by Dr. Jack E. Lemons

ASTM Committee F04 on Medical and Surgical Materials and Devices has been creating standards for this field since 1962. Dr. Jack Lemons provides a quick overview of the past, present, and future of this committee.

Risk Factors: A Changing World

On a worldwide basis, public health care is rapidly evolving. Central to the population at large, life and death considerations are paralleled by concerns about quality of life—especially in developed countries. Within investigations about enhanced quality of life, risk factors associated with surgical reconstruction of the musculoskeletal system have been a point of ongoing discussion. In part, outcomes have been assessed specific to the longer-term (greater than 10-year) stabilities of the synthetic devices that achieve these reconstructions. These stabilities are needed for minimizing pain and maintaining normal functional activities (for example, aesthetics, ambulation, mastication, etc.). In this regard, it has been recognized that risk factors related to orthopedic devices continue to increase. Today’s population exhibits contradictory trends that highlight the stresses on orthopedic devices: we are much more active through involvement in sports, are living longer, but on the average are becoming more overweight. Also, many medical professionals have asked if it is possible to increase treatment longevities by a factor of two or more.

In general, surgical devices can provide life saving measures (heart valves, vessels), enhanced mastication (tooth root replacements), improved bone and soft tissue repairs (plates, rods, and screws for fraction fixation plus ligament, tendon, and skin replacements) and total joint arthroplasties (TJAs) to maintain function and ambulation. Millions of TJA prostheses constructed from synthetic biomaterials have been safely and effectively utilized over decades and consensus conferences have recognized their value and cost effectiveness. The risk factors listed above, however, are critically important to the longevities of TJA-based treatments.

Standards and Committee F04: Past and Present

Most of the synthetic materials that have been utilized for surgical implant devices over past decades were based on redirected uses of metallics, polymerics, and ceramics that were originally intended for non-biomedical, industrial-type applications. All of the following and many more examples from industry have been found relevant to the biomedical field:

• Experience gained about strength and degradation capacities from applications of metallics under machine-tool conditions and in sea-and-ground water conditions;
• Evaluations of various properties from aerospace and automotive applications; and
• Details about the rigidity, inertness and wear resistance from the cookware, electronic, and chemical industries.

Consensus standards specific to implant devices were started within ASTM through the formation of Committee F04 on Medical and Surgical Materials and Devices in 1962. The committee’s primary focus at that time emphasized the material and design aspects of constitution and properties that were directly applicable to existing device systems (including test methods). Industrial representatives (mostly from engineering) attended twice-yearly meetings where clinical practitioners (MDs and DMDs), university faculty (PhDs, MDs, and DMDs) and those from government were involved in the development of standards. These standards were intended to meet the needs of the developers, manufacturers, users, and regulators within the biomedical and surgical disciplines. Most activities and information were based on perspectives from the physical science/engineering disciplines with input from those with biological/medical science oriented backgrounds. This multidisciplinary coordination has been retained over the years, although significant changes have been instituted over the last decade as the biomaterial, biomechanical, biological and clinical disciplines have evolved.

Many of the standards developed for implant devices are utilized as part of industrial quality control and quality analysis programs. The basic information on material composition, strength, and surface finish is combined with design parameters such as component dimensions and tolerances to assure proper aspects of fit and fill for assembly, as well as locking and/or motions where indicated. Therefore, to develop appropriate and broadly useful standards, interactions among manufacturers, users, regulators, and general interests are necessary at the outset. The ASTM process provides this opportunity.

Another aspect of standardization extends to the retrieval and analysis of devices that are removed in surgery. After removal, studies must follow protocols to preserve the confidentiality of the patient while maximizing the quality and quantity of any investigations conducted. In general, “explant” device and record information can be separated into three tiers for classification. If the overall outcomes were as-anticipated and no unusual patient or device records or results are noted, this result would be classified as Tier I. Tier II would be reserved for conditions where something is noted, but the findings were judged not to have influenced the performance aspects of the patient or the device. When unanticipated changes or outcomes are found, a Tier III classification is warranted, and additional in-depth studies might be indicated. The ASTM F04 standard on device retrieval and analysis (F 561, Recommended Practice for Retrieval and Analysis of Implantable Medical Devices) provides a basis for more uniform methods and data collection which thereby enhances opportunities to utilize pre- and post-implant studies as part of improving existing devices and clinical treatments. Additionally, where indicated by multidisciplinary in-depth investigations, a new biomaterial, a new device design, and/or a new clinical treatment may then be proposed.

Devices, Instruments, and Future Consensus Standards

Consensus standards provided through ASTM Committee F04 have played a long-term and important role within the rapidly evolving discipline of implant devices. However, recent research has shown that previously utilized synthetics, when combined with new biological-origin products, can be of increased value. It is also recognized that completely new biological-origin and biomimetic products are now evolving from research, development, and applications. This field is now called tissue engineering (see article on page 30). It is anticipated that consensus standards will continue to play a very important role within this discipline, both nationally and internationally.

The importance of the changes that have occurred over the past five years within the primary disciplines associated with surgical implant devices and surgical rehabilitative procedures have resulted in a recent workshop (May 2000) that focused on the past, present, and future of consensus standards being developed within ASTM F04. Speakers were asked to address questions from the membership and to emphasize: What is and will be our primary role, how can we better serve all aspects of the discipline, and what should we do in the future to be appropriately relevant, efficient, and prospective? The workshop began with position statements from the elected officers and ASTM staff, which were followed by presentations from chairs of the subcommittees and a panel of industry vice presidents, CEOs, and FDA representatives. Subsequently, presentations were provided from affiliated organizations (societies, academies and international committees) related to inter-society and international harmonization.

In summary, the groups felt that F04’s future success would be enhanced by regular electronic (Internet-based) communication at all levels, the greater inclusion of evolving biologically oriented sciences and disciplines such as the tissue engineered medical products, the continued evolution of committee infrastructure to assure that all are enfranchised within the process, and that inter-society and international harmonization will be needed to maintain relevance within this rapidly evolving field. The future opportunities are many and we anticipate that medical treatments will continue to improve with an ever-increasing role of high technology and clinical outcome-based systems. //

Copyright 2001, ASTM