SAT0658 Quantitative analysis of joint structure by hr-pqct in patients with rheumatoid arthritis: correlation between cartilage loss and bone deterioration

Background HR-pQCT is a high-resolution CT dedicated to human extremities. It has been used for the study of rheumatoid arthritis (RA) in recent years, enabling quantitative analysis of bone erosion, bone microstructure, and joint space. Objectives The purpose of this study is to investigate a correlation between cartilage loss and bone deterioration (juxta-articular osteoporosis and erosion) in patients with RA by HR-pQCT. Methods Twenty patients with RA (70±8 years, 15 female, 5 male) participated in this study. The second and third MCP joints were scanned by second-generation HR-pQCT (XtremeCT II, Scanco Medical, Switzerland) at the voxel size of 61 µm. The following parameters were measured semiautomatically using dedicated software (TRI/3D-BON, Ratoc System Engineering, Tokyo) based on previous studies1–3. 1) Average joint space width (ave-JSW) of MCP joints, 2) bone microstructure of metacarpal head: volumetric bone mineral density (vBMD), trabecular thickness (Tb.Th), trabecular number (Tb.N), and structure model index (SMI), 3) total volume of erosions (ER-volume) on the metacarpal head. Results Ave-JSW of MCP joints was 1.47 (1.00–1.89) mm. vBMD of the metacarpal head was 131.4 (54.3–263.5) mg/cm3, Tb.Th was 213.1 (166–329.3) mm, Tb.N was 0.95 (0.69–1.50)/mm, and SMI was 1.68 (0.65–2.52). The total number of erosions was 31, and an average number of erosions on each metacarpal head was 0.9 (0–4). Total ER-volume on the metacarpal head was 1.96 (0–16.7) mm3. Ave-JSW had significant correlations with vBMD, SMI and ER-volume (R=0.37,–0,40, −0.42, p Conclusions Cartilage loss was correlated with juxta-articular osteoporosis and bone erosion in RA patients. Quantitative evaluation of total joint structure (joint space, bone microstructure, and erosion) by HR-pQCT would be useful for the pathophysiological research and drug development of RA. References [1] Burghardt AJ, et al. Ann Biomed Eng2013. [2] Yang H, et al. Int J Rheum Dis2017. [3] Chiba K, et al. Eular2017. Disclosure of Interest None declared