ASTM F2423-11(2020)
(Guide)Standard Guide for Functional, Kinematic, and Wear Assessment of Total Disc Prostheses
Standard Guide for Functional, Kinematic, and Wear Assessment of Total Disc Prostheses
SIGNIFICANCE AND USE
4.1 This guide can be used to determine the fatigue and wear behavior of IVD prostheses subjected to functional and kinematic cyclic loading/motion for relatively large numbers of cycles (for example, various designs of IVD prostheses, as well as the effects of materials, manufacturing techniques and other design variables on one particular design can be determined using this guide).
4.2 This guide is intended to be applicable to IVD prostheses that support load and transmit motion by means of an articulating joint or by use of compliant materials. Ceramics, metals, or polymers, or combination thereof, are used in IVD prostheses, and it is the goal of this guide to enable a kinematic wear and/or fatigue comparison of these devices, regardless of material and type of device.
SCOPE
1.1 This guide provides guidance for wear and/or fatigue testing of total disc prostheses under functional and kinematic conditions and, to this end, describes test methods for assessment of the wear or functional characteristics, or both, of total disc prostheses.
1.2 Both lumbar and cervical prostheses are addressed.
1.3 Load and kinematic profiles for lumbar and cervical devices are not identical and, therefore, are addressed separately in the guide.
1.4 Partial disc replacements, such as nucleus replacements or facet joint replacements, are not intended to be addressed.
1.5 Wear is assessed using a weight loss method in a testing medium as defined in this guide.
1.6 This guide does not address any potential failure mode as it relates to the fixation of the implant to its bony interfaces.
1.7 It is the intent of this guide to enable comparison of intervertebral disc (IVD) prostheses with regard to wear and fatigue characteristics when tested under the specified conditions. It must be recognized, however, that there are many possible variations in in-vivo conditions. A single laboratory simulation with a fixed set of parameters might not be universally representative.
1.8 Most IVD prostheses primarily fall into two classifications: articulating ball-in-socket type prostheses, and elastomeric or compliant type prostheses. For the former, this guide primarily addresses Mode 1 wear (defined in 3.2.17.1); whereas for the latter, this guide addresses potential failure of the prosthesis when the implant is subjected to a range of motion and/or loads that fall within the full range of possible physiologic motions and loads.
1.9 For articulating components, this guide predominantly describes a Mode 1 test. The user is cautioned that other modes of wear may occur and may have significant influence on the functionality and performance of an articulating IVD prosthesis; therefore, the user should consider the effects of other wear modes on the performance of the prosthesis.
1.10 In order that the data be reproducible and comparable within and between laboratories, it is essential that uniform procedures are established. This guide is intended to facilitate uniform methods for testing and reporting of data for total disc replacement prostheses.
1.11 Without a substantial clinical retrieval history of IVD prostheses, actual loading profiles and patterns cannot be delineated at the time of the writing of this guide. It therefore follows that the load and motion conditions specified by this guide do not necessarily accurately reproduce those occurring in vivo. Rather, this guide provides useful boundary/endpoint conditions for evaluating prosthesis designs in a functional manner.
1.12 The values stated in SI units are to be regarded as the standard with the exception of angular measurements, which may be reported in either degrees or radians.
1.13 This guide is not intended to be a performance standard. It is the responsibility of the user of this guide to characterize the safety and effectiveness of the prosthesis under evaluation.
1.14 This standard does not purport to address all of t...
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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: F2423 − 11 (Reapproved 2020)
Standard Guide for
Functional, Kinematic, and Wear Assessment of Total Disc
Prostheses
This standard is issued under the fixed designation F2423; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope motion and/or loads that fall within the full range of possible
physiologic motions and loads.
1.1 This guide provides guidance for wear and/or fatigue
testing of total disc prostheses under functional and kinematic
1.9 For articulating components, this guide predominantly
conditions and, to this end, describes test methods for assess-
describesaMode1test.Theuseriscautionedthatothermodes
ment of the wear or functional characteristics, or both, of total
of wear may occur and may have significant influence on the
disc prostheses.
functionality and performance of an articulating IVD prosthe-
sis;therefore,theusershouldconsidertheeffectsofotherwear
1.2 Both lumbar and cervical prostheses are addressed.
modes on the performance of the prosthesis.
