ASTM F3140-23

Standard Test Method for Cyclic Fatigue Testing of Metal Tibial Tray Components of Unicondylar Knee Joint Replacements

SIGNIFICANCE AND USE
4.1 This test method can be used to describe the effects of materials, manufacturing, and design variables on the fatigue performance of metallic tibial trays subject to cyclic loading for relatively large numbers of cycles.  
4.2 The loading of tibial tray designs in vivo will, in general, differ from the loading defined in this practice. The results obtained here cannot be used to directly predict in vivo performance. However, this practice is designed to allow for comparisons between the fatigue performance of different metallic tibial tray designs, when tested under similar conditions.  
4.3 In order for fatigue data on tibial trays to be comparable, reproducible, and capable of being correlated among laboratories, it is essential that uniform procedures be established.
SCOPE
1.1 This test method covers a procedure for the fatigue testing of metallic tibial trays used in partial knee joint replacements.  
1.2 This test method covers the procedures for the performance of fatigue tests on metallic tibial components using a cyclic, constant-amplitude force. It applies to tibial trays which cover either the medial or the lateral plateau of the tibia.  
1.3 This test method may require modifications to accommodate other tibial tray designs.  
1.4 This test method is intended to provide useful, consistent, and reproducible information about the fatigue performance of metallic tibial trays with unsupported mid-section of the condyle.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2023
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.22 - Arthroplasty

Relations

• Refers: ASTM E1823-24a - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 15-Feb-2024
• Refers: ASTM E1823-24 - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 01-Feb-2024
• Refers: ASTM E1823-20 - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 01-Feb-2020
• Refers: ASTM F1800-19 - Standard Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
• Effective Date: 01-Oct-2019
• Refers: ASTM F1800-19e1 - Standard Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
• Effective Date: 01-Oct-2019
• Refers: ASTM E1823-12e - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 15-Dec-2012
• Refers: ASTM F1800-12 - Standard Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
• Effective Date: 15-Dec-2012
• Refers: ASTM E1823-12d - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 15-Nov-2012
• Refers: ASTM E1823-12c - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 01-Sep-2012
• Refers: ASTM E1823-12b - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 01-Aug-2012
• Refers: ASTM E1823-12a - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 15-May-2012
• Refers: ASTM E1823-12 - Standard Terminology Relating to Fatigue and Fracture Testing
• Effective Date: 15-Mar-2012
• Refers: ASTM F2083-11 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Dec-2011
• Refers: ASTM E467-08e1 - Standard Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
• Effective Date: 01-Nov-2011
• Refers: ASTM E468-11 - Standard Practice for Presentation of Constant Amplitude Fatigue Test Results for Metallic Materials
• Effective Date: 01-Oct-2011

Overview

ASTM F3140-23 provides a standardized test method for cyclic fatigue testing of metallic tibial tray components used in unicondylar (partial) knee joint replacements. Developed by ASTM, this standard aims to establish reliable and reproducible procedures to assess the fatigue performance of metal tibial trays subjected to cyclic, constant-amplitude forces. By adopting unified testing practices, the standard supports meaningful comparison among different tibial tray designs and manufacturing methods, advancing the safety and effectiveness of orthopedic medical devices.

Key Topics

• Scope of Testing: Specifies procedures for evaluating the fatigue performance of metallic tibial trays used in unicondylar knee arthroplasty, addressing both medial and lateral tibial plateau components.
• Cyclic Fatigue Loading: Outlines the use of sinusoidal, constant-amplitude cyclic forces to simulate in-service loading conditions experienced by tibial trays during a knee replacement’s lifetime.
• Test Setup Requirements: Details for specimen preparation, alignment, loading positions, and fixture configuration, including the use of spacers and spherical indenters to replicate clinical conditions.
• Data Reporting and Analysis: Guidelines for recording test parameters, environmental control, cycles to failure, modes of failure, and results documentation to promote inter-laboratory comparability.
• Reproducibility and Comparability: Emphasizes the need for standardized procedures so that fatigue data can be shared, compared, and correlated across different laboratories and product designs.

