[Accident-induced pseudarthroses of the dens axis. Etiology, follow-up and therapy].

In a retrospective analysis the significance of internal fixation of unstable and symptomatic non-union of the odontoid was evaluated. In all but one cases a type II fracture of the odontoid was the underlying cause for the pseudarthrosis. The time interval between trauma and definitive diagnosis varied between 6 months and 30 years. All patients asked for medical advice because of acute neck pain; in three cases additional neurological deficits were notified. In all but one case the pseudarthrosis was classified as unstable on flexion-/extension views. The occurrence of neurological deficits showed a positive correlation with the amount of dislocation of the pseudarthrotic odontoid. Nine out of 10 patients underwent internal stabilisation of the non-union. Reoperation because of persistent instability/failure of stabilisation had to be performed in two cases (22.2%). At follow-up all 9 patients were pain-free. The neurological deficits in two patients had improved significantly. According to our experience internal stabilisation in unstable non-union of the odontoid is recommended to achieve significant reduction of the pain level. Also improvement of the neurological deficits can be expected depending on the duration of the symptoms.