Bone grafting is currently used in orthopaedic and maxillofacial surgery for the treatment of bridging diaphyseal defects, non-union, filling metaphyseal defects and mandibular reconstruction.
Autogenous Bone Grafts
Autogeneous bone graft is osteogenic (which forms bone, due to living cells such as osteocytes or osteoblasts), osteoconductive (have no capacity to induce or form bone but they provide an inert scaffold which osseous tissue can regenerate bone), osteoinductive (stimulate cells to undergo phenotypic conversion to osteoprogenitor cell types capable of formation of bone). There are no substitutes for autogenous bone; there are, however, synthetic alternatives.
Bone Allograft Materials
Allografts have been used as an alternative, but it has low or no osteogenicity, increased immunogenicity and resorbs more rapidly than autogenous bone. In clinical practice, fresh allografts are rarely used because of immune response and the risk of transmission of disease. The frozen and freeze-dried types are osteoconductive but are considered, at best, to be only weakly osteoinductive. Freeze drying diminishes the structural strength of the allograft and renders it unsuitable for use in situations in which structural support is required. Allograft bone is a useful material in patients who require bone grafting of a non-union but have inadequate autograft bone. Bulk allografts can be utilised for the treatment of segmental bone defects. Their use is well documented for reconstruction after resection of bone tumours, however not common in reconstruction after trauma in which bone lengthening and transport are usually required.
Demineralised Bone Matrix
Demineralised bone matrix (DBM) was first observed by Urist in 1965 to induce heterotopic bone. The active components of DBM are a series of glycoproteins, which belong to a group of transforming growth factor family (TGF-β). The members of this group are responsible for the morphogenic events involved in the development of tissue and organs. Urist later isolated a protein from the bone matrix, which was termed as the bone morphogenic protein (BMP). DBM is commercially available and used in management of non-union of fractures. They are not suitable where structural support is required. To date, the main delay in developing clinical products has been the need to find a suitable carrier to deliver the BMP to the site at which its action is required. New generation ceramic composites/hybrids could fill this gap. Experimentally, BMP-2 and OP-1® (BMP-7) have been shown to stimulate the formation of new bone in diaphysical defects in the rat, rabbit, dog, sheep and non-human primates. The use of BMP’s with new calcium phosphate derivatives or composites could be used for bone remodelling where bone regeneration and remodelling is needed such as therapeutic applications in osteoporosis.
Bovine Collagen/Hydroxyapatite Mixtures
Bovine collagen mixed with hydroxyapatite is marketed as a bone-graft substitute, which can be combined with bone marrow aspirated from the site of the fracture. Although no transmission of disease has been recorded, their use will continue to be a source of concern. This material is osteogenic, osteoinductive and osteoconductive however it lacks the structural strength required.
A complete set of references can be found by referring to the original paper.
Primary author: G. Heness and B. Ben-Nissan
Source: Abstracted from “Innovative Bioceramics” in Materials Forum, Vol. 27, 2004.
For more information on this source please visit The Institute of Materials Engineering Australasia.