Background Patients with rheumatoid arthritis (RA) are associated with an increased risk of periarticular and generalized bone loss. A 3D high resolution peripheral quantitative computed tomography (HR-pQCT) system has been developed to perform in vivo human measurements of bone geometry, volumetric bone mineral density (vBMD) and microarchitecture on peripheral skeletal sites such as the radius and tibia. HR-pQCT also holds great potential to measure morphological, densitometric and microstructural changes of periarticular bones in RA.

Objectives By using HR-pQCT, we aimed: 1) to investigate whether bone geometry, vBMD and microarchitectural measures of the distal radius are significantly associated with those of the 2nd metacarpal; 2) to investigate clinical factors influencing bone geometry, vBMD and microarchitectural measures of the distal radius and 2nd metacarpal.

Methods This cross-sectional study involved 100 female RA patients. HR-pQCT at distal radius and 2nd metacarpal head, both of the non-dominant forearm, were performed to assess bone geometry, cortical and trabecular vBMD and microarchitecture.

Results The cohort had a mean (SD) age of 53.4 (9.3) years old and a mean (SD) disease duration of 9.1 (7.8) years. Sixty-seven patients were post-menopausal. The cohort had mild disease activity, with mean (SD) Disease Activity Score in 28 Joint (DAS28) score of 3.7 (1.2), and mild disability, with median (range) of Health Assessment Questionnaire (HAQ) score of 0.38 (0-2.6). Forty-nine patients had erosive disease at wrists or hands. There were week correlations (range of r: 0.33-0.36) between total, cortical and trabecular area at distal radius and those at 2nd metacarpal. Moderate correlations were found between total (r=0.63) and trabecular (r=0.56), but not cortical (r=0.38), vBMD at distal radius and those at 2nd metacarpal. There were also weak to moderate correlations between microarchitectural measures at distal radius and those at 2nd metacarpal, with the strongest correlation seen in the ratio of trabecular bone volume and tissue volume (r=0.57) and the weakest one seen in trabecular thickness (r=0.20). Clinical factors related to disease severity, including disease duration, the number of deformed joints, HAQ score, and erosive disease, significantly correlated with bone geometry, vBMD and microarchitecture at both distal radius and 2nd metacarpal. However, clinical factors related to disease activity, including the number of swollen joints, C-reactive protein level, and DAS28 score, were more likely to be correlated with bone geometry, vBMD and microarchitecture at 2nd metacarpal, but not those at distal radius.

Conclusions Bone geometry, vBMD and microarchitectural measures of the distal radius significantly correlated with those of the 2nd metacarpal, but at a weak to moderate level of correlation. It appears that the clinical characteristics of RA contribute differently to bone quality at peripheral skeletal site and that at periarticular site.

1. Fouque-Aubert A, Boutroy S, Marotte H et al. Assessment of hand bone loss in rheumatoid arthritis by high-resolution peripheral quantitative CT. Ann Rheum Dis 2010;69(9):1671-6.

Disclosure of Interest None Declared