The relationship between the Spine Deformity Index, biochemical parameters of bone metabolism and vascular calcifications: results from the Epidemiological VERtebral FRACtures iTalian Study (EVERFRACT) in dialysis patients

Background: The Spine Deformity Index (SDI) is a measure of vertebral fractures (VFs), providing information on both their number and severity. Methods: We evaluated the relationships between SDI and clinical, biochemical and arterial calcification parameters in 387 hemodialysis (HD) patients. VFs, assessed by quantitative vertebral morphometry, and vascular calcifications were identified in the same lateral spinal X-ray. To improve the detection of fracture severity, we created a corrected SDI (c-SDI), by dividing SDI for the number of VFs. We assessed routine biochemistry, bone-Gla-protein (BGP), undercaboxylated BGP (ucBGP), and matrix-Gla-protein (MGP). Results: VFs prevalence was 55.3%. HD patients with a SDI > 1 were more frequently males (p < 0.05), and had lower BGP (p < 0.01). Patients with a c-SDI > 1 had higher LDL-cholesterol (p < 0.05) and lower ucBGP (p < 0.05) and MGP (p < 0.05). Calcifications of the abdominal aorta (AAoC) were more frequent in patients with SDI > 1 (p < 0.05) and with c-SDI > 1 (p < 0.05). Multivariate logistic regression showed that male sex (OR 1.86, CI 1.20-2.91), age (OR 1.03, CI 1.01-1.05) and albumin = 3.5 g/dL (OR 0.54, CI 0.31-0.93) were predictors of a SDI > 1. Age (OR 1.05, CI 1.03-1.07), LDL-cholesterol (OR 1.74, CI 1.04-2.92) and ucBGP (OR 0.35, CI 0.18-0.70) were associated with c-SDI > 1. Conclusions: We conclude that the severity of VFs was associated with age, atherogenic factors and bone metabolism markers.