University of Portsmouth installs country’s first hip simulator for fatigue testing

The Portsmouth Hip Simulator, the first in Britain to fatigue test  implanted hip joints, has been installed at the University of Portsmouth .  The equipment applies realistic physiological hip joint forces to artificial hip joints, and enables the durability of the fixation of implants to be assessed.

Designed by the researchers in the Department of Mechanical and Design Engineering in collaboration with Simsol, a specialist company that builds simulation equipment, the £110k machine simulates the direction and the magnitude of hip contact force experienced by a hip joint during a range of daily activities including walking, standing up from a chair and stair climbing and descending.

Typically, at least one million steps are taken by an individual per year, equivalent to one million loading cycles experienced by the hip joint with a maximum hip contact force of up to three times body weight during each step.

“Simulating these forces in the laboratory means that we can obtain results within a few months which, if tested on a patient, would take years,” said Dr Tong, who leads the Biomechanics research team.

“There is an urgent need to revisit the Total Hip Replacement (THR) with a view to improving the fixation beyond 10 to 20 years”, said Dr Tong.  “This will drastically reduce the need for revision surgery which is an important factor in an aging population”.

THR is one of the most successful surgical procedures ever developed where an artificial ball-socket structure is used to replace the diseased or damaged hip joint. The replacement cup is usually attached to the pelvis by acrylic bone cement.

An estimated one million THRs are performed annually worldwide, and more than 43 000 are carried out each year in Britain . It is predicted that by 2010, 20 per cent of the population will be over 60, and 40 per cent of those will have osteoarthritis, for which THR is the primary treatment.

Research carried out by Dr Tong’s team will focus on studying the failure mechanism of the current cemented THRs and result in recommendations to orthopaedic surgeons to improve surgical procedures in order to improve the longevity of the artificial hip joints.  

For further information please contact:

Anne Stanford

University of Portsmouth

02392 842721

(20/6/05)