Computed Tomography Analysis for Postoperative Muscle Changes in Patients With Ankylosed Hips Who Underwent Total Hip Arthroplasty: Three Case Reports

In patients with ankylosed hips, activities of daily living (ADL) are often restricted because of the limited range of hip motion and adjacent joint disorders that cause severe low back and knee pain. Total hip arthroplasty (THA) can improve hip mobility and reduce adjacent joint pain; however, muscle atrophy around the hip joint potentially interferes with ADL improvement. Herein, we describe the seven-year clinical outcomes of computed tomography (CT)-based navigation THA in three patients with ankylosed hips. Additionally, we report the longitudinal changes in muscle atrophy; the muscle volume around the hip joint was measured using CT analysis. The three patients include one woman and two men, aged 75, 65, and 73, respectively, who underwent THA using a CT-based navigation system. None of the patients experienced THA post-operative complications, and all were able to walk with a cane and sit freely in a chair. The hip function of the Harris Hip Score improved from a mean of 71.0 points to 86.6 points at seven years postoperatively. The volume of the gluteus maximus muscle increased in all patients (mean +10.1%); however, the gluteus medius and minimus decreased in all patients (mean, -42.2% and -51.0%). THA with CT-based navigation for ankylosed hips improves ADL, hip joint function, and muscle volume of the gluteus maximus in mid-term clinical results; however, muscle volume recovery in the gluteus medius and minimus can be insufficient.