Extensor Digitorum Brevis Manus: A Comprehensive Review of this Variant Muscle of the Dorsal Hand

Abstract

The extensor digitorum brevis manus (EDBM) is a variant muscle located on the dorsum of the hand. This variant of the fourth compartment has often eluded preoperative diagnosis and led to unnecessary repeat visits to the operating room owing to its lack of notoriety. As a result, we aim to review the literature concerning the EDBM with respect to its embryology, comparative anatomy and variants, and clinical significance in an attempt to increase awareness and help in preoperative diagnosis and management. A total of 21 articles were reviewed. The results show that the EDBM often goes underdiagnosed and is frequently discovered incidentally in the operating room or in cadaveric dissections. There are multiple variations of the EDBM that, in certain instances, dictate the correct method of management. While there has been a reversal of opinions on which technique is the most popular at relieving symptoms caused by the EDBM, current arguments stand for retinacular release only when the EDBM serves as a sole extensor for one of the indices. In other instances where this is not the case, surgical excision of the EDBM proved to be the most effective at relieving symptoms.

A Rare Case of Painful Hand Swelling

“…Extensor digitorum brevis manus (EDBM) originates from the extensor surface of the hand/wrist, the most common origin described is either the dorsal metacarpal surface, the distal end of the radius, or the proximal portion of the radiocarpal ligament [ 9 - 10 ]. The muscle is innervated by the posterior interosseous nerve [ 9 - 10 ].…”

“…Extensor digitorum brevis manus (EDBM) originates from the extensor surface of the hand/wrist, the most common origin described is either the dorsal metacarpal surface, the distal end of the radius, or the proximal portion of the radiocarpal ligament [ 9 - 10 ]. The muscle is innervated by the posterior interosseous nerve [ 9 - 10 ]. The insertion of EDBM is of importance in the case of EDBM because of its relation with extensor indicis proprius (EIP), both might have a common insertion which is useful in classifying this muscle.…”

A rare bilateral variation on the dorsum of the hand: extensor digitorum brevis manus and extensor medii proprius

“…These muscles are usually identified through clinical symptoms as chronic pain or swelling on the hand after repeated exercise, and can be misdiagnosed as dorsal wrist ganglion, exostosis, tendon sheath cyst, rheumatoid tenosynovitis or benign tumor mass [4]. However, most EDBM are asymptomatic as in the case here, and their presence is incidentally recognized during hand surgery that was operated to treat other injuries or illnesses.…”

“…The fourth tendon sheath, in most cases, envelop tendons of extensor digitorum (ED) and extensor indicis proprius (EIP) [1]. In literature, numerous reports describe variations of the extensor muscles as well as flexor muscles [23456]. Particularly, supernumerary muscles might be present in this fourth compartment.…”

Finger abduction as a novel function of the extensor digitorum brevis manus muscle

“…The name EDBM was ascribed to the muscle by Macalister in 1875 which has been widely used by authors in the literature [ 9 ]. The EDBM typically originates from the dorsal wrist capsule, the dorsal distal radius, dorsal metacarpal surface or proximal radiocarpal ligament overlying the fourth extensor compartment [ 4 , 14 ]. It can have up to four tendons with the most commonly occurring pattern being a single tendon to the index or middle finger.…”