Muscle-Tendon Adaptation following Tendon Transfer

Co-Principal Investigators: Wendy M. Murray, PhD and Vincent R. Hentz, MD

Investigators: M. Elise Johanson, MS, PT; Kevin C. McGill, PhD; Zoia C. Lateva, PhD; and Niels Smaby, PhD

Project Category: Spinal Cord Injury - 2005

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 muscle-tendon 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 finalized the imaging and electrophysiological protocols for completing Aims 1 and 2. We collected MR images in 10 able-bodied control subjects, and we collected electrophysiological data from 8 of these control subjects as well. Data analysis is ongoing for these initial data sets that describe the muscle length, cross-sectional area, fiber architecture, and neural innervation of the non-transferred brachioradialis. We identified approximately 15 potential subjects with brachioradialis to flexor pollicis longus transfers and are moving forward in enrolling them in this study.

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.

Funding Source: VA RR&D Merit Review

Funding Status: Active