Intermuscular Fat, But Not Subcutaneous Fat, Correlated With Major Complications After Primary Total Hip Arthroplasty

To investigate the relationship between upper-thigh intermuscular fat, subcutaneous fat measured by CT and major complications after primary total hip arthroplasty (THA).Between 2015 and 2021, consecutive patients who had primary THA and preoperative hip CT were retrospectively included. Upper-thigh muscle cross-sectional intermuscular fat, subcutaneous fat, and muscle area were measured on hip CT images. The major complications included dislocation, aseptic loosening, infection, and periprosthetic fracture. The effect of upper-thigh intermuscular fat, subcutaneous fat and muscle area on the outcome was analyzed using multivariable cox proportional hazards analysis. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated.A total of 3028 patients were included and 71 (2.34%) of them had major complications. During a median of 25 months of follow-up, patients showed increased incidence of total major complications with increased intermuscular fat area (log-rank p = 0.012). The multivariable cox regression revealed that per SD increment in intermuscular fat area was associated with higher risk of total major complications (HR = 2.04, 95% CI = 1.71-2.43, p < 0.001), dislocation (HR = 1.96, 95% CI = 1.44-2.66, p < 0.001), aseptic loosening (HR = 2.02, 95% CI = 1.30-3.16, p = 0.002), infection (HR = 1.94, 95% CI = 1.24-3.05, p = 0.004), and periprosthetic fracture (HR = 2.26, 95% CI = 1.67-3.07, p < 0.001).Upper-thigh intermuscular fat, but not subcutaneous fat measured on CT associated with the risk of major complications after primary THA.