Calcaneal fracture outcome score (CFOS): A novel outcome-based prognostic CT grading for calcaneal fracture reduction

While radiographic reduction quality is considered a key determinant of outcome in intraarticular calcaneal fractures, its quantification remains inconsistent and often unidimensional. Existing radiographic parameters only partially reflect the complex joint surface restoration while gradings often lack correlation to clinical outcomes. This study introduces the Calcaneal Fracture Outcome Score (CFOS), a composite score integrating joint-specific deformities and patient-level prognosticators to improve outcome prediction.

Postoperative CT scans from 80 patients with surgically treated calcaneal fractures were evaluated for residual step, gap, and angulation at the posterior facet (PF) and calcaneocuboid (CC) joint. Additional parameters included Boehler's angle, Gissane's angle, Sanders classification, smoking status, and comorbidity burden. All variables were z-standardized and entered into a LASSO regression with 5-fold cross-validation. A weighted score (CFOS) was computed per patient and correlated with PROMS (VAS-FA; SF-12).

Higher CFOS grades were associated with significantly worse outcomes, i.e. posttraumatic osteoarthritis (p<0.001), VAS-FA (p=0.035) and SF-12 PCS (p=0.010), outperforming the traditional grading established by Kurozumi et al and adapted by Nosewicz et al. with a mean positive predictive value of 90 %.

The CFOS offers a clinically intuitive, multidimensional assessment of reduction quality and provides robust predictive value for postoperative functional outcome.

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