New metal-on-metal and ceramic-on-ceramic hip joints have been criticized of late, particularly with the meta-on-metal hips causing metal to leak into surrounding tissues and the bloodstream, resulting in pain and questionable metal toxicity. Revisions are needed in some cases and this has been an unanticipated consequence of this new technology, as report in the New York Times.
http://www.nytimes.com/2011/12/28/business/the-high-cost-of-failing-artificial-hips.html?scp=1&sq=metal%20hip%20joints&st=cse
This study, looking at the old metal-on-plastic hips, showed that they were equal to the new joints, and perhaps slightly better as they required less revision surgery over time. This information came from an overview of 18 different studies involving 3400 hip replacements.