1.3 Load and kinematic profiles for lumbar and cervical
1.10 In order that the data be reproducible and comparable
devices are not identical and, therefore, are addressed sepa-
within and between laboratories, it is essential that uniform
rately in the guide.
procedures are established. This guide is intended to facilitate
1.4 Partial disc replacements, such as nucleus replacements
uniformmethodsfortestingandreportingofdatafortotaldisc
or facet joint replacements, are not intended to be addressed.
replacement prostheses.
1.5 Wearisassessedusingaweightlossmethodinatesting
1.11 Without a substantial clinical retrieval history of IVD
medium as defined in this guide.
prostheses, actual loading profiles and patterns cannot be
1.6 This guide does not address any potential failure mode
delineated at the time of the writing of this guide. It therefore
as it relates to the fixation of the implant to its bony interfaces.
follows that the load and motion conditions specified by this
guide do not necessarily accurately reproduce those occurring
1.7 It is the intent of this guide to enable comparison of
in vivo. Rather, this guide provides useful boundary/endpoint
intervertebral disc (IVD) prostheses with regard to wear and
conditions for evaluating prosthesis designs in a functional
fatigue characteristics when tested under the specified condi-
manner.
tions. It must be recognized, however, that there are many
possible variations in in-vivo conditions. A single laboratory
1.12 The values stated in SI units are to be regarded as the
simulation with a fixed set of parameters might not be
standard with the exception of angular measurements, which
universally representative.
may be reported in either degrees or radians.
1.8 Most IVD prostheses primarily fall into two classifica-
1.13 This guide is not intended to be a performance stan-
tions: articulating ball-in-socket type prostheses, and elasto-
dard. It is the responsibility of the user of this guide to
meric or compliant type prostheses. For the former, this guide
characterizethesafetyandeffectivenessoftheprosthesisunder
primarily addresses Mode 1 wear (defined in 3.2.17.1);
evaluation.
whereas for the latter, this guide addresses potential failure of
the prosthesis when the implant is subjected to a range of
1.14 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 appro-
1 priate safety, health, and environmental practices and deter-
This guide is under the jurisdiction ofASTM Committee F04 on Medical and
mine the applicability of regulatory limitations prior to use.
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.25 on Spinal Devices.
1.15 This international standard was developed in accor-
Current edition approved Oct. 1, 2020. Published November 2020. Originally
dance with internationally recognized principles on standard-
approved in 2005. Last previous edition approved in 2016 as F2423–11 (2016).
DOI: 10.1520/F2423-11R20. ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2423 − 11 (2020)
Development of International Standards, Guides and Recom- 3.2.2.1 origin, n—center of the global coordinate system
mendations issued by the World Trade Organization Technical which is located at the initial position of the total disc
Barriers to Trade (TBT) Committee. replacement’s instantaneous center of rotation (COR).
3.2.2.1 Discussion—Some articulating devices do not have
2. Referenced Documents
a single center of rotation, but instead have either a mobile
2.1 ASTM Standards: center of rotation or multiple distinct centers of rotation,
F561 Practice for Retrieval and Analysis of Medical depending on the direction of movement. In this case, the
Devices, and Associated Tissues and Fluids origin should be explicitly defined by the user with a rationale
F1582Terminology Relating to Spinal Implants for that definition.
F1714GuideforGravimetricWearAssessmentofProsthetic
3.2.2.2 X-axis, n—positive X-axis is a global fixed axis
Hip Designs in Simulator Devices
relative to the test machine’s stationary base, and is to be
F1877Practice for Characterization of Particles
directed anteriorly relative to the specimen’s initial unloaded
F2077TestMethodsForIntervertebralBodyFusionDevices
position.
