ASTM F2665-21

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: F2665 − 09 (Reapproved 2014) F2665 − 21
Standard Specification for
Total Ankle Replacement Prosthesis
This standard is issued under the fixed designation F2665; 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 specification covers total ankle replacement (TAR) prostheses used to provide functioning articulation by employing talar
and tibial components that allow for a minimum of 15° of dorsiflexion and 15 to 25° (1) of plantar flexion, as determined by
non-clinical testing.
1.2 Included within the scope of this specification are ankle components for primary and revision surgery with modular and
non-modular designs, bearing components with fixed or mobile bearing designs, and components for cemented and/or cementless
use.
1.3 This specification is intended to provide basic descriptions of material and prosthesis geometry. In addition, those
characteristics determined to be important to inthe vivoin-vivo performance of the prosthesis are defined.
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.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 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:
F67 Specification for Unalloyed Titanium, for Surgical Implant Applications (UNS R50250, UNS R50400, UNS R50550, UNS
R50700)
This specification 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 July 15, 2014April 1, 2021. Published September 2014April 2021. Originally approved in 2009. Last previous edition approved in 20092014
as F2665F2665 – 09 (2014). - 09. DOI: 10.1520/F2665-09R14.10.1520/F2665-21.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2665 − 21
F75 Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants (UNS
R30075)
F86 Practice for Surface Preparation and Marking of Metallic Surgical Implants
F90 Specification for Wrought Cobalt-20Chromium-15Tungsten-10Nickel Alloy for Surgical Implant Applications (UNS
R30605)
F136 Specification for Wrought Titanium-6Aluminum-4Vanadium ELI (Extra Low Interstitial) Alloy for Surgical Implant
Applications (UNS R56401)
F138 Specification for Wrought 18Chromium-14Nickel-2.5Molybdenum Stainless Steel Bar and Wire for Surgical Implants
(UNS S31673)
F451 Specification for Acrylic Bone Cement
F561 Practice for Retrieval and Analysis of Medical Devices, and Associated Tissues and Fluids
F562 Specification for Wrought 35Cobalt-35Nickel-20Chromium-10Molybdenum Alloy for Surgical Implant Applications
(UNS R30035)
F563 Specification for Wrought Cobalt-20Nickel-20Chromium-3.5Molybdenum-3.5Tungsten-5Iron Alloy for Surgical Implant
Applications (UNS R30563) (Withdrawn 2005)
F565 Practice for Care and Handling of Orthopedic Implants and Instruments
F648 Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated Form for Surgical Implants
F732 Test Method for Wear Testing of Polymeric Materials Used in Total Joint Prostheses
F745 Specification for 18Chromium-12.5Nickel-2.5Molybdenum Stainless Steel for Cast and Solution-Annealed Surgical
Implant Applications (Withdrawn 2012)
F746 Test Method for Pitting or Crevice Corrosion of Metallic Surgical Implant Materials
F748 Practice for Selecting Generic Biological Test Methods for Materials and Devices
F799 Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Forgings for Surgical Implants (UNS R31537, R31538,
R31539)
F981 Practice for Assessment of Compatibility of Biomaterials for Surgical Implants with Respect to Effect of Materials on
Muscle and Insertion into Bone
F983 Practice for Permanent Marking of Orthopaedic Implant Components
F1044 Test Method for Shear Testing of Calcium Phosphate Coatings and Metallic Coatings
F1108 Specification for Titanium-6Aluminum-4Vanadium Alloy Castings for Surgical Implants (UNS R56406)
F1147 Test Method for Tension Testing of Calcium Phosphate and Metallic Coatings
F1160 Test Method for Shear and Bending Fatigue Testing of Calcium Phosphate and Metallic Medical and Composite Calcium
Phosphate/Metallic Coatings
F1223 Test Method for Determination of Total Knee Replacement Constraint
F1377 Specification for Cobalt-28Chromium-6Molybdenum Powder for Coating of Orthopedic Implants (UNS R30075)
F1472 Specification for Wrought Titanium-6Aluminum-4Vanadium Alloy for Surgical Implant Applications (UNS R56400)
F1537 Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNS R31537, UNS
R31538, and UNS R31539)
F1580 Specification for Titanium and Titanium-6 Aluminum-4 Vanadium Alloy Powders for Coatings of Surgical Implants
F1609 Specification for Calcium Phosphate Coatings for Implantable Materials
F1800 Practice for Cyclic Fatigue Testing of Metal Tibial Tray Components of Total Knee Joint Replacements
