Treatment of bone defects and non-unions frequently requires the
transplantation of autologous bone. As an alternative, different kinds of
bone substitutes have been used more often during the past years. These
bone substitutes include synthetic materials, just as well as processed materials from human donors (allogen) or animals (xenogen). The relatively low hurdles in the approval process, compared to
pharmaceutical drugs, have led to an almost unmanageable amount of different kinds of
bone substitutes. Due to sparse clinical studies, evidence-based decisions for a specific product or a specific indication are hardly possible. Therefore, a deeper knowledge about basic properties of different
bone substitutes is needed for a rational clinical decision. The present review aims to clarify the sometimes confusing nomenclature of
bone substitutes and discuss their different
biological properties. Generally,
bone substitutes can be discriminated in osteogenic, osteoinductive and osteoconductive materials. The great majority of
bone substitutes and especially synthetic materials serve as a matrix for bone growth and therefore possess mainly osteoconductive properties. The combination of these osteoconductive materials with osteogenic cells or osteoinductive
growth factors, leads to composite materials with higher bone forming potential. Clinically, the quality and vitality of the recipient bone defect is of great importance. As a prerequisite for successful
transplantation of
bone substitutes or autologous bone, the recipient bone defect should be mechanically stable, free of
infection with vital bone ends and intact soft tissue coverage. Bone defects in the spine, methaphyseal defects after
trauma/tumour and diaphyseal segmental defects are typical indications for the application of
bone substitutes. Unfortunately, the current literature does not allow concrete recommendations for specific
bone substitutes or specific clinical indications. However, this review aims to discuss clinical benefits and limitations of
bone substitutes for frequent indications to help clinicians in their decision making process.