1、Designation: F2025 06 (Reapproved 2012)Standard Practice forGravimetric Measurement of Polymeric Components forWear Assessment1This standard is issued under the fixed designation F2025; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a laboratory method using aweight-loss (that is, mass-loss; see X1.4) technique
3、 for evalu-ating the wear properties of polymeric materials or deviceswhich are being considered for use as bearing surfaces ofhuman joint replacement prostheses. The test specimens areevaluated in a device intended to simulate the tribologicalconditions encountered in the human joint; for example,
4、use ofa fluid such as bovine serum, or equivalent pseudosynovialfluid shown to simulate similar wear mechanisms and debrisgeneration found in vivo.2. Referenced Documents2.1 ASTM Standards:2D792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD1505 Test M
5、ethod for Density of Plastics by the Density-Gradient TechniqueF732 Test Method for Wear Testing of Polymeric MaterialsUsed in Total Joint ProsthesesF1714 Guide for Gravimetric WearAssessment of ProstheticHip Designs in Simulator Devices2.2 Other Standards:3ISO 142422 Implants for SurgeryWear ofTota
6、l Hip-JointProsthesesPart 2: Methods of MeasurementISO 142432 Implants for SurgeryWear of Total Knee-Joint ProsthesesPart 2: Methods of Measurement3. Significance and Use3.1 This practice uses a weight-loss method of wear deter-mination for the polymeric components or materials used inhuman joint pr
7、ostheses, using serum or demonstrated equiva-lent fluid for lubrication, and running under a load profilerepresentative of the appropriate human joint application(1,2).4The basis for this weight-loss method for wear mea-surement was originally developed (3) for pin-on-disk wearstudies (Practice F732
8、) and has been extended to total hipreplacements (4, 5, ISO 142422, and Guide F1714), and tofemoro-tibial knee prostheses (6 and ISO 142432), and tofemoro-patellar knee prostheses (6,7).3.2 While wear results in a change in the physical dimen-sions of the specimen, it is distinct from dimensional ch
9、angesdue to creep or plastic deformation, in that wear results in theremoval of material in the form of polymeric debris particles,causing a loss in weight of the specimen.3.3 This practice for measuring wear of the polymericcomponent is suitable for various simulator devices. Thesetechniques can be
10、 used with metal, ceramic, carbon, polymeric,and composite counter faces bearing against a polymericmaterial (for example, polyethylene, polyacetal, and so forth).Thus, this weight-loss method has universal application forwear studies of human joint replacements which featurepolymeric bearings. This
11、 weight-loss method has not beenvalidated for non-polymeric material bearing systems, such asmetal-metal, carbon-carbon, or ceramic-ceramic. Progressivewear of such rigid bearing combinations has generally beenmonitored using linear, variable-displacement transducers, orby other profilometric techni
12、ques.4. Components and Materials4.1 Hip Prosthesis ComponentsThe hip joint prosthesiscomprises a ball-and-socket configuration in which materialssuch as polymers, composites, metal alloys, ceramics, andcarbon have been used in various combinations and designs.4.1.1 Component ConfigurationsThe diamet
13、er of theprosthetic ball may vary from 22 to 54 mm or larger. Thedesign may include ball-socket, trunnion, bipolar, or otherconfigurations. If applicable, the normal metal backing for thepolymeric component shall be used provided disassembly andreassembly of these components for the measurement does
14、 not1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Aug. 15, 2012. Published September 2012. Originallyapproved in 2000. Last previous edition ap
15、proved in 2006 as F2025 06. DOI:10.1520/F2025-06R12.2For 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.3Availabl
16、e from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United
17、 States1have an unrepresentative effect on the weight measurements orwear behavior. Otherwise, a modified backing may be used,again provided this has no unrepresentative effect on theweight measurements or wear behavior (see X1.5).4.2 Knee Prosthesis ComponentsThe knee joint comprisesfemoral, tibial
18、, and patellar configurations in which materialssuch as metal alloys, ceramics, polymers, and carbon materialshave been used in various combinations in different designs.4.2.1 Component ConfigurationsThe polymeric compo-nents may be backed by either metal, ceramic, or compositereinforcements. If app
19、licable, the normal metal backing shallbe used provided disassembly and reassembly of these com-ponents for the measurement does not have an unrepresentativeeffect on the weight measurements or wear behavior.Otherwise, a modified backing may be used, again providedthis has no unrepresentative effect
