Influence of hip morphology on gluteal muscle biomechanics: a computational modeling study.

Background: Hip morphology variations, particularly in femoral neck shaft angle (NSA) and iliac wing width (IWW), have been associated with gluteal tendinopathy. However, the biomechanical implications of these morphological differences on gluteal muscle function are not well understood. This study investigates how NSA and IWW influence gluteal muscle forces, moment arms, and estimated tendon loads during walking, aiming to provide insights into the potential biomechanical pathways that may contribute to altered lateral hip loading patterns.

Methods: We modified a musculoskeletal model to reflect varying NSAs (108°, 123° and 143°) and IWWs (185, 265 and 345 mm), simulating nine gait cycles to assess the impact on the moment arms and loading of the gluteus medius (GMed) and minimus (Gmin) muscles.

Results: Models revealed that a high NSA with a narrow IWW (NSA143°/IWW185 mm) resulted in the shortest moment arms (GMed, 26 mm; Gmin, 29 mm) and highest peak muscle forces (GMed, 1240 N; GMin, 242 N), suggesting a biomechanical predisposition to gluteal tendinopathy. Conversely, a low NSA with a wide IWW (NSA108°/IWW345 mm) produced the longest moment arms (GMed, 47 mm; GMin, 45 mm) and lowest peak muscle forces (GMed, 742 N; GMin, 145 N). A 4° decrease in NSA reduced tensile load by 37 N (4.0%, p < 0.001) for GMed and 4 N (2.7%, p = 0.025) for GMin, with a minor increase in GMin compressive load by 2 N (1.8%, p = 0.048). A 10 mm decrease in IWW increased tensile and compressive loads by 12 N (1.3%, p < 0.001) and 20 N (20%, p < 0.001) for GMed, and by 3 N (2%, p < 0.007) and 3 N (2.7%, p < 0.007) for GMin.

Conclusions: Our biomechanical modeling suggests patients with narrow iliac width may be predisposed to gluteal tendinopathy through increased tendon loading. The protective mechanical effect of decreased neck shaft angle suggests its clinical association with tendinopathy likely involves other factors, such as IT band compression which was not accounted for in this study. For clinical assessment, iliac width measurement may help identify at-risk patients and guide preventive interventions, while neck shaft angle should be evaluated within a broader anatomical context.