1、Designation: F 732 00 (Reapproved 2006)Standard Test Method forWear Testing of Polymeric Materials Used in Total JointProstheses1This standard is issued under the fixed designation F 732; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a laboratory method forevaluating the wear properties of combinations of
3、materialsthat are being considered for use as bearing surfaces of humantotal joint prostheses. The body of this test method containsgeneral methods which apply to all types of prosthesis wearapplications while individual annexes describe specific weartest methods and clinical validation criteria tai
4、lored to eachdistinct wear application (for example, linear reciprocatingmotion, ball-cup (“hip-type”) wear, delamination wear, etc.). Itis the intent of this test method to rank materials, within eachwear application, for polymer wear rates under simulatedphysiological conditions. It must be recogn
5、ized, however, thatcontact geometries and wear motions are simplified using suchmethods. This test method, therefore, represents only an initialstage in the full wear characterization of a candidate material.1.2 All candidate materials should be tested in an appropri-ate joint simulator apparatus us
6、ing prototype prostheses beforebeing used in clinical trials in patients. The tests described inthis test method are used to quickly and reliably screen materialcombinations for wear performance in different orthopaedicwear applications prior to committing them to more expensiveand time-consuming jo
7、int simulator testing. In addition, thesesimplified tests can be used to relate material, surface finish, orother parameters to wear behavior on a more practical basisthan is possible in joint simulator tests.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsF75 Specif
8、ication for Cobalt-28 Chromium-6 MolybdenumAlloy Castings and Casting Alloy for Surgical Implants(UNS R30075)F86 Practice for Surface Preparation and Marking of Me-tallic Surgical ImplantsF 648 Specification for Ultra-High-Molecular Weight Poly-ethylene Powder and Fabricated Form for Surgical Im-pla
9、ntsF 799 Specification for Cobalt-28Chromium-6MolybdenumAlloy Forgings for Surgical Implants (UNS R31537,R31538, R31539)F 1537 Specification for Wrought Cobalt-28 Chromium-6Molybdenum Alloy for Surgical ImplantsF 2025 Practice for Gravimetric Measurement of PolymericComponents for Wear AssessmentG 4
10、0 Terminology Relating to Wear and Erosion3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 wearfor the purpose of this test method, the pro-gressive loss of material from the polymer specimen as a resultof the oscillating motion against the counterface under load.Wear may be ge
11、nerated by several mechanisms includingadhesion, two or three body abrasion, surface fatigue, or otherprocesses.3.1.2 wear ratethe volume of material lost due to wearper unit of sliding distance (or per million wear cycles ifcomplex motion patterns result in a non-uniform slidingdistance across the
12、specimen; see 4.3).4. Significance and Use4.1 This test method is intended to be performed in con-junction with pin-on-flat wear machines or similar machinesthat are designed to evaluate simplified specimen geometries.4.2 This test method is designed to evaluate combinations ofmaterials with respect
13、 to the amount of polymer wear, wherequantifiable wear occurs primarily on the polymeric compo-nent. With some combinations of materials, significant wear ofthe counterface may occur, with subsequent embedding ofcounterface debris particles in the polymer. Such an occurrencewill render the weight lo
14、ss of the polymer specimen unreliableas an indicator of the polymer wear.4.3 Wear is reported as volume loss of the polymericspecimen as a function of sliding distance; however, if thesliding distance is not constant across the polymeric specimensurface due to complex motion patterns, wear may be re
15、ported1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Materials Test Methods.Current edition approved March 1, 2006. Published April 2006. Originallyapproved in 1982. Last previou
16、s edition approved in 2000 as F 732 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Intern
17、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.as volume loss of the polymeric specimen as a function of wearcycles (in which case a “wear cycle” shall be defined). Volumeloss of the polymer specimen is determined by dividing theexperimental weight loss
18、by the density of the polymer. Forease of interpretation, wear should be reported as a function ofboth the number of wear cycles and the sliding distance, whenpossible.4.4 The reference for the comparative evaluation of candi-date materials shall be the wear rate of ultra-high-molecular-weight polye
19、thylene (UHMWPE) conforming to SpecificationF 648 bearing against counterfaces of cobalt-chromium-molybdenum alloy (in accordance with Specifications F75,F 799,orF 1537), having prosthetic-quality surface finish andlubricated with bovine blood serum (see 5.2).5. Apparatus and Materials5.1 Orthopaedi
