- wear of the polyethylene component and
- early periprosthetic fracture.
A regulatory report released in England states:
Detailed analysis of data from the England and Wales National Joint Registry (NJR) has shown that the mobile bearing variant of the Preservation unicompartmental knee system has a higher than expected early revision rate compared to other unicompartmental knee systems used in England and Wales. Of 264 DePuy Preservation unicompartmental mobile bearing knee implants recorded on the NJR database between 01/04/2003 and 18/11/2008, 34 (12.9%) of these have been revised (as of July 2009).
The exact cause for the high revision rate is not known but is likely to be multifactorial. Failure modes reported to date include: loosening, pain, wear of the polyethylene component and early periprosthetic fracture.
In light of this and after continuing analysis by the manufacturer, DePuy has now ceased actively promoting the mobile bearing variant of this knee system in the UK and has confirmed to the MHRA that it will be discontinued throughout Europe from August 2009.