ASTM F2624-12(2020)
(Test Method)Standard Test Method for Static, Dynamic, and Wear Assessment of Extra-Discal Single Level Spinal Constructs
Standard Test Method for Static, Dynamic, and Wear Assessment of Extra-Discal Single Level Spinal Constructs
ABSTRACT
This test method deals with static, dynamic, and wear testing of extra-discal motion preserving implants. These implants are intended to augment spinal stability without significant tissue removal while allowing motion of the functional spinal unit(s). Wear is assessed using a weight loss method and a dimensional analysis for determining wear of components used in extra-discal spinal motion preserving procedures, using testing medium as defined in this test method. This test method is not intended to address facet arthroplasty devices and any potential failure mode as it relates to the fixation of the device to its bony interfaces; and does not prescribe methods for assessing the mechanical characteristics of the device in translation. The static test includes the static flexion test, static extension test, static torsion test, static lateral bending test, and fatigue tests. Wear test includes flexion/extension wear assessment, rotational wear assessment, and bending wear assessment. The apparatus which shall be used includes implant components and spinal testing apparatus. The calculation and interpretation of wear results are also elaborated.
SIGNIFICANCE AND USE
4.1 This test method is designed to quantify the static and dynamic characteristics of different designs of single level spinal constructs. Wear may also be assessed for implants that allow motion using testing medium (see 6.1) for simulating the physiologic environment at 37 °C. Wear is assessed using a weight loss method in addition to dimensional analyses. Weight loss is determined after subjecting the implants to dynamic profiles specified in this test method. This information will allow the manufacturer or end user of the product to understand how the specific device in question performs under the test conditions prescribed in this test method.
4.2 This test method is intended to be applicable for single level extra-discal spinal constructs. Three different types of fixtures are specified for testing single level extra-discal spinal constructs See Fig. 2, Fig. 4, and Fig. 5. See also Table 1.
4.3 Implants may be designed using a variety of materials (for example, ceramics, metals, polymers, or combinations thereof), and it is the goal of this test method to enable a comparison of the static, dynamic, and wear properties generated by these devices, regardless of material and type of device.
SCOPE
1.1 This test method describes methods to assess the static and dynamic properties of single level spinal constructs.
1.2 An option for assessing wear using a weight loss method and a dimensional analysis is given. This method, described herein, is used for the analysis of devices intended for motion preservation, using testing medium as defined in this standard (6.1).
1.3 This test method is not intended to address any potential failure mode as it relates to the fixation of the device to its bony interfaces.
1.4 It is the intent of this test method to enable single level extra-discal spinal constructs with regard to kinematic, functional, and wear characteristics when tested under the specified conditions.
1.5 This test method is not intended to address facet arthroplasty devices.
1.6 In order that the data be reproducible and comparable within and between laboratories, it is essential that uniform procedures be established. This test method is intended to facilitate uniform testing methods and data reporting.
1.7 The motion profiles specified by this test method do not necessarily accurately reproduce those occurring in vivo. Rather this method provides useful boundary/endpoint conditions for evaluating implant designs in a functional manner.
1.8 This test method is not intended to be a performance standard. It is the responsibility of the user of this test method to characterize the safety and effectiveness of the device under evaluation.
1.9 Multiple test methods are included in this standard. However, it mu...
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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: F2624 − 12 (Reapproved 2020)
Standard Test Method for
Static, Dynamic, and Wear Assessment of Extra-Discal
Single Level Spinal Constructs
This standard is issued under the fixed designation F2624; 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 device design. In most instances, only a subset of the herein
described test methods will be required.
1.1 This test method describes methods to assess the static
and dynamic properties of single level spinal constructs. 1.10 The values stated in SI units are to be regarded as the
standard with the exception of angular measurements, which
1.2 Anoptionforassessingwearusingaweightlossmethod
may be reported in either degrees or radians. No other units of
and a dimensional analysis is given. This method, described
measurement are included in this standard.
herein, is used for the analysis of devices intended for motion
1.11 This standard does not purport to address all of the
preservation, using testing medium as defined in this standard
safety concerns, if any, associated with its use. It is the
(6.1).
responsibility of the user of this standard to establish appro-
1.3 Thistestmethodisnotintendedtoaddressanypotential
priate safety, health, and environmental practices and deter-
failuremodeasitrelatestothefixationofthedevicetoitsbony
mine the applicability of regulatory limitations prior to use.
interfaces.
