1.1 This practice covers a series of recommendations, generally applicable to all medical devices, for characterization of the morphology, shape, size, and size distribution of particles. The methods utilized include sieves, optical, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrooptical.

1.2 While characterizing the quantity or number of particles shed from medical devices is important, this is not covered within the scope of the current document. AAMI TIR 42 and USP <788> provide guidelines for determination of particle quantities in various size ranges.

1.3 These methods are appropriate for particles produced by a number of different methods. These methods can include simulated use approaches such as in vitro wear test machines (Test Method F732), total joint simulation systems (Guides F1714 and F1715), abrasion testing, and vascular durability testing (Guide F2942). Other methods for producing particles such as shatter boxes or pulverizers, as well as commercially available particles, and particles harvested from tissues in animal or clinical studies can be used.

1.4 Except for chemical composition, this standard does not address sample preparation procedures and/or test systems that can be affected by chemical properties (for example, solubility, miscibility). While this standard does not provide detailed recommendations regarding assessment of chemical properties of particles, these should be considered.

1.5 The particles may be metallic, polymeric, or ceramic and are released from medical device materials either acutely or chronically (for example, due to wear).

1.6 The digestion procedures to be used and issues of sterilization of retrieved particles are not the subject of this practice.

1.7 A classification scheme for description of particle morphology is included in Appendix X3.

1.8 When nanoparticles (that is, having at least one dimension less than 100 nm) are known to be present or are expected, other characterization methods may be needed. For information regarding nanoparticle characterization, refer to standards that address nanoparticles (for example, ISO 21363, ISO/TR 10993-22, ISO/TR 16196).

1.9 This standard does not address ions released from medical devices.

1.10 The values stated in SI units, including units officially accepted for use with SI, are to be regarded as standard. No other systems of measurement are included in this standard.

1.11 As a precautionary safety measure for handling test samples during particle characterization analyses, removed particles from implant tissues should be sterilized or minimally disinfected by an appropriate means that does not adversely affect these particles.

1.12 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.13 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.