INORGANIC BONE SUBSTITUTES

Abstract

These studies are indicative of the potential utility of resorbable and nonresorbable inorganic materials as bone graft substitutes. Bone transplants and bone substitute materials are necessary in +/−10% of all skeletal reconstructive operations. The higher osteogenic potential of autografts compared to allogenic transplants is undisputed, but restricted by limited availability and necessity of secondary operations.

Commercial bone graft materials show variety of compositions and properties, many very different from those of autologous bone. Physicochemical properties of these materials were compared using x-ray diffraction, scanning and transmission electron microscopy. Biological reactivity of different materials was also compared in histological evaluations in animal models. Experimental and clinical studies have been encouraging, especially in metaphyseal defects.

Bone substituting the artificial material should be able to bear weight and, if possible, be lamellar bone. Since fundamental examinations of osteoinduction and affiliated isolation of growth factors (Urist 1965), extensive scientific research on growth factors contained in bone matrix has been performed. Proteins of the TGF-β family play a key role in regulation of bone regeneration. In past years, alkaline fibroblast growth factor has raised increased interest among researchers. Its presence implies that it plays an important role in the development of bone substance. One best known effect is significant augmentation of microangiogenesis, which could be demonstrated among others in experimental wound healing investigations. Further experimental examinations showed significant increase of callus formation in rats and miniature pigs, in which FGF had been injected into the fracture site.

Current bone substitute materials are only to be used in clearly defined indications, as they do not currently meet the biological or mechanical properties of autogenous bone. Our knowledge is grounded on various experimental models, which are not always comparable. Therefore many aspects have to be considered as a working understanding.