ASTM F3336-22

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.
Designation: F3336 − 22
Standard Practice for
Lipid Preconditioning of Ultra-High-Molecular-Weight
Polyethylene for Accelerated Aging
This standard is issued under the fixed designation F3336; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope susceptibilitytooxidativechanges.Themethodshavenotbeen
evaluatedforuseinpreconditioningofUHMWPEcomponents
1.1 It is the intent of this practice to permit an investigator
for subsequent testing of mechanical or wear properties.
to incorporate lipids found in the synovial environment into
ProcedureAshould not be used for preconditioning of UHM-
polymeric specimens. This can be used as a preconditioning
WPEcomponentsforsubsequenttestingofmechanicalorwear
step to evaluate the oxidative stability of ultra-high-molecular-
properties.
weight polyethylene (UHMWPE) materials. This practice de-
scribes a laboratory procedure for preconditioning of UHM- 1.7 The values stated in SI units are to be regarded as
WPE specimens. standard. The values given in parentheses are mathematical
conversions to inch-pound units that are for information only
1.2 The preconditioned UHMWPE can be aged at elevated
and are not considered standard.
temperature and at elevated oxygen pressure following meth-
1.8 This standard does not purport to address all of the
ods of accelerated aging described in Practice F2003,to
safety concerns, if any, associated with its use. It is the
accelerate oxidation of the material and thereby allow for the
responsibility of the user of this standard to establish appro-
evaluation of its long-term chemical stability.
priate safety, health, and environmental practices and deter-
1.3 The preconditioned UHMWPE can be tested without
mine the applicability of regulatory limitations prior to use.
further aging using a method to evaluate oxidative stability
1.9 This international standard was developed in accor-
such as oxidation induction time as described in Test Method
dance with internationally recognized principles on standard-
D3895.
ization established in the Decision on Principles for the
1.4 Themethodsofthispracticemaybeusedonanytypeof
Development of International Standards, Guides and Recom-
UHMWPE material intended for use in total joint arthroplasty
mendations issued by the World Trade Organization Technical
in a synovial joint (for example, conventional, cross-linked,
Barriers to Trade (TBT) Committee.
antioxidant stabilized, etc.). See Appendix X1.
2. Referenced Documents
1.5 Although the preconditioning method followed by ac-
celerated aging described by this practice will permit an
2.1 ASTM Standards:
investigator to compare the oxidative stability of different
D883Terminology Relating to Plastics
UHMWPE materials, it is recognized that this method is not
D3895Test Method for Oxidative-Induction Time of Poly-
known to simulate the degradative mechanisms for an implant
olefins by Differential Scanning Calorimetry
during real-time shelf aging or in vivo. The described methods
F648Specification for Ultra-High-Molecular-Weight Poly-
have not been evaluated for mechanical testing under cyclic
ethylene Powder and Fabricated Form for Surgical Im-
loading.
plants
F2003Practice for Accelerated Aging of Ultra-High Mo-
1.6 The preconditioning and accelerated aging methods
lecular Weight Polyethylene after Gamma Irradiation in
specifiedhereinareintendedtoranktheresistancetooxidation
Air
of materials as a result of the absorption of lipids, which may
F2102Guide for Evaluating the Extent of Oxidation in
occur in UHMWPE following implantation, and to determine
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
Surgical Materials and Devices and is the direct responsibility of Subcommittee For referenced ASTM standards, visit the ASTM website, www.astm.org, or
F04.15 on Material Test Methods. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Jan. 1, 2022. Published January 2022. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
F3336-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3336 − 22
Polyethylene Fabricated Forms Intended for Surgical 5. Apparatus
Implants
5.1 Absorption Vessel—A glass container such as a beaker
2.2 ISO Standards:
or an Erlenmeyer flask that can contain the desired volume of
ISO 5834 Implants for Surgery—Ultra-High Molecular
theabsorptionmediumandthatcanbestirredandheatedsafely
Weight Polyethylene
up to 120°C, with an accuracy of 2°C.
5.2 Heating and Stirring Apparatus—A hotplate equipped
3. Terminology
with a stirring function. For the high absorption procedure
3.1 Definitions—For definitions of terms in this practice
performed at 120°C, it will be necessary to stir the medium
relating to plastics, refer toTerminology D883. For definitions
during absorption to maintain homogeneity of the sample
of terms in this practice relating to UHMWPE, refer to
surfaceexposure.Anoilbathshallbeplacedontheheatingand
Specification F648 and ISO 5834.
stirring apparatus to create a heating environment which can
3.2 Definitions of Terms Specific to This Standard:
maintain the temperature of the absorption medium at 120°C,
3.2.1 lipids, n—lipophilic compounds which have been
with an accuracy of 61°C. Alternative heating methods may
shown to absorb into UHMWPE from the synovial fluid (1).
be used so long as the required accuracy is obtained.
