ASTM F2345-03
(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
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 the 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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Designation:F2345–03
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope NotificationsforCeramicBallHipSystems(draftJan.10,
1995)
1.1 Thesetestmethodscovertheevaluationofthestaticand
cyclic fatigue strength of ceramic modular femoral heads,
3. Terminology
mountedonaconeasusedonthefemoralstemofthetotalhip
3.1 Definitions:
arthroplasty.
3.1.1 circularity—deviations of taper cross section from a
1.2 These test methods were primarily developed for evalu-
perfect circle.
ation of ceramic (Specifications F603 and F1873) head
3.1.2 cone—the proximal end of the femoral component
designs on metal cones but may have application to other
fabricated as a truncated right cone and used to engage with a
materials.
mating conical bore of the modular femoral head.
1.3 The values stated in SI units are to be regarded as the
3.1.3 cone angle—included angle of cone (Fig. 1).
standard.
3.1.4 femoral neck-axis—centerline or axis of symmetry of
1.4 This standard does not purport to address all of the
the femoral cone.
safety concerns, if any, associated with its use. It is the
3.1.5 head size—nominal spherical diameter of the head
responsibility of the user of this standard to establish appro-
(generally standardized, but not limited to 22, 26, 28, 32, and
priate safety and health practices and determine the applica-
36 mm for total hips.)
bility of regulatory limitations prior to use.
3.1.6 installation load—the force, applied at 0° from femo-
2. Referenced Documents ral neck axis, used to settle the head on the cone prior to
testing.
2.1 ASTM Standards:
3.1.7 load axis—line of action of the compressive force
E4 Practices for Force Verification of Testing Machines
applied to the head.
F603 Specification for High-Purity Dense Aluminum Ox-
3.1.8 load axis angle—the measured angle “L” between the
ide for Surgical Implant Application
line of action of the applied force and femoral neck axis (see
F1873 Specification for High-Purity Dense Yttria Tetrago-
Fig. 5).
nal Zirconium Oxide Polycrystal (Y-TZP) for Surgical
3.1.9 load magnitude—the peak (absolute value) compres-
Implant Applications
sive force of the applied constant amplitude cyclic force.
F1875 Practice for Fretting Corrosion Testing of Modular
3.1.10 load rate—rate of applied compressive force.
Implant Interfaces: Hip Femoral Head-Bore and Cone
3.1.11 stroke rate—the rate of the stroke displacement of
Taper Interface
the force applicator.
2.2 Other Documents:
3.1.12 surface finish—measured roughness of surface of
DIN 4768 Determination of Surface Roughness R,R , and
a z
taper cone or head bore as determined by DIN 4768.
R with Electric Stylus Instruments; Basic Data
max
3.1.13 test frequency—therateofcyclicrepetitionoffatigue
FDAGuidance Document for the Preparation of Premarket
loading in cycles per second.
3.1.14 THR—total hip replacement.
ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedical
andSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommittee
4. Significance and Use
F04.22 on Arthroplasty.
4.1 These test methods can be used to determine the effects
Current edition approved Nov. 1, 2003. Published January 2004.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or of head and cone materials, design variables, manufacturing,
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 4
Available from Beuth Verlag GmbH (DIN—DIN Deutsches Institut fur Available from Food and Drug Administration (FDA), 5600 Fishers Ln.,
Normung e.V.), Burggrafenstrasse 6, 10787, Berlin, Germany. Rockville, MD 20857.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2345–03
FIG. 1 Geometrical Design Criteria for Modular Ball
FIG. 3 Loading in a Metal Cone
FIG. 2 Geometrical Design Criteria for Mating Conical Fit
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
finishing as the final femoral stem prosthesis.
4.3 The static test data may yield valuable information
about the relative strengths and merits of different head and
conedesignsforparticularapplications.Duetothehighforces
anticipated for this type of destructive test (>40 kN), the
boundaryconditionsandloadlevelsfarexceedpossible in vivo
loading parameters and therefore may not necessarily be
applicableasaquantitativeindicatorofexpected in vivodevice
FIG. 4 Loading Through a Copper Ring
performance.
