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for the
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Designation: F1800 − 12

Standard Practice for

Cyclic Fatigue Testing of Metal Tibial Tray Components of
Total Knee Joint Replacements1
This standard is issued under the fixed designation F1800; 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 (´) indicates an editorial change since the last revision or reapproval.

1. Scope 3. Terminology
1.1 This practice covers a procedure for the fatigue testing 3.1 Definitions:
of metallic tibial trays used in knee joint replacements. This 3.1.1 R value—The R value is the ratio of the minimum load
practice covers the procedures for the performance of fatigue to the maximum load.
tests on metallic tibial components using a cyclic, constant- minimum load
amplitude force. It applies to tibial trays which cover both the R5 (1)
maximum load
medial and lateral plateaus of the tibia. This practice may
require modifications to accommodate other tibial tray designs. 3.2 Definitions of Terms Specific to This Standard:
3.2.1 anteroposterior centerline—a line that passes through
1.2 This practice is intended to provide useful, consistent, the center of the tibial tray, parallel to the sagittal plane and
and reproducible information about the fatigue performance of perpendicular to the line of load application. For asymmetric
metallic tibial trays with one unsupported condyle. tibial tray designs, the appropriate center of the tibial tray shall
1.3 The values stated in SI units are to be regarded as be determined by the investigator and the rationale reported.
standard. No other units of measurement are included in this 3.2.2 fixture centerline—a line that passes through the center
standard. of the fixture, parallel to the anteroposterior centerline. This
1.4 This standard does not purport to address all of the line represents the separation between the supported and
safety concerns, if any, associated with its use. It is the unsupported portions of the test fixture.
responsibility of the user of this standard to establish appro- 3.2.3 mediolateral centerline—a line that passes through the
priate safety and health practices and determine the applica- center of the tibial tray, parallel to the coronal, or frontal, plane
bility of regulatory limitations prior to use. and perpendicular to the line of load application. For asym-
metric tibial tray designs, the appropriate center of the tibial
2. Referenced Documents tray shall be determined by the investigator and the rationale
reported.
2.1 ASTM Standards:2
E4 Practices for Force Verification of Testing Machines 3.2.4 moment arm, dap—the perpendicular distance between
E467 Practice for Verification of Constant Amplitude Dy- the mediolateral centerline of the tibia component and the line
namic Forces in an Axial Fatigue Testing System of load application.
E468 Practice for Presentation of Constant Amplitude Fa- 3.2.5 moment arm, dml—the perpendicular distance between
tigue Test Results for Metallic Materials the anteroposterior centerline of the tibia component and the
E1150 Definitions of Terms Relating to Fatigue (Withdrawn line of load application.
1996)3
4. Significance and Use
4.1 This practice can be used to describe the effects of
1
materials, manufacturing, and design variables on the fatigue
This practice is under the jurisdiction of ASTM Committee F04 on Medical and
performance of metallic tibial trays subject to cyclic loading
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.22 on Arthroplasty. for relatively large numbers of cycles.
Current edition approved Dec. 15, 2012. Published January 2013. Originally 4.2 The loading of tibial tray designs in vivo will, in general,
approved in 1997. Last previous edition approved in 2007 as F1800 – 07. DOI:
10.1520/F1800-12. differ from the loading defined in this practice. The results
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or obtained here cannot be used to directly predict in vivo
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM performance. However, this practice is designed to allow for
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
comparisons between the fatigue performance of different
3
The last approved version of this historical standard is referenced on metallic tibial tray designs, when tested under similar condi-
www.astm.org. tions.

