Dynamics of syndesmophyte growth according to multispiral computed tomography data in patients with ankylosing spondylitis

Background. Syndesmophitis is a pathognomonic sign of damage to the axial skeleton in ankylosing spondylitis (AS), however, the characteristics of its formation and growth are poorly understood.

The aim – to evaluate the dynamics of changes of syndesmophyte growth according to multispiral computed tomography (MSCT) data in patients with ankylosing spondylitis.

Materials and methods. The data of MSCT of the thoracic or lumbar spine were analyzed in 10 patients with AS (8 men). Changes in the dynamics of the length of syndesmophytes and the width at their base were studied. Only patients who had previously been diagnosed with at least 1 syndesmophyte in the thoracic or lumbar spine were included in the study. The average age of patients included in the analysis was 43.5±8.4 years, with an average disease duration of 16.4±7 years. All patients underwent repeated MSCT. The average follow-up period was 16 months (from 9 to 26 months). 9 patients were positive by HLA-B27. The median age of disease onset was 31 [22; 49] years. All patients had high activity initially.

Results. On 226 endplates of thoracic (216 in 9 patients) and lumbar (10 in 1 patient) vertebrae in 10 patients with AS, a total of 90 syndesmophytes (from 1 to 9 syndesmophytes in 1 patient) were detected on MSCT during 2 observation periods, of which 44 (48.9%) were present initially and 46 (51.1%) – during the repeat examination. Accordingly, 2 (4.5%) new syndesmophytes appeared during the observation period. The minimum length of syndesmophytes was 2.4 mm, and the maximum was 14.3 mm, while the width ranged from 4.9 to 23.0 mm. A significant (>10%) increase in the length of syndesmophytes was observed in 27 (61.4%) cases, and in 2 (4.5%) of them the increase was more than half of the initial one. The width of syndesmophytes and their changes also varied widely. In 2 patients it decreased by more than 10%, and in 18 (40.9%) it increased significantly during the observation period. In 15 (34.1%) syndesmophytes the length, and in 24 (54.5%) the width during the analyzed period remained virtually unchanged or was within ±10% of the initial size. The growth rate and sizes of different syndesmophytes, even in the same patient, often varied greatly.

Conclusions. In this study, an attempt was made to evaluate the dynamics of changes of linear sizes of syndesmophytes in patients with AS according to CT scans of the thoracic or lumbar spine. Preliminary data show that practically every syndesmophyte tends to grow, and the growth rate of different syndesmophytes, even in the same patient, can vary greatly. It is noteworthy that some syndesmophytes decreased in dynamics, possibly due to drug therapy, although possible errors in the analysis of parameters cannot be excluded. The data obtained by us and data from other authors suggest that AS may regress in some patients.

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