OBJECTIVE

To evaluate premenopausal women with longstanding rheumatoid arthritis (RA) for potential associations between parameters of localized bone involvement and parameters of systemic bone involvement in the affected joints.

METHODS

Eighty consecutively evaluated premenopausal women with RA were included in the study, along with 160 healthy female control subjects who were matched to the patients by age and body mass index. Volumetric bone mineral density (vBMD), bone microarchitecture, and finite elements of biomechanical bone strength (bone stiffness and estimated failure load) at the distal radius and distal tibia were analyzed by high-resolution peripheral quantitative computed tomography (HR-pQCT) in patients with RA compared to healthy controls. In addition, in patients with RA, localized bone involvement in the metacarpophalangeal and proximal interphalangeal joints was analyzed by HR-pQCT, to identify bone erosions and osteophytes.

RESULTS

Among the 80 premenopausal women with longstanding RA, the mean ± SD age was 39.4 ± 6.7 years and mean ± SD disease duration was 9.8 ± 5.3 years. Trabecular and cortical bone parameters and bone strength at the distal radius and distal tibia were all impaired in patients with RA compared to healthy controls (each P < 0.05). In total, 75% of RA patients had evidence of bone erosions, and 41.3% of RA patients had detectable osteophytes on HR-pQCT. RA patients with bone erosions, as compared to RA patients without bone erosions, had lower cortical vBMD (at the distal radius, mean ± SD 980 ± 72 mg HA/cm versus 1,021 ± 47 mg HA/cm [P = 0.03]; at the distal tibia, 979 ± 47 mg HA/cm versus 1,003 ± 34 mg HA/cm [P = 0.04]) and higher cortical bone porosity (at the distal radius, mean ± SD 2.8 ± 2.5% versus 1.8 ± 1.6% [P = 0.04]; at the distal tibia, 3.7 ± 1.6% versus 2.7 ± 1.6% [P = 0.01]). In patients with RA, osteophyte volume at the distal radius was positively correlated with trabecular vBMD (r = 0.392, P = 0.02), trabecular number (r = 0.381, P = 0.03), and trabecular stiffness (r = 0.411, P = 0.02), and negatively correlated with trabecular separation (r = -0.364, P = 0.04), as determined by Pearson's or Spearman's correlation test.

CONCLUSION

The findings show that premenopausal women with longstanding RA have systemic bone fragility at peripheral joint sites. Moreover, the presence of bone erosions is mainly associated with cortical bone fragility at the distal radius and tibia, and presence of osteophytes is associated with repair of trabecular bone at the distal radius.