Metal-o-metal (MoM) hip implant devices from all manufacturers have been under scrutiny because of a higher than expected early failure rate. But what does that mean? What is causing these hip implants to fail?
On June 27th and 28th of this year, the FDA had an open hearing on Orthopedic Rehabilitation Devices in which doctors, patients and device manufacturers gathered to voice their concerns and opinions on the success and failures on metal-on-metal hips.
On the first day of the conference, Two PhD University Professors, as well as Industry Representatives from hip implant manufacturers Smith & Nephew and Corin USA spoke on the topic “MoM”Device Mechanics /Failure Modes”
According Steven M. Kurtz, PhD of Drexel University the top causes of MoM hip failure were:
- Thinning of the neck of the device, femoral loosening and neck fractures
- Wear and elevated wear — Some MoM components experienced greater wear than was expected based on simulator studies.
- Absorption of black deposits on tapers at time of revision
- Edgewear- greater than expected wear around the edge of the device
Jeremy L. Gilbert, PHD of Syracuse University detailed more types of corrosion.
- Tribocorrosion – combination of wear and corrosion
- Fretting corrosion — wear and corrosion in which the corrosion rate is enhanced by a small oscillation between two meeting surfaces. This can lead to metal toxicity in a cobalt chromium hip replacement
- Stress Corrosion cracking, or stress enhanced corrosion — corrosion enhanced by stresses put on the device
Mark. H. Gonzalez, MD, Chairman of Orthopedic Surgery at the University of Illinois spoke on behalf of Device Manufacturer Corin USA, — He also stated that fretting and corrosion of the head and or neck of the device is one cause of the device failure. He suspects that the corrosion may have something to do with the component positioning and edge loading. Increased wear may linked to increased ion levels on the blood. He also touched on femoral neck fractures.
As sort of a defense to the hip prosthesis, Dr. Gonzalez advised that clinical outcomes of Mom Arthoplasty depend on:
- Implant Selection
- Patient Selection
- Surgical Technique
Clearly, not all patients are good candidates for a metal on metal hip replacement. The success of the hip replacement can also vary based upon the surgeon.
Smith & Nephew has one MoM hip device that is approved in the United States: The Birmingham Hip Resurfacing Device. The reported causes of failure for this device have been:
- Femoral neck fracture
- Femoral neck collapse
- Femoral head collapse
- Avascular necrosis
- Alignment of acetabular and femoral devices
Everyone’s body responds to a device differently. If you experienced pain after a hip replacement or an early failure of a hip implant, you should talk to your orthopedic surgeon to get the best explanation on what caused your specific device to fail.
Related Topics: Metal on Metal Hip Implant Lawsuits