Standard Practice for Cyclic Fatigue Testing of Metallic Stemmed Hip Arthroplasty Femoral Components with Torsion (Withdrawn 2011)

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 in which proximal support for the stem has been lost. It is also recognized that, for some materials, the environment has an effect on the response to cyclic loading (see 12.7). The test environment used and rationale for the choice of that environment should be described in the test report.  
It is recognized that actual in vivo loading conditions are not constant amplitude. However, sufficient information is not available to create standard load spectrums for metallic stemmed femoral components. A simple periodic constant amplitude force is accordingly recommended.
SCOPE
1.1 This practice covers a method for the fatigue testing of metallic stemmed femoral components used in hip arthroplasty. The described method is intended to be used for evaluation in comparisons 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 femoral stems with modular heads, with the head in place. Such prostheses should not have an anterior-posterior A-P bow or a medial-lateral M-L bow, and they 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.
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.
WITHDRAWN RATIONALE
This practice covers a method for the fatigue testing of metallic stemmed femoral components used in hip arthroplasty. The described method is intended to be used for evaluation in comparisons 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.
Formerly under the jurisdiction of Committee F04 on Medical and Surgical Materials and Devices, this practice was withdrawn in November 2011.

General Information

Status
Withdrawn
Publication Date
30-Sep-2005
Withdrawal Date
17-Nov-2011
Current Stage
Ref Project

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ASTM F1612-95(2005) - Standard Practice for Cyclic Fatigue Testing of Metallic Stemmed Hip Arthroplasty Femoral Components with Torsion (Withdrawn 2011)
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:F1612–95 (Reapproved 2005)
Standard Practice for
Cyclic Fatigue Testing of Metallic Stemmed Hip Arthroplasty
Femoral Components with Torsion
This standard is issued under the fixed designation F1612; 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 E1150 Definitions of Terms Relating to Fatigue
2.2 ISO Document:
1.1 This practice covers a method for the fatigue testing of
ISO 7206-3 (1988) Stem Test
metallicstemmedfemoralcomponentsusedinhiparthroplasty.
The described method is intended to be used for evaluation in
3. Terminology (see Fig. 1 and Fig. 2)
comparisons of various designs and materials used for
3.1 Definitions of Terms Specific to This Standard:
stemmed femoral components used in the arthroplasty. This
3.1.1 cantilever plane—a plane perpendicular to the line of
practice covers procedures for the performance of fatigue tests
load application at the level on the stem at which the stem
using (as a forcing function) a periodic constant amplitude
becomes unsupported.
force.
3.1.2 distal stem axis—the centerline in the A-P projection
1.2 This practice applies primarily to one-piece prostheses
and the M-L projection of the most distal 50 mm of the stem.
and femoral stems with modular heads, with the head in place.
3.1.3 estimated maximum bending moment—the maximum
Suchprosthesesshouldnothaveananterior-posteriorA-Pbow
compressive load times the unloaded moment arm.
or a medial-lateral M-L bow, and they should have a nearly
3.1.4 geometric centroid (cantilever plane)— the point in a
straight section on the distal 50 mm of the stem. This practice
cross-sectional area of the cantilever plane whose coordinates
mayrequiremodificationstoaccommodateotherfemoralstem
arethemeanvaluesofthecoordinatesofallofthepointsinthe
designs.
area.
1.3 The values stated in SI units are to be regarded as the
3.1.5 line of load application—the loading axis of the test
standard.
machine.
1.4 This standard does not purport to address all of the
3.1.6 R value—the ratio of the minimum force to the
safety concerns, if any, associated with its use. It is the
maximum force,
responsibility of the user of this standard to establish appro-
minimum force
priate safety and health practices and determine the applica-
R 5
maximum force
bility of regulatory limitations prior to use.
3.1.7 Reference Line L1:
2. Referenced Documents
3.1.7.1 distal stem axis—the M-L centerline of the most
2.1 ASTM Standards:
distal 50 mm of stem in the A-P projection.
E4 Practices for Force Verification of Testing Machines
3.1.8 Reference Line L2:
E466 Practice for Conducting Force Controlled Constant
3.1.8.1 collared device—the plane of the distal side of the
Amplitude Axial Fatigue Tests of Metallic Materials
collar in the A-P projection.
E467 Practice for Verification of Constant Amplitude Dy-
3.1.8.2 collarless device—theresectionplanerecommended
namic Forces in an Axial Fatigue Testing System
for the device in the A-P projection.
E468 Practice for Presentation of Constant Amplitude Fa-
3.1.9 Reference Point P1—the spherical center of the pros-
tigue Test Results for Metallic Materials
thesis head.
3.1.10 Reference Point P3:
3.1.10.1 collared device—the intersection of the principal
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
axisofthecollar(L2)withthemedialsurfaceofthesteminthe
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.22 on Arthroplasty.
