Bone Mineral Density in Rheumatoid Arthritis Measured by the Gamma Transmission Method

Abstract

The study was performed in 55 RA patients and 47 controls. The ages of the RA patients were evenly distributed over the range 24-68 years. The average duration of the disease was less than 3 years. 100 mCi of ²⁴¹Am was used as radiation source. Bone mineral density (BMD) was expressed as g/cm³. The measuring sites were the mid-point of the third metacarpal bone, the radius 1.5 cm distal to the head and the radius 10 cm from the head. The values for each measuring site were calculated by dividing the bone index (g/cm) by the cross-sectional area of the bone. At the mid-radius and the distal radius the BMD was significantly lower in the RA patients than in the controls. The differences were 8% and 10% respectively. At the third metacarpal the difference (5%) was not significant. The osteoporotic effect of RA seemed to intensify with age. The duration of the disease was not correlated with BMD. Serial BMD measurements in RA cases of recent onset revealed no clear decrease in BMD. A significant correlation was found between BMD and the following factors: Systemic and local technetium index of joints, X-ray grade, ESR. Sex, functional capacity, grip strength, Waaler-Rose titre and serum alkaline phosphatase were not related to BMD. It is concluded that general osteoporosis in RA is usually slight and closely related to the inflammatory process.