A pilot study of a computed tomography volumetric analysis technique to determine severity of injury and prognosis for OTA 42A-C open tibial diaphyseal fractures

PURPOSE: This pilot study evaluated a novel computed tomography (CT)-based volumetric analysis tool for open tibial fractures. We hypothesized that the volumetric injury ratio (VINJ/VUNINJ), a quantitative comparison of injured with contralateral uninjured limb segments, would correlate with clinical outcomes and serve as a prognostic marker. METHODS: A retrospective review of a tibial fracture registry was conducted at a single academic institution (2014-2024). Eligible patients were older than 18 years old with preoperative bilateral lower extremity CT imaging, high-energy injuries, and ≥6 months of follow-up. Demographics, Charlson Comorbidity Index (CCI), injury features, and outcomes including fracture-related infection (FRI), amputation, and nonunion were collected. Tissue volume was measured at the fracture midpoint and 5 cm proximal and distal, with corresponding contralateral measurements. VINJ/VUNINJ was calculated, and logistic regression estimated complication risk. The primary endpoint was a composite complication (FRI, amputation, or nonunion). Discrimination was assessed using AUROC and compared with the Gustilo-Anderson (GA) classification via the DeLong test. The Youden Index identified an optimal risk threshold. Power analysis estimated sample size requirements for a future validation study. RESULTS: Fifteen patients met inclusion criteria (mean age 36.1 ± 13.5 years). GA distribution: 60% II, 6.7% IIIa, 26.7% IIIb, and 6.7% IIIc. The volumetric model (log[p/(1-p)] = -110.964 + 100.011 × VINJ/VUNINJ) demonstrated a trend toward improved discriminatory ability compared with the GA model (AUROC: 0.944 vs 0.769, P = 0.068). A Youden-derived threshold (0.539) classified 5 patients (33.3%) as high-risk; all developed complications compared with 10% in the low-risk group (100% vs 10%, P = 0.001). Power analysis indicated that detecting a twofold increase in complications would require ∼23 patients per arm (46 total). CONCLUSION: This pilot study introduces a CT-based volumetric ratio as a quantitative tool for risk stratification in open tibial fractures. Findings suggest superior prognostic accuracy compared with GA, supporting prospective validation in larger patient cohorts.