ASTM F732-17 Standard Test Method for Wear Testing of Polymeric Materials Used in Total Joint Prostheses.pdf

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1、Designation: F732 17Standard Test Method forWear Testing of Polymeric Materials Used in Total JointProstheses1This standard is issued under the fixed designation F732; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of las

2、t revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () 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 materialsthat are being c

3、onsidered 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 tailored to eachdistinct wea

4、r application (for example, linear reciprocatingmotion, ball-cup (“hip-type”) wear, delamination wear, and soforth). It is the intent of this test method to rank materials,within each wear application, for polymer wear rates undersimulated physiological conditions. It must be recognized,however, tha

5、t contact geometries and wear motions are sim-plified using such methods. This test method, therefore, repre-sents only an initial stage in the full wear characterization of acandidate material.1.2 All candidate materials should be tested in an appropri-ate joint simulator apparatus using prototype

6、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 joint simulator

7、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.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. Th

8、e values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This international standard was developed in accor-dance with internationally recognized

9、 principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating

10、to PlasticsF75 Specification for Cobalt-28 Chromium-6 MolybdenumAlloy Castings and Casting Alloy for Surgical Implants(UNS R30075)F86 Practice for Surface Preparation and Marking of Metal-lic Surgical ImplantsF648 Specification for Ultra-High-Molecular-Weight Poly-ethylene Powder and Fabricated Form

11、 for Surgical Im-plantsF799 Specification for Cobalt-28Chromium-6MolybdenumAlloy Forgings for Surgical Implants (UNS R31537,R31538, R31539)F1537 Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNSR31537, UNS R31538, and UNS R31539)F2025 Practice for Gravimetric

12、Measurement of PolymericComponents for Wear AssessmentG40 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 progres-sive loss of material from the polymer specimen as a result ofthe oscillating

13、motion against the counterface under load. Wearmay be generated by several mechanisms including adhesion,two or three body abrasion, surface fatigue, or other processes.3.1.2 wear ratethe volume of material lost due to wear perunit of sliding distance (or per million wear cycles if complexmotion pat

14、terns result in a non-uniform sliding distance acrossthe specimen; see 4.3).1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Sept. 1,

15、2017. Published October 2017. Originallyapproved in 1982. Last previous edition approved in 2011 as F732 00 (2011).DOI: 10.1520/F0732-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume i

16、nformation, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardi

17、zation established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14. Significance and Use4.1 This test method is intended to be performed in con-junction with

18、pin-on-flat wear machines or similar machinesthat are designed to evaluate simplified specimen geometries.NOTE 1See Haider & Baykal (1)3for useful considerations andpotential pitfalls in conducting pin on disk testing, interpreting test resultsand the complex and sometimes conflicting effects of low

19、er stress andhigher contact area on wear.4.2 This test method is designed to evaluate combinations ofmaterials with respect 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

20、occur, with subsequent embedding ofcounterface debris particles in the polymer. Such an occurrencewill render the weight loss 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,

21、 if thesliding distance is not constant across the polymeric specimensurface due to complex motion patterns, wear may be reportedas 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 d

22、ividing theexperimental weight loss 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

23、of ultra-high-molecular-weight polyethylene (UHMWPE) conforming to SpecificationF648 bearing against counterfaces of cobalt-chromium-molybdenum alloy (in accordance with Specifications F75,F799,orF1537), having prosthetic-quality surface finish andlubricated with bovine blood serum (see 5.2).5. Appa

24、ratus and Materials5.1 Orthopaedic 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 wearapplications, refer to Annex A3.NO

25、TE 2Other types of applications may be addressed in laterrevisions.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 concen

26、tration, and so forth), dilution withdeionized water of up to 75 % (volume fraction) may beappropriate. The appropriate dilution shall be based on satis-faction of the clinical validation criteria in the appropriateannex.5.2.2 A filter-sterilized serum rather than pooled serumshould be used since th

27、e former is less likely to containhemolyzed blood material, which has been shown to adverselyaffect the lubricating properties of the serum (2). Serum mustbe filtered to remove hard, abrasive, particulate contaminantsthat might otherwise affect the wear properties of the speci-mens being tested.5.2.