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 F1800 − 12
4.3 In order for fatigue data on tibial trays to be comparable, the keel (see Fig. 2). The method of supporting (or not
reproducible, and capable of being correlated among supporting) any such feature shall be reported.
laboratories, it is essential that uniform procedures be estab-
lished. 6.4 A spacer of plastic possessing sufficient stiffness and
creep resistance (for example, ultra high molecular weight
5. Specimen Selection polyethylene, acetal co-polymer) shall be placed between the
tibial tray and the load applicator (see Fig. 3). The spacer shall
5.1 The test component selected shall have the same geom-
contain a spherical indentation (or recess) for the spherical
etry as the final product, and shall be in finished condition.
indenter. This recess shall be greater to or equal than the
6. Apparatus diameter of the spherical indenter and is included to minimize
the chance of spacer fracture under load. The spacer shall have
6.1 The tibial tray shall be mounted as a cantilever beam
a minimum thickness of 6 mm, measured at the dome of the
(see Fig. 1 and Fig. 2). Care shall be taken to ensure that the
sphere. It is recommended that the diameter of the spacer is 13
fixation of the tibial tray does not produce abnormal stress
mm.
concentrations that could change the failure mode of the part.
One possible setup involving fixation of the inferior surface or NOTE 1—Actual dimensions of the spacer may vary as smaller tibial
clamping of the superior surface is shown in Fig. 1 and Fig. 2. tray designs may require a smaller diameter disk.
If necessary, bone cement or other high strength epoxy may be
6.4.1 The spacer shall be placed on the unsupported tibial
used on the supported aspect of the tibial tray to prevent
condyle. The purpose of the spacer is to distribute load to the
loosening during the test.
tibial tray condyle and to eliminate possible fretting fatigue
6.2 The tibial tray shall be positioned such that the antero- initiated by contact between the metal indenter and the tibial
posterior centerline and the fixture centerline are aligned with tray.
an accuracy of 61 mm in the x direction and 62° in the x–y
plane (see Fig. 1 and Fig. 2). 6.5 The fixturing shall be constructed so that the load shall
be applied perpendicular to the undeflected superior surface of
6.3 When the tibial tray design includes a central keel or
the tibial tray.
other prominence, the proper method for support of the keel
must be determined. Depending on the tibial tray design, it may 6.6 Use one of the following two methods for determining
be necessary to evaluate the design with or without support of the position of the loading point.

FIG. 1 Schematic of Test Setup Without a Central Keel

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 F1800 − 12

FIG. 2 Schematic or Test Setup With a Central Keel

FIG. 3 Recommended Spacer Drawing

6.6.1 For tibial articulating surface designs that have a at 0° flexion and the position of the center of pressure
concave surface, the loading point shall be the intersection with determined. The loading point shall be the intersection of the
the tray of a line perpendicular to the tray which intersects the line perpendicular to the tray which intersects the center of the
deepest part of the concave recess of the articulating surface of pressure contact area.
the tibial component.
6.6.2 For other tibial designs, the femoral component, the NOTE 2—Optionally, define the worst-case scenario considering the
tibial articulating surface, and the tibial tray shall be assembled potential translation in the transverse plane and/or the potential axial

