Supernumerary extensor pollicis longus tendon: a case report.

We report a rare case in which the extensor pollicis longus (EPL) tendon was separated into 2 slips at the site of origin, ran an abnormal course across the wrist, and combined in the vicinity of the metacarpophalangeal (MCP) joint; the tendon on the radial side passed through another tendon sheath between the first and second compartments and the tendon on the ulnar side passed over the extensor retinaculum.