Extraction of calcium containing crystals from synovial fluids and articular cartilage.

A protocol for extracting minerals from biological tissues and fluids has been developed. Synovial fluid (SF) and articular cartilage samples were treated with papain and sodium hypochlorite to extract and concentrate calcium containing crystals. The method was validated by testing the ability to reextract synthetic calcium pyrophosphate dihydrate and calcium hydroxyapatite crystals added to SF in an unchanged form. The extracted crystals were analyzed by infrared spectroscopy and X-ray powder diffraction. The concentration of both calcium pyrophosphate dihydrate and hydroxyapatite crystals in SF was found to be higher than published figures.