ASTM F1714-96(2018)
(Guide)Standard Guide for Gravimetric Wear Assessment of Prosthetic Hip Designs in Simulator Devices
Standard Guide for Gravimetric Wear Assessment of Prosthetic Hip Designs in Simulator Devices
SIGNIFICANCE AND USE
3.1 This guide uses a weight-loss method of wear determination for the polymeric components used with hip joint prostheses, using serum or demonstrated equivalent fluid for lubrication, and running under a dynamic load profile representative of the human hip-joint forces during walking (1,2).5 The basis for this weight-loss method for wear measurement was originally developed (3) for pin-on-disk wear studies (see Practice F732) and has been extended to total hip replacements (4,5) femoral-tibial knee prostheses (6), and to femoropatellar knee prostheses (6,7).
3.2 While wear results in a change in the physical dimensions of the specimen, it is distinct from dimensional changes due to creep or plastic deformation, in that wear generally results in the removal of material in the form of polymeric debris particles, causing a loss in weight of the specimen.
3.3 This guide for measuring wear of the polymeric component is suitable for various simulator devices. These techniques can be used with metal, ceramic, carbon, polymeric, and composite counter faces bearing against a polymeric material (for example, polyethylene, polyacetal, and so forth). This weight-loss method, therefore, has universal application for wear studies of total hip replacements that feature polymeric bearings. This weight-loss method has not been validated for high-density material bearing systems, such as metal-metal, carbon-carbon, or ceramic-ceramic. Progressive wear of such rigid bearing combinations generally has been monitored using a linear, variable-displacement transducers or by other profilometric techniques.
SCOPE
1.1 This guide describes a laboratory method using a weight-loss technique for evaluating the wear properties of materials or devices, or both, which are being considered for use as bearing surfaces of human-hip-joint replacement prostheses. The hip prostheses are evaluated in a device intended to simulate the tribological conditions encountered in the human hip joint, for example, use of a fluid such as bovine serum, or equivalent pseudosynovial fluid shown to simulate similar wear mechanisms and debris generation as found in vivo, and test frequencies of 1 Hz or less.
1.2 Since the hip simulator method permits the use of actual implant designs, materials, and physiological load/motion combinations, it can represent a more physiological simulation than basic wear-screening tests, such as pin-on-disk (see Practice F732) or ring-on-disk (see ISO 6474).
1.3 It is the intent of this guide to rank the combination of implant designs and materials with regard to material wear-rates, under simulated physiological conditions. It must be recognized, however, that there are many possible variations in the in vivo conditions, a single laboratory simulation with a fixed set of parameters may not be universally representative.
1.4 The reference materials for the comparative evaluation of candidate materials, new devices, or components, or a combination thereof, shall be the wear rate of extruded or compression-molded, ultra-high molecular weight (UHMW) polyethylene (see Specification F648) bearing against standard counter faces [stainless steel (see Specification F138); cobalt-chromium-molybdenum alloy (see Specification F75); thermomechanically processed cobalt chrome (see Specification F799); alumina ceramic (see Specification F603)], having typical prosthetic quality, surface finish, and geometry similar to those with established clinical history. These reference materials will be tested under the same wear conditions as the candidate materials.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Rec...
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F1714 − 96 (Reapproved 2018)
Standard Guide for
Gravimetric Wear Assessment of Prosthetic Hip Designs in
Simulator Devices
This standard is issued under the fixed designation F1714; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 This guide describes a laboratory method using a
standard.
weight-loss technique for evaluating the wear properties of
1.6 This international standard was developed in accor-
materials or devices, or both, which are being considered for
dance with internationally recognized principles on standard-
use as bearing surfaces of human-hip-joint replacement pros-
ization established in the Decision on Principles for the
theses.Thehipprosthesesareevaluatedinadeviceintendedto
Development of International Standards, Guides and Recom-
simulate the tribological conditions encountered in the human
mendations issued by the World Trade Organization Technical
hip joint, for example, use of a fluid such as bovine serum, or
Barriers to Trade (TBT) Committee.
equivalent pseudosynovial fluid shown to simulate similar
wear mechanisms and debris generation as found in vivo, and
2. Referenced Documents
test frequencies of 1 Hz or less.
