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Published on: September 7, 2022
Inadvertent short external rotator tendon release during anterior-approach total hip arthroplasty: a prospective
Rajrishi Sharma1, Manjot S Birk2, Ahmed El-Bakoury2
1From the University of Calgary, Calgary, Alta. (Sharma, Birk, Johnston); the McCaig Institute for Bone and Joint Health, Calgary, Alta. (Sharma); the Alberta Hip and Knee Clinic, Calgary, Alta. (Sharma, Johnston); the Mediclinic Parkview Hospital, United Arab Emirates (El-Bakoury); Alexandria University, Egypt (El-Bakoury); the Department of Orthopaedics, St. Paul's Hospital, University of British Columbia, Vancouver, BC (Veljkovic); Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, Alta. (Walker); the Cumming School of Medicine, University of Calgary, Calgary, Alta. (Salat). rajrishi.sharma@ucalgary.ca.
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.
Results:
We recruited 25 participants with Kellgren-Lawrence grade 3 or 4 osteoarthritis. The average age was 65 (range 51 to 80) years, and the average body mass index was 28.2 (range 21.2 to 40.8). Of the 25 participants, 13 (52%) were male; 14 (56%) participants were undergoing THA for their left hip. On preoperative MRI, all SER tendons were intact. Intraoperatively, the surgeon reported 2 (8%) purposeful releases of the obturator internus for assistance on exposure and no purposeful piriformis or obturator externus releases. On postoperative MRI, consensus reading concluded complete release of the obturator internus in all participants (100%), piriformis release in 72% of participants, and obturator externus release in 4% of participants. We observed significant differences between SER tendon integrity on postoperative MRI and the surgeon's reported releases for obturator internus and piriformis (p < 0.001).
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.
