Periosteal and endosteal reaction to reaming and nailing: the possible role of revascularization on the endosteal anchorage of cementless stems.

The reaction of bone to titanium implants of different shapes inserted in the rabbit tibia was investigated with histological and perfusion techniques to determine the pattern of vessel distribution. The experimental implants included full cylindrical rods, hollow rods with holes on the surface and wire mesh rods. In the implanted bones the rods were found to fill a large area of the medullary canal; however, owing to the discrepancy between the shape of the diaphysis and the implant, the endosteal contact was never complete. In an early phase, reactive bone filled the gap between the endosteal and the implant surface; in hollow and wire mesh rods bone had grown inside through the lateral holes or loops of the mesh. Revascularization took place together with remodelling of the endosteal, primary bone to mature lamellar. In full implants a reticle of newly formed vessels developed around the rods; in hollow and wire mesh implants vessels had grown inside the implant itself and the endosteal surface had a more regular profile than in full rods. Wire mesh plugs prevented formation of a peripheral medullary space and showed no encapsulation; wires in contact with or in proximity to the endosteal surface were incorporated by lamellar systems with strong connections with the original cortical bone.