A new kind of hip replacement – that's supposed to last years longer than the standard type – is being recalled by another manufacturer, while the U.S. Food and Drug Administration plans to review how safe the devices are for patients.

One of the manufacturers of the devices, British-based Smith & Nephew, recently recalled a liner used in so called metal-on-metal hip replacements. The company said in a statement that it was "not satisfied with the clinical results" it was seeing.

It’s the fourth company to recall or suspend sales of the implants, which were introduced in the mid-2000s and billed as a more durable option compared to the traditional metal-and-plastic type.

But compared to standard hip replacements, research studies have suggested that those using a metal ball and a metal cup are more than three times more likely to fail, and can cause tissue damage around the joint.

Health authorities concerned

After approving the metal devices for use around the world, government watchdogs have been taking a second look at them.


Richard Stone holds an X-ray of his pelvis and prosthetic hip, in Palm Beach, Fla. (Steve Mitchell/Associated Press)

In April, Health Canada issued a safety advisory saying that metal-on-metal implants can cause pain, "soft tissue reactions," and that the implants can become loose.

Patients with the implants who have painful hips and an MRI showing tissue damage should have the devices removed, the agency said. And all patients with metal-on-metal hips, even if they have no symptoms, should be monitored by their surgeons.

South of the border, the U.S. Food and Drug Administration has said that it has "concerns" about the devices, cautioning that the metal ball and metal cup slide against each other so that "some tiny metal particles may wear off of the device and enter into the space around the implant," and that the metal particles "may even get into the bloodstream."

Later this month, the FDA plans to review how safe the devices are for patients. A public meeting is set for June 27 and 28, where the agency said will seek expert opinions on "the risks and benefits" of the devices, based on the available science.

Canadians affected

Thousands of patients in Canada have had a metal-on-metal hip replacement since they were introduced. Some have since had them removed. For many others they've become a source of worry.

Frank Cristo underwent the procedure five years ago, but he said the pain he had been experiencing only got worse so he had the implant removed and is waiting to have it

'I was good for the first month or so, then I started feeling pain all the time.' —Frank Cristo, hip-replacement patient

replaced with the metal-and-plastic type.

"I was told metal-on-metal was supposed to be the best," he said. "I was good for the first month or so then I started feeling pain all the time."

Cristo isn’t alone. About one in 100 patients experience inflammation and pain. Canadian research suggests a smaller number develop something called pseudo tumors that cause serious muscle and tissue damage.

And the number of people complaining of problems related to a metal-on-metal hip replacement is on the rise in Canada, according to  Dr. Nizar Mahomed, the head of orthopaedic surgery at Toronto Western Hospital.

"We are just starting to see the increased numbers of revisions or failures in the metal to metal prosthesis," he said. "I hope that it stabilizes, but there are still concerns that the number of failures will continue to increase with time."

Role of health authorities questioned

A recent study of 22 Canadian patients with metal-on-metal implants found that the devices failed in two of the cases.

Dr. Ross Leighton, who helped conduct the study and is a former president of the Canadian Orthopaedic Association, believes there weren't enough independent studies of this type of implant before they were approved.

"It really comes down to Health Canada really having enough stringent criteria before they bring out a new component," he said.

Health Canada says its approval requirements are among the most stringent in the world.

Companies that manufacture the metal devices say they continue to make and improve on them.

With files from CBC’s Pauline Dakin