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

Abstract

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