1.2 Sincethehipsimulatormethodpermitstheuseofactual 2.1 ASTM Standards:
D883Terminology Relating to Plastics
implant designs, materials, and physiological load/motion
combinations, it can represent a more physiological simulation F75Specification for Cobalt-28 Chromium-6 Molybdenum
Alloy Castings and Casting Alloy for Surgical Implants
than basic wear-screening tests, such as pin-on-disk (see
(UNS R30075)
Practice F732) or ring-on-disk (see ISO 6474).
F86Practice for Surface Preparation and Marking of Metal-
1.3 It is the intent of this guide to rank the combination of
lic Surgical Implants
implant designs and materials with regard to material wear-
F136 Specification for Wrought Titanium-6Aluminum-
rates, under simulated physiological conditions. It must be
4VanadiumELI(ExtraLowInterstitial)AlloyforSurgical
recognized,however,thattherearemanypossiblevariationsin
Implant Applications (UNS R56401)
the in vivo conditions, a single laboratory simulation with a
F138 Specification for Wrought 18Chromium-14Nickel-
fixed set of parameters may not be universally representative.
2.5MolybdenumStainlessSteelBarandWireforSurgical
1.4 The reference materials for the comparative evaluation
Implants (UNS S31673)
of candidate materials, new devices, or components, or a
F370Specification for Proximal Femoral Endoprosthesis
combination thereof, shall be the wear rate of extruded or
(Withdrawn 2005)
compression-molded, ultra-high molecular weight (UHMW)
F565PracticeforCareandHandlingofOrthopedicImplants
polyethylene (see Specification F648) bearing against standard
and Instruments
counter faces [stainless steel (see Specification F138); cobalt-
F603Specification for High-Purity DenseAluminum Oxide
chromium-molybdenum alloy (see Specification F75); thermo-
for Medical Application
mechanically processed cobalt chrome (see Specification
F648Specification for Ultra-High-Molecular-Weight Poly-
F799); alumina ceramic (see Specification F603)], having
ethylene Powder and Fabricated Form for Surgical Im-
typical prosthetic quality, surface finish, and geometry similar
plants
to those with established clinical history. These reference
F732Test Method for Wear Testing of Polymeric Materials
materials will be tested under the same wear conditions as the
Used in Total Joint Prostheses
candidate materials.
1 2
This guide is under the jurisdiction ofASTM Committee F04 on Medical and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Surgical Materials and Devicesand is the direct responsibility of Subcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
F04.22 on Arthroplasty. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2018. Published May 2018. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2013 as F1714–96 (2013). The last approved version of this historical standard is referenced on
DOI: 10.1520/F1714-96R18. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1714 − 96 (2018)
F799Specification for Cobalt-28Chromium-6Molybdenum entirely of noncorrosive materials, such as acrylic plastic or
Alloy Forgings for Surgical Implants (UNS R31537, stainless steel, and is easily removable from the machine for
R31538, R31539) thorough cleaning between tests. Design the wear chambers
G40Terminology Relating to Wear and Erosion suchthatthetestbearingsurfacesareimmersedinthelubricant
throughout the test (3,7).
2.2 ISO Standard:
4.3.2 Component Clamping Fixtures—Since wear is to be
ISO6474ImplantsforSurgery–CeramicMaterialsBasedon
Alumina determined from the weight-loss of the components, the
method for mounting the components in the test chamber
3. Significance and Use
should not compromise the accuracy of assessment of the
weight-loss due to wear.
3.1 This guide uses a weight-loss method of wear determi-
4.3.3 Load—Ensure that the test load profile is representa-
nation for the polymeric components used with hip joint
tive of that which occurs during the patient’s walking cycle,
prostheses, using serum or demonstrated equivalent fluid for
with peak hip-loads ≥2kN (2). The loading apparatus shall be
lubrication, and running under a dynamic load profile repre-
free to follow the specimen as wear occurs, so that the applied
sentative of the human hip-joint forces during walking (1,2).
load is constant to within 63% for the duration of the test.
