Preoperative abductor muscle strength on the healthy side affects the Timed Up and Go test after total hip arthroplasty in women.

Background: The risk of falls causing periprosthetic fracture has become an issue with the increase in the number of patients undergoing long-term follow-up after total hip arthroplasty (THA) and the aging of patients. The Timed Up and Go test (TUG) is utilized to evaluate fall risk. This study investigated muscle volume around the hip joint based on computed tomography (CT), CT value, and muscle strength to investigate contributing factors to poor TUG 1 year post-THA.

Methods: This study retrospectively investigated 124 patients with unilateral hip osteoarthritis who underwent THA and classified them based on TUG results at 1 year postoperatively into TUG of < 10 s (fast group [103 patients]) and ≥ 10 s (slow group [21 patients]). Body mass index, the volume and CT density of the psoas major and gluteus medius muscles on CT images, pre- and postoperative hip flexion muscle strength, and hip abductor muscle strength were compared in each group.

Results: Age was significantly older and preoperative abductor (fast Group: 1.0 ± 0.3 and slow Group: 0.7 ± 0.3, P = 0.003) and flexion muscle strengths (0.9 ± 0.3 and 0.7 ± 0.3, respectively, P = 0.02) on the healthy side were significantly lower in the slow group. The gluteus medius muscle demonstrated significantly lower CT density in the slow group on both sides. Nominal logistic regression analysis revealed that age and preoperative healthy abductor muscle strength, which are poor factors for TUG 1 year post-THA, were significantly associated with TUG of ≥ 10 s at 1 year post-THA.

Conclusions: The poor factors for TUG 1 year after THA were age and preoperative abductor muscle strength on the healthy side.