4.4 In the fatigue test methods, it is recognized that actual
loading in vivo is quite varied, and that no one set of model for the purposes of comparisons between designs and
experimental conditions can encompass all possible variations. materials. These test methods are intended to be performed in
Thus, the test methods included here represent a simplified air.
F2345–03
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.
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
each test. Note that it is imperative that components that
survive the test should not be used for clinical purposes after
testing.
7.2.3 The load axis angle “L” shall be maintained within
61° for all test samples.
FIG. 5 Pictorial Example of the Load Angle “L”
NOTE 1—Precautions should be taken to protect the test operator from
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°.
5.1 The loading fixtures should be capable of sustaining
7.3.2 Number of Test Specimens—Aminimumoffivespeci-
forces up to the anticipated fracture level. The static loading
mens is recommended for a test group.
fixtures may require load capacity up to 200 kN in some
7.3.3 The femoral head may be loaded through a hardened
circumstances. The fatigue tests should use fixtures with
(minimum 150 HB) metal 100 6 1° cone with a minimum
fatigue load capacity up to 50 kN.
surface diameter of 0.75 times the head diameter (Fig. 3) or
5.2 Thefixturesshallbeconstructedsothatthelineofforce
alternatively,thecontactsurfacemaybeprotectedbymeansof
application passes through the center of the femoral head.
a copper ring (Fig. 4).Asuggested minimum thickness for the
5.3 Due to the high forces anticipated in this type of cyclic,
copperringis1.25mmanditshouldextendabout2.25mmon
destructive test, appropriate shielding of the modular ball test
either side of the contact diameter.The diameter of contact for
site is recommended.
theappliedforceshouldbeapproximately0.643timesthehead
size.
6. Equipment Characteristics
7.3.4 The conical metal loading fixture may be damaged if
the test fractures the sample. It shall be examined after each
6.1 Generally, the static tests should be performed on either
test fracture and be discarded if damaged. If a copper ring is
mechanical(powerscrews)orhydraulic(servo-hydraulic)load
used for the contact, a new ring shall be used for each test.
frameswithadequateloadcapacity(upto200kN).Thefatigue
tests should generally be performed on hydraulic (servo- 7.3.5 Use of one of the following loading conditions are
recommended:
hydraulic) load frames with adequate load capacity (up to 50
kN).Thetestequipmentshouldmeettherequirementsoutlined 7.3.5.1 Position control with a stroke rate of 0.04 mm/s
in Practices E4. (0.0015 in./s) or,
6.2 The varying force, as determined by suitable dynamic
7.3.5.2 Load control with a loading rate of 1 kN/s (224.8
verification, should be maintained at all times to within 62%
lb/s) or less.
of the largest compressive force being used for the duration of
7.4 On Axis Fatigue Test Method:
the test.
7.4.1 The maximum test frequency shall not exceed 30 Hz.
7.4.2 The load axis angle “L” is 0°.
7. Procedure
7.4.3 The femoral head may be loaded through a hardened
7.1 Sample Assembly: metal 100 6 1° cone (Fig. 3) or alternatively, the contact ring
7.1.1 Following normal laboratory cleaning procedures to may be protected by means of a copper ring (Fig. 4). A
remove any debris or other surface contaminants, the head and suggested minimum thickness for the copper ring is 1.25 mm
cone are assembled on a suitable test machine. A suggested and it should extend about 2.25 mm on either side of the
procedure for cleaning and drying of the specimens is given in contact diameter.The diameter of contact for the applied force
Appendix X1. Any cleaning procedures used should be con- should be the head diameter multiplied by the cosine of 50° or
sistent with typical manufacturing practices. 0.643 times the head diameter.
