Musculoskeletal Biomechanical Analysis of Brachial Plexus Injury and Treatment

The brachial plexus is a network of nerves that includes the motor neurons that supply the muscles of the upper limb, including muscles that cross the shoulder. Severe injury of the brachial plexus nerves can result in persistent muscle weakness or paralysis, even following extensive surgery and rehabilitation. Bone and postural deformity are additional complications that further compromise upper limb function in children with brachial plexus birth palsy (BPBP). The pattern of injury is highly complex and idiosyncratic across individuals, obfuscating research to improve clinical management of the injury. The objective of this dissertation was to evaluate the biomechanical consequences of brachial plexus injury at the shoulder. Recent advances in computational musculoskeletal modeling and simulation techniques allowed us to compare different nerve transfer surgeries solely based on the biomechanical roles of the muscles they target while controlling for concomitant clinical factors. Traditional motion capture and strength measurement experimental techniques, combined with inverse dynamics analyses, were used to evaluate the dynamics of upper extremity movement in patients with brachial plexus injury. Computational techniques were again used to identify muscles that are mechanically capable of contributing to shoulder deformity in children with BPBP. Having identified muscle candidates of deformity, a rat model of BPBP novel to Wake Forest University was adapted to identify strength imbalance or impaired longitudinal muscle growth as a predominant mechanism of shoulder deformity following BPBP. We found that nerve transfer to the axillary nerve was most likely to restore useful shoulder function than transfer to the suprascapular nerve. For injuries involving the axillary nerve, performing a nerve transfer only to the anterior and middle deltoid compartments can effectively restore useful shoulder function given the limited availability of donor motoneurons. An individual's maximal strength, rather than ability to perform tasks, is a useful way to ensure patients with brachial plexus injury maintain long-term functional ability. Finally, though many muscles are capable of producing deforming shoulder forces for conditions of strength imbalance about the shoulder, shoulder deformity in a rat model of BPBP was most associated with impaired longitudinal muscle growth. These results provide new insights into the biomechanical roles of muscles involved in brachial plexus injury that may help improve the prognosis of brachial plexus injuries.

Grantor dc:publisher

Wake Forest University

Year dc:date.issued

2014

Author dc:creator

• Crouch, Dustin Lee

• brachial plexus

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10339/39387

OAI identifier oai:identifier

oai:wakespace.lib.wfu.edu:10339/39387