Mohammed H. Karrar Alsharif; Mamoun A. Alfaki; Abubaker Y. Elamin; Elbagir H. Manssor; Khalid M. Taha; Emad M. Arafa & Khalid Hadi M. Aldosari

Variation in the morphology of the extensor pollicis longus muscle is very rare. The muscle is considered as one of the deep group of dorsal forearm muscles. It passes through the dorsal radiocarpal ligament in a detached compartment. It inserts at the base of the distal phalanx of the thumb. The muscle might have double tendons where they run either in one, or in separate compartments. In this study, we report an extremely rare condition for a 38-year-old male where some of the tendon fibers split at the base of the proximal phalanx and the two tendons insert at the sides of the base of the distal phalanx. We also noticed a high range of hyperextension where the action was painless and showed no sign of discomfort. We believe that the way the tendons get inserted might have a role in this wide range of extension.

KEY WORDS: Extensor pollicis longus; Tendon; Interphalangeal joint, hyperextension; Angle of motion.

ALSHARIF, K. M. H.; ALFAKI, M. A.; ELAMIN, A. Y.; MANSSOR, E. H.; TAHA, K. M.; ARAFA, E. M. & ALDOSARI, K. H. M. An accessory extensor pollicis longus tendon: A case report of rare anatomical variant. Int. J. Morphol., 35(4):1276-1279, 2017.