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. Michael Coladonato, senior regulatory specialist, and Lisa Ferrara, Ph.D., technical director, Element Materials Technology, were among the experts interviewed for the feature; their full input is provided in the following Q&A:   
 
Michael Barbella: Please discuss the latest trends in testing methodologies for orthopedic products.
Michael Coladonato and Lisa Ferrara: The latest trends in testing methodologies for orthopedic products involve the development of a comprehensive battery of tests that evaluate medical products as an entire “system.” Implementing testing to evaluate how the implant performs is one part of the assessment. However, it is vital to evaluate how the implant integrates and functions with the other components that accompany the medical device, such as the instruments, the surgical approach, potential software, and the biological environment. This changes the way the testing and evaluation should be approached. Assessment of each discrete unit within the system must be analyzed, as well as evaluation of the system as a whole.
 
Barbella: How has patient-specific and customized implants impacted the testing methods for orthopedic devices?
Coladonato and Ferrara: Patient-specific and customized implants are beginning to have greater market presence. Medical facilities are working towards implementing the printing of implants in the clinical setting. This would allow the physician to virtually pre-plan the surgery and further tailor the implant to the patient’s anatomy with refinement of the anatomical placement and fit. The ability to print patient-specific implants in the clinical setting requires a collaborative effort involving the manufacturers of the printers, quality specialists, design and test engineers, regulatory specialists, medical staff, and surgeons to evaluate multiple facets of the printing process and device designs to ensure the safety of printed devices and altered designs.  
 
Barbella: How is 3D printing/additive manufacturing impacting orthopedic device testing? 
Coladonato and Ferrara: The 3D printing of implants and tooling have grown at an exponential rate over the last few years. There is significant market appeal with the ability to print complex designs and open architectures that allow for tissue ingrowth, thus creating a potential for improved healing.  
The ability to rapidly print prototypes and production parts have revolutionized orthopedic implants. Multiple manufacturers have expanded their business by adding printing capabilities, resulting in the rapid growth for additively manufactured orthopedic devices. However, the validation of additive manufacturing for implants must address the manufacturing processes and risks for the Quality System, which would include the testing of every lot, as well as the necessary testing needed to fulfill regulatory requirements.  
 
Barbella: What are the most pressing challenges facing orthopedic device testers, and what kinds of solutions are available to them?
Coladonato and Ferrara: Keeping up with the pace of new and novel technologies where the test standards need to be slightly modified to accurately assess the nuances of novel orthopedic devices. The medical device industry is rapidly changing, therefore orthopedic device testers must adapt quickly and effectively in order to provide appropriate test strategies that both meet regulatory requirements while taking into consideration the nuances of novel medical devices.
 
Barbella: How have new materials and technological advancements like AI impacted orthopedic device testing?
Coladonato and Ferrara: Artificial Intelligence (AI) has entered into the medical device arena with multiple opportunities for improving diagnostics and treatment processes. It will provide intelligent systems that can learn and provide faster diagnostic and treatment options specific to each patient, while monitoring the patient’s treatment compliance. AI will be the catapult for customized medicine. The challenge lies in the testing and evaluation of AI’s safety, efficacy, accuracy, cybersecurity, and learning capabilities. Therefore, each application that will incorporate AI will most likely require customized pre-clinical and clinical evaluation strategies specific to the technology at hand. Assessment of the cumulative system that incorporates AI will require detailed risk assessment and mitigation plans with an evaluation of the system in the manner it is intended to function, as well as how the system can fail. Assessment of safety and efficacy, as well as cybersecurity, compliance, and risk will require in-depth detailed test plans.
 
Barbella: What strategies are being used to test orthopedic instruments, since there are no existing published guidelines for instruments?
Coladonato and Ferrara: Strategies to assess the integration of the instrument with the implant, the tissue environment and placement, the strength and durability are all factors to take into account when testing orthopedic instruments. The most common test strategy utilized for orthopedic instruments is usability testing coupled with a risk-based biocompatibility assessment. This approach can allow for the most accurate assessment of the instruments with respect to safety and effectiveness.
 
Barbella: In what ways has the EU’s MDR impacted orthopedic device testing?
Coladonato and Ferrara: The EU MDR includes the General Safety and Performance Requirements (GSPRs), which have replaced the MDD Essential Requirements. Non-clinical testing is critical in supporting CE marking and compliance to the GSPRs. The EU MDD lists mandatory standards (harmonized standards) for non-clinical testing, a similar list is available for the EU MDR, however, the EU MDR list of standards is more comprehensive and notified bodies require manufacturers to begin using the latest version of the applicable standards one year following the standard being published.