext Rot
Angle
(Deg)
15 Valgus
Val Rot
(Deg)
0 Valgus
Val Rot
(Deg)
15 Valgus
Val Rot
(Deg)
15 Valgus
Val Rot
(Deg)
15 Valgus
Val Rot
(Deg)
0
◦
5
◦
10
◦
15
◦
20
◦
25
◦
30
◦
-0.7
± 2.9
-1.0
± 2.7
-1.0
± 2.8
-1.1
± 3.0
-0.9
± 3.5
-0.6
± 3.8
-0.2
± 4.1
-1.2
± 3.2
-0.3
± 3.7
0.7
± 4.1
1.9
± 4.6
3.0
± 5.1
3.9
± 5.6
4.8
± 6.1
-0.1
± 2.1
-0.1
± 2.5
0.6
± 2.9
1.6
± 3.2
2.6
± 3.5
3.9
± 3.8
5.3
± 4.2
-0.8
± 3.2
-0.5
± 3.4
-0.5
± 3.5
-0.4
± 3.6
-0.2
± 3.7
-0.0
± 3.8
0.2
± 3.9
-1.0
± 2.3
-0.3
± 3.0
0.6
± 3.4
1.8
± 4.0
3.1
± 4.4
4.4
± 4.4
5.6
± 5.1
58

Figure 5-5: Valgus Tibial Rotation Under Four Loading Conditions
59

There is agreement in the literature that varus tibial rotaiton is not a prevalent motion during ACL injury; however, analyzing knee kinematics under varus tibial rotatory moments may improve our understanding of knee kinematics under other loading conditions. Data for the three in vitro tests exhibiting the highest levels of varus tibial rotation may be found in Table 5.6 and Figure 5-6. At very low flexion angles (0 to 5 degrees) there were minimal differences between the three loading conditions. Once flexion angles increased to 10 degrees, loading conditions composed of an internal tibial rotation moment exhibited higher varus tibial rotation than the loading condition composed of an isolated varus tibial rotation moment. There were no noteworthy differences amongst the groups with internal tibial rotation moments at flexion angles from 0 to 30 degrees. In a trend similar with the valgus tibial rotation analysis, the highest levels of varus tibial rotation were seen under loading conditions consisting of an internal tibial rotation moment. While this seems counterintuitive, it is important to remember that the muscle loads and joint reaction forces employed by this test setup are much different from the other studies used to validate the data
[2, 51, 52, 53]. The quadriceps (200 N) and hamstrings (80 N) muscle loads were quite high, so larger varus tibial rotation moments would have been necessary to overcome these constraints and force varus rotation at low flexion angles. In this study, ± 15
Nm varus tibial rotation moments were applied; however, Markolf et al used a ± 40
Nm varus tibial rotation moment during the serial dissection study used to validate our data [2].
60

Table 5.6: Varus Tibial Rotation Data Under Five Loading Conditions
Knee 0 Ant Shear 0 Ant Shear 134 Ant Shear
Flexion 0 Int Rot 15 Int Rot 15 Int Rot
Angle
(Deg)
15 Varus
Val Rot
(Deg)
0 Varus
Val Rot
(Deg)
0 Varus
Val Rot
(Deg)
0
◦
5
◦
10
◦
15
◦
20
◦
25
◦
30
◦
-0.9
-0.5
-0.2
±
±
±
2.2
2.7
2.7
0.3
± 3.0
1.1
± 3.4
2.0
± 3.8
3.2
± 4.4
0.6
0.5
1.5
±
±
±
4.2
4.7
5.0
3.0
± 5.1
4.7
± 5.1
6.1
± 5.0
7.6
± 5.1
2.1
2.6
3.3
±
±
±
4.5
4.3
4.4
4.3
± 4.4
5.4
± 4.4
6.6
± 4.5
7.7
± 4.5
Figure 5-6: Valgus Tibial Rotation Data Under Four Loading Conditions
61

