1、Designation: F 1714 96 (Reapproved 2008)Standard Guide forGravimetric Wear Assessment of Prosthetic Hip Designs inSimulator Devices1This standard is issued under the fixed designation F 1714; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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 guide describes a laboratory method using aweight-loss technique for evaluating the wear pro
3、perties ofmaterials or devices, or both, which are being considered foruse as bearing surfaces of human-hip-joint replacement pros-theses. The hip prostheses are evaluated in a device intended tosimulate the tribological conditions encountered in the humanhip joint, for example, use of a fluid such
4、as bovine serum, orequivalent pseudosynovial fluid shown to simulate similarwear mechanisms and debris generation as found in vivo, andtest frequencies of 1 Hz or less.1.2 Since the hip simulator method permits the use of actualimplant designs, materials, and physiological load/motioncombinations, i
5、t can represent a more physiological simulationthan basic wear-screening tests, such as pin-on-disk (seePractice F 732) or ring-on-disk (see ISO 6474).1.3 It is the intent of this guide to rank the combination ofimplant designs and materials with regard to material wear-rates, under simulated physio
6、logical conditions. It must berecognized, however, that there are many possible variations inthe in vivo conditions, a single laboratory simulation with afixed set of parameters may not be universally representative.1.4 The reference materials for the comparative evaluationof candidate materials, ne
7、w devices, or components, or acombination thereof, shall be the wear rate of extruded orcompression-molded, ultra-high molecular weight (UHMW)polyethylene (see Specification F 648) bearing against standardcounter faces stainless steel (see Specification F 138); cobalt-chromium-molybdenum alloy (see
8、Specification F75); ther-momechanically processed cobalt chrome (see SpecificationF 799); alumina ceramic (see Specification F 603), havingtypical prosthetic quality, surface finish, and geometry similarto those with established clinical history. These referencematerials will be tested under the sam
9、e wear conditions as thecandidate materials.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating 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 Me-t
10、allic Surgical ImplantsF 136 Specification for Wrought Titanium-6Aluminum-4Vanadium ELI (Extra Low Interstitial) Alloy for SurgicalImplant Applications (UNS R56401)F 138 Specification for Wrought 18Chromium-14Nickel-2.5Molybdenum Stainless Steel Bar and Wire for SurgicalImplants (UNS S31673)F 370 Sp
11、ecification for Proximal Femoral Endoprosthesis3F 565 Practice for Care and Handling of Orthopedic Im-plants and InstrumentsF 603 Specification for High-Purity Dense Aluminum Ox-ide for Medical ApplicationF 648 Specification for Ultra-High-Molecular-Weight Poly-ethylene Powder and Fabricated Form fo
12、r Surgical Im-plantsF 732 Test Method for Wear Testing of Polymeric MaterialsUsed in Total Joint ProsthesesF 799 Specification for Cobalt-28Chromium-6MolybdenumAlloy Forgings for Surgical Implants (UNS R31537,R31538, R31539)G 40 Terminology Relating to Wear and Erosion2.2 ISO Standard:ISO 6474 Impla
13、nts for SurgeryCeramic Materials Basedon Alumina43. Significance and Use3.1 This guide uses a weight-loss method of wear determi-nation for the polymeric components used with hip joint1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the
14、direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 1996. Last previous edition approved in 2002 as F 1714 96 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
15、 Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM
16、International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.prostheses, using serum or demonstrated equivalent fluid forlubrication, and running under a dynamic load profile repre-sentative of the human hip-joint forces during walking (1,2).5The basis for this
17、weight-loss method for wear measurementwas originally developed (3) for pin-on-disk wear studies (seePractice F 732) and has been extended to total hip replace-ments (4,5) femoral-tibial knee prostheses (6), and to femoro-patellar knee prostheses (6,7).3.2 While wear results in a change in the physi
18、cal dimen-sions of the specimen, it is distinct from dimensional changesdue to creep or plastic deformation, in that wear generallyresults in the removal of material in the form of polymericdebris particles, causing a loss in weight of the specimen.3.3 This guide for measuring wear of the polymeric
