Radiological study of the sacroiliac joints in vertebral ankylosing hyperostosis.

A radiological study of the sacroiliac joints was undertaken in 54 patients (32 males, 22 females) with vertebral ankylosing hyperostosis (VAH) and in 46 control patients (24 males, 22 females) matched for age and sex. The ages ranged from 38 to 90 years. The radiographs were taken in anteroposterior, oblique, and craniocaudal projections. The films were read for cranial, ventral, and caudal capsular ossifications, for ventral and caudal osteophytes, and for bone sclerosis. Cranial and/or ventral capsular ossifications were found in 28 (87.5%) males with VAH and in 4 (16.6%) control males (p less than 0.0005), but only in 2 females with VAH and no control female. Sacroiliac capsular ossifications in males with VaH are frequent from the onset, but complete bridging of the joint is not reached before the sixth decade. Women, either VAH or control, have more sacroiliac osteophytes than men. There were 11 out of 22 control women with osteophytes versus 4 out of 24 men (p less than 0.025). The incidence of osteophytes does not seem to increase with age after 50 years. Our findings support the idea of VAH being a distinct entity and not a major form of osteophytosis.