Applications

ASTM F3140-23 is primarily used by medical device manufacturers, research laboratories, and regulatory bodies involved in the design, development, and quality assurance of partial knee replacement systems. Key practical applications include:

• Design Verification: Assess the fatigue strength of new metallic tibial tray components during the development of unicondylar knee systems.
• Comparative Evaluation: Compare the performance of different materials, designs, or manufacturing methods under controlled cyclic loading.
• Regulatory Submissions: Support evidence-based submissions for regulatory agencies by documenting compliance with a recognized international test method.
• Component Selection: Aid surgeons and procurement teams in selecting implants with verified fatigue performance for improved patient outcomes.
• Quality Control: Facilitate batch release and quality assurance testing by providing repeatable and standardized assessment procedures.

Related Standards

When implementing fatigue testing of tibial tray components, additional ASTM standards provide valuable context and guidance:

• ASTM E467 - Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
• ASTM E468 - Practice for Presentation of Constant Amplitude Fatigue Test Results for Metallic Materials
• ASTM E739 - Guide for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
• ASTM E1823 - Terminology Relating to Fatigue and Fracture Testing
• ASTM F1800 - Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
• ASTM F2083 - Specification for Knee Replacement Prosthesis

Practical Value

By following ASTM F3140-23, stakeholders in the orthopedic industry ensure high-quality, scientifically valid fatigue testing that:

• Enhances the understanding of material and design impacts on tibial tray durability.
• Reduces the risk of implant failure, improving patient safety and satisfaction.
• Supports regulatory approvals and market acceptance for innovative unicondylar knee devices.
• Offers a foundation for ongoing product improvement and clinical research in orthopaedic medical devices.

