When surgeons and engineers collide, miracles can happen!
One such collaboration began some 35 years ago between Dr Clive Lee of the Department of Engineering at the University of Exeter and Robin Ling of the Department of Orthopaedic Surgery at the Princess Elizabeth Orthopaedic Hospital. The result was the ‘Exeter hip’.
At the BA Festival of Science on Wednesday September 8, 2004, Dr Lee will describe the evolution of what is now the produced the most widely used cemented hip joint in the world – from its conception as an idea, through initial development, those first implants (and the lessons learned) and the design modifications which followed.
There have in fact been 3 changes to the hip since the very first implant in 1970.
The first a change in surface finish of the femoral stem, from polished to matt, the second a change back from matt to polished and finally a change to a modular system for the stem.
Data will be presented showing the clinical results of the original stem at 33 years – 92% survivorship for mechanical loosening. The modular polished stem has even better results, most probably due to better cementing technique and has 100% survivorship at over 12 years. Truly remarkable!
The difficulties in collecting and reporting the results of hip arthroplasty will be presented, leading to the conclusion that improvements of one implant over another are very difficult to demonstrate in less than a decade of clinical use and may take more than two.
So, what of the future?
Dr Lee says,
‘It would be arrogant to suggest that the current design of the Exeter hip is the best possible and new designs are being proposed by a number of centres. Plainly, any new design should be at least as good as existing designs and preferably better than existing designs.
There is no way that an engineer or an orthopaedic surgeon can use laboratory tests or computer simulations to predict the long term clinical performance of a new design of implant. This means that new designs have to be tried out in people.
Although some useful information can be obtained by RSA and other modern investigatory techniques, there is no doubt that the only way to test and to prove a new design of hip joint is to use it in people for at least 10 years.’
There is a clear moral and ethical dilemma here – is it justified to replace a design that we know will last more than 20 years, and probably more than 30 years, with a new design, when we have no means of telling whether the new one will actually survive 5 years or even 10 years? Coupled with this, today companies are directly marketing hip joints to patients using results that are scientifically not justified. The new fashion of patient choice is empowering patients to choose designs when they have no real knowledge of the reliability of the marketing information.
Is ignorance bliss? With total hip replacement is a very common procedure in the NHS, how can patients ensure the best implant is being used for their hip? Newer is commonly not necessarily better.
The ethics of experimenting on people with new devices when existing devices satisfy the requirements of, perhaps, 90% of patients will be discussed.
Supported by the Royal Academy of Engineering, the whole day promises to be a treat for all those attending with six presentations in total, a panel session and press conference.
Notes for editors
Founded in 1976, the Royal Academy of Engineering promotes the engineering and technological welfare of the country. Our fellowship - comprising the UK’s most eminent engineers - provides the leadership and expertise for our activities, which focus on the relationships between engineering, technology, and the quality of life. As a national academy, we provide independent and impartial advice to Government; work to secure the next generation of engineers; and provide a voice for Britain’s engineering community.
The BA is the UK’s nationwide, open membership organisation dedicated to connecting science with people, so that science and its applications become accessible to all. The BA aims to promote openness about science in society and to engage and inspire people directly with science and technology and their implications.
The BA Festival of Science is one of the UK’s biggest science festivals. It attracts 400 of the best scientists and science communicators from home and abroad who reveal the latest developments in research to a general audience.
The BA Festival of Science 2004 will take place at the University of Exeter from 6 - 10 September 2004, and throughout the city from 4 - 11 September. The Engineering Section ‘Where have all the engineers gone?’ takes place on Wednesday 8 September. The engineering session, Where have all the Engineers Gone? takes place on Wednesday 8 September, 09.30 – 17.00, Queen’s Building LT2.
For more information please contact
Dr Claire McLoughlin at the Royal Academy of Engineering
Craig Brierley at the BA, tel: 020 7019 4947