Study of morphology, phylogeny, classification and clinical relevance of extensor digitorum brevis manus

Introduction and objectives : Variations in structures of hand are of clinical and surgical importance. A rare variation of the extensor musculature on the dorsum of hand is extensor digitorum brevis manus (EDBM). Presence of EDBM on the dorsum of hand can be confused for many dorsal hand mass lesions. In the present cadaveric study, an attempt was made to delineate the anatomical morphology and morphometry of EDBM and evaluate its phylogenetic significance and clinical relevance. Methodology: Study was conducted on 78 human hands in the department of anatomy. A longitudinal incision was performed on the dorsum of hand along the axis of middle finger, skin flaps were raised both on radial and ulnar side. A transverse incision was taken at metacarpophalangeal joints from second to fifth fingers. Results: We found EDBM in two incidences. In both the cases it was extending from the distal end of radius, dorsal aspect of wrist joint and from the extensor indicis tendon. Muscle was medial to extensor indicis tendon. Insertion was into the dorsal digital expansion of middle finger. In both the cases it was classified as type III anatomical variety. Conclusion: Appreciation of such variant muscle on the dorsum of the hand is of great significance during clinical and surgical evaluation of mass lesions on the dorsum of hand. Key words: Extensor digitorum brevis manus; dorsum of hand; variations.