Spine structural lesions in ankylosing spondylitis: comparison between radiographic and opportunistic...

The aim of this study was to evaluate the prevalence and severity of spinal structural lesions on radiographs versus opportunistic thoraco-abdomino-pelvic CT (TAP CT) in ankylosing spondylitis (AS).

This monocentric retrospective pilot study included AS patients meeting the modified New York criteria for radiographic sacroiliitis who had both spine radiographs and TAP CT within 12 months. On CT, 36 anterior vertebral corners (C7-S1) were graded for erosion/squaring (grade 1), syndesmophytes (grade 2), and bone bridges (grade 3). Posterior facet joint ankylosis was recorded as present or absent, generating anterior, posterior, and total CT-scores (0-216). Radiographic assessment was performed using the Radiographic Ankylosing Spondylitis Spinal Score (RASSS, 0-84).

A total of 142 patients were included (median age 54 years [47-62], 70.4% male, 77.6% HLA-B27 positive, median disease duration 14 years [6-26], 43.5% treated with bDMARDs). Structural spinal damage was identified in 62.6% by RASSS and 71.8% by CT. Anterior vertebral lesions were present in 94 patients, and 68 exhibited posterior facet joint ankylosis. Mean RASSS and total CT-scores were 13.1 (±20.0) and 37.2 (±47.2), respectively. Total CT-score correlated with age, disease duration, male sex, HLA-B27 positivity, inflammatory bowel disease, and CRP >5 mg/L (p<0.05). Multivariate analysis confirmed associations with age, disease duration, male sex, and CRP. Intra-reader reliability was excellent for both modalities (ICC >0.90).

Opportunistic TAP CT is a reliable, reproducible, and complementary imaging tool to radiography for evaluating anterior and posterior spinal structural damage in AS.