Zimmer | Durom Hip Resurfacing | Which Medical Device
From Which Medical Device
The Durom hip resurfacing is a metal-on-metal hip resurfacing introduced in 2003. The device has a Metasul® bearing, which is wrought-forged Cobalt Chrome – the Protasul-21 WF alloy. This bearing was developed by Sulzer (subsequently Centerpulse, itself acquired by Zimmer in 2003), and has a proven track record in smaller diameter heads. The femoral component has a more slender stem than other designs and a macro-grooved internal surface for cement interlock – the instruments are designed to provide a consistent 1mm mantle of cement.
The acetabular component subtends a 165 degree angle, and has the shape of a flattened dome. There are 2mm thick fins around the periphery of the cup to provide immediate rotational stability and which effectively give a peripheral flare to the socket. It has a titanium plasma sprayed coating (Porolock™) which has a roughness of 20-50 microns and is high friction. The component is 4mm thick across the range of sizes (3mm in the US version). The Durom cup was withdrawn from sale in the United States in 2008 following reports of early failure when used with a standard femoral stem (Long et al). Although the US design was different to that in the rest of the world having a slightly different structure and a slightly thicker coating, at least one non-US series has also reported relatively high revision rates (survival 92.4% at 4.8 years) (Berton et al). It has been suggested that bone ingrowth into the surface may not have been as good as for other sockets (Illgen et al), but this may relate to the shape of the socket and the fact that the socket does not always get contact with host bone if a standard hemispherical reaming technique is used (Long et al). The technique for implantation has been the focus of some debate – the peripheral fins mean that the position of the socket should likely not be adjusted once implanted.
The 9th National Joint Registry Report for England and Wales reports that the Durom head had 1608 implantations and a 5 year all cause revision rate of 5.99% (4.74 to 7.58), compared with 3.67% for the Birmingham Hip Resurfacing and 13.77% for the ASR.
Other published results state an 88.2% survival rate at 5 years in a series of 100 patients (Naal et al). The Australian Joint Registry in 2008 reported a three year cumulative revision rate of 5.8% for the Durom resurfacing (compared with 6.0% for the ASR and 2.5% for the Birmingham Hip Resurfacing)
A retrieval study published in 2011 suggested that reduced sphericity of the femoral component might have lead to equatorial bearing and loosening of the acetabular component in the Durom system, although the device exhibited lower wear than the Birmingham Hip Resurfacing (Matthies et al).
Read our roundup of hip resurfacing devices.
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