ASTM F1877-05(2010)
(Practice)Standard Practice for Characterization of Particles
Standard Practice for Characterization of Particles
SIGNIFICANCE AND USE
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.
SCOPE
1.1 This practice covers 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 (Test Method F732), total joint simulation systems (Guides F1714 and F1715), 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F1877 − 05(Reapproved 2010)
Standard Practice for
Characterization of Particles
This standard is issued under the fixed designation F1877; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice covers a series of procedures for charac- 2.1 ASTM Standards:
terization of the morphology, number, size, and size distribu- C242 Terminology of Ceramic Whitewares and Related
tion of particles. The methods utilized include sieves, optical, Products
SEM, and electrooptical. C678 Test Method for Determination of Particle Size Distri-
bution of Alumina or Quartz Using Centrifugal Sedimen-
1.2 Thesemethodsareappropriateforparticlesproducedby
tation (Withdrawn 1995)
a number of different methods. These include wear test
E11 Specification for Woven Wire Test Sieve Cloth and Test
machines (Test Method F732), total joint simulation systems
Sieves
(Guides F1714 and F1715), abrasion testing, methods for
E161 Specification for Precision Electroformed Sieves
producing particulates, such as shatter boxes or pulverizors,
E766 Practice for Calibrating the Magnification of a Scan-
commercially available particles, and particles harvested from
ning Electron Microscope
tissues in animal or clinical studies.
E1617 Practice for Reporting Particle Size Characterization
1.3 The debris may include metallic, polymeric, ceramic, or
Data
any combination of these.
F561 Practice for Retrieval and Analysis of Medical
Devices, and Associated Tissues and Fluids
1.4 The digestion procedures to be used and issues of
sterilization of retrieved particles are not the subject of this F660 Practice for Comparing Particle Size in the Use of
Alternative Types of Particle Counters
practice.
F661 Practice for Particle Count and Size Distribution Mea-
1.5 A classification scheme for description of particle mor-
surement in Batch Samples for Filter Evaluation Using an
phology is included in Appendix X3.
Optical Particle Counter (Discontinued 2000) (Withdrawn
1.6 The values stated in SI units are to be regarded as
2000)
standard. No other units of measurement are included in this
F662 Test Method for Measurement of Particle Count and
standard.
Size Distribution in Batch Samples for Filter Evaluation
1.7 As a precautionary measure, removed debris from Using an Electrical Resistance Particle Counter (Discon-
implanttissuesshouldbesterilizedorminimallydisinfectedby tinued 2002) (Withdrawn 2002)
an appropriate means that does not adversely affect the F732 Test Method for Wear Testing of Polymeric Materials
particulate material. This standard does not purport to address Used in Total Joint Prostheses
all of the safety concerns, if any, associated with its use. It is F1714 GuideforGravimetricWearAssessmentofProsthetic
the responsibility of the user of this standard to establish Hip Designs in Simulator Devices
appropriate safety and health practices and determine the F1715 Guide for Wear Assessment of Prosthetic Knee De-
applicability of regulatory limitations prior to use. signs in Simulator Devices (Withdrawn 2006)
1 2
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Surgical Materials and Devices and is the direct responsibility of Subcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
F04.16 on Biocompatibility Test Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved June 1, 2010. Published September 2010. Originally the ASTM website.
ε1 3
approved in 1998. Last previous edition approved in 2005 as F1877 – 05 . DOI: The last approved version of this historical standard is referenced on
10.1520/F1877-05R10. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1877 − 05 (2010)
3. Terminology detailed studies, several methods are described that may be
utilized for numerically characterizing their dimensions, size
3.1 Definitions of Terms Specific to This Standard:
distribution, and number.
3.1.1 agglomerate, n—a jumbled mass or collection of two
or more particles or aggregates, or a combination thereof, held
5. Significance and Use
together by relatively weak cohesive forces caused by weak
chemical bonding or an electrostatic surface charge generated
5.1 Thebiologicalresponsetomaterialsintheformofsmall
by handling or processing.
particles, as from wear debris, often is significantly different
from that to the same materials as larger implant components.
3.1.2 aggregate, n—a dense mass of particles held together
The size and shape (morphology) of the particles may have a
by strong intermolecular or atomic cohesive forces that is
major effect on the biological response; therefore, this practice
stable to normal mixing techniques, including high-speed
provides a standardized nomenclature for describing particles.
stirring and ultrasonics.
