It is important to understand several common definitions used in bone repair:
|means that the bone substitute acts as a scaffold for new bone formation.|
|means that the material acts to induce the pleuripotential cells to change into osteoblasts.|
|refers to the formation of bone.|
The orthopaedic surgeon must first assess the clinical situation that requires bone grafting and determine if there is an osteogenic signal, if there are responding cells, if there is a matrix required to act as a scaffold, and if a vascular supply exists.
To decide on a type of graft to be used, you need to look at the amount of bone loss, the biomechanical requirements, the host biological potential, and the bioactive factors that can be provided. In the past, the surgeon could either use autogenous bone graft or allograft bone, which acts like a scaffold. The allograft was either frozen or freeze dried bone chips.
However, the newest advancement is to use bone graft (extenders) or substitutes for traditional bone graft material. In most trauma cases, autogenous bone graft is still the gold standard of treatment to fill defects.
AVAILABLE TYPES OF BONE GRAFT
|Demineralized Bone Matrix (DBM)|
|This is produced by acid extraction of bone, and has a variable amount of bone morphogenic protein (BMP). DBM is available as a gel, paste, putty, or powder, with no intrinsic strength, and is used as an adjunct for spinal fusion procedures. The commercial products are ZETH (KYERON), AlloMatrix (Wright Medical Technology), or Grafton P (Osteotech). DBM is used clinically in revision hip and knee surgery together with cancellous bone chips to fill contained defects.|
|These synthetics are derived from synthetic or marine coral that is porous. These osteoconductive products are hydroxyapatite, tricalcium phosphate, and calcium phosphate, commercial available as ELIZ (KYERON) , Endobon (Biomet), OSIQ (KYERON), Norian SRS (Synthes) and AXOZ (KYERON). These materials are brittle, have variable resorption, and are often used for the augmentation of fracture repair. OSIQ, Norian SRS and AXOZ are injectables.|
The commercial products REOS (KYERON) and CopiOs (Zimmer) have the ceramics mixed with a collagen to make to product also osteoinductive and less brittle.
|Autologous Platelet Concentrates (APC)|
|This product is harvested from blood and has multiple growth factors that may be combined with a matrix to enhance bone formation. BMAC system (KYERON) can be used here, which is multi-biologic concentrate centrifuge.|
|Bone Marrow Cells|
|These cells are osteoinductive because of the mesenchymal cells that are present; they should be combined with matrix to stimulate bone formation. There is some interest in combining bone marrow cells with ceramics (ELIZ) , cancellous bone chips (ZETH) or a collagen-ceramic composite (REOS) to fill contained defects in hip and knee revision arthroplasty. The BMAC system, a multi-biologic concentrate centrifuge, can be well used to concentrate regenerative cells in a point-of-care procedure within 15 minutes.|
|Bone Morphogenic Protein (BMP)|
|BMP, which has been available for many years, is osteoconductive. BMP can cause bone formation in nonunions and in spinal fusions. The main issue associated with the use of BMP is to find a suitable carrier that will fill the void, be nonreactive, be biodegradable, and have some biomechanical properties. The other issue at the present time is the cost of BMP, which is about $3000 per level of spinal fusion. In the treatment of tibial nonunions, there has been shown to be no difference with BMP compared with autograft.|