Radial to Median Sensory Nerve Transfers to Restore Sensate Key Pinch: A Cadaveric Assessment of Size Match and Implications for Transfer.

Background: Loss of key-pinch sensation after median nerve injury poses significant functional detriment. Nerve transfers are utilized to improve function after nerve injury and size matching of donor and recipient nerves is important to optimize success. This anthropometric study investigates the anatomy of the superficial branch of the radial nerve (SBRN) to the thumb and index finger and explores radial to median sensory nerve transfers, a necessary but not heavily discussed facet of nerve transfers for the hand.

Methods: Anatomic dissection of SBRN in 15 cadaver hands was performed to assess variability in diameter and branching patterns based on nerve location. Dissection of the index radial and thumb ulnar digital nerves was performed to assess diameter based on location and calculate ideal size match for nerve transfer.

Results: All specimen thumbs had 2 SBRN branches at the level of the metacarpal shaft and proximal phalanx; 87% had 2 index SBRN branches extending to the proximal phalanx. Index radial and ulnar SBRN branches were similar in diameter at all levels (p > 0.0167). There was a significant size mismatch between the individual SBRN branches and index digital at all measured levels (p < 0.0167). The thumb radial SBRN was significantly larger than ulnar SBRN (p = 0.006).

Conclusions: Optimal size match for transfer involved transection of radial index SBRN 1 cm distal to the MCP joint and ulnar thumb SBRN 1 cm distal to the MCP joint. Consideration should be made for transfer of both index SBRN branches at the level of the MCP joint to improve size match. Corresponding digital nerves were transected 1 cm proximal to the level of SBRN harvest.