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New Factors Challenge Traditional Testing Requirements

Trevor-Gascoyne-web Kevin-Knight-Knight-Mechanical-Testing-web Gemma-Budd-Lucideon-web Brian-Choules web
Trevor Gascoyne Kevin Knight Gemma Budd Brian Choules
Orthopaedic Innovation
Centre 
Knight Mechanical 
Testing 
Lucideon MED Institute


From regulatory changes to working with new materials and technologies, several aspects of the device testing process can hold up orthopaedic device manufacturers.

Chief among device manufacturers’ frustrations is understanding the technical aspects and specific requirements of testing standards, according to device testing companies.

“Regulatory agencies give OEMs a large series of testing standards that they have to perform and show a successful test. The standards are often just guidelines. They specify the outcome you want and the approximate method for doing a test, but the actual interpretation of the standard, interpretation of the testing method and all of the finer aspects of testing are left up to the company that is performing the testing,” says Trevor Gascoyne, Manager of Clinical Research and Biomedical Engineering, Orthopaedic Innovation Centre. “OEMs say that they need to abide by these standards, show how the testing performed and show their success. At that point, they have a whole slew of questions for us. How many millions of cycles do we do? What kind of loading profiles do we need? For example, FDA requires artificially-aged polyethylene implants. That’s a suggestion of the standard, but not a requirement.”

Keeping an open and strong line of communication between your testing supplier and FDA consultant is critical to meet all of the necessary testing requirements.

Stricter government regulations can also pose problems for device manufacturers when testing their device. Gascoyne notes the increase in requests for aggressive testing for hip and knee simulator or joint wear testing, attributed to recent FDA recalls.

“FDA is proactively combatting this kind of incident for future implants, and what they want to see is the failure mechanism of a particular joint replacement,” Gascoyne says. “In the past, they would test hip and knee implants under ideal conditions in a laboratory, exactly how they were designed to run. What they found with ASR and the metal-on-metal implants was that they weren’t optimally implanted. They weren’t put in the optimal patients under standard ranges of motion.”

               

Now, according to Gascoyne, FDA is looking for exposure to more adverse, aggressive conditions and asking what happens when an implant is placed incorrectly or fails.

New materials and manufacturing methods may also pose problems for device manufacturers. Challenges with new materials lie in understanding the mechanical performance of the material, as well as which process parameters affect performance, and to what degree, according to Kevin Knight, President, Knight Mechanical Testing.

“On the plastic side, we’ve seen an increase in highly cross-linked polyethylene liners and tibial inserts that have been doped with an oxidation control substance,” Gascoyne says.

                       Knee-Simulator-Orthopaedic-Innovation-Centre-web
Recent FDA recalls have device companies performing more aggressive hip and knee (above) simulator and joint wear testing.

“Oxidation, we know from literature and past years, has been very bad for inserts. They start to shear off or delaminate and often crack inside the body, causing a lot of wear very quickly. Some companies come to us with PEEK. This is being applied to similar applications as the standard polyethylene, bearing surfaces primarily. We’ve seen some flexible bearing surfaces. Polyurethane is one of them.”

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