Defective metal-on-metal hip replacement systems can cause patients debilitating problems for years after the implants have been replaced, according to research presented at the annual meeting of the American Academy of Orthopaedic Surgeons this week.
Surgeons have learned over the past decade that newer versions of hip implants, made with a metal ball that fits into a metal socket, have been failing at a higher rate than traditional hip implants made of ceramic or plastic parts. Typically, most hip implants fracture, loosen, or dislocate over a decade or two due to wear and tear. But many of these metal implants, designed to be more durable than traditional implants, are failing after five years or less.
When artificial hips fail, they cause pain and disability, and need to be replaced.
This premature failure of all-metal implants baffled doctors, until they cut open patients and noticed a startling trend. The joint space was often inflamed and discolored by tissue death. They suspect the problem occurs when the metal parts of the implant rub together and debris breaks off and falls into the joint space, causing the implants to fail faster, but also allowing cobalt and chromium to leech into the bloodstream. This causes a type of blood poisoning known as metallosis, which can affect the heart and nervous system.
The new research also found that a third of patients in a Netherlands study on metal hips experienced adverse reactions in soft tissue; a quarter of patients in an English study had revision surgery after experiencing worsening symptoms, and a third of those required additional surgery because of “disease progression.”
The study indicated that 98 percent of cups and 93 percent of balls from metal implants showed “moderate to severe scratching” in 46 retrieved metal-on-metal implants.
Increasing complaints about metal-on-metal hip implants ultimately led the Food and Drug Administration (FDA) in 2010 to order 21 manufacturers to conduct studies on patients who have received the implants. The agency will use this information to determine what measures need to be taken with the devices.
Source: USA Today