The authors sought to determine the incidence of lumbar disc changes among 104 patients with rheumatoid arthritis, RA. The subjects had had RA for 10 years or more. It is well known that 25 to 90 percent of patients with RA will have cervical spine involvement. The authors used radiographs and magnetic resonance imaging to examine a total of 520 disc levels in the lumbar spine. They then sought to determine if disease activity using Ochi’s classification, serum C-reactive protein, rheumatoid factor, platelet count, and Lansbury index correlated with radiographic findings. The subjects were evaluated whether or not they had report of low back pain.
The authors were looking for erosive or sclerotic changes of the anterior rim of the vertebral bodies, irregularity of vertebral end plate, and narrowing, fusion, or collapse of the intervertebral discs. The authors used a grading scale from zero to four. Zero was normal. Grade I was characterized by erosive or sclerotic changes of the anterior rim of the vertebral bodies on Xray, and signal intensity changes at the same level on MRI. Grade II lesions demonstrated irregularity of the vertebral end plates on plain Xray and on MRI. Grade III lesions where characterized by collapse of the intervertebral discs or the vertebral bodies. The authors then considered type A and B lesions for those lesions graded as II or III. Type A lesions were characterized by narrowing of the intervertebral space. Type B lesions had maintained intervertebral space or ballooning of the disc.
The authors found that 45 percent of patients had at least one lumbar lesion. The two types of lumbar disc lesions related to RA were disc narrowing and disc ballooning. Only one patient was found to have both a type A and type B lesion in their lumbar spine. The authors propose that there may be two types of RA. One may destroy mainly cartilage, and the other subchondral bone.
Ochi’s classification appeared to be useful in predicting the likelihood of lumbar disc lesions. Ochi’s classification includes three types based on the number of peripheral joints involved. Forty five of patients were included in the least erosive subset, LES, 28 patients in the more erosive subset, MES, and 31 patients in the mutilating disease subset, MUD.
The MUD patients had 61 percent grade II or III lesions. The authors felt that the extent of lumbar spine involvement correlated with the extent of RA in peripheral joints.
Laboratory values for CRP, rheumatoid factor, and platelet count did not seem to correlate with lumbar pathology.