Biomechanics of integrative cartilage repair

Cartilage repair is required in a number of orthopaedic conditions and rheu matic diseases. From a macroscopic viewpoint, the complete repair of an art icular cartilage defect requires integration of opposing cartilage surfaces or the integration of repair tissue with the surrounding host cartilage. H owever, integrative cartilage repair does not occur readily or predictably in vivo. Consideration of the 'integrative cartilage repair process', at le ast in the relatively early stages, as the formation of a adhesive suggests several biomechanical approaches for characterizing the properties of the repair tissue. Both strength of materials and fracture mechanics approaches for characterizing adhesives have recently been applied to the study of in tegrative cartilage repair. Experimental configurations, such as the single -lap adhesive test, have been adapted to determine the strength of the biol ogical repair that occurs between sections of bovine cartilage during expla nt culture, as well as the strength of adhesive materials that are applied to opposing cartilage surfaces. A variety of fracture mechanics test proced ures, such as the (modified) single edge notch, 'T' peel, dynamic shear, an d trouser tear tests, have been used to assess Mode I, II, and III fracture toughness values of normal articular cartilage and, in some cases, cartila ginous tissue undergoing integrative repair. The relationships between adhe sive biomechanical properties and underlying cellular and molecular process es during integrative cartilage repair remain to be elucidated. The determi nation of such relationships may allow the design of tissue engineering pro cedures to stimulate integrative cartilage repair.