An experimental study was performed in order to investigate methods of preparation and mechanical properties of a potential bone graft substitute. This new composite material consists of porous hydoxyapatite coated with oxidised cellulose.

Porous hydoxyapatite has excellent osteoconductive properties and promising strength characteristics. Drawbacks include its lack of osteoinductive properties and its brittle nature. Oxidised cellulose can be functionalised to provide binding sites for proteins, drugs and cells, which would allow for increased osteoinductive activity. It has good tensile strength. By creating a composite of these two substances, it was proposed that a graft substitute could be created.

Hydroxyapatite samples were formed by processing and sintering bovine cancellous bone. A method was devised by which cellulose was brought into solution and infiltrated into hydoxyapatite samples. The cellulose was then regenerated (cured) and oxidised.

Infrared spectrometry confirmed the desired chemical reactions took place and that oxidised cellulose was formed. Scanning electron microscopy confirmed that the three-dimensional structure of the hydroxyapatite was satisfactorily coated. Crush testing showed that infiltrated samples were less brittle and more likely to hold their shape than control samples.

Further development and testing is required to assess this composite material for its biological activity and potential as a bone graft substitute.

The purpose of the study was to assess the incorporation of defatted, and deproteinated bovine cancellous bone in a sheep bone graft model. Cylindrical defects were created in the femoral condyles of 12 sheep using custom-made trephines. The defect was filled with a cylinder of prepared bovine bone. The removed cylinder of bone was implanted into a defect created in the opposite femoral condlyle. Fluorochrome bone labels were administered over an 8-week period and the sheep sacrificed at 10 weeks. Undecalcified thin bone sections were viewed with a fluorescent microscope.

ln one sheep there was a technical problem leading to unsatisfactory histology. All other sheep showed similar histology. The autograft incorporated rapidly with the graft showing a rim of reactive bone and the graft itself showing rapid laying down of new bone on its surface. The xenograft showed a similar reactive rim of new bone with deposition of new bone throughout the graft and resorption of the graft material.

This study demonstrates that specially prepared bovine cancellous bone can act as a scaffold for the depostion of new bone in a sheep model. The role of this material in humans is to be evaluated.