ASTM F2624-12(2016)

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.Figure  
Loading Mode  
Rotational  
Fig. 2  
Flexion  
Extension  
Lateral Bending  
Axial Rotation  
Fig. 2 and Fig. 6  
Offset Flexion and Offset Extension  
Shear  
Fig. 4  
Anterior/Posterior Shear  
Compression Bending  
Fig. 5  
Compression Bending  
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 bo...

General Information

• Status: Historical
• Publication Date: 30-Nov-2016
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.25 - Spinal Devices

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F2624 − 12 (Reapproved 2016)
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 test method 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 test method to establish
1.3 Thistestmethodisnotintendedtoaddressanypotential
appropriate safety and health practices and to determine the
failuremodeasitrelatestothefixationofthedevicetoitsbony
applicability of regulatory limitations prior to use.
interfaces.
1.4 It is the intent of this test method to enable single level
2. Referenced Documents
extra-discal spinal constructs with regard to kinematic,
2.1 ASTM Standards:
functional, and wear characteristics when tested under the
E2309Practices forVerification of Displacement Measuring
specified conditions.
Systems and Devices Used in Material Testing Machines
1.5 This test method is not intended to address facet
F561 Practice for Retrieval and Analysis of Medical
arthroplasty devices.
Devices, and Associated Tissues and Fluids
F1714GuideforGravimetricWearAssessmentofProsthetic
1.6 In order that the data be reproducible and comparable
Hip Designs in Simulator Devices
within and between laboratories, it is essential that uniform
F1717Test Methods for Spinal Implant Constructs in a
procedures be established. This test method is intended to
Vertebrectomy Model
facilitate uniform testing methods and data reporting.
F1877Practice for Characterization of Particles
1.7 The motion profiles specified by this test method do not
F2003Practice for Accelerated Aging of Ultra-High Mo-
necessarily accurately reproduce those occurring in vivo.
lecular Weight Polyethylene after Gamma Irradiation in
Rather this method provides useful boundary/endpoint condi-
Air
tions for evaluating implant designs in a functional manner.
F2423Guide for Functional, Kinematic, and Wear Assess-
1.8 This test method is not intended to be a performance
ment of Total Disc Prostheses
standard. It is the responsibility of the user of this test method
to characterize the safety and effectiveness of the device under 3. Terminology
evaluation.
3.1 All terminology is consistent with the referenced
1.9 Multiple test methods are included in this standard. standards, unless otherwise stated.
However, it must be noted that the user is not obligated to test
3.2 Definitions:
using all of the described methods. Instead, the user should
3.2.1 center of rotation (COR)—the point about which the
only select test methods that are appropriate for a particular
simulated vertebral bodies rotate in performing the range of
motion (ROM) specified in this test method.
ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedical
andSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommittee
F04.25 on Spinal Devices. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2016. Published December 2016. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2007. Last previous edition approved in 2012 as F2624–12. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F2624-12R16. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2624 − 12 (2016)
FIG. 1 Typical Force Displacement Curve
3.2.2 compressive bending stiffness (N/mm)—the compres- 3.2.5.2 X-Axis—the positive X-Axis is a global fixed axis
sive bending yield force divided by elastic displacement (see
relative to the testing machine’s stationary base and is to be
the initial slope of line BC in Fig. 1). directed anteriorly relative to the specimen’s initial unloaded
position.
3.2.3 compressive bending ultimate load (N)—the maxi-
mum compressive force in the X-Z plane applied to a spinal 3.2.5.3 Y-Axis—the positive Y-Axis is a global fixed axis
implant assembly (see the force at Point E in Fig. 1). The relative to the testing machine’s stationary base and is directed
ultimate load should be a function of the device and not of the
laterally relative to the specimen’s initial unloaded position.
load cell or testing machine.
3.2.5.4 Z-Axis—the positive Z-Axis is a global fixed axis
3.2.4 compressive bending yield load (N)—the compressive
relative to the testing machine’s stationary base and is to be
bending force in the X-Z plane necessary to produce a directed superiorly relative to the specimen’s initial unloaded
permanent deformation equal to 0.020 times the active length
position.
of the longitudinal element (see the force at Point D in Fig. 1).
