Bone allograft use in trauma and orthopaedic surgery is limited by the potential for cross infection due to inadequate acceptable decontamination methods. Current methods for allograft decontamination either put the recipient at risk of potentially pathogenic organisms or markedly reduce the mechanical strength and biological properties of bone. This study developed a technique of sterilization of donor bone which also maintains its mechanical properties.

Whole mature rat femurs were studied, as analogous to strut allograft. Bones were inoculated by vortexing in a solution of pathogens likely to cause cross infection in the human bone graft situation. Inoculated bones were subjected to supercritical carbon dioxide at 250 bar pressure at 35 degrees celsius for different experimental time periods until a set of conditions for sterilization was achieved. Decontamination was assessed by vortexing the treated bone in culture broth and plating this on suitable culture medium for 24 hours. The broth was also subcultured. Controls were untreated-, gamma irradiated- and dehydrated bone. Mechanical testing of the bones by precision three-point bending to failure was performed and the dimensions and cross-section digitally assessed so values could be expressed in terms of stress.

Mechanical testing revealed bone treated with supercritical carbon dioxide was consistently significantly stronger than that subjected to gamma irradiation and bones having no treatment (due to the minor dehydrating effect of the carbon dioxide). Terminal sterilization of bone is achieved using supercritical carbon dioxide and this method maintains the mechanical properties.

The new technique greatly enhances potential for bone allograft in orthopaedic surgery.