Explanation:
In the posterior approach to total hip arthroplasty, the short external rotators (piriformis, obturator internus, superior and inferior gemelli) along with the posterior capsule provide critical posterior stability to the hip joint. These structures act as dynamic and static stabilizers preventing posterior translation of the femoral head, particularly when the hip is in flexion, adduction, and internal rotation. Failure to repair the posterior capsule and short external rotators during closure has historically been associated with significantly higher rates of postoperative dislocation. Modern posterior approaches emphasize meticulous repair of these structures to restore stability and reduce the incidence of instability after surgery. Reference: Pellicci PM et al., 'Posterior approach to total hip replacement using enhanced posterior soft tissue repair', Clinical Orthopaedics and Related Research (1998).