Effect of Rheumatoid Arthritis on Volumetric Bone Mineral Density and Bone Geometry, Assessed by Peripheral Quantitative Computed Tomography in Postmenopausal Women Treated with Bisphosphonates

Objective. To investigate the effect of rheumatoid arthritis (RA) on volumetric bone mineral density (vBMD) and bone geometry in postmenopausal women treated with bisphosphonates. Methods. Fifty-three postmenopausal women with RA and 87 control subjects, comparable in terms of age, body mass index, and years since menopause, underwent peripheral quantitative computed tomography (pQCT) of the nondominant tibia. Results. At 4% (trabecular site), trabecular bone mineral content (BMC) and vBMD (p < 0.001) were lower in the RA group, while trabecular area was comparable. At 38% (cortical site), cortical BMC (p < 0.01), area (p < 0.05), and thickness (p < 0.001) were lower in the RA group, whereas vBMD was comparable. Endosteal circumference was higher (p < 0.05), whereas periosteal circumference was comparable, indicating cancellization of cortical bone. In the RA group, muscle area was lower (p < 0.001), while at 14% polar stress strength index was significantly lower (p < 0.01) in patients with RA, indicating impairment of bone mechanical properties. Conclusion. RA is associated with negative effects on both cortical and cancellous bone in postmenopausal women treated with bisphosphonates. Cortical geometric properties are also adversely affected mainly by increased endosteal circumference, whereas trabecular geometric properties are generally preserved. (First Release April 1 2012; J Rheumatol 2012;39:1215-20; doi:10.3899/jrheum.110579)