Use of survivorship and contact stress analyses to predict the long-term efficacy of new generation joint replacement designs. A model for FDA device evaluation.

: Long-term investigational device exemption (IDE) clinical trial evaluation, as currently monitored by the Food and Drug Administration (FDA) regulatory process, is time-consuming, burdensome, and extremely costly to the product developers and ultimately to the consumer. Thus, almost all devices introduced in the past decade have not been clinically tested; they have been introduced under a "510k" grandfather provision that does not address the safety and efficacy of the product. As a result, joint replacement devices have been sold and used with serious failure consequences for the consumer. When 10-year survivorship studies are available for specific joints that demonstrate strong evidence of favorable clinical performance with suitable supporting analysis, they can be used as a standard for comparison with newer, similar designs. Additionally, contact stress analysis of the bearing surfaces of these joint replacements can be used to determine their long-term wear characteristics under normal loading conditions and compared to retrieved devices used for 10 years or more. Devices that demonstrate a 90% survivorship over a 10-year interval and have low enough contact stresses to minimize wear failure during the same period can be used as "standard designs" to which newer designs should be compared. Using this methodology, the developers of any new device should cite the standard design that they have improved on and document an improvement in early (1 to 3 years) survivorship studies with a contact stress analysis demonstrating bearing contact stresses equal to or lower than the standard design. Any device that fails more often or wears out faster than a standard design should not be released until design modifications have proved it superior or equal to the standard designs.