The basis for this weight-loss method for wear measurement
Never allow the applied load to be below that required to keep
was originally developed (3) for pin-on-disk wear studies (see
the chambers seated (for example, 50 N) (4).
PracticeF732)andhasbeenextendedtototalhipreplacements
4.3.4 Motion—Ensure that relative motion between the hip
(4,5) femoral-tibial knee prostheses (6), and to femoropatellar
components oscillates and simulates the flexion-extension arc
knee prostheses (6,7).
of walking. Addition of internal-external or abduction-
3.2 While wear results in a change in the physical dimen-
adduction arcs is at the investigator’s discretion. It is recom-
sions of the specimen, it is distinct from dimensional changes
mendedthattheorientationsofthecupandballrelativetoeach
due to creep or plastic deformation, in that wear generally
other and to the load-axis be maintained by suitable specimen-
results in the removal of material in the form of polymeric
holder keying.
debris particles, causing a loss in weight of the specimen.
4.3.5 Oscillating Frequency—Oscillatethehipprosthesesat
3.3 This guide for measuring wear of the polymeric com-
a rate of one cycle per second (1 Hz).
ponent is suitable for various simulator devices. These tech-
4.3.6 Cycle Counter—Include a counter with the hip-
niquescanbeusedwithmetal,ceramic,carbon,polymeric,and
simulator to record the total number of wear cycles.
composite counter faces bearing against a polymeric material
4.3.7 Friction—It is recommended that the machine include
(for example, polyethylene, polyacetal, and so forth). This
sensors capable of monitoring the friction forces transmitted
weight-loss method, therefore, has universal application for
across the bearing surfaces during the wear test.
wear studies of total hip replacements that feature polymeric
4.4 Lubricant:
bearings. This weight-loss method has not been validated for
4.4.1 It is recommended that the specimen be lubricated
high-density material bearing systems, such as metal-metal,
withbovinebloodserum;however,anothersuitablelubrication
carbon-carbon, or ceramic-ceramic. Progressive wear of such
medium may be used if validated.
rigidbearingcombinationsgenerallyhasbeenmonitoredusing
4.4.2 If serum is used, use filtered-sterilized serum rather
a linear, variable-displacement transducers or by other profi-
than pooled serum since the former is less likely to contain
lometric techniques.
hemolyzed blood material, which has been shown to adversely
4. Apparatus and Materials affect the lubricating properties of the serum (3). Diluted
solutions of serum have also been used for this purpose (8).
4.1 Hip Prosthesis Components—The hip-joint prosthesis
Filtration may remove hard, abrasive, particulate contaminants
comprises a ball-and-socket configuration in which materials
that might otherwise affect the wear properties of the speci-
such as polymers, composites, metal alloys, ceramics, and
mens being tested.
carbon have been used in various combinations and designs.
4.4.3 Maintain the volume and concentration of the lubri-
4.2 Component Configurations—The diameter of the pros-
cant nearly constant throughout the test. This may be accom-
thetic ball may vary from 22 to 54 mm or larger. The design
plished by sealing the chambers so that water does not
may include ball-socket, trunnion, bipolar, or other configura-
evaporate,orperiodicallyorcontinuouslyreplacingevaporated
tions.
water with distilled water.
4.3 Hip Simulator: 4.4.4 To retard bacterial degradation, freeze and store the
4.3.1 Test Chambers—In the case of a multi-specimen serumuntilneededforthetest.Inaddition,ensurethatthefluid
machine, contain the components in individual, isolated cham- medium in the test contains 0.2% sodium azide (or other
bers to prevent contamination of one set of components with suitable antibiotic) to minimize bacterial degradation. Other
debris from another test. Ensure that the chamber is made lubricantsshouldbeevaluatedtodetermineappropriatestorage
conditions.
