Knee Tissue Strains and Effectiveness of a Novel Functional ACL Knee Brace during Dynamic In

112 Pages·2017·3.62 MB·English

Knee Tissue Strains and Effectiveness of a Novel
Functional ACL Knee Brace during Dynamic In-Vitro
Loading
by
Stefan Sebastian Tomescu
A thesis submitted in conformity with the requirements
for the degree of Master of Science
Institute of Medical Science
University of Toronto
© Copyright by Stefan Sebastian Tomescu, 2017
Knee Tissue Strains and Effectiveness of a Novel Functional
ACL Knee Brace during Dynamic In-Vitro Loading
Stefan Sebastian Tomescu
Master of Science
Institute of Medical Science
University of Toronto
2017
Abstract
Functional knee braces are commonly prescribed to help stabilize and protect the knee after an
ACL injury or reconstruction. Newer brace designs employ a dynamic tensioning system to
apply directional forces to the knee. The purpose of this thesis was to characterize meniscal
loading under dynamic loading conditions and test the efficacy of a functional knee brace
equipped with a dynamic tensioning system to reduce ACL and meniscal strain. A combined in-
vivo/in-silico/in-vitro testing method was used to quantify tissue strains and the effect of the
brace on cadaveric specimens. Tissue strains were quantified and validated before and after
reconstruction, and the brace was found to lower tissue strains during most conditions. This work
provides supportive evidence for the use of braces with a dynamic tensioning system for patients
who are ACL deficient or following reconstruction.
ii
Acknowledgments
There are many individuals without whom this thesis may not have come to fruition. Firstly, I’d
like to thank my supervisor, Dr. Cari Whyne, and supervisory collaborator, Dr. Naveen
Chandrashekar, who have aided in overseeing and guiding all aspects of this thesis. Dr. Cari
Whyne has been both a direct supervisor of this work and a research mentor for my professional
career. Her skill and experience as a scientific researcher has helped steer this thesis in the right
direction, even when that direction wasn’t always clear. Dr. Naveen Chandrashekar, has not only
provided the necessary knowledge to complete this thesis, but continuously aided to enhance the
quality of the work being done, and the possibilities for further involvement in biomechanical
research. He also connected me with a network of support for this research and other endeavors
outside of the thesis, ensuring that I have opportunity to expand my research career under his
support. Both Cari and Naveen’s mentorship and support have made this thesis a positive
learning experience.
I’d like to also express gratitude to the other individuals that are members of my thesis
committee, Dr. Emil Schemitsch and Dr. Tyson Beach. Dr. Emil Schemitsch kindly agreed to be
part of this committee and worked on fitting each meeting into his demanding surgical and
administrative career. His critical input and expertise have contributed significantly to enriching
the work. I also thank Dr. Schemitsch for continuing to be involved even after relocating to
University of Western. Dr. Tyson Beach has offered both his time and expertise in Biomechanics
in aid of this project. His knowledge in the field added positively to discussion and helped
significantly broaden my experience in Biomechanics.
There were many people that were integral to the completion of this thesis, but none more so
than my lab mate Mr. Ryan Bakker. Ryan was instrumental in all phases of the thesis, devoting
his training, knowledge and time to aid in the computer simulations, cadaver preparation, and
testing. Without his experience, the testing may not have been successful. Additionally, Ryan
kindly spent many hours discussing and ironing out the details of the work with me. I’m glad that
in working with Ryan I have gained not only a lab mate and professional colleague, but also a
friend.
iii
Finally, I’d like to dedicate this thesis to my family, whose sacrifices, support and
encouragement have enabled me throughout this research. My parents, Drs. Mihaila and Stefan
Tomescu, and my grandmother, Mrs. Maria Traistaru, have sacrificed much to provide me with
the opportunities to pursue my career, and without them I would not be where I am today. I’d
also like to thank my wife, Mrs. Jelena Tomescu, to whom I became engaged and married in the
process of completing this thesis. She has been a supportive and enthusiastic partner, comforting
me during times of stress and celebrating with me every small accomplishment and success. I’d
also like to thank my parents in-law, Mr. Milutin and Mrs. Kata Zaric, for their generosity and
kindness. It is all these individuals and their continued support, both professional and personal,
that made this experience rewarding and enjoyable.

iv
Contributions
Many lab mates, technicians, experts and helpers aided and assisted in this project both directly
and indirectly.
I’d like to thank the following for their specific contributions to this work:
Dr. David Wasserstein for connecting me with the funding partner,
Mr. Micah Nicholls, our partner at Össur Inc., for his brace insights and study design,
Mrs. Helen Chong for helping with the initial phases of data collection in the motion
capture lab,
Mr. Gajendra Hangalur and Mr. Mayank Kalra for their important contributions
throughout the preparation and testing of the cadavers,
Mr. Adam Zhang, Mr. Liu He, Ms. Ania Polak, Mr. Nokhez Qazi, Mr. Neil Griffet, and
Mr. Tom Gawel for offering a helping hand with the lab work,
and to Össur Inc for providing the necessary funding and braces to complete this work.
Additional funding was received from NSERC, the Susanne and William Holland Surgeon
Scientist Award GSEF, and the Queen Elizabeth II/Wellesley Surgeons Graduate Scholarships in
Science and Technology.

