MORPHOMETRIC STUDIES ON SYNOVIUM IN ADVANCED OSTEOARTHRITIS - IS THERE AN ASSOCIATION BETWEEN APATITE-LIKE MATERIAL AND COLLAGEN DEPOSITS

Objective. To look for the frequency and the influence of apatite-like deposits in the synovial membrane of advanced osteoarthritic joints. Methods. Synovium of 16 joints undergoing total arthroplasty for advan ced primary osteoarthritis was embedded in paraffin. Adjacent sections were stained with alizarin red S, Mowat's pentachrome, Hematoxylin-eo sin and Gomori to show apatite-like deposits, collagen, cartilage frag ments, vessels, cells and iron respectively. Histomorphometry was carr ied out for the apatite-like and collagen deposits by the point counti ng method; the density of vessels and cells was also quantified. Resul ts. 14 out of the 16 specimens contained apatite-like material, mostly on the synovial surface or just beneath. There was no correlation bet ween the apatite-like deposits and any other measured histological par ameter (fibrosis, villus length, synovial lining cell width, density o f synovial vessels or cells). Interestingly, the p value for a correla tion between the amounts of apatite and collagen deposits was close to significance (r = 0.53; p = 0.055) when the relative volume of the ap atite-like material was less than 1.2% (n = 13). Conclusions. Apatite- like deposits are frequently observed in the synovium of late stage os teoarthritis. Although not statistically significant these results sug gest a possible association between apatite-like and collagen deposits when the amount of apatite deposits is low. Further quantitative stud ies are recommended to investigate this observation.