1.12 This international standard was developed in accor-
1.4 It is the intent of this test method to enable single level
dance with internationally recognized principles on standard-
extra-discal spinal constructs with regard to kinematic,
ization established in the Decision on Principles for the
functional, and wear characteristics when tested under the
Development of International Standards, Guides and Recom-
specified conditions.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.5 This test method is not intended to address facet
arthroplasty devices.
2. Referenced Documents
1.6 In order that the data be reproducible and comparable
2.1 ASTM Standards:
within and between laboratories, it is essential that uniform
E2309Practices forVerification of Displacement Measuring
procedures be established. This test method is intended to
Systems and Devices Used in Material Testing Machines
facilitate uniform testing methods and data reporting.
F561 Practice for Retrieval and Analysis of Medical
1.7 The motion profiles specified by this test method do not
Devices, and Associated Tissues and Fluids
necessarily accurately reproduce those occurring in vivo.
F1714GuideforGravimetricWearAssessmentofProsthetic
Rather this method provides useful boundary/endpoint condi-
Hip Designs in Simulator Devices
tions for evaluating implant designs in a functional manner.
F1717Test Methods for Spinal Implant Constructs in a
Vertebrectomy Model
1.8 This test method is not intended to be a performance
F1877Practice for Characterization of Particles
standard. It is the responsibility of the user of this test method
F2003Practice for Accelerated Aging of Ultra-High Mo-
to characterize the safety and effectiveness of the device under
lecular Weight Polyethylene after Gamma Irradiation in
evaluation.
Air
1.9 Multiple test methods are included in this standard.
F2423Guide for Functional, Kinematic, and Wear Assess-
However, it must be noted that the user is not obligated to test
ment of Total Disc Prostheses
using all of the described methods. Instead, the user should
only select test methods that are appropriate for a particular 3. Terminology
3.1 All terminology is consistent with the referenced
standards, unless otherwise stated.
ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedical
andSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommittee
F04.25 on Spinal Devices. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2020. Published November 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2007. Last previous edition approved in 2016 as F2624–12 (2016). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/F2624-12R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2624 − 12 (2020)
3.2 Definitions: 3.2.5.1 origin—the center of the coordinate system is lo-
3.2.1 center of rotation (COR)—the point about which the cated at the center of rotation of the testing fixture.
simulated vertebral bodies rotate in performing the range of
3.2.5.2 X-Axis—the positive X-Axis is a global fixed axis
motion (ROM) specified in this test method.
relative to the testing machine’s stationary base and is to be
3.2.2 compressive bending stiffness (N/mm)—the compres-
directed anteriorly relative to the specimen’s initial unloaded
sive bending yield force divided by elastic displacement (see position.
the initial slope of line BC in Fig. 1).
3.2.5.3 Y-Axis—the positive Y-Axis is a global fixed axis
3.2.3 compressive bending ultimate load (N)—the maxi- relative to the testing machine’s stationary base and is directed
mum compressive force in the X-Z plane applied to a spinal
laterally relative to the specimen’s initial unloaded position.
implant assembly (see the force at Point E in Fig. 1). The
3.2.5.4 Z-Axis—the positive Z-Axis is a global fixed axis
ultimate load should be a function of the device and not of the
relative to the testing machine’s stationary base and is to be
load cell or testing machine.
directed superiorly relative to the specimen’s initial unloaded
3.2.4 compressive bending yield load (N)—the compressive
position.
bending force in the X-Z plane necessary to produce a
3.2.6 degradation—loss of material, function, or material
permanent deformation equal to 0.020 times the active length
properties due to causes other than wear.
of the longitudinal element (see the force at Point D in Fig. 1).
