Smoking increases the risk of early postoperative infection after elective total hip arthroplasty: Evidence from a Nationwide Japanese database

PURPOSE: Smoking is a potentially modifiable risk factor for adverse outcomes after total hip arthroplasty (THA), but evidence on early postoperative complications in Asian populations remains limited. This study examined the association between smoking and early postoperative complications after elective THA using a nationwide inpatient database in Japan. METHODS: This retrospective cohort study analysed data from the Japanese Diagnosis Procedure Combination (DPC) database between December 2011 and March 2023. Patients undergoing elective primary THA for osteoarthritis, osteonecrosis of the femoral head, or rheumatoid arthritis were included. Smoking status was identified using administrative codes. One-to-one propensity score matching was used to balance baseline characteristics between smokers and non-smokers. Primary outcomes were early postoperative surgical complications, medical complications, and in-hospital mortality. Dose-dependent effects were assessed using the Brinkman Index, with heavy smoking defined as ≥ 600. RESULTS: After propensity score matching, 52,551 patients were included in each group. Smoking was associated with a higher risk of postoperative infection (odds ratio [OR] 1.31; 95% confidence interval [CI] 1.15-1.49; p < 0.001) and a lower likelihood of blood transfusion (OR 0.83; 95% CI 0.80-0.85; p < 0.001). No significant associations were observed with dislocation, periprosthetic fracture, wound dehiscence, reoperation, major medical complications, or in-hospital mortality. Heavy smoking (Brinkman Index ≥ 600) was not associated with postoperative complications. CONCLUSIONS: Smoking was associated with an increased risk of early postoperative infection following elective THA, but not with other major complications or in-hospital mortality. Smoking cessation should be considered an important component of perioperative optimisation.