Variability and clinical anatomy of the superior gluteal nerve-A systematic review and meta-analysis.

The superior gluteal nerve (SGN) is a mixed nerve of the sacral plexus that arises from the posterior divisions of the L4, L5, and S1 nerve roots. Its motor branch plays a crucial role in innervation of hip muscles, which allows for physiological gait or walk-pattern. As for its sensory branch, it provides innervation for the hip joint capsule, especially its superior part. The understanding of this nerve is crucial as it may be injured during many operations involving mostly pelvic surgery, both arthroscopic and open procedures. The risk of injury is especially high during total hip arthroplasty (THA). These lesions often result in the presentation of major walk-pattern abnormalities. The most classical and commonly known would be the Trendelenburg sign, which presents with pelvic instability characterized by having the patient standing on one leg whereby the pelvis on the contralateral side will be dropping, resulting in a positive sign. The aim of this meta-analysis was to obtain all relevant data on SGN and its variations, in order to emphasize its anatomical, physiological, as well as clinical implications. A large-scale search was conducted in all major databases (PubMed, Embase, Science Direct, Google Scholar, and Web of Science) in order to determine and pool all available and relevant SGN data. No restrictions were applied to date or language. The data collection was categorized by prevalence, branching, patterns, course, origin, and distance from anatomical landmarks. A total of 41 studies (n = 869 hemipelves) were included in our analysis. The most common branching pattern of SGN was a spray pattern, 70.4% (95% CI: 54.4-96.8; p < 0.001) of the general population. We found that the closest branch to the greater trochanter of the femur and concurrently the most at risk during surgery was a muscular branch to gluteus minimus muscle. As the trend of pelvic surgeries, especially THA continues to rise, SGN lesions are now more than ever at risk. Yet to the authors' knowledge, this does not seem to be reflected in the current literature thereby making this the first meta-analysis concerning this important anatomical structure. The authors believe it is paramount for surgeons, especially in the orthopedic specialty, to thoroughly understand the SGN with its anatomical variability and clinical tie-ins.