Potassium permanganate induced calcergy: a model to study the effects of drugs on hydroxyapatite crystal deposition.

Hydroxyapatite crystal deposition is thought to play a role in the inflammatory episodes of osteoarthritis. A plaque of hydroxyapatite crystals was produced by local subcutaneous injection of a potassium permanganate solution. Transmission electron microscopy with X-ray energy spectroscopy was used to identify the crystal deposits as hydroxyapatite. The effects of dexamethasone, indomethacin, ethane 1-hydroxy-1, 1-diphosphonate (EHDP) and dichloromethylene diposphonate (Cl2MDP) on the development of the apatite plaque was studied. EHDP strongly inhibited the apatite deposition. Cl2MDP slowed the natural resorption of the apatite plaque. Dexamethasone and indomethacin failed to affect the crystal deposition process. The results suggest that EHDP could inhibit crystal deposition in the osteoarthritic joint and that Cl2MDP might have a role in slowing apatite crystal shedding from osteoarthritic cartilage and so reduce the synovitis seen in Osteoarthritis.