Reliability and reproducibility of the STAB classification compared with Neer and AO classifications for proximal humerus fracture-dislocations: a retrospective cohort study of 57 patients.

BACKGROUND: Proximal humerus fracture-dislocations represent a challenging injury pattern with high complication rates. Current classification systems, including Neer and AO, have limitations in guiding treatment decisions for Neer type VI injuries. This study introduces and validates the STAB classification system, comparing its reliability and reproducibility with established classifications. METHODS: A retrospective cohort study of 57 patients with Neer type VI proximal humerus fracture-dislocations treated between January 2018 and December 2024 was conducted. Four observers with different experience levels independently classified all cases using AO, Neer, and STAB systems at two time points (2 weeks apart). Inter-observer and intra-observer agreements were assessed using Cohen’s kappa coefficients. Clinical outcomes including operation time, fracture healing time, Constant-Murley scores, and complication rates were compared among STAB subtypes. RESULTS: The STAB classification demonstrated higher reliability (inter-observer kappa = 0.94) and reproducibility (intra-observer kappa = 0.95) compared to AO (0.86 and 0.89) and Neer (0.83 and 0.92) classifications (all p < 0.05). Among 57 patients (Type T: 22, Type A: 20, Type B: 15), significant differences were observed in operation time (69.2 vs. 91.5 vs. 114.3 min, p < 0.001), fracture healing time (9.1 vs. 10.4 vs. 12.0 weeks, p < 0.001), Constant-Murley scores (83.2 vs. 74.8 vs. 61.5, p < 0.001), and complication rates (13.6% vs. 30.0% vs. 60.0%, p < 0.001). Closed reduction success rates were 90.9%, 58.3%, and 20.0% for Types T, A, and B, respectively. CONCLUSIONS: The STAB classification system demonstrates more reliability and reproducibility, compared to both Neer and AO classifications. By distinguishing fracture-dislocation patterns based on head-stem continuity, the STAB system provides valuable prognostic information and may help optimize individualized treatment strategies for Neer type VI proximal humerus fracture-dislocations. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.