Local adiposity at the surgical site outperforms BMI as a predictor of postoperative wound problems in THA

Postoperative wound complications remain a significant cause of morbidity after total hip arthroplasty (THA). Body mass index (BMI) is commonly used for risk assessment, but it does not reflect regional fat distribution. This study aimed to determine whether surgical site fat thickness (SSFT), measured on preoperative radiographs, is a more accurate predictor of wound complications than BMI in patients undergoing posterior approach THA. A prospective cohort study was conducted on 157 patients who underwent primary posterior approach THA at a single tertiary centre. SSFT was measured as the perpendicular distance from the greater trochanter to the skin surface on standardized anteroposterior radiographs. Preoperative BMI was recorded for all patients. Wound complications within 90 days—including superficial infection, wound dehiscence, prolonged drainage, and unplanned return to the operating room—were documented. Logistic regression was used to evaluate predictors, and receiver operating characteristic (ROC) analysis compared the discriminatory performance of SSFT and BMI. Eighteen patients (11.5%) developed wound complications. Increased SSFT demonstrated a strong independent association with wound problems, with each additional millimetre increasing the odds of complications by 15%. BMI did not independently predict wound complications after adjustment for confounders. ROC analysis revealed superior predictive accuracy for SSFT (area under the curve 0.82) compared with BMI (0.65). An SSFT threshold of 25 mm yielded optimal sensitivity and specificity for identifying high-risk patients. SSFT is a more precise predictor of postoperative wound complications than BMI in patients undergoing THA. Incorporating SSFT into preoperative evaluation may enhance risk stratification and guide targeted perioperative wound-management strategies.