The Role of Combined Inflammatory Biomarkers in the Diagnosis of High- and Low-Virulence FRI Among High-Risk Lower Extremity Fractures

OBJECTIVE: The aim of this study is to evaluate the diagnostic accuracy of infection-related biomarkers in high-risk lower limb injury patients with fracture-related infection (FRI) caused by high-/low-virulence microorganisms. METHODS: This study was a retrospective analysis of patients with high-risk lower extremity fractures (including tibial plateau, calcaneus, and Pilon fractures) who underwent open reduction internal fixation (ORIF) surgery from January 2017 to February 2022. Peripheral blood samples were collected within 24 hours of admission, and the following information was evaluated: gender, age, BMI, smoking, comorbidities, injury information, surgical details, values for serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), as well as neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR). RESULTS: A total of 576 patients receiving lower extremity fracture surgery were included in this study. Fifty-one patients (8.85%) were identified as FRI, and 28 (54.9%) of these 51 cases were further classified as high-virulence group. The median levels of CRP, ESR, NLR, and MLR were significantly higher in the FRI group than in the non-FRI group (p < 0.01). Similarly, the marginally significantly higher levels of CRP and NLR presented in the high-virulence group, compared to the low-virulence group (p < 0.1). The AUC areas of CRP, NLR, and CRP+NLR were 0.826, 0.650, and 0.873, respectively. We calculated the optimal cut-off points for CRP+NLR as diagnostic markers of high-virulent infection was 0.377. CONCLUSION: This study showed the incidence of FRI in high-risk lower extremity fractures was 8.9%, and identified preoperative serum biomarkers, including CRP, ESR, NLR, and PLR, as useful tools for assisting in the diagnosis of infection. Additionally, the combination of CRP with NLR played a discriminating clinical role in postoperative infections caused by different virulence. LEVEL OF EVIDENCE: Clinical study.