Faulty hips may mean surgery

Many New Zealanders may need invasive surgery after a recent global recall of hip implants.

The Smith & Nephew R3 hip implants were recalled after usually high rates of replacement surgery were required in Australia and the United Kingdom. In New Zealand, 139 of the devices have been implanted.

According to the New Zealand Orthopaedic Association, more than 25 per cent of patients had replacement surgery when a similar recall of 525 DePuy ASR hip implants was issued in 2010.

Another recall in April involved 41 Stryker MITCH hip implants.

Ministry of Health senior media advisor Kevin McCarthy said Smith & Nephew had finished contacting surgeons to alert them of the recall.

"They should have been all contacted by Wednesday last week."

Medsafe head of compliance management Derek Fitzgerald confirmed the action.

"The company sent out a notice to all of the surgeons involved and all of the hospitals that were supplied product.

"We know that all of the hospitals have acknowledged receipt of the letter."

Fitzgerald said the expectation was that surgeons would contact affected patients to inform them about the recall.

Smith & Nephew said there was no single reason why their implant was not working as well as expected.

Fitzgerald said there were various reasons for implant revision or replacement.

"The reasons for these sorts of products to be replaced are things like dislocation, loosening of the various parts, infection, pain."

Smith & Nephew said that fractures were another cause of replacement.

According to the New Zealand Orthopaedic Association, microscopic amounts of metal can be worn away in this type of implant. That debris was made up of cobalt and chromium, two metals which were usually needed in small amounts. This problem caused the recall of Stryker implants.

The metal could enter the tissues around the implant, causing swelling and pain. The patient may require an operation to investigate the swelling and possibly replace the implant.

The US Food and Drug Administration warned that replacements carried the standard risks of surgery. They included reaction to anaesthesia, infection, bleeding and blood clots.

The replacement may also be more difficult if there had been a local reaction to the implant.

There were also concerns about cobalt poisoning if there was more than 1 milligram of metal debris per litre of blood, or about the size of five grains of sand.

Cobalt is needed for absorption of vitamin C and B12. Too little reduces production of red blood cells, which can cause anaemia.

Too much chromium can also cause problems. Chromium helps regulate blood sugar levels, but more than about 2.5 grains of sand is grounds for caution.

Fitzgerald said Medsafe would keep a watch on metal-on-metal implants and the actions of overseas medical device regulators.

He said New Zealand currently had no approval process for medical devices.

"They're allowed to be just put onto the market, but they can be taken off if they're not satisfactory.

"We just have what's known as a listing process, unlike other regulators overseas, like Australia, Europe and America where devices have to first be assessed in some way."

He said the medical device safety legislation is very old, but steps are being taken to fix this.

"We are forming a joint agency with the Australian regulator."

The joint Australia New Zealand Therapeutic Products Agency is expected to replace Medsafe within five years.