Inadvertent short external rotator tendon release during anterior-approach total hip arthroplasty: a prospective magnetic resonance imaging study

BACKGROUND: The direct anterior approach for total hip arthroplasty (DAA THA) is believed to be a tissue-sparing approach that aims to spare the short external rotator (SER) tendons and posterior capsule, but the rate of SER release is unknown. We sought to prospectively determine the early appreciable percentage of SER tendon release among patients undergoing DAA THA for osteoarthritis using magnetic resonance imaging (MRI). METHODS: We recruited participants undergoing DAA THA for osteoarthritis for this single-centre, prospective study. All participants underwent a 1.5 T MRI preoperatively and 3 months postoperatively. The surgeon recorded the status of SER tendons intraoperatively. Two fellowship-trained musculoskeletal radiologists independently reviewed MRIs for integrity of SER tendons at each time point. CONCLUSION: Given the complexity of attachment of conjoint and piriformis tendons to the lateral capsule and appropriate stem positioning, release of these tendons viewed on MRI is inevitable. This may be owing to their inadvertent release during capsular exposure, as these tendons merge with the capsule, or during lateralization and posterization rasping of the femoral broach, especially for the obturator internus.