The new article describes in detail the matters related to MR compatibility and also provides a brief overview of non-clinical testing and the way it should be conducted.

The Food and Drug Administration (FDA or the Agency), the US regulating authority in the sphere of healthcare products, has published draft guidance dedicated to orthopedic non-spinal bone plates, screws, and washers in the context of premarket notification (510(k)) submissions. Once finalized, the guidance will provide an overview of the applicable regulatory requirements, as well as additional clarifications and recommendations to be taken into consideration by medical device manufacturers and other parties involved in order to ensure compliance. At the same time, provisions of the guidance are non-binding in their legal nature and are not intended to introduce new rules or impose new obligations. Moreover, the authority explicitly states that an alternative approach could be applied, provided such an approach is in line with the existing regulatory framework and has been agreed upon with the authority in advance. 

The document highlights the key points related to the specific aspects to be addressed in the submissions and outlines the scope of information the authority expects the applicants to submit.

MR Compatibility

First of all, the document outlines potential risks associated with magnetic resonance (MR) compatibility for the products covered by the scope of the guidance. The risks include:

  • Movement of the implant, resulting in tissue damage or displacement of the device;
  • Heating of the tissue surrounding the implant and subsequent tissue damage; and/or
  • Image artifacts that may render the MR images uninterpretable or misleading. 

The authority expects medical device manufacturers to make sure the issues related to MR compatibility are properly addressed in order to ensure the effectiveness of the device as well as the safety of patients. In this respect, the document refers to a guidance document dedicated to testing and labeling medical devices for safety in the MR environment.

Non-Clinical Testing: Key Points

The scope of the guidance covers, inter alia, aspects related to non-clinical testing. Under the general rule, the information included in 510(k) submissions should cover  aspects related to the fixation of a fracture site – in particular, it should be demonstrated that it is substantially equivalent. Thus, the authority encourages medical device manufacturers to perform the appropriate testing intended to evaluate the actual performance characteristics of the product in question. The authority also mentions that if a plate, screw, or washer system is indicated for use in multiple anatomical locations or if the system encompasses a large variety of device designs, there may be more than one worst-case device that should be supported with mechanical performance data. 

As further explained by the authority, the minimum acceptable sample size for bench testing is 5 units. Should any additional issues be identified or reasonably forced, a larger sample size could be needed. 

With respect to the specific aspects related to bench performance testing and reporting associated with it, the authority refers to a separate guidance document dedicated to the matter. The authority also mentions that medical device manufacturers may make references to the applicable voluntary consensus standards in order to demonstrate compliance with the respective regulatory requirements the products are subject to. In such a case, the submission should include all necessary information and documentation as prescribed by the applicable standard. Furthermore, the manufacturers are encouraged to provide detailed enough side-by-side comparisons to similar medical devices already on the market and cleared for the same intended use. 

The guidance further describes the scope of mechanical performance testing to be conducted, as well as applicable testing endpoints. In this respect, the authority mentions that when a plating system’s overall construct and plate designs are similar to the identified predicate, individual analysis of the worst-case plate and screw components as listed below may be sufficient to establish the substantial equivalence of the construct; when the overall construct differs in fixation method or raises concerns about strength or stability at the fracture site, additional construct evaluations such as bench testing or in vivo data may be needed to demonstrate substantial equivalence. Moreover, based on the comparison to a predicate device, a need for additional testing endpoints could be identified. For products comprised of polymers, additional performance testing could be required to assess the characteristics of the components thereof when used for the intended purpose. All the testing should cover the worst-case scenario to ensure the accuracy and reliability of its results. 

The authority also mentions that submissions for devices made of anisotropic materials should address the shear strength of the devices and the risk of crack propagation through additional testing and/or scientific justification. Special considerations would apply depending on the nature of the device and the materials it is comprised of. For instance, in the case of a medical device containing fibers, the parameters subject to a rigorous assessment would include the percent fiber used, length of fibers, fiber direction, and sizing agent since these factors could significantly impact the safety and performance of the device. 

In summary, the present FDA guidance provides additional clarifications regarding MR compatibility matters and also describes the approach to be applied with respect to non-clinical testing. The document outlines the scope of such testing and highlights the most important aspects to be addressed.

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