Measurement of periarticular bone mineral density in the hands of patients with early inflammatory arthritis using dual energy x-ray absorptiometry

Hand bone densitometry is more sensitive than standard radiology in the measurement of disease-related bone damage in early arthritis. Most studies employing dual energy x-ray absorptiometry (DXA) have evaluated the whole hand. The aim of this study was to evaluate a method that quantified bone density in regions of interest that were confined to the juxta-articular areas of metacarpo-phalangeal (MCP) and proximal interphalangeal (PIP) joints. Patients with inflammatory arthritis affecting the hands were selected for study. Postero-anterior (PA) scans of selected juxta-articular sub-regions were acquired using a Hologic 4500 Elite bone densitometer and forearm software. Each hand was scanned three times in immediate succession with repositioning between scans. The six selected sub-regions included the periarticular regions of the second, third, and fourth MCP and PIP joints. Sub-regions of different dimensions (4 and 5 mm proximal and distal to the joint space) were assessed at each joint. Coefficients of variation (CV) were calculated for bone mineral density (BMD) and bone mineral content (BMC) of each selected sub-region. Eighty four individual hand joints in seven patients were evaluated three times. Precision values ranged between 0.89% and 2.37% for BMD and between 1.38 and 3.26 for BMC measurements. BMD measurements of MCP joints were more precise than PIP joints. BMD measurements of 10-mm sub-regions were more precise than 8-mm sub-regions. The precision value for the net average BMD measurement of the six sub-regions evaluated was 0.78% for 8-mm sub-regions and 0.73% for 10-mm sub-regions. Net average BMC measurements had CV values of 1.11% and 1.08%, respectively. DXA can be used to reliably measure periarticular BMD and BMC of small joints in the hands in patients with early inflammatory arthritis. Precision values for quantifying juxta-articular bone approximated BMD measurements of the spine.