Safety Alert Or Field Safety Notices for ABG I Uncemented Acetabular Cups for Total Hip Replacement

Safety alert / Field Safety Notice

MDA/2004/011

CON008577

2004-03-02

United Kingdom

MHRA

https://webarchive.nationalarchives.gov.uk/20141206095400/http://www.mhra.gov.uk/PrintPreview/PublicationSP/CON008577

Cup wear and asymptomatic acetabular osteolysis. six hospitals in the uk have informed mhra of poor results and high revision rates associated with abg i acetabular cups. failure modes reported to date include: increased wear of the ultra-high molecular weight polyethylene (uhmwpe) acetabular cup liner sever, asymptomatic peri-acetabular osteolysis cup loosening which in severe cases has led to cup migration into the pelvis. mhra is also aware of two uk clinical centres with 'kaplan meier survivorship curves' demonstrating abg i cup survivorship of 90+% at ten years, i.E. less than 10% of the acetabular cups had been revised after ten years. the scandinavian joint registries report similar results associated with this product. currently available worldwide literature reports both good and poor abg i cup performance. mhra, in co-operation with stryker uk, has co-ordinated a detailed audit of clinical notes and x-rays at three uk hospitals (two reporting poor results and one reporting good results) to determine the reasons for the mixed performance in the uk. using two orthopaedic experts' opinion that a cup should 'definitely' or 'probably' be revised as an endpoint, the implant survivorship for all 340 of the abg i cups reviewed during this audit was 100% at three years and 82.5% at ten years. no one factor could be identified as the initiating factor for higher than anticipated polyethylene wear and poor cup performance (see appendix for further details). although the reason for the variation in performance of abg i cups is unclear, the mhra audit demonstrated that unacceptable revision rates have been observed at some uk clinical centres. as the failure mode is asymptomatic, mhra recommends that all patients implanted with abg i cups are identified and, where necessary, recalled for clinical and radiological review. all patients with abg i cups should be reviewed regularly to ensure patients requiring revision are identified at the earliest opportunity. in all cases the benefit of radiographic examination should be weighed against the risks from radiation exposure on an individual bases, in line with the requirements of ir(me)r 2000 1 . this medical device alert has been distributed to gps for information, in the event that any of their patients have received an abg i acetabular cup. references 1 . si 2000 no 1059. the ionising radiation (medical exposure) regulations 2000.

Identify patients who have received ABG I acetabular cups. Where the identified patients are already undergoing annual review, including radiographic examination, continue to monitor their progress. Where the identified patients are not currently undergoing annual review, recall them for clinical assessment, including radiographic examination, on an annual basis. Radiographic examination should include both A-P and lateral X-rays. Look for evidence of acetabular osteolysis. Where the extent of osteolysis, if present, is unclear from X-rays, consider further investigation using CT.