Christopher Glenn Neville. Submitted in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy

Transcription

1 The Effect of Deep Posterior Compartment Muscle Strength on Foot Kinematics, Forefoot Loading, and Function in Subjects with stage II Posterior Tibial Tendon Dysfunction by Christopher Glenn Neville Submitted in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Supervised by Professor Nancy Watson & Professor Jeff Houck School of Nursing University of Rochester Rochester, New York 2008

2 ii Curriculum Vitae The author was born in Syracuse, NY on April 17, He attended Ithaca College from 1995 to 2000, graduating with a Bachelor of Science degree in 1999 and a Master s of Science Degree (Physical Therapy) in The author practiced clinically in the physical therapy field before returning to academics at the University of Rochester in the Fall of He began graduate studies pursuing a degree in Health Practice Research through a collaborative effort between the School of Nursing at the University of Rochester and the Ithaca College Movement Analysis Laboratory. In 2004 the author received the Mary McMillian Doctoral Scholarship from the Foundation of Physical Therapy. In 2006 and 2007 the author was nominated for the Goldner award for abstracts submitted to the American Orthopaedic Foot and Ankle Society meeting. In 2007 the author received a student award from the Gait and Clinical Movement Analysis Society to attend the annual meeting. His research area was investigating the mechanics of the foot and ankle under the mentorship of Associate Professor Jeff Houck and Associate Professor Nancy Watson.

3 iii ACKNOWLEDGEMENTS There are so many people who contributed in various ways to making this work a reality. First, I would like to thank the faculty and staff at Ithaca College who provided a welcome environment for me to complete my research. This work was the result of a collaborative relationship between Ithaca College and the University of Rochester - School of Nursing, made possible with thoughtful and open minded guidance from directors Dr. Earnest Nalette, Dr. Mattie Schmidt, and Dr. Margaret Kearney. I appreciate their hard work and commitment to making the Health Practice Research program a reality. Second, I would like to thank my committee, Dr. Margaret Carno, Dr. Jeff Houck, Dr. Deborah Nawoczenski, and Dr. Nancy Watson who provided constant direction and encouragement during the completion of this project. I cannot acknowledge enough the contribution from Dr. Jeff Houck who above having an unwavering commitment to me and this project also served as a role model for becoming a scholar. I am indebted to him for showing me this path and always being available to make sure I stayed on it. Third, this work would not have been possible without the Foot and Ankle Division of the Department of Orthopaedic Surgery at the University of Rochester and the patients that trusted in their care and guidance. Dr. Sam Flemister provided invaluable time, meeting almost weekly to discuss patients and develop new ideas as this project evolved and was completed. Each study subject also gave generously of

4 iv their time despite no obvious gain. It was a pleasure to meet and work with so many individuals. Last, my bride Laurie who almost 5 years ago entertained my desire to leave clinical practice to return to school with openness and encouragement despite obvious obstacles. She has since been a steadfast person for me to talk with or lean on whenever needed. In the last year of collecting data and finishing this project she has also added the role of raising our daughter to her already full plate of work. Finishing this project with her by my side has made this experience not only easier, but possible and I thank her for her unwavering commitment to me.

5 v Abstract Purpose/Hypothesis: The purpose of this study was to investigate how weakness is associated with foot mechanics and self-reports of function in subjects with stage II posterior tibial tendon dysfunction (PTTD). Materials/Methods: Thirty stage II PTTD subjects (age; 58.1 ±10.5 years, BMI 30.6±5.4) and 15 matched controls (age; 56.5 ±7.7 years, BMI 30.6±3.6) volunteered for this study. Strength testing was completed using a custom device that measured isometric forefoot adduction and ankle inversion. Strength ratios (involved/ uninvolved) were calculated for each subject with strong and weak PTTD groups defined based on comparison to controls. Foot mechanics were assessed with two methods: 1) kinematic data were collected using a multi-segment foot model with an Optotrak Motion Analysis System (Northern Digital Inc, CAN) and Motion Monitor Software (Innsport Training Inc, USA), and 2) plantar loading data were collected using Pedar-X insoles (Novel Inc, St Paul, MN) taped to the bottom of the feet. Selfreported function was assessed using the revised Foot Function Index and the Short- Form Musculoskeletal Functional Assessment tools. Results: The strength ratio averaged 1.06±0.1 (range ) for controls and a 20% deficit (weakness) was used as a cut-off for weakness: PTTD strong (average 1.06±0.1, range ), PTTD weak (average 0.64±0.2, range ). Significant differences in foot mechanics were associated with strength. Subjects with PTTD who were weak demonstrated significantly greater flatfoot deformity and altered plantar loading patterns compared to subjects with PTTD who were strong and

