Background Generalized bone loss at axial and peripheral bone is a common feature of rheumatoid arthritis (RA) and is one of the determinants of the fracture risk. The relationship between decreased areal bone mineral density (aBMD) and fracture is less clear in RA than in postmenopausal osteoporosis. High-resolution peripheral quantitative computed tomography (HR-pQCT) is an in vivo imaging technique capable of assessing volumetric BMD (vBMD) and microarchitecture of cortical and trebecular bone at the distal radius.

Objectives To assess volumetric density, microarchitecture and bone strength at the distal radius in female patients with RA in comparison to healthy controls with HR-pQCT.

Methods This cross-sectional study involved 66 female RA patients (age 48.9±8.2 years; disease duration 10.7±8.2 years) and 66 age-matched healthy females (age 48.8±8.2 years). aBMD of femoral neck, total hip, lumbar spine (L1-4) and forearm was measured by dual-energy X-ray absorptiometry (DXA). HR-pQCT at distal radius and image-based finite-element analyses (FEA) were performed to assess cortical and trabecular vBMD, microarchitecture and bone strength.

Results There was no difference in age, body height and percentage of postmenopause between RA patients and controls. RA patients had significantly lower body weight (55.0±10.5kg vs. 58.3±7.3kg, p=0.038). aBMD at femoral neck, total hip, lumbar spine and forearm did not differ significantly between the 2 groups. However, at distal radius, compared with controls, RA patients had significantly lower volumetric cortical (p=0.004) and trabecular bone density (p=0.024), lower bone/tissue volume (p=0.023), higher trabecular separation (p=0.025), increased inhomogeneity of trabecular network (p=0.039), and increased structure model index (SMI). These alterations were independent of menstrual status. After adjusted for age, body weight, body height and aBMD of forearm by DXA, differences between RA and controls remained significant for cortical vBMD, trabecular separation, inhomogeneity of the trabecular network and SMI. Using FEA, there was no significant difference in stiffness, failure load and apparent modulus between RA and controls. Percentage difference in cortical and trabecular vBMD between RA and controls significantly correlated with disease activity (C-reactive protein, erythrocyte sedimentation rate, Disease Activity Score in 28 joints) and severity parameters (Health Assessment Questionnaire score and disease duration), while percentage difference in trabecular microarchitecture correlated with disease duration. Use of glucocorticoids did not influence vBMD or microarchitecture or bone strength in RA patients.

Conclusions Patients with RA are associated with low vBMD and microarchitectural alterations of both cortical and trabecular bone at distal radius that are partially independent of demographics and aBMD assessed by DXA. Results from our study may increase understanding of the role of microarchitectural deterioration in bone fragility in patients with RA.

1. Haugeberg G et al. Bone mineral density and frequency of osteoporosis in female patients with rheumatoid arthritis: results from 394 patients in the Oslo County Rheumatoid Arthritis register. Arthritis Rheum 2000;43(3):522-30.

Disclosure of Interest None Declared