Keywords: cyclic fatigue testing, unicondylar knee replacements, tibial tray, orthopaedic medical devices, ASTM F3140-23, knee joint prosthesis, fatigue performance, test method, medical device standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3140 − 23
Standard Test Method for
Cyclic Fatigue Testing of Metal Tibial Tray Components of
Unicondylar Knee Joint Replacements
This standard is issued under the fixed designation F3140; 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 E467 Practice for Verification of Constant Amplitude Dy-
namic Forces in an Axial Fatigue Testing System
1.1 This test method covers a procedure for the fatigue
E468 Practice for Presentation of Constant Amplitude Fa-
testing of metallic tibial trays used in partial knee joint
tigue Test Results for Metallic Materials
replacements.
E739 Guide for Statistical Analysis of Linear or Linearized
1.2 This test method covers the procedures for the perfor-
Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
mance of fatigue tests on metallic tibial components using a
E1823 Terminology Relating to Fatigue and Fracture Testing
cyclic, constant-amplitude force. It applies to tibial trays which
F1800 Practice for Cyclic Fatigue Testing of Metal Tibial
cover either the medial or the lateral plateau of the tibia.
Tray Components of Total Knee Joint Replacements
F2083 Specification for Knee Replacement Prosthesis
1.3 This test method may require modifications to accom-
modate other tibial tray designs.
3. Terminology
1.4 This test method is intended to provide useful,
3.1 Definitions:
consistent, and reproducible information about the fatigue
3.1.1 R value—the R value, also known as the force ratio, is
performance of metallic tibial trays with unsupported mid-
the ratio of the minimum load to the maximum load. See
section of the condyle.
Terminology E1823.
1.5 The values stated in SI units are to be regarded as
minimum load
standard. No other units of measurement are included in this
R 5 (1)
maximum load
standard.
3.2 Definitions of Terms Specific to This Standard:
1.6 This standard does not purport to address all of the
3.2.1 anteroposterior (A/P) centerline—a line that passes
safety concerns, if any, associated with its use. It is the
through the center of the tibial tray, parallel to the sagittal
responsibility of the user of this standard to establish appro-
plane, perpendicular to the line of load application, and which
priate safety, health, and environmental practices and deter-
is ⁄2 the maximum tibial tray width in the M/L direction.
mine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accor-
3.2.2 distance, d —the perpendicular distance between the
ap
dance with internationally recognized principles on standard- mediolateral centerline of the tibia component and the point of
ization established in the Decision on Principles for the
load application.
Development of International Standards, Guides and Recom-
3.2.3 distance, d —the perpendicular distance from the
ml
mendations issued by the World Trade Organization Technical
anteroposterior centerline of the tibia component to the center
Barriers to Trade (TBT) Committee.
of the load application.
3.2.4 fixture centerline—a line that passes through the center
2. Referenced Documents
of the fixture, aligned with the anteroposterior centerline.
2.1 ASTM Standards:
3.2.5 mediolateral (M/L) centerline—a line that passes
through the center of the tibial tray, parallel to the coronal or
frontal plane, perpendicular to the line of load application, and
This test method is under the jurisdiction of ASTM Committee F04 on Medical
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
which is ⁄2 the maximum tibial tray length in the A/P direction.
F04.22 on Arthroplasty.
Current edition approved Sept. 1, 2023. Published September 2023. Originally
4. Significance and Use
approved in 2017. Last previous edition approved in 2017 as F3140 – 17. DOI:
10.1520/F3140-23.
4.1 This test method can be used to describe the effects of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
materials, manufacturing, and design variables on the fatigue
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
performance of metallic tibial trays subject to cyclic loading
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. for relatively large numbers of cycles.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3140 − 23
4.2 The loading of tibial tray designs in vivo will, in general, 6.1.1 The implant shall be placed on the rollers such that the
differ from the loading defined in this practice. The results distance between the centers of rollers shall not be less than
obtained here cannot be used to directly predict in vivo 80 % of the A/P distance as shown in Fig. 1. The roller contact
performance. However, this practice is designed to allow for lengths should overlap with the A/P centerline to minimize
comparisons between the fatigue performance of different moments causing rotation about the y-axis on Fig. 1.
metallic tibial tray designs, when tested under similar condi-
6.1.2 The implant should be sufficiently supported to allow
tions.
for bending forces to be applied while minimizing the moment
imparted about the A/P or M/L axis that would result in test
4.3 In order for fatigue data on tibial trays to be comparable,
instability. In some cases, this location may mask the worst-
reproducible, and capable of being correlated among
case M/L load location. An analysis should be conducted to
laboratories, it is essential that uniform procedures be estab-
