ASTM F1440-92(2002)
(Practice)Standard Practice for Cyclic Fatigue Testing of Metallic Stemmed Hip Arthroplasty Femoral Components Without Torsion
Standard Practice for Cyclic Fatigue Testing of Metallic Stemmed Hip Arthroplasty Femoral Components Without Torsion
SIGNIFICANCE AND USE
This practice can be used to describe the effects of materials, manufacturing, and design variables on the fatigue resistance of metallic stemmed femoral components subjected to cyclic loading for relatively large numbers of cycles. The recommended test assumes a “worst case‘‘ situation where proximal support for the stem has been lost. It is also recognized that for some materials the environment may have an effect on the response to cyclic loading. The test environment used and the rationale for the choice of that environment should be described in the report.
It is recognized that actual in vivo loading conditions are not constant amplitude. However, there is not sufficient information available to crate standard load spectrums for metallic stemmed femoral components. Accordingly, a simple periodic constant amplitude force is recommended.
In order for fatigue data on femoral stems to be useful for comparison, it must be reproducible among different laboratories. Consequently, it is essential that uniform procedures be established.
SCOPE
1.1 This practice describes a method for the fatigue testing of metallic stemmed femoral components used in hip arthroplasty. The described method is intended to be used to evaluate the comparison of various designs and materials used for stemmed femoral components used in the arthroplasty. This practice covers procedures for the performance of fatigue tests using (as a forcing function) a periodic constant amplitude force.
1.2 This practice applies primarily to one-piece prostheses and modular components, with head in place such that prostheses should not have an anterior/posterior bow, and should have a nearly straight section on the distal 50 mm of the stem. This practice may require modifications to accommodate other femoral stem designs.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 For additional information see Refs. (1-5) .
General Information
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Standards Content (Sample)
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Designation:F1440–92(Reapproved 2002)
Standard Practice for
Cyclic Fatigue Testing of Metallic Stemmed Hip Arthroplasty
Femoral Components Without Torsion
This standard is issued under the fixed designation F 1440; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice describes a method for the fatigue testing
of metallic stemmed femoral components used in hip arthro-
plasty.The described method is intended to be used to evaluate
the comparison of various designs and materials used for
stemmed femoral components used in the arthroplasty. This
practice covers procedures for the performance of fatigue tests
using (as a forcing function) a periodic constant amplitude
force.
1.2 This practice applies primarily to one-piece prostheses
and modular components, with head in place such that pros-
theses should not have an anterior/posterior bow, and should
have a nearly straight section on the distal 50 mm of the stem.
This practice may require modifications to accommodate other
femoral stem designs.
1.3 The values stated in SI units are to be regarded as the
standard.
1.4 For additional information see Refs. (1-5) .
2. Referenced Documents
2.1 ASTM Standards:
E 4 Practices for Force Verification of Testing Machines
E 466 Practice for Conducting Force Controlled Constant
Amplitude Axial Fatigue Tests of Metallic Materials
E 467 Practice for Verification of Constant Amplitude Dy-
FIG. 1 Collared Device
namic Forces in an Axial Fatigue Testing System
E 468 Practice for Presentation of Constant Amplitude Fa-
tigue Test Results for Metallic Materials
3.1.4 geometric centroid (cantilever plane)— the point in a
cross-sectional area of the cantilever plane whose coordinates
3. Terminology
are the mean values of the coordinates of all the points in the
3.1 Definitions and Symbols (see Fig. 1(a) and 1(b)):
area.
3.1.1 cantilever plane—a plane perpendicular to the line of
3.1.5 line of load application—the loading axis of the test
load application at the level on the stem where the stem
machine.
becomes unsupported.
3.1.6 Reference Line L1, distal stem axis—the medial-
3.1.2 distal stem axis—the centerline in the anterior/
lateral(M-L)centerlineofthemostdistal50mmofsteminthe
posterior projection of the most distal 50 mm of the stem.
A-P projection.
3.1.3 estimated maximum bending moment—the maximum
3.1.7 Reference Line L2:
load times the unloaded moment arm.
3.1.7.1 collared device— the plane of the distal side of the
collar in the A-P projection.
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
3.1.7.2 collarless device—theresectionplanerecommended
Surgical Materials and Devices and is the direct responsibility of Subcommittee
for the device in the A-P projection.
F04.22 on Arthroplasty.
Current edition approved Sept. 15, 1992. Published November 1992.
Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1440–92 (2002)
3.1.8 Reference Point P1—the spherical center of the pros-
thesis head.
3.1.9 Reference Point P3:
3.1.9.1 collared device— the intersection of the principal
axisofthecollar(L2)withthemedialsurfaceofthesteminthe
A-P projection.
3.1.9.2 collarless device—the intersection of the resection
plane (L2) with the medial surface of the stem in the A-P
projection.
3.1.10 Reference Point P4—the distal tip of the stem.
3.1.11 Reference Point P6 — the intersection of the canti-
lever plane with the medial surface of the stem in the A-P
projection.