Such a unified nomenclature will be of value in interpretation
3.1.3 aspect ratio (AR), n—a ratio of the major to the minor
of biological tests of responses to particles, in that it will
diameter of a particle, which can be used when the major axis
facilitate separation of biological responses associated with
does not cross a particle outline (see 11.3.3).
shape from those associated with the chemical composition of
3.1.4 elongation (E), n—ratio of the particle length to the
debris.
average particle width (see 11.3.4).
5.2 The quantity, size, and morphology of particles released
3.1.5 equivalent circle diameter (ECD), n—ameasureofthe
as wear debris from implants in vivo may produce an adverse
size of a particle (see 11.3.2 and Appendix X1).
biological response which will affect the long term survival of
3.1.6 Feret diameter, n—the mean value of the distance the device. Characterization of such debris will provide valu-
between pairs of parallel tangents to a projected outline of a able information regarding the effectiveness of device designs
particle. or methods of processing components and the mechanisms of
wear.
3.1.7 flocculate, n—a group of two or more attached par-
ticles held together by physical forces, such as surface tension,
5.3 The morphology of particles produced in laboratory
adsorption, or similar forces.
tests of wear and abrasion often is affected by the test
conditions, such as the magnitude and rate of load application,
3.1.8 form factor (FF), n—a dimensionless number relating
device configuration, and test environment. Comparison of the
area and perimeter of a particle, as determined in 11.3.6.
morphology and size of particles produced in vitro with those
3.1.9 irregular, adj—a particle that cannot be described as
produced in vivo will provide valuable information regarding
round or spherical. A set of standard nomenclature and refer-
the degree to which the method simulates the in vivo condition
ence figures are given in Appendix X2.
being modeled.
3.1.10 particle, n—the smallest discrete unit detectable as
determined in test methods. A nanoparticle has at least one
6. Interferences
dimension less than 100 nm.
6.1 Particles may form aggregates or agglomerates during
3.1.11 particle breadth, n—distancebetweentouchpointsof
preparation and storage. These would result in an increase in
the shortest Feret pair, orthogonal to length.
measured particle size and decrease in particle number. It is
3.1.12 particle length, n—distance between touch points of
essential that care be taken to resuspend particles prior to
maximumFeretpair.Thisvaluewillbegreaterthanorequalto analysis and to note any effects of the dispersant used.
the maximum Feret diameter.
6.2 Debris from wear tests or harvested from tissues may
3.1.13 rectangular, adj—a particle that approximates a
containamixtureofmaterials.Careshouldbetakentoseparate
square or rectangle in shape.
the particles and methods utilized to determine the chemical
composition of the particles.
3.1.14 roundness (R), n—a measure of how closely an
object represents a circle as determined in 11.3.5.
6.3 Many automated particle counters operate on the as-
sumption that the particles are spherical. These methods may
3.1.15 spherical, adj—a particle with a generally spherical
shape that appears round in a photograph. not be appropriate for nonspherical debris.Additional methods
should be used to verify size using methods that take aspect
ratio into consideration, for example, SEM image analysis.
4. Summary of Practice
4.1 Particles produced by implant wear in vivo in animal or
7. Apparatus
clinical studies are harvested from tissues after digestion
utilizing methods, such as those in Practice F561. Particles 7.1 Scanning Electron Microscope (SEM) (see Practice
E766):
generated in vitro, or obtained from commercial sources, are
used as received, or after digestion, if they were generated in 7.1.1 Standard SEM equipment can be utilized for many
protein solutions, and further separation if there are signs of studies. In special instances, such as with polymeric particles,
aggregation. A two level analysis is provided. For routine a low acceleration voltage (1-2 kV) machine with a high
analysis, the particles are characterized by the terms of brightness electron source, such as a field emission tip, may be
morphology and by size using Feret diameters. For more utilized.
F1877 − 05 (2010)
TABLE 1 Recommended Magnifications for Particle Imaging
11. Particle Characterization
Magnification Particle Size Range (µm)
11.1 Particle Shape (Morphology)—Refer to the photo-
10000 0.1 to 1.0
1000 1 to 10 graphs and classify the morphology of the particles using the
100 10 to 100
nomenclature in Appendix X2.
11.2 Routine Particle Size Determination Using Feret Di-
ameters:
7.1.2 Elemental analysis may be accomplished with an
11.2.1 The use of multiple Feret diameters especially is
energy dispersive spectrometer (EDS) for energy dispersive
useful for spherical and rectangular particles.
