Biological Approaches to Spinal Instrumentation and Fusion in Spinal Deformity Surgery

The use of autografts, allografts, and synthetic materials as bone substitutes in spinal surgery continues to increase as the population ages. Each of these materials has advantages and disadvantages. Autografts have previously been considered the gold standard for their excellent graft incorporation without the risk of rejection or disease transmission. However, their drawback is limited supply and the potential for donorsite morbidity. Allografts are an acceptable alternative because of the relative abundance, availability of desired sizes and shapes, and elimination of procurement-related morbidities. Advances in processing techniques and strict guidelines for allograft donor screening have reduced the risk of disease transmission. However, some manufacturing and sterilization processes can compromise the mechanical strength and biological properties of the allograft. Moreover, allografts may still, albeit rarely, elicit an inflammatory response, be rejected, or transmit disease. Synthetic materials are an emerging and increasingly popular option. However, their ability to incorporate into the host tissue remains uncertain. In addition, the host immune responses are not well elucidated. The biological approaches to spinal instrumentation and fusion must be tailored to meet the specific needs of each clinical scenario.