What is involved in a hip replacement?
Hip replacements are usually performed by making a cut (incision) over the side of the hip and then cutting out the affected bone and replacing it with an artificial part (prosthesis). Some surgeons use minimally invasive techniques. This means that they make just one or two very small cuts instead of one long cut and use specially designed surgical instruments and telescopes. It is thought that there may be less blood loss, less pain and quicker healing with this technique but it is not proven. Your surgeon will discuss with you if this is available.
You will be able to go home once you are eating and drinking normally and are mobile enough to be safe where you are going after you leave hospital. You will have an X-ray before being discharged, to make sure that your hip replacement looks normal.
Are there different types of hip replacements?
Hip replacements can all be divided into two types:
- Total hip replacement (total hip arthroplasty):
- This involves replacing both the 'ball' (femoral head) and the 'socket' (acetabulum) with artificial parts.
- Partial hip replacement (partial hip arthroplasty):
- When either the 'ball' (femoral head) and the 'socket' (acetabulum) is replaced but not both.
The replacement part may be made of various materials, including metal, polyethylene and ceramic. They may be fixed in place using special cement (cemented) or they may not be fixed (uncemented) but designed so that the bone grows over them and fixes them in place that way. The 'socket' part is also sometimes called the 'cup' of the hip replacement.
Metal-on-metal hip resurfacing
Metal-on-metal hip resurfacing (MOMR) is another option. In this operation no part of the joint is removed completely but the surfaces of the ball and socket are removed. A specially designed metal cap is fitted over the head of the thighbone (femur) and another metal component is fitted into the socket (acetabulum). Re-do operations are more common and occur earlier than with hip replacements. MOMR is generally used for fewer patients but is still an acceptable option for younger people, especially men who are wanting to undertake vigorous sporting activity following their surgery (but see below).
Which type of hip replacement should I have?
Your surgeon will discuss this with you. It will depend on who you are. In other words, how old you are, whether you have any other medical conditions and what you want to be able to do once you have had your hip replaced. It will also depend on what types of hip replacements your surgeon is used to performing and which ones are used in their hospital. In the UK the National Institute for Health and Care Excellence (NICE) only recommends devices that are known to last at least 10 years in 95 out of every 100 people who have that type fitted.
All hip replacements can be divided into either cemented or uncemented.
Cemented hip replacement
In the UK more than 9 out of every 10 people who have a hip replacement have a cemented one:
- They fix well
- It is usually possible to get up and move early after the operation.
Uncemented hip replacement
- Easier to re-do, making them possibly more suitable for younger people who are more likely to outlive their replacement.
- Take longer to fix in place so full weight bearing and mobilising are not possible as early as with cemented prostheses.
There is no perfect hip replacement that will suit everyone and some of the differences between all of the different types and makes of hip replacement parts aren't known, particularly how they perform in the long term. In many countries, registries have been set up so that anyone who has had a hip replacement is entered into the register. The information collected is used to monitor how their replacement is performing. In the UK patients also enter information about their health and quality of life before and after their operation.
Metal-on-metal hip replacement (MOMR)
This refers to total hip replacement (THR) and resurfacing, where both the artificial 'ball' (femoral head) and the 'socket' (acetabulum) are made of metal. These were designed to reduce the chances of the components wearing out, especially in younger people who need their joint replacement to last longer, as they are likely to live longer. Unfortunately this does not seem to be the case, especially with a particular THR called De Puy's ASR implant. This turned out not to last as long as other implants and has been withdrawn.
Those patients who have a De Puy ASR implant and any patient with an MOMR (THR or resurfacing) who is getting hip pain, should be seen every year to have a blood test and a magnetic resonance imaging (MRI) scan. These are done in order to monitor any effects of metal debris having been released from the metal ball rubbing on the metal cup or socket; it is not yet know what effects this has on the hip or what effects it might have on your general health. There has been some concern that MOMR may be associated with an increased risk of bladder cancer but the studies have given conflicting results.
Both types of MOMR are being used much less often, as a result of the concerns outlined above.
Further reading and references
Primary Total Hip Replacement: A Guide to Best Practice; British Orthopaedic Association (2012)
Arthritis of the hip (end stage) - hip replacement (total) and resurfacing arthroplasty; NICE Technology Appraisal Guidance, February 2014
Hi all, now that I’ve had my second THR 5 weeks ago (left hip) and have been putting more weight on my other leg (right THR a year ago on that one) I sometimes feel my right joint makes an adjustment...Dsilk05
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