Located on the dorsal side of the forearm, the extensor pollicis longus muscle inserts into the base of the distal phalanx of the thumb.
The EPL tendon is responsible for extension of the thumb’s distal interphalangeal joint. When a rupture of the EPL tendon occurs, the patient will experience loss of thumb extension.
The EPL tendon is most commonly ruptured due to fractures of the distal radius. The rupture incidence is about 3%. A rupture is more common in undisplaced fractures when compared to displaced fractures.
The extensor pollicis longus muscle is innervated by the posterior interosseous nerve, which branches from the radial nerve. It is important to determine if the loss of thumb extension is due to a tendon rupture or interruption of the posterior interosseous nerve.
The tendon is prone to rupture and increased friction distal to the extensor retinaculum at the Lister’s tubercle. It is more common with undisplaced fractures, due to ischemic rupture or attrition. The rupture usually occurs between 3 weeks and 3 months after the injury.
Treatment:
In rare cases when the rupture is acute a repair will be done. A palmaris longus graft may be used to bridge a gap. A tendon transfer of the extensor indicis proprius (EIP) tendon to the EPL tendon is used for treatment of an EPL rupture (this is the best option).
