Predictive value of a preoperative computed tomography-derived perifracture soft-tissue envelope index for fracture-related infection after open reduction and internal fixation of tibial plateau fractures.

BACKGROUND: Fracture-related infection (FRI) is a major complication after open reduction and internal fixation (ORIF) of tibial plateau fractures. This study evaluated whether a preoperative computed tomography (CT)-derived soft-tissue envelope index (STEI) was associated with 12-month FRI and whether it provided incremental value for preoperative risk stratification. METHODS: This retrospective single-center cohort study included 347 adults with unilateral closed tibial plateau fractures who underwent ORIF between January 2020 and December 2024. The STEI was defined as the mean ratio of soft-tissue area to osseous contour area at three axial levels located 5, 15, and 25 mm below the tibial plateau articular reference plane. FRI was adjudicated according to consensus confirmatory criteria. Every included patient had a dated, traceable, archived outcome record generated during clinical care after the 12-month anniversary of definitive ORIF. Non-FRI status required both the absence of any confirmatory criterion during the first postoperative year and explicit confirmation in a subsequent archived record. Logistic regression, receiver operating characteristic (ROC) curve analysis, calibration, decision curve analysis, and internal validation using 1,000 bootstrap resamples were performed. RESULTS: The median follow-up duration was 12.8 months [interquartile range (IQR), 12.2-13.9], and 41 patients developed FRI (11.82%). The STEI was higher in the FRI group than in the non-FRI group (3.08 ± 0.52 vs. 2.51 ± 0.48; P < 0.001), and the interobserver intraclass correlation coefficient (ICC) was 0.946 [95% confidence interval (CI), 0.920-0.963]. The STEI remained independently associated with FRI [adjusted odds ratio (OR) per 0.10-unit increase, 1.21; 95% CI, 1.12-1.31; P < 0.001]. The combined preoperative model yielded an area under the ROC curve (AUC) of 0.865 (95% CI, 0.806-0.923), an optimism-corrected AUC of 0.847, and a calibration slope of 0.91, and provided greater net benefit across threshold probabilities of 5%-30%. CONCLUSION: The preoperative CT-derived STEI was independently associated with 12-month FRI after ORIF of closed tibial plateau fractures and added predictive information beyond clinical and fracture-related factors. Prospective multicenter external validation of both the index and the combined model is required.