The objectives of this thesis were to determine in vitro knee kinematics in response to externally applied loads and moments in single- and multi-axis loading of the knee.
In order to accomplish these goals, a new methodology using a force couple testing system was developed. This system was used to study the normal knee kinematics under simulated muscle loads and various loading conditions consisting of anteriorposterior tibial shear loads, internal-external tibial rotation moments, and varusvalgus tibial rotation moments (Tables A.1, A.2, A.3). Using this system, the impact of tibial loading on knee kinematics was studied.
Based on the results of the quasi-static cadaveric testing, several conclusions may be drawn. First, the force couple testing system produces repeatable results and comparable knee kinematics with previous literature [2, 51, 52, 53]. Statiscal analysis could not be performed between previous studies and this particular study because of differences in test apparatuses, specimens, and breadth and selection of loading conditions. Even with these differences between studies, trends in the data suggest that the results from this study are similar to those previously investigated.
The second conclusion we may draw is that the insertion of Tekscan sensors into the knee joint did not alter knee kinematics in this study. During Tekscan insertion, the anterior horn of the meniscus was removed and the pressure film was inserted between the tibial plateau and the meniscus. Contact pressure data was recorded throughout four full extension-to-flexion cycles, but this data was not analyzed in this thesis.
During later work it will be fully analyzed, along with ACL and MCL strain under the various loading conditions.
62

This study has provided important insights on the effects of externally-applied tibial translation loads and rotation moments with and without tekscan pressure film inserted between the tibial plateau and the meniscus. Future work will be aimed at correlating contact pressure distributions in the knee joint with externally-applied tibial translation loads and rotation moments through extension-to-flexion cycles.
Additional work will also center on ACL and MCL strain under the same loading conditions through extension-to-flexion cycles. Once these variables are analyzed from the in vitro portion of the testing, they be imported into a finite element model to determine the position and loading condition that produce the highest ACL:MCL strain. Finally, dynamic in vitro testing will be conducted to attempt to rupture the ACLs of the specimens used during this study. The results from such experiments could possibly lead to a better understanding of ACL injuries, their treatment methods, and injury prevention approaches.
63

[1] Butler, D.L., Noyes, F.R., and Grood, E.S. Ligamentous Restraints to Anterior-
Posterior Drawer in the Human Knee: A Biomechanical Study.
The Journal of
Bone and Joint Surgery (1980). 62:259-270.
[2] Markolf, K.L, Mensch, J.S., and Amstutz, H.C. Stiffness and Laxity of the Knee –
The Contributions of the Supporting Structures: A Quantitative in vitro Study.
The Journal of Bone and Joint Surgery (1976). 58:583-594.
[3] Dehaven, K.E. The role of the meniscus. In: Ewing, J.W., ed.
Articular Cartilage and Knee joint Function: Basic Scence and Arthroscopy (1990). New York, NY:
Raven Press. 103.
[4] Morgan, C.D., Kalman, V.R., and Grawl, D.M. Definitive Landmarks for Reproducible Tibial Tunnel Placement in Anterior Cruciate Ligament Reconstruction.
Arthroscopy (1995). 3:275-288.
[5] Cross, M.J. and Powell, J.F. Long-Term Follow-Up of Posterior Cruciate Ligament Rupture: A Study of 116 Cases.
The American Journal of Sports Medicine
(1984). 4:292-297.
[6] Dehaven, K.E. and Lintner, D.M. Athletic Injuries: Comparison by Age, Sports, and Gender.
The American Journal of Sports Medicine (1986). 3:218-224.
[7] Piziali, R.L., Seering, W.P., Nagel, D.A. and Schurman, D.J. The Function of the Primary Ligaments of the Knee in Anterior-Posterior and Medial-Lateral
Motions.
Journal of Biomechanics (1980). 9:777-784.
64

