The osteogenic properties of the interface membrane at the site of orthopedic implants: The impact of underlying joint disease

Osseointegration at the site of orthopedic implants is dependent on the rec ruitment, attachment, and differentiation of osteogenic cells. Data concern ing the effect of a patient's underlying joint disease on the modulation of the cellular activity and the long-term survival of joint prostheses is li mited. In this study, immunocytochemistry was used to investigate the osteo genic cell phenotype within the bone-implant interface fibrous membrane in 60 patients with different underlying joint disease. Tissue specimens were removed during revision operations performed at variable times following im plantation. The results provided histological evidence of the presence of f ibrocartilage tissue and calcified bone within the interface. TGF-P, metall oproteinases (MMP1 and MMP2) and their inhibitors (TIMP1 and TIMP2) were im munolocalized within fibroblasts, chondrocytes, and osteoblasts throughout the interface, indicating that signals modulating the osteogenic cell pheno type at these sites are highly regulated. Finally, the study identified a s ignificant difference in the histological changes elicited by implant parti culate debris in patients of different diagnostic categories. Such observat ions imply that the activity of the original joint disorder could augment s pecific cellular activation/immune signals that subsequently affect the deg ree of the local inflammatory responses to implant wear particles. The nega tive balance between the rate of bane growth and resorption around the pros thetic joint is central to the pathogenesis of aseptic loosening of implant s.