The options: how do you decide which hip replacement to have?
The first thing to decide is whether you need a traditional Total Hip Replacement (THR) or whether you might be a candidate for resurfacing, a relatively new operation that emerged in the mid 1990s.
Total hip replacement (THR)
A total hip replacement is what most people will end up with, but there are still myriad options.
In a THR, the surgeon is essentially replacing the hip's natural ball and socket joint with an artificial one. First he removes the top part of the thigh bone and inserts a long shaft with a ball at the top end. He then hollows out the hip socket and puts in an artificial socket. The two parts – the ball and socket – then slot in to each other.
For a start, there are 70 types of artificial joints (prostheses), which vary in shape and design (the most common are the Charnley and Exeter hips), and also in material, which can be plastic, ceramic or metal.
The most widely used combination is a metal ball with a plastic socket (doctors call this “metal-on-plastic”).
Increasing numbers of surgeons, especially in private hospitals, are using cementless THRs, where the bone grows into the replacement parts, or a ‘hybrid’, where one part is cemented in but not the other.
Whether to use cement to fix the hip replacement
The next decision is whether to use cement to fix the replacement parts in place. A THR with cement is the traditional choice, and still the most popular; it accounts for 50% of all hip operations.
In a cementless THR, the surface of the replacement part is roughed up and sometimes a coating is applied to encourage the bone to grow through it, but no adhesive is used.
The surgeon needs to hammer the new joint in place very firmly. Non-cemented hips are thought to last longer, but the downside is that it is more difficult to remove the new joint if there is a problem.
As research has shown that orthopaedic surgeons who do the most operations of a particular type get the best results, it's often best to stick with their recommendation.
“We do get patients who have read about the latest developments on the Internet and want to find out more, which is fine,” says John Hodgkinson, consultant orthopaedic surgeon at the Wrightington Hospital, where Sir John Charnley pioneered total hip replacements in 1962.
“There are theoretical advantages and disadvantages for all of the options. For example, with a plastic socket, you get tiny fragments of plastic collecting around the hip joint in a kind of sludge. But with metal, although it is harder and will theoretically last longer, there is the risk of tiny metal particles entering the bloodstream. Patients can look on the internet and find evidence to support any position.”
Like Mr Hodgkinson, the Government's National Institute for Health and Clinical Excellence is a fan of the THR with cement because it is the tried and tested option.
Its guidance says doctors should choose a hip that has been proved to last more than 10 years, and if they opt for a newer type, it should have three years’ evidence and be on target to meet the 10-year benchmark.
There is now a National Joint Registry, set up to collect data on all hip (and knee) replacements in England and Wales, in both NHS and independent hospitals.
You can download the NJR’s annual report at www.njrcentre.org.uk, for information on prostheses used, techniques and outcomes.
Are you eligible for resurfacing?
Resurfacing now accounts for 5-10% of all hip operations, although it's usually only offered to younger patients. Because there is less risk of dislocating a resurfaced hip, it can be useful for those who still want to do sports like skiing and mountaineering.
With resurfacing, the surgeon doesn't need to remove as much of the thigh bone. Instead he fits a metal cap over the top of the bone and resurfaces the hip socket with metal, so the two parts move together.
“Resurfacing is only really suitable for younger patients, generally women aged up to 55 or 60, and men aged up to 60 or 65,” says Graham Keene, consultant orthopaedic surgeon at BUPA Cambridge Lea Hospital.
“As we get older, our bones become weaker and the risk of a fracture with resurfacing is thought to be too high.”
Resurfacing is just as major an operation as a total replacement, and recovery times are similar.
Doctors agree not enough is known about the side effects of resurfacing, which include the theoretical risk of metal contamination.
What are the risks of hip surgery?
Hip replacement and resurfacing are major operations, usually lasting one to two hours, and there are always small risks to the heart and brain.
The main risk is of infection, which is why almost all hip operations are done in a specially ventilated operating theatre.
In a survey of hospitals by healthcare analysts Dr Foster, infection rates varied from none to 1.5%.
Around 3 per cent of patients get a blood clot in the leg during the operation, which can be treated with blood-thinning drugs, although it is a potential killer if it moves to the lungs. Problems with blood clots will usually become apparent within three months. Wearing an elastic stocking after the operation helps prevent this.
Very rarely, hip bones crack during the operation (this happens in less than 4 out of every 1,000 cases). The surgeon can usually fix it, but it may delay recovery.
Dislocation of the new hip is a risk, especially in the first six months, leading to a second operation.
In the longer term, one in three patients may end up with one leg longer than the other. Up to 1cm doesn't really make a difference, but any more than 1.5cm and the patient may need shoe inserts. With resurfacing, this is not usually a problem.
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