Supplmentary material: Utility of intraoperative neurophysiological monitoring in donor fascicle localization during nerve transfers for elbow flexion: relationship between FCU CMAP amplitude and biceps brachii reinnervation Video S1. Donor fascicle selection. Intraoperative neurophysiological mapping during selective ulnar to musculocutaneous nerve transfer (Oberlin technique). Fascicle by fascicle ulnar nerve stimulation with CMAP recording from FDI, ADM, and FCU is shown, followed by donor fascicle selection based on predominant FCU response. Abbreviations: CMAP, compound muscle action potential; FCU, flexor carpi ulnaris; FDI, first dorsal interosseous; ADM, Abductor digiti minimi. Other material: Table S1: Baseline demographic and clinical characteristics of the analytical cohort and stratified by injury level Table S2: Intraoperative Donor Fascicle Characteristics