Background

There have been limited published reports on the clinical results of cervical artificial disc replacement. Goffin et al reported a 90% rate of good to excellent results at 1 to 2 yrs after Bryan disc replacement. Wigfield et al reported a 46% improvement in pain and 31% improvement in disability 2 yrs after Prestige cervical disc replacement.

Tissue engineering in reconstructive surgery has many potential attractions, not the least to avoid donor site morbidity and reduce the potential need for allografts and prostheses. Currently there are only two products that have FDA approval in the United States, namely skin and cartilage. Other potential products being trialled are artificial blood vessels and heart valves. The common denominator of these is that they are essentially two dimensional and relatively avascular. Three dimensional tissue engineering has three essential components, (1) cells, (2) scaffold and (3) blood supply. Cells are most easily derived from an autologous source, by conventional tissue culture where they are expanded and implanted into the required site. They are committed cells and usually a large source of donor tissue is required to obtain an adequate source of cells for reconstruction. Stem cells have the potential to grow and differentiate, they may be embryonal which introduces ethical problems or adult stem cells. Cells can be genetically engineered to produce specific growth factors for the purpose of further cell proliferation, such as vascular endothelial growth factor for angiogenesis. The second essential is a scaffold for cells to adhere to and grow. This is particularly important for the development of the vascular network. Fibrin, PTFE (Dexon) Matrigel (a form of Laminen) or collagen are the most popular forms of matrix. The third and most essential component for three-dimensional tissue engineering is vascularization. To date, most tissue engineering research involves invitro studies of cell differentiation and growth but the invivo potential is limited because of inability to transfer a blood supply.

At the Bernard O’Brien Institute at St Vincent’s Hospital, Melbourne, we have developed a model of invivo tissue engineering which involves the initial creation of a vascular core inside a plastic chamber which can be moulded to any desired shape. This construct seems to be an ideal environment for seeding of cells, including stem cells which allows them to survive and differentiate into various mesenchymal tissues. To date we have been able to generate skin flaps, fat, tissue and skeletal muscle. Although our prime interest has not been bone or cartilage it is reasonable to assume that this can be relatively simply produced in the same model from either stem cell sources or by the use of differentiating factors.