Extensor digitorum brevis manus muscle

Extensor digitorum brevis manus is an extra or accessory muscle on the backside (dorsum) of the hand. It was first described by Albinus in 1758.[1] The muscles lies in the fourth extensor compartment of the wrist, and is relatively rare.[2] It has a prevalence of 4% in the general population according to a meta-analysis.[3] This muscle is commonly misdiagnosed as a ganglion cysta, synovial nodule or cyst.[4][5][6]

Extensor digitorum brevis manus
Details
SystemMuscular system
ArteryAnterior interosseous artery
NervePosterior interosseous nerve
Identifiers
LatinMusculus extensor digitorum brevis manus
Anatomical terminology

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.[3] Many variations of the muscle have been described in the literature. It could have up to four tendons with a single tendon inserting to the index or the middle finger being the two most common variations.[7] At the insertion the tendon of the extensor digitorum brevis manus often joins the extensor indicis proprius,[3] although it also occurs when the extensor indicis proprius is absent. It was also reported to coexist with the extensor medii proprius, another anatomical variation in the extensor compartment of the hand.[8] 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.[2] it inserted to the index finger and the middle finger in 77% and 23% of the cases, respectively.[2] 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.[9] The extensor digitorum brevis manus may have been originated from the deep layer, a typical location where most of the variations take place.[2] Some authors believe that this muscle may represent a failure of proximal migration of ulnocarpal elements of the extensor muscle mass in humans.[8][10]

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.[11] 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.[4][5][6]

See also

References
  1. Albinus, BS (1758). "De extensore digitorum brevis manus". Academicarum Annotationum IV: 28–29.
  2. Ranade, AV; Rai, R; Prabhu, LV; Rajanigandha, V; Prakash, Janardhanan JP; Ramanathan, L; Prameela, MD (2008). "Incidence of extensor digitorum brevis manus muscle". Hand (N Y). 3 (4): 320–3. doi:10.1007/s11552-008-9111-5. PMC 2584220. PMID 18780016.
  3. Yammine, Kaissar (2015). "The prevalence of extensor digitorum brevis manus and its variants in humans: a systematic review and meta-analysis". Surgical and Radiologic Anatomy. 37 (1): 3–9. doi:10.1007/s00276-014-1312-8. ISSN 0930-1038. PMID 24849464.
  4. Cavdar, S.; Dogan, T.; Bayramiçli, M.; Sehirli, U.; Yüksel, M. (1998-01-01). "An unusual variation of extensor digitorum brevis manus: a case report and literature review". The Journal of Hand Surgery. 23 (1): 173–177. doi:10.1016/S0363-5023(98)80108-1. ISSN 0363-5023. PMID 9523974.
  5. Ogura, T.; Inoue, H.; Tanabe, G. (1987-01-01). "Anatomic and clinical studies of the extensor digitorum brevis manus". The Journal of Hand Surgery. 12 (1): 100–107. doi:10.1016/s0363-5023(87)80171-5. ISSN 0363-5023. PMID 3805622.
  6. Paraskevas, G.; Papaziogas, B.; Spanidou, S.; Papadopoulos, A. (2014-02-08). "Unusual variation of the extensor digitorum brevis manus: A case report". European Journal of Orthopaedic Surgery & Traumatology. 12 (3): 158–160. doi:10.1007/s00590-002-0035-4. ISSN 1633-8065. PMID 24573895.
  7. Le Double, A.-F. (Anatole-Félix) (1897-01-01). Traité des variations du système musculaire de l'homme et de leur signification au point de vue de l'anthropologie zoologique. Paris, Schleicher frères.
  8. Suwannakhan, A.; Tawonsawatruk, T.; Meemon, K. (2016). "Extensor tendons and variations of the medial four digits of hand: a cadaveric study". Surgical and Radiologic Anatomy. 38 (9): 1083–1093. doi:10.1007/s00276-016-1673-2. ISSN 0930-1038. PMID 27056052.
  9. "The Phylogeny of the Human Forearm Extensors - ProQuest". search.proquest.com. Retrieved 2016-06-04.
  10. Souter, W. A. (1966-09-01). "The extensor digitorum brevis manus". British Journal of Surgery. 53 (9): 821–823. doi:10.1002/bjs.1800530923. ISSN 1365-2168. PMID 5911774.
  11. "A Morphometric Evaluation of Extensor Digitorum Brevis Manus by Dissection: A rare atavistic muscle of the dorsum of hand | Jawaharlal Nehru Medical College". www.jnmc.edu. Archived from the original on 2016-08-07. Retrieved 2016-06-04.
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