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 F1800 − 12
rotation (1)4 of the femoral component relative to the tibial baseplate, and 8.5 Test frequency—Run all tests at a frequency of 30 Hz or
apply 6.6.1 or 6.6.2. The rationale for the choice of femoral component less. Take care to ensure that the test machine can maintain the
placement relative to the tibial baseplate should be reported.
NOTE 3—If the geometry of the tibial baseplate superior surface
applied load at the chosen frequency and that resonant condi-
prevents using and dap and dml for the load application (for example, the tions are not reached.
presence of protrusion at the location of the theoretical load application), 8.6 R value—Run all tests with an R value of 10.0.
the rationale for the choice of the appropriate load location should be
reported (X1.6 is an example of the variation that could occur due to tibial NOTE 4—In strict terms, since the force applied to the tray is
baseplate misalignment). compressive, the maximum force is the smallest negative amplitude.
6.6.3 The dap and the dml shall be determined from either of Consequently, the R value is ten when the negative signs cancel each
other. In terms of applied bending moment at the cantilever plane, the R
the above techniques and will be used for all testing of that value would be 0.1. See Terminology E1150 for the definition of the R
design in that size. value.
6.7 The load shall be applied by means of a spherical 8.7 Measure the vertical deflection of the tibial tray using a
indenter, a diameter of 32 mm is recommended. dial gage, displacement transducer, and so forth. Record the
point at which the deflection is measured (that is, under the
7. Equipment Characteristics applied load, at the point of maximum deflection).
7.1 Perform the tests on a fatigue test machine with ad- 8.8 Report the test environment used.
equate load capacity.
7.2 Analyze the action of the machine to ensure that the 9. Test Termination
desired form and periodic force amplitude is maintained for the 9.1 Continue the test until the tibial tray fails or until a
duration of the test (see Practice E467 or use a validated strain predetermined number of cycles has been applied to the
gaged part). implant. The suggested number of cycles is ten million. Failure
7.3 The test machine shall have a load monitoring system may be defined as: a fracture of the tibial tray; formation of a
such as the transducer mounted in line with the specimen. crack detectable by eye, fluorescent dye penetrant, or other
Monitor the test loads continuously in the early stages of the non-destructive means; or exceeding a predetermined deflec-
test and periodically thereafter to ensure the desired load cycle tion limit.
is maintained. Maintain the varying load as determined by 10. Report
suitable dynamic verification at all times to within 62 % of the
largest compressive force being used. 10.1 Report the fatigue test specimens, procedures, and
results in accordance with Practice E468.
8. Procedure 10.2 In addition, report the following parameters: tibial tray
8.1 Determine the size of the tibial tray component used by material, spacer diameter and thickness, indenter diameter,
the investigator. Dimensions shall be reported. overall anteroposterior and mediolateral dimensions of the tray,
8.2 Position the test specimen such that the load axis is location of anteroposterior and mediolateral centerlines (for
perpendicular to the undeflected superior surface of the tray asymmetric tibial trays), tibial condyle loaded (for asymmetric
since the tray surface will not remain perpendicular to the load tibial trays), dml, dap, fixation method, largest compressive
axis during loading. load, R value, cycles to failure, mode and location of failures,
test environment, and test frequency. The method for determin-
8.3 Mount one side of a symmetric tibial component on the ing the loading location on the tibial tray (that is, dml, and dap)
fixture (see Fig. 1 and Fig. 2). Use the centerline of the tray to shall be documented.
distinguish between supported and non supported sides. If
asymmetrical, fix the tibial component such that a worst case 11. Precision and Bias
condition is tested. Report the criteria used to distinguish 11.1 A precision and bias statement does not exist for this
between supported and not supported sides. practice.
8.4 Apply the load by means of a spherical indenter.
12. Keywords
4
The boldface numbers given in parentheses refer to a list of references at the 12.1 arthroplasty; orthopaedic medical devices; tibial com-
end of the test. ponents; total knee arthroplasty

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 F1800 − 12
APPENDIX

(Nonmandatory Information)

X1. RATIONALE

X1.1 Fractures of tibial trays in TKR have occurred in to this rule. There may also be a reason why an investigator
clinical applications (2-6). The tray design, quality of bone, wishes to test a size that is not worst case. This practice may
and other features contribute to implant fracture. One recog- also be used for this purpose.
nizable mode of clinical failure occurs when the lateral portion
of the tray is firmly anchored while bone support of the medial X1.6 The tolerance chosen for the alignment of the tibial
condyle is absent. As the body loads are applied through the tray is based on finite element analysis of a tibial tray design
tray of the prosthesis, significant stresses can result at the area with and without a central keel. The analysis represents one
where the tray is still firmly supported. Because it is believed design under specific boundary conditions and is shown as one
that this lack of support is the primary reason behind fracture example of the variation that can occur due to tibial tray
of the tibial trays, this practice was chosen as a simplified misalignment. The results of this analysis were as follows:
model to use in fatigue testing of actual implants. Effect of Malignment (1 mm Shift)

