Extensor medii proprius muscle

The extensor medii proprius (so called the extensor digiti medii) is a rare anatomical variant in the extensor compartment of the forearm. The aberrant muscle is analogous to the extensor indicis with the insertion being the middle finger instead of the index finger.

Extensor medii proprius
Extensor medii proprius (EMP)
Details
Originposterior distal third of ulna and interosseous membrane
Insertionmiddle finger (extensor hood)
Arteryposterior interosseous artery
Nerveposterior interosseous nerve
Actionsextends middle finger
Identifiers
Latinmusculus extensor digiti medii proprius
Anatomical terms of muscle

Structure

The extensor medii proprius originates from the distal third of ulna near the extensor indicis and the adjacent interosseous membrane. It passes through the fourth extensor compartment along with the extensor indicis and the extensor digitorum. It inserts to the extensor expansion of the middle finger usually on the ulnar side of the tendon of the extensor digitorum of the middle finger,[1] though, insertion deep to the extensor digirorum tendon was seen.[2] Insertion to the fibrous tissue proximal to the metacarpophalangeal joint of the middle finger was also reported.[3]

Prevalence

The reported incidence of the extensor medii proprius in cadaveric dissections ranges from 0% to 12%.[4][5][6][7] Meta-analysis showed that the prevalence of this muscle was significantly higher in North American and Japanese populations than European and Indian populations.[8]

Function

The extensor medii proprius extends the middle finger. The presence of this anomalous muscle results in a more independent movement of the middle finger.

Clinical significance

The extensor medii proprius is unlikely to cause symptoms.[9][10] However, awareness of this anomalous muscle may help physicians for identification and for proper planning of surgery.[11]

Additional Images
  • Extensor indicis proprius (EIP) and extensor medii proprius (EMP)

See also

References
  1. Tan, Swee T.; Smith, Paul J. (1999). "Anomalous extensor muscles of the hand: A review". The Journal of Hand Surgery. 24 (3): 449–455. doi:10.1053/jhsu.1999.0449. PMID 10357521.
  2. Li, Jing; Ren, Zhen Feng (2013). "Bilateral extensor medii proprius with split tendon of extensor indicis proprius, a rare anatomical variant". Romanian Journal of Morphology and Embryology = Revue Roumaine de Morphologie et Embryologie. 54 (3): 639–641. ISSN 1220-0522. PMID 24068417.
  3. von Schroeder, H. P.; Botte, M. J. (November 1991). "The extensor medii proprius and anomalous extensor tendons to the long finger". The Journal of Hand Surgery. 16 (6): 1141–1145. doi:10.1016/s0363-5023(10)80081-4. ISSN 0363-5023. PMID 1748763.
  4. Hirai, Y.; Yoshida, K.; Yamanaka, K.; Inoue, A.; Yamaki, K.; Yoshizuka, M. (November 2001). "An anatomic study of the extensor tendons of the human hand". The Journal of Hand Surgery. 26 (6): 1009–1015. doi:10.1016/s0363-5023(01)70045-7. ISSN 0363-5023. PMID 11721244.
  5. Carlos, JS.; Goubran, E.; Ayad, S. (2011). "The presence of extensor digiti medii muscle -an anatomical variant". J Chiropr Med (10): 100–104.
  6. Dass, P.; Prabhu, LV.; Pai, MM.; Nayak, V.; Kumer, G.; Janardhanan, JP. (2011). "A comprehensive study of the extensor tendons to the medial four digits of the hand". Chang Gung Med J (34): 612–619.
  7. Mestdagh, H.; Bailleul, JP.; Vilette, B.; Bocquet, F.; Depreux, R. (1985). "Organization of the extensor complex of the digits". Anat Clin (7): 49–53.
  8. Yammine, Kaissar (6 August 2014). "The prevalence of the extensor indicis tendon and its variants: a systematic review and meta-analysis". Surgical and Radiologic Anatomy. 37 (3): 247–254. doi:10.1007/s00276-014-1352-0. ISSN 0930-1038. PMID 25096501.
  9. Ogura, T.; Inoue, H.; Tanabe, G. (1987). "Anatomic and clinical stud- ies of the extensor digitorum brevis manus". J Hand Surg (12): 100–107.
  10. Leslie, DR. (1954). "The tendons of the dorsum of the hand". Aust N Z J Surg (23): 253–256.
  11. Klena, JC.; Riehl, JT.; Beck, JD. (2012). "Anomalous extensor tendons to the long finger: a cadaveric study of incidence". J Hand Surg Am (5): 938–941.

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