Evolving Regulatory Expectations are Complicating Device Testing

His name may not carry the notoriety of Robert Jones, Hugh Owen Thomas, or even Sir John Charnley, but Duncan Dowson is nevertheless an orthopedic icon in his own right.
 
The former University of Leeds professor and decorated scientist who died last year at 90 is regarded as the father of biotribology and a pioneer in formulating elastohydrodyamic theory, a foundational concept used to describe the lubrication of gears, cams and bearings. That theory forms the basis for many of the analytical tools and methods Dowson created during his 70-year career, including a film thickness formula for hip joint prostheses that emanated from his 1960s-era research on total hip arthroplasty.
 
Industry pundits consider Dowson’s contributions to biotribology and elastohydrodynamic theory to be essential to the evolution of joint simulation and wear.
 
“Innovative numerial solutions for elastohydrodynamic lubrication problems pioneered by Dowson provided further insights into the mechanism of ankle, knee, and hip synovial joint lubrication,” a June 2020 editorial in lubricants stated. “Dowson investigated total joint replacement with an UHMWPE acetabular component, cushion bearing behaviour for knee and hip arthroplasty, and lubrication of total hip replacement joints created with materials of high elastic modulus…For more than 60 years, Duncan Dowson sustained invaluable contributions towards the advancement of total joint replacement prostheses.”
 
One of the most invaluable—and lasting—contributions arising from Dowson’s biotribology work was the development of knee simulators, which are used to perform wear testing of knee implants. Dowson detailed such a device for the first time in his 1977 book, “Evaluation of Artificial Joints.”
 
Simulators for knees, hips, and other joints reproduce both the active and natural motion of their respective parts to assess the kinematics and kinetics of total joint arthroplasty. The testing simulated by these devices allow researchers, product engineers, and manufacturers to evaluate the wear performance of their implants and bearing materials under physiological conditions. Such testing helps improve designs and leads to safer joint replacements.
 
ODT’s feature “Testing Complete” details the trends and market forces driving orthopedic testing and analysis. Lisa Olsen, senior vice president, Global Laboratory Services, NAMSA, was among the experts interviewed for the feature; her full input is provided in the following Q&A:  
 
Michael Barbella: Please discuss the latest trends in testing methodologies for orthopedic products.
Lisa Olsen: More and more, NAMSA is observing chemical characterization of orthopedic products. Although the biocompatibility requirements haven’t changed, regulators are looking for thorough chemical analysis of extractables. And, in some cases with devices that have coatings, more unique materials or bioabsorbable properties. These analyses are being extended to leachable and time-course studies to reveal the chemical properties over time.
 
Barbella: What are the most pressing challenges facing orthopedic device testers, and what kinds of solutions are available to them?
Olsen: As with all devices, the evolving regulatory expectations for testing approaches can be challenging. The standards are written in a broad fashion, appropriately so, to address myriads of device types. But this also means it can be difficult to prospectively understand what regulators require throughout testing.
 
Barbella: How is 3D printing/additive manufacturing impacting orthopedic device testing? 
Olsen: It puts a focus on the materials and can shift what is considered design freeze and thus, the point in development where analytical and biological testing is applied. But, as biocompatibility testing is more focused on the materials and the effects from processing, these methods are not impacted.
 
Barbella: How have new materials and technological advancements like AI impacted orthopedic device testing?
Olsen: AI can help avoid some of the efficacy testing by getting deeper and more advanced in the theoretical modelling. Then, testing can be better targeted or devices with unsuitable designs can be re-worked before going to testing. But ultimately, global regulators still have their expectations for bodies of testing that haven’t changed which simply can’t be addressed with AI.
 
Barbella: In what ways has the EU’s MDR impacted orthopedic device testing?
Olsen: The MDR is definitely causing device manufacturers to look at their portfolios to determine what products need to be retained and which may need to be discontinued because the requirements for testing have expanded. Not only that, the requirements for evaluation are now ongoing—it isn’t test it and forget it, but a program of continual evaluation is needed.
 
Barbella: How has patient-specific and customized implants impacted the testing methods for orthopedic devices?
Olsen: In many cases, patient–specific and customized implants are still leveraging a basic platform of design and materials. Testing must consider the “worst-case” use and processing scenario and then develop a plan to evaluate the safety risks. Fundamentally, it comes back to materials: they have to be well understood and this means the standard biological and chemical evaluations should be considered to determine how risks can be appropriately modelled.
 
Barbella: What strategies are being used to test orthopedic instruments, since there are no existing published guidelines for instruments?
Olsen: The horizontal guidance documents and standards for devices can still be leveraged to provide a basic direction for testing. Then, it is a matter of evaluating the device and its use to determine which risks are probable and create a test plan to look at those endpoints.
 
Barbella: How do you expect orthopedic device testing to evolve over the next 5-10 years?
Olsen: As with most devices, I think we will see in-vitro methods gain prominence as well as more chemical and materials evaluations to leverage non-animal alternatives. However, when animal safety and efficacy studies are performed, I believe we will see more efforts to leverage all of the possible data from each study.