19、com-ponent is suitable for various simulator devices. These tech-niques can be used with metal, ceramic, carbon, polymeric, andcomposite counter faces bearing against a polymeric material(for example, polyethylene, polyacetal, and so forth). Thisweight-loss method, therefore, has universal applicati
20、on forwear studies of total hip replacements that feature polymericbearings. This weight-loss method has not been validated forhigh-density material bearing systems, such as metal-metal,carbon-carbon, or ceramic-ceramic. Progressive wear of suchrigid bearing combinations generally has been monitored
21、 usinga linear, variable-displacement transducers or by other profilo-metric techniques.4. Apparatus 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
22、 used in various combinations and designs.4.2 Component ConfigurationsThe diameter of the pros-thetic ball may vary from 22 to 54 mm or larger. The designmay include ball-socket, trunnion, bipolar, or other configura-tions.4.3 Hip Simulator:4.3.1 Test ChambersIn the case of a multi-specimenmachine,
23、contain the components in individual, isolated cham-bers to prevent contamination of one set of components withdebris from another test. Ensure that the chamber is madeentirely of noncorrosive materials, such as acrylic plastic orstainless steel, and is easily removable from the machine forthorough
24、cleaning between tests. Design the wear chamberssuch that the test bearing surfaces are immersed in the lubricantthroughout the test (3,7).4.3.2 Component Clamping FixturesSince wear is to bedetermined from the weight-loss of the components, themethod for mounting the components in the test chambers
25、hould not compromise the accuracy of assessment of theweight-loss due to wear.4.3.3 LoadEnsure that the test load profile is representa-tive of that which occurs during the patients walking cycle,with peak hip-loads$2kN(2). The loading apparatus shall befree to follow the specimen as wear occurs, so
26、 that the appliedload is constant to within 63 % for the duration of the test.Never allow the applied load to be below that required to keepthe chambers seated (for example, 50 N) (4).4.3.4 MotionEnsure that relative motion between the hipcomponents oscillates and simulates the flexion-extension arc
27、of walking. Addition of internal-external or abduction-adduction arcs is at the investigators discretion. It is recom-mended that the orientations of the cup and ball relative to eachother and to the load-axis be maintained by suitable specimen-holder keying.4.3.5 Oscillating FrequencyOscillate the
28、hip prostheses ata rate of one cycle per second (1 Hz).4.3.6 Cycle CounterInclude a counter with the hip-simulator to record the total number of wear cycles.4.3.7 FrictionIt is recommended that the machine includesensors capable of monitoring the friction forces transmittedacross the bearing surface
29、s during the wear test.4.4 Lubricant:4.4.1 It is recommended that the specimen be lubricatedwith bovine blood serum; however, another suitable lubricationmedium may be used if validated.4.4.2 If serum is used, use filtered-sterilized serum ratherthan pooled serum since the former is less likely to c
30、ontainhemolyzed blood material, which has been shown to adverselyaffect the lubricating properties of the serum (3). Dilutedsolutions of serum have also been used for this purpose (8).Filtration may remove hard, abrasive, particulate contaminantsthat might otherwise affect the wear properties of the
31、 speci-mens being tested.4.4.3 Maintain the volume and concentration of the lubri-cant nearly constant throughout the test. This may be accom-plished by sealing the chambers so that water does notevaporate, or periodically or continuously replacing evaporatedwater with distilled water.4.4.4 To retar
32、d bacterial degradation, freeze and store theserum until needed for the test. In addition, ensure that the fluidmedium in the test contains 0.2 % sodium azide (or othersuitable antibiotic) to minimize bacterial degradation. Otherlubricants should be evaluated to determine appropriate storageconditio
33、ns.4.4.5 It is recommended that ethylene-diaminetetraaceticacid (EDTA) be added to the serum at a concentration of 20mM to bind calcium in solution and minimize precipitation ofcalcium phosphate onto the bearing surfaces. The latter eventhas been shown to strongly affect the friction and wearpropert
34、ies, particularly of polyethylene/ceramic combinations.The addition of EDTA to other lubricant mediums should beevaluated.4.4.6 A lubricant other than bovine serum may be used if itcan be shown that its lubricating properties and, therefore,material wear properties are reasonably physiological (8).I
