Abstract
The search for the ideal bearing surface in Total Hip Replacements continues. The current ‘best’ materials are felt to be combinations of metal, ceramics and cross-linked polyethylene. Laboratory studies suggest that ceramic-on-metal articulations may provide distinct advantages. This study aims to identify the best bearing surface combination with the lowest adverse side effect profile.
Between February 2004 and September 2007, 164 hips were replaced in 142 patients. 39% were male and 69% were female. The average age at surgery was 53 years (17-72 years). Follow-up assessment included radiographs, the Harris Hip Score and whole blood samples for metal ion levels. Complications to date included 3 hips which needed femoral revision because of surgery related factors, and 3 cases of sepsis of which 1 settled and 2 needed revision. One hip needed revision of head and liner to a larger bearing size for recurrent dislocations, and is no longer being followed up for blood metal ions.
Post-operative whole blood metal ion levels were compared to pre-operative levels to determine the increase or decrease in metal ion levels. There were no changes in those patients with ceramic-on-ceramic and ceramic-on-polyethylene articulations. Moderately raised whole blood metal ion levels were noted at 3 months in the ceramic-on-metal group, while the metal-on-metal group show the greatest increase.
This study agrees with laboratory bearing surface wear studies demonstrating lower wear rates in the ceramic-on-metal group compared to the metal-on-metal group. With concerns related to high blood metal ion levels in metal-on-metal articulations, ceramic-on-metal bearing surfaces may well become a bearing surface of choice in the future, but progress needs to be monitored in the longer term.
