Patient-Specific Modeling Of Adult Acquired Flatfoot Deformity Before And After Surgery

195 Pages·2016·5.35 MB·English

Virginia Commonwealth University
VCU Scholars Compass
Theses and Dissertations Graduate School
2013
Patient-Specific Modeling Of Adult Acquired
Flatfoot Deformity Before And After Surgery
Edward Meade Spratley
Virginia Commonwealth University
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PATIENT-SPECIFIC MODELING OF ADULT ACQUIRED FLATFOOT
DEFORMITY BEFORE AND AFTER SURGERY

A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of
Philosophy in Biomedical Engineering at Virginia Commonwealth University

by

EDWARD MEADE SPRATLEY
B.S., University of Virginia, 2004
M.S., Virginia Commonwealth University, 2009

Director: Jennifer S. Wayne, Ph.D.
Departments of Biomedical Engineering & Orthopaedic Surgery
Virginia Commonwealth University
Richmond, Virginia
November, 2013
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ACKNOWLEDGEMENT
It seems very strange to be writing an acknowledgments page and setting about wrapping
up my duties here at VCU. While I'm sure no one ever says that this time has come too soon, it
is nonetheless bittersweet to be moving on. Over the past years, I've come to view VCU as a
home away from home and certainly much more than just the place I went for a degree. So, first
and foremost, for that welcome feeling, and for any positive professional skill or trait that I may
claim, I am indebted to my wonderful advisor Dr. Jennifer Wayne. She has helped me in so
many ways in her capacity as a teacher, a mentor, a colleague, and finally as a friend. I count
myself lucky to have been able to study under her for these past six years.
I would also like to thank my many peers and lab mates, past and present, for their
friendship and excellent collaboration. Among these especially, I would like to thank Johnny
Owen for his guidance, statistics wizardry, and unflappable, kind demeanor; Sean Higgins and
Charles Taylor for exposing me to new skills and challenges, as well as being terrific friends;
Erika Matheis for all her efforts and sarcastic charm as we worked together on this study; and
Ruchi Chande for putting up with me and always setting such a fine example of hard work,
compassion, and humor.
I would like to acknowledge Dr. Gerald Miller who has served as both a Master's and
Doctoral advisor to me and been a mentor and confidant since my first year here at VCU. He has
been a great source of support and inspiration and no small amount of prodding. Thank you to
my committee members and the faculty and staff who have helped us get this project off the
ground, especially Dr. Robert Adelaar for his vision and enthusiasm for our work; Carol Ford
and Barbara Ennis for coordinating all the schedules of the doctors and our patients; and Dr.
Curtis Hayes and Lanea Bare for helping us gather and make sense of all the x-rays and MRIs.
Finally, I need to thank my family and friends for all their support and for making
Richmond home now for so many years. Thank you to my parents Katherine and Jack who have
always encouraged me in everything I do. Thanks to my Grandmother for all that she has done to
help me through this program. Lastly, thank you to my wife Jennifer, for just absolutely
everything. She has been my loudest cheerleader and best friend for so many years and I can't
wait to see what's in store for us next.