20、c Wear Application:5.1.1 For linear reciprocating wear motion applications,refer to Annex A1.5.1.2 For fixed-bearing ball-cup (“hip-type”) wear motionapplications, refer to Annex A2.5.1.3 For nominally linear motion delamination wear appli-cations, refer to Annex A3.NOTE 1Other types of applications
21、 may be addressed in later revi-sions.5.2 Lubricant (see also Annex A4):5.2.1 The specimen shall be lubricated with bovine bloodserum unless an alternative medium can be justified as de-scribed in section 5.2.8. Since different sera differ in compo-sition (protein concentration, etc.), dilution with
22、 deionizedwater of up to 75 % (volume fraction) may be appropriate. Theappropriate dilution shall be based on satisfaction of theclinical validation criteria in the appropriate annex.5.2.2 A filter-sterilized serum rather than pooled serumshould be used since the former is less likely to containhemo
23、lyzed blood material, which has been shown to adverselyaffect the lubricating properties of the serum (1)3. Serum mustbe filtered to remove hard, abrasive, particulate contaminantsthat might otherwise affect the wear properties of the speci-mens being tested.5.2.3 Maintain the volume, concentration,
24、 and temperatureof the lubricant nearly constant throughout the test. This maybe accomplished by sealing the chambers so that water doesnot evaporate, by periodically or continuously replacing evapo-rated water with deionized water, or by recirculating thelubricant in a sealed environment.5.2.4 To r
25、etard bacterial degradation, freeze and store theserum until needed for testing. In addition, it is recommendedthat the serum contains a mass fraction of 0.2 to 0.3 % sodiumazide (or other suitable antibacterial agent) to minimize bacte-rial degradation.NOTE 2Sodium azide is a poison and must be han
26、dled very carefully.5.2.5 It is recommended that ethylene-diaminetetraaceticacid (EDTA) be added to the serum at a concentration of 20mM (7.45 g/L) to bind calcium in solution and minimizeprecipitation of calcium phosphate onto the bearing surfaces.The latter event has been shown to strongly affect
27、the frictionand wear properties, particularly of polyethylene/ceramic com-binations (2).5.2.6 Additives such as sodium azide and EDTA shall bedissolved in deionized water and passed through a 0.2-m filterbefore adding to bovine serum.5.2.7 The appropriate interval for replacing used serumdepends on
28、how long the serum maintains its composition (forexample, lubricating properties) under the specific testconditions/materials being used and the additives present in theserum. There is no minimum replacement interval. The maxi-mum replacement interval is two weeks. The selected intervalmust meet the
29、 validation requirements in the appropriateannex.5.2.8 Alubricant other than bovine serum shall be used onlywhen it can be shown that the lubricant reproduces clinicalwear mechanisms as well or better than bovine serum. In suchcase the lubricant shall be specified in the test report.6. Preparation o
30、f Specimens6.1 The governing rule for specimen preparation is that thefabrication process parallels that used or intended for use in theproduction of actual prostheses, in order to produce a specimenwith comparable bulk material properties and surface charac-teristics (see Practice F86).6.2 Polymers
31、 and Composites:6.2.1 Obtain a fabrication history for each polymeric orcomposite specimen, including information such as grade,batch number, and processing variables, including method offorming (extruding, molding, etc.), temperature, pressure, andforming time used, articulation surface preparation
32、 methods(see Annex A5) and any post-forming treatments, includingsterilization.6.2.2 Pre-test characterization may include measurement ofbulk material properties, such as molecular-weight range anddistribution, percent crystallinity, density, or others. The sur-face finish of specimens may be charac
33、terized by profilometry,photomicrography, replication by various plastics, or othertechniques.6.2.3 SterilizationSterilize the specimens in a mannertypical of that in clinical use for such devices unless it can beproven that this has no effect on wear properties of thematerials. Report sterilization
34、 processing parameters with theaging time prior to each test, if known. Sterilization of all testand control specimens within a specific test group should bedone simultaneously (in a single container), when possible, tominimize variation among the specimens.6.2.4 Cleaning of Polymer SpecimensPrior t
35、o wear test-ing, careful cleaning of the polymer specimens is important toremove any contaminants that would not normally be presenton an actual prosthesis. During the wear test, the specimensmust be re-cleaned and dried before each wear measurement toremove any extraneous material that might affect
36、 the accuracyof the measurement. The required procedure for cleaning anddrying of polymeric specimens, as defined in Practice F 2025,is given in Annex A6.6.3 Soaking of Polymeric and Composite Specimens:3The boldface numbers in parentheses refer to a list of references at the end ofthis test method.
37、F 732 00 (2006)26.3.1 Polymeric and composite specimens should be pre-soaked in the wear test lubricant to minimize fluid-sorptionduring the wear test. Without presoaking, specimens madefrom very low-wear polymers such as UHMWPE could showa net increase in weight or volume during the initial wearint
38、ervals due to fluid sorption (1, 3). The error due to fluidsorption can be reduced through presoaking and use of controlsoak specimens. The length of presoaking depends on thevariability and magnitude of fluid sorption encountered (3).Aminimum of one control soak specimen per material conditionis re
39、quired.6.4 Counterfaces of Metal Alloys, Ceramic, or Other Mate-rials:6.4.1 CharacterizationPretest characterization of thecounterface material shall include recording of fabricationvariables, such as composition, forming method (forging,casting, molding, etc.) and any postforming processing, such a
40、sannealing. Obtain data on material properties relevant to wear(for example, grain structure, hardness, and percentage ofcontaminants).6.4.2 Surface FinishIn tests that are intended to evaluatean alternate counterface material bearing against the standardUHMWPE, ensure that the counterface finish is
41、 appropriate forcomponents intended for clinical use. In test of alternatematerials where a reference metal or ceramic is used, polish thecounterface to the prosthesis quality.6.4.3 Ensure that cleaning of specimens produces a surfacefree of any particles, oils, greases, or other contaminants thatmi
42、ght influence the wear process.7. Procedure7.1 Make any initial measurements required to determinethe subsequent amount of wear of the polymeric specimen (seePractice F 2025 for the gravimetric measurement method).7.2 Place the control soak specimen(s) in a soak chamber oftest lubricant, such that t
43、he total surface area exposed to thelubricant is equal to that of the wear specimens when mountedin the test chambers. Maintain the soak chamber lubricanttemperature at the same nominal temperature as the testchambers. This temperature shall be 37 6 3C unless justifi-cation can be provided that use
44、of a different temperature willnot affect the results.7.3 Place the wear test specimens in their test chambers, addthe lubricant, and activate load(s) and motion(s).7.4 As testing is commenced, monitor the specimens forsigns of erratic behavior that might require early termination ofthe test.7.5 Rem
45、ove the wear and soak specimens at desired inter-vals, wash, rinse, concurrently in accordance with the proce-dure in Annex A6 (also defined in Practice F 2025). It isimportant that both the wear and soak components be treatedidentically to ensure that they have the same exposure to thewash, rinse,
46、and drying fluids. This will provide the mostaccurate correction for fluid sorption by the wear specimens,and correction for any other factors which could affect wearmeasurements.7.6 After rinsing and drying, conduct wear measurements.7.7 Thoroughly rinse all test assembly surfaces which havecontact
47、ed bovine serum using deionized water.7.8 Inspect the bearing surfaces of the test specimens andnote the characteristics of the wear process. Visual, micro-scopic, profilometric, replication, or other inspection tech-niques can be used. Care must be taken, however, that thesurfaces do not become con
48、taminated or damaged by anysubstance or technique that might affect the subsequent wearproperties. If contamination occurs, thoroughly reclean thespecimens prior to restarting the wear test.7.9 Replace the wear specimens, maintaining originalcouples and orientation, and soak control(s) in fresh lubr
49、icantand continue wear cycling.7.10 The appropriate wear test duration depends on theobjective of the specific test, the duration of run-in effects, thelinearity of wear rates, and the potential for wear mechanismtransitions. The minimum duration shall be two million wearcycles. The minimum number of wear measurements, subse-quent to the initial measurement shall be four.8. Report8.1 Materials:8.1.1 Provide material traceability information from a rawmaterial and fabrication or manufacturing standpoint for eachmaterial counterface. Examples of such information includemateri
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