Immunohistochemical in situ characterization of orthopedic implants on polymethyl metacrylate embedded cutting and grinding sections.

ABSTRACT

When investigating the tissue reaction on orthopedic implants, the cellular activity at the bone-implant interface is of special interest. Preparation of undecalcified bone sections with methylmetacrylate (MMA)-based resins allows evaluation of the host tissue reactions with the implant in situ. However, the technical workup is demanding and few reports exist on the immunohistochemical characterization of these sections. Rat (R), sheep (S), and human (H) samples were investigated. R specimens contained intramedullary rods in the rat tibia. S specimens were sheep tibiae with an external fixator. H specimens were obtained from deceased patients. Specimens were embedded in MMA-based Technovit 9100N using cold polymerization. Sections of 10-15 microm thickness were obtained and prepared for immunohistochemical staining. Good morphological detail was preserved in all specimens providing information about mineralization, recent bone formation, and bone-implant contact. The following antibodies could reproducibly be detected specifically Osteopontin (R, S, H), Osteonectin, Cathepsin D (R, S), von Willebrand factor (R, H), Osteocalcin, ED 1 (R), CD 3, CD 68, Keratin (H). Control procedures without adding primary antibodies showed no unspecific staining. Reliable detection of immunohistochemical markers of bone resorption, bone formation, inflammation, and angiogenesis at undecalcified sections with the implant in situ appears promising in enhancing our understanding of the cellular activity and cell-matrix interactions at the bone-implant interface.