35、nsuch a case, specify the lubricant in the test report.4.5 Hold the bulk temperature of the lubricant at 37 6 3Cor as specified, if different.5. Specimen Preparation5.1 The governing rule for preparation of componentcounter faces is that the fabrication process parallels that usedor intended for use
36、 in the production of actual prostheses, in5The boldface numbers in parentheses refer to the list of references at the end ofthis standard.F 1714 96 (2008)2order to produce a specimen with comparable bulk materialproperties and surface characteristics (see Practice F86).5.2 Polymers and Composites:5
37、.2.1 Obtain a fabrication history for each polymeric orcomposite component, including information such as grade,batch number, and processing variables, including method offorming (extruding, molding, and so forth), temperature, pres-sure, and forming time used, and any post-forming treatments,includ
38、ing sterilization.5.2.2 Pretest characterization may include measurement ofbulk material properties, such as molecular-weight range anddistribution, percent crystallinity, density, or other. The surfacefinish of specimens may be characterized by profilometry,photomicrography, replication by various
39、plastics, or othertechniques.5.2.3 SterilizationSterilize the components in a mannertypical of that in clinical use for such devices, including totaldose and dose rate, as these may affect the wear properties ofthe materials. Report these processing parameters with theaging time prior to each test w
40、hen known. Sterilization of alltest and control components within a specific test group shouldbe done simultaneously (in a single container), when possible,to minimize variation among the specimens. This wear-simulation procedure makes no attempt to maintain the sterilityof specimens during the wear
41、 test.5.2.4 Cleaning of Polymer ProsthesesPrior to wear test-ing, careful cleaning of the polymer specimens is important toremove any contaminants that would not normally be presenton the actual prosthesis. During the wear run, the componentsmust be re-cleaned and dried before each weighing to remov
42、eany extraneous material that might affect the accuracy of theweighing. A suggested procedure for cleaning and drying ofpolymeric components is given in Annex A4. With somecombinations of materials, wear may result in the transfer ofparticulate debris which may then become re-imbedded orotherwise at
43、tached to polymeric, metal, or composite surfaces.Such an occurrence will render the weight-loss assessment ofwear less reliable.5.2.5 Weighing of Polymeric ComponentsWeigh the poly-meric components on an analytical balance having an accuracyon the order of 610 g. This degree of sensitivity is neces
44、saryto detect the slight loss in weight of polymers, such as UHMWpolyethylene, which may wear 30 mg or less per million cycles(3,5).Always weigh specimens in the clean, dry condition (seeAnnex A1). Keep the components in a dust-free container andhandle with clean tools to prevent contamination that
45、mightaffect the weight measurement. Weigh each wear and controlcomponent three times in rotation to detect random errors inthe weighing process.5.3 Soaking of Polymeric and Composite Prostheses:5.3.1 Polymeric and composite components should be pre-soaked in the lubricant to minimize fluid sorption
46、during thewear run. Without presoaking, components of very low-wearpolymers such as polyethylene may show a net increase inweight during the initial wear intervals, due to fluid sorption(3,4). The error due to fluid sorption can be reduced throughpresoaking and the use of control soak specimens. The
47、 numberof specimens required and the length of presoaking depends onthe variability and magnitude of fluid sorption encountered (4).5.3.2 After fabrication and characterization, clean and drythe wear components and three soak-control components ofeach test material in accordance with Annex A4, and t
48、henweigh by precisely controlled and repeatable methods. Placethe wear components and soak controls in a container of serumfor a specified time interval. Then, remove, clean, dry, andreweigh the components, and calculate the weight-loss (seeAnnex A4). Repeat the specimens until a steady rate offluid
49、-sorption has been established. The number of weighingswill depend on the amount of fluid sorption exhibited by thespecimens.5.3.3 In general, the weight of the components will stabilizeat an asymptotic value in a reasonable time period. WithUHMW polyethylene, a presoak period of 30 days has beenfound adequate (4,7). In any case, use the weight-gain of thesoak controls to correct for ongoing fluid sorption by the wearcomponents during the wear test.5.4 Counterfaces of Metal Alloys, Ceramic, or Other Mate-rials:5.4.1 CharacterizationInclude with the pretest chara