3.2.7 elastic displacement (mm or degrees)—the displace-
3.2.5 coordinate system/axes—three orthogonal axes are
ment at 2% offset yield (see PointAin Fig. 1) minus the 2%
defined following a right-handed Cartesian coordinate system.
offset displacement (see Point B in Fig. 1). (The distance
The XY plane bisects the sagittal plane between the superior
between Point A and Point B in Fig. 1.)
and inferior surfaces that are intended to simulate the adjacent
3.2.8 fluid absorption—fluid absorbed by the device mate-
vertebral end plates. The positive Z axis is to be directed
rial during testing or while implanted in vivo.
superiorly.Forcecomponentsparalleltothe XYplaneareshear
components of loading.The compressive axial force is defined 3.2.9 functional failure—permanent deformation or wear
to be the component in the negative Z direction.Torsional load that renders the implant assembly ineffective or unable to
is defined to be the component of moment about the Z-axis. adequately resist load/motion or any secondary effects that
FIG. 1 Typical Force Displacement Curve
F2624 − 12 (2020)
result in a reduction of clinically relevant motions or the 3.2.20 stiffness (N/mm or N-m/degree)—the slope of the
motions intended by the design of the device. initial linear portion of the force-displacement or moment-
degree curve (the slope of Line OG in Fig. 1).
3.2.10 interval net volumetric wear rate—VR during cycle
i
3.2.21 test block—the component of the test apparatus for
interval i (mm /million cycles):
mounting a single level spinal construct for the intended test
WR
i
configuration (Fig. 3).
VR 5
i
ρ
3.2.22 torsional aspect ratio—the active length of the lon-
where:
gitudinal element divided by the distance from the center of
ρ = mass density (for example, units of g/mm ) of the wear
rotation to the insertion point of an anchor (for example: 0.78
material.
for a 35 mm active length, X=40mmand Y = 40/2 mm).
3.2.11 interval net wear rate—WR during cycle interval i 3.2.23 two percent (2 %) offset angular displacement
i
(degrees)—a permanent angular displacement in the X-Y plane
(mg/million cycles):
measured via the actuator equal to 0.020 times the torsional
NW 2 NW
~ !
i i21
WR 5 310 aspect ratio (for example: 0.9° for 0.78 × 0.02 × 180°/pi) (see
i
~# ofcyclesininterval i)
Point B in Fig. 1).
Note: for i=1, NW =0.
i–1
3.2.24 2 % offset displacement—a permanent deformation
3.2.12 kinematic profile—the relative motion between adja-
measuredviatheactuatorequalto0.020timestheactivelength
centvertebralbodiesthatthespinaldeviceissubjectedtowhile
ofthelongitudinalelement(forexample:1.04mmfora52mm
being tested (note that rigid devices may have minimal motion
active length) (see Distance OB in Fig. 1).
between vertebral bodies).
3.2.25 wear—the progressive loss of material from the
3.2.13 maximum run-out force or moment—the maximum
device(s)ordevicecomponentsasaresultofrelativemotionat
force or moment for a given test that can be applied to a single
the surface with another body as measured by the change in
level construct intended for fusion in which all of the tested
mass of the components of the implants. Or in the case of
constructs have withstood 5000000 cycles without functional
non-articulating, compliant components, wear is defined sim-
or mechanical failure. For non-fusion devices, the maximum
ply as the loss of material from the device. Note that bone
run-out force or moment is defined as 10000000 cycles
interface components of the device are excluded from this
without functional or mechanical failure.
definition. See 5.2.2, 5.2.4, and 5.2.5.
3.2.14 mechanical failure—failure associated with a defect
3.2.26 weight S of soak control specimen (g)—S initialand
i 0
in the material (for example, fatigue crack) or of the bonding
S at end of cycle interval i.
i
between materials that may or may not produce functional
3.2.27 weight W of wear specimen (g)—W initialand W at
i 0 i
failure.
end of cycle interval i.
3.2.15 net volumetric wear—NV of wear specimen (mm ):
i
3.2.28 ultimate displacement (mm or degrees)—the dis-
NW
placementassociatedwiththeultimateforce(displacementOF
i
NV 5
i
ρ
in Fig. 1).
at end of cycle interval i.
3.2.29 ultimate load (N or N-m)—the maximum applied
where: force, F, transmitted by the actuator that can be applied to the
spinal construct (Point E in Fig. 1).
ρ = mass density (for example, units of g/mm ) of the wear
material.
3.2.30 yield displacement—the displacement (mm or de-
grees) when a spinal construct has a permanent deformation
3.2.16 net wear—NW of wear specimen (g):
i
equal to the offset displacement (Distance OA in Fig. 1).
NW 5 ~W 2 W !1~S 2 S !
i 0 i i 0
3.2.31 yield force—the applied force, F, or moment trans-
Loss in weight of the wear specimen corrected for fluid ab-
mitted by the actuator required to produce a permanent
sorption at end of cycle interval i.
deformation equal to the offset displacement (Point D in Fig.
3.2.17 permanent deformation—the remaining displace-
1).
ment (mm) or angular rotation (degrees) relative to the initial
unloaded condition of the intervertebral body fusion device
4. Significance and Use
assembly after the applied force has been removed.
4.1 This test method is designed to quantify the static and
3.2.18 run-out (cycles)—the maximum number of cycles
dynamic characteristics of different designs of single level
thatatestneedstobecarriedtoiffunctionalfailurehasnotyet
spinal constructs. Wear may also be assessed for implants that
occurred.
allowmotionusingtestingmedium(see6.1)forsimulatingthe
3.2.19 single level spinal construct—a non-biologic physiologic environment at 37°C. Wear is assessed using a
structure, which lies entirely outside the intervertebral disc
weight loss method in addition to dimensional analyses.
space, intended to support the full or partial load between Weight loss is determined after subjecting the implants to
adjacent vertebral bodies. In this test method, this definition dynamicprofilesspecifiedinthistestmethod.Thisinformation
does not include facet arthroplasty devices. will allow the manufacturer or end user of the product to
F2624 − 12 (2020)
NOTE 1—This example depicts a 3D rendering of a possible method for implementing of the rotational testing apparatus. In this example, adjustment
mechanismsareemployedtoimpartbothaxialload(Fz)andaspondylolisthesisoffsetpriortolockingthespinalassemblyintheapparatus.Theactuator
isrotatedtoapplyflexion/extensionmoments.Spinalconstructsarealsotestedinlateralbendingandaxialtorsioninthissametestsetupwithappropriate
modifications.
FIG. 2 Rotational Testing Apparatus
understand how the specific device in question performs under 5.2.1 Test Chambers—In the case of a multi-specimen
the test conditions prescribed in this test method.
machine being used with testing medium, each chamber shall
be isolated to prevent cross-contamination of the test speci-
4.2 This test method is intended to be applicable for single
mens. The chamber shall be made entirely of non-corrosive
level extra-discal spinal constructs. Three different types of
components(suchasacrylicplasticorstainlesssteel)andshall
fixtures are specified for testing single level extra-discal spinal
be easy to remove from the machine for thorough cleaning
constructs See Fig. 2, Fig. 4, and Fig. 5. See also Table 1.
between tests.
4.3 Implants may be designed using a variety of materials
5.2.2 Forweartesting,thetestchamberalsomustisolatethe
(for example, ceramics, metals, polymers, or combinations
device/construct from wear centers created by the testing
thereof), and it is the goal of this test method to enable a
fixtures.
comparison of the static, dynamic, and wear properties gener-
5.2.3 The user must determine the appropriate degrees of
atedbythesedevices,regardlessofmaterialandtypeofdevice.
freedom for the device depending on its intended use (see
5. Apparatus
5.2.6).
5.2.4 Component Clamping/Fixturing—Since one of the
5.1 Implant Components—The device may comprise a va-
purposes may be to characterize the wear properties of the
riety of shapes and configurations. Some known forms include
spinal device, the method for mounting components in the test
screws which rigidly grip the vertebral bodies coupled with
flexible, ela
...
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