A cadaveric study of surgical anatomy of the obturator nerve in the adult Kenyan population

Abstract

Background: Anatomical ethnic variations of the obturator nerve have been described in other populations. Chronic groin pain especially in athletes due to obturator nerve neuropathy has been reported in local population. Iatrogenic injury to the nerve has also been documented especially in acetabular reconstruction. Good anatomical understanding and relevance in surgical approaches and intervention in situations such as pelvic fractures, acetabular labral cysts, obturator nerve ganglions among others are important. Objective: To determine the variations in the course of obturator nerve main trunk, level of division into anterior and posterior branches and distribution of branches in the adult Kenyan population. Methods: Anatomical descriptive cross-sectional study done at Human Anatomy Laboratory, Moi University, involved census of sixty adult black Kenyan specimens which were dissected from obturator nerve main trunk, divisions, and distribution of anterior and posterior branches. Location of the nerve in obturator foramen was measured in relation to most medial, inferior and superolateral points. Photography done and data recorded in a structured data collection sheet. Analysis for variables was done using STATA version 13 SE and presented in prose and diagrams. Comparison of the measurements between the sexes and left and right side were done using two sample t-tests. Results: Main trunk emerged from the medial border of the psoas major muscle, descended on the lateral wall of the lesser pelvis towards the obturator foramen. Intatrapelvic branch to the obturator externus occurred in 3.33% of specimens.The nerve exited obturaor canal at mean distance of 14.95mm from the most medial point of obturator foramen. Majority divided into anterior and posterior branches in the obturator canal at 88.3% and in the thigh at 11.7%. Anterior division branches innervated all of adductor longus, gracilis, 98.3% of adductor brevis and 6.7% of pectineus in all specimens recorded. Supply to adductor longus and gracilis were from the same division in 70% with the rest arising independently from the anterior division branches. The posterior division branches supplied adductor magnus in all specimens, 1.7% of adductor brevis specimens and all of obturator externus. Articular branch in the specimens came from anterior division branches in 60%, 30% from common trunk and 10% from posterior division branches. No statistical difference between the sexes and the sides were noted as shown by the p-values. Conclusion: Intrapelvic branch to obturator externus is present in local population. The division into anterior and posterior in majority occurred within the obturator canal. Anterior division branches supplied adductor longus, gracilis, most of adductor brevis and occasionally pectineus. Posterior division branches supplied adductor magnus, obturator externus and rarely adductor brevis. Recommendations: Surgeons should be aware of variations in obturator nerve main trunk, divisions, and branches during surgery. The most medial and most inferior points of the obturator foramen allow for safe transforaminal procedures.