A multicenter randomized controlled trial is performed in Sweden (Uppsala, Malmo and Stockholm) comparing surgery with posterior C1-C2 fusion and conservative treatment with a rigid collar. Follow up will be performed up to one year after start of treatment registering EQ5D, NDI and cervical CT scans. Mortality will be documented during follow-up. All direct and indirect costs of treatment will be registered and used for cost-effectiveness analysis.

50 patients, based on the following calculation of study size: The standard deviation for Neck Disability index, NDI, is just under 7, while "minimally clinical important difference" (MCID) is 7 points . That gives that 16 patients are needed in each group to get 80% power with a significance level of 5%. However, in the studied population the one year mortality rate is substantial, especially after a neck injury . In order to be able to draw conclusions from the study the investigators have elected to expand the study to 25 subjects in each group.

Follow up: 1w, 6w, 3m, 1y with CT, Questionaires: NDI, EQ5D. Bone density measurement at injury. Extension flexion x-ray after 1 year.

Inclusion Criteria:

• Acute displaced odontoid fracture type II according to Anderson and D'Alonzo, age 75 years or older. Displacement defined as 4 mm anterior translator displacement, any posterior translator displacement, or 10 degrees of angulation.

Exclusion Criteria:

• Any contraindication to surgery, anesthesia class ASA 4 or higher (Saklad 1941), severe senile dementia (defined as being admitted to a nursing home or hospital because of the dementia), anatomical or other prerequisites that makes an operation unsuitable.