Variations of abductor pollicis longus and extensor pollicis brevis muscles: surgical significance

To investigate variations of the abductor pollicis longus and the extensor pollicis brevis muscles, an anatomic study was performed on 15 cadaver forearms. Some variations were observed as reported in previous studies. An unusual insertion of the abductor pollicis longus muscle and the extensor pollicis brevis muscle also was encountered during the dissection. Both tendons of these muscles were found to have inserted into the inferior side of the base of the first metcarpal bone together, instead of dorsal side. Our study suggested that the extensor pollicis brevis muscle and the abductor pollicis longus muscle differentiate from a common muscle.