[8] Emerson, R.J. Basketball Knee Injuries and the Anterior Cruciate Ligament.
Clinical Journal of Sports Medicine (1993). 2:317-238.
[9] Loudon, J.K., Jenkins, W. and Loudon, K.L. The Relationship Between Static
Posture and ACL Injury in Female Athletes.
Journal of Orthopaedic & Sports
Physical Therapy (1996). 4:91-97.
[10] Uhorchak, J.M., Scoville, C.R., Williams, G.N., Arciero, R.A., St Pierre, P.
and Taylor, D.C. Risk Factors Associated with Noncontact Injury of the Anterior Cruciate Ligament: A Prospective Four-Year Evaluation of 859 West Point
Cadets.
The American Journal of Sports Medicine (2003). 6:831-842.
[11] Hewett, T.E., Myer, G.D. and Ford, K.R. Anterior Cruciate Ligament Injuries in Female Athletes: Part 2, A Meta-Analysis of Neuromuscular Interventions
Aimed at Injury Prevention.
The American Journal of Sports Medicine (2006).
3:490-498.
[12] Lee, C.Y., Smith, C.L., Zhang, X., Hsu, H.C., Wang, D.Y. and Luo, Z.P. Tensile
Forces Attenuate Estrongen-Stimulated Collagen Synthesis in the ACL.
Biochemical and Biophysical Research Communications (2004). 371:1221-1225.
[13] Slauterbeck, J.L., Fuzie, S.F., Smith, M.P., Clark, R.J., Xu, K.T., Starch, D.W.
and Hardy, D.M. The Menstrual Cycle, Sex Hormones, and Anterior Cruciate
Ligament Injury.
Journal of Athletic Training (2002). 27:275-278
[14] Wojtys, E.M., Huston, L.J., Boynton, M.D., Spindler, K.P and Lindenfeld, T.N.
The Effect of hte Menstrual Cycle on Anterior Cruciate Ligament Injuries in
Women as Determined by Hormone Levels.
The American Journal of Sports
Medicine (2002). 30:182-188.
[15] Agel, J., Arendt, E.A. and Bershadsky, B. Anterior Cruciate Ligament Injury
65

in National Collegiate Athletic Association Basketball and Soccer: A 13-Year
Review.
The American Journal of Sports Medicine (2005). 33:524-530.
[16] Arendt, E. and Dick, R. Anterior Cruciate Ligament Injury Patterns Among
Collegiate Men and Women.
Journal of Athletic Training (1999). 34:86-92.
[17] Hewett, T.E., Lindenfeld, T.N., Riccobene, J.V. and Noyes, F.R. The Effect of
Neuromuscular Training on the Incidence of Knee Injury in Female Athletes: A
Propsective Study.
The American Journal of Sports Medicine (1999). 27:699-706.
[18] Krosshaug, T., Andersen, T.E., Olsen, O.E., Myklebust, G. and Bahr, R. Research Approaches to Describe the Mechanisms of Injuries in Sport: Limitations and Possibilities.
British Journal of Sports Medicine (2005). 39:330-339.
[19] Majewski, M., Susanne, H. and Klaus, S. Epidemiology of Ahtletic Knee Injuries:
A 10-Year Study.
Knee (2006). 13:184-188.
[20] Hewett, T.E., Myer, G.D., Ford, K.R., Heidt, R.S., Colosimo, A.J., McLean,
S.G., van den Begert, A.J., Paterno, M.V. and Succop, P. Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior
Cruciate Ligament Injury Risk in Female Athletes: A Prospective Study.
The
American Journal of Sports Medicine (2005). 33:492-501.
[21] Olsen, O.E., Myklebust, G., Engebretsen, L. and Bahr, R. Injury Mechanisms for Anterior Cruciate Ligament Injuries in Team Handball: A Systematic Video
Analysis.
The American Journal of Sports Medicine (2004). 32:1002-1012.
[22] Markolf, K.L., Burchfield, D.M., Shapiro, M.M., Shepard, M.F., Finerman, G.A.
and Slauterbeck, J.L. Combined Knee Loading States that Generate High Anterior Cruciate Ligament Force.
Journal of Orhtopaedic Research (1995). 13:930-
935.
66

