ASTM F2345-03(2008)
(Test Method)Standard Test Methods for Determination of Static and Cyclic Fatigue Strength of Ceramic Modular Femoral Heads
Standard Test Methods for Determination of Static and Cyclic Fatigue Strength of Ceramic Modular Femoral Heads
SIGNIFICANCE AND USE
These test methods can be used to determine the effects of head and cone materials, design variables, manufacturing, and other conditions on the static and cyclic load-carrying ability of modular femoral heads mounted on the cones of femoral stem prostheses.
These test methods may use actual femoral prostheses or neck-cone models of simplified geometry with the same geometrical and material characteristics as in the implants. In either case, the matching metallic cone region of the test specimen selected shall be of the same material, tolerances, and finishing as the final femoral stem prosthesis.
The static test data may yield valuable information about the relative strengths and merits of different head and cone designs for particular applications. Due to the high forces anticipated for this type of destructive test (>40 kN), the boundary conditions and load levels far exceed possible in vivo loading parameters and therefore may not necessarily be applicable as a quantitative indicator of expected in vivo device performance.
In the fatigue test methods, it is recognized that actual loading in vivo is quite varied, and that no one set of experimental conditions can encompass all possible variations. Thus, the test methods included here represent a simplified model for the purposes of comparisons between designs and materials. These test methods are intended to be performed in air.
The test data may yield valuable information about the relative strengths of different head and cone designs.
SCOPE
1.1 These test methods cover the evaluation of the static and cyclic fatigue strength of ceramic modular femoral heads, mounted on a cone as used on the femoral stem of the total hip arthroplasty.
1.2 These test methods were primarily developed for evaluation of ceramic (Specifications F 603 and F 1873) head designs on metal cones but may have application to other materials.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F2345 − 03(Reapproved 2008)
Standard Test Methods for
Determination of Static and Cyclic Fatigue Strength of
Ceramic Modular Femoral Heads
This standard is issued under the fixed designation F2345; 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 2.2 Other Documents:
DIN 4768Determination of Surface Roughness R,R , and
a z
1.1 Thesetestmethodscovertheevaluationofthestaticand
R with Electric Stylus Instruments; Basic Data
max
cyclic fatigue strength of ceramic modular femoral heads,
FDA Guidance Documentfor the Preparation of Premarket
mountedonaconeasusedonthefemoralstemofthetotalhip
NotificationsforCeramicBallHipSystems(draftJan.10,
arthroplasty. 5
1995)
1.2 These test methods were primarily developed for evalu-
3. Terminology
ationofceramic(SpecificationsF603andF1873)headdesigns
3.1 Definitions:
on metal cones but may have application to other materials.
3.1.1 circularity—deviations of taper cross section from a
1.3 The values stated in SI units are to be regarded as
perfect circle.
standard. No other units of measurement are included in this
3.1.2 cone—the proximal end of the femoral component
standard.
fabricated as a truncated right cone and used to engage with a
1.4 This standard does not purport to address all of the
mating conical bore of the modular femoral head.
safety concerns, if any, associated with its use. It is the
3.1.3 cone angle—included angle of cone (Fig. 1).
responsibility of the user of this standard to establish appro-
3.1.4 femoral neck-axis—centerline or axis of symmetry of
priate safety and health practices and determine the applica-
the femoral cone.
bility of regulatory limitations prior to use.
3.1.5 head size—nominal spherical diameter of the head
(generally standardized, but not limited to 22, 26, 28, 32, and
2. Referenced Documents
36 mm for total hips.)
2.1 ASTM Standards:
3.1.6 installation load—the force, applied at 0° from femo-
E4Practices for Force Verification of Testing Machines
ral neck axis, used to settle the head on the cone prior to
F603Specification for High-Purity DenseAluminum Oxide
testing.
for Medical Application
3.1.7 load axis—line of action of the compressive force
F1873SpecificationforHigh-PurityDenseYttriaTetragonal
applied to the head.
