Extensor digitorum brevis manus muscle

Structure

The extensor digitorum brevis manus usually originates from the dorsal aspect (backside) of the wrist, either from the joint capsule, the distal end (the most distant end) of the radius, the metacarpal, or from the radiocarpal ligament in the area of the fourth extensor compartment. At the insertion the tendon of the extensor digitorum brevis manus often joins the extensor indicis proprius, The muscle is supplied the posterior interosseous nerve and posterior branch of the anterior interosseous artery.

Variation

The extensor digitorum brevis manus was found to be present in 4% of the population, and there was no correlation between gender, side or ancestry. it inserted to the index finger and the middle finger in 77% and 23% of the cases, respectively. It occurred bilaterally in 26% the total cases.

Development

At some point during the embryonic development, the precursor extensor mass differentiates into three layers: radial, superficial, and deep. The extensor digitorum brevis manus may have been originated from the deep layer, a typical location where most of the variations take place. Some authors believe that this muscle may represent a failure of proximal migration of ulnocarpal elements of the extensor muscle mass in humans.

Functions

It extends the index or the middle finger. It is believed to be a substitute for the extension of the index finger when the extensor indicis proprius is absent.

Clinical significance

Only a few clinical cases have been reported among more than 300 clinical and cadaveric dissections. This implies that the presence of this muscle is usually asymptomatic, although the extensor digitorum brevis manus might cause a painful swelling which can potentially be misdiagnosed as other pathology such as synovial cyst and lipoma.

References

References

1. (1758). "De extensore digitorum brevis manus". Academicarum Annotationum.
2. (December 2008). "Incidence of Extensor Digitorum Brevis Manus Muscle". HAND.
3. (January 2015). "The prevalence of extensor digitorum brevis manus and its variants in humans: a systematic review and meta-analysis". Surgical and Radiologic Anatomy.
4. (January 1998). "An unusual variation of extensor digitorum brevis manus: A case report and literature review". The Journal of Hand Surgery.
5. (January 1987). "Anatomic and clinical studies of the extensor digitorum brevis manus". The Journal of Hand Surgery.
6. (January 2002). "Unusual variation of the extensor digitorum brevis manus: A case report". European Journal of Orthopaedic Surgery & Traumatology.
7. (1897). "Traité des variations du système musculaire de l'homme et de leur signification au point de vue de l'anthropologie zoologique". Schleicher frères.
8. (February 1941). "The Phylogeny of the Human Forearm Extensors". Human Biology.
9. (8 December 2005). "The extensor digitorum brevis manus". British Journal of Surgery.
10. (2012). "A morphometric evaluation of Extensor digitorum brevis manus by dissection: A rare atavistic muscle of the dorsum of hand". Medica Innovatica.