The reliability of the Neer classification for proximal humerus fractures: a survey of orthopedic shoulder surgeons

BACKGROUND: The Neer classification is among the most widely used systems to describe proximal humerus fractures (PHF) despite the poor interobserver agreement. The purpose of this study was to verify whether or not blinded shoulder surgeons and trainees agree with the authors of articles published in the highest impact-factor orthopedic journals. METHODS: All articles regarding PHF published between 2017 and 2019 in the top 10 orthopedic journals as rated by impact factor were searched. Articles were included if the authors used the Neer classification to describe at least 1 PHF in the figures. Figures were extracted without the legend, and X-rays ± computed tomography scan images were included when available. An international survey was conducted among 138 shoulder surgeons who were asked to record the Neer classification for each de-identified radiograph in the publications. The type of fracture mentioned in the legend of the published figure was considered as the gold standard. RESULTS: Survey participants agreed with the published article authors in 55% of cases overall (range 6%-96%, n = 35). The most common response disagreed with the article authors in 13 cases (37%), underestimating the number of parts in 11 of 13 cases. The interobserver agreement between the 138 responders was fair (k = 0.296). There was an association between the percentage of concordant answers and greater experience (number of years of shoulder surgery practice) of the responders (P = .0023). The number of parts, the number or type of available imaging modalities, and the geographic origin of participants did not influence the agreement between responders and authors. DISCUSSION: In more than one-third of cases, specialized shoulder surgeons disagree with article authors when interpreting the Neer classification of de-identified images of PHF in published manuscripts. Morphologic classification of PHF as the sole basis for treatment algorithms and surgical success should be scrutinized.