6 vi controls. Subjects with PTTD who were strong demonstrated greater flatfoot deformity compared to controls but no difference in plantar loading patterns. Strength was not associated with self-reported function or pain. Conclusions: Deep posterior compartment strength is associated with foot mechanics as evidenced by greater flatfoot deformity and altered plantar loading patterns in subjects who are weak. Surprisingly, flatfoot deformity in subjects with PTTD who are strong suggests factors other than strength may also play a role in flatfoot deformity. A pre-existing flatfoot posture may be present without a strength deficit due to congenital flatfoot posture. Clinical Significance: Treatment outcomes may be different for subjects with stage II PTTD who are weak and those who are strong.

7 vii Table of Contents Chapter 1: The Impact of Posterior Tibial Tendon Dysfunction Specific Aim 1: Strength and Foot Kinematics Specific Aim 2: Strength and Forefoot Loading Specific Aim 3: Contributing Factors to Forefoot Loading Specific Aim 4: Strength and Functional Ability Chapter 2: Background and Current Concepts in Posterior Tibial Tendon Dysfunction (PTTD) Clinical Epidemiology of PTTD Diagnosis of PTTD Clinical Classification Schemes for PTTD Pathogenesis in PTTD Strength and Function in Subjects with stage II PTTD Clinical Management of PTTD Pathomechanics of PTTD Preliminary Studies Chapter 3: Strength Assessment in subjects with stage II PTTD Design/Sample Function Questionnaires Kinematics and Force Plate Recordings Kinematic Model Procedures for Foot Kinematics

8 viii Foot Loading Recording Isometric Test of Ankle Inversion and Foot Adduction Strength Procedures for Isometric Strength Testing Statistical Analysis Sample Size Justification Chapter 4: Results Sample Characteristics and Deep Posterior Compartment Strength Deep Compartment Strength Strength and Flatfoot Kinematics: Specific Aim 1 Strength and Forefoot Loading: Specific Aim 2 Predictions of Forefoot Loading: Specific Aim 3 Strength and Self-Report of Pain and Function: Specific Aim 4 Chapter 5: Discussion Strength and PTTD Strength and Foot Kinematics Plantar Loading- Specific Aim 2 Predicting Plantar Loading- Specific Aim 3 Deep Posterior Compartment Strength and Self-Reported Function Future Studies Conclusions References Appendix I

9 Appendix II 137 ix

10 x List of Tables Table Title Page TABLE 1.1 Key terminology 4 TABLE 2.1 Muscle Architecture and Pathology related to PTTD 24 TABLE 2.2 In-vitro foot kinematics related to PTTD 44 TABLE 3.1 Screening criteria for subjects with PTTD 47 TABLE 3.2 TABLE 3.3 TABLE 4.1 TABLE 4.2 TABLE 4.3 TABLE 4.4 Screening criteria used to establish unilateral flatfoot deformity Calculations for power analysis on foot kinematic measures at the pre-swing phase of stance Subject classification variables for subjects with stage II PTTD and matched controls. Values expressed as means±sd. P values represent comparisons between PTTD groups and Control group using a one-way ANOVA Test re-test reliability for 11 control and 11 posterior tibial tendon dysfunction (PTTD) subjects. Units are in Newtons Means and SD of kinematic variables across the stance phase of gait Means (% BW) and SD of loading in areas of the plantar foot (masks) at the terminal stance phase of gait

11 xi TABLE 4.5 TABLE 4.6 List of dependent and independent variables to be used in the regression models to predict loading patterns in subejcts with PTTD Pearson Correlations and significance levels for each of the predictor variables and each dependent loading variable

12 xii List of Figures Figure Title Page FIGURE 1.1 FIGURE 2.1 a. Anatomy of the leg with attention to the course of the Posterior Tibialis Muscle. b. Cross-sectional view of the leg identifying the Deep Posterior Compartment Muscles. Foot Fall events used to define the phases of Stance (adapted from Perry, 1992) FIGURE 2.2 Changes in posterior tibialis muscle length ( PTLength ) 39 FIGURE 2.3 FIGURE 2.4 for the Posterior Tibial Tendon Dysfunction (PTTD) and control groups across three rockers of stance. Dotted lines represent ±1 SD. PTLength in the subtalar neutral (STN) position represents zero. * Indicates midpoint of each rocker where significant differences occurred between groups. Scores on the Function Index and the Mobility subscale of the Musculoskeletal Functional Assessment Questionnaire in subjects with Posterior Tibial Tendon Dysfunction (PTTD). * Indicates significant (p<0.05) differences between groups using a two sample t test. Sagittal plane ankle power during the stance phase of gait. * Indicates significant difference between groups (alpha=0.05)

