Stretching implant life

A researcher from Cambridge University’s engineering department has been awarded a €1.5m (£0.9m) grant from the European Research Council (ERC) to set up a research group to improve the lifespan of prosthetic implants such as hip replacements.

Bone is an active material, it responds to stresses and strains. But in the absence of straining, bone adjacent to implants can become unhealthy, contributing to loss of adhesion.

For implants to be successful and to last for a reasonable length of time, it is recommended that patients follow physical exercise regimes. But in cases where the patient is completely immobile or with very restricted mobility, this is not possible. In these cases, drugs are often administered that can have side effects.

Now, researcher Athina Markaki and her team are working on a therapy whereby controlled levels of mechanical strain could be induced directly in growing bone via the prosthesis itself.

The idea is that the implant should have a highly porous surface layer, made by bonding ferromagnetic fibres together, into which bone tissue growth would occur. During the post-operative period, the application of a magnetic field will then cause the fibre network to deform elastically, as individual fibres tend to align with the field. This will impose strains on the bone tissue as it grows into the fibre network.

Such mechanical deformation is known to be highly beneficial in promoting bone growth, providing the associated strain lies in a certain range. Preliminary work, involving both model development and experimental studies on the effect of magnetic fields on fibre networks, has suggested that beneficial therapeutic effects can be induced using field strengths no greater than those already employed for diagnostic purposes.

The project will be carried out in collaboration with the Orthopaedic Research Unit (ORU), Department of Surgery at Cambridge University.