Single photon emission computed tomography and the source of lumbar pain in advanced ankylosing spondylitis

Spinal pain is a characteristic of ankylosing spondylitis (AS) that can persist indefinitely, even when laboratory indices of inflammation are normal. We used single photon emission computed tomography to study 28 symptomatic patients with established disease, half of whom had complete ankylosis of sacroiliac and one-third of whom had complete ankylosis of intervertebral joints. Pain in the lumbar region was associated with increased uptake of isotope in the facetal joints. There was no relationship of pain with impaired lumbar flexion, erythrocyte sedimentation rate, serum immunoglobulin A nor with radiologic change in the sacroiliac, intervertebral and facetal joints. We suggest that persistent lumbar pain with AS might be associated with facetal joint inflammation and that treatment directed at these sites may be rewarding.