Floating Knee Severity Score (FKS): A Novel Multidimensional Prognostic Model for Predicting Functional Outcomes...

Purpose: Floating knee (FK) injuries are complex high-energy traumas associated with poor functional outcomes. This study aimed to identify independent predictors of functional prognosis and to develop a novel, multidimensional scoring system to predict long-term functional outcomes. Methods: A retrospective analysis was performed on 182 adult patients with ipsilateral femur and tibia fractures treated between January 2010 and December 2023. Functional outcomes were assessed using the Karlström-Olerud criteria and dichotomized as excellent-good versus fair-poor. Variables significant in univariate analysis were entered into a multivariate logistic regression model. Independent predictors were used to construct the FKS-score. Predictive performance was evaluated using ROC analysis. Results: Of the 182 patients, 103 (56.6%) achieved excellent-good outcomes, while 79 (43.4%) had fair-poor results. Multivariate analysis identified Fraser IIA-B (OR 2.12), Fraser IIC (OR 3.85), Gustilo I-II (OR 1.42), Gustilo IIIA-B (OR 2.61), Gustilo IIIC (OR 3.22), segmental fractures (OR 2.18), extensor mechanism injury (OR 2.04), vascular injury (OR 4.89), intra-articular extension (OR 1.92), and patella fracture (OR 1.76) as independent predictors of poor functional outcome. The FKS-score, ranging from 0 to 15, demonstrated high predictive accuracy (AUC = 0.89). An optimal cut-off value of ≥9 points yielded a sensitivity of 78% and specificity of 85%. Conclusions: The FKS-score is the first comprehensive prognostic scoring system specifically developed for floating knee injuries. It provides a reliable, practical tool for early risk stratification and the prediction of long-term functional outcomes, thereby supporting clinical decision-making and patient counseling.