20、 on the weight measurementsor wear behavior (see X1.5).4.3 Other prosthesis components and test coupons may beused to represent other human joint replacement applications.5. Specimen Preparation5.1 Polymers and CompositesMaterial Condition:5.1.1 A fabrication history shall be obtained for each poly-
21、meric or composite component, including information such asgrade, batch number and processing variables, method offorming (extruding, molding, and so forth), temperature, pres-sure and forming time used, and any post-forming treatments,including the sterilization method and parameters.5.1.2 Pretest
22、characterization may include measurement ofbulk material properties such as molecular-weight range anddistribution, percent crystallinity, or other. Density is a particu-larly important property because of the conversion of weightmeasurements to volumetric wear (see 7.4). Density measure-ments shall
23、 be obtained in accordance with Test Methods D792or Test Method D1505. If it can be justified that previousdensity measurements are representative of the material used inthe current wear test, reference to these previous measurementsand suitable justification shall be provided (see also X1.6). Thesu
24、rface finish of specimens may be characterized byprofilometry, photomicrography, and replication by variousplastics or other techniques.5.1.3 SterilizationThe components shall be sterilized in amanner typical of that in clinical use for such devices, as thismay affect the wear properties of the mate
25、rials. Sterilization ofall test and control components within a specific test groupshould be done simultaneously (in a single container) whenpossible to minimize variation among the specimens. The weartesting procedure makes no attempt to maintain the sterility ofspecimens during the wear test.5.2 P
26、olymer Specimen Cleaning ProcedurePrior toweighing and wear testing, careful cleaning of the polymerspecimens is important to remove any contaminants that wouldnot normally be present on the actual prosthesis. During thewear test, the components must be re-cleaned and dried beforeeach weighing to re
27、move any extraneous material that mightaffect the accuracy of the weighing. The procedure for cleaningand drying of polymeric components is given in Annex A1.With some combinations of materials, wear may result in thetransfer of particulate debris which may then become re-imbedded or otherwise attac
28、hed to polymeric, metal, or com-posite surfaces. Such an occurrence will render the weight-lossassessment of wear less reliable.5.3 Polymer Specimen Weighing ProcedureThe polymericcomponents shall be weighed on an analytical balance havinga sensitivity on the order of 10 g. This degree of sensitivit
29、y isnecessary to detect the slight loss in weight of polymers suchas ultra-high-molecular-weight polyethylene (UHMWPE),which may wear 1 mg or less per million cycles. Specimensshall always be weighed in the clean, dry condition (AnnexA1). The components shall be kept in a dust-free container andhand
30、led with clean tools to prevent contamination which mightaffect the weight measurement. Each wear and control compo-nent shall be weighed three times in rotation to detect randomerrors in the weighing process.5.4 Pre-Soaking of Test Specimens:5.4.1 Polymeric and composite components made frommateria
31、ls which absorb fluid initially, but saturate within a fewweeks, should be presoaked in the test lubricant to reduce theerror due to fluid sorption during the wear run. If the fluidsorption behavior of a particular material is unknown, theinvestigator shall conduct a preliminary study to determinewh
32、ether or not the material is exempt from presoaking.5.4.2 Preliminary StudyA minimum of three soak speci-mens (these can be test coupons or actual devices) per materialshall be cleaned and dried in accordance with the procedure inAnnex A1, and then weighed by precisely controlled andrepeatable metho
33、ds (Annex A1). The specimens shall then beplaced in a container of test lubricant and removed, cleaned,dried, and weighed (in accordance with Annex A1) once ortwice a week. The weight change shall be calculated inaccordance with Annex A1. The procedure shall be repeateduntil the specimens have soake
34、d for five weeks. Specimenweight change shall be averaged at each interval and plottedversus time. Data points shall be fit using a second or thirdorder polynomial or hyperbolic function, connecting throughzero. The fit of this curve should have an R2value of 0.8 orgreater. If the slope of this curv
