Cortical thickness relative to the transverse diameter of third metacarpal bone reflects bone mineral density in patients with rheumatoid arthritis.

Abstract

Rheumatoid arthritis (RA) is accompanied by potential risk of bone mineral loss. In this study, we developed a screening index for the osteoporosis related level of bone mineral density loss for RA patients as a substitute to the dual-energy X-ray absorptiometry (DXA) method. X-ray pictures of both sides of the hand were taken in order to evaluate Sharp/van der Heijde Scores (SHSs). This score was calculated for RA patients at the first consultation and routinely thereafter. We measured cortical thickness and the transverse diameter of the mid-portion of the metacarpal bone of the right middle finger with the same radiograph. Cortical Thickness Ratio (CTR) was then calculated as cortical thickness relative to the transverse diameter. Bone mineral density (BMD) of the lumbar spine (LS) and femoral neck (FN) was measured at the same time. The relationship between BMD and CTR was evaluated using multivariate linear regression analysis. Clinical backgrounds and disease indices were also evaluated. The cut-off index (COI) of the CTR for osteoporosis criteria that represented with a T-score < -2.5 for both bones was calculated using the Receivers Operation Characteristics technique. In 300 subjects, the CTR demonstrated significant correlation with BMD in both bones (p < 0.01). The COI was determined to be 0.25 and the odds ratio was 4.19 and 4.90 for the LS and FN, respectively. Our findings indicated that the CTR correlated with BMD. This index may represent a promising screening tool for the judgment of osteoporosis in RA patients.