ASTM F3161-16

Standard Test Method for Finite Element Analysis (FEA) of Metallic Orthopaedic Total Knee Femoral Components under Closing Conditions

SIGNIFICANCE AND USE
2.1 This standard is applicable to the calculation of stresses seen on a knee femoral component when loaded in a manner described in this test method. This method can be used to establish the worst-case size for a particular implant family. When stresses calculated using this method were compared to the stresses measured from physical strain gauging techniques performed at one laboratory, the results correlated to within 9%.
SCOPE
1.1 This standard establishes requirements and considerations for the numerical simulation of metallic orthopaedic cemented and cementless total knee femoral components using Finite Element Analysis (FEA) techniques for the estimation of stresses and strains. This standard is only applicable to stresses below the yield strength, as provided in the material certification.  
1.2 Purpose—This test method establishes requirements and considerations for the development of finite element models to be used in the evaluation of metallic orthopaedic total knee femoral component designs for the purpose of prediction of the static implant stresses and strains. This procedure can be used for worst-case assessment within a family of implant sizes to provide efficiencies in the amount of physical testing to be conducted. Recommended procedures for performing model checks and verification are provided to help determine if the analysis follows recommended guidelines. Finally, the recommended content of an engineering report covering the mechanical simulation is presented.  
1.3 Limits—This document is limited in discussion to the static structural analysis of metallic orthopaedic total knee femoral components (which excludes the prediction of fatigue strength).  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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.

General Information

• Status: Published
• Publication Date: 31-Jan-2016
• 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

• Referred By: ASTM F2083-21 - Standard Specification for Knee Replacement Prosthesis (Withdrawn 2023)
• Effective Date: 01-Feb-2016
• Referred By: ASTM F3495-23 - Standard Test Methods for Determining the Static Failure Load of Ceramic Knee Femoral Components
• Effective Date: 01-Feb-2016
• Referred By: ASTM F3210-22e1 - Standard Test Method for Fatigue Testing of Total Knee Femoral Components Under Closing Conditions
• Effective Date: 01-Feb-2016

Overview

ASTM F3161-16: Standard Test Method for Finite Element Analysis (FEA) of Metallic Orthopaedic Total Knee Femoral Components under Closing Conditions provides a unified approach for the numerical simulation of metallic total knee femoral components using finite element analysis (FEA). The standard is focused on static structural analysis-specifically the assessment of stress and strain-under controlled loading and boundary conditions. This methodology is applicable to both cemented and cementless knee femoral implants and is limited to evaluating stresses below the material yield strength as defined in material certifications.

ASTM F3161-16 aims to support the development, verification, and reporting of FEA models, aiding in worst-case evaluations of implant families and reducing the need for exhaustive physical testing. It also issues recommendations on documenting the engineering analysis, ensuring that simulation results are reliable and reproducible.

Key Topics

• Scope of Simulation: Focuses on static structural analysis for metallic orthopaedic knee femoral components, excluding fatigue strength predictions.
• Model Development: Describes requirements for geometric representation, including the use of CAD models and justified simplifications to maximize relevance for simulation.
• Material Properties: Details use of modulus of elasticity and Poisson’s ratio from certified material data, emphasizing unit consistency with geometric inputs.
• Loading and Boundary Conditions: Specifies the application of test loads and the constraint of the anterior flange to replicate closing conditions typical in orthopedic evaluation.
• Mesh and Convergence: Recommends strategies for mesh refinement, convergence studies, and the use of tetrahedral or hexahedral elements to ensure accurate stress and strain prediction.
• Analysis and Reporting: Outlines the contents required in the final engineering report, including model details, boundary conditions, selection of peak stress regions, mesh study, and any assumptions or deviations from the standard methodology.
• Validation: Presents methods for comparing FEA results with physical strain gauge data, supporting the credibility of FEA as an alternative to physical testing.

Applications

• Product Development: Used by designers and engineers to evaluate new total knee femoral component designs, minimizing the need for physical prototypes and identifying worst-case designs within a product family.
• Regulatory Submissions: Supports evidence in regulatory filings for biomechanical performance and safety of knee implants, as it standardizes the simulation and documentation process.
• Quality Assurance: Enables manufacturers to verify consistency and reliability in implant design through validated computational simulations.
• Benchmark Testing: Offers benchmarking capabilities by correlating FEA-predicted stresses with strain gauge data, providing confidence in the use of computational models.

