Pharmaceutical

More problems with metal-on-metal hip implants expected

Patients who have metal-on-metal hip implants should have regular checkups to ensure their device is working properly and that it isn’t poisoning their blood with heavy metals. The warning comes after a recent English study found metal-on-metal hip implants were failing at three times the rate of more traditional metal-on-plastic or metal-on-ceramic devices.

Over the past decade, materials used to make hip resurfacing and total hip replacement systems have expanded to include metal-on-metal parts, meaning that both the ball and socket that fit into and move against each other are made of metal. The design was intended to be more durable.

About 21 prosthetics manufacturers make metal-on-metal implants, including DePuy Orthopaedics, a subsidiary of Johnson & Johnson.

While the intention was good – to make a device that would last longer than traditional ceramic or plastic devices – the design was flawed. This became apparent after reports of problems with the metal-on-metal devices began piling up. What doctors soon realized is that when the metal parts of the implant rub together, it may cause fragments of metal to fall into the joint space. This can cause inflammation that accelerates the failure of the devices. But it may also lead to a new problem. As the heavy metals are leached into the bloodstream, it can cause a type of blood poisoning known as metallosis.

Metallosis can cause headaches and fatigue. But the real damage from the condition may not be realized for years.

Recently, the Food and Drug Administration (FDA) made a stunning announcement – that it would be reviewing all the metal-on-metal implants that have been approved for use in the United States. Manufacturers were asked to conduct studies on their devices and to report any problems, including cases of heavy metals in the blood.

An estimated 500,000 people in the United States have received metal-on-metal hips over the past decade, yet only a relative few have come forward with problems. Studies suggest that number will likely increase in the years to come, and that tissue destruction is likely occurring without patients’ knowledge.

Source: The Seattle Times