Incidence of subaxial subluxation in patients with generalized rheumatoid arthritis who have had previous occipital cervical fusions.

A retrospective study of 79 patients with rheumatoid arthritis was undertaken to determine the incidence of subaxial subluxation after upper cervical fusions. Fifty-five patients had isolated axial subluxation and underwent atlantoaxial fusion. Twenty-four underwent occipitocervical fusion for atlantoaxial subluxation and superior migration of the odontoid. The two groups were comparable in age, duration of disease, and time to follow-up (atlantoaxial fusion, 65.4 months; occipitocervical fusion, 72.6 months). Fusion rates were comparable: 80% atlantoaxial fusion and 90.1% occipitocervical fusion. Of the occipitocervical fusion patients, 36% developed subaxial subluxation requiring surgery at an average of 2.6 years after fusion. Of the atlantoaxial fusion patients, 5.5% developed subaxial subluxation requiring surgery after an average of 9 years after fusion. No patient with atlantoaxial fusion developed superior migration of the odontoid. Subaxial subluxation requiring surgery developed early in patients after occipitocervical fusion. This was not true of atlantoaxial fusion. Early atlantoaxial fusion seemed to prevent the development of superior migration of the odontoid. When occipitocervical fusion is necessary and early subaxial subluxation is present, longer fusions or occipitocervicothoracic fusion should be strongly considered.