The accessory obturator nerve: an anatomical study with literature analysis

Abstract

Objectives: The accessory obturator nerve (AON) is often underrepresented in the literature and unknown to many surgeons.

As this variant nerve has been mistaken for other regional nerves e.g., obturator nerve, nerve injury has occurred.

Therefore, the current study was undertaken to better understand the surgical anatomy of the AON.

Methods: In the supine position, 20 adult fresh frozen cadavers (40 sides) underwent an anterior approach to the retroperitoneal

space. When present, the length and diameter of the AON were measured with microcalipers. The position, course and

origin of each AON were documented.

Results: The AON was identified on 12 sides (30%). The origin was found to be L2–L3 on four sides; L3 on two sides, L3–L4

from three sides, from the obturator nerve on two sides, and from the femoral nerve on three sides. The average length

from the origin to the superior pubic ramus was 14.5 cm. The average diameter was found to be 1.2 mm. All AON were

found to lie medial to the psoas major muscle. Additionally, on all sides, the AON was medial to the femoral nerve and lateral

to the obturator nerve. Two left sides anastomosed with the anterior division of obturator nerve at its exit from the obturator

foramen. Eight sides terminated deep (two) or superficial (six) to the origin of pectineus; two of these had demonstrable

branches to the hip joint.

Conclusion: The AON is a normal anatomical variant and there are many variations in its origin and terminal branches can

be “strong” or “weak.” Knowing the normal anatomy and variations of the AON is important for surgeons including neurosurgeons,

orthopaedic surgeons, and urologists who deal with the pathologies of this area.

Keywords

• anatomy; lumbar plexus; posterior abdominal wall; psoas major; variations

References

1. 1. Swanson LW. Neuroanatomical terminology: a lexicon of classical origins and historical foundations. Oxford: Oxford University Press; 2015. p. 29.
2. 2. Cruveilhier J. The anatomy of the human body. New York (NY): Harper and Brothers; 1844.
3. 3. McMinn RMH. Last’s anatomy: regional and applied. 9th ed., Marrickville (NSW), Australia, Elsevier; 2003. p. 397.
4. 4. Bergman RA, Thompson SA, Afifi AK, Saddeh FA. Compendium of human anatomical variations. Baltimore: Urban and Schwarzenburg; 1988. pp 143–8.
5. 5. Katritsis E, Anagnostopoulou S, Papadopoulos N. Anatomical observations on the accessory obturator nerve (based on 1000 specimens). Anat Anz 1980;148:440–5.
6. 6. Eisler P. Der Plexus lumbosacralis des Menschen. Anat Anz 1891;6: 274–81.
7. 7. Eisler P. Der Plexus lumbosacralis des Menschen. Abh naturforsch Ges Halle 1892;17: 279–364.
8. 8. Bardeen CR, Elting AW. A statistical study of the variations in the formation and position of the lumbosacral plexus in man. Anat Anz 1901;19:124–8, 209–32.

9. 9. Kaiser RA. 1949. Obturator neurectomy for coxalgia. An anatomical study of the obturator and the accessory obturator nerve. J Bone Joint Am 1949;31:815–19.
10. 10. Woodburne RT. The accessory obturator nerve and the innervation of the pectineus muscle. Anat Rec 1960;136:367–9.
11. 11. Webber RH. Some variations in the lumbar plexus of nerves in man. Acta Anat 1961;44:336–45.
12. 12. Akkaya T, Comert A, Kendir S, Acar HI, Gumus H, Tekdemir I, Elhan A. Detailed anatomy of accessory obturator nerve blockade. Minerva Anestesiol 2008;74:119–22.
13. 13. Anloague PA, Huijbregts P. Anatomical variations of the lumbar plexus: a descriptive anatomy study with proposed clinical implications. J Man Manip Ther 2009;17: e107–e114.
14. 14. Quain J, Sharpey W, Thomson A, Cleland JG. Quain’s elements of anatomy. 7 ed. The University of California: James Walton; 1867. p. 663–4.
15. 15. Ellis H. Demonstrations of anatomy. 11th ed. 1887. a, p. 543; b, p. 631.
16. 16. Allen H, Shakespeare EO. A System of human anatomy: bones and joints. 2nd ed. H. C. Lea’s Son & Company; 1883. p. 566.
17. 17. Atanassoff PG, Weiss BM, Brull SJ. Lidocaine plasma levels following two techniques of obturator nerve block. J Clin Anesth 1996;8: 535–9.
18. 18. Akata T, Murakami J, Yoshinaga A. Life-threatening haemorrhage following obturator artery injury during transurethral bladder surgery: a sequel of an unsuccessful obturator nerve block. Acta Anaesthesiol Scand 1999;43:784–88.
19. 19. Rohini M, Yogesh AS, Banerjee C, Goyal M. Variant accessory obturator nerve? A case report and embryological review. Journal of Medical and Health Sciences 2012;1:7–9.
20. 20. Jirsch JD, Chalk CH. Obturator neuropathy complicating elective laparoscopic tubal occlusion. Muscle Nerve 2007;36:104–6.
21. 21. Hollinshead WH. Anatomy for surgeons. Vol. 2: The thorax, abdomen & pelvis. London: Cassell & Co. Ltd.; 1956. p. 636–8.
22. 22. Lennon RL, Horlocker TT. Mayo Clinic Analgesic pathway: peripheral nerve blockade for major orthopedic surgery and procedural training manual. Boca Raton (FL): CRC Press; 2006. p. 6.
23. 23. Bonica J. Management of pain. Philadelphia (PA): Lippincott, Williams & Wilkins; 2010. p. 1079.
24. 24. De Sousa OM. Concideracoes anatomocirurgicas sobre nervo obturator acessorio. Rev Cir S Paulo 1942;7:399–402.
25. 25. Sim IW, Webb T. Anatomy and anaesthesia of the lumbar somatic plexus. Anaesth Intensive Care 2004;32:178–87.
26. 26. Standring S. Gray’s anatomy. 40th ed. London: Churchill Livingstone; 2008. p. 1069–81.
27. 27. Tubbs RS, Sheetz J, Salter G, Oakes WJ. Accessory obturator nerves with bilateral pseudoganglia in man. Ann Anat 2003;185:571–2.
28. 28. Howell AB. The phylogenetic arrangement of the muscular system. Anat Rec 1936;66:295–316.
29. 29. Yasar S, Kaya S, Temiz C, Tehli O, Kural C, Izci Y. Morphological structure and variations of lumbar plexus in human fetuses. Clin Anat 2014;27:383–8.
30. 30. Bolk L. Beziehungen zwischen. Skelett, Muskulatur and Nerven der Extremitäten. Morphol Jahrb 1894;21:241–77.
31. 31. Leche W. Muskulatur. Säugethiere. Mammalia. Dr. H. G. Bronn’s Klassen und Ordnungen des Thierreichs 1900;6:649–919.
32. 32. Grafenberg E. Die Entwickelung der Menschlichen Beckenmuskulatur. Anat Hefte 1904;23:431–93.