[Atlanto-axial lateral mass osteoarthritis. Three case reports and review of the literature].

This report describes three cases of symptomatic unilateral C1-C2 mass osteoarthritis. The patients were all female aged 67, 62 and 59 years. One patient had a history of rheumatoid arthritis. Unilateral occipital pain was the main symptom. Neuroradiological work-up included open mouth anteroposterior radiograph, flexion/extension lateral radiograph of the cervical spine, CT scan with coronal and sagittal reconstruction and MRI. Findings allowed differential diagnosis with tumoral or infectious disease of upper cervical spine and ruled out C1-C2 instability. CT scan and MRI permitted precise operative planning by determining the course of vertebral artery in the C1 and C2 vertebrae. Two patients were treated by CT scan guided steroid injection. The third patient was treated by C1-C2 arthodesis after failure of conservative treatment.