The biological response to materials in the form of small particles, as from wear debris, often is significantly different from that to the same materials as larger implant components. The size and shape (morphology) of the particles may have a major effect on the biological response; therefore, this practice provides a standardized nomenclature for describing particles. Such a unified nomenclature will be of value in interpretation of biological tests of responses to particles, in that it will facilitate separation of biological responses associated with shape from those associated with the chemical composition of debris.

The quantity, size, and morphology of particles released as wear debris from implants in vivo may produce an adverse biological response which will affect the long term survival of the device. Characterization of such debris will provide valuable information regarding the effectiveness of device designs or methods of processing components and the mechanisms of wear.

The morphology of particles produced in laboratory tests of wear and abrasion often is affected by the test conditions, such as the magnitude and rate of load application, device configuration, and test environment. Comparison of the morphology and size of particles produced in vitro with those produced in vivo will provide valuable information regarding the degree to which the method simulates the in vivo condition being modeled.

1.1 This practice outlines a series of procedures for characterization of the morphology, number, size, and size distribution of particles. The methods utilized include sieves, optical, SEM, and electrooptical.

1.2 These methods are appropriate for particles produced by a number of different methods. These include wear test machines, total joint simulation systems, abrasion testing, methods for producing particulates, such as shatter boxes or pulverizors, commercially available particles, and particles harvested from tissues in animal or clinical studies.

1.3 The debris may include metallic, polymeric, ceramic, or any combination of these.

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

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

1.6 As a precautionary measure, removed debris from implant tissues should be sterilized or minimally disinfected by an appropriate means that does not adversely affect the particulate material. 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 and health practices and determine the applicability of regulatory limitations prior to use.