Relationship between ectopic calcifications and bone fragility depicted on computed tomography scan in 70 patients with systemic sclerosis

Background: A higher risk of osteoporotic fracture was described in systemic sclerosis patients than in healthy patients. Objective: To evaluate the relation between osteoporotic fracture risk measured by the scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) on computed tomography (CT) scan and the presence of ectopic calcifications: vascular, valvular and spinal. Methods: This monocentric retrospective study was performed on patients followed between 2000 and 2014 at Nancy University Hospital. Systemic sclerosis patients, according to ACR/EULAR 2013 criteria, followed from 2000 to 2014 and who underwent, during their follow-up, a CT including the first lumbar vertebra were included. The SBAC-L1 was measured with a threshold set at 145 Hounsfield units (HU). Vascular and spinal calcifications were studied on CT. For vascular calcifications, the Agatston score was used. Valvular calcifications were studied on echocardiography. Results: A total of 70 patients were included (mean age: 62.3 (+/- 15.6) years, women 88.5%). The mean SBAC-L1 was 157.26 (+/- 52.1) HU, and 35 patients (50%) presented an SBAC-L1 <= 145 HU. The reproducibility of the calcification evaluation was good, with kappa coefficients varying between 0.63 and 1. In univariate analysis, spinal and vascular calcifications were associated with an SBAC-L1 <= 145 HU, with ORs of 13.6 (1.6-113.3) and 8 (95%CI: 2.5-25.5), respectively. In multivariate analysis, the SBAC-L1 was not associated with the presence of any ectopic calcifications. The SBAC-L1 decreased with age (p = 0.0001). Conclusion: Patients with systemic sclerosis with an SBAC-L1 <= 145 HU were older, but they did not have more ectopic calcification.