find the physiological worst-case location and fixture may need
lished.
to be designed to accommodate this location.
5. Specimen Selection
6.2 The tibial tray shall be positioned such that the antero-
5.1 The test component selected shall have the same geom-
posterior centerline and the fixture centerline are aligned with
etry as the final product, and shall be in processed and finished
an accuracy of 61 mm in the x-direction and 62° in the x-y
condition.
plane (see Fig. 1).
6.3 When the tibial tray design includes a central keel or
6. Apparatus
other prominence, enough space shall be left under the tray to
6.1 The tibial tray shall be mounted as a three-point bend
prevent the keel from impacting during the deflection.
test. Care shall be taken to ensure that the three-point bend
fixture does not produce abnormal stress concentrations that 6.4 Apply the force by means of a spherical indenter of
could change the failure mode of the part, especially at the two either a diameter of 32 mm or use the femoral component at the
reaction locations. The reaction locations should include cy- tibiofemoral flexion angle that generates the smallest contact
lindrical rollers of 6 mm diameter to avoid constrained forces area between the femur and the tibial insert observed during
that will increase the run-out load. Deviation from cylindrical flexion between 0° and 60°, whichever is smaller, to be used as
rollers or the suggested diameter shall be justified in test worst-case loading condition. A spacer possessing sufficient
methods. One possible setup where walls are present on the stiffness and creep resistance (for example, ultra-high molecu-
anterior and posterior locations as well as medial lateral central lar weight polyethylene, acetal co-polymer) and a recom-
locations is shown in Fig. 1. These walls are necessary to mended circular footprint of 13 mm in diameter (see Fig. 2)
prevent a possible rotation or spit-out of the implant during the
shall be placed between the tibial tray and the load applicator
relatively high frequency fatigue test. Friction between the to act as a spacer. In the case of semi-constrained or monoblock
implant and the walls should be minimized. designs, it may be more appropriate to use the worst-case
FIG. 1 Schematic of Suggested Test Setup
F3140 − 23
determined. The loading point shall be the intersection of the
line perpendicular to the tray which intersects the center of the
pressure contact area.
NOTE 1—Optionally, define the worst-case scenario considering the
potential translation in the transverse plane and/or the potential axial
rotation (1) of the femoral component relative to the tibial baseplate, and
apply 6.6.1 or 6.6.2. The rationale for the choice of femoral component
placement relative to the tibial baseplate should be reported. Femoral
loading location that has the potential to generate worst-case stress
concentrations on the fixation features should be considered to address the
true worst-case loading location.
NOTE 2—If the geometry of the tibial baseplate superior surface
prevents using and d and d for the load application (for example, the
ap ml
presence of protrusion at the location of the theoretical load application),
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
baseplate misalignment). Investigators may elect to use the thinnest tibial
insert in lieu of the spacer for such a situation.
6.6.3 The d and the d shall be determined from either of
ap ml
the above techniques and will be used for all testing of that
design in that size.
7. Equipment Characteristics
7.1 Perform the tests on a fatigue test machine with ad-
equate load capacity.
FIG. 2 Suggested Spacer Drawing with Concave Top Surface
7.2 The dynamic loading waveform is sinusoidal at the
Cross Section Shown on Bottom Image
primary frequency. Analyze the action of the machine to ensure
(Actual dimensions of the spacer may vary as smaller tibial tray
that the desired form and periodic force amplitude is main-
designs may require a smaller diameter disk)
tained for the duration of the test (see Practice E467 or use a
validated strain-gaged part).
7.3 The test machine shall have a load and deflection
bearing. The choice of bearing used shall be justified in the
monitoring system such as the transducer mounted in line with
final report. This spacer shall contain an indentation conform-
the specimen. Monitor the test loads and deflections continu-
ing to the load applicator. The load applicator shall be a
ously in the early stages of the test and periodically thereafter
spherical indenter or the intended femoral component fixed at
to ensure the desired load cycle is maintained. Maintain the
a flexion angle consistent with the curvature representative of
varying load as determined by suitable dynamic verification at
the walking gait contact geometry. The spacer recess shall be
all times to within 62 % of the largest compressive force being
greater than or equal to the diameter of the load applicator.
used. An initial number of cycles of loading may need to be
6.4.1 The spacer shall be placed on the sulcus point of the
applied to reach the desired load parameters before the
tibial condyle. The purpose of the spacer is to distribute the
initiation of the test.
load to the tibial tray condyle and to eliminate possible fretting
7.3.1 Applied forces outside the 62 % deviation limit at the
fatigue initiated by contact between the metal indenter and the
beginning of the test will not invalidate the test. However,
tibial tray.
