Functional and clinical anatomy of the obturator externus muscle: Cadaveric studies and clinical findings for total hip arthroplasty in the posterior approach.

Repairing released posterior soft tissues is important in preventing dislocation after total hip arthroplasty (THA) via the posterior approach. We clarify the functional and the clinical anatomy of obturator externus. We performed cadaveric studies and investigated clinically in primary THA cases. The location, trajectory, and size of the muscular tendon was recorded. The trajectory of the obturator externus ran orthogonal to the femoral axis with the hip in 90° flexion whereas that of the obturator internus muscle ran parallel. Because the trajectory of obturator externus and the obturator internus differ, their functions also differ.