Bone mineral density in ankylosing spondylitis.

Vertebral osteoporosis is a well-recognized feature of ankylosing spondylitis (AS) and also the vertebral compression fractures due to osteoporosis are a common but frequently unrecognized complication of AS. Both may contribute to the pathogenesis of spinal deformity and back pain. The aim of this study was to measure vertebral and femoral neck bone mass in patients with AS by dual photon absorptiometry, to determine the prevalence of compression fractures and to examine the relationship between bone density and disease severity. We found that the bone mass was diminished in the lumbar spine in moderate AS versus mild forms but the patients with advanced disease had the highest BMD values. Examination of spinal radiographs revealed compression and biconcave fractures in 9 (40.9%) cases. Neither the duration of the disease and the degree of sacroiliitis, nor the disease activity assessed by laboratory and clinical parameters was found to significantly affect the results.