13 xiii FIGURE 3.1a FIGURE 3.1b Standardization jig used for evaluating the too-many-toes sign in subjects with PTTD. Clinical method of counting toes seen on lateral side of foot and hindfoot eversion measured on standing pictures FIGURE 3.2 Testing jig used to calculate the Arch Index. 50 FIGURE 3.3 Infrared emitting diodes (IREDs), location and anatomic coordinate systems used to model foot kinematics. 55 FIGURE 3.4 Medial Longitudinal Arch (MLA) Angle. 56 FIGURE 3.5 FIGURE 3.6 FIGURE 3.7 FIGURE 3.8 Identification of plantar pressure masks with subject specific anatomic landmarks A. Picture of subject and instrumentation for isometric ankle inversion and foot adduction strength testing. B. Display of peak force (converted from volts) and electromyography (EMG) collected from the tibialis anterior muscle of a single maximum effort. The peak-topeak EMG signal is compared to the peak-to-peak maximum voluntary contraction (MVC) signal determined prior to the test. ANOVA model used for hypothesis testing in specific aim 1. Forefoot abduction at the midpoint of terminal and preswing phases of gait. Beta s are calculated if current trends

14 xiv are maintained with a proposed sample of 15 subjects per group. FIGURE 3.9 FIGURE 4.1 FIGURE 4.2 FIGURE 4.3 FIGURE 4.4 Medial Longitudinal Arch height at the midpoint of terminal and pre-swing phases of gait. Beta s are calculated if current trends are maintained with a proposed sample of 15 subjects per group. Deep Compartment strength in each lower extremity with controls randomly assigned an involved side for comparison. Comparison of raw strength values (N) by side irrespective of involvement in the PTTD group. No significant difference was observed between sides in either the PTTD group or controls. Strength ratio calculated as involved divided by uninvolved side in each group. Strength ratio calculated as involved divided by uninvolved side in each group for each subject. Groups are defined based on strength profile with a weak PTTD group demonstrating a greater than 20% deficit in strength in their involved side while the strong group demonstrates a less than 20% deficit

15 xv FIGURE 4.5 FIGURE 4.6 FIGURE 4.7 FIGURE 4.8 Average strength ratio calculated as involved divided by uninvolved side in each group. Groups are defined based on strength profile with a weak PTTD group demonstrating a greater than 20% deficit in strength in their involved side while the strong group demonstrates a less than 20% deficit. Medial Longitudinal Arch pattern across the stance phase of gait for the posterior tibial tendon dysfunction (PTTD) weak, PTTD strong and comparison control group. Error bars represent ±1 SD. Subtalar neutral position (STN) is the zero reference position. Lateral forefoot pattern across stance with the lateral FF segment relative to the hindfoot for the posterior tibial tendon dysfunction (PTTD) weak, PTTD strong and comparison control group. Error bars represent ±1 SD. Subtalar neutral position (STN) is the zero reference position. Hindfoot eversion/inversion pattern across the stance phase of gait for the posterior tibial tendon dysfunction (PTTD) weak, PTTD strong, and comparison control group. Error bars represent ±1 SD. Subtalar neutral position (STN) is the zero reference position FIGURE 4.9 Results of two-way ANOVA model investigating three 83

16 xvi FIGURE 4.10 FIGURE 4.11 FIGURE 4.12 FIGURE 4.13 groups (Control, PTTD strong, and PTTD weak) across two different loading areas of the forefoot (medial and lateral FF) during the terminal stance phase of gait. Total loading was entered as a covariate in the model. Values represent Means for each group with error bars (1 SD) for the control group. Mean total and distributed loading by mask for three groups (PTTD strong, PTTD weak and Controls) at terminal stance. * Indicates significant difference (p<0.05) in loading between groups for that mask. Scatter plot of independent variable, MLA angle, and dependent variable, lateral forefoot loading, demonstrating that as lateral forefoot loading increases the MLA angle decreases (higher MLA). Scatter plot of independent variable, MLA angle, and dependent variable, midfoot+heel loading, demonstrating that as midfoot+heel loading increases the MLA angle increases (lower MLA). Group comparisons for the functional self-report measures. The Foot Function Index Revised scale and the Short Form of the Musculoskeletal Functional Assessment scale were completed on all subjects with Posterior Tibial Tendon

17 xvii Dysfunction. FIGURE 4.14 Results of the two-way ANOVA model investigating the interaction between pain and function in subjects with stage II Posterior Tibial Tendon Dysfunction. 89