1、Designation: F 1714 96 (Reapproved 2002)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 (e) 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 pr
3、operties 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,
5、it 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 physi
6、ological 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, n
7、ew 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 F 75); 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 s
9、ame wear conditions as thecandidate materials.2. Referenced Documents2.1 ASTM Standards:D 883 Terminology Relating to Plastics2F 75 Specification for Cast Cobalt-Chromium-MolybdenumAlloy for Surgical Implant Applications3F 86 Practice for Surface Preparation and Marking of Me-tallic Surgical Implant
10、s3F 136 Specification for Titanium 6A1-4V ELI Alloy forSurgical Implant Applications3F 138 Specification for Stainless Steel Bar and Wire forSurgical Implants (Special Quality)3F 370 Specification for Proximal Femoral Prosthesis3F 565 Practice for Care and Handling of Orthopedic Im-plants and Instru
11、ments3F 603 Specification for High-Purity Dense Aluminum Ox-ide for Surgical Implant Application3F 648 Specification for Ultra-High-Molecular-Weight Poly-ethylene Powder and Fabricated Form for Surgical Im-plants3F 732 Practice for Pin-on-Flat Evaluation of Friction andWear Properties of Polymeric M
12、aterials for Use in TotalJoint Prostheses3F 799 Specification for Thermomechanically ProcessedCobalt-Chrome-Molybdenum Alloy for Surgical Implants3G 40 Terminology Relating to Erosion and Wear42.2 ISO Standard:ISO 6474 Implants for SurgeryCeramic Materials Basedon Alumina53. Significance and Use3.1
13、This guide uses a weight-loss method of wear determi-nation for the polymeric components used with hip-jointprostheses, using serum or demonstrated equivalent fluid for1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsib
14、ility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Sept. 10, 1996. Published October 1996.2Annual Book of ASTM Standards, Vol 08.01.3Annual Book of ASTM Standards, Vol 13.01.4Annual Book of ASTM Standards, Vol 03.02.5Available from American National Standards Institute, 25 W. 43rd
15、St., 4thFloor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.lubrication, and running under a dynamic load profile repre-sentative of the human hip-joint forces during walking (1,2).6The basis for this weight-los
16、s 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) and to femoral-tibial knee prostheses (6), and tofemoropatellar knee prostheses (6,7).3.2 While wear results in a change in the physical d
17、imen-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 com-p
18、onent 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 application fo
19、rwear 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 usin
20、ga 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 used
21、 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, conta
22、in 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 clean
23、ing 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 chambershould
24、 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 must befree to follow the specimen as wear occurs, such th
25、at theapplied load is constant to within 63 % for the duration of thetest. Never allow the applied load to be below that required tokeep the chambers seated (for example, 50 N) (4).4.3.4 MotionEnsure that relative motion between the hipcomponents oscillates and simulates the flexion-extension arcof
26、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 hip
27、 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-surfaces d
28、uring 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, then use filtered-sterilized serumrather than pooled serum since the former is less likely to
29、contain hemolyzed blood material, which has been shown toadversely affect the lubricating properties of the serum (3).Diluted solutions of serum also have been used for this purpose(8). Filtration may remove hard, abrasive, particulate contami-nants that might otherwise affect the wear properties of
30、 thespecimens 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 ret
31、ard bacterial degradation, freeze and store theserum until needed for 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 storageconditions
32、.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 wearpropertie
33、s, 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 usedwhen it can be shown that its lubricating properties and,therefore, material wear properties are reasonably physiologi-cal (8).
34、 In such a case, specify the lubricant in the test report.4.5 Hold the bulk temperature of the lubricant at 37 6 3Cor 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
35、 in the production of actual prostheses, inorder to produce a specimen with comparable bulk material6The boldface numbers in parentheses refer to the list of references at the end ofthis standard.F 17142properties and surface characteristics (see Practice F 86).5.2 Polymers and Composites:5.2.1 Obta
36、in 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,including steri
37、lization.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 plastics,
38、 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 when known
39、. 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 test.5.2
40、.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 removeany extr
41、aneous 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 reimbedded orotherwise attached to
42、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 necessaryto det
43、ect the slight loss in weight of polymers, such as UHMWpolyethylene, which may wear 30 mg or less per million cycles(3,5). Always weight specimens in the clean, dry condition (seeAnnex A1). Keep the components in a dust-free container andhandle with clean tools to prevent contamination that mightaff
44、ect 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 during t
45、hewear 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 numbero
46、f 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 thenweigh
47、 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 (see AnnexA4). Repeat the specimens until a steady rate of fluid-sorptionhas
48、 been established. The number of weighings will depend onthe amount of fluid sorption exhibited by the specimens.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
49、(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 character-ization of metal, ceramic, or other materials, recording offabrication variables, such as composition, forming method(forging, casting, and so forth) and any postforming process-ing, such as annealing. Obtain data on material propertiesrelevant to wear (for example, grain structure, hardness, andpercentage of conta
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