Anatomic Mapping of the Inferior Branch of the Superior Gluteal Nerve: Implications for Revision Total Hip Arthroplasty

BACKGROUND: The superior gluteal nerve (SGN) is at risk for iatrogenic injury during primary total hip arthroplasty (THA), with reported rates as high as 8%. The SGN integrity is critical for abductor function, especially in the revision setting where instability rates are inherently higher. The Adelaide approach is an extended posterior approach facilitating improved exposure and identification of the SGN bundle during complex revision THA. Few studies have detailed the anatomy of the inferior branch of the SGN, which is in close proximity, particularly in revisions for acetabular bone loss. We performed an Adelaide approach to identify the inferior branch of the SGN and established its location variability in reference to specific anatomical landmarks. METHODS: There were 28 Adelaide approaches (14 cadavers) performed across three academic institutions (United States, Australia, and India). The inferior branch of the SGN was identified after reflecting the gluteus medius muscle, and distances to the acetabular rim, the tip of the greater trochanter, and the inferior border of the gluteus minimus muscle were recorded. RESULTS: The mean distance for the entire study group was 3.3 cm to the acetabular rim (range, 1.5 to 4.6), 4.9 cm to the greater trochanter(range, 3 to 7.6), and 2.9 cm to the gluteus minimus muscle border (range, 1.0 to 4.3). CONCLUSIONS: The inferior SGN branch is consistently near all anatomic landmarks. Understanding the relationship of the SGN to surrounding anatomical structures is important for optimizing SGN function during revision THA, particularly with severe acetabular bone loss in which constructs may extend onto the lateral ilium. Future electromyographic studies may help determine if the Adelaide approach allows for better visualization and protection of the SGN bundle during revision procedures while avoiding injury and preserving abductor function.