We performed a retrospective examination of the anteroposterior pelvic CT scout views of 419 randomly selected patients between April 2004 and August 2009 in order to determine the prevalence of cam-type femoroacetabular deformity in the asymptomatic population. The CT scans had all been undertaken for conditions unrelated to disorders of the hip. The frequency of cam-type femoroacetabular deformity was assessed by measuring the α-angle of each hip on the anteroposterior images. The α-angles were classified according to the Copenhagen Osteoarthritis Study. Among 215 male hips (108 patients) the mean α-angle was 59.12° (37.75° to 103.50°). Of these, a total of 30 hips (13.95%) were defined as pathological, 32 (14.88%) as borderline and 153 (71.16%) as normal. Among 540 female hips (272 patients) the mean α-angle was 45.47° (34.75° to 87.00°), with 30 hips (5.56%) defined as pathological, 33 (6.11%) as borderline and 477 (88.33%) as normal. It appears that the cam-type femoroacetabular deformity is not rare among the asymptomatic population. These anatomical abnormalities, as determined by an increased α-angle, appear to be twice as frequent in men as in women. Although an association between osteoarthritis and femoroacetabular impingement is believed to exist, a long-term epidemiological study is needed to determine the natural history of these anatomical abnormalities.

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.