It is time to reconsider the classification of dens fractures: an anatomical approach

A clinical study was performed to evaluate a new classification for odontoid process fractures. The external and internal anatomy of the axis has been studied. The files of 97 patients with a fracture of the odontoid process admitted to our institution were reviewed and classified according to the proposed new classification. The method was tested for reliability and validity. The patients were followed for a mean period of 14 years, in order to evaluate the outcome of these fractures and to correlate it to the fracture type. Intraobserver and interobserver agreement was excellent with intraclass correlation coefficients at levels of 0.98 and 0.85, respectively. Four types of odontoid process fractures are distinguished. Type B fractures are associated with high risk of pseudarthrosis. Existing classifications are inadequate and misleading since they do not include all types of odontoid process fractures, nor they consider the internal anatomy of the odontoid process. Classification of the odontoid process fractures has to be reconsidered as novel-imaging technology has shown new patterns of fractures. The analysis of the imaging data in the present study justifies the new classification.