Spinal Accessory Nerve Versus Intercostal Nerves in Gracilis Free-Functioning Muscle Transfer for Elbow Flexion in Adult Brachial Plexus Patients.

Purpose: Traumatic brachial plexus injury may cause either partial or complete loss of arm function. Surgical reconstruction of elbow flexion using a gracilis free-functioning muscle transfer (FFMT) may be necessary. The donor nerve, which could be the spinal accessory nerve (SAN) or intercostal nerves (ICN), can affect the final muscle strength, but little is known about how they affect voluntary neuromuscular control. This study aimed to examine the differences in voluntary neuromuscular control of the FFMT gracilis reinnervated by either SAN or ICN using biomechanical measures.

Methods: Patients with a gracilis FFMT for elbow flexion innervated with SAN or ICN (2-3 motor nerves) were studied. The voluntary control of their gracilis-produced elbow flexion was evaluated on a previously validated apparatus. Subjects were instructed to produce a predefined torque relative to their maximum elbow flexion torque. Objective measures of neuromuscular control, including elbow flexor contraction latency, relaxation latency, and duration of successfully achieved demanded torque, were studied.

Results: Twenty-two subjects were identified, 12 with SAN and 10 with ICN as the donor nerve to reinnervate the FFMT gracilis muscle for elbow flexion. The SAN group displayed a similar ability to contract and a better ability to relax elbow flexion produced by the gracilis muscle compared with the ICN group. The SAN group also demonstrated better modulation in their hold times with an increase in torque demand compared with the ICN group.

Conclusions: This study demonstrated the superior neuromuscular control of SAN over ICN for control.

Type of study/level of evidence: Therapeutic IV.