Advances in surgery Can a new joint put a spring in your step? Diane Back and Angus Lewis outline sporting possibilities and cautions for replacement hips and knees
In the past 20 years there has been an explosion in the number of total joint replacements performed throughout the world(1). Hips and knees are the most commonly replaced joints, but shoulders, elbows and ankles can all be done, too.
Hip and knee replacements were originally designed for elderly people, generally over the age of 70, who led relatively sedentary lives and who were not expected to outlive the lifetime of the prosthesis. The ability of these artificial joints to relieve pain and maintain everyday mobility has been a revolution in the treatment of arthritic conditions, and we would expect a new hip joint in these elderly patients to be good for 15 to 20 years.
With increasing confidence, hip and knee replacements are being given to an ever younger population, who are much more likely to outlast the expected life of their replacement joint and who also place demands on the implants that the original designers would not have considered. Although the technology behind joint replacement surgery continues to evolve, people are pushing the implants to the limit and causing them to fail earlier – after 10 years or less in the case of hips. Because knee replacements are more recent, we can be even less certain about their longevity and what might influence it. While we have data giving more than 95% ‘survivorship’ of knee implants at five to 10 years’ follow-up, this is among the more elderly and less active population(2). For younger patients, we simply do not yet know how they will fare.
Aware as we are in the medical profession of the need to encourage people to pursue healthy lifestyles, what advice should we all be giving to people who have undergone a total joint replacement? Should we advise them to cease all exercise, or do we tell clients and patients to undertake only certain types of exercise and avoid others?
While there are numerous published guidelines on what types of activity people should do after joint replacement surgery, none of them are based on proper randomised control trials. Nevertheless, there is plenty of evidence that the more activity you do, the quicker you will wear out your implant(3). What we’re less clear about is whether impact in particular makes much difference. Most studies recommend a reduction in impact sports to minimise the likelihood of wear on the bearing surface and decrease the chances of loosening the implant(4-6).
There is no doubt that patients who participate in sport after knee and hip replacements are at higher risk of traumatic complications, including dislocation, fracture around the prosthesis and even failure of the implant. The likelihood of doing serious injury to the replacement joint while playing rugby is far greater than if you restrict your activity to playing a sedate round of golf!
While clients and patients need to be aware of the relative risks involved, the current literature does not offer a great deal by way of helpful advice, with opinion, even among orthopaedic surgeons, divided as to what exactly we should be recommending as harmless or beneficial.
For total hip replacement, there is general consensus that impact sports should be avoided:
The materials used in total hip replacement vary but these days most implants consist of a metal head articulating on a polyethylene cup. The polyethylene has been shown to wear more with increased weight-bearing activities. Work has been done on other kinds of bearing surfaces, such as ceramic heads articulating with ceramic cups.
Also in the past 10 years there has been a resurgence of interest in ‘hip resurfacing’, a procedure that aims to preserve a significant proportion of the femoral head and leaves the femoral canal intact. This produces a bigger ball and socket joint, which holds out much better prospects for the stability of the joint. The new generation of hip resurfacings tend to incorporate a metal head with a metal cup articulation in the belief that this will produce less ‘wear debris’ and reduce the chances of loosening of the implants.
Studies have shown that after hip resurfacing, people are able to undertake sports that would have been on the banned list for a total replacement, including downhill skiing, squash, football, judo, horse riding, triathlon and running.
There is a big proviso, however: we still have only three years’ worth of evidence of joint performance among hip-resurfacing patients, so it is too early to tell whether these dramatically increased levels of activity involving high impact sports will also cause a decrease in the durability of the prostheses. Likewise, we have no long-term follow-up studies yet on how the new materials affect the longevity of resurfacings.
With the exception of cross-country skiing the general advice about avoiding impact sports is much the same as for hip replacements. But the reality is that total knee replacement seems to be far less forgiving with regard to sporting activities. Several studies show that a significant number of patients do not return to their pre-replacement sporting activity(7,8). At present artificial knee joints don’t seem to be able adequately to reproduce the complex twisting mechanism of the natural knee and many enthusiasts find they are unable to maintain their chosen sports.
Total shoulder and elbow replacements are less common. There are fewer problems about weightbearing surface but joint stability can be an issue. One study did show that after shoulder replacement, significant numbers of golfers did return to their sport and even improved their handicaps.(9)
Total ankle replacement is very much in its infancy. There have been numerous problems with fixation of these implants and there is nothing in the literature to guide us about sporting activity, although the general recommendation for no impact sport would probably be appropriate.