[23] McLean, S.G., Huang, X., Su, A. and van den Bogert, A.J. Sagittal Plan Biomechanics Cannot Injure the ACL During Sidestep Cutting.
Clinical Biomechanics
(2004). 19:828-838.
[24] Clasby, L. and Young, M.A. Management of Sports-Related Anterior Cruciate
Ligament Injuries.
Association of Perioperative Registered Nurses (1997). 4:607.
[25] Unwin, A. What’s New in Anterior Cruciate Ligament Surgery?
Orthopaedics and Trama (2010). 2:100-106.
[26] Laxdal, G., Karus, J., Hansson, L., Heidvall, M., Ejerhed, L. and Karlsson,
J. A Propsective Randomized Comparison of Bone-Patellar Tendon-Bone and
Hamstring Grafts for Anterior Cruciate Ligament Reconstruction.
Arthroscopy
(2005). 1:34-42.
[27] Gulotta, L.V. and Rodeo, S.A. Bilogy of Autograft and Allograft Healing in
Anterior Cruciate Ligament Reconstruction.
Clinical Journal of Sports Medicine
(2007). 26:509-24.
[28] Brown, C.H., Wilson, D.R., Hecker, A.T. and Ferragamo, M. Graft-Bone Motion and Tensile Properties of Hamstring and Patellar Tendon Anterior Cruciate
Ligament Femoral Graft Fixation Under Cyclic Loading.
Arthroscopy (2005).
9:922-935.
[29] Magen, H.E., Howell, S.M. and Hull, M.L. Structural Properties of Six Tibial Fixation Methods for Anterior Cruciate Ligament Soft Tissue Grafts.
The
American Journal of Sports Medicine (1999). 1:35-48.
[30] LaPrade, R.F., Wentorf, F.A., Fritts, H., Gundry, C. and Hightower, C.D. A
Prospective Magnetic Resonance Imaging Study of the Incidence of Posterolateral and Multiple Ligament Injuries in Acute Knee Injuries Presenting with a
Hemiarthrosis.
Arthroscopy (2007). 23:1341-1347.
67

[31] Ruiz, A.L., Kelly, M. and Nutton, R.W. Arhtroscopic ACL Reconstruction: A
5-9 Year Follow-Up.
Knee (2002). 9:197-200.
[32] Lohmander, L.S., Englund, P.M., Dahl, L.L and Roos, E.M. The Long-Term
Consequence of Anterior Cruciate Ligament and Meniscus Injuries: Osteoarthritis.
The American Journal of Sports Medicine (2007). 35:1756-1769.
[33] Myklebust, G. and Bahr, R. Return to Play Guidelines After Anterior Cruciate
Ligament Surgery.
British Journal of Sports Medicine (2005). 39:127-131.
[34] McLean, S.G., Huang, X. and van den Bogert, A.J. Association Between Lower
Extremity Posture at Contact and Peak Knee Valgus Moment During Sidestepping: Implications for ACL Injury.
Clinical Biomechanics (2005). 20:863-870.
[35] Chappell, J.D., Creighton, R.A., Giuliani, C., Yu, B. and Garrett, W.E. Kinematics and Electromyography of Lnading Preparation in Vertical Stop-Jump:
Risks for Noncontact Anterior Cruciate Ligament Injury.
The American Journal of Sports Medicine (2007). 35:235-241.
[36] Padua, D.A., Marshall, S.W., Beutler, A.I., DeMaio, M., Boden, B.P., Yu, B.
and Garrett, W.E. Predictors of Knee Valgus Angle During a Jump-Landing
Task.
Medicine & Science in Sports & Exercises (2005). 37:S398.
[37] Boden, B.P., Dean, G.S., Feagin, J.A. and Garrett, W.E. Mechanicsm of Anterior
Cruciate Ligament Injury.
Orthopedics (2000). 23:573-578.
[38] Cochrane, J.L., Lloyd, D.G., Buttfield, A., Seward, H. and McGivern, J. Characteristics of Anterior Cruciate Ligament Injuries in Australian Football.
Journal of Sports Science and Medicine (2007). 10:96-104.
[39] Krosshaug, T., Nakamae, A., Boden, B.P., Engebretsen, L., Smith, G., Slauterbeck, J.R., Hewett, T.E. and Bahr, R. Mechanisms of Anterior Cruciate Liga-
68