Related Standards

• ASTM F2083 - Standard Specification for Knee Replacement Prosthesis.
• ASTM F1264 - Standard Specification and Test Methods for Intramedullary Fixation Devices.
• ISO 7206-4 - Implants for surgery – Partial and total hip joint prostheses – Determination of endurance properties of stemmed femoral components.
• ASTM E1049 - Standard Practices for Cycle Counting in Fatigue Analysis.
• ISO 14243 - Implants for surgery – Wear of total knee-joint prostheses.

---

By following ASTM F3161-16, manufacturers, researchers, and regulatory bodies can ensure reliable finite element analysis in orthopedic implant evaluation. The standard streamlines the engineering process, fosters consistent reporting, and boosts confidence in implant safety prior to clinical use. With applications in product development, regulatory compliance, and quality control, this standard supports the broader adoption of validated computational simulation in orthopaedic device design.

Keywords: finite element analysis, FEA, knee femoral component, orthopedic implants, ASTM F3161-16, static structural analysis, model verification, implant simulation, biomechanical testing, regulatory submission.

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: F3161 − 16
Standard Test Method for
Finite Element Analysis (FEA) of Metallic Orthopaedic Total
Knee Femoral Components under Closing Conditions
This standard is issued under the fixed designation F3161; 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 described in this test method. This method can be used to
establish the worst-case size for a particular implant family.
1.1 This standard establishes requirements and consider-
When stresses calculated using this method were compared to
ations for the numerical simulation of metallic orthopaedic
the stresses measured from physical strain gauging techniques
cemented and cementless total knee femoral components using
performed at one laboratory, the results correlated to within
FiniteElementAnalysis(FEA)techniquesfortheestimationof
9%.
stresses and strains. This standard is only applicable to stresses
below the yield strength, as provided in the material certifica-
3. Geometric Data
tion.
3.1 Finite element models are based on a geometric repre-
1.2 Purpose—Thistestmethodestablishesrequirementsand
sentation of the device being studied. The source of the
considerations for the development of finite element models to
geometricdetailscanbeobtainedfromdrawings,solidmodels,
be used in the evaluation of metallic orthopaedic total knee
preliminary sketches, or any other source consistent with
femoral component designs for the purpose of prediction of the
defining the model geometry. In building the finite element
static implant stresses and strains. This procedure can be used
model, certain geometric details may be omitted from the
for worst-case assessment within a family of implant sizes to
orthopaedic implant geometry shown in the Computer Aided
provide efficiencies in the amount of physical testing to be
Design (CAD) model if it is determined that they are not
conducted. Recommended procedures for performing model
relevant to the intended analysis. Engineering judgment shall
checks and verification are provided to help determine if the
be exercised to establish the extent of model simplification and
analysis follows recommended guidelines. Finally, the recom-
shall be justified.
mendedcontentofanengineeringreportcoveringthemechani-
3.2 It is most appropriate to consider the worst-case stress
cal simulation is presented.
condition for the orthopaedic implant family being simulated.
1.3 Limits—This document is limited in discussion to the
The worst-case shall be determined from all relevant engineer-
static structural analysis of metallic orthopaedic total knee
ing considerations, such as femoral component geometry and
femoral components (which excludes the prediction of fatigue
dimensions. If finite element analysis is being used for deter-
strength).
mining the worst-case, then the worst-case size may not be
1.4 The values stated in SI units are to be regarded as
known. It may be necessary to run several sizes in order to
standard. No other units of measurement are included in this
determine the worst-case. If the FEA results do not conclu-
standard.
sively determine the worst-case configuration, a rationale
1.5 This standard does not purport to address all of the should be included (e.g., additional analysis or physical test-
safety concerns, if any, associated with its use. It is the ing) to justify the worst-case size.
responsibility of the user of this standard to establish appro-
4. Material Properties
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4.1 The required material properties for input into an FEA
model for the calculation of strains and displacement are
2. Significance and Use
modulus of elasticity (E) and Poisson’s ratio (ν). These values
2.1 This standard is applicable to the calculation of stresses
can typically be obtained from material certification data. It
seen on a knee femoral component when loaded in a manner
should be noted that the fatigue test is run under load control;
the FEAshould also be run under load control. When the FEA
This test method is under the jurisdiction ofASTM Committee F04 on Medical
is run under load control, the modulus of elasticity will not
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
affect the stress calculations under small displacement theory
F04.22 on Arthroplasty.
but will affect displacement and strain. The influence of
Current edition approved Feb. 1, 2016. Published March 2016. DOI: 10.1520/
F3161–16 Poisson’s ratio on the stress calculations is negligible.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3161 − 16
4.2 Ensure that material property units are consistent with
geometric units in the CAD model. SI units are the preferred