4.4.5 It is recommended that ethylene-diaminetetraacetic
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
acid (EDTA) be added to the serum at a concentration of 20
4th Floor, New York, NY 10036, http://www.ansi.org.
mM to bind calcium in solution and minimize precipitation of
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. calcium phosphate onto the bearing surfaces. The latter event
F1714 − 96 (2018)
has been shown to strongly affect the friction and wear (3,5).Alwaysweighspecimensintheclean,drycondition(see
properties, particularly of polyethylene/ceramic combinations. AnnexA1). Keep the components in a dust-free container and
The addition of EDTA to other lubricant mediums should be handle with clean tools to prevent contamination that might
evaluated. affect the weight measurement. Weigh each wear and control
4.4.6 Alubricant other than bovine serum may be used if it component three times in rotation to detect random errors in
can be shown that its lubricating properties and, therefore, the weighing process.
material wear properties are reasonably physiological (8).In
5.3 Soaking of Polymeric and Composite Prostheses:
such a case, specify the lubricant in the test report.
5.3.1 Polymeric and composite components should be pre-
4.5 Hold the bulk temperature of the lubricant at 37 6 3°C soaked in the lubricant to minimize fluid sorption during the
or as specified, if different. wear run. Without presoaking, components of very low-wear
polymers such as polyethylene may show a net increase in
5. Specimen Preparation
weight during the initial wear intervals, due to fluid sorption
(3,4). The error due to fluid sorption can be reduced through
5.1 The governing rule for preparation of component coun-
presoakingandtheuseofcontrolsoakspecimens.Thenumber
ter faces is that the fabrication process parallels that used or
ofspecimensrequiredandthelengthofpresoakingdependson
intendedforuseintheproductionofactualprostheses,inorder
thevariabilityandmagnitudeoffluidsorptionencountered (4).
to produce a specimen with comparable bulk material proper-
5.3.2 After fabrication and characterization, clean and dry
ties and surface characteristics (see Practice F86).
the wear components and three soak-control components of
5.2 Polymers and Composites:
each test material in accordance with Annex A4, and then
5.2.1 Obtain a fabrication history for each polymeric or
weigh by precisely controlled and repeatable methods. Place
composite component, including information such as grade,
thewearcomponentsandsoakcontrolsinacontainerofserum
batch number, and processing variables, including method of
for a specified time interval. Then, remove, clean, dry, and
forming (extruding, molding, and so forth), temperature,
reweigh the components, and calculate the weight-loss (see
pressure, and forming time used, and any post-forming
Annex A4). Repeat the specimens until a steady rate of
treatments, including sterilization.
fluid-sorption has been established. The number of weighings
5.2.2 Pretest characterization may include measurement of
will depend on the amount of fluid sorption exhibited by the
bulk material properties, such as molecular-weight range and
specimens.
distribution, percent crystallinity, density, or other.The surface
5.3.3 Ingeneral,theweightofthecomponentswillstabilize
finish of specimens may be characterized by profilometry,
at an asymptotic value in a reasonable time period. With
photomicrography, replication by various plastics, or other
UHMW polyethylene, a presoak period of 30 days has been
techniques.
found adequate (4,7). In any case, use the weight-gain of the
5.2.3 Sterilization—Sterilize the components in a manner
soak controls to correct for ongoing fluid sorption by the wear
typical of that in clinical use for such devices, including total
components during the wear test.
dose and dose rate, as these may affect the wear properties of
5.4 Counterfaces of Metal Alloys, Ceramic, or Other Mate-
the materials. Report these processing parameters with the
rials:
aging time prior to each test when known. Sterilization of all
5.4.1 Characterization—Include with the pretest character-
testandcontrolcomponentswithinaspecifictestgroupshould
ization of metal, ceramic, or other materials, recording of
be done simultaneously (in a single container), when possible,
fabrication variables, such as composition, forming method
to minimize variation among the specimens. This wear-
(fo
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