Modified Partial Radial to Axillary Nerve Transfer as the Index Procedure for Isolated Axillary Nerve Injury.

OBJECTIVE: Axillary nerve injuries often produce profound functional deficits. Beyond expectant management or microsurgical repair, treatment is generally limited to salvage procedures. We present the results of partial radial-to-axillary nerve transfer as the index procedure for treatment of axillary nerve injury after failure of initial conservative management.

METHODS: Minimum 2-year follow-up data was collected and retrospectively analyzed for this single-surgeon cohort of patients with isolated axillary nerve injury. The injury was confirmed with electromyography (EMG), and all patients underwent a nerve transfer as the index intervention. All patients were evaluated for donor-site neuromuscular morbidity, and deltoid muscle biopsies were obtained intra-operatively from 8 patients for motor endplate (MEP) morphometric analysis. Age at time of surgery ranged from 22-68 years, and time from injury to surgery ranged from 2-120 months. Shoulder range of motion (ROM) and Medical Research Council (MRC) muscle strength scores were recorded pre-op and post-op.

RESULTS: There were 16 patients in the final sample (median age 56, 15 males, 1 female, 93.75% White, 6.25% Black). Significant improvements in pre-op versus final post-op function were observed: average MRC score improved by 2.82± 1.33 (p<0.01), while average active forward- flexion improved by 108.18 ± 44.17° (p < 0.01), abduction by 94.91 ± 41.58° (p < 0.01), and external rotation by 36.67 ± 27.04° (p < 0.01). Surviving MEPs were observed in biopsies of denervated muscles from all patients, even those greater than 6 months from injury.

INTERPRETATION: In patients with an isolated axillary nerve injury, when an appropriate donor radial nerve branch can be identified, partial radial-to-axillary nerve transfer as the index treatment procedure offers the possibility of significantly improving shoulder motion and functional strength, without detectable donor-site morbidity. Furthermore, the opportunity for meaningful functional improvement was observed even in patients treated with surgery beyond 6 months from the time of nerve injury and correlated with the observed persistence of deltoid MEPs at later time points.

LEVEL OF EVIDENCE: Level IV, Case Series, Treatment Study.