Background Periarticular osteoporosis is one of the earliest radiographic signs of bone damage in RA (rheumatoid arthritis). Recent dual-energy x-ray absorptiometry (DXA) investigation has shown decreases in bone mineral density (BMD) in RA with only a few weeks of disease duration . Periarticular BMD around the wrist joint is crucial in determining the associations between periarticular osteoporosis and joint destruction or functional impairment [2,3]. However, specific regions of interest (ROIs) for the correlation, predicting clinical variables of hand bone loss and its relationship to disease duration, remain largely unexplored.
The aim was to investigate the relationship between periarticular osteoporosis in the distal forearm and clinical variables or disease duration.
Objectives Periarticular BMD measurement of the forearm in RA patients is not used for routine assessment. This study was conducted to investigate 1) the difference between various periarticular ROIs of BMD of the forearm, 2) the correlation between periarticular forearm BMD and joint destruction and physical function, 3) the independent variables for predicting BMD of the forearm, and 4) the forearm BMD of different ROIs in the early stage of RA.
Methods We conducted a cross-sectional clinical study of a cohort with RA from a single institution. Measurements included BMD assessed by DXA of the distal forearm, joint destruction of the hands assessed by modified total Sharp score (mTSS), functional impairment assessed by a health assessment questionnaire (HAQ), and other clinical data. Variables affecting the forearm BMD values were analyzed by correlation and stepwise regression analyses.
Results Of the 405 patients enrolled in the present study, 324 (average age 62.5±13.2 years) were identified as women with definite RA with a complete set of data. BMD in the distal end of the forearm (BMDud) was significantly reduced compared with that in the distal third of the forearm (BMD1/3) (P <0.0001). In a stepwise regression analysis of the clinical and therapeutic variables examined, the duration of the disease in the BMDud and mTSS in BMD1/3 were independent predicting variables, while age and partial HAQ scores associated with the upper extremity were common independent variables (Table). BMDud was significantly less than BMD1/3, even in patients with a short duration of the disease.
Conclusions The results of the present study showed the presence of periarticular osteoporosis of the wrist joint, even in patients with a short duration of the disease. Periarticular BMD in the distal forearm is closely correlated with joint destruction and functional impairment in RA. Periarticular BMD in the distal forearm may be already reduced at the clinical onset of RA.
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Acknowledgements We thank Dr. Hiroyuki Yoshitomi, Kyoto University Graduate School of Medicine, for their valuable help. We also thank Wataru Yamamoto, Kurashiki Sweet Hospital, for his tremendous help on data management.
Disclosure of Interest None declared