Autologous nerve grafting versus multiple nerve transfers for upper trunk brachial plexus injury: a rat model study

Upper trunk(C5-C6) injuries of brachial plexus impair shoulder abduction and elbow flexion. For C5-C6 ruptures with preserved proximal stumps, nerve grafting (NG) remains the conventional approach. Nerve transfers (NT) represent the sole viable option in C5-C6 avulsions. The current global standard for NT involves triple transfer procedures: spinal accessory nerve (SAN) to suprascapular nerve(SSN), ulnar nerve fascicle to the biceps branch of musculocutaneous nerve (Oberlin procedure), and the nerve to the long head of the triceps to the anterior branch of the axillary nerve (Leechavengvongs procedure). Recent clinical trends indicate a broadening of NT indications to include root rupture scenarios, driven by the rationale that distal NT significantly shorten axonal regeneration distance. To enable direct comparison, this study established two rat models simulating these clinical strategies: 1) an NG model where the C5-C6 stumps were grafted to the SSN and upper trunk; 2) a multiple NT model comprising the above three procedures. Functional recovery (Ochiai score, Barth foot-fault test, and Terzis grooming test), electrophysiological parameters and regenerated sensory axon counts were evaluated at 8 and 16 weeks postoperatively. At 8 weeks, no statistically significant differences existed in functional outcomes between groups. By 16 weeks, while Ochiai scores and Terzis results remained comparable, NG demonstrated significantly superior performance on the Barth test. Electrophysiologically, NT exhibited significantly better recovery rates for musculocutaneous, axillary and suprascapular nerves at 8 weeks. However, these electrophysiological advantages were no longer statistically significant by 16 weeks. At 8 weeks, NG already carried more regenerated sensory axons in musculocutaneous and axillary nerves, while SSN counts were similar. By 16 weeks NG surpassed NT in sensory axon numbers for all three nerves. These findings indicate that for C5-C6 root ruptures, NG achieves comparable functional and electrophysiological recovery to NT, while yielding superior restoration of sensory and coordinated motor function.