ELECTROPHYSIOLOGIC ISOLATION OF ULNAR NERVE FASCICLES INNERVATING FLEXOR CARPI ULNARIS IN OBERLIN NERVE TRANSFER SURGERY

摘要

Introduction: Oberlin nerve transfer, which utilizes an ulnar nerve fascicle as the donor nerve and the biceps branch of the musculocutaneous nerve as the recipient, is commonly used to restore elbow flexion following upper brachial plexus injury. Selectively transferring a fascicle that only innervates flexor carpi ulnaris (FCU) may be beneficial for risk reduction, as partial loss of FCU function is functionally less significant than loss of ulnar-innervated hand intrinsic function. We describe the use of intra-operative neurophysiology to isolate fascicles only innervating the FCU. Methods: Between 2018 and 2020, 10 cases of Oberlin nerve transfer were reviewed. Individual nerve fascicles were pulled away from surrounding ulnar fascicles and stimulated with a monopolar or tripolar hook stimulator. Intensity ranged from 0.04-0.50 mA, pulse duration (PD) from 100-250 ms, and frequency from 2.1-5.1 Hz. Compound muscle action potentials (CMAPs) were recorded from the FCU, abductor digiti minimi (ADM), first dorsal interosseus (FDI), and adductor pollicis (AP) muscles. CMAPs from stimulation in all recorded muscles were confirmed at other sites. Fascicles where FCU was isolated or that had minimal CMAPs from the ADM, FDI, and AP were selected for transfer by the surgeon. Results: Patients (9 male and 1 female) ranged from 8 months to 79 years of age. All patients had at least upper trunk brachial plexus injuries. 90 of injuries were due to trauma. In 5 cases FCU CMAPs were isolated after single fascicle stimulation. Difference in PD (p = 0.15) and frequency of stimulation (p = 0.18) between cases with and without isolation was not significant. Conclusion: With low stimulation intensities, it is possible to isolate ulnar nerve fascicles that only innervate FCU. This technique may help minimize risk associated with Oberlin nerve transfer, while maximizing the potential for functional recovery.