ment Injury in Basketball: Video Analysis of 39 Cases.
The American Journal of Sports Medicine (2007). 35:359-367.
[40] Benvenuti, J.F., Vallotton, J.A. and Leyvraz, P.F. Objective Assessment of the
Anterior Tibial Translation in Lachman Test Position: Comparison Between
Three Types of Measurement.
Knee Surgery, Sports Traumatology, Arthroscopy
(1998). 6:215-219
[41] Logan, M.C., Williams, A., Lavelle, J. Gedroyc, W. and Freeman, M. What
Really Happens During the Lachman Test?
A Dynamic MRI Analysis of
Tibiofemoral Motion.
The American Journal of Sports Medicine (2004). 50:3145-
3152.
[42] Daniel, D.M., Malcom, L.L., Losse, G., Stone, M.L., Sachs, R. and Burks, R.
Instrumented Measurement of Anterior Laxity of the Knee.
Journal of Bone and
Joint Surgery (1985). 67A:720-726.
[43] Stijak, L., Herzog, R.F and Schai, P. Is There an Influence of the Tibial Slope of the Lateral Condyle on the ACL Lesion? A Case-Control Study.
Knee Surgery,
Sports Traumatology, Arthroscopy (2008). 16:112-117.
[44] Kaplan, P.A., Walker, C.W., Kilcoyne, R.F., Brown, D.E., Tusek, D. and Dussault, R.G. Occult Fracture Patterns of the Knee Associated with Anterior Cruciate Ligament Tears: Assessment with MR Imaging.
Radiology (1992). 183:835-
838.
[45] Speer, K.P., Spritzer, C.E., Bassett, F.H., Feagin, J.A. and Garrett, W.E. Osseous Injury Associated with Acute Tears of the Anterior Cruciate Ligament.
The American Journal of Sports Medicine (1992). 20:382-389.
[46] Gardiner, J.C. and Weiss, J.A. Subject-Specific Finite Element Analysis of the
69

Human Medial Collateral Ligament During Valgus Knee Loading.
Journal of
Orthopaedic Research (2003). 1098-1106.
[47] McLean, S.G., Huang, X. and van den Bogert, A.J. Investigating Isolated Neuromuscular Control Contributions to Non-Contact Anterior Cruciate Ligament
Injury Risk Via Computer Simulation Methods.
Clinical Biomechanics (2008).
23:926-936.
[48] Pena, E., Calvo, B., Martinez, M.A. and Doblare, M. A Three-Dimensional
Finite Element Analysis of the Combined Behavior of Ligaments and Menisci in the Healthy Human Knee Joint.
Journal of Biomechanics (2006). 39:1686-1701.
[49] Donahue, T.L., Hull, M.L., Rashin, M.M. and Jacobs, C.R. A Finite Element
Model of the Human Knee Joint for the STudy of Tibio-Femoral Contact.
Journal of Biomechanical Engineering (2002). 124:273-280.
[50] Gardiner, J.C., Weiss, J.A. and Rosenberg, T.D. Strain in the Human Medial
Collateral Ligament During Valgus Loading of the Knee.
Clinical Orthopaedics and Related Research (2001). 266-274.
[51] Yamamoto, Y., Hsu, W.H., Woo, S.L., Van Scyoc, A.H., Takakura, Y. and Debski, R.E. Knee Stability and Graft Function After Anterior Cruciate Ligament
Reconstruction: A Comparison of a Lateral and an Anatomical Femoral Tunnel
Placement.
The American Journal of Sports Medicine (2004). 1825-1832.
[52] Li, G., Rudy, T.W., Sakane, M., Kanamori, A., Ma, C.B. and Woo, S.L. The
Importance of Quadriceps and Hamstring Muscle Loading on Knee Kinematics and in-situ Forces in the ACL.
Journal of Biomechanics (1999). 32:395-400.
[53] Harner, C.D., Vogrin, T.M., Hoher, J., Ma, C.B. and Woo, S.L. Biomechanical
Analysis of a Posterior Cruciate Ligament Reconstruction: Deficiency of the
70

Posterolateral Structures as a Cause of Graft Failure.
The American Journal of
Sports Medicine (2000). 28:32-39.
[54] Balasubramanian, S. Posterior Cruciate Ligament (PCL) Injury and Repair: A
Biomechanical Evaluation of the Human Knee Joint Under Dynamic Posterior
Loading; Kinematics and Contact Pressure Measurements in Normal, PCL Deficient and PCL Reconstructed Knees. Dissertation, Wayne State University,
Detroit Michigan (2006).
71

This appendix provides tables of the loading profiles used during this in vitro kinematic investigation. The loading profiles are divided into three tables: one-plane; two-plane; and three-plane loading conditions.
72