3.2.6 degradation—loss of material or function or material
3.2.5 coordinate system/axes—three orthogonal axes are
properties due to causes other than that associated with wear.
defined following a right-handed Cartesian coordinate system.
3.2.7 elastic displacement (mm or degrees)—the displace-
The XY plane is to bisect the sagittal plane between superior
ment at 2% offset yield (see PointAin Fig. 1) minus the 2%
and inferior surfaces that are intended to simulate the adjacent
offset displacement (see Point B in Fig. 1). (The distance
vertebral end plates. The positive Z axis is to be directed
between Point A and Point B in Fig. 1.)
superiorly.Forcecomponentsparalleltothe XYplaneareshear
components of loading.The compressive axial force is defined 3.2.8 fluid absorption—fluid absorbed by the device mate-
rial during testing or while implanted in vivo.
to be the component in the negative Z direction.Torsional load
is defined to be the component of moment about the Z-axis.
3.2.9 functional failure—permanent deformation or wear
that renders the implant assembly ineffective or unable to
3.2.5.1 origin—the center of the coordinate system is lo-
cated at the center of rotation of the testing fixture. adequately resist load/motion or any secondary effects that
F2624 − 12 (2016)
result in a reduction of clinically relevant motions or the 3.2.20 stiffness (N/mm or N-m/degree)—(The Slope of Line
motions intended by the design of the device. OG—Fig. 1)—the slope of the initial linear portion of the
force-displacement or moment-degree curve.
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—(Distance OB—Fig. 1)—a
3.2.12 kinematic profile—the relative motion between adja-
permanent deformation measured via the actuator equal to
centvertebralbodiesthatthespinaldeviceissubjectedtowhile
0.020 times the active length of the longitudinal element (for
being tested (note that rigid devices may have minimal motion
example: 1.04 mm for a 52 mm active length) (see Point B in
between vertebral bodies).
Fig. 1).
3.2.13 maximum run out force or moment—the maximum
3.2.25 wear—the progressive loss of material from the
force or moment for a given test that can be applied to a single
device(s)ordevicecomponentsasaresultofrelativemotionat
level construct intended for fusion in which all of the tested
the surface with another body as measured by the change in
constructs have withstood 5000000 cycles without functional
mass of the components of the implants. Or in the case of
or mechanical failure. For non-fusion devices, the maximum
non-articulating, compliant components, wear is defined sim-
run out force or moment is defined as 10000000 cycles
ply as the loss of material from the device. Note that bone
without functional or mechanical failure.
interface components of the device are excluded from this
3.2.14 mechanical failure—failure associated with a defect definition; see 5.2.2, 5.2.4, and 5.2.5.
in the material (for example, fatigue crack) or of the bonding
3.2.26 weight S of soak control specimen (g)—S initialand
i 0
between materials that may or may not produce functional
S at end of cycle interval i.
i
failure.
3.2.27 weight W of wear specimen (g)—W initialand W at
i 0 i
3.2.15 net volumetric wear—NV of wear specimen (mm ):
end of cycle interval i.
i
NW
3.2.28 ultimate displacement (mm or degrees)—
i
NV 5
i
ρ
(DisplacementOF—Fig.1)—thedisplacementassociatedwith
at end of cycle interval i.
the ultimate force.
where: 3.2.29 ultimate load (N or N-m)—(Point E—Fig. 1)—the
maximumappliedforce, F,transmittedbytheactuatorthatcan
ρ = mass density (for example, units of g/mm ) of the wear
be applied to the spinal construct.
material.
3.2.30 yield displacement—(Distance OA—Fig. 1)—the
3.2.16 net wear—NW of wear specimen (g):
i
displacement (mm or degrees) when a spinal construct has a
NW 5 ~W 2 W !1~S 2 S !
i 0 i i 0
permanent deformation equal to the offset displacement.
Loss in weight of the wear specimen corrected for fluid ab-
3.2.31 yield force—(PointD—Fig.1)—theappliedforce, F,
sorption at end of cycle interval i.
or moment transmitted by the actuator required to produce a
3.2.17 permanent deformation—the remaining displace-
permanent deformation equal to the offset displacement.
