A quantitative study of articular repair in the guinea pig

This study examined the healing of articular defects, with and without carbon fiber implants, and the response of repair tissue to its interim removal in guinea pigs of different ages. These were investigated after the induction of full thickness articular cartilage defects in the patellar groove of skeletally mature and immature guinea pigs. To indicate its capacity for replacement after attrition, repair tissue occurring in untreated (control) and carbon fiber treated (experimental) defects was ablated after 8 weeks, and the animals were sacrificed after an additional 8 weeks. The repair tissue was studied quantitatively at gross and microscopic levels and qualitatively using scanning and transmission electron microscopic study. The principal findings were as follows. The initial formation of repair tissue was variable, but it occurred in most cases. Secondary repair tissue formation consistently occurred after excision. Age did not influence the degree of repair. Carbon fiber implants of the type used impaired healing of small full thickness articular cartilage defects, compared with no treatment. Microscopically, repair tissue contains five main cell types, each with a characteristic surrounding matrix. Intermediate forms also are found. These, together with four of the five main types comprise a morphologic continuum and fit readily into a proposed developmental sequence that may stem from the fibroblast.