Abstract
The use of biologics will grow in the future in terms of bone healing, spine fusion, and disc regeneration. In addition, osteogenic material will always be needed for spinal fusion. The future will be a combination of improvements in bone graft materials that are safe, have no donor morbidity, and have an unlimited supply. This talk will discuss current and future options for bone healing. Bone grafts and bone graft substitutes are generally classified into one or more of the following groups: osteogenic, osteoinductive, osteoconductive, and structural. Structural grafts, such as a tricortical iliac crest graft or femoral ring allograft, provide mechanical support to the construct. Osteoconductive grafts provide a scaffold for bone formation. Osteoinductive grafts are able to induce osteoblastic differentiation of the progenitor cells. Osteogenic grafts are able to directly contribute cells for bone formation. Autograft has long been considered the gold standard as it has all of the above properties. However, limited supply of autograft, as well as the morbidity associated with its harvest, has led to the development of a plethora of bone graft substitutes and extenders which may contain one or more of the above properties. Allografts obtained from cadavers provide an osteoconductive scaffold, and are weakly osteoinductive. These grafts do not have any osteogenic potential, as all the cells are killed during the processing aimed to decrease the risk of infection transmission and antigenicity. Still, a minute risk of viral transmission, such as hepatitis, cytomegalovirus, and human immunodeficiency virus, still exists. Allografts may also undergo further processing such a demineralization, leading to demineralized bone matrix (DBM). DBM lacks the structural support of strut allografts, but still has osteoconductive and osteoinductive properties. Demineralized bone matrix (DBM) is a bone graft substitute with primarily osteoconductive and some osteoinductive properties. It is formed by acid extraction of allograft bone, resulting in the loss of mineralized component of bone while retaining the type 1 collagen framework and many growth factors. The osteoinductive quality of DBM varies among different products due to the variability in their content of the bone morphogenic proteins (BMPs). It is currently available in multiple forms, including putty, injectable gel, and flex strips. Ceramics are an attractive type of bone graft extenders and substitutes for several reasons. They can be manufactured in large quantities and a variety of shapes and sizes, do not carry a risk of disease transmission, are biodegradable, and are easy to sterilize. On the other hand, they only provide an osteoconductive scaffold, have little shear strength, and are brittle. As such, they cannot be used as structural grafts without the protection of rigid instrumentation. Commercially available forms of ceramics include calcium carbonate and β-tricalcium phosphate.