Ankylosing spondylitis: patterns of radiographic involvement--a re-examination of accepted principles in a cohort of 769 patients.

PURPOSE: To re-examine the patterns of radiographic involvement in ankylosing spondylitis (AS).
MATERIALS AND METHODS: This prospective study had institutional review board approval, and 769 patients with AS (556 men, 213 women; mean age, 47.1 years; age range, 18-87 years) provided written informed consent. Radiographs of the cervical spine, lumbar spine, pelvis, and hips were scored by using the Bath Ankylosing Spondylitis Radiology Index (BASRI) by an experienced radiologist. Differences in sacroiliitis grade between right and left sacroiliac joints, frequency of cervical- and lumbar-predominant involvement by sex, frequency of progression to complete spinal fusion, and association between hip arthritis and spinal involvement were computed for the cohort overall and for subgroups defined according to duration of AS in 10-year increments.
RESULTS: Symmetric sacroiliitis was seen in 86.1% of patients. Lumbar predominance was more common during the first 20 years of the disease, after which the cervical spine and lumbar spine were equally involved. Men and women were equally likely to have cervical-predominant involvement. Complete spinal fusion was observed in 27.9% of patients with AS for more than 30 years and in 42.6% of patients with AS for more than 40 years. Patients with BASRI hip scores of 2 or greater had significantly higher BASRI spine scores.
CONCLUSION: There were no sex differences in cervical-predominant involvement in AS. Hip arthritis was strongly associated with worse spinal involvement. © RSNA, 2010