Pattern of Innervation of the Upper Gluteus Maximus Muscle: Implication in Prosthetic Hip Dislocation

Abstract

Background: Dislocation is one of the most common complications after total hip arthroplasty. The posterolateral approach avoids disruption of the abductor mechanism but may denervate gluteus maximus as a basis for associated higher dislocation rates. Objective: To determine the pattern of innervation of gluteus maximus ​ Study design: Descriptive cross-sectional study Materials and methods: Twenty four cadavers for routine dissection in the Department of Human Anatomy, University of Nairobi were used. Having exposed the gluteus maximus, the muscle was transected close to its distal attachment and reflected superiorly to expose the entry of the neurovascular structures into it from the greater sciatic foramen. The pattern of distribution of the inferior gluteal nerve to the muscle was noted and the left and right in the same cadaver compared Results: In all the 48 cadaver sides, the inferior gluteal nerve exited the pelvis via the infra-piriformic compartment of the greater sciatic foramen. In majority (43, 89.6%) of gluteal regions this nerve funned out in multiple equal branches to the GM. Only one branch crossed the upper border of piriformis muscle. In 5 cases, this single branch that crossed the upper border of piriformis was a major trunk almost equal in size to the parent nerve. One such case was bilateral. Conclusion: A major branch of the inferior gluteal nerve to the upper part of GM, when present, could be injured in the posterior approaches to the hip to significantly weaken the upper part of this muscle increasing the risk of prosthetic hip dislocation.