Metal-on-metal stemmed hip implants should no longer be used in patients, and patients with these artificial hips should be carefully monitored, particularly young women whose hip implants have large diameter heads, according to a new study.
The study, conducted by researchers from the Universities of Bristol and Exeter, and the Centre for Hip Surgery at the Wrightingdon Hospital in Lancashire, was based on data from the National Joint Registry in England and Wales. Researchers looked at 402,051 first total hip replacements using a stemmed implant between April 2003 and September 2011. They then singled out revision operations carried out on these hip implants to determine how long it took before a revision operation was needed for each type of implant. Revision surgeries involve removing and replacing an implant that has failed and is no longer working properly.
Researchers did not include data on the DePuy ASR hip replacement system, a metal-on-metal implant that was recalled in 2010, because the devices were already known to have a much higher early failure rate than other brands of artificial hips. They also only included data on hip replacements for which there was sufficient data so that they could identify which operations were revisions of earlier hip implants. They also tried to balance the data by only considering data from surgeries on so-called “typical” patients.
Typical patients were defined as those whose hip replacements were needed because of osteoarthritis only, and who were generally healthy or with only mild illnesses at the time of the primary surgery. This allowed researchers to analyze data on 82 percent of all first total hip replacements using a stemmed implant performed in the study period.
Researchers found that metal-on-metal hip implants were used in 8 percent – or 31,171 – of first total hip replacements using a stemmed implant, and that those who received an all-metal implant were more likely that those who received another type of device to need revision surgery due to failure within five years of implantation.
Revision rates were higher in people who had a larger diameter metal-on-metal implant head. Rates were also higher among women, especially younger women.
The most common reasons for revision surgery in any type of hip implant were loosening of the implant and pain. Researchers noted that these complaints were most often made by people with metal-on-metal implants.
Source: Warwick Courier