OP0052 Cortical bone loss is an early feature of axial spondyloarthritis. (15th June 2017) - Haschka, J
Abstract : Background: Systemic bone loss is a well-known and severe consequence in axial spondyloarthritis (axSpA). To date deterioration of bone microstructure has only been described in patients with long-standing ankylosing spondylitis while bone microstructure has not been assessed in axSpA. Objectives: The aim of the present study was to investigate bone microstructure, geometry and volumetric bone mineral density (vBMD) using high resolution peripheral quantitative CT (HR-pQCT) in a cohort of axSpA patients at an early stage of disease and to search for potential factors for deterioration of bone microstructure. Methods: An inception cohort of 101 axSpA patients and 50 healthy controls of similar age and sex was assessed for geometric, volumetric and microstructural parameters of bone using HR-pQCT scanning of the radius. Additionally, demographic and disease specific characteristics of SpA patients were recorded. Results: SpA patients and controls were comparable in age (median (IQR) 45.0 (15.0) vs. 44.76 (26.0) years, p=0.917), sex (female 41.6% vs. 40%, p=0.852) and BMI (median (IQR) 26.3 (6.5) vs. 23.8 (5.2), p=0.118). 75% of patients showed HLA-B27 positivity. Median disease duration was 6.5 (9.0) years, 58.4% of patients were on biological treatment and 14.9% of patients in disease remission according to ASDAS-CRP. Geometric and microstructural analysis by HR-pQCT revealed a significantly reduced cortical area (p=0.022) and cortical thickness (p=0.006) in SpA patients compared to controls. No differences in cortical porosity (p=0.685), trabecular geometry or microstructure were detected. Total and cortical vBMD were significantly reduced in SpA patients (p=0.042 and p=0.007), while there was no difference in trabecular vBMD (p=0.376). Patients with a short disease duration <2 years (n=46) showed a significant reduction of cortical thickness and cortical area (p=0.050 and p=0.032) compared to controls. Patients with a disease duration >2 years (n=55) additionally developed a decrease of cortical and total vBMD (p=0.004 and p=0.036). Multivariate regression models identified male sex to be associated with lower cortical vBMD and female sex with lower trabecular vBMD. History of prednisolone treatment (>5mg >3months) was associated with lower trabecular vBMD, and disease duration with higher trabecular vBMD. Remission status, treatment with TNF inhibitors, HLA-B27 status and presence of peripheral arthritis did not influence bone microstructure independently. Conclusions: Bone microstructure in SpA patients is primarily characterized by deterioration of cortical bone. Cortical bone loss starts early and is evident within the first 2 years of disease. Disclosure of Interest: None declared