Lumbar plexus and its variations

Introduction: Looking to the applied significance of lumbar plexus in the form of its involvement in various injuries, direct or iatrogenic and entrapment, it is imperative to have a thorough knowledge about its formation, branching pattern, and variations. Tubbs et al referred to the lumbar plexus as a 'no man's land' because of relative inaccessibility of this region and there is infrequency in operating on retroperitoneal structures by neurosurgeons. However, a recent increase in retroperitoneal laparoscopic surgeries inspired us to revisit the anatomy of lumbar plexus. Material and methods: The study was conducted on 30 formalin embalmed cadavers available in the Department of Anatomy, RMC, PIMS, Loni, Maharashtra. Thorough dissection was performed to observe the formation of branches of lumbar plexus and measurements were taken from the adjacent bony landmarks. Result: Bilateral prefixation of the lumbar plexus was found in one cadaver bilaterally. Ilioinguinal and iliohypogastric nerves were arising by a common stem in 11.66% of cases; in the remaining ones, they were having separate origins. In majority, 81.6% of the genitofemoral nerve pierced the medial third of the anterior surface of the psoas major muscle. Accessory obturator nerve was observed in 3 cases (5%) of 60 plexuses. The site of formation of femoral nerve was 5 cm inferior to the iliac crest in 71.6% of instances. The formation of obturator nerve was found to vary from the level of supracristal plane to 3.5 cm inferior to the plane; in 58.3%, it was 3 cm below the plane. Conclusion: The measurements given in this study will help the surgeon to avoid iatrogenic nerve injury as well as to assess them during lumbar plexus block.