Zirconium Oxide Polycrystal (Y-TZP) for Surgical Im-
plant Applications (Withdrawn 2007) 3.1.8 load axis angle—the measured angle “L” between the
F1875Practice for Fretting Corrosion Testing of Modular
line of action of the applied force and femoral neck axis (see
Implant Interfaces: Hip Femoral Head-Bore and Cone Fig. 5).
Taper Interface
3.1.9 load magnitude—the peak (absolute value) compres-
sive force of the applied constant amplitude cyclic force.
3.1.10 load rate—rate of applied compressive force.
ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedical
3.1.11 stroke rate—therateofthestrokedisplacementofthe
andSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommittee
force applicator.
F04.22 on Arthroplasty.
Current edition approved Dec. 15, 2008. Published December 2008. Originally
3.1.12 surface finish—measured roughness of surface of
approved in 2003. Last previous edition approved in 2003 as F2345–03. DOI:
taper cone or head bore as determined by DIN 4768.
10.1520/F2345-03R08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on Available from Beuth Verlag GmbH (DIN—DIN Deutsches Institut fur
the ASTM website. Normung e.V.), Burggrafenstrasse 6, 10787, Berlin, Germany.
3 5
The last approved version of this historical standard is referenced on Available from Food and Drug Administration (FDA), 5600 Fishers Ln.,
www.astm.org. Rockville, MD 20857.
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F2345 − 03 (2008)
FIG. 1 Geometrical Design Criteria for Modular Ball
FIG. 3 Loading in a Metal Cone
FIG. 2 Geometrical Design Criteria for Mating Conical Fit
3.1.13 test frequency—therateofcyclicrepetitionoffatigue
loading in cycles per second.
3.1.14 THR—total hip replacement.
4. Significance and Use
4.1 These test methods can be used to determine the effects
of head and cone materials, design variables, manufacturing,
and other conditions on the static and cyclic load-carrying
ability of modular femoral heads mounted on the cones of
femoral stem prostheses.
4.2 Thesetestmethodsmayuseactualfemoralprosthesesor
neck-cone models of simplified geometry with the same
geometrical and material characteristics as in the implants. In
either case, the matching metallic cone region of the test
specimenselectedshallbeofthesamematerial,tolerances,and
FIG. 4 Loading Through a Copper Ring
finishing as the final femoral stem prosthesis.
4.3 The static test data may yield valuable information boundaryconditionsandloadlevelsfarexceedpossible in vivo
about the relative strengths and merits of different head and loading parameters and therefore may not necessarily be
conedesignsforparticularapplications.Duetothehighforces applicableasaquantitativeindicatorofexpected in vivodevice
anticipated for this type of destructive test (>40 kN), the performance.
F2345 − 03 (2008)
7. Procedure
7.1 Sample Assembly:
7.1.1 Following normal laboratory cleaning procedures to
remove any debris or other surface contaminants, the head and
cone are assembled on a suitable test machine. A suggested
procedure for cleaning and drying of the specimens is given in
Appendix X1. Any cleaning procedures used should be con-
sistent with typical manufacturing practices.
7.1.2 The stem taper cones are mounted at 0° load angle (L
= 0°).An assembly force of 2 kN is used to mount the femoral
ball and achieve a standard head/cone reference position prior
to all tests.
7.1.3 Pre-assembly of the head on the taper should be
conducted under stroke or load control at a rate that will
consistentlyproducetherequired2kNassemblyloadwithless
than 50 N of overshoot. One of the following loading condi-
tions for assembly is suggested:
7.1.3.1 A loading rate of 500 N/s 6 100.
7.1.3.2 A stroke rate of 0.04 mm/s.
FIG. 5 Pictorial Example of the Load Angle “L”
7.2 General Test Requirements:
7.2.1 The tests are performed at room temperature in air.
7.2.2 New test cones and femoral heads shall be used for
4.4 In the fatigue test methods, it is recognized that actual
each test. Note that it is imperative that components that
loading in vivo is quite varied, and that no one set of
survive the test should not be used for clinical purposes after
experimental conditions can encompass all possible variations.
testing.
