Syndesmophytes Less Frequent at Vertebral Rim Near Aorta in Ankylosing Spondylitis

Syndesmophytes occurred less frequently and were smaller at the thoracolumbar vertebral rim near the aorta in patients with ankylosing spondylitis (AS), suggesting that factors other than vertebral inflammation may affect syndesmophyte development, according to study data published in Annals of Rheumatic Disease.  

Investigators conducted a cross-sectional study to examine syndesmophyte frequency in the vertebral rim among patients with AS. Adult patients who met modified New York criteria for the classification of AS had spine radiographs and spine computed tomography (CT) scans taken. Sixty patients provided thoracolumbar CT scans, providing data for 6 intervertebral disk spaces (IDSs): T10-T11, T11-T12, T12-L1, L1-L2, L2-L3, and L3-L4. An additional 22 patients also underwent CT scans of the mid-thoracic spine, providing data for 5 additional IDSs: T5-T6, T6-T7, T7-T8, T8-T9, and T9-T10. In examining each IDS scan, investigators divided the entire vertebral rim (360°) into sectors of 5° each. Height for ascending and descending syndesmophytes was computed for each sector, as well as the sector distance from aorta. According to this semiautomated method, syndesmophyte size and frequency were assessed in relation to the location of the aorta.

Of 60 enrolled patients, 54 had syndesmophytes in the 180° region of the vertebral rim neighboring the aorta in at least 1 IDS; these 54 participants contributed data to subsequent analyses.

The majority of patients were middle-aged men with “long-standing” AS. Axial CT images indicated that syndesmophyte frequency was lowest at the aorta-adjacent sector and progressively increased at sectors further from the aorta. Mean syndesmophyte height also followed a similar trend. The association between aortic distance and syndesmophyte frequency/height was most pronounced at T10-11, T11-12, T12-L1, and L1-L2 and less pronounced at T7-T8, T8-T9, and L2-L3. The minimum distance from aorta to vertebral rim (minAV) varied among IDSs, with mean values <3 mm at the thoracolumbar junction and >4 mm for other IDSs. Syndesmophytes were not present in the abutting sector when minAV distance was <2.0 mm. However, syndesmophytes became progressively more common as minAV distance increased beyond 3.0 mm. According to generalized estimating equations models, both the location of the angular sector on the rim in relation to the aorta and minAV distance were associated with the likelihood of a syndesmophyte at a given angular sector (both P <.0001).

These data suggest that factors other than vertebral inflammation may influence syndesmophyte development in patients with AS. Additional research is necessary to further explicate the role of the aorta in vertebral morphology.

Reference

Tan S, Dasgupta A, Flynn JA, Ward MM. Aortic-vertebral interaction in ankylosing spondylitis: syndesmophyte development at the juxta-aortic vertebral rim [published online April 6, 2019]. Ann Rheum Dis. doi:10.1136/annrheumdis-2018-214675