BONE-MINERAL DENSITY IN ANKYLOSING-SPONDYLITIS - DEXA COMPARISON OF CONTROL SUBJECTS WITH MILD AND ADVANCED CASES

We have used dual-energy X-ray absorptiometry to measure bone mineral density (BMD) in patients with ankylosing spondylitis comparing 41 hea lthy control subjects and 33 patients with either mild or advanced ank ylosing spondylitis. A Norland XR-28 bone densitometer was used to mea sure the BMD of the lumbar spine and that of the head, trunk, arms, fe moral neck, Ward's triangle, legs, pelvis, and total body. Mild ankylo sing spondylitis was defined as that showing no or incipient syndesmop hytes between L1 and L5 vertebrae: we studied 16 men of mean age 37 ye ars and six women of mean age 37 years. Advanced ankylosing spondyliti s, in 11 men of mean age 42 years, showed a bamboo spine with bridging syndesmophytes across all disc spaces between L1 and L5. The mean BMD of the lumbar spine was significantly different in the patients and c ontrol subjects of the same sex (0.01< p < 0.05, analysis of variance) , being significantly reduced compared with control subjects in mild d isease (0.001 < p < 0.01, t-test) and significantly increased in advan ced disease over control subjects (0.01 < p < 0.05; t-test) and over p atients with mild disease (0.001 < p < 0.01; t-test). The relevance of these findings to the aetiology and pathogenesis of spinal deformitie s and other complications in ankylosing spondylitis is discussed.