Variant of the extensor pollicis tertius: a case report on a unique extensor muscle to the thumb

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.

Accessory extensor pollicis longus: A rare tendon anomaly

This report provides a complete review of a rare anatomical variation, the accessory extensor pollicis longus (EPL) tendon and its clinical significance. We will describe a case of an asymptomatic accessory EPL that was found incidentally during surgery with a tendon located in the fourth extensor compartment. Pulling on it induced extension of the thumb interphalangeal joint. Very few cases of accessory EPL have been previously reported with various muscle origins and tendon insertions. In the literature, three symptomatic cases of accessory EPL were reported with a tendon running in a compartment other than the fourth. Although this variation is asymptomatic in most cases, knowledge of its existence might be useful in routine procedures to avoid inadvertent tendon damage, or during tendon repair.