Alireza Manafi Rasi - Department of Orthopedic Surgery, Imam Hossein Hospital, Shahid Beheshti University of Medical Science, Tehran, Iran
Reza Zandi - Department of Orthopedic Surgery, Taleghani Hospital, Shahid Beheshti University of Medical Science, Tehran, Iran
Mohamad Qoreishi - Department of Orthopedic Surgery, Akhtar Hospital, Shahid Beheshti University of Medical Science, Tehran, Iran
Ali Habibollahzadeh - Department of Orthopedic Surgery, Imam Hossein Hospital, Shahid Beheshti University of Medical Science, Tehran, Iran

Background: Surgical techniques and rehabilitations after total hip arthroplasty (THA) play a significant role in theimprovement of pain and limping. This study aimed to assess hip abductor muscle’s diameter and its strength after 6months postoperative THA performed by Hardinge approach.Methods: After obtaining the patients’ demographic characteristics, the preoperative values of patients’ hip abductormuscle diameter were measured using magnetic resonance imaging, and were compared with postoperative values 6months 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 that55.7% of the participants were male. Muscle diameter decreased from a mean value of 27.07±7.485 preoperative tomean value of 25.64±7.353 mm postoperative (P<0.001). Moreover, the degrees of Trendelenburg test (i.e., mild orsevere) decreased after surgery (P<0.001). There was no significant difference between the frequencies of differentgrades of limping according to the studied variables.Conclusion: A decrease was observed in gluteus medius muscle diameter, and the Trendelenburg test results wereimproved in this study. Moreover, the difference between pre- and postoperative gluteus medius muscle diameters weremeasured using MRI. It can be concluded that MRI is not an appropriate diagnostic tool for the assessment of abductorstrength after THA in the 6-month postoperative visit. Accordingly, it is suggested to evaluate muscle strength beforeand after each surgery to schedule the following treatment protocol required for each patient.Level of evidence: IV

Hardinge, Hip Abductor Diameter, magnetic resonance imaging, Trendelenburg test