We believe that there is a need for a systematic method of rating the evidence to support the effectiveness of an osteobiologic. However, this is not always true as the sheep interbody fusion model results in a very high fusion rate even when osteobiologics with relatively little osteoinductivity are used. In general, the larger the animal the higher is the required concentration of BMP-2. 15, 16 An example is BMP-2 and the concentration required to achieve fusion in different species along with the length of time. Within in vivo animal models, there is a hierarchy of spine fusion models determined by the species and the time to fusion. 9 - 14 In evaluating the strength of evidence that an osteobiologic has any of the 3 main characteristics, in particular, osteogenic and osteoinductive activity, it is important to have a hierarchy of in vivo over in vitro data. Other materials may have cellular components and may even be marketed as products containing “stem cells” however, the scientific data that the “stem cells” actually have any effect on fusion is limited to a few peer-reviewed studies with small sample sizes and often without a comparator. Other materials such as DBM may have actual osteoinductive molecules, but DBMs vary in osteoinductive activity between brands and from lot to lot within brands. Some materials without any osteoinductive properties are tested as bone void filler and brought to market with that minimal level of data. In fact, many products that are marketed are only supported by minimal evidence. Currently, the level of evidence that supports the use of different osteobiologics varies greatly. Given the very limited evidence of most osteobiologics, it is hard to predict effectiveness of the osteobiologics and how it affects patient outcomes.Ī systematic method of judging the effectiveness of osteobiologics does not exist.

The choice of the osteobiologic product can greatly affect the cost and outcome of surgery. Furthermore, the vast majority of the currently available osteobiologics products, have little or, in some cases, no clinical evidence for efficacy. 5 - 8 In addition, the majority of studies are often rated level III evidence or below. Several systematic reviews developed by AOSpine Knowledge Forum Degenerative reported low level of evidence primarily due to the high risk of bias, small sample size, lack of control groups, and limited patient-reported outcomes. Although those materials have been used in the past 2 decades, the literature on their effectiveness is inconclusive. The spine biologics domain expanded from being primarily iliac bone autograft to demineralized bone materials (DBMs), bone morphogenetic protein-2 (BMP-2), synthetics, and bone marrow aspirates. Non-autograft osteobiologics can be further divided into bone graft extenders (reducing the amount of autologous bone needed while achieving similar fusion rates), enhancers (combined with autologous bone to enhance the fusion), and substitutes (have same efficacy or better than autograft). Osteobiologics can have varying degrees of autograft, allograft, or synthetic components. Osteogenic property refers to the presence of cells that are crucial steps of bone formation and remodeling such as mature osteoblast and stem cells.

Osteoinductive property refers to growth factors within the graft that recruit cells into the matrix and drive cell differentiation into bone forming lineage.

This osteoinductive matrix provides a porous environment for ingrowth of blood vessels and a surface friendly for cell growth and differentiation into bone lineage. Osteoconductive property of bone graft refers to the 3-dimensional matrix that forms a scaffold for the eventual formation of bone. 1 - 4 The ideal bone graft has osteoconductive, osteoinductive, and osteogenic properties. The use of osteobiologics for spine fusion has increased significantly over the years with the expansion of available graft materials as well as the incidence of patients with spine pathologies.

Vallum spine