these cycles shall not be counted toward the completion count.
6.4.2 The thickness of the spacer, measured at the thinnest
Once counting begins, all cycles must be counted and the
point between the flat and indented surfaces, shall be no greater
applied forces must remain within the deviation limit.
than the equivalent dimension of the thinnest tibial bearing.
6.5 The fixturing shall be constructed so that the load is
8. Procedure
applied perpendicular to the undeflected superior surface of the
tibial t
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F3140 − 17 F3140 − 23
Standard Test Method for
Cyclic Fatigue Testing of Metal Tibial Tray Components of
Unicondylar Knee Joint Replacements
This standard is issued under the fixed designation F3140; 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
1.1 This test method covers a procedure for the fatigue testing of metallic tibial trays used in partial knee joint replacements.
1.2 This test method covers the procedures for the performance of fatigue tests on metallic tibial components using a cyclic,
constant-amplitude force. It applies to tibial trays which cover either the medial or the lateral plateau of the tibia.
1.3 This test method may require modifications to accommodate other tibial tray designs.
1.4 This test method is intended to provide useful, consistent, and reproducible information about the fatigue performance of
metallic tibial trays with unsupported mid-section of the condyle.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E467 Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
E468 Practice for Presentation of Constant Amplitude Fatigue Test Results for Metallic Materials
E739 Guide for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
E1823 Terminology Relating to Fatigue and Fracture Testing
F1800 Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
F2083 Specification for Knee Replacement Prosthesis
This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.22 on Arthroplasty.
Current edition approved Sept. 1, 2017Sept. 1, 2023. Published October 2017September 2023. Originally approved in 2017. Last previous edition approved in 2017 as
F3140 – 17. DOI: 10.1520/F3140-17.10.1520/F3140-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3140 − 23
3. Terminology
3.1 Definitions:
3.1.1 R value—the R value, also known as the force ratio, is the ratio of the minimum load to the maximum load. See Terminology
E1823.
minimumload
R 5 (1)
maximumload
minimumload
R 5 (1)
maximumload
3.2 Definitions of Terms Specific to This Standard:
3.2.1 anteroposterior (A/P) centerline—a line that passes through the center of the tibial tray, parallel to the sagittal plane and
plane, perpendicular to the line of load application.application, and which is ⁄2 the maximum tibial tray width in the M/L direction.
3.2.2 distance, d —the perpendicular distance between the mediolateral centerline of the tibia component and the point of load
ap
application.
3.2.3 distance, d —the perpendicular distance from the anteroposterior centerline of the tibia component to the center of the load
ml
application.
3.2.4 fixture centerline—a line that passes through the center of the fixture, aligned with the anteroposterior centerline.
3.2.5 mediolateral (M/L) centerline—a line that passes through the center of the tibial tray, parallel to the coronal, or frontal, plane
and coronal or frontal plane, perpendicular to the line of load application. application, and which is ⁄2 the maximum tibial tray
length in the A/P direction.
3.2.4 distance, d —the perpendicular distance between the mediolateral centerline of the tibia component and the point of load
ap
application.
3.2.5 distance, d —the perpendicular distance from the anteroposterior centerline of the tibia component to the center of the load
ml
application.
4. Significance and Use
4.1 This test method can be used to describe the effects of materials, manufacturing, and design variables on the fatigue
performance of metallic tibial trays subject to cyclic loading for relatively large numbers of cycles.
4.2 The loading of tibial tray designs in vivo will, in general, differ from the loading defined in this practice. The results obtained
here cannot be used to directly predict in vivo performance. However, this practice is designed to allow for comparisons between
the fatigue performance of different metallic tibial tray designs, when tested under similar conditions.
4.3 In order for fatigue data on tibial trays to be comparable, reproducible, and capable of being correlated among laboratories,
it is essential that uniform procedures be established.
5. Specimen Selection
5.1 The test component selected shall have the same geometry as the final product, and shall be in processed and finished
condition.
6. Apparatus
6.1 The tibial tray shall be mounted as a three-point bend test. Care shall be taken to ensure that the three-point bend fixture does
not produce abnormal stress concentrations that could change the failure mode of the part, especially at the two reaction locations.
The reaction locations should include cylindrical rollers of 6mm 6 mm diameter to avoid constrained forces that will increase the
run-out load. Deviation from cylindrical rollers or the suggested diameter shall be justified in test methods. One possible setup
F3140 − 23
where walls are present on the anterior and posterior locations as well as medial lateral central locations is shown in Fig. 1. These
walls are necessary to prevent a possible rotation or spit-out of the implant during the relatively high frequency fatigue test. Friction
