Biologics in Hand Surgery

Bone Grafts and Substitutes

Complex fractures, nonunions, or tumor resections can leave bone defects. Autologous bone grafts are effective fillers, carrying both osteoinductive and osteoconductive properties. However, autografts require harvesting, which lead to increased operative time as well as donor site morbidities. The amount of autograft available may not be sufficient. Therefore, there is a demand for bone graft substitutes that can be readily applied.

Allografts

Bone allografts are widely used in hand surgery. Bones harvested from cadavers are typically freeze-dried and sometimes undergo further processing such as ethylene oxide treatment or γ-radiation for further sterilization. Allografts can also be prepared fresh or frozen, but such preparations are rarely used in hand surgery. While the osteoblasts and precursors are lost during the freeze-drying, allografts still provide favorable osteoconductive properties.

Allografts can come in several different forms such as cortical, cancellous, and corticocancellous. Cortical allografts are incorporated by creeping substitution with intramembranous ossification, while cancellous allografts are incorporated by enchondral ossification.

Demineralized bone matrix (DBM) is allograft that has been decalcified, leaving organic matrix behind. The trabecular network of collagen serves as a scaffold for bone formation. The growth factors and bone morphogenic proteins (BMPs) are maintained and can help induce cells to form bone. DBM does not provide mechanical strength. However, its soft consistency allows it to be placed into small defects or even be injected percutaneously.