2.2 ISO Standard:
3.2.2.3 Y-axis, n—positive Y-axis is a global fixed axis
ISO 18192–1Implants for Surgery—Wear ofTotal Interver-
relative to the test machine’s stationary base, and is directed
tebral Spinal Disc Prostheses—Part 1: Loading and Dis-
laterally relative to the specimen’s initial unloaded position.
placement Parameters for Wear Testing and Correspond-
3.2.2.4 Z-axis, n—positive Z-axis is a global fixed axis
ing Environmental Conditions for Test
relative to the test machine’s stationary base, and is to be
3. Terminology directed superiorly relative to the specimen’s initial unloaded
position.
3.1 All functional and kinematic testing terminology is
3.2.2.5 x-axis, n—positive x-axis is a fixed axis relative to
consistent with the referenced standards (for example, Test
the IVD prosthesis and a moving axis relative to the global
Methods F2077, Terminology F1582, and so forth), unless
coordinate system, and is directed anteriorly relative to the
otherwise stated.
prosthesis.
3.2 Definitions:
3.2.2.6 y-axis, n—positive y-axis is a fixed axis relative to
3.2.1 axial load, n—theresultantforce, F ,appliedtothe
axial
the IVD prosthesis and a moving axis relative to the global
superior or inferior fixture-end plate that simulates the in-vivo
coordinate system, and is directed laterally relative to the
load that an IVD prosthesis (original healthy disc) must resist.
prosthesis.
3.2.1.1 Discussion—Based on a healthy disc, the primary
component would be an axial compressive force F in the 3.2.2.7 z-axis, n—positive z-axis is a fixed axis relative to
Z
the IVD prosthesis and a moving axis relative to the global
direction of the negative global Z axis, and it would pass
through the origin of the IVD prosthesis. Shear components in coordinate system, and is directed superiorly relative to the
prosthesis.
the XYplanewouldbe F and F .Lateralbendingmoment M
X Y X
and flexion/extension moment M components would be cre-
3.2.3 degradation, n—loss of material or function or mate-
Y
atedabouttheoriginwhentheaxialloaddoesnotpassthrough
rial properties as a result of causes other than that associated
it.
with wear.
3.2.2 coordinate system/axes, n—global XYZ orthogonal
3.2.4 fluid absorption, n—fluid absorbed by the device
axesaredefinedfollowingaright-handedCartesiancoordinate
material during testing.
system in which the XY plane bisects the sagittal plane angle
3.2.5 functional failure, n—permanent deformation or wear
between the superior and inferior surfaces that are intended to
that renders the IVD prosthesis assembly ineffective or unable
simulate the adjacent vertebral end plates. The global axes are
to resist load/motion or any secondary effects that result in a
stationary relative to the IVD prosthesis’s inferior end plate
reduction of clinically relevant motions or the motions in-
fixture, which, in this guide, is also considered to be stationary
tended by the design of the device.
with respect to the test machine’s frame. Lower case letters,
3.2.6 interval net volumetric wear rate VR during cycle
i
xyz, denote a local, moving orthogonal coordinate system
interval i (mm /million cycles), n—VR = WR/ρ, where ρ =
i i
attached to the superior end plate fixture with directions
mass density (for example, units of g/mm ) of the wear
initially coincident with those of the global XYZ axes, respec-
material.
tively. The 3-D motion of the superior relative to the inferior
3.2.7 interval net wear rate WR during cycle interval i
i
end plate fixture is specified and is to be measured in terms of
(g/million cycles), n—WR =((NW – NW )/(number of cycles
sequential Eulerian angular rotations about the xyz axes, i i i-1
in interval i))×10 .
respectively (z, axial rotation; x, lateral bending; and y,
3.2.7.1 Discussion—For i=1, NW =0.
flexion-extension). i-1
3.2.8 intervertebral disc (IVD) prosthesis, n—nonbiologic
structure intended to restore the support and motion or a
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
portion thereof between adjacent vertebral bodies.
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
3.2.9 kinematic profile, n—relativemotionbetweenadjacent
the ASTM website.
vertebral bodies that the IVD prosthesis is subjected to while
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. being tested.
F2423 − 11 (2020)
TABLE 1 Test Profiles and Associated Parameters for Cervical
3.2.10 limit, n—a significant change in stiffness during a
IVD Prostheses
given motion, indicating the implant has reached its designed
Preferred Alternate
endpoint in range of motion.