units of measurement.
5. Loading
5.1 Theloadinglocationandorientationofthekneefemoral
component shall be guided by the loading location and
boundary conditions described below. The areas of particular
interest are the stresses at the posterior aspect of the condyle,
anterior notch, and other design-specific critical regions.
5.2 The worst-case condyle shall be loaded. If the weaker
condyle cannot be justified, each condyle shall be analyzed
individually. Centrally locate a 7.62 mm diameter projected
circle over the apex of the posterior articulating surface with FIG. 2 Apply 1 N Load onto Load Footprint
the knee femoral component positioned in 90 degrees of
flexion.Apply an anterior directed 1 N load uniformly over the
face generated by the intersection of this projected circle with
the articulating surface. Refer to Fig. 1 and Fig. 2.
NOTE 1—Do not introduce additional solid material to the femoral
component model.
NOTE 2—It is recognized that the loading conditions in this test method
will not be identical to those of a physical testing standard currently under
development. However, the differences in loading conditions (e.g., load
application differences; potting level differences; use of bone cement
which is not modeled in FEA) do not significantly affect identification of
theworst-casestressconditionandconstructforsubsequentbenchtesting,
which is the primary objective of this test method.
5.3 Ensure that load units are consistent with material
property units.
6. Boundary Conditions
FIG. 3 Anterior Flange Constraint
6.1 The prescribed boundary condition idealizes embedding
the anterior flange within a potting medium. The femoral
7. Analysis
component shall be fixed in all translations on all “embedded”
7.1 The analysis and modeling system, programs or soft-
anteriorflangesurfaces.RefertoFig.1andFig.3.Ahorizontal
ware used for the finite element model creation and analysis
plane shall be constructed to define a closed perimeter around
should be capable of fully developing the geometric features
the anterior flange periphery. Note that the horizontal plane
andidealizingtheloadingandboundaryconditionenvironment
maynotbeparalleltotheanteriorflangebonecutface.Theuse
of the orthopaedic implant. An engineering justification shall
of other stress evaluation levels and/or constraint levels shall
be provided to support any assumptions and/or simplifications.
be justified.
7.2 The finite element mesh can be created using automatic
meshing, manual meshing, or a combination of the two
techniques. The overriding consideration is that the type, the
size, and the shape of the elements used must be able to
represent the expected behavior without significant numerical
limitation or complication. Most FEApackages have a built-in
program which checks the shape of the element for the type of
analysis selected. If this tool is not available, then additional
checks are needed.
7.3 The number and spacing of nodes (i.e. mesh density)
should be consistent with the type of element used and the type
of result desired. This may be demonstrated with a mesh
densitystudy,wherebyaseriesofmodelswithincreasingmesh
refinement in the critical stress regions is used to demonstrate
solution convergence. This allows the error associated with
subsequent models to be estimated. The method used to
demonstrate mesh convergence, in analysis cases where it is
not performed directly onto the model being analyzed, shall be
FIG. 1 Apex Location and Anterior Flange Constraint (lateral
view) documented in the FEA report. It is recommended that a
F3161 − 16
minimum of three mesh refinement levels be evaluated and a with any acceptable proprietary or non-proprietary engineering
model convergence of ≤5% be demonstrated on all measures report format; however, the report shall include, at a minimum,
and regions of interest. If differences in peak stresses between the following:
two sizes in a product family are calculated to be less than 5%,
8.1.1 A complete description of device being analyzed
a tightening of the model convergence is recommended to
including detailed dimensions. The report should reference a
increase the likelihood of establishing the worst-case size
source CAD geometry file by name and revision number. If the
within a product family. Reporting of the degrees of freedom is
evaluation is not being performed on the final design of the
not necessary if the model satisfies the convergence criterion.
device or if there are other significant assumptions that may
limit the use of the results, this shall be clearly stated.
7.4 The choice of element type is left to the analyst;
however, it is recommended for analysis of a knee femoral 8.1.2 A description of boundary constraints, loads, and
component that tetrahedral or hexahedral elements be used. If material properties. The source of the material property data
tetrahedral elements are considered, use of 4-noded elements utilized should be referenced.
should be avoided to prevent stress and strain incompatibilities
8.1.3 A summary of the finite element modeling and analy-
across elements. Additionally, the linear, 4-noded tetrahedron
sis system used for the analysis. If current versions of widely
element is a constant strain element. This means that displace-
used, commercially available software are used, this summary
ment interpolation is linear and the corresponding stresses and
can be by name and reference to the version used. For
strains are constant within any element. Therefore, a very
non-commercially available proprietary tools, or custom user
refined mesh is required around locations where high stress/
modification of commercially available software, sufficient
strain gradients are present when utilizing these elements.
technical background and results of test problems should be
When elements which are not
...