Thus, the test methods included here represent a simplified
7.2.3 The load axis angle “L” shall be maintained within
model for the purposes of comparisons between designs and
61° for all test samples.
materials. These test methods are intended to be performed in
NOTE 1—Precautions should be taken to protect the test operator from
air.
injurybyfragmentsshouldthespecimenshatterwhenunderloadorwhen
4.5 The test data may yield valuable information about the disassembling or when storing the specimen after removal of the force
from unfractured specimens.
relative strengths of different head and cone designs.
7.3 Static On Axis Test Method:
5. Apparatus
7.3.1 The load axis angle “L” is 0°.
7.3.2 Number of Test Specimens—Aminimumoffivespeci-
5.1 The loading fixtures should be capable of sustaining
mens is recommended for a test group.
forces up to the anticipated fracture level. The static loading
7.3.3 The femoral head may be loaded through a hardened
fixtures may require load capacity up to 200 kN in some
(minimum 150 HB) metal 100 6 1° cone with a minimum
circumstances. The fatigue tests should use fixtures with
surface diameter of 0.75 times the head diameter (Fig. 3)or
fatigue load capacity up to 50 kN.
alternatively,thecontactsurfacemaybeprotectedbymeansof
5.2 Thefixturesshallbeconstructedsothatthelineofforce
a copper ring (Fig. 4).Asuggested minimum thickness for the
application passes through the center of the femoral head.
copperringis1.25mmanditshouldextendabout2.25mmon
5.3 Due to the high forces anticipated in this type of cyclic,
either side of the contact diameter.The diameter of contact for
destructive test, appropriate shielding of the modular ball test
theappliedforceshouldbeapproximately0.643timesthehead
site is recommended.
size.
7.3.4 The conical metal loading fixture may be damaged if
6. Equipment Characteristics
the test fractures the sample. It shall be examined after each
test fracture and be discarded if damaged. If a copper ring is
6.1 Generally, the static tests should be performed on either
used for the contact, a new ring shall be used for each test.
mechanical(powerscrews)orhydraulic(servo-hydraulic)load
7.3.5 Use of one of the following loading conditions are
frameswithadequateloadcapacity(upto200kN).Thefatigue
recommended:
tests should generally be performed on hydraulic (servo-
7.3.5.1 Position control with a stroke rate of 0.04 mm/s
hydraulic) load frames with adequate load capacity (up to 50
(0.0015 in./s) or,
kN).Thetestequipmentshouldmeettherequirementsoutlined
7.3.5.2 Load control with a loading rate of 1 kN/s (224.8
in Practices E4.
lb/s) or less.
6.2 The varying force, as determined by suitable dynamic
7.4 On Axis Fatigue Test Method:
verification, should be maintained at all times to within 62%
7.4.1 The maximum test frequency shall not exceed 30 Hz.
of the largest compressive force being used for the duration of
the test. 7.4.2 The load axis angle “L” is 0°.
F2345 − 03 (2008)
7.4.3 The femoral head may be loaded through a hardened statementjustifyingthenumberandkindsofsamplesshouldbe
metal 100 6 1° cone (Fig. 3) or alternatively, the contact ring included (FDA Guidance Document).
may be protected by means of a copper ring (Fig. 4). A
8.4 Additional optional information characterizing the bore
suggested minimum thickness for the copper ring is 1.25 mm
and cone dimensions and tolerances (Figs. 1 and 2) would be
and it should extend about 2.25 mm on either side of the
desirable to better interpret the test results. This information
contact diameter.The diameter of contact for the applied force
may include, but is not limited to the following: cone type,
should be the head diameter multiplied by the cosine of 50° or
head bore angle, head bore major/minor diameters, bore
0.643 times the head diameter.
surface roughness (R,R per DIN 4768), cone angle, cone
a z
7.4.4 The conical metal loading fixture may be damaged if
diameter,conesurfaceroughness(R,R perDIN4768),length
a z
the test fractures the sample. It should be examined after each
of mating interface between the bore and cone, and method of
test fracture and be discarded if damaged. If a copper ring is
femoral ball sterilization.
usedforthecontactsurface,anewringshouldbeusedforeach
test.
