Given that an artificial hip joint (say) has a finite life before the balljoint wears out, and given that there’s a very limited number of times this joint can be replaced due to the bone fixings, would it not be possible to make a servicable replacment joint? Have permanent anchor fixings attached to the bone at both ends, and a bolt-in replaceable joint in the middle. When the joint wears out, then it’s just a matter of soft tissue surgery to replace the relevant section.
Is there any good reason why this isn’t done, or is it standard practice in some places and I’m just stultifyingly ill-informed?
Depending on whose figures you use, up to 80-90% of the current generation of replacement hips may be expected to function satisfactorily at 10 years (vs. closer to 60% 10 years ago). It’s hard to accurately compare figures for longer terms, because a patient who has had a replacement hip for 25-30 years was probably much younger, and very possibly more active, than the typical hip replacement candidate!
While there has been substantial work in prostheses such as you describe, one of the major causes of failure, especially in load-bearing joints like the hip and knee, is aseptic loosening of the prosthesis within the bone, rather than wear on the artificial articulating surfaces. This makes your fine idea rather less useful than it might seem.
Of course, as I said, there has been work on this, and it is possible that newer cements are now available that would increase interest in replaceable articulating surface. Presumably some orthopod or biomechanical engineer will be along shortly to bring us up to date
Thanks KP, that does make sense. I guess I was assuming that the bone mounts remain solid like a screwed-in fracture plate, but I suppose plates aren’t very load-bearing once the broken bone heals.
My husband’s knee is estimated to last 30 years. It is made of pure zirconium and has a coating of zirconium oxide. He has sensitivities to some metals, including copper, that made using traditional replacements out of the question. There was some talk of using platinum, but this artificial knee was released after initial studies and they decided to use it. The advantage is that the surface is more slippery when wet, as well as being harder; there will be less surface wear down, and less loss of smoothness that would impact the functioning of the knee.