An estimated one-fifth to one-third of patients who have received a metal-on-metal hip replacement system made by Johnson & Johnson subsidiary DePuy Orthopaedics have had the devices fail them, according to the National Joint Registry for England and Wales. The report suggests the problem with the artificial hips is even greater than first expected.
The United States does not have an established registry for replacement joints, but reports to the Food and Drug Administration (FDA) have also indicated the DePuy artificial hips were failing at a higher than expected rate. The hip implants were recalled last fall, affecting an estimated 93,000 people worldwide.
Most hip implants are made of a combination of metal and plastic or ceramic. The DePuy implant was made with a metal ball and metal socket, presumably to be more durable. It was approved for use in the United States in 2006 through an expedited approval process granted to devices that are similar to ones already approved for use.
About 12 percent of hip implants made from a combination of materials fail over about 15 years. Concerns were raised with DePuy implants when early reports showed that the same percentage were failing after just five years. The British registry shows that over time, DePuy’s failure rate is rising.
The report followed 2,100 patients who received the DePuy metal-on-metal device. About 29 percent of patients who received the device six years ago had to have their implants replaced. Seventeen percent of patients who received the devices five years ago have had them replaced; however, that number could rise over the next year.
The source of the problem may be the materials used to make them stronger than other implants. When the metal parts rub together, small bits of metal may fall into the joint space causing irritation and inflammation. This swelling can wear on the implant and could cause it to loosen, dislocate or fracture. These complications usually require revision surgery to remove and replace the system. The patients who have problems are disabled, in pain, and could suffer even more complications from additional surgeries.
Concerns about the metal-on-metal devices have led the FDA to order a review of all metal-on-metal hip replacement systems. A report is expected soon.
Source: NY Times