Axial
Displacement Control: Load Control:
Test Profile Load, N
3.2.11 load profile, n—loading that the device experiences Range of Motion Applied Moment
(2-4)
A
(ROM), degree (3) Ranges, Nm (3)
while being tested under an applied kinematic profile or the
Flexion/extension 100 ±7.5 ±2.0
loading that the IVD prosthesis is subjected to if tested in load
Lateral bend/ 100 ±6 ±2.0
control.
rotation ±6 ±4.0
A
3.2.12 mechanical failure, n—failure associated with a de-
TheuseroftheguidemustdeterminewhethertheROM(rangeofmotion)willbe
equally divided between flexion and extension or weighted more toward one of the
fect in the material (for example, fatigue crack) or of the
motion directions.
bonding between materials that may or may not produce
functional failure.
3.2.13 net wear NW of wear specimen (g), n—NW 5~W
i i 0
4.2 This guide is intended to be applicable to IVD prosthe-
2W 1 S 2S ; loss in weight of the wear specimen corrected
! ~ !
i i 0
ses that support load and transmit motion by means of an
for fluid absorption at end of cycle interval i.
articulating joint or by use of compliant materials. Ceramics,
3.2.14 net volumetric wear NV of wear specimen (mm ),
i
metals, or polymers, or combination thereof, are used in IVD
n—NV 5NW/ρ atendofcycleinterval iwhere ρ=massdensity
i i
prostheses,anditisthegoalofthisguidetoenableakinematic
(for example, in units of g/mm ) of the wear material.
wear and/or fatigue comparison of these devices, regardless of
3.2.15 run out (cycles), n—maximum number of cycles that material and type of device.
a test needs to be carried to if functional failure has not yet
5. Apparatus
occurred.
5.1 Total Disc Prosthesis Components—The total disc re-
3.2.16 wear, n—progressive loss of material from the de-
placement may comprise a variety of shapes and configura-
vice(s)asaresultofrelativemotionatthesurfacesasmeasured
tions. Some known forms include ball-and-socket articulating
by the change in mass of the IVD prosthesis or components of
joints, biconcave joints having a free-floating or semi-
the IVD prosthesis.
constrained third body, metallic endplates bonded to elastomer
3.2.16.1 Discussion—In the case of a nonarticulating, com-
cores, and single-axis hinge joints.
pliant IVD prosthesis, wear is defined simply as the loss of
material from the prosthesis. Note that inferior and superior
5.2 Spinal Testing Apparatus:
bone interface components are excluded from this definition;
5.2.1 Test Chambers—Incaseofamulti-specimenmachine,
see 5.2.2.
each chamber shall be isolated to prevent cross-contamination
of the test specimens. The chamber shall be made entirely of
3.2.17 Wear modes (1) for articulating type designs:
noncorrosive components (such as acrylic plastic or stainless
3.2.17.1 Mode 1 refers to the articulation between two
steel), and shall be easily removable from the machine for
primary bearing surfaces only.
thorough cleaning between tests.
3.2.17.2 Mode 2 occurs whenever a primary surface articu-
5.2.2 Component Clamping/Fixturing—Since the purpose
lates directly against a secondary, nonbearing surface.
of the test is to characterize the wear and/or fatigue properties
3.2.17.3 Mode 3 occurs when the two primary bearing
of the IVD prosthesis under functional and kinematic
surfaces are still articulating together, but third-body particles
conditions, the method for mounting components in the test
have become entrapped between them.
chamber shall not compromise the accuracy of assessment of
3.2.17.4 Mode 4 refers to any contact and motion occurring
the weight loss or stiffness variation during the test. For
between two secondary, nonbearing surfaces.
example, prostheses having complicated superior and inferior
3.2.18 weight S of soak control specimen (g), n—S initial
i 0
surfaces for contacting bone (for example, sintered beads,
and S at end of cycle interval i.
i
hydroxylapatite (HA) coating, plasma spray) may be specially
3.2.19 weight W of wear specimen (g), n—W initial and
i 0
manufactured to modify that surface in a manner that does not
W at end of cycle interval i.
i
affect the wear simulation.
5.2.3 The device sho
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