FDA announced in January that it intends to require filing of a PMA or a notice of completion of a product development protocol for two types of metal-on-metal replacement hips with cemented and uncemented acetabular components. In a Federal Register notice the agency summarized its proposed findings on the degree of risk of illness or injury to be eliminated or reduced by requiring the devices to meet PMA requirements.
The notice said FDA originally classified the metal-on-metal hip systems as Class 3 because insufficient information existed to support a conclusion that performance standards or general controls would provide reasonable assurance of device safety and effectiveness. Further, it said, concerns expressed at a 2001 meeting of the Orthopedic and Rehabilitation Devices Panel are still relevant today.
“Current wear testing methods for metal/metal bearings are limited, and importantly can underestimate bearing wear by an order of magnitude compared to clinical outcomes,” the notice said. “There are also no standardized wear methods or consensus among researchers for investigating joint microseparation, dislocation, cup deformation, demanding gait activities and third-body abrasion. In addition, there is a lack of wear measurements from retrieved metal/metal bearings, so it is a challenge to correlate wear rates from modern devices to adverse events demonstrated clinically like pseudotumors. To complicate matters further, metal/metal bearings have shown unpredictable wear trends in simulator testing, which have not been explained. Therefore, it is a challenge to introduce sufficient special controls to mitigate the risks of modern metal/metal hip devices.”
Meanwhile, the agency also issued a new safety communication on metal-on-metal hip implants with recommendations for surgeons on evaluating patients, soft image testing, and metal ion testing. The new guidelines are based on the agency’s current assessment of metal-on-metal hip implants, including benefits and risks, evaluation of published literature, and the results of an Orthopedic and Rehabilitation Devices Advisory Panel meeting, last summer.
The guidelines advise surgeons to select a metal-on-metal implant for patients only after determining that the benefit/risk profile of using such an implant outweighs that of using an alternative hip system. They also are advised to regularly evaluate symptomatic patients at least every six months and asymptomatic patients every year or two. There also are recommendations on soft tissue imaging and metal ion testing for symptomatic and asymptomatic patients.
Editors note: If you have more questions about building an FDA friendly PMA, consider attending our upcoming conference Success in Pre-clinical studies and Clinical Trials [4], on Thursday, February 14, at MD&M West, Anaheim.
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