Investigators: V. Rodney Hentz, MD and Felix E. Zajac, PhD Project Staff: Francisco J. Valero-Cuevas, PhD; M. Elise Johanson, MS, PT; Inder Perkash, MD; Charles G. Burgar, MD; Kevin C. McGill, PhD; H.F. Machiel Van der Loos, PhD; Deborah E. Kenney, MS OTR; Joseph D. Towles, MS; and Niels Smaby, MS Project Category: Spinal Cord Injury - 2000 Advances in surgical reconstructive techniques for restoring hand function in quadriplegia require a better understanding of the complex mechanical operation and coordination of the muscles that control the hand. The objective of this project is to develop a computer model of the thumb and index finger in grasping tasks to quantitatively study how changes in the musculoskeletal system arising from quadriplegia contribute to deficits in functional grasping. The ability to quantify key- and tip- pinch capability in the pre- and post-operative hand is critical to the evaluation of the functional benefit of alternative treatments. A 3D computer biomechanical model of the index finger and thumb has been developed. Finger and thumbtip forces with simultaneous recording of EMG signals from all of the finger and thumb muscles have been recorded to validate the model. Cadaveric studies of index finger muscles have been used to investigate the effects of a proposed modification to the Zancolli lasso surgical procedure, and to quantify the reduction in fingertip force that can be attributed to paralysis associated with low radial and ulnar nerve paralysis. The existing robotic technology, used to record finger and thumbtip forces, has been expanded to provide interactive "virtual" simulation of pinch tasks. A new clinical assessment device has been developed to make quantitative assessments of pinch deficits in individuals with quadriplegia. Pinch function will be measured pre- and post operatively using 3 parameters; grasp opening, magnitude of pinch force and ability to direct force. The findings from this study will assist in targeting specific muscles for rehabilitation and evaluating the efficacy of surgical reconstructive procedures. Publications: Results from this project have been disseminated in the form of eight conference abstracts and presentations and three journals articles since 1998. Three selected articles are: Valero-Cuevas FJ, Towles JD, Hentz VR: Quantification of fingertip force reduction in the forefinger following simulated paralysis of extensor and intrinsic muscles. J Biomech, In press. Valero-Cuevas FJ: Predictive modulation of muscle coordination pattern magnitude scales fingertip force magnitude over the voluntary range. J Neurophysiol 83(3):1469-1479, 2000. Valero-Cuevas FJ, Zajac FE, Burgar CG: Large index-fingertip forces are produced by subject-independent patterns of muscle excitation. J Biomech 31(8):693-703, 1998. Funding Source: VA Medical Merit Review |
