Deltoid reanimation after axillary nerve injury: Comparing grafts and nerve transfers outcomes.

Abstract

Loss of deltoid function following axillary nerve (AN) injury or upper brachial plexus injury (BPI) severely limits shoulder function. Both interposition nerve grafting and distal nerve transfer are established reconstructive strategies; however, comparative outcome data remain limited. A retrospective single-center study included patients treated between 2006 and 2022 for isolated AN injury or C5-C6 BPI with deltoid paralysis. Exclusion criteria were graft repair performed >8 months after trauma, nerve gaps >7.5 cm, and nerve transfers to the posterior AN branch. Overall, 154 patients with ≥24 months follow-up were analyzed: interposition grafting (Group A, n=67) and medial head triceps motor branch (MHBRn) transfer to the anterior division of the AN (Group B, n=87). The primary outcome was functional deltoid reinnervation, graded using the British Medical Research Council (BMRC) scale at ≥24 months follow-up. Between-group comparisons used the Fisher's exact test; effect sizes were expressed as risk ratios (RR) and absolute risk differences (RD). Functional deltoid recovery (BMRC ≥M3) occurred in 86.2% of Group B versus 50.7% of Group A (RR 1.70, 95% CI 1.32-2.18; RD +35.5%, 95% CI +21.5 to +49.5; p<0.001). Recovery in the transfer group was predominantly high-grade (M4 70.1% and M4+ 10.3%), whereas grafting yielded mainly M3 recovery with rare M4 outcomes (6.0%). Subgroup analyses confirmed a consistent advantage of performing nerve transfer in isolated AN injuries and BPI-associated palsy. MHBRn transfer to the axillary nerve provides a significantly higher likelihood of meaningful deltoid reinnervation compared to interposition nerve grafting at the long-term follow-up, thereby supporting distal nerve transfer as a preferred reconstructive option when a suitable donor is available.