Vertebral fracture prevalence and measurement of the scanographic bone attenuation coefficient on CT-scan in patients with systemic sclerosis.

To study vertebral fracture (VF) prevalence and the scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) on computed tomography scans (CT-scans) in systemic sclerosis patients. This monocentric retrospective study included patients followed from 2000 to 2014 and fulfilling ACR/EULAR 2013 criteria for systemic sclerosis and who underwent a thoracic or thoraco-abdomino-pelvic CT-scan during their follow-up. Clinical characteristics for sclerosis and osteoporosis risk factors were collected. For CT-scan, the VFs were determined according to Genant's classification, the SBAC-L1 was measured in Hounsfield Units (HU), and a SBAC-L1 ≤ 145 HU (fracture threshold) defined patients at VF risk. Predictive factors for SBAC-L1 ≤ 145 HU were studied. A total of 70 patients were included [mean age, 62.3 (± 15.6) years, women 88.5%, diffuse sclerosis 22.9% (n = 16)]. On CT-scans, three VFs were detected in three patients (4.3%). The mean SBAC-L1 was 157.26 HU (± 52.1), and 35 patients (50%) presented a SBAC-L1 ≤ 145 HU. In multivariate analysis, only age (especially patients older than 63 years, OR = 1.08, CI 95% 1.04-1.13, p = 0.001) and calcinosis (OR = 6.04, CI 95% 1.27-28.70, p = 0.02) were independently associated with a SBAC-L1 ≤ 145 HU. On a large sample of patients with systemic sclerosis, the VF prevalence on CT-scan was low (4.3%) while 50% of the patients presented a SBAC-L1 ≤ 145 HU. Interestingly, the presence of calcinosis, periarticular calcifications or acro-osteolysis was linked with low SBAC-L1 and should lead to an osteoporosis screening, especially for patients under 63 years old.