AN INVESTIGATION OF THE STRESS-DISTRIBUTION GENERATED IN ARTICULAR-CARTILAGE BY CRYSTAL AGGREGATES OF VARYING MATERIAL PROPERTIES

Several joint diseases are associated with the deposition of crystals within the articular cartilage. A variety of crystal aggregates have p reviously been identified throughout the thickness of the cartilage. A linen, elastic finite element model representing instantaneous, or sh ort-term, loading conditions has been developed of a large crystal agg regate surrounded by articular cartilage The material properties of th e aggregate and the cartilage were varied and the resultant shear stre ss and equivalent strain distribution in the surrounding cartilage stu died in order to provide some Indication of the relative potential of various types of crystal aggregate to cause damage to tile articular c artilage. Results indicated that aggregrates with a Young's modulus ei ther much bs, or much greater, than that of the surrounding cartilage generated the maximum shear stress and equivalent strain concentration s at the interface between the aggregate and the cartilage. Also, that highly compressible aggregates, with a very low Poisson's ratio, gene rated higher shear stress and equivalent strain concentrations in the surrounding cartilage than aggregates of a more incompressible nature. Under conditions of short-term loading these results suggest that cry stal aggregates present within the cartilage layer will increase the s hear stress and equivalent strain concentrations in the surrounding ca rtilage, and therefore have the potential to cause damage to the carti lage. (C) 1997 Elsevier Science Ltd for IPEM.