New advance for artificial joints

A new type of artificial hip, more robust and longer lasting than conventional artificial joints, is to undergo clinical trials and could be available for patients within five years.

These ‘ceramic-on-metal’ joints are said to cause less damage to the surrounding bone than conventional artificial hips, so many recipients will avoid the need for further surgery. They could also lower the age at which it is practical for patients to undergo hip replacement, helping them to continue to lead active lives. The limitations of conventional artificial hips mean that many patients are advised to wait as long as possible, often in considerable discomfort, before having an artificial hip put in place.

The research is being carried out by engineers, medical researchers and biologists at the University of Leeds, underpinned by funding from the Engineering and Physical Sciences Research Council (EPSRC).

This research continues work carried out by the same team to develop ‘metal-on-metal’ joints, which have been in use for a number of years. The ceramic part of the new artificial joint is the knuckle head and the cup of the hip is made out of the metal.

“An increasing number of younger and active patients now need hip replacements, and are demanding better-performing artificial joints,” said lead researcher Professor John Fisher of the School of Mechanical Engineering. “These recent developments will lead to a ten-fold improvement in wear performance.”

Local bone damage occurs because, as the head of an artificial hip rubs against the cup that holds it, tiny wear particles are produced. These accumulate over time and cause an adverse reaction in the living cells around the implant, leading to the death and eventual loss of bone tissue.

‘Metal-on-metal’ and ‘ceramic-on-metal’ joints generate a lower volume of wear particles than traditional ‘metal-head-in-polyethylene-cup’ implants. The metal particles are also much smaller and so disperse more readily around the body. In contrast the polyethylene wear particles are larger, being micron or sub-micron in size, these are retained in tissues around the artificial joint and stimulate inflammation and bone loss, which leads to loosening and failure.

Currently over 10% of hip replacement patients need follow-up operations to address problems caused by damaged bone tissue. The new hips could cut this figure significantly, reducing the risk of dislocations and other long-term problems.