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TABLE OF CONTENTS
Page
ACKNOWLEDGEMENT ................................................................................................... iii
TABLE OF CONTENTS ...................................................................................................... iv
LIST OF FIGURES .............................................................................................................. ix
LIST OF TABLES ............................................................................................................. xiii
ABSTRACT ........................................................................................................................ xiv
1. INTRODUCTION........................................................................................................... 1
1.1 Overview Of Computational Modeling ................................................................. 1
1.1.1 Finite Element Analysis ..................................................................................... 1
1.1.2 Rigid Body Kinematics ....................................................................................... 2
1.2 Scope of this Dissertation ...................................................................................... 5
2. FOOT AND ANKLE ANATOMY ............................................................................. 6
2.1 Bony Anatomy ....................................................................................................... 6
2.2 Ligaments ............................................................................................................. 12
2.3 Muscle Constraints............................................................................................... 17
3. ADULT ACQUIRED FLATFOOT DEFORMITY ................................................ 21
3.1 Clinical Presentation and Diagnosis .................................................................... 21
3.1.1 Radiographic Evaluation ................................................................................. 22
3.1.2 Soft-Tissue and Kinematic Evaluation ............................................................. 25
3.2 Etiology ................................................................................................................ 26
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3.2.1 Posterior Tibial Tendon Dysfunction............................................................... 27
3.2.2 Ligamentous Changes ...................................................................................... 28
3.3 Stages of AAFD ................................................................................................... 29
3.4 Treatment ............................................................................................................. 31
3.4.1 Tendon Transfer as PTT Augmentation ........................................................... 33
3.4.2 Medializing Calcaneal Osteotomy ................................................................... 36
4. STUDY DESIGN AND DATA ACQUISITION ..................................................... 38
4.1 Patient Recruitment .............................................................................................. 38
4.2 X-ray .................................................................................................................... 39
4.3 Plantar Force Measurements ................................................................................ 41
4.4 Magnetic Resonance Imaging (MRI) ................................................................... 41
4.4.1 Tissue Attenuation ............................................................................................ 44
4.5 Study Objectives .................................................................................................. 46
5. MODEL CREATION ................................................................................................ 48
5.1 Overview .............................................................................................................. 48
5.2 Mask Creation And Thresholding ........................................................................ 49
5.3 Preprocessing ....................................................................................................... 50
5.3.1 Morphology Operations ................................................................................... 51
5.4 Stereolithography (STL) Files ............................................................................. 53
5.4.1 Mesh Quality .................................................................................................... 55
5.4.2 Smoothing ........................................................................................................ 56
5.4.3 Triangle Reduction........................................................................................... 57
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5.5 Characterizing The Models .................................................................................. 60
5.5.1 Long Bone Axes................................................................................................ 60
5.5.2 Talar Dome ...................................................................................................... 62
5.6 Anatomy Reconstruction ..................................................................................... 65
5.6.1 5th Metatarsals ................................................................................................ 66
5.6.2 Proximal Tibia and Fibula............................................................................... 68
6. RIGID-BODY KINEMATIC SIMULATIONS ...................................................... 70
6.1 Overview .............................................................................................................. 70
6.2 Defining Neutral Plantarflexion ........................................................................... 70
6.3 Origins And Insertions ......................................................................................... 73
6.4 COSMOSMotion ................................................................................................. 74
6.4.1 Solver Parameters ............................................................................................ 75
6.4.2 Contact parameters .......................................................................................... 76
6.5 Body Weight And Muscles .................................................................................. 79
6.5.1 Achilles Tendon Course ................................................................................... 81
6.5.2 FHL Tendon Course ........................................................................................ 82
6.5.3 FDL Tendon Course ........................................................................................ 83
6.5.4 Peronei Tendon Courses .................................................................................. 85
6.6 Ligament Constraints ........................................................................................... 87
6.6.1 Ligament Arrangement and Properties ........................................................... 88
6.6.2 Mechanical Modeling ...................................................................................... 92
6.6.3 FORTRAN Expressions .................................................................................... 93
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7. PREOPERATIVE MODEL/PATIENT AGREEMENT ....................................... 95
7.1 Overview .............................................................................................................. 95
7.2 Methods................................................................................................................ 95
7.2.1 Tissue Grading ................................................................................................. 95
7.2.2 Model Loading ................................................................................................. 96
7.2.3 Measurements and Validation ......................................................................... 97
7.3 Results ................................................................................................................ 100
7.3.1 Population Characteristics ............................................................................ 100
7.3.2 Radiographic Validation - Preoperatively..................................................... 103
7.4 Discussion .......................................................................................................... 107
8. POSTOPERATIVE MODEL/PATIENT AGREEMENT ................................... 112
8.1 Overview ............................................................................................................ 112
8.2 Methods.............................................................................................................. 113
8.2.1 X-ray and Plantar Force Data Collection ..................................................... 113
8.2.2 Model Creation and Loading ......................................................................... 117
8.2.3 Measurements and Validation ....................................................................... 120
8.3 Results ................................................................................................................ 121
8.3.1 Radiographic Validation - Postoperatively ................................................... 121
8.3.2 Plantar Force Validation ............................................................................... 124
8.3.3 Soft-tissue Strains and Joint Contact Force .................................................. 125
8.4 Discussion .......................................................................................................... 127
9. PARAMETRIC ANALYSIS ................................................................................... 135
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9.1 Overview ............................................................................................................ 135
9.2 Methods.............................................................................................................. 135
9.3 Results ................................................................................................................ 138
9.3.1 Radiographic Predictions .............................................................................. 138
9.3.2 Plantar Force Predictions ............................................................................. 142
9.3.3 Soft-tissue Strains and Joint Contact Force Predictions ............................... 144
9.4 Discussion .......................................................................................................... 146
10. FUTURE DIRECTIONS AND CONCLUSIONS ................................................. 151
Literature Cited .................................................................................................................. 154
Additional Acknowledgements .......................................................................................... 168
APPENDIX A .................................................................................................................... 169
List of Abbreviations ..................................................................................................... 169
General Abbreviations ............................................................................................... 169
Anatomic Abbreviations ............................................................................................ 170
X-ray measure Abbreviations .................................................................................... 171
APPENDIX B .................................................................................................................... 172
STL Characteristics ........................................................................................................ 172
APPENDIX C .................................................................................................................... 174
Ligament Properties ........................................................................................................ 174
APPENDIX D .................................................................................................................... 176
APPENDIX E .................................................................................................................... 177
VITA .................................................................................................................................. 176
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