The new article addresses aspects related to non-clinical performance testing for patient-matched guides.

The Food and Drug Administration (FDA or the Agency), the US regulatory authority in the sphere of healthcare products, has published a guidance document dedicated to patient-matched guides to orthopedic implants. The document provides an overview of the applicable regulatory requirements as well as additional clarifications and recommendations to be considered 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 legislation and has been agreed upon with the authority in advance. 

The scope of the guidance covers, inter alia, aspects related to non-clinical performance testing. With respect to the content and format of test reports to be submitted by responsible parties, the document refers to separate guidance issued by the FDA dedicated to the non-clinical bench performance testing information to be included in premarket submissions.

Intra- and Inter-Designer Variability

First of all, the authority mentions that the patient-matched guide design process should yield reproducible results for patient data sets within individual designers and across multiple designers since high designer variability may cause patient-matched guides to misalign implants. Thus, variability testing should take place in order to ensure that the results of a design process can be reproduced. For this purpose, the authority encourages the parties responsible for medical devices to investigate intra- and inter-designer variability across representative patient data sets and designers. The scope of the aforementioned testing should address such aspects as segmentation, anatomical landmark definition, and guide creation. In particular, the authority expects medical device manufacturers to use basic instructions to ensure the designers are able to follow them. As further explained by the authority, the data sets used should be representative in the context of the patient population, while the designers participating in the assessment should represent different experience levels. All the variabilities identified in the course of such an assessment should be subjected to a rigorous analysis in order to understand their impact.

Mechanical Integrity

The scope of the guidance also covers aspects related to mechanical integrity. According to the guidance, it is important since patient-matched guides rely on geometrical specifications to align implants with the patient’s anatomy. The processes patient-matched guides are subject to during their life cycle (e.g., transportation or cleaning) could cause mechanical distortion and, consequently, affect safety and effectiveness. Thus, mechanical analysis should take place after shipping and processing in order to ensure the characteristics of the device remain intact. For this purpose, the authority recommends that the parties responsible for medical devices conduct dimensional and mechanical evaluations to assess that guide stability and strength are adequate to withstand forces associated with worst-case conditions relative to transit, cleaning/sterilization, and use in the surgical environment. Should the device be labeled for cleaning or sterilization for further use after being accidentally dropped, the appropriate testing should also include dropping to ensure the accuracy and reliability of its results. The assessment should address the worst-case scenario and be duly documented.

Debris Generation

Another important aspect addressed in the guidance relates to debris that could appear due to interaction between the medical device and surgical instrument used. Such debris could create additional concerns in terms of biocompatibility or mechanical issues. According to the guidance, the testing intended to address matters related to debris generation should cover the magnitude and type of debris that could be generated when the device is used for its intended purpose. In this respect, the authority encourages medical device manufacturers to conduct simulated use testing utilizing the specified surgical instruments under worst-case contact conditions to measure the amount, size, and shape of debris generated per ASTM F1877: Standard Practice for Characterization of Particles. The scope of the assessment should also cover biocompatibility ramifications. The manufacturers may also conduct a comparison to similar medical devices already on the market in order to assess whether the clinically justified acceptance criteria are met.

Impact Alignment Accuracy and Guide Usability

The authority also mentions that patient-matched guides are intended for aligning orthopedic implants relative to anatomical landmarks identified on pre-operative images as recommended by the orthopedic implant manufacturer, while implant misalignment can cause premature implant failure and impact patient outcomes. In order to ensure the related matters are properly addressed, the authority recommends medical device manufacturers carry out an evaluation related to usability and accuracy. As further explained by the FDA, while benchtop evaluations may be useful in early verification activities, validation of the system’s performance, including bone and soft tissue interaction, should be performed in a cadaveric model to test the “fit”, feasibility, and accuracy of the guide within the surgical workflow. 

In summary, the present FDA guidance outlines the key considerations related to patient-matched guides and describes in detail the specific testing to be conducted in order to ensure they are properly addressed. The document provides additional clarifications regarding the scope of testing to be conducted in each case and highlights the key points to be taken into account by medical device manufacturers in this respect. 

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