Variant composition of extensor digitorum co-existent with the absence of extensor indicis

Ruchi Dhuria

Abstract

The human extensor tendons of hand often display an array of variations. Routine preclinical educational dissection revealed anomalous arrangement of extensor tendons in the left hand of an adult male cadaver. The extensor digitorum muscle was hypoplastic; there was no contribution to the index and the little fingers. It showed two parts, as lateral and medial. The lateral part was preponderantly tendinous, and divided into a thicker radial and a thinner ulnar slip. Both the slips eventually traversed towards the middle finger and formed its extensor digital expansion. The medial part of extensor digitorum was fleshy. It became tendinous as it approached the extensor retinaculum and formed the dorsal digital expansion of the ring finger. Strikingly, there was absence of extensor indicis muscle. The presence of an accessory muscle having an aponeurotic origin from the dorsal upper surface of the radius was another unique aspect of this study. This accessory muscle contributed to the extensor digital expansion of the index finger. The morphology of the other extensor muscles was as usual. We endeavor to discuss the relevance of embryogenesis with respect to the extensor tendons and highlight the possible clinical repercussions. Although extensor muscles of hand exhibit a number of variations, each merit documentation as the clinician is required to evaluate each case on an individual basis.