v
Table of Contents

Acknowledgments........................................................................................................................... iii
Contributions.................................................................................................................................... v
Table of Contents ............................................................................................................................ vi
List of Appendices .......................................................................................................................... ix
List of Figures .................................................................................................................................. x
List of Tables ................................................................................................................................ xiv
List of Abbreviations ..................................................................................................................... xv
1 Chapter 1 Literature Review .......................................................................................................1
1.1 Human Body and Anatomy ......................................................................................................1
1.1.1 Anatomical Orientation............................................................................................1
1.1.2 General Knee Anatomy............................................................................................2
1.1.3 Anatomy and Function of the Anterior Cruciate Ligament .....................................3
1.1.4 Meniscal Anatomy and Function .............................................................................4
1.2 ACL injury ................................................................................................................................6
1.2.1 Risk Factors..............................................................................................................6
1.2.2 Treatment Options....................................................................................................7
1.3 Bracing......................................................................................................................................9
1.3.1 Prophylactic Braces..................................................................................................9
1.3.2 Functional Knee Braces .........................................................................................10
1.3.3 Dynamic Tensioning Systems................................................................................12
1.3.4 Neuromuscular Effects of Bracing.........................................................................13
1.4 Testing Methodologies ...........................................................................................................14
vi
1.4.1 In-Vivo ...................................................................................................................14
1.4.2 In-Silico..................................................................................................................15
1.4.3 In-Vitro...................................................................................................................15
1.4.4 Strain Measurement Techniques ............................................................................17
1.4.5 In-Vitro Knee Brace Testing..................................................................................19
2 Chapter 2 Hypotheses and Research Aims ...............................................................................21
2.1 Thesis Rationale......................................................................................................................21
2.2 Thesis Hypothesis ...................................................................................................................22
2.3 Thesis Outline .........................................................................................................................22
3 Chapter 3 Dynamic Meniscal and ACL Strains are Maintained Following ACL
Reconstruction...........................................................................................................................24
3.1 Introduction.............................................................................................................................25
3.2 Methodology ...........................................................................................................................26
3.3 Results.....................................................................................................................................29
3.4 Discussion ...............................................................................................................................30
4 Chapter 4 Efficacy of an ACL Functional Knee Brace with a Dynamic Tension System .......40
4.1 Introduction.............................................................................................................................41
4.2 Materials and Methods ...........................................................................................................42
4.3 Results.....................................................................................................................................45
4.4 Discussion ...............................................................................................................................46
4.5 Summary/Conclusions ............................................................................................................50
5 Chapter 5 General Discussion ...................................................................................................54
5.1 Summary and Discussion .......................................................................................................54
5.2 Contributions ..........................................................................................................................56
5.3 Future Directions ....................................................................................................................57
vii
6 References .................................................................................................................................59
7 Appendix 1: Cadaver Preparation .............................................................................................76
7.1 Dissection ...............................................................................................................................76
7.2 Muscle Cable Insertion ...........................................................................................................77
7.3 Foaming Procedure .................................................................................................................78
7.4 Moment Arm Calculations .....................................................................................................84
8 Appendix 2: Pilot Testing .........................................................................................................87
8.1 Pilot 1 ......................................................................................................................................87
8.2 Pilot 2 ......................................................................................................................................92
8.3 Pilot 3 ......................................................................................................................................95

viii
List of Appendices
Appendix 1: Cadaver Preparation ..................................................................................................76
Appendix 2: Pilot Testing ..............................................................................................................87

ix
List of Figures
Figure 1. Knee Ligament Anatomy ................................................................................................ 3
Figure 2. ACL Anatomy. ACL fibers are marked in consecutive order (A-C) with the knee in
zero degrees of flexion. Fibers reorganize as the knee flexes to 90 degrees. Apostrophe denotes
distal fiber endings. ......................................................................................................................... 4
Figure 3. Meniscal Anatomy........................................................................................................... 5
Figure 4. ACL Rebound Brace with Dynamic Tensioning System. (A) Back view. (B) side view,
(C) DTS close up, (D), adjustable torque knob ............................................................................ 13
Figure 5. Overview of In-vivo/In-Silico(Computational)/In-Vitro Method for Jump Landing.
Extracted with Permission from Bakker et al 2016. ..................................................................... 17
Figure 6. Experimental Overview. (1) In-vivo motion capture setup, (2) OpenSim
musculoskeletal model, (3) Dynamic knee simulator. .................................................................. 36
Figure 7. Motion Capture Activities. (A) Double leg squat, (B) single leg squat, (C) gait. ......... 36
Figure 8. Kinematic, Kinetic Variables and Muscle Forces Extracted from OpenSim for DSL,
SLS, and Gait. ............................................................................................................................... 37
Figure 9. Average Strain Profiles of the ACL (n=7) and Meniscus (n=5) for DSL, SLS and Gait.
ACL strain decreased during DLS and SLS and increased throughout the gait cycle. Meniscal
strain followed a similar pattern between ACL intact and reconstructed conditions. .................. 38
Figure 10. Comparison of Relative ACL strain during DLS. Both curves are presented as strain
relative to starting position rather than resting length. Current strain values (n=7) and pattern
match results of Beynnon et al (1998) (n=8). ............................................................................... 38
Figure 11. Comparison of ACL strain during the gait cycle. Current ACL strain pattern (n=7) is
similar to the findings of Taylor et al (2013) (n=32). ................................................................... 39
x