BBC Focus Magazine

[M Paul Lloyd]

I was reading Robert Matthews latest ‘The Analyst’ in the April issue about the pitfalls of statistical analysis in medicine and (providing I actually understood it all correctly) I have to say I drew some small solace from what he had to say.
You see I had just heard a rather draconian announcement on the radio made on behalf of some panel from Bristol University or other to the effect that, in their collective expert opinion, all metal on metal, and not just some but “all”, metal on metal large ball hip replacements should be banned due to their apparently being twice as likely to have adverse side effects than the metal on plastic variety.
http://lifestyle.aol.co.uk/2012/03/13/m ... be-banned/
http://www.businessweek.com/news/2012-0 ... eview-says
http://www.nhs.uk/news/2012/03march/Pag ... rates.aspx
http://www.cbsnews.com/8301-504763_162- ... udy-warns/
This is said to be as a result of observational studies that show the metal on metal hip joints result in an unacceptable amount of wear leading to metals, specifically chromium and cobalt, entering the blood stream and surrounding tissue resulting in massive inflammation and adverse, carcinogenic side effects on overall patient health etc etc.. With the qualifying statement pointing out that metal on metal joints are "twice as bad as metal on plastic".
But here’s the thing, I’m not so sure what to make of this because although the published statistics appear to show that metal on metal has double the risk of complications the actual numbers don’t really say that.
So lets have a closer look at the actual figures.
Metal on plastic joints are reckoned to be 97% successful which is 3% short of the ideal whilst metal on metal are 94% successful which is 6% short of the ideal so yes I guess you could say that the failure rate of metal on metal hips is twice that of the metal on plastic but in reality metal on metal hips are only a few percent behind the metal on plastic.

So its all just so much meaningless fiddling of the figures, isn't it?

Another point that doesn’t seem to have been taken into account is the fact that metal on metal hips are generally given to younger and more active patients than the metal on plastic which often end up in older more sedentary subjects and I have to say that in my admittedly limited experience of other metal on metal hip replacement patients quite a few of them seem to treat these prosthetic joints with what I can only describe as reckless, gay abandon and appear quite happy to carry on with running marathons, cycling over the local moors, climbing mountains, ski-ing, snowboarding, surfing or indeed whatever they can throw themselves at as if they had been given a veritable ‘Steve Austin’ style bionic super joint!

This can’t be right surely?

No artificial joint is going to be anywhere near as good as a real one and treating it as such is surely going to lead to problems?
So I suggest that the 6% of metal on metal joints that show signs of accelerated wear may in effect have been abused by some of their owners and this apparently science based scaremongering via the press is just another example of how badly science and medicine can be represented in the popular media.

For myself I already have a large ball all metal right hip joint to my right hip which is working just fine thank-you and am scheduled to receive another of the same design to my left in about a weeks time. Now although the announcement that they should be banned did rattle me a little at first I must admit Robert Matthews comments have, in a roundabout way made me feel a whole lot better about it all.
So unless I hear otherwise I’m going to go ahead with the metal on metal hip replacement and if need be act as a sort of human guinea pig and we shall see if I suffer any long term effects of having, not one, but two of these apparently infernal devices.

I'll keep you posted.