Principal Investigator: Wendy M. Murray, PhD Co-Investigators: Garry E. Gold, MD; V. Rodney Hentz, MD; M. Elise Johanson, MS, PT; Zoia C. Lateva, PhD; Kevin C. McGill, PhD; Niels Smaby, PhD; and Anca Velisar, MS 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 structural and functional changes that take place in transferred muscle, and to more accurately model the impairments associated with the surgically altered tetraplegic limb. Research Plan: This project has four specific aims: Aim 1: A computer simulation of the Br-FPL transfer will characterize the clinical ideal, in which the transferred muscle has normal strength and is maximally activated for its new function. Aim 2: The nominal model will be personalized to represent 8-10 surgical candidates based on pre-operative assessments of Br cross-sectional area obtained from medical imaging, and elbow and wrist extension strength. Aim 3: The transferred Br will be re-imaged and a novel electrophysiological technique will be applied in the same subjects who were studied pre-operatively to identify postoperative changes to muscle and fiber architecture. Aim 4: The ability to fully activate the transferred Br during lateral pinch will be quantified in the same subjects. The personalized simulations will be further refined based on the data collected in Aims 3 and 4. Work Accomplished: A total of 10 subjects have been enrolled in this study since its onset; three additional candidates are scheduled for surgery in early 2007 and are willing to participate. A manuscript describing our model of the Br-FPL tendon transfer was published in the Journal of Bone and Joint Surgery, a second manuscript describing computer simulations of the mechanical behavior of the passive upper limb is in preparation. The results from our simulations of the passive limb were also presented at the BMES meeting in October. Expected Outcome: This work will identify and characterize which factors need to be incorporated into a biomechanical model to accurately predict surgical outcome of the Br-FPL transfer. In doing so, the factors responsible for disappointing surgical outcomes will be better understood, which will lead to better treatment decisions. Publications Murray WM, Hentz VR, Fridén J, Lieber RL. The significance of surgical attachment length for hand and wrist function following brachioradialis tendon transfer. J Bone Jt Surg. 2006, 88:2009-2016. 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 Velisar, A., Murray, W. M. (2006) Passive joint coupling in the upper limb: multiarticular muscle function in the forearm and hand. Podium presentation at the BMES 2006 Annual Meeting, Chicago, IL. October 11-October 14th. 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. Funding Source: NIH
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