NETWORKS REPORTS

VAMAS – what is it?

The VAMAS project was established following an economic summit meeting in 1982 held at Versailles by the Heads of State of the seven leading industrial nations and representatives from the Commission of the European Communities. The main objective of VAMAS is to support world trade in high technology products. It achieves this through international collaborative projects aimed at providing the technical basis for drafting standards, codes of practice and specifications for advanced materials. The work undertaken by VAMAS covers all aspects of advanced materials science and technology that form the foundation for national and international standards. It includes:

• the development of test methods;

• the comparison of test results;

• the production of reference materials;

• the establishment of databases of material properties; and

• the agreement of nomenclature

The countries that have signed the memorandum of understanding to participate in VAMAS are Canada, France, Germany, Italy, Japan, UK, USA, and the Commission of the European Communities. Organisations from other countries may also take part in specific research activities. VAMAS has no funds of its own. Funding of VAMAS projects is through each organisation contributing its research effort and paying its own expenses.

The activities of VAMAS are focused around five technical themes: metals and metal matrix composites; polymers and polymer matrix composites; ceramics and ceramic matrix composites; non-materials specific test techniques; and materials classification and data. The research programmes are grouped together in Technical Work Areas (TWAs). The work of each TWA is led by an International Chairman appointed by the VAMAS Steering Committee and assisted by National Co-ordinators from each of the countries taking part in the TWA, who are appointed by their national delegate on the Steering Committee. 22 TWAs have been established covering the five themes of VAMAS and between them there are over 60 active projects.

Overall management of VAMAS is vested in the Steering Committee, which reviews the progress of each TWA, approves new projects, initiates new areas of activity, agrees policy and establishes procedures. Typically, the Steering Committee members are from government, research laboratories or standards bodies, with up to three representatives from each of the signatories of the VAMAS Memorandum of Understanding. The Chairmanship currently alternates every three years between the USA and the UK.

Currently, TWAs 1 & 7 in the fourth theme of Test techniques are working on topics relevant to biomaterials, wear test methods and tests for bioengineering materials. Other TWAs may be working in areas of relevance such as TWA 5, Polymer composites, or TWA 3, Ceramics.

Potential new participants in the work of existing TWAs are always welcome and interested organisations should contact the TWA Chairman in the first instance (for contact details see web site below). Ideas for possible new TWA activities are also welcome. Applications to establish a new TWA are considered by the Steering Committee and evaluated against the following criteria:

• the relevance of the work to advanced materials technology

• the importance of the proposed work area in terms of advancing technology, growth and employment

• the significance of the work in terms of standards development

• the non-duplication of other work being conducted elsewhere

• the probability of implementation of the results of any work undertaken

The benefits of VAMAS

VAMAS has contributed to the development of national and international standards through:

• pre-standardisation work in rapidly developing technical areas prior to the formal establishment of technical standards committees

• facilitation of, and in some cases, initiative for setting up of new standards technical committees

• transfer of results to standards bodies leading directly to international, European and national standards

• the development of assessment methods for materials behaviour and performance which contribute to the development and utilisation of advanced materials

• the production of reference materials and procedures

• the increased proficiency of laboratories, including industrial laboratories

• the harmonisation of different national test methods and guidelines, and networking between different groups working in similar areas, leading to budgetary savings.

There are also a number of secondary benefits of the work:

• the promotion of awareness of the importance of pre-normative research

• the establishment of national and international networks of laboratories

• improved international relations at the management level between national research and development programmes and between these programmes and the standards bodies

Through the establishment of links between VAMAS Technical Work Areas and various standards technical committees, often because VAMAS TWA participants are also members of the appropriate standards committees, work undertaken within VAMAS TWAs has contributed directly to the setting up of ISO Technical Committees, and VAMAS contributions have been instrumental in the establishment of a number of standards. ISO and IEC have agreed to publish Technology Trend Assessments (TTAs) based upon the work of VAMAS to accelerate the development of standards in advanced materials.

Descriptions of VAMAS and results of its work are available in the VAMAS Bulletin, published annually, and in VAMAS Technical Reports. In addition, individual articles are published in the trade and technical press, scientific journals and conference proceedings. The results of each national contribution to the work of the TWA is freely communicated to all other contributors to the TWA but remains confidential to the contributors until it is agreed otherwise.

To get more information about VAMAS publications or to suggest new areas for VAMAS activities, contact the VAMAS Secretariat, c/o Mr John Sillwood, Centre for Materials Measurement & Technology, National Physical Laboratory, Teddington, Middlesex TW11 0LW, United Kingdom, Tel: +44 181 943 7183, Fax: +44 181 943 2989, E-mail vamas@npl.co.uk, web-site http://www.npl.co.uk/npl/vamas .

TWA1 & TWA7 Joint Activity on Biomaterials

Total joint replacements in human bodies are increasing in quantity world-wide. This is due to increasing life expectancy, population growth, advances in medical science, rigorous exercise, and an increasing number of accidents. One of the key-life limiting factors of the current bio-components is the generation of numerous particles from the wear of Ultra-high-molecular-weight Polyethylene (UHMWPE) in contact with the Cobalt-Chromium (CoCr) alloy.

TWA1 under the leadership of Dr. Stephen M. Hsu of the National Institute of Standards and Technology in Gaithersburg USA (NIST), is undertaking an international round-robin study on wear debris characterisation methodology and representation. The material system to be studied is an ultra-high molecular weight polyethylene and a cobalt-chromium alloy. The objective of the study is to develop wear debris characterisation methods in terms of size, shape, and morphology, and to develop mathematical representations of the debris. While the wear debris formation is the current life limiting factor of artificial joints, the exact nature of the linkage between debris size, shape, and morphology to bioactivity is not well understood.

TWA7 under the leadership of Dr. Tetsuya Tateishi of MITI’s National Institute for Advanced Interdisciplinary Research in Ibaraki Japan (MEL) has developed a bioculture technique to determine the relationship between debris particles and bioactivity. The test uses murine macrophage or osteoblast cell lines, in an ‘inverted culture system’ to ensure adequate contact between the wear particles and the cells. Interleukin-1 beta is a cytokine that is reported to enhance the activity of osteoclasts and to be produced by activated macrophages in the tissue surrounding loosened orthopaedic implants. The test system, as currently constituted, uses IC-21 murine macrophage cells and is designed to detect the release of Interleukin-1 beta using ELISA and measure the cytokine gene expression using RNA extraction followed by PCR amplification. Initial results are shown in a figure and table, and look encouraging.

The joint TWA1 & TWA7 activity will identify if a particular population of size, shape, or morphology is more bioactive than others. This may lead to international standardisation of biomaterial test methods in the future. Specific samples of metal and UHMWPE are sent to each TWA1 participant, and using the same processing procedures and wear tester (pin on disk), with ASTM F-732 method as a guide for testing, populations of wear debris are then produced for characterisation on-site and distribution to TWA7 participants for biocompatibility testing. Twenty-one laboratories in eleven countries have agreed to participate in the TWA1 wear activity. The joint group is still seeking laboratories to conduct bioculture tests. Interested parties should contact Dr. Tateishi to join the TWA7 activity on the bioculture test round robin.

Fig. 1 Interleukin -1 beta release from IC-21 cells phagocytosing polyethylene particles

Table 1 Relative expression of mRNAs for the cytokines involved in osteolysis