A-P projection.
Current edition approved Oct. 1, 2005. Published October 2005. Originally
3.1.10.2 collarless device—the intersection of the resection
approved in 1995. Last previous edition approved in 2000 as F1612 – 95 (2000).
plane (L2) with the medial surface of the stem in the A-P
DOI: 10.1520/F1612-95R05.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or projection.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
Withdrawn. 4th Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1612–95 (2005)
3.1.12 Reference Point P6 — the intersection of the canti-
lever plane with the medial surface of the stem in the A-P
projection.
3.1.13 stem reference angles—Since the distal stem axis is
obscurred by the grouting agent after preparation of the test
sample,thestemreferenceanglesaretobeusedtomeasurethe
repeatability of the stem orientation.They may also be used to
estimate the actual orientation of the distal stem to the line of
load application if the stem geometry is well known.
3.1.13.1 X (M-L)—the angle between the stem reference
line and line of load application in the M-L projection.
3.1.13.2 X (A-P)—theanglebetweenthestemreferenceline
and line of load application in the M-L and A-P projections.
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-
tween the distal tip of the stem (P4) and cantilever plane.
3.1.16 unloaded moment arm—the vector sum of the per-
pendicular distance between the line of load application and
geometric centroid of the stem cross section at the cantilever
plane in the A-P and M-L projections.
3.1.17 unsupported stem length—the vertical distance be-
tween Point P3 and the cantilever plane.
4. Significance and Use
4.1 This practice can be used to describe the effects of
materials, manufacturing, and design variables on the fatigue
FIG. 1 1(a) Collared Device, M-L Projection
resistance of metallic stemmed femoral components subjected
to cyclic loading for relatively large numbers of cycles. The
recommended test assumes a worst case situation in which
proximal support for the stem has been lost. It is also
recognized that, for some materials, the environment has an
effect on the response to cyclic loading (see 12.7). The test
environment used and rationale for the choice of that environ-
ment should be described in the test report.
4.2 Itisrecognizedthatactualinvivoloadingconditionsare
not constant amplitude. However, sufficient information is not
available to create standard load spectrums for metallic
stemmed femoral components. A simple periodic constant
amplitude force is accordingly recommended.
5. Purpose
5.1 In order for fatigue data on femoral stems to be useful
for comparison, it must be reproducible among different
laboratories. It is consequently essential that uniform proce-
dures for testing and reporting test data be established.
6. Apparatus
6.1 Thespecimenshallbeconstrainedbyasuitablegrouting
agent within a rigid cavity. A common grouting agent used is
polymethyl methacrylate (PMMA, bone cement). The mini-
mumthicknessofthegroutingagentshouldbe1cm.Although
FIG. 2 1(b) Collarless Device, M-L Projection
The reference points and lines are consistent with the proposed Specification
for CementableTotal Hip Prostheses with Femoral Stems.The Reference Points P2
and P5 in that specification are not relevant to this practice. Consequently, they are
3.1.11 Reference Point P4—the distal tip of the stem. not used in this practice.
F1612–95 (2005)
bone cement is the recommended grouting agent, other mate- suitable dynamic verification should be maintained at all times
rial may be used, provided that it does not alter the test to within 62% of the largest compressive force being used.
specimen chemically or mechanically.
9. Procedure
6.2 The test fixtures shall be constructed so that the line of
load application is in the implant A-P symmetry plane of the
9.1 Specimen Test Orientation—The angle between the
supported portion of the stem (Fig. 3). distal stem axis and the line of load application in the M-L
6.3 The test fixtures shall be constructed so that the line of
projection shall be 10 6 1° (Fig. 1 Fig. 2)), and the angle
load application passes through the ball center. between the distal stem axis and the line of load application in
6.4 Aballorrollerbearing,low-frictionmechanismshallbe
the A-P projection shall be 9 6 1° (Fig. 3). An example of a
included in the loading apparatus to minimize loads not method of accomplishing mounting the stem at the desired
perpendicular to the cantilever plane. An example of such a
angle is given in Appendix X1.
mechanism is included in Appendix X2. 9.2 Specimen Mounting:
9.2.1 Maintain the stem reference angles X (M-L) and X
7. Specimen Selection
(A-P) within a range of 61° over a test group.
