Obturator Externus

Original Editor - Manisha Shrestha

Top Contributors - Manisha Shrestha, Vidya Acharya and Kim Jackson

Description

Obturator externus (OE) muscle is the conical shaped short external rotator located in the outer side of obturator membrane in lateral wall of pelvis.

Anatomy

[1]

Origin

The Obturator externus (OE) muscle originates from the rami of pubis and ischium, the external bony margin of the obturator foramen in a clockwise direction from 12 o'clock around to the 10 o'clock position (right hip viewed from the front), and a few fibres arose from the obturator membrane.[2][3]

Insertion

It formed a musculotendinous junction at the level of the femoral neck. The fibres passed laterally along the inferior margin of the acetabulum, acting like a sling at the inferior part of the neck and inserted as a cylindrical tendon into the trochanteric fossa with some fibres extending towards the piriformis fossa.[2]

Nerve

The posterior branch of the obturator nerve, L2-L4[4].

Artery

The anterior branch of obturator artery and medial circumflex femoral artery.

Function

[5]
  • Obturator externus externally rotates hip during neutral and flexion but not in hip extension.[2]
  • It may assist in the adduction of the hip joint during flexion [4].
  • It helps to stabilise the head of the femur in the socket during flexion and internal rotation as it's posterior fibers reinforce the posterior capsule of hip joint. [2]

Clinical relevance

  1. Solomon et al explored the role of the short external rotators in hip stability following a total hip replacement (THR) through a posterior approach. They noted that preservation of the piriformis and the external obturator reduces the risk of dislocation after THR indicating other approaches for THR.[3] OE with its fibres which reinforce the posterior capsule acts as a hip joint stabiliser.[2]
  2. Obturator externus(OE) bursa- OE bursa with bursal fluid was present between the transverse acetabular ligament and the OE muscle. Studies suggest that OE bursa is prevalent in hips with intra articular pathology than normal hips.[2]
  3. Repetitive eccentric contraction of Obturator externus causing musculotendinous tear in professional basketball players. Targeted rehabilitation will ensure a rapid return to competition without complication[6]
  4. Impingement syndrome after total hip replacement-a close relationship between the musculo-tendinous part of the OE muscle and the inferior margin of the acetabulum can lead to the impringement syndrome if transverse acetabular ligament is released or an acetabular cup position protruding beyond the caudal rim after arthroplasy. Releasing the OE insertion attachment to the posterior capsule decreased the risk of impingement. [2][7]

Assessment

Treatment

Resources

  1. Kenhub - Learn Human Anatomy. Functions of the obturator externus muscle - 3D Human Anatomy | Kenhub. Available from: https://www.youtube.com/watch?v=3LHk8KUAcw8 [last accessed 30/3/2020]
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Gudena R, Alzahrani A, Railton P, Powell J, Ganz R. The anatomy and function of the obturator externus. Hip International. 2015 Sep;25(5):424-7.
  3. 3.0 3.1 Solomon LB, Lee YC, Callary SA, Beck M, Howie DW. Anatomy of piriformis, obturator internus and obturator externus: implications for the posterior surgical approach to the hip. The Journal of bone and joint surgery. British volume. 2010 Sep;92(9):1317-24.
  4. 4.0 4.1 Kendal, McCreary, Provance; Muscle Testing and Function with Posture and Pain; 4th Edition; Lateral Rotators of Hip Joint, Page 218.
  5. Hip Rotator Series Part 1: Obturator Externus. Available from:https://www.youtube.com/watch?v=CglBvRB2JQ4 [last accessed 30/3/2020]
  6. Coudert R, Coudreuse JM, Le Corroller T, Bensoussan L, Champsaur P, Delarque A, Viton JM. Obturator externus musculotendinous injury in a professional basketball player. Annals of Physical and Rehabilitation Medicine. 2015 Sep 1;58:e67.
  7. Müller M, Dewey M, Springer I, Perka C, Tohtz S. Relationship between cup position and obturator externus muscle in total hip arthroplasty. Journal of orthopaedic surgery and research. 2010 Dec 1;5(1):44.