Vertical fractures of the dens.

PURPOSE To establish the mechanism of injury that causes vertical fractures of the dens. METHODS Over a 3-year period, 30 patients with dens fractures were seen at our institution. From these records, we identified and retrospectively reviewed the radiographs (n = 3), CT scans (n = 3), and MR images (n = 1) of three patients with vertical fractures of the dens to assess the characteristics of these fractures and other associated injuries. Medical records of these three patients were also reviewed in an attempt to elucidate the mechanism of injury. Additionally, we reviewed three cases reported in the literature and compared them with findings in our patients. RESULTS In all patients, radiographs showed fractures involving the base of the dens (type 2), but they did not show the vertical fractures. Axial CT scans and sagittal reformations clearly showed the vertical dens fractures. One patient also had a unilateral Jefferson-type fracture. The atlantodental space was preserved in all patients. In one patient, there was posterior displacement of the fractured dens. All three patients were neurologically normal. After a 6-month period of external fixation, two patients healed adequately. CONCLUSION Vertical dens fractures probably result from axial loading and slight extension of the head. In our cases, vertical dens fractures were accompanied by other fractures of C-1 and C-2. CT with sagittal reformations is the ideal imaging method to detect vertical dens fractures.