Changes in the extracellular matrix on the surface of sintered bovine bone implanted in the femur of a rabbit: An immunohistochemical study

Abstract:

The interface of implanted True Bone Ceramics (TBC; sintered bovine bone; Koken, Tokyo, Japan) was examined. In the primary experiment, TBC was implanted into the bone marrow of a rabbit's femur. The extracellular matrices (types I, II, and III collagens and fibronectin) of decalcified specimens collected 1–48 weeks postoperatively were immunohistochemically examined. Undecalcified sections collected 6 weeks postoperatively were used for line analyses of calcium and phosphorus, by a scanning electron microscope-electron probe microanalysis (SEM-EPMA) method. In a secondary experiment, TBC was implanted into an osteochondral defect of a femoral condyle, harvested 1–12 weeks postoperatively, and decalcified to examine the extracellular matrices at the interface. In the bone marrow in the early phase, TBC had absorbed quantities of fibronectin. Immature bone (containing both types I and III collagens) in direct apposition to the ceramic surface had matured (containing type I collagen alone) in the TBC pores. SEM-EPMA revealed the continuity of high levels of calcium and phosphorus at the TBC-bone interface. In the secondary experiment, enchondral ossification or fibrous tissue formation was observed near the articular surface. However, in the subchondral layer, direct bone formation was observed in the TBC pores. It was concluded that TBC has excellent bioactivity for inducing maturation of new bone matrix on porous surfaces.