Increased metacarpal bone mass following 18 months of slow-acting antirheumatic drugs for rheumatoid arthritis.

Osteoporosis in RA is mediated by numerous inflammatory substances. This study was undertaken to see if SAARD could modify the rate of metacarpal bone loss in RA. Combined cortical thickness (CCT) measured at the midshaft of the right second metacarpal was used to calculate bone mass (CA%) using a digitizer. Eighty-one subjects were studied, all of whom had at least three sets of hand X-rays, the last of which was approximately 18 months following initiation of SAARD therapy. There were 12 males and 69 females. The mean age at time of starting therapy was 51 (SD 12) years while the mean duration of disease at the time was 7.6 (SD 8) years. The mean time to referral for SAARD from the general clinic was 2.5 (SD 3) years. The percentage fall in bone mass prior to therapy was 2.51%/day compared to a gain of 0.6%/day after therapy (P less than 0.05). Forty-nine patients were aged over 50 years while 32 were 50 years or younger at the time of study. Comparison showed that in the pretreatment period, the rate of change in CCT and CA% was not significantly dependent age (P less than 0.1). During that therapy, the rate of change in CCT and CA% significantly different in the two age groups. Patients aged over 50 years continued to lose bone, but at a slower rate (P less than 0.05). Patients aged 50 years or less either stopped losing or gained metacarpal bone mass during the study period (P less than 0.005). The time to referral for SAARD and disease duration (comparable in the two age groups) did not have a significant effect on changes in CA% during therapy. Change in bone mass could be predicted by change in disease activity. We conclude that SAARD have a significant sparing effect on metacarpal osteoporosis in RA. This positive effect is masked by the overwhelming influence of age (and menopause) and could be missed. Metacarpal osteoporosis seems a pathophysiologically more useful measure of radiological change in RA than erosions or joint space narrowing.