The bone-metal interface following hip nailing.

In order to establish a base line for tissue reaction in relationship to loaded implanted foreign materials that might be used for comparison with new materials, the interface between the trabecular bone in the femoral head and hip nails has been studied in 20 specimens. The interface consists of four distinguishable layers: a cellular layer at the surface, a layer of fibrovascular connective tissue, a layer of collagenous connective tissue and/or fibrocartilage, and a peri-implant bone plate. Even 10 years after insertion of the nail this interface remained cellularly active, the activity presumably being related to the different modulus of elasticity between the metal and the surrounding trabecular bone.