3.1.12 R value—the R value is the ratio of the minimum
force to the maximum force.
minimum force
R 5
maximum force
3.1.13 Stem ReferenceAngle X—theanglebetweenthestem
reference line and the line of load application.
3.1.14 stem reference line—a line passing through Refer-
ence Point P6 and the center of the prosthesis head (P1).
3.1.15 supported stem length—the vertical distance be-
FIG. 2 Collarless Device
tween the distal tip of the stem (P4) and the cantilever plane.
3.1.16 unloaded moment arm—the perpendicular distance
5. Specimen Selection
between the line of load application and the geometric centroid
5.1 The specimen selection should have the same geometry
of the stem cross section at the cantilever plane.
as the final finished product, and the stem should be in the final
3.1.17 unsupported stem length—the vertical distance be-
finished condition.
tween Point P3 and the cantilever plane.
3.2 See Figs. 1 and 2.
6. Apparatus
6.1 Thespecimenshallbeconstrainedbyasuitablegrouting
4. Significance and Use
agent within a rigid cavity. A common grouting agent used is
4.1 This practice can be used to describe the effects of
poly methyl methacrylate (PMMA—bone cement) that is
materials, manufacturing, and design variables on the fatigue
polymerized in place. The minimum thickness of the grouting
resistance of metallic stemmed femoral components subjected
agent should be 1 cm. Although bone cement is the recom-
to cyclic loading for relatively large numbers of cycles. The
mended grouting agent, other material may be used provided it
recommended test assumes a “worst case‘‘ situation where
does not chemically or mechanically interact with the test
proximal support for the stem has been lost. It is also
specimen.
recognized that for some materials the environment may have
6.2 The test fixtures shall be constructed so that the line of
an effect on the response to cyclic loading. The test environ-
load application is in the implant anterior/posterior symmetry
ment used and the rationale for the choice of that environment
plane of the supported portion of the stem.
should be described in the report.
6.3 The test fixtures shall be constructed so that the line of
4.2 Itisrecognizedthatactual in vivoloadingconditionsare
load application passes through the ball center.
not constant amplitude. However, there is not sufficient infor-
6.4 A ball- or roller-bearing low-friction mechanism shall
mation available to crate standard load spectrums for metallic
be included in the loading apparatus to minimize loads not
stemmed femoral components. Accordingly, a simple periodic
perpendicular to the cantilever plane. An example of such a
constant amplitude force is recommended.
mechanism is included in Appendix X1.
4.3 In order for fatigue data on femoral stems to be useful
7. Equipment Characteristics
for comparison, it must be reproducible among different
laboratories. Consequently, it is essential that uniform proce-
7.1 The action of the machine should be analyzed to ensure
dures be established.
that the desired form and periodic force amplitude is main-
tained for the duration of the test. (See Practice E 467.)
7.2 The test machine should have a load monitoring system
such as the transducer mounted in line with the specimen. The
The reference points and lines are consistent with the Proposed Standard
test loads should be monitored continuously in the early stages
Specification for Cementable Total Hip Prostheses with Femoral Stems. The
of the test and periodically thereafter to ensure the desired load
reference points “P2” and “P5” in that proposed specification are not relevant to this
practice. Consequently, they are not used in this practice. cycle is maintained. The varying load as determined by
F1440–92 (2002)
suitable dynamic verification should be maintained at all times beginning of each test. Possible methods included dial gages,
to within 62 % of the maximum force being used. optical micrometers, or linear scales viewed with a strobe light
to slow the apparent motion of the deflection.
8. Procedure
9. Test Termination
8.1 Specimen Test Orientation—The angle between the
distal stem axis and the line of load application shall be 10 6
9.1 Continue the test until the specimen fails or until a
1° %. An example of a method to accomplish mounting the predetermined number of cycles has been applied to the
stem at the desired angle is given in Appendix X2.
specimen. Failure should be defined as a complete separation,
8.2 Specimen Mounting: or exceeding of a deflection limit on a test machine. In
8.2.1 Maintain the stem Reference Angle X within a range
reporting results, state the criteria selected for defining failure
of 61° over a test group. andthenumberofcyclesshownasthepredeterminedrunoutof
8.2.2 Maintain the unsupported stem length at 62 mm.
the test. Discard the data for a specific sample if the grouting
8.2.3 No relative motion between the prosthesis and the agent fractured prior to test completion.
grouting agent is permitted during hardening of the grouting
10. Report
agent.
8.2.4 The surface of the grouting agent at the cantilever
10.1 Report the fatigue test specimens, procedures, and
planeshallbeapproximatelylevelandperpendiculartotheline
results in accordance with Recommended Practice E 468.
of load application.
10.2 In addition, report the following parameters: Stem
8.2.5 An example of a technique for setting a specimen in
ReferenceAngle X, supported stem length, maximum force, R
the grouting agent in the correct orientation is given in
value,
...
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