MAGNESIUM WHITLOCKITE DEPOSITION IN ARTICULAR-CARTILAGE - A STUDY OF 80 SPECIMENS FROM 70 PATIENTS

Objective-To examine articular cartilage from a number of joint sites, using a large sample group, for the presence of magnesium whitlockite crystal deposition. Methods-Articular cartilage specimens were taken from a total of 70 patients. The majority of specimens were taken from femoral heads, with smaller numbers from femoral condyle, tibial plat eau, radius, ulna, and several small peripheral joints. Normal and ost eoarthritic articular cartilage specimens were obtained from patients undergoing prosthesis replacement or amputation. Specimens were resin embedded and examined using transmission electron microscopy and x ray microanalysis. Results-Magnesium whitlockite crystals were identified , on the basis of morphology, size and elemental composition, in artic ular cartilage from all sites sampled. The distribution of crystals wa s similar in all samples (restricted to the superficial zone), althoug h the density of deposition was extremely variable, with the greatest density observed in femoral head specimens. No magnesium whitlockite c rystals were observed in osteophytic or epiphysial cartilage. Conclusi ons-This study demonstrated the widespread extent of magnesium whitloc kite deposition in human articular cartilage, albeit at much lower den sity than previously reported in femoral head articular cartilage. In consideration of possible roles for these crystals in articular cartil age, it is concluded that an opportunistic mode of formation, possibly influenced by mechanical stresses, would be most plausible.