Accessory Extensor Pollicis Longus Tendon Incidentally Discovered During Dorsal Distal Radius Plating.

Anatomical variations of the extensor pollicis longus (EPL) tendon are rare. Variations are typically asymptomatic, yet knowledge of these variations poses significance in the setting of dorsal approaches to wrist surgery. We present a case of an accessory EPL tendon that was discovered intraoperatively in the fourth dorsal compartment during open repair of a distal radius fracture with a dorsal spanning plate. If not correctly identified, the accessory EPL could have been entrapped beneath the plate, resulting in limited thumb extension and potentially tendon rupture.