3.2.2 oxidation, n—theincorporationofoxygenintoanother
NOTE 1—Because elevated temperatures can cause lipid contamination
molecule (for example, UHMWPE) by means of a chemical
of the surfaces of the aging vessels, it is recommended that an apparatus
reaction, resulting in the formation of a chemical covalent be dedicated to the aging of lipid-containing specimens.
bond.
6. Test Specimens
3.2.3 oxidative stability, n—the resistance to oxidation in a
6.1 Specimensshallbefirstmachinedandpreconditionedin
material. A specific material can be described to have more
this form. Cubes (1 cm×1cm×1cm)are recommended.
oxidativestabilityifthechangeinitsoxidationunderdescribed
6.2 Following preconditioning, physical or chemical char-
conditions is less than that of another material under the same
acterizationtestssuchasthemeasurementofcross-linkdensity
conditions.
may be performed on smaller samples cut from the original
4. Significance and Use
(preconditioned) sample.
4.1 Thispracticesummarizestwomethodsthatmaybeused
7. Conditioning
to precondition UHMWPE by the absorption of lipids to
7.1 Ifsamplestobeusedhavebeenpreviouslyprocessedby
differentiate the simulated in vitro oxidative stability of
radiation, then samples shall be removed from their inert/
UHMWPEs, after lipid exposure.
vacuum packaging immediately prior to the procedure.
4.1.1 Procedure A, High Squalene Absorption—This
method of preconditioning with lipids may be used for com-
7.2 After completing the preconditioning procedure, speci-
parative oxidative stability testing to screen different materials mens shall be maintained at 23 6 2°C (73.4 6 3.6°F) for not
under aggressive conditions.
more than seven days, starting from the end date of
4.1.2 Procedure B, Mixed Lipid Absorption—This method incorporation, before performing further testing or accelerated
of preconditioning may be used for comparative oxidative
aging.
stability testing under mild conditions that more closely
8. Procedure
simulate in-vivo conditions.
8.1 Specimen Orientation—Test specimens shall be arrayed
4.2 This practice may be used to accelerate the oxidation of
withintheabsorptionvesselsuchthatallrelevantsurfaceshave
UHMWPE components when using elevated temperature and
equivalent access to the medium containing the lipids during
elevated oxygen pressure according to the methods of Practice
the test, preferably by stirring.
F2003. Under real-time conditions such as implantation, oxi-
dativechangestoUHMWPEformulationsmaytakemonthsor 8.2 Procedure A, High Squalene Absorption—Forprecondi-
years to produce changes that may result in deleterious tioning with lipids for comparative oxidative stability testing
mechanical performance. The method outlined in this practice under aggressive conditions, cubes of test material (1 cm ×
permits the preparation of UHMWPE for evaluation of oxida- 1cm × 1 cm) shall be immersed in preheated squalene (see
tive stability in a relatively short period of time (for example, Annex A1) at 120°C for 2 h. After 2 h, remove the samples,
allow them to cool to room temperature, and wipe them clean
weeks).
with a dry, lint-free wipe prior to storage or further testing.
4.3 This practice may also be used to precondition UHM-
8.3 Procedure B, Mixed Lipid Emulsion—For precondition-
WPE test specimens prior to characterization of their physical
and chemical properties. In particular, this practice may be ingwithlipidsforcomparativeoxidativestabilitytestingunder
mild conditions, cubes of test material (1 cm×1cm×1cm)
used for preconditioning with lipids prior to oxidation induc-
tion time (OIT) testing as outlined in Test Method D3895. shallbeimmersedinamixedlipidemulsion(seeAnnexA2)at
40°C for three weeks or until 1.0 6 0.1 mg of weight
absorption is measured, whichever occurs first. Measure the
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
absorbed mass once per week. Wipe the samples clean with a
4th Floor, New York, NY 10036, http://www.ansi.org.
dry, lint-free wipe prior to weighing. Replace with fresh
The boldface numbers in parentheses refer to a list of references at the end of
this standard. emulsion when replacing the samples after weighing.
F3336 − 22
8.4 Stability of Lipid Absorption Media—The lipids used in 9. Reporting of Specimen Preparation and Test
the procedures are often sensitive to environmental changes. Conditions
For Procedure A, squalene shall not be reused. It shall be
9.1 The written report shall include details regarding the
removed from the manufacturer or supplier’s container imme-
preparation of the test samples, the preparation of
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