Clearance of 85Sr-labeled calcium phosphate crystals from rabbit joints.

The clearance of basic calcium phosphate crystals from rabbit joints was studied using synthetic crystals with characteristics similar to natural joint fluid mineral phase. Addition of strontium 85 during synthesis resulted in uniform trace-labeling. Crystals were rapidly taken up by synovial lining cells after intrasynovial injection. The time for clearance of one-half of the injected basic calcium phosphate crystal mass was 6.7 days, approximately 3 times faster than found previously for the much larger calcium pyrophosphate dihydrate crystals.