F1814 Guide for Evaluating Modular Hip and Knee Joint Components
F1877 Practice for Characterization of Particles
F2003 Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in Air
F2083 Specification for Knee Replacement Prosthesis
F2503 Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment
F2565 Guide for Extensively Irradiation-Crosslinked Ultra-High Molecular Weight Polyethylene Fabricated Forms for Surgical
Implant Applications
F2695 Specification for Ultra-High Molecular Weight Polyethylene Powder Blended With Alpha-Tocopherol (Vitamin E) and
Fabricated Forms for Surgical Implant Applications
F2943 Guide for Presentation of End User Labeling Information for Musculoskeletal Implants
2.2 ISO Standards:
ISO 6474ISO 6474-1 Implants for Surgery—Ceramic Materials—Part 1: Ceramic Materials Based on High-Purity Alumina
ISO 10993-1 Biological Evaluation of Medical Devices—Part 1: Evaluation and testing within a risk management process
ISO 13179-1 Implants for surgery—Plasma-sprayed unalloyed titanium coatings on metallic surgical implants—Part 1: General
requirements
ISO 13779-2 Implants for surgery—Hydroxyapatite—Part 2: Thermally sprayed coatings of hydroxyapatite
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
F2665 − 21
ISO 14243–2ISO 14243-2 Implants for Surgery—Wear of Total Knee-Joint Prostheses—Part 2: Methods of Measurement
ISO 22622 Implants for surgery—Wear of total ankle-joint prostheses—Loading and displacement parameters for wear-testing
machines with load or displacement control and corresponding environmental conditions for test
2.3 FDA Document:Documents:
21 CFR 888.6 Degree of Constraint
21 CFR 888.3110 Ankle Joint Metal/Polymer Semi-Constrained Cemented Prostheses
21 CFR 888.3120 Ankle Joint Metal/Polymer Non-Constrained Cemented Prostheses
2.4 ANSI/ASME Standard:
ANSI/ASME B46.1–1995 Surface Texture (Surface Roughness, Waviness, and Lay)
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 constraint, n—the relative inability of a TAR, inherent to its geometrical and material design, to be further displaced in a
specific direction under a given set of loading conditions.
3.1.2 dorsiflexion, n—rotation of the tibial component towards the anterior talar surface.
3.1.3 flexion, n—rotation of the talar component relative to the tibial component around the medial-lateral axis. Flexion is
considered positive when it is dorsiflexion, and negative when it is plantar flexion.
3.1.4 IE rotation, n—rotation of the tibial component relative to the talar component around the tibial axis. IE rotation is
considered positive when the tibial component rotates internally (clockwise when viewed proximally on the left ankle). IE rotation
is considered negative when the tibial component rotates externally.
3.1.5 interlock, n—mechanical design feature used to increase capture of one component within another and to restrict unwanted
displacement between components, thatcomponents (that is, component locking mechanism for modular components.components).
3.1.6 plantar flexion, n—rotation of the tibial component toward the posterior talar surface.
3.1.6 talar component, n—bearing member fixed to the talus for articulation with the tibial component. This could be metallic
or from some other suitably hard surface material.
3.1.7 radiographic marker, n—a nonstructural wire or bead designed to be apparent on X-rays taken after implantation for those
components that would otherwise not be apparent on such X-rays.
3.1.8 subluxation, n—instability or partial dislocation which occurs when the relative translational or rotational motion between
the talar and tibial components reaches an extreme where the two components would cease to articulate over the designated low
friction bearing friction-bearing surfaces.
3.1.9 talar component, n—bearing member fixed to the talus for articulation with the tibial component. This could be metallic or
from some other suitably hard surface material.
3.1.10 tibial component, n—fixed or mobile bearing member attached to the tibia for articulation with the talar component,
typically consisting of two major components,components: a metallic tibial tray and an ultra-high-molecular-weight polyethylene
(UHMWPE) (see Specification F648) bearing surface.
3.1.11 total ankle replacement (TAR), n—prosthetic parts that substitute for the natural opposing tibial and talar articulating
surfaces.
3.1.11 IE rotation, n—rotation of the tibial component relative to the talar component around the tibial axis. IE rotation is
considered positive when the tibial component rotates internally (clockwise when viewed proximally on the left ankle). IE rotation
is considered negative when the tibial component rotates externally.
