1、Designation: F732 00 (Reapproved 2011)Standard 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 revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () 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 mat
3、erialsthat 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 tailor
4、ed 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 recognize
5、d, 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 using
6、 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 joint
7、 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.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as s
8、tandard. The 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.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsF
9、75 Specification 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 ImplantsF648 Specification for Ultra-High-Molecular-Weight Poly-ethylene Powder and Fabricated Form for Surgica
10、l Im-plantsF799 Specification for Cobalt-28Chromium-6MolybdenumAlloy Forgings for Surgical Implants (UNS R31537,R31538, R31539)F1537 Specification for Wrought Cobalt-28Chromium-6MolybdenumAlloys for Surgical Implants (UNS R31537,UNS R31538, and UNS R31539)F2025 Practice for Gravimetric Measurement o
11、f 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 pro-gressive loss of material from the polymer specimen as a resultof the oscillating motion agains
12、t the counterface under load.Wear may be generated 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 i
13、n a non-uniform slidingdistance across the specimen; see 4.3).1This 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 Material Test Methods.Current edition approved June 1, 2011. Publishe
14、d July 2011. Originally approvedin 1982. Last previous edition approved in 2006 as F732 00 (2006). DOI:10.1520/F0732-00R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
15、fer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Significance and Use4.1 This test method is intended to be performed in con-junction with pin-on-flat wear machines or s
16、imilar machinesthat are designed to evaluate simplified specimen geometries.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, sign
17、ificant wear ofthe counterface may 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 fun
18、ction of sliding distance; however, 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
19、polymer specimen is determined by dividing 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-dat
20、e materials shall be the wear rate 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 b
21、ovine blood serum (see 5.2).5. Apparatus 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 wea
22、r appli-cations, refer to Annex A3.NOTE 1Other types of applications 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
23、 differ in compo-sition (protein concentration, etc.), dilution with 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 poole
24、d serumshould be used since the former is less likely to containhemolyzed 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 t
25、he speci-mens being tested.5.2.3 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,
26、 or by recirculating thelubricant in a sealed environment.5.2.4 To retard 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 b
27、acte-rial degradation.NOTE 2Sodium azide is a poison and must be handled 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 be
28、aring surfaces.The latter event has been shown to strongly affect 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.
29、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 interval. The maxi-mum rep
30、lacement 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 bovine serum. In suchcase th
31、e lubricant shall be specified in the test report.6. Preparation of 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 prope
32、rties 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 information such as grade,batch number, and processing variables, including method offorming (extruding, molding, etc.), temperature
33、, pressure, andforming time used, articulation surface preparation 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,
34、density, or others. The sur-face finish of specimens may be characterized by profilometry,photomicrography, replication by various plastics, or othertechniques.3The boldface numbers in parentheses refer to a list of references at the end ofthis test method.F732 00 (2011)26.2.3 SterilizationSterilize
35、 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 testand control specimens wit
36、hin 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 wear test-ing, careful cleaning of the polymer specimens is important toremove any contaminants that would not normally
37、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 the accuracyof the measurement. The required procedure for cleaning anddrying of polymeric specimens, as defined in Pract
38、ice F2025,isgiven 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 polymers such as UHMWPE could sh
39、owa net increase in weight or volume during the initial wearintervals 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).Am
40、inimum 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 composition, forming method (forging
41、,casting, molding, etc.) and any postforming processing, such asannealing. 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 ag
42、ainst 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 cleaning of specimens produces a surfacefre
43、e 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 so
44、ak 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 lubricanttemperature at the same nominal temperature as the testchambers. This temperature sh
45、all be 37 6 3C unless justifi-cation can be provided that use 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 be
46、havior that might require early termination ofthe test.7.5 Remove 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 F2025). It isimportant that both the wear and soak components be treatedidentically t
47、o ensure that they have the same exposure to thewash, rinse, 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
48、Thoroughly rinse all test assembly surfaces which havecontacted 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. Ca
49、re must be taken, however, that thesurfaces do not become contaminated 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 lubricantand 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 mechanismtra
