[A rare insertion variant of the extensor pollicis brevis tendon. A case report].

Two brothers are presented with uni- and bilateral congenital palmar subluxation of the metacarpophalangeal joints of the thumbs as well as extensor lag. A hypoplastic extensor pollicis brevis tendon inserting atypically to the tendon of the extensor pollicis longus at the metacarpophalangeal joint level was found. In each case, arthrodesis of the metacarpophalangeal joint of the thumb was performed. This very rare variation of the insertion of the extensor pollicis brevis tendon is presented, surgical therapy and the pertinent literature reviewed.