35、e at five weeks is ten or moretimes less than the slope of the curve at zero (see X1.7), thenthis material shall be subjected to presoaking before weartesting (if gravimetric wear measurement is to be used).Otherwise, it is exempt.NOTE 1Even if presoaking is not required, one to three soak controlco
36、mponents are still necessary per material condition to account for fluidsorption by the wear components during the wear test.5.4.3 Pre-soaking Procedure (if Required)After fabrica-tion and characterization, the wear components and one tothree soak-control components of each test material shall becle
37、aned in accordance with the procedure in Annex A1. Thewear components and soak control(s) shall then be placed in acontainer of test lubricant for a minimum of five weeks (35days).6. Measurement Procedure6.1 After fabrication, characterization, and the completionof the presoak period (if required),
38、the wear components andF2025 06 (2012)2soak control(s) should be cleaned, dried, and weighed byprecisely controlled and repeatable methods (Annex A1).These weights shall be recorded as the initial weights of thespecimens for purposes of calculating the progressive weightloss during the wear test. Th
39、e soak control specimen(s) shall beplaced in holders in a soak chamber of test lubricant, such thatthe total surface area exposed to the lubricant is equal to that ofthe wear components when mounted in the test chamber. Thesoak chamber temperature shall be maintained at the sametemperature as the bu
40、lk lubricant in the wear test, or specifiedif different. It is recommended that the soak chamber beattached to the test machine or otherwise agitated in the samemanner as the actual wear chambers. In addition, it may beadvantageous to apply a cyclic load to the soak controlspecimen(s) (without tange
41、ntial motion) comparable to thatapplied to the wear specimens, since this can also affect the rateof fluid sorption.6.2 The wear and soak component(s) shall be removed atspecified intervals, washed, rinsed, and dried concurrently, inaccordance with the procedure in Annex A1. It is importantthat both
42、 the wear and soak component(s) be treated identicallyto ensure that they have the same exposure to the wash, rinse,and drying fluids. This will provide the most accurate correc-tion for fluid sorption by the wear specimens.6.3 After rinsing and drying, the wear components and soakcontrols shall be
43、weighed on an analytical balance in accor-dance with 5.3.6.4 The wear chambers and component surfaces shall bethoroughly rinsed with distilled or deionized water.6.5 The bearing surfaces of the components shall beinspected, and the characteristics of the wear process noted.Visual, microscopic, profi
44、lometric, replication, or other inspec-tion techniques can be used. However, care must be taken thatthe surfaces do not become contaminated or damaged by anysubstance or technique which might affect the subsequent wearproperties. If contamination occurs, the specimens shall bethoroughly re-cleaned p
45、rior to restarting the wear test.6.6 The wear components and soak control(s) shall bereplaced in fresh lubricant and wear cycling continued.7. Determination of Wear Rates7.1 Test LengthThe accuracy of the test method dependson the relative magnitudes of wear and fluid sorption. This isespecially tru
46、e when the fluctuations in the weight due tovariation in the amount of surface drying are large in compari-son to the incremental weight loss due to wear. For high-wearlow-sorption materials, the wear rate may be clearly estab-lished in as few as 50 000 wear cycles. With comparativelylow-wearing mat
47、erials, such as UHMWPE, several millioncycles or more may be required to clearly establish thelong-term wear properties.7.2 Number of Measurements per TestWhen specimenscan be removed for intermediate weight measurement, at leastthree measurements per test series shall be made.7.3 Correcting for Flu
48、id SorptionThe average gain (orloss) of the soak control component(s) shall be added to (orsubtracted from) the measured weight loss of each wearcomponent (Annex A2.6). This procedure corrects both forsystematic sorption as well as random differences in theamount of surface drying (of the entire set
49、 of test and controlspecimens) and balance fluctuations due to environmental orother variables at each interval of weighing.7.4 Conversion to Volumetric WearIn tests where the wearrates of materials with different densities are evaluated, it maybe preferable to compare these on the basis of volumetric wear,rather than weight loss. The volumetric wear rate may beobtained by dividing the weight loss data by the density of thematerial, in appropriate units. The accuracy of this calculationis dependent on the material being reasonably homogeneous(that is, having