9. Precision and Bias
7.4.5 The fatigue force shall have a sinusoidal waveform
appliedfromtheforcemagnitudetoaminimumthatis10%of 9.1 Precision—For a destructive test, wherein replicate
the load magnitude. measurements cannot be made on a single test sample, dis-
7.4.6 The cyclic forces should be applied until 10 million agreement between replicate measurements on different
cycles without failure of the components or until fracture has samples includes actual part-to-part variability in the property
occurred. being measured as well as methodological imprecision. It is
impossible to design an experiment that can separate these
7.5 Off Axis Fatigue Test Method:
factors. Thus, any statements regarding precision include both
7.5.1 The maximum test frequency shall not exceed 30 Hz.
factors.
7.5.2 The load axis angle “L” is 30°.
9.1.1 Theprecisionandbiasofthesetestmethodsneedtobe
7.5.3 A polymeric spherical concave component with the
established. Test results that can be used to establish precision
same segment diameter as suggested in 7.4.3 should be used
and bias are solicited.
(Fig. 5). The segment diameter should not change during the
9.1.2 Thefollowingdataareofferedforguidance.Atotalof
test.
32 nominally identical alumina heads (28-mm diameter,
7.5.4 The fatigue force shall have a sinusoidal waveform
⁄14-mm modular taper), representing four different manufac-
appliedfromtheforcemagnitudetoaminimumthatis10%of
turinglots,weretestedforstaticultimatecompressivestrength
the load magnitude.
(UCS)whenattachedtoTi6Al4Vtapers,byasinglelaboratory.
8. Report
The data are summarized as follows:
8.1 The minimum required report shall identify the Lot
Sample Maximum Minimum Mean Std.
Desig-
manufacturer(s), head size, femoral head material, the defini-
Size UCS UCS UCS Deviation
nation
tion of failure used in the test, the cone material, and the
kN kN kN kN (% of mean)
description of the cone and taper geometries.
1 10 57 49 53.4 2.5 (4.7 %)
8.2 The report shall also describe the test equipment and all
2 8 62 54 57.2 2.4 (4.2 %)
3 10 64 46 56.2 5.7 (10.1 %)
test parameters.
4 4 58 54 56.5 1.7 (3.0 %)
8.2.1 For the static test, the control mode, the loading rate,
9.1.3 For these four sets of data, one can estimate the
and a description of the loading contact.
8.2.2 Forthefatiguetests,thetestfrequency,thepeakforce, weighted repeatability standard deviation as 6.0% of mean
UCS. Phrased differently, the experience from this one labo-
the load axis angle “L,” load amplitude, and a description of
the loading contact for each sample. ratory would indicate that any two measurements at the same
laboratory would be expected to differ by more than 23.7% of
8.3 Test Results:
their mean value no more than one time in 20.
8.3.1 For the static test, the maximum failure force for each
sample is required. Reporting of the mean failure force,
10. Keywords
standard deviation, and range is also recommended.
8.3.2 For the fatigue test methods, the number of cycles 10.1 bore; ceramic; cone; fatigue; modular head; static;
completed by the sample and whether the sample failed. A strength
F2345 − 03 (2008)
APPENDIXES
(Nonmandatory Information)
X1. RATIONALE
X1.1 Modular or interchangeable femoral heads have been X1.3.5 A series of 10 ruptures of zirconia heads were
used in various THR designs since approximately 1970. This reported by J. P. Arnaud et al (6)
...
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