Metal-on-Metal Hip Implants: A Closer Look

The metal-on-metal design on hip implants was first used by George McKee of Norwich England in 1953.  Following the loosening of components of the metal-on-polyethylene hip implant design, the abandoned metal-on-metal hip design was again considered.  Reportedly though, the US House of Representatives called for an investigation on metal-on-metal hip replacements.



Emerging concerns on the all-metal device began when the device gave a high failure rate.  One of the complications observed as metallosis or metal poisoning.  Symptoms associated with metallosis include soft tissue damage, inflammatory reactions, and bone loss.  Furthermore, patients may also go through hip swelling, trouble in walking and pain in the hip region.

 Grounds for investigation

According to the New York Times August 2011 issue, complaints regarding the metal-on-metal hip implants received by the US Food and Drug Administration were roughly 5,000.  The accumulated number was higher than the combined complaints of the past four years. Also published in the New York Times was the article on the dangers of metal-on-metal hip replacements entitled "Remedy Is Elusive as Metallic Hips Fail at a Fast Rate," which discussed how metal-on-metal hip implants shed debris, causing damage on the tissues around the device.  Also stated in the article, that warnings about the harm the implant may bring were given by researchers but these were not minded.

As stated in a range of reports that the Australia and United Kingdom joint registry detected a failure rate of more than 50% of the average rate of all-metal hip implants. In 2003, DePuy Orthopedics marketed the ASR XL Acetabular System and the ASR Hip Resurfacing System, with metal-on-metal hip designs. It was expected that the device will last for 15-20 years.However, recipients complain of defect-related complications within a few years after implantation.

 Materials of the implant

A metal-on-metal (MoM) implant is made out of metal--- from its ball, stem and to its shell.  Compared to the metal-on-plastic polyethylene plastic articulation, cobalt-chrome has much smaller debris particles and offers high wear resistance.  MoM hip implants are durable enough to last a long time and are suited for physically active and younger patients.

 Steps taken by authorities

The FDA is actively working in several areas to further assess the safety and effectiveness of metal-on-metal hip implants.  As an added measure, they have also asked the device manufacturers to conduct post-market surveillance studies on the all-metal hip systems. Device manufacturers, including DePuy Orthopedics, have ordered hip replacement recalls on their devices.  Patients and surgeons ought to have a closer look on the devices and report right away hip implant failure symptoms.



Reference:

depuyhiprecall-info.com/2011/10/increased-failure-rates-add-evidence-depuy-hip-lawsuit/

hipsforyou.com/historyhipreplacement.php

nytimes.com/2011/10/01/health/01hip.html?_r=3&pagewanted=all

fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/MetalonMetalHipImplants/ucm241769.htm
activejoints.com/mom.html