الفهرس 
• Types of bone substitutesOnly 14 pages are availabe for public view
 |  | from | 127 |  |  |
| | | from | 127 | | |
Abstract
Previously, the goals for bone-graft substitutes were to match fusion rates with autologous bone-grafting techniques while avoiding the morbidity of bone-graft harvest and extending the quantity of available graft material. As bone-graft substitutes and growth factors become clinical realities, new standards will be defined.
Thus, various bone graft substitutes have been developed to promote spinal fusion. These graft materials all possess distinct cellular, biochemical and structural properties that determine their specific clinical indications.
A large number of bone-graft alternatives are currently commercially available for orthopaedic use. They vary in composition, mechanism of action, and special characteristics.
Selection of proper bone-graft substrate is essential to achieve successful fusion. The ideal bone graft is characterized by its osteoconductive and osteoinductive capabilities, freedom from disease, minimal antigenic factors, and structural support.
Osteoconductive materials, such as allograft, collagen, calcium or ceramic preparations are one such class of potential bone graft alternatives, but generally they lack osteoinductive properties. Recent attention has focused on osteoinductive materials such as demineralised bone matrix, recombinant bone morphogenetic proteins and bone marrow aspirates or blood product concentrates. These products may be combined with osteoconductive carriers and are clearly finding a place in the clinical arena.
Unlike autograft, which is still considered to be the gold standard, because it contributes osteogenic cells, osteoinductive factors and an osteoconductive matrix, none of these other alternative methods provide all three components required for bone regeneration. For this reason, it may be more efficacious to use several techniques concomitantly to construct a composite graft that exhibits an even greater capacity to enhance arthrodesis of the spinal column.
So, an ideal bone-generating combination is now the goal. It will integrate an osteoconductive matrix with growth factors delivered in a localized environment and, over the appropriate time course, attract and sustain osteoprogenitor cells as they differentiate into osteogenic cells.
The use of bone substitute as a graft extender has become an acceptable practice especially in fusions spanning multiple segments. Beside using some types of bone substitutes as carrier for osteoinductive proteins.
The outcome of spinal fusions depends on a complex process influenced primarily by the type of graft material used and on the many local and systemic factors that affect the arthrodesis healing response (e.g., soft tissue bed, graft site preparation, mechanical stability).