Abstract
1. Thirty-seven cases of fracture of the dens have been studied.
2. The incidence of non-union was high: 64 per cent after apparently adequate closed treatment.
3. Possible causes of the high incidence of non-union have been studied : attention is drawn to the effect of displacement and to that of posterior displacement in particular.
4. Non-union of the dens with potential instability at the atlanto-axial joint is not acceptable in a patient who expects to lead a normal active life.
5. Atlanto-axial fusion is the method of choice in the treatment of instability ; once that has been secured, pseudarthrosis of the dens is no longer significant.