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ASTM International has added a PEKK raw material standard for surgical implants to its list of some 12,000 standards.
ASTM F2820, Specification for Polyetherketoneketone (PEKK) Polymers for Surgical Implant Applications, can be used for quality control by resin manufacturers as well as a guide for developing master files and test data for OEMs and regulatory agencies. Companies that implement the new standard could also benefit from easier regulatory approval.
“This is of particular importance in permanent implant applications, where failure can lead to additional surgical procedures and potentially harm the patient,” says Jon Moseley, Ph.D., Director of Implant Technology at Wright Medical Technology and chairman of F04.11, the ASTM subcommittee that passed the standard. “In addition, using materials that meet the requirements of ASTM F2820 can reduce or eliminate the need for animal testing for these materials.”
A deeper discussion on the standard follows.
What was the reasoning behind development of a new standard?
Jon Moseley, Ph.D.: The material covered by the new standard is a high performance engineering polymer that is being used for long-term implantable medical devices such as cages for spine fusion. These devices undergo rigorous testing before being approved for use in humans, but those tests are usually carried out on devices made from only two or three lots of polymer. Standardization of critical chemical, physical and mechanical properties is one way to help ensure that equal or higher quality materials are used in the devices that are actually used in the clinic.
What does the new standard cover?
Moseley: It covers the requirements for poly(ether ketone ketone) (PEKK) polymers intended for use in implantable medical devices, and it has requirements for both the virgin resin and for fabricated forms. It includes requirements for chemical, physical and mechanical properties.
The standard describes two types of PEKK resins based on the use of different ratios of the two isomeric forms of the EKK monomer. This results in different thermal and mechanical properties which are accounted for in the requirements.
How does the new standard benefit orthopaedic device manufacturers and suppliers?
Moseley: Orthopaedic device manufacturers benefit in several ways. Using materials that meet the standard is an important part of consistently producing high quality products. If your raw material is variable, then the final product is also going to be inconsistent, which could obviously have unacceptable consequences in an implantable device.
Using materials that meet the standard will also reduce the amount of testing needed to obtain approval to market a new device. Regulatory agencies recognize the value of using standardized materials that already have a proven record of clinical use, because it reduces the number of unknowns when they are evaluating a new device for safety and efficacy. Furthermore, scientists and engineers from agencies such as FDA take an active role in the development of medical device standards.
The standard will also be used by manufacturers and suppliers to set internal specifications for their products. This is especially helpful for suppliers, because specifications based on a recognized standard tend to be more consistent, which reduces the need for them to conduct special tests for a single customer.
What will manufacturers and suppliers need to do to comply with the new standard?
Moseley: Suppliers of PEKK resins will have to perform testing to verify the identity and purity of the polymer; to show that physical properties such as density, melting point and glass transition temperature are within narrow limits; and that mechanical properties such as tensile and impact strength meet specifications when the resin is fabricated into standard test specimens.
Manufacturers of medical devices will also have to show that their products still meet the physical and mechanical requirements of the standard after all process steps have been completed. Testing has to be performed on the final device (or on test specimens fabricated according to identical methods), because each process step has the potential to adversely affect the material. For example, gamma or e-beam radiation is frequently used to terminally sterilize medical devices, and ionizing radiation can cause degradation in many polymers.
In addition to setting requirements for the properties of PEKK, F2820 also stipulates that both the resin and fabricated forms should be manufactured under a certified Quality Management System.
What else should orthopaedic manufacturers and suppliers know about ASTM F2820?
Moseley: All standards should be considered as works in progress, and this is especially true of new standards. Subcommittee F04.11 welcomes feedback and participation in the ongoing effort to improve the quality and usefulness of the standards under its jurisdiction.
Jon Moseley, Ph.D., earned degrees in chemical and biomedical engineering and has worked in the medical device industry for more than 20 years. He is the Director of Implant Technology for Wright Medical Technology, an orthopaedics company located in Arlington, Tennessee. He also serves as chairman for ASTM subcommittee F04.11 on polymeric materials for surgical and medical devices.
