Glass bones

Degenerative bone disease is a growing problem throughout the world. Approximately 90 per cent of the population over the age of 40 suffer to some extent with this condition. While normal repair processes fail with age, injury, infection or excessive loading may also be contributory factors. Moreover, life expectancy in prosperous parts of the world currently stands at 80+ years, which means that many people will exceed the natural lifespan of their own connective tissues, particularly bone and cartilage. Current statistics reveal that 33 per cent of women and 17 per cent of men, between the ages of 80 to 90, get hip fractures.  

A general problem with artificial replacement joints - usually a polished metal ball mounted on a metal femoral stem and a polymer or alumina cup - is that of stress transfer from synthetic materials, whose mechanical moduli (elasticity) are very different from that of the host bone. Changes in mechanical loading following hip replacement cause demineralisation of bone from the inner wall of the femur, which can lead to loosening of the femoral stem. Additionally, wear debris from the articulating prosthetic joint is also a common problem that provokes the body's immune response and tends to require revision surgery. While bone transplantation is an alternative, the lack of donors and tissue compatibility limit the usefulness of this approach. Current research is focusing on the design of bioactive glass and ceramic scaffolds that could be used to enhance the body's own repair mechanisms, and thus regenerate compromised bone tissue in situ.