The new article highlights the most important aspects related to mechanical testing and the assessment of dimensional measurements.
The Food and Drug Administration (FDA or the Agency), the US regulating authority in the sphere of healthcare products, has published a guidance document dedicated to technical considerations for additive manufactured medical devices. The document is intended to provide additional clarifications regarding the applicable regulatory requirements, as well as recommendations to be considered by medical device manufacturers and other parties involved in operations with medical devices to ensure compliance thereto. The authority also mentions that provisions of the guidance are non-binding in their legal nature, nor intended to introduce new rules or requirements to be followed. Moreover, an alternative approach could be applied, provided such an approach complies with the respective legislation and has been agreed with the Agency in advance.
The present FDA guidance highlights, inter alia, the aspects related to the information the authority expects the applicants to include in premarket submissions related to medical devices manufactured with the use of 3D-printing (additive manufacturing, or AM) technologies. According to the guidance, the scope of supporting information to be provided should be determined depending on numerous factors, such as the intended use of the product in question, risks associated thereto, applicable classification rules, or regulatory framework the device is subject to. In certain cases, additional information could be required due to the specific nature of the device (e.g., for patient-matched or implantable ones). At the same time, the authority also mentions that the applicability of the specific considerations should be determined on a case-by-case basis due to the differences related to the particular additive manufacturing technologies used. However, medical device manufacturers may rely on the general rule which states that if the type of characterization or performance testing outlined in each of the sub-sections below is needed for a device made using non-AM techniques, the information should also be provided for an AM device of the same device type. Furthermore, manufacturers are also encouraged to contact the regulatory agency in case additional clarifications are needed.
The use of additive manufacturing technology provides medical device manufacturers with exceptional flexibility in creating device sizes. Consequently, this technology is often used to manufacture patient-matched medical devices. In such cases, it is important to provide physical dimensions, as standardized sizes are usually not applicable. Apart from this, the manufacturer should provide information regarding different variations, indicating specific characteristics that could be subject to changes to meet the needs of a specific patient. As it was mentioned before, technical considerations would depend on the particular additive manufacturing technology used, so the manufacturer should provide sufficient details about it as well. Since these technologies are relatively new, the authority also encourages medical device manufacturers to provide a detailed description of the manufacturing process, including post-processing. Based on this information it would be possible to determine the scope of assessment medical device should be subject to.
When providing information about the device, the manufacturer should pay special attention to its specific features due to the complexity of geometry and characteristics of the materials used. In particular, the elements of a device that are intended to be manufactured with the use of 3D-printing technology should be indicated in drawings.
In general, the testing to be applied in the case of medical devices manufactured with the use of AM technology should be the same as for similar devices manufactured ordinarily. Such testing should be performed using a final device that has already passed all the steps of the manufacturing process and represents the device that would be available to customers. Should it not be the case, the manufacturer will have to provide the appropriate justification. Apart from this, the manufacturer should consider worst-case scenarios to ensure the accuracy and reliability of testing results. Moreover, it is also necessary to justify the way the particular testing scenarios were selected.
Another important aspect related to additive manufactured medical devices is based on the specific feature of the manufacturing process itself – the build direction, which could also impact the performance of a final device. This aspect should be also taken into consideration when conducting mechanical testing. The manufacturer shall conduct testing to identify the exact extent to which the build direction impacts the properties of the device. In certain cases, the location within the build space could be important as well. Thus, the appropriate testing should be performed to identify its impact.
Based on the above, the authority emphasizes the importance of ensuring consistency in manufacturing processes. In this respect, the Agency referees the recommendations on process validation and acceptance activities.
As explained by the FDA, the way the device is oriented and placed in the build space could impact not only its mechanical properties but the dimensions as well. Hence, the authority expects manufacturers to provide information about the ranges for dimensions that would be acceptable about the intended use of the device and risks associated thereto. For this purpose, the manufacturer should measure the dimensions for several devices manufactured in ways that are different in terms of location and orientation, while to ensure the safety and quality of the devices the manufacturer should ensure consistency in manufacturing processes. In any case, each time assessing the acceptability of dimension ranges, the manufacturer should consider the way the final device will be used, as well as its technological characteristics.
The authority also mentions that since the effect of orientation can vary based on the manufacturing technology used, a baseline study of the machine/material combination used may help determine the degree to which the build orientation will affect mechanical properties, while the appropriate justification should be duly provided if necessary. Such a justification should cover the aspects related to the design, post-printing processes, and other procedures the device is subject to before it will be considered final.
In summary, the present FDA guidance outlines the most important aspects related to the information the manufacturers should provide for technical considerations depending on the particular additive manufacturing technology used. The authority also describes the approach to be applied concerning testing to be conducted to ensure the final device meets the initial specifications, as well as the general safety and performance requirements.
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