Available from Food and Drug Administration (FDA), 5600 Fishers Ln., Rockville, MD 20857, http://www.fda.gov.
F2665 − 21
4. Classification
4.1 The following classification by degree of constraint is suggested for all total joint prostheses, including total ankle replacement
systems, based on the concepts adopted by the U.S. Food and Drug Administration (see 21 CFR 888.6).
4.1.1 Constrained—A constrained joint prosthesis prevents dislocation of the prosthesis in more than one anatomic plane and
consists of either a single, flexible, across the-joint across-the-joint component or more than one component linked together or
affined.
4.1.2 Semi-constrained—Semi-Constrained—A semi-constrained joint prosthesis limits translation or rotation, or both translation
and rotation of the prosthesis in one or more planes via the geometry of its articulating surfaces. Its components have no
across-the-joint linkages.
4.1.3 Non-constrained—Non-Constrained—A non-constrained joint prosthesis minimally restricts prosthesis movement in one or
more planes. Its components have no across-the-joint linkages.
4.2 Currently, most ankle designs are considered either semi-constrained or non-constrained. Most mobile bearing ankle
components are considered non-constrained. The US government 21 CFR 888.3110 identifies ankleU.S. government, in
21 CFR 888.3110, identifies “ankle joint metal/polymer semi-constrained cemented prosthesis and 21 CFR 888.3120 identifies
ankleprosthesis” and, in 21 CFR 888.3120, identifies “ankle joint metal/polymer non-constrained cemented prosthesis. prosthesis.”
5. Material
5.1 All devices conforming to this specification shall be fabricated from materials with adequate mechanical strength, durability,
corrosion resistance, and biocompatibility.
NOTE 1—The choice of materials is understood to be a necessary but not totally sufficient assurance of proper function of the device made from them.
5.1.1 Mechanical Strength—Various metallic components of total ankle replacement devices have been successfully fabricated
from materials, as examples, found in Specifications F75, F90, F136, F138, F562, F563, F745, F799, F1108, F1377, F1472, F1537,
and F1580. Polymeric bearing components have been fabricated from UHMWPE, as an for example, as specified in
SpecificationSpecifications F648 and F2695 and Guide F2565. Porous coatings have been fabricated from example materials
specified in Specifications F67, F75and, F75.and F1609; ISO 13779-2, and ISO 13179-1. Not all of these materials may possess
sufficient mechanical strength for critical, highly stressed components or for articulating surfaces. Conformance of a selected
material to its standard and successful clinical usage of the material in a previous implant design are not sufficient to ensure the
strength of an implant. Manufacturing processes and implant design can strongly influence the device’s performance
characteristics. Therefore, regardless of the material selected, the ankle implant must meet the performance requirements of Section
6.
5.1.2 Corrosion Resistance—Materials with limited or no history of successful use for orthopaedic implant application shall
exhibit corrosion resistance equal to or better than one of the materials listed in 5.1.1 when tested in accordance with Test Method
F746.
5.1.3 Biocompatibility—Materials Devices made from materials with limited or no history of successful use for orthopaedic
implant application shall be determined to exhibit acceptable biological response equal when tested in accordance with Practices
F748, F981to or better than one of the , or ISO 10993-1. While no known surgical implant material has ever been shown to be
completely free of adverse reactions in the human body, long-term clinical experience has shown an acceptable level of biological
response can be expected if materials listed in 5.1.1 when tested are used. However, the specifications listed in 5.1.1 cover raw
materials and not finished medical devices, where the design and fabrication process of the device can impact biological response.
Hence, for a device made from material listed in 5.1.1, its biocompatibility shall be verified in accordance with Practices F748,
F981and, F981 for a given application.or ISO 10993-1, unless justification can be provided for why design and processing will
not impact the biocompatibility of the final, sterilized device.
5.1.4 Polymeric Component Oxidation Resistance—Polymeric components may be subject to degradation of mechanical or wear
performance due to oxidation and may need to be aged prior to subsequent mechanical testing following Practice F2003.
F2665 − 21
6. Performance Requirements
6.1 Component Function—Each component for total ankle arthroplasty is expected to function as intended when manufactured in
accordance with good manufacturing practices and to the requirements of this specification. The components shall be capable of
withstanding static and dynamic physiologic loads (1) without compromising their function for the intended use and environment.
