The MHRA has received reports of higher than anticipated rates of revision for ASRTM acetabular cups.
Subsequent to the publication of the MHRA’s Medical Device Alert MDA/2010/033 for metal-on-metal hip replacements on 22 April 2010, the National Joint Registry (NJR) of England and Wales informed the MHRA that ASRTM acetabular cups had been identified from registry data as having higher than anticipated rates of revision in hip resurfacing and total hip replacement procedures (see Appendix). The MHRA has also received similar reports from two of the 257 clinical centres in the UK that have implanted these devices.
DePuy produces two different instruction documents for this device: the instructions for use (IFU) supplied with the device, and the surgical technique manual. A cup inclination angle of 45º is recommended for reaming and implantation in all versions of the surgical technique manual. However, the original IFU did not contain reference to specific cup placement angles. Based on post-market experience, in October 2008, the manufacturer added to its IFU (Revision C) a recommended cup inclination angle of between 40º and 45º and distributed a document entitled ‘The importance of correct acetabular component positioning’ highlighting the importance of cup angles to implanting surgeons from February 2009.
All users were informed of correct cup angles in the manufacturer’s Field Safety Notice of 8 March 2010. The FSN did not recommend any additional follow-up for patients in the absence of symptoms. However, the performance of devices implanted outside the manufacturer’s currently recommended angle range (40º– 45º) is not known.
DePuy ASRTM acetabular cups have been in clinical use in the UK since 2003.