Would you still do a metal on metal hip resurfacing? A roundup of hip resurfacing devices
Published date : 06 June 2011
Article date : 06 June 2011
The last few months have been particularly difficult for many involved in hip resurfacing. The flush of enthusiasm for the technology seen five or so years ago has been replaced by a race for the exit for many. Problems with the ASR device in particular have made the headlines and mainstream media, and there is the spectre of further failures to come following the enthusiastic implantation of large bearing metal-on-metal hip replacements on standard stems : the term trunionosis* has been coined and is rapidly being adopted into the orthopaedic vernacular.
It may therefore be an ideal time to review the hip resurfacing devices which have been, and still are available and we have product descriptions for ten of these here.
The list includes devices with established track records, devices which have yet to prove themselves, and devices which have been withdrawn or which may have poorer results than others. In the first category, the Birmingham Hip Resurfacing is perhaps the best established device, with excellent published results. However, it is likely that even enthusiasts are limiting their indications, avoiding younger patients and those needing smaller sizes. Socket placement remains a critical part of the procedure, as experience shows it is particularly important to avoid open sockets and impingement. and patients should be carefully followed up. The ADEPT hip resurfacing is a very similar device, with similar (albeit shorter term) results; the MITCH resurfacing from Stryker is also similar, coming as it does from the same manufacturer, but has few published results to speak of so far, being preentry by ODEP criteria. The Conserve Plus has good results from a single centre and an ODEP 5A rating, but is yet to be widely adopted.
The ReCap Hip Resurfacing has a UK ODEP 3A rating, but appears to have a higher revision rate in the Australian and England and Wales National Joint Registries than the Birmingham Hip Resurfacing. The Cormet 2000 has an ODEP 5B rating, but also has higher revision rates in these registries.
Unknown quantities amongst hip resurfacings include the Minimally Invasive Hip Resurfacing, which is yet to publish results. The ACCIS Hip from implantcast has a unique ceramic surface engineered finish which shows great promise, but for which published results are also awaited.
The ASR Hip Resurfacing has been withdrawn from the market, and the Durom socket withdrawn from sale in the USA. The US version of the latter was a little different from that in the rest of the world, but results elsewhere have not lived up to the promise of the smaller metasul bearing.
It seems likely therefore that the future will see far fewer metal-on-metal hip resurfacings being implanted, and that some of these devices will no longer be used. For some this opens up a gap in the market, which may be filled by devices which are new but also may be unproven (eg short stem hip replacements, ADM X3). It is important that the lessons of hip resurfacing are learned if the potential for similar issues with some of these devices is to be avoided in future.
June 2011.
*Trunionosis The phenomenon whereby wear particles are generated at the trunion or interface between head and stem in a modular hip system. The phenomenon may be exaggerated where there is a large head bearing, and the frictional torque generated at the joint surface is correspondingly large, or where the assembly includes a collar or sleeve between the trunion on the stem and the femoral head.
Editor's note.
Hart points out that this term is misleading because most of the wear occurs on the head side of the taper, rather than on the femoral stem, or trunion. This is important because many meta-on-metal bearing revisions might be possible without changing the stem.
