OBJECTIVES: This study aimed to determine the relationship between preoperative fatty infiltration of the lower extremity muscles and walking speed at 2 weeks after total hip arthroplasty (THA). METHODS: This was a single-institution retrospective cohort study. Participants in this study were patients undergoing primary THA. Fatty infiltration in each muscle (bilateral psoas major, gluteus maximus, gluteus medius, gluteus minimus, quadriceps, and triceps surae) was assessed using non-contrast X-ray computed tomography images obtained during a detailed preoperative examination. The outcome of this study was the normal comfortable walking speed at 2 weeks after THA. Decreased walking speed was defined as less than 0.8 m/s (non-decreased group, coded 0
decreased group, coded 1). Multivariate logistic regression analysis was used to analyze the relationship between fatty infiltration of each skeletal muscle and walking speed. RESULTS: A total of 168 participants were included in the analysis. On the operative side, the analysis identified fatty infiltration of the gluteus medius (odds ratio, 0.95
95% confidence interval, 0.91-0.99) as a determinant of decreased walking speed after THA. On the nonoperative side, the analysis identified fatty infiltration of the quadriceps (odds ratio, 0.91
95% confidence interval, 0.83-0.99) as a determinant of decreased walking speed after THA. CONCLUSIONS: In patients undergoing THA, increased fatty infiltration of the gluteus medius on the operative side and the quadriceps on the nonoperative side were associated with decreased walking speed at 2 weeks postoperatively.