between the implant and the walls should be minimized.
6.1.1 The implant shall be placed on the rollers such that the distance between the centers of rollers shall not be less than 80 %
of the A/P distance as shown in Fig. 1. The roller contact lengths should overlap with the A/P centerline to minimize moments
causing rotation about the y axis y-axis on Fig. 1.
6.1.2 The implant should be sufficiently supported to allow for bending forces to be applied while minimizing the moment
imparted about the A/P or M/L axis that would result in test instability. In some cases, this location may mask the worst-case M/L
load location. An analysis should be conducted to find the physiological worst-case location and fixture may need to be designed
to accommodate this location.
6.2 The tibial tray shall be positioned such that the anteroposterior centerline and the fixture centerline are aligned with an
accuracy of 61 mm in the x direction x-direction and 62° in the x–yx-y plane (see Fig. 1).
6.3 When the tibial tray design includes a central keel or other prominence, enough space shall be left under the tray to prevent
the keel from impacting during the deflection.
6.4 Apply the force by means of a spherical indenter of either a diameter of 32 mm or use the femoral component at the
tibiofemoral flexion angle that generates the smallest contact area between the femur and the tibial insert observed during flexion
between 0° and 60°, whichever is smaller, to be used as worst-case loading condition. A spacer possessing sufficient stiffness and
creep resistance (for example, ultra-high molecular weight polyethylene, acetal co-polymer) and a recommended circular footprint
of 13 mm in diameter (see Fig. 2) shall be placed between the tibial tray and the load applicator to act as a spacer. In the case of
semi-constrained or monoblock designs, it may be more appropriate to use the worst-case bearing. The choice of bearing used shall
be justified in the final report. This spacer shall contain an indentation conforming to the load applicator. The load applicator shall
be a spherical indenter or the intended femoral component fixed at a flexion angle consistent with the curvature representative of
the walking gait contact geometry. The spacer recess shall be greater than or equal to the diameter of the load applicator.
6.4.1 The spacer shall be placed on the sulcus point of the tibial condyle. The purpose of the spacer is to distribute the load to
the tibial tray condyle and to eliminate possible fretting fatigue initiated by contact between the metal indenter and the tibial tray.
FIG. 1 Schematic of Suggested Test Setup
F3140 − 23
FIG. 2 Suggested Spacer Drawing Withwith Concave Top Surface Cross-section Cross Section Shown on Bottom Image
(Actual dimensions of the spacer may vary as smaller tibial tray
designs may require a smaller diameter disk.)disk)
6.4.2 The thickness of the spacer, measured at the thinnest point between the flat and indented surfaces, shall be no greater than
the equivalent dimension of the thinnest tibial bearing.
6.5 The fixturing shall be constructed so that the load is applied perpendicular to the undeflected superior surface of the tibial tray.
6.6 Use one of the following two methods for determining the position of the loading point. point:
6.6.1 For tibial articulating surface designs that have a curved surface, the loading point shall be the intersection with the tray of
a line perpendicular to the tray which intersects the deepest part of the curved recess of the articulating surface of the tibial
component.
6.6.2 For other tibial designs, the femoral component, the tibial articulating surface, and the tibial tray shall be assembled at 0°
flexion and the position of the center of pressure determined. The loading point shall be the intersection of the line perpendicular
to the tray which intersects the center of the pressure contact area.
NOTE 1—Optionally, define the worst-case scenario considering the potential translation in the transverse plane and/or the potential axial rotation (1) of
the femoral component relative to the tibial baseplate, and apply 6.6.1 or 6.6.2. The rationale for the choice of femoral component placement relative to
the tibial baseplate should be reported. Femoral loading location that has the potential to generate worstcaseworst-case stress concentrations on the fixation
features should be considered to address the true worst-case loading location.
NOTE 2—If the geometry of the tibial baseplate superior surface prevents using and d and d for the load application (for example, the presence of
ap ml
protrusion at the location of the theoretical load application), 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 baseplate misalignment.)misalignment). Investigators may elect to use the thinnest tibial insert in
lieu of the spacer for such a situation.
6.6.3 The d and the d shall be determined from either of the above techniques and will be used for all testing of that design
ap ml
in that size.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
F3140 − 23
7. Equipment Characteristics
7.1 Perform the tests on a fatigue test machine with adequate load capacity.
7.2 The dynamic loading waveform is sinusoidal at the primary frequency. Analyze the action of the machine to ensure that the
desired form and periodic force amplitude is maintained for the duration of the test (see Practice E467 or use a validated strain
gaged strain-gaged part).
7.3 The test machine shall ha
...