All components used for experimental measures of performance shall be equivalent to the finished product in form and material.
Components shall be sterilized if the sterilization process will affect their performance.
NOTE 2—Computer models may be used to evaluate many of the functional characteristics if appropriate material properties and functional constraints
are included and the computer models have been validated with experimental tests.
6.1.1 Individual tibial (that is, tibial tray and bearing surface components) and talar components should be fatigue tested using
relevant or analogous test methods under appropriate loading conditions (including worst-case scenarios) to address loss of
supporting foundation leading to potential deformation and/or component fracture.
6.1.1.1 Tibial tray components may be evaluated in a manner similar to Test Method Practice F1800, with a loading moment value
chosen to compare with a clinically successful implant, or justified in other suitable ways for the design being tested) (2). In
choosing the loading moment, both the moment arm and the load used shall be specified with explanation as to how and why they
were chosen. Each of five specimens shall be tested for 10 million cycles with no failure. All tibial components designated by this
specification shall pass this minimum requirement.
6.1.1.2 Tibial bearing surface components shall be fatigue tested considering worst-case scenarios to demonstrate that the
component is able to withstand anticipated physiological loading conditions and is not susceptible to the failure modes that have
been reported in the literature (3-5). The worst-case scenarios should take into consideration loads, component sizes, thickness of
the plastic bearing insert, bony support, locking mechanism, edge loading, misalignments, and how these can affect the individual
design.
6.1.2 Contact area and contact pressure distributions may be determined at various flexion angles using one of several published
methods (6-11) to provide a representation of stresses applied to the bearing surfaces and to the components. Flexion angles of 0,
610,0°, 610°, and 615° are recommended. If the prosthesis is designed to function at higher angles of dorsiflexion or plantar
flexion, then it is recommended that these measurements be continued at 5° increments to the full range of motion. If these tests
are performed, it is important to maintain consistent test parameters and to evaluate other TAR prostheses under the same
conditions.
6.1.3 Range of motion in dorsiflexion and plantar flexion shall be greater than or equal to 15° (each) which is required for walking
(12-14). These measurements apply to components mounted in neutral alignment in bone or in an anatomically representative
substitute. It is critical to define the location of the neutral alignment position, for example, center of contact areas or patches, in
terms of dimensions from outside edges of the components. The initial positioning or location of the neutral alignment point will
affect the range of motion values for certain TAR prostheses. The range of flexion determined from non-clinical testing, therefore,
can be compromised by misalignments in various degrees of freedom. Worst-case scenario misalignments as well as neutral
alignment should be evaluated for dorsiflexion and plantar flexion range of motion testing.
NOTE 3—The nominal range of motion of a total ankle replacement can be estimated using the computer-aided drawingsdesign (CAD) of an implant. The
definition of zero degrees of ankle flexion for the implant should be reported. The actual maximum dorsiflexion and maximum plantar flexion should be
defined as the maximum angle at which the following conditions are met: (a1) bony impingement is not expected, (b2) the edges of the talar component
or tibial component do not dig into the UHMWPE bearing (if any), and (c3) the implant system can sustain a compressive load of 3600 N (approximately
5five average body weights) (13, 15) and a combination of the translational and rotational extreme laxity motions claimed in the design without
subluxation.
6.1.4 Total ankle replacement constraint data for internal-external rotation, anterior-posterior displacement, and medial-lateral
displacement should be determined for all total ankle joints in a manner similar to Test Method F1223 for total knees. Implants
should be tested at 0°, 610° and maximum flexion at a minimum.
6.2 All modular components shall be evaluated for the integrity of their connecting mechanisms. As suggested in Guide F1814,
static and dynamic shear tests, bending tests, and tensile tests or any combination may be necessary to determine the performance
characteristics. The connecting mechanisms shall show sufficient integrity for the range of loads anticipated for the application.
F2665 − 21
6.3 It is important to understand the wear performance for articulating surfaces. Any new or different material couple shall not
exceed the wear rates of the following material couple when tested under simulated physiological conditions, or if it does exceed
these rates its use shall be further justified. The current standard wear couple is CoCrMo alloy (see Specification F75) against a
fixed bearing UHMWPE (see Specification F648), both having prosthetic-quality surface finishes as described in 8.2 and 8.3.
6.3.1 Materials may be preliminarily tested in a pin-on-flat or pin-on-disk test apparatus such as described in Test Method F732
with
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