The reliability and reproducibility of the Hertel classification for comminuted proximal humeral fractures compared with the Neer classification

The Neer classification is the most commonly used fracture classification system for proximal humeral fractures. Inter- and intra-observer agreement is limited, especially for comminuted fractures. A possibly more straightforward and reliable classification system is the Hertel classification. The aim of this study was to compare the inter- and intra-observer variability of the Hertel with the Neer classification in comminuted proximal humeral fractures. Four observers evaluated blinded radiographic images (X-rays, CT-scans, and CT-scans with 3D-reconstructions) of 60 patients. After at least two months classification was repeated. Inter-observer agreement on plain X-rays was fair for both Hertel (κ = 0.39; 95% CI 0.23-0.62) and Neer (κ = 0.29; 0.09-0.42). Inter-observer agreement on CT-scans was substantial (κ = 0.63; 0.56-0.72) for Hertel and moderate for Neer (κ = 0.51; 0.29-0.68). Inter-observer agreement on 3D-reconstructions was moderate for both Hertel (κ = 0.60; 0.53-0.72) and Neer (κ = 0.51; 0.39-0.58). Intra-observer agreement on plain X-rays was fair for both Hertel (κ = 0.38; 0.27-0.59) and Neer (κ = 0.40; 0.15-0.52). Intra-observer agreement on CT-scans was moderate for both Hertel (κ = 0.50; 0.38-0.66) and Neer (κ = 0.42; 0.35-0.52). Intra-observer agreement on 3D-reconstructions was moderate for Hertel (κ = 0.55; 0.45-0.64) and substantial for Neer (κ = 0.63; 0.48-0.79). The Hertel and Neer classifications showed a fair to substantial inter- and intra-observer agreement on the three diagnostic modalities used. Although inter-observer agreement was highest for Hertel classification on CT-scans, Neer classification had the highest intra-observer agreement on 3D-reconstructions. Data of this study do not confirm superiority of either classification system for the classification of comminuted proximal humeral fractures