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 (2016)
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, such as acrylic plastic or stainless steel, and shall
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 purchase the vertebral bodies coupled
with flexible, elastic members; other forms may include rigid chamber shall not compromise the accuracy of assessment of
members coupled in a constrained (for example, pedicle the weight loss or stiffness variation during the test. For
screws) or semi-constrained manner (for example, screws and example, implants having complicated surfaces for contacting
rods connected with a universal joint with defined motion bone (for example, sintered beads, hydroxylapatite (HA)
limitati
...

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: F2624 − 12 F2624 − 12 (Reapproved 2016)
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. 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 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 must be noted that the user is not obligated to test using
all of the described methods. Instead, the user should only select test methods that are appropriate for a particular device design.
In most instances, only a subset of the herein described test methods will be required.
1.10 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. No other units of measurement are included in this standard.
1.11 This test method 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 test method to establish appropriate safety and health practices and to determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
E2309 Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines
F561 Practice for Retrieval and Analysis of Medical Devices, and Associated Tissues and Fluids
F1714 Guide for Gravimetric Wear Assessment of Prosthetic Hip Designs in Simulator Devices
F1717 Test Methods for Spinal Implant Constructs in a Vertebrectomy Model
F1877 Practice for Characterization of Particles
F2003 Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in Air
F2423 Guide for Functional, Kinematic, and Wear Assessment of Total Disc Prostheses
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
F04.25 on Spinal Devices.
Current edition approved Dec. 1, 2012Dec. 1, 2016. Published February 2013December 2016. Originally approved in 2007. Last previous edition approved in 20072012
as F1587 – 07.F2624 – 12. DOI: 10.1520/F2624-12.10.1520/F2624-12R16.
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’sstandard’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
F2624 − 12 (2016)
3. Terminology
3.1 All terminology is consistent with the referenced standards, unless otherwise stated.
3.2 Definitions:
3.2.1 center of rotation (COR)—the point about which the simulated vertebral bodies rotate in performing the range of motion
(ROM) specified in this test method.
3.2.2 compressive bending stiffness (N/mm)—the compressive bending yield force divided by elastic displacement (see the
initial slope of line BC in Fig. 1).
3.2.3 compressive bending ultimate load (N)—the maximum compressive force in the X-Z plane applied to a spinal implant
assembly (see the force at Point E in Fig. 1). The ultimate load should be a function of the device and not of the load cell or testing
machine.
3.2.4 compressive bending yield load (N)—the compressive bending force in the X-Z plane necessary to produce a permanent
deformation equal to 0.020 times the active length of the longitudinal element (see the force at Point D in Fig. 1).
3.2.5 coordinate system/axes—three orthogonal axes are defined following a right-handed Cartesian coordinate system. The XY
plane is to bisect the sagittal plane between superior and inferior surfaces that are intended to simulate the adjacent vertebral end
plates. The positive Z axis is to be directed superiorly. Force components parallel to the XY plane are shear components of loading.
The compressive axial force is defined to be the component in the negative Z direction. Torsional load is defined to be the
component of moment about the Z-axis.
3.2.5.1 origin—the center of the coordinate system is located at the center of rotation of the testing fixture.
3.2.5.2 X-Axis—the positive X-Axis is a global fixed axis relative to the testing machine’s stationary base and is to be directed
anteriorly relative to the specimen’s initial unloaded position.
3.2.5.3 Y-Axis—the positive Y-Axis is a global fixed axis relative to the testing machine’s stationary base and is directed laterally
relative to the specimen’s initial unloaded position.
3.2.5.4 Z-Axis—the positive Z-Axis is a global fixed axis relative to the testing machine’s stationary base and is to be directed
superiorly relative to the specimen’s initial unloaded position.
FIG. 1 Typical Force Displacement Curve
F2624 − 12 (2016)
3.2.6 degradation—loss of material or function or material properties due to causes other than that associated with wear.
3.2.7 elastic displacement (mm or degrees)—the displacement at 2 % offset yield (see Point A in Fig. 1) minus the 2 % offset
displacement (see Point B in Fig. 1). (The distance between Point A and Point B in Fig. 1.)
3.2.8 fluid absorption—fluid absorbed by the device material during testing or while implanted in vivo.
