Magnetic Resonance Imaging Assessment of Hip Abductor after Total Hip Arthroplasty Using a Direct Lateral Approach

Background: Surgical techniques and rehabilitations after total hip arthroplasty (THA) play a significant role in the improvement of pain and limping. This study aimed to assess hip abductor muscle’s diameter and its strength after 6 months postoperative THA performed by Hardinge approach. Methods: After obtaining the patients’ demographic characteristics, the preoperative values of patients’ hip abductor muscle diameter were measured using magnetic resonance imaging, and were compared with postoperative values 6 months later. Moreover, the hip abductor muscle’s strength was assessed using the Trendelenburg test. Results: A total of 88 patients participated in this study with a mean age of 47.3±1.574 years. It should be noted that 55.7% of the participants were male. Muscle diameter decreased from a mean value of 27.07±7.485 preoperative to mean value of 25.64±7.353 mm postoperative (P<0.001). Moreover, the degrees of Trendelenburg test (i.e., mild or severe) decreased after surgery (P<0.001). There was no significant difference between the frequencies of different grades of limping according to the studied variables. Conclusion: A decrease was observed in gluteus medius muscle diameter, and the Trendelenburg test results were improved in this study. Moreover, the difference between pre- and postoperative gluteus medius muscle diameters were measured using MRI. It can be concluded that MRI is not an appropriate diagnostic tool for the assessment of abductor strength after THA in the 6-month postoperative visit. Accordingly, it is suggested to evaluate muscle strength before and after each surgery to schedule the following treatment protocol required for each patient.