7.1 The specimen selected should have the same geometry 9.2.2 Maintain the unsupported stem length within 62 mm.
asthefinalfinishedproduct,andthestemshouldbeinthefinal 9.2.3 Do not permit any relative motion between the pros-
finished condition. thesis and grouting agent during hardening of the grouting
7.2 The head of the prothesis should have the same geom- agent.
etry and surface finish as the final finished product, unless it 9.2.4 Keepthesurfaceofthegroutingagentatthecantilever
can be demonstrated that differences in the condition of the planeapproximatelylevelandperpendiculartothelineofload
head have no effect on the fatigue response of the stem in this application.
test. 9.2.5 An example of a technique for setting a specimen in
7.3 The length of the neck of the prosthesis contributes to the grouting agent in the correct orientation is given in
themagnitudeofthemaximumbendingmoment.Thelengthof Appendix X1.
neck(orheadoffset)shouldbethelongestpossiblethatwillbe 9.3 Test Frequency—Run all tests at a test frequency of 30
used with the femoral stem being evaluated. This will inher- Hz or less (see section 12.8).
ently maximize the maximum bending moment. 9.4 R Value—Run all tests with an R value of 10.0.
9.5 Measure the unsupported stem length, stem reference
8. Equipment Characteristics
angle, and moment arm for each specimen prior to testing. A
8.1 The action of the machine should be analyzed to ensure possible means would be to use a shadowgraph of the A-P
that the desired form and periodic force amplitude is main- projection as shown in Figs. 1-3.
tained for the duration of the test. (see Practice E467). 9.6 Measuretheamountofhorizontaldeflectionofthehead
8.2 The test machine should have a load monitoring system inboththeM-LandA-Pprojectionsinresponsetotheperiodic
forcing function one time after the beginning of each test (see
such as the transducer mounted in line with the specimen. The
test loads should be monitored continuously in the early stages section 12.9).
of the test and periodically thereafter to ensure that the desired
10. Test Termination
load profile is maintained. The varying load as determined by
10.1 Continue the test until the specimen fails or a prede-
termined number of cycles has been applied to the specimen.
Specimenfailureshouldbedefinedasacompleteseparationof
the specimen, or exceeding of a deflection limit on a test
machine. In reporting the results, state the criteria selected for
defining specimen failure and the number of cycles shown as
the predetermined runout of the test. Discard the data for a
specific sample if the grouting agent fails prior to test comple-
tion.
11. Report
11.1 Report the fatigue test specimens, procedures, and
results in accordance with Practice E468.
11.2 In addition, report the following parameters: stem
reference angles X (M-L) and X (A-P), unsupported stem
Instrictterms,sincetheforceappliedtotheheadiscompressive,themaximum
force is the largest algebraic value. The R value is consequently 10 when the
negative signs cancel each other.As a numeric example, assume a test is conducted
atapeakloadof3000N(−3000).Theleastcompressiveloadwouldbe10%ofthat,
or 300 N (−300). The R value would be−3000/−300, or 10. The R value would be
FIG. 3 Collared or Collarless Device, A-P Projection 0.1 in terms of applied bending moment at the cantilever plane.
F1612–95 (2005)
length, supported stem length, largest compressive force, R 12. Precision and Bias
value, specimen material, cycles to failure, estimated maxi-
12.1 The precision and bias of this practice is being
mum bending moment, location of fractures in relation to the
established.
cantilever plane, average dimensions of the stem cross section
in the cantilever plane, grouting agent, test environment, test
frequency, head/neck offset of the stem (neck length), and
deflection limit used to cut off testing (see 10.1). Test results that can be used to establish precision and bias are solicited.
APPENDIXES
(Nonmandatory Information)
X1. EXAMPLE PROSTHESIS MOUNTING PROCEDURE
X1.1 Adrawingorshadowgraphoftheprosthesisshouldbe ringstand and test tube holder can be used to grip the head of
available before mounting to establish the angular relationship the subject prosthesis.
between the distal stem axis and stem reference angle.
X1.3 The prosthesis is held by the head permitting the
X1.2 A gripping device, as illustrated in Fig. X1.1,ora
distal tip to rest on a flat surface. The angle jig illustrated in
Fig. X1.2 is positioned with the distal stem in the notch. The
stem is adjusted so that it is centered in the notch of the angle
jig.This will orient the distal stem at approximately 10° to the
line of load application. The head is now gripped firmly to
maintain the angular orientation of the stem.
X1.4 The angle jig can be removed and the prosthesis
mounted at the appropriate depth in an appropriate specimen
holder.
X1.5 Grouting material can be placed around the test
prosthesis into the specimen holder and permitted to harden.
X1.6 Thegripontheheadoftheprosthesisisreleasedafter
hardening of the grouting agent, and a shadowgraph may be
prepared of the profile of the test specimen and specimen
holder assembly.
X1.7 Asecondadjustablestopmaybeaddedbelowthegrip
and adjusted to rest against the medial surface of an appropri-
ately oriented prosthesis to facilitate repeatable mounting of
FIG. X1.1 Example of a Low-Friction Mechanism the test group.
X2. RATIONALE
X2.1 Thebreakageoffemoralstemsinhiparthroplastyhas stems. There are some problems with the proposed simplified
occurred in clinical application. The stem design, PMMA model. The worst case assumes that proximal cement break-
support, quality of bone, and other features contribute to stem down has already occurred. It does not address any features o
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