3.2.9 functional failure—permanent deformation or wear that renders the implant assembly ineffective or unable to adequately
resist load/motion or any secondary effects that result in a reduction of clinically relevant motions or the motions intended by the
design of the device.
3.2.10 interval net volumetric wear rate—VR during cycle interval i (mm /million cycles):
i
WR
i
VR 5
i
ρ
where:
ρ = mass density (for example, units of g/mm ) of the wear material.
3.2.11 interval net wear rate—WR during cycle interval i (mg/million cycles):
i
~NW 2 NW !
i i21
WR 5 310
i
~# of cycles in interval i)
Note: for i = 1, NW = 0.
i–1
3.2.12 kinematic profile—the relative motion between adjacent vertebral bodies that the spinal device is subjected to while being
tested (note that rigid devices may have minimal motion between vertebral bodies).
3.2.13 maximum run out force or moment—the maximum force or moment for a given test that can be applied to a single level
construct intended for fusion in which all of the tested constructs have withstood 5 000 000 cycles without functional or
mechanical failure. For non-fusion devices, the maximum run out force or moment is defined as 10 000 000 cycles without
functional or mechanical failure.
3.2.14 mechanical failure—failure associated with a defect in the material (for example, fatigue crack) or of the bonding
between materials that may or may not produce functional failure.
3.2.15 net volumetric wear—NV of wear specimen (mm ):
i
NW
i
NV 5
i
ρ
at end of cycle interval i.
where:
ρ = mass density (for example, units of g/mm ) of the wear material.
3.2.16 net wear—NW of wear specimen (g)(g)::
i
NW 5 W 2 W 1 S 2 S
~ ! ~ !
i 0 i i 0
Loss in weight of the wear specimen corrected for fluid absorption at end of cycle interval i.
3.2.17 permanent deformation—the remaining displacement (mm) or angular rotation (degrees) relative to the initial unloaded
condition of the intervertebral body fusion device assembly after the applied force has been removed.
3.2.18 run-out (cycles)—the maximum number of cycles that a test needs to be carried to if functional failure has not yet
occurred.
3.2.19 single level spinal construct—a non-biologic structure, which lies entirely outside the intervertebral disc space, intended
to support the full or partial load between adjacent vertebral bodies. In this test method, this definition does not include facet
arthroplasty devices.
3.2.20 stiffness (N/mm or N-m/degree)—(The Slope of Line OG—Fig. 1)—the slope of the initial linear portion of the
force-displacement or moment-degree curve.
3.2.21 test block—the component of the test apparatus for mounting a single level spinal construct for the intended test
configuration (Fig. 3).
3.2.22 torsional aspect ratio—the active length of the longitudinal element divided by the distance from the center of rotation
to the insertion point of an anchor (for example: 0.78 for a 35 mm active length, X = 40 mm and Y = 40/2 mm).
3.2.23 two percent (2 %) offset angular displacement (degrees)—a permanent angular displacement in the X-Y plane measured
via the actuator equal to 0.020 times the torsional aspect ratio (for example: 0.9° for 0.78 × 0.02 × 180°/pi) (see Point B in Fig.
1).
3.2.24 2 % offset displacement—(Distance OB—Fig. 1)—a permanent deformation measured via the actuator equal to 0.020
times the active length of the longitudinal element (for example: 1.04 mm for a 52 mm active length) (see Point B in Fig. 1).
F2624 − 12 (2016)
NOTE 1—This example depicts a 3D rendering of a possible method for implementing of the rotational testing apparatus. In this example, adjustment
mechanisms are employed to impart both axial load (Fz) and a spondylolisthesis offset prior to locking the spinal assembly in the apparatus. The actuator
is rotated to apply flexion/extension moments. Spinal constructs are also tested in lateral bending and axial torsion in this same test setup with appropriate
modifications.
FIG. 2 Rotational Testing Apparatus
3.2.25 wear—the progressive loss of material from the device(s) or device components as a result of relative motion at the
surface with another body as measured by the change in mass of the components of the implants. Or in the case of non-articulating,
compliant components, wear is defined simply as the loss of material from the device. Note that bone interface components of the
device are excluded from this definition; see 5.2.2, 5.2.4, and 5.2.5.
3.2.26 weight