Abstract
Corrosion at the taper interface between the femoral head and the femoral stem is well described in metal-on-polyethylene (MoP) hips but previously was undetermined in large diameter head metal-on-metal (LHMoM) hips. The high failure rate of the articulating surface replacement (ASR) XL hip system has been partly attributed to susceptibility to corrosive damage at the taper interface. It was not known if other hip manufacturers are liable to taper corrosion. Therefore the aim of this study was to quantify the prevalence and severity of taper corrosion in LHMoM hips and compare corrosion across five different current generation manufacturers.
Taper corrosion was analysed in a consecutive series of the five most common hip types at our retrieval centre: ASR XL, DePuy (n=49); Birmingham hip resurfacing, Smith & Nephew (n=33), Durom, Zimmer (n=31), M2a Magnum, Biomet (n=14) and Cormet, Stryker (n=10). A four-scale peer-reviewed qualitative corrosion scoring system was used to quantify corrosion (none, mild, moderate and severe).
Evidence of corrosion was observed in 86% of components, with at least moderate corrosion observed in 61%. No difference in corrosion was observed between the ASR XL and the other manufacturers (p=0.202). There was still no difference seen when all manufacturers were compared individually (p=0.363). A positive correlation was observed between corrosion and femoral head diameter (r=0.224, p=0.021). However no relationship was observed with implantation time (r=0.163, p=0.118).
Our study indicates that taper corrosion is common in LHMoM hips and affects all hip types equally. The clinical significance of this finding is that all hip types will be susceptible to the complications of corrosion, such as third body wear and osteolysis. Furthermore recent reports indicate that corrosive debris released from the taper interface may play a role in the formation of pseudotumours and adverse soft-tissue reactions. We found that larger femoral head sizes showed greater corrosion, which suggests that high torque increases fretting corrosion of the taper interface. Future work must determine the optimum femoral head size and investigate the chemical composition of the corrosive debris.
