Cortical bone density and thickness alterations by high-resolution peripheral quantitative computed tomography: association with vertebral fractures in primary Sjogren's syndrome

Objectives. To evaluate volumetric BMD (vBMD), microarchitecture and strength and vertebral fractures (VFs) in primary SS (pSS). Methods. We evaluated 71 female pSS patients and 71 gender-, age-, and race-matched controls. Clinical data including risk factors for osteoporosis (OP) and fractures were collected through a standardized protocol. Areal BMD and VFs were analysed by DXA. Bone microarchitecture, vBMD and bone strength were assessed by high-resolution peripheral quantitative CT (HR-pQCT), a non-invasive method. Results. pSS patients and controls were comparable for age, BMI, calcium intake, smoking, menopause, sedentary lifestyle and family history of fractures (P > 0.05). OP or low BMD for the patient's age (33.8 vs 5.6%; P < 0.0001) and VFs (19.7 vs 5.6%; P = 0.043) were more frequent in patients than controls. HR-pQCT showed deterioration of cortical and trabecular components and strength at the radius, and of cortical components and strength at the tibia (P < 0.05) in patients compared with controls. pSS patients and controls were also analysed by multivariate analysis adjusted for age, ethnicity, prednisone use, weight and height, which showed that the pSS group had lower values of cortical vBMD, cortical thickness and apparent modulus (P < 0.05) at the radius and cortical vBMD and apparent modulus (P < 0.05) at the tibia. Patients with VFs had more cortical bone deterioration (cortical vBMD/cortical thickness) at the tibia compared with patients without VFs (P < 0.05). Conclusions. This study was the first to assess bone microarchitecture in pSS and demonstrated that cortical deterioration is the most important abnormality observed in pSS patients with VFs. This novel finding shows that this compartment contributes to vertebral fragility, suggesting that this non-invasive evaluation may be useful in the clinical practice. (AU)