Design Change in Stress from Correct Alignment

X1.2 It is recognized that for some materials the environ- no keel 4 % increase
ment may have an effect on the response to cyclic loading. The keel 8 % increase
test environment used and the rationale for that choice shall be Effect of Malrotation (5° Rotation)
described in the test report.
Design Change in Stress form Correct Alignment
no keel 5.5 % increase
X1.3 It is also recognized that actual in vivo loading keel 10 % increase
conditions are not constant amplitude. However, there is
The required tolerance limits (61 mm and 62°) were
insufficient information available to create standard load spec-
chosen to minimize the change in stress while ensuring a
trums for metallic tibial components. Accordingly, a simple
reasonable test setup.
periodic constant amplitude force is recommended.
X1.7 It is recommended that testing be terminated at ten
X1.4 Worst case loading of the tibial tray may vary depend- million cycles if failure of the tibial tray has not occurred. The
ing on material, design, and clinical indications. The researcher tibial tray design addressed in this testing are designed to
shall evaluate the possible clinical and design related failure replace the knee joint and intended to carry load over the life
modes and attempt to determine a worst case situation. As of the implant. Ten million cycles represents the number of
stated above, loss of medial bone support has been clinically loading cycles a tibial tray might experience over ten years of
and is thus incorporated in this practice. Additional factor that clinical use (estimated at one million loading cycles per year).
may be of importance include wear that has been reported in It is recognized that in this unsupported condition, the implant
the posterior medial region of the tibia (7). Also, as the method may not be required to withstand this number of loading cycles
of heat treatment can affect the strength of the tibial tray prior to revision.
material, it shall be considered. For example, the high tem-
perature sintering treatment used to apply a porous coating to X1.8 In developing this practice, it was recognized that
a tibial tray may affect the fatigue strength of the tibial tray. alternative methods for testing tibial trays exist. One such test
method would include placing a tibial insert in the metal tray
X1.5 The size of tibial tray to be tested shall be determined and applying load through femoral component with a greater
by the investigator. In general, the worst case size shall be distribution on the medial condyle (at a ratio of 60/40 or
chosen based on evaluation or experience, or both. In a design 80/20). This practice attempts to simplify the loading condi-
with a constant tray thickness, maximizing the dml will result in tions while addressing clinical failure modes of tibial tray
the largest moment arm and therefore the highest stresses in the designs. Based on various goals, investigators may seek to
tray; however, a tray of non-uniform thickness may not adhere deviate from the test method defined here.

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 F1800 − 12
REFERENCES

(1) Dennis, D. A., Komistek, M. R., Mahfouz, J. T., Outten, A. S., (5) Morrey, B. F., and Chao, E. Y. S, “Fracture of the Porous-Coated
“Mobile-Bearing Total Knee Arthroplasty: Do the Polyethylene Bear- Metal Tray of a Biologically Fixed Knee Prosthesis,” Clinical
ings Rotate?” Clinical Orthopedics and Related Research, 440, 2005, Orthopaedics and Related Research, No. 228 , March 1988, pp.
pp. 88–95. 182–189.
(2) Gradisar, I. A., Hoffman, B. S., and Askew, M. S., “Fracture of a (6) Scott, R. D., Ewald, F. C., and Walker, P. S., “Fracture of the Metallic
Fenestrated Metal Backing of a Total Knee Component,” Journal of Tibial Tray Following Total Knee Replacement: Report of Two
Arthroplasty, Vol. 4, No. 1, March 1989, pp. 27–30. Cases,” Journal of Bone and Joint Surgery, Vol. 66A , 780, June 1984.
(3) Koeneman, J. B., Johnson, R. M., Weinstein, A. M., and Dupont, J. A., (7) Wasielewski, R. C., Galante, J. O., Leighty, R. M., Naterajan, R. N.,
“Failure of Metal Tibial Trays,” 12th Annual Meeting of the Society and Rosenberg, A. G., “Wear Patterns on Retrieved Polyethylene
for Biomaterials, 146, 1986.
Tibial Inserts and Their Relationship to Technical Consideration
(4) Mendes, D. G., Brando, D., Galor, R. L., and Roffman, M., “Breakage
During Total Knee Arthroplasty,” Clinical Orthopaedics and Related
of the Metal Tray in Tibial Knee Replacement,” Orthopedics, Vol. 7,
Research, No. 299, February 1994, pp. 31–43.
No. 5, May 1984, pp. 860–862.

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