Perioperative Inflammatory Biomarkers and Surgical Site Infection After Pelvic and Acetabular Fracture Surgery: A Retrospective Cohort Study

Background: Surgical site infection (SSI) remains a serious complication following operative treatment of pelvic and acetabular fractures. Although routinely available inflammatory biomarkers have been investigated for perioperative risk assessment in various orthopedic populations, their association with SSI after pelvic and acetabular fracture surgery remains unclear. This study aimed to evaluate the association between perioperative inflammatory biomarkers and postoperative SSI in patients undergoing surgical fixation of pelvic and acetabular fractures. Methods: Adult patients who underwent definitive surgical fixation for pelvic ring and/or acetabular fractures between January 2018 and January 2025 were retrospectively reviewed. Hematological parameters and inflammatory biomarkers, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI), were assessed at admission, preoperatively, and on postoperative day 0. Factors associated with SSI were evaluated using univariable Cox regression and Firth penalized logistic regression, with adjustment for treatment strategy, time to definitive surgery, age, sex, and Injury Severity Score. Exploratory receiver operating characteristic analyses were performed to assess the discriminatory ability of preoperative laboratory parameters and inflammatory biomarkers. Results: Among 104 patients, 12 (11.5%) developed SSI. Univariable Cox regression identified staged treatment (p = 0.015), longer time from injury to definitive surgery (p = 0.023), lower admission platelet count (HR 0.61 per 50 × 109/L increase, 95% CI 0.38–0.97; p = 0.038), and higher admission SIRI (HR 1.03, 95% CI 1.00–1.05; p = 0.048) as factors associated with SSI. In the multivariable Firth-penalized logistic regression analysis, neither staged treatment nor time to definitive surgery remained statistically significant, and none of the included covariates demonstrated a statistically significant independent association with SSI. Exploratory ROC analyses showed limited discriminatory performance of the evaluated preoperative laboratory parameters and inflammatory biomarkers. Conclusions: Routinely available perioperative inflammatory biomarkers demonstrated limited utility for identifying patients at risk of SSI following pelvic and acetabular fracture surgery. The associations of admission SIRI, admission platelet count, staged treatment, and delayed definitive fixation observed in univariable analyses should be considered exploratory. These findings highlight the multifactorial nature of postoperative SSI and warrant validation in larger prospective cohorts.