F2345–03
7.4.4 The conical metal loading fixture may be damaged if desirable to better interpret the test results. This information
the test fractures the sample. It should be examined after each may include, but is not limited to the following: cone type,
test fracture and be discarded if damaged. If a copper ring is head bore angle, head bore major/minor diameters, bore
usedforthecontactsurface,anewringshouldbeusedforeach surface roughness (R,R per DIN 4768), cone angle, cone
a z
test. diameter, cone surface roughness (R,R per DIN 4768),
a z
7.4.5 The fatigue force shall have a sinusoidal waveform length of mating interface between the bore and cone, and
appliedfromtheforcemagnitudetoaminimumthatis10%of method of femoral ball sterilization.
the load magnitude.
7.4.6 The cyclic forces should be applied until 10 million 9. Precision and Bias
cycles without failure of the components or until fracture has
9.1 Precision—For a destructive test, wherein replicate
occurred.
measurements cannot be made on a single test sample, dis-
7.5 Off Axis Fatigue Test Method:
agreement between replicate measurements on different
7.5.1 The maximum test frequency shall not exceed 30 Hz.
samples includes actual part-to-part variability in the property
7.5.2 The load axis angle “L” is 30°.
being measured as well as methodological imprecision. It is
7.5.3 A polymeric spherical concave component with the
impossible to design an experiment that can separate these
same segment diameter as suggested in 7.4.3 should be used
factors. Thus, any statements regarding precision include both
(Fig. 5). The segment diameter should not change during the
factors.
test.
9.1.1 Theprecisionandbiasofthesetestmethodsneedtobe
7.5.4 The fatigue force shall have a sinusoidal waveform
established. Test results that can be used to establish precision
appliedfromtheforcemagnitudetoaminimumthatis10%of
and bias are solicited.
the load magnitude.
9.1.2 Thefollowingdataareofferedforguidance.Atotalof
32 nominally identical alumina heads (28-mm diameter,
8. Report
⁄14-mm modular taper), representing four different manufac-
8.1 The minimum required report shall identify the manu-
turinglots,weretestedforstaticultimatecompressivestrength
facturer(s), head size, femoral head material, the definition of
(UCS)whenattachedtoTi6Al4Vtapers,byasinglelaboratory.
failureusedinthetest,theconematerial,andthedescriptionof
The data are summarized as follows:
the cone and taper geometries.
Lot
Sample Maximum Minimum Mean Std.
8.2 The report shall also describe the test equipment and all Desig-
Size UCS UCS UCS Deviation
nation
test parameters.
kN kN kN kN (% of mean)
8.2.1 For the static test, the control mode, the loading rate,
and a description of the loading contact. 1 10 57 49 53.4 2.5 (4.7 %)
2 8 62 54 57.2 2.4 (4.2 %)
8.2.2 Forthefatiguetests,thetestfrequency,thepeakforce,
3 10 64 46 56.2 5.7 (10.1 %)
the load axis angle “L,” load amplitude, and a description of
4 4 58 54 56.5 1.7 (3.0 %)
the loading contact for each sample.
9.1.3 For these four sets of data, one can estimate the
8.3 Test Results:
weighted repeatability standard deviation as 6.0% of mean
8.3.1 For the static test, the maximum failure force for each
UCS. Phrased differently, the experience from this one labo-
sample is required. Reporting of the mean failure force,
ratory would indicate that any two measurements at the same
standard deviation, and range is also recommended.
laboratory would be expected to differ by more than 23.7% of
8.3.2 For the fatigue test methods, the number of cycles
their mean value no more than one time in 20.
completed by the sample and whether the sample failed. A
statementjustifyingthenumberandkindsofsamplesshouldbe
10. Keywords
included (FDA Guidance Document).
8.4 Additional optional information characterizing the bore 10.1 bore; ceramic; cone; fatigue; modular head; static;
and cone dimensions and tolerances (Figs. 1 and 2) would be strength
F2345–03
APPENDIXES
(Nonmandatory Information)
X1. RATIONALE
X1.1 Modular or interchangeable femoral heads have been head design. This series of ruptures seem to be due to the
used in various THR designs since approximately 1970. This inappropriate fit between the head and taper. The angle of the
concept provides several features to suit the patient as planned head bore was smaller than the angle of the metallic taper.
pre-operatively or selected intra-operatively by the surgeon, or X1.3.6 A detailed survey for one zirconia head source was
both, such a
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