Co-Principal Investigators: Wendy M. Murray, PhD and V. Rodney Hentz, MD Co-Investigators: M. Elise Johanson, MS, PT; Kevin C. McGill, PhD, Zoia C. Lateva, PhD; and Niels Smaby, PhD Objective: The aim of this study is to improve the clinical outcomes of tendon transfer surgeries by better characterizing muscle architecture (the length, arrangement, and organization of fibers and tendon within a muscle) and the ability to activate the muscle after transfer. Research Plan: This project has three specific aims: Aim 1: Compare muscle length and cross-sectional area of the transferred brachioradialis and non-transferred brachioradialis. We will estimate these properties from surface reconstructions of the muscle-tendon path obtained using MRI. Aim 2: Compare the fiber architecture of the transferred and non-transferred brachioradialis. We will estimate the locations of the neural innervations and muscletendon junctions using a novel electrophysiological technique. Aim 3: Compare the ability to activate the transferred brachioradialis with and without external stabilization of the elbow and wrist. Work Accomplished: During this project period, we enrolled 7 subjects with tetraplegia and Br-FPL transfers, 4 control subjects with tetraplegia without tendon transfer, and 5 additional nonimpaired controls. We collected MR images in 6 subjects with tetraplegia and Br-FPL and we collected electrophysiological data from 6 Br-FPL subjects; 5 subjects were common to both protocols. MR images were collected in 4 subjects with tetraplegia without tendon transfer and electrophysiology data was also collected from 3 of these subjects. MR and electrophysiology data were collected in all 5 nonimpaired controls; the additional control subjects were recruited to match the age range of the tendon transfer subjects. Over the life of the project we have enrolled 15 nonimpaired control subjects, 7 subjects with tetraplegia and Br-FPL transfers, and 4 control subjects with tetraplegia. Data analysis is ongoing. Two manuscripts describing the anatomy and strength of the nonimpaired subjects were accepted for publication. Four abstracts associated with this work have been presented at scientific meetings in the last year. Expected Outcome: Clinical studies often cite insufficient post-operative muscle strength as the cause of poor surgical outcomes. As such, the most critical determinant of the functional outcome of a tendon transfer is the force-generating capacity of the donor muscle. A muscle’s overall capability to generate force is determined by its architecture and by the nervous system’s ability to activate it. This study will quantify these two critical factors in subjects with transferred muscles. These data will provide objective measures of muscle force-generating capability post-transfer, and will form the basis for the design of rehabilitation interventions to optimize functional outcomes. Publications Holzbaur KRS, Murray WM, Gold GE, and Delp SL. Upper limb muscle volumes in adult subjects. J Biomech 2007, 40:742-749. Holzbaur KRS, Delp SL, Gold GE, and Murray WM. Moment-generating capacity of upper limb muscles. J Biomech (in press). Presentations and Abstracts Holzbaur KRS, Gold GE, Johanson ME, and Murray WM. MRI-based estimation of muscle volume and length following tendon transfer surgery. Abstracts of the 5th World Congress of Biomechanics. Munich, Germany. J Biomech 2006, 39, Supplement 1:S84. Holzbaur KRS, Delp SL, and Murray WM. Moment-generating capacity of upper limb muscles. Abstracts of the 5th World Congress of Biomechanics. Munich, Germany. 2006, J Biomech 39, Supplement 1:S85. Lateva ZC, McGill KC. Architecture of a series-fibered human muscle: EMG study of brachioradialis. Proc 16th Congress Intl Soc Electrophysiol Kinseiol (ISEK), July, 2006. Lateva ZC, McGill KC. Variability of muscle-fiber conduction velocity in normal muscles during voluntary contractions. 28th Intl Congress Clin Neurophysiol, Sept, 2006. Funding Source: Department of Veterans Affairs - Merit Review
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