Assessment of subchondral bone mineral density in equine metacarpophalangeal and stifle joints.

摘要

Functional relationships between articular cartilage and underlying subchondral bone have been shown to be associated with the progression of osteoarthritis (OA). However, quantifiable factors substantiating this relationship do not exist. Therefore, the study objective involved quantifying subchondral bone mineral density (BMD) of the equine metacarpophalangeal (MCP) and stifle joints as a step in determining if regional subchondral BMD may be associated with OA changes. BMD was bilaterally quantified using dual energy xray absorptiometry (DEXA) for four subchondral regions: palmer and dorsal aspect of the medial 3rd metacarpal (MC3P, MC3D), medial femoral condyle (MFC), and the medial trochlear ridge (MTR). BMD (g/cm2) was measured using a 5.2 x 5.2 mm region of interest in the subchondral bone area. To account for the differences in thickness, BMD (g/cm2) was divided by sample thickness providing volumetric BMD (g/cm3). No significant effect of side on BMD values was found (p > 0.72). However, there were significant differences in BMD found between all regions (p < 0.05). The volumetric BMD of the MC3P region was significantly greater than the MC3D and the MC3D was greater than the MFC, while the MFC was greater than the MTR (MC3P > MC3D > MFC > MTR). The MCP regions had a higher volumetric BMD than the stifle regions possibly due to higher weight distribution, smaller articular surface area, and joint geometry. The adaptive bone structural variations between the regions studied were shown to be significant. Mechanical properties of the overlying cartilage are currently being analyzed to correlate with these results and provide a possible diagnostic method to investigate OA progression.