Aims: To examine whether functional radiography and functional magnetic resonance imaging (MRI) are equal to detect the extent of unstabile anterior atlantoaxial subluxation (aAAS) in rheumatic patients. Methods: The series consisted of 23 patients with unstable aAAS (diagnosed by functional radiography) examined by functional MRI because of a neck symptom. Twenty-two patients had rheumatoid arthritis and one had juvenile idiopathic arthritis. aAAS was diagnosed if the anterior atlanto-axial diameter (AAD) was > 3 mm and was considered unstable if the AAD differed > 2 mm between flexion and extension radiographs. The AAD was measured from radiographs (flexion and extension) and MRI images (flexion and neutral). Results: The extent of aAAS during flexion measured by radiography was greater than that found by MRI in all our 23 cases [the mean difference was 3 mm (95% CI: 2 to 4)]. In 4 patients (17%) MRI could not find aAAS. The difference between the AAD measurements during flexion by these two methods was substantial (i.e. , ≥ 4 mm) in 9 cases (39%). Severe aAAS (≥ 9 mm) was seen in 15 patients (65%) by functional radiography and in 4 (17%) by functional MRI. Conclusions: The magnitude of aAAS was often substantially smaller in functional MRI than in functional radiography. Thus one cannot rely on functional MRI alone; functional radiographs are needed to show the size of unstable aAAS.

Aims: To evaluate whether the atlantoaxial disorders (anterior atlantoaxial subluxation and atlantoaxial impaction) associate with destruction of shoulder or peripheral joints, and bone mineral density (BMD) in patients with long-term rheumatoid arthritis (RA). Methods: An inception cohort 67 patients with seropositive and erosive RA were followed up for 20 years. Cervical spine, shoulder, hand and foot radiographs, and the BMD of the lumbar spine and femoral neck were evaluated. Results: A positive relationship was detected between the occurrence of atlantoaxial disorders and the destruction of both shoulder (p < 0.001) and peripheral (p = 0.001) joints. In addition, the severity of atlantoaxial disorders positively correlated with the grade of destruction in the evaluated joints. Furthermore, a positive relationship was found between the occurrence of the atlantoaxial disorders and a decrease in BMD of the femoral neck (p = 0.019). Conclusions: Patients with severe RA and osteoporosis have an increased risk for atlantoaxial disorders, therefore the cervical spine radiographs of these patients should be analysed before major surgery and also at regular intervals. The co-existence of shoulder and cervical spine disorders makes the differential diagnosis of shoulder and neck pain challenging.

The outcome of operations performed on 38 patients for rheumatoid disorders of the cervical spine were analysed 10 or more years later. The mean age of the patients at the time of operation was 56 years (35 to 77); 32 had seropositive disease. The mean duration of the disease was 17 years (four to 36). Twenty-seven patients had painful anterior atlanto-axial subluxation (AAS), nine had subaxial subluxation alone and two had severe cranial subluxation of the odontoid, one also with subaxial subluxation. One patient died from postoperative staphylococcal septicaemia and another 18 died during the follow-up period. Patients with coincident cardiac or other diseases, and those with cranial subluxation of the odontoid of more than 3 mm had an increased mortality. Neither the patients' age nor the magnitude of AAS correlated with mortality. Of the 37 patients with occipitocervical pain, 30 were relieved and all the six patients with tetraparesis were improved. Of the 24 Gallie fusions only 12 were solidly united; patients with long-term cortisone treatment were more likely to develop pseudarthrosis. There was no correlation between clinical outcome and radiological result. Four patients had further operations to treat subluxation which developed below the fused segments.