X-ray analysis (EDXA).
11.2.2 Determine the particle size and aspect ratio as the
7.2 Optical Microscope—An optical microscope operating
mean of two Feret diameters.
in the transmission mode may be utilized. Dark field illumina-
11.2.3 Calculate the particle size distribution based on the
tion may enhance visualization of some particles. Polarized
volume of solution used and the size of the filters.
light will facilitate identification of semicrystalline polymeric
materials. 11.3 Detailed Particle Shape Analysis for Irregular Shaped
Particles:
7.3 Automatic Particle Counters (see Practice F660):
11.3.1 Fiveparticledimensionalmeasurementsareprovided
7.3.1 Image Analyzer—This instrument counts particles by
using examples shown in Appendix X1. One is a measure of
size as those particles lie on a microscope slide.
particle size while the other four are shape descriptors.
7.3.2 Optical Counter—This instrument measures the area
of a shadow cast by a particle as it passes a window. From this 11.3.2 The Equivalent Circle Diameter (ECD) as a Measure
area the instrument reports the diameter of a circle of equal of Particle Size:
area.
11.3.2.1 The ECD is defined as the diameter of a circle with
7.3.3 Electrical Resistance Counter—This instrument mea-
an area equivalent to the area (A) of the particle and has the
sures the volume of an individual particle. From that volume
units of length:
theinstrumentreportsthediameterofasphereofequalvolume
ECD 5 4*A/π 2 (1)
~ !
(see Test Methods C678).
11.3.3 The Aspect Ratio (AR) is a Common Measure of
8. Reagents
Shape:
8.1 Particle-Free (0.2 µm Filtered) Deionized Water, for
11.3.3.1 The AR is the ratio of the major diameter (d )to
max
nonpolymeric particles.
the minor diameter (d ). The major diameter is the longest
min
8.2 Particle-Free (0.2 µm Filtered) Methanol or Ethanol,
straight line that can be drawn between any two points on the
for polymeric or mixed debris.
outline.The minor diameter is the longest line perpendicular to
the major diameter:
8.3 Ultra-Cleaning Reagent,forapparatusorlabwareclean-
ing. AR 5 d /d (2)
max min
11.3.4 The elongation (E), is similar to the AR except it is
9. Specimen Preparation
more suited for the measurement of much longer particles,
9.1 Specimens from explanted tissues from animal or clini-
especially fibrilar particles, where the major axis line does not
cal studies may need to be harvested and digested using
stay within the particle boundaries. Refer to particle types A
methods, such as those described in Practice F561.
and C in Appendix X1.
9.2 Particles from in vitro cell culture tests also may need to
11.3.4.1 The E is the ratio of the length (FL) to the breadth
be digested and harvested.
(FW):
9.3 Centrifugation of particles from wear may be
E 5 FL/FW (3)
considered, if necessary, at 400 g for 10 min, and resuspended
in water or methanol. Resuspended particles may be filtered in 11.3.5 The roundness (R) is a measure of how closely a
accordance with Practice F561 prior to examination by SEM.
particle resembles a circle. The R varies from zero to one in
magnitude with a perfect circle having a value of one.
10. Particle Imaging by Light or Scanning Electron
R 5 ~4A!/~π d ! (4)
max
Microscopy
where:
10.1 Images may either be captured electronically or pho-
A = area, and
tographically for subsequent analysis.
d = the maximum diameter.
max
10.2 For the characterization and measurements to be
accurate, it is essential that the particles be imaged at the 11.3.6 The form factor (FF) is similar to R but is based on
largest magnification as possible. The magnifications in Table the perimeter (p) of the particle outline rather than the major
1 are recommended. diameter. The FF is more sensitive to the variations in
roughness of the particle outline.
10.3 For particle size distribution measurements, divide
each of the size ranges specified in Table 1, into 10 bins. FF 5 4πA/p (5)
F1877 − 05 (2010)
where: based on identification of key elemental peaks for the major
elements likely to be present in the sample.
p = perimeter of the particle outline.
13. Report
11.4 Other Particles Size Determination Methods:
13.1 Reportthefollowinginformation(seePracticeE1617):
11.4.1 Particles larger than 20 µm may be determined by
13.1.1 The source of the particles and materials and meth-
sieves described in Specifications E11 and E1
...
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