Table A.1: List of One-Plane Loading Conditions
Anterior (+) / Valgus (+) / External (+) / Compressive (+) /
Posterior (-) Varus (-) Internal (-) Distractive (-)
Tibial Shear Tibial Rotation Tibial Rotation
Newtons Newton-Meters Newton-Meters
Joint Force
Newtons
0
0
0
0
0
0
0
0
0
0
0
-134
-201
67
134
201
268
0
0
0
0
-67
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-5
-10
-15
5
7.5
10
15
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-5
-10
-15
5
10
15
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
-67
-134
-67
67
134
150
150
73

Table A.2: List of Two-Plane Loading Conditions
Anterior (+) / Valgus (+) / External (+) / Compressive (+) /
Posterior (-) Varus (-) Internal (-)
Tibial Shear Tibial Rotation Tibial Rotation
Distractive (-)
Joint Force
Newtons Newton-Meters Newton-Meters Newtons
134
134
0
0
0
0
134
134
0
0
0
0
134
134
134
134
134
134
134
134
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
0
0
0
0
0
0
0
0
0
0
0
0
-5
-5
-10
-10
5
5
10
10
-3
-6
-9
-12
-15
3
6
9
12
15
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
74

Table A.3: List of Three-Plane Loading Conditions
Anterior (+) / Valgus (+) / External (+) / Compressive (+) /
Posterior (-) Varus (-) Internal (-)
Tibial Shear Tibial Rotation Tibial Rotation
Distractive (-)
Joint Force
Newtons Newton-Meters Newton-Meters Newtons
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
7.5
15
-3
-3
-6
-6
-9
-9
-12
-12
-15
-15
3
3
6
6
9
9
12
12
15
15
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
75

Figure B-1: One-Plane: Ant/Post Tib Shear - Ant/Post Tib Translation
76

Figure B-2: One-Plane: Ant/Post Tib Shear - Int/Ext Tib Rotation
Figure B-3: One-Plane: Ant/Post Tib Shear - Var/Val Tib Rotation
77

Figure B-4: One-Plane: Int/Ext Rot - Ant/Post Tib Translation
78

Figure B-5: One-Plane: Int/Ext Rot - Int/Ext Tib Rotation
Figure B-6: One-Plane: Int/Ext Rot - Var/Val Tib Rotation
79

Figure B-7: One-Plane: Var/Val Rot - Ant/Post Tib Translation
80

Figure B-8: One-Plane: Var/Val Rot - Int/Ext Tib Rotation
Figure B-9: One-Plane: Var/Val Rot - Var/Val Tib Rotation
81

Figure B-10: Two-Plane: Ant Shear + Int/Ext Rot - Ant/Post Tib Translation
82

Figure B-11: Two-Plane: Ant Shear + Int/Ext Rot - Int/Ext Tib Rotation
Figure B-12: Two-Plane: Ant Shear + Int/Ext Rot - Var/Val Tib Rotation
83

Figure B-13: Two-Plane: Ant Shear + Var/Val Rot - Ant/Post Tib Translation
84

Figure B-14: Two-Plane: Ant Shear + Var/Val Rot - Int/Ext Tib Rotation
Figure B-15: Two-Plane: Ant Shear + Var/Val Rot - Var/Val Tib Rotation
85

Figure B-16: Two-Plane: Int/Ext Rot + 7.5 Nm Var/Val Rot - Ant/Post
Tib Translation
86

Figure B-17: Two-Plane: Int/Ext Rot + 7.5 Nm Var/Val Rot - Int/Ext Tib
Rotation
Figure B-18: Two-Plane: Int/Ext Rot + 7.5 Nm Var/Val Rot - Var/Val Tib
Rotation
87

Figure B-19: Two-Plane: Int/Ext Rot + 15 Nm Var/Val Rot - Ant/Post Tib
Translation
88

Figure B-20: Two-Plane: Int/Ext Rot + 15 Nm Var/Val Rot - Int/Ext Tib
Rotation
Figure B-21: Two-Plane: Int/Ext Rot + 15 Nm Var/Val Rot - Var/Val Tib
Rotation
89

Figure B-22: Three-Plane: Ant/Post Tib Translation
90

Figure B-23: Three-Plane: Int/Ext Tib Rotation
Figure B-24: Three-Plane: Var/Val Tib Rotation
91

Figure B-25: Three-Plane: Ant/Post Tib Translation
92

Figure B-26: Three-Plane: Int/Ext Tib Rotation
Figure B-27: Three-Plane: Var/Val Tib Rotation
93