Pattern of Inner- vation of the Upper Gluteus Maximus Muscle: Implication in Prosthetic Hip Dislocation.

K A, A P, G G. "Pattern of Inner- vation of the Upper Gluteus Maximus Muscle: Implication in Prosthetic Hip Dislocation." Annals of African Surgery. 2011;8(2):28-30.


Gluteus Maximus Muscle: Implication in Prosthetic Hip Dislocation
Awori K.O. MBChB, MMed (Surgery), Dip. (SICOT), FCS (Orth) ECSA, Anne N. Pulei A.A. Bsc, MBChB, Gikenye G. MBChB, MMed,FCS(ECSA) Affiliation: Department of Human Anatomy, University of Nairobi, P.O. Box 30197 00100 Nairobi, Kenya. Correspondingauthor: KirsteenO.Awori,Tel.254-722812499,Email:
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
Gluteus maximus (GM) is a powerful hip extensor inner- vated by the inferior gluteal nerve (IFN) and an impor- tant muscle in rising up from squatting position, climb- ing (1) and running (2). Its functions during running are to control flexion of the trunk on the stance-side (3) and to decelerate the swing leg. Low levels of GM activity may contribute to hip extension during stance, and to re- strain hip flexion during swing. During loading response of the gait cycle, in the frontal plane, activity in the up- per portions of the gluteus maximus, hip abductors and tensor fascia lata control drop of the contralateral pelvis, which is relative hip adduction (4).
Risk factors in prosthetic hip dislocation include patient- related ones such as neuromuscular disease (5) and sur- gical ones. Of the surgically-related factors, the approach has generated a lot of controversy. In the Moore posteri- or approach to the hip the incision starts 10 centimetres from the posterior superior iliac spine, is directed later- ally and distally to the back of the greater trochanter and extends for 10 or more centimetres, parallel to the shaft of the femur. The deep fascia is exposed and the iliotibial band is incised from the trochanter to the distal end of
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.

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