Surgical anatomy of femoral nerve(s) in formalin prefixed cadavers in an adult Kenyan population

Abstract

Background: Variations involving femoral nerve have been described in literature. This nerve is the largest branch of the lumbar plexus arising from the posterior division of the ventral rami, 2nd- 4th nerve roots. It has motor innervation to hip flexor, knee extensors, while sensory to medial and anterior aspects of the thigh. Risks of insults to nerve can be non-iatrogenic (trauma), and iatrogenic (approaches and procedures to the acetabulum, pelvis and proximal femur, when mostly not cautious, and unaware of variant anatomy). The study aimed at providing precise description of variant anatomy of nerve, hence will help surgeons avoid iatrogenic insults. Objective: To describe the anatomical course and length of the femoral nerve and its main branches in relation to the inguinal ligament. Methods: Study site was Human Anatomy Laboratory, Moi University School of Medicine, using anatomic descriptive cross-sectional study design. It involved a selected population of fifty six (56), both male and female formalin prefixed adult cadaveric specimens. Included were adult pelvic and lower limb cadavers without gross evidence of fracture, pathology or prior surgery, while excluded were deformed or mutilated cadavers. Dissection was done to expose femoral nerve and its branches according to Cunningham’s Manual of Practical Anatomy 15th Edition. The length of the femoral nerve in relation to the inguinal ligament and its bony attachments, and the patterns of distribution of main branches in the regions were defined. Measurements were taken using Vernier callipers (accuracy to 0.01mm) and documented in the structured data collection forms. Coloured photographs of the nerves and branches were taken and also documented. Measurements were analysed using IBM SPSS Statistics Version 20.0.0. Results presented in form of tables, text, graphs and photographs. Results: Males- 35 (Left=17, Right=18); Females- 21(Left=7, Right=14). Femoral nerve location- lateral to mid-inguinal point: 53.02 mm (SD 14.59) from the ipsilateral anterior superior iliac spine (ASIS) and 72.87mm (SD 19.75) from the pubic symphysis. Nerve trunk in relation to inguinal ligament measured: 47.85mm (SD 13.719) from the psoas muscle proximally and branched 29.32 mm (SD 14.239) distally. Innervations and branches: quadriceps in all specimens (Posterior); Sartorius muscles (Anterior), with noted variability in individual muscles. Branching pattern variations: 6 limbs (10.71%) at ligament level, 2(3.57%) limbs had a more proximal, while one nerve was split by a slip from the psoas muscle and then united 25.88mm proximal to ligament. The variations in sex and measurements were not statistically significant (p> 0.05). Conclusion: The anatomical course, length and branches of the femoral nerve in relation to inguinal ligament in adult Kenyan population concur to great extent with described anatomic studies with some noted variability. Recommendations: Surgeons should be aware of the anatomic variations of femoral nerve and be cautious when operating in the zones traversed by the nerve.