28、3 Maintain the volume, concentration, 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 thelubrica

29、nt in a sealed environment.5.2.4 To retard bacterial degradation, freeze and store theserum between -10 and -40 C until it is used for testing. Priorto testing, it is recommended, but not mandatory, that a suitableantibacterial agent be added at an appropriate volume fraction.A commonly used antibac

30、terial agent is sodium azide. Ifsodium azide is used, it is recommended to use a volumefraction of 0.11 to 0.16 % (mass fraction of 0.2 to 0.3 %). Thevolume and mass fractions of the antibacterial agent referencesthe volume and mass of the final test solution which may bediluted or undiluted serum.N

31、OTE 3Sodium azide is a poison and must be handled very carefully.NOTE 4It has been shown that the addition of sodium azide mayreduce wear, and sodium azide may not inhibit all types of bacterialgrowth (3).5.2.5 It is recommended, but not mandatory, that ethylene-diaminetetraacetic acid (EDTA) be add

32、ed to the serum at aconcentration of 20 mM 7.45 g/L to bind calcium in solutionand minimize precipitation of calcium phosphate onto thebearing surfaces. The latter event has been shown to stronglyaffect the friction and wear properties, particularly ofpolyethylene/ceramic combinations (4). The molar

33、 concentra-tion of the EDTA references the volume of the final testsolution which may be diluted or undiluted serum.NOTE 5There are multiple forms of EDTA commonly available, suchas pure EDTA, EDTA dipostassium salt dihydrate, and so forth. All ofthese compounds have different molecular weights, and

34、 a different amountof each compound is required to achieve the same EDTA concentration.Pure EDTA has a very low solubility in water, and EDTA disodium saltdihydrate is recommended.5.2.6 Additives such as sodium azide and EDTA shall bedissolved in deionized water and passed through a 0.2-m filterbefo

35、re adding to bovine serum.5.2.7 The appropriate interval for replacing used serumdepends on 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

36、interval. The maxi-mum replacement interval is two weeks. The selected intervalmust meet the 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 bo

37、vine serum. In suchcase the lubricant shall be specified in the test report.3The boldface numbers in parentheses refer to a list of references at the end ofthis test method.F732 1726. Preparation of Specimens6.1 The governing rule for specimen preparation is that thefabrication process parallels tha

38、t 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 and Composites:6.2.1 Obtain a fabrication history for each polymeric orcomposite specimen, including i

39、nformation such as grade,batch number, and processing variables, including method offorming (extruding, molding, and so forth), temperature,pressure, and forming time used, articulation surface prepara-tion methods (see AnnexA5) and any post-forming treatments,including sterilization.6.2.2 Pre-test

40、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 characterized by profilometry,photomicrography, replication by various plastics, or othertechniques.

41、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 processing parameters with theaging time prior to each test, if known. Sterilization of all t

42、estand 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 to weartesting, careful cleaning of the polymer specimens is importantto remove any contaminant

43、s that would not normally bepresent on an actual prosthesis. During the wear test, thespecimens must be re-cleaned and dried before each wearmeasurement to remove any extraneous material that mightaffect the accuracy of the measurement. The required proce-dure for cleaning and drying of polymeric sp

44、ecimens, asdefined in Practice F2025, is given in Annex A6.6.3 Soaking of Polymeric and Composite Specimens:6.3.1 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 pol

45、ymers such as UHMWPE could showa net increase in weight or volume during the initial wearintervals due to fluid sorption (2, 5). 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 flui

46、d sorption encountered (5).Aminimum of one control soak specimen per material conditionis required.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 composi

47、tion, forming method (forging,casting, molding, and so forth) and any postformingprocessing, such as annealing. Obtain data on material prop-erties relevant to wear (for example, grain structure, hardness,and percentage of contaminants).6.4.2 Surface FinishIn tests that are intended to evaluatean al

48、ternate counterface material bearing against the standardUHMWPE, ensure that the counterface finish is 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 clea

49、ning of specimens produces a surfacefree of any particles, oils, greases, or other contaminants thatmight influence the wear process.7. Procedure7.1 Make any initial measurements required to determinethe subsequent amount of wear of the polymeric specimen (seePractice F2025 for the gravimetric measurement method).7.2 Place the control soak specimen(s) in a soak chamber oftest lubricant, such that the total surface area exposed to thelubricant is equal to that of the wear specimens when mountedin the test chambers. Maintain the soak chamber lubricanttemperatu