Digital tomosynthesis as a new diagnostic tool for evaluation of spine damage in patients with ankylosing spondylitis

We aimed to compare digital tomosynthesis (DTS) with radiographs for the assessment of spinal bone damage in patients with ankylosing spondylitis (AS). The study comprised 68 patients with AS who underwent both DTS and radiographs of the cervical and lumbar spine on the same day. Spinal bone damage was assessed using the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) and the presence of facet joint damage. The Wilcoxon signed-rank test and McNemar’s test were used to compare spinal bone damage between the two modalities. In 68 AS patients with mean 4.5 years of disease duration, the mean mSASSS was 11.7 ± 11.3 with radiographs and 13.1 ± 11.5 with DTS (p = 0.001). A grade 1 (erosion, sclerosis, or squaring) score in the mSASSS system was higher with DTS than with radiographs (p = 0.001), but grade 2 (syndesmophyte) and grade 3 (bridge) scores (p > 0.005 each) were not. In particular, the grade 1 score was higher with DTS than with radiographs at the cervicothoracic (p < 0.001) and thoracolumbar (p = 0.003) junctions. With regard to facet joint damage, erosion/sclerosis of facet joints was better depicted by DTS than by radiographs in the cervical (54.4 vs. 22.1%, p < 0.001) and lumbar spine (72.1 vs. 11.8%, p < 0.001). DTS depicted more subtle damage of spinal vertebrae in patients with AS than radiographs did. Moreover, erosion/sclerosis of facet joints was better detected with DTS than with radiographs.