The recurrent (thenar motor) branch of the median nerve is the critical motor branch arising from the median nerve at or just distal to the flexor retinaculum, curving back (recurrently) to supply the three thenar muscles: abductor pollicis brevis (APB), flexor pollicis brevis (superficial head, FPB), and opponens pollicis. It provides the motor innervation essential for thumb opposition. Its origin varies: extraligamentous (55%), subligamentous (31%), or transligamentous (14%).
The recurrent branch is the most critical nerve to identify and preserve in carpal tunnel release (CTR) surgery. Inadvertent division of the recurrent branch during CTR produces permanent thenar muscle paralysis and loss of thumb opposition — a catastrophic complication. The safe zone in open CTR is ulnar to the axis of the ring finger to avoid the recurrent branch as it curves from the median nerve to the thenar muscles. The transligamentous variant runs through the flexor retinaculum itself and is vulnerable to blind hook knife release in endoscopic CTR. Thenar muscle wasting indicates chronic recurrent branch compression within the carpal tunnel.
Inadvertent division of the thenar motor branch during carpal tunnel release produces permanent loss of thumb opposition from APB and opponens denervation — one of the most serious complications of hand surgery; the safe zone in open CTR is a vertical line ulnar to the axis of the ring finger, and the transligamentous variant must be sought before any blind release technique.
