Principal Investigator: Wendy M. Murray, PhD Project Staff: Garry E. Gold, MD; Vincent R. Hentz, MD; M. Elise Johanson, MS, PT; Zoia C. Lateva, PhD; Kevin C. McGill, PhD; and Niels Smaby, MS Project Category: Spinal Cord Injury - 2003 Objective: This study will attempt to develop better biomechanical models for predicting the outcome of brachioradialis-to-flexor-pollicis-longus (Br-FPL) tendon transfer, a procedure that restores lateral pinch following tetraplegia. We hypothesize that the effectiveness of the transferred brachioradialis is impaired because of post-operative muscle adaptations and weakness of elbow and wrist extensors. The specific aim of this study is to characterize the sturctural and functional changes that take place in transferred muscle, and to more accurately model the impairments associated with the surgically altered tetraplegic limb. Aim 1 will define the maximum potential of the Br-FPL transfer to produce lateral pinch force. A nominal model of the transfer will characterize the clinical ideal, in which the transferred muscle has nominal strength and can be maximally activated for its new function. Our previous work suggests that this model will substantially overestimate actual pinch forces measured in subjects who have had transfers. Aim 2 will determine the extent to which pre-operative weakness limits force production. Personalized simulations of Br-FPL tendon transfers will be developed for 8-10 surgical candidates based on pre-operative assessments of Br cross-sectional area, obtained by medical imaging, and elbow and wrist extension strength. These models should predict pinch force better than the nominal model. Aim 3 will identify post-operative changes to muscle and fiber architecture. The transferred Br will be re-imaged and a novel electrophysiological technique will be applied. It is expected that the transferred muscle will have reduced cross-sectional area and lack distal bands of muscle fibers, and that models incorporating these differences will lead to even better predictions of actual outcomes. Aim 4 will test the ability to fully activate the transferred Br during lateral pinch. EMG during maximum voluntary effort for pinch is expected to be less than EMG during maximum resisted elbow flexion (Br's original function), in part due to lack of wrist and elbow extension strength needed for joint stabilization. This work will identify and characterize factors responsible for disappointing surgical results, and this better understanding will lead to better treatment decisions. Funding Source: NIH Funding Status: Submitted |
