Regulators in the UK have launched an investigation to find out if people who have had metal-on-metal hip implants are at a higher risk of developing dementia or heart problems due to a defect in the design.
The report follows a medical device alert announced by the Medicines and Healthcare products Regulatory Agency (MHRA) last month that now recommends more than 50,000 people in the UK who received metal-on-metal hip replacements undergo additional tests.
A representative from the agency also revealed to The Times that the MHRA is looking into whether those patients have also suffered problems with their heart, cognition, or memory.
The components of metal-on-metal implants can rub against one another, releasing small metal ions into the bloodstream and causing metal poisoning. According to Dr. Neil McGuire, clinical director of medical devices at the MHRA, the metal used in many hip implant components may be toxic in high doses. The agency wants to find out if there’s a problem and what should be done about it.
“It may turn out that we’re chasing smoke, but it may not,” McGuire said. “If we do find something we’re not going to keep quiet about it.”
Finding the actual connection has been difficult for the agency since the heart and cognitive issues often arise around the same age that people get implants.
“We’re always balancing depriving people of the benefits of these devices versus protecting people from harm,” he said. “We don’t want to set a lot of hares running if there’s nothing to find.
“It may be at the end of it we say, ‘There’s nothing to see here folks.’ ”
Studies Connect Metal Hip Implants with Cognitive Issues
A study published in January in the journal BMC Psychiatry explored the possibility of a connection between defective hip implants and cognitive problems. The researchers looked at 10 cases in which patients were implanted with the now-recalled ASR total hip replacement and evaluated neuropsychiatric morbidity.
In the nine patients who had toxic levels of chromium or cobalt in their blood from the implants, nine suffered from depression with three receiving treatment. Seven also showed short-term memory problems.
In one case, a then 52-year-old man underwent a complete ASR total hip replacement on his left side before needing revision surgery six years later. During that time, he had high levels of chrome and cobalt in his blood. He also complained of chronic pain, social withdrawal, poor sleep and concentration, short-term memory loss and more.
The researchers concluded that clinicians should be aware of potential cognitive problems after metal-on-metal hip implants and look for any issues.
In 2016, scientists also conducted a study that looked at whether patients with metal hips had a higher risk of heart failure. Published in the journal Acta Orthopaedica, the study concluded that men with a metal-on-metal hip implant had a higher rate of hospitalization for heart failure than men with a metal-on-polyethylene implant.
Scope of Metal-on-Metal Hips Metal Poisoning Unclear
According to some experts, it is unclear just how widespread the problem of metal poisoning as a result of metal-on-metal hips actually is. Mark Wilkinson, a professor at the University of Sheffield, said that only 30 cases of metal poisoning have been confirmed from the millions of metal-on-metal implants worldwide.
“There doesn’t seem to be any clear evidence so far that the group with reasonably functioning prostheses is going to have any significant risk of heart or brain problems,” he told The Times. “It’s not that people aren’t looking: there is a large amount of research, but there’s no convincing evidence. There isn’t that epidemic of systemic effects.”
In the meantime, everyone who has received a metal-on-metal hip implant in the UK is urged to see their physician for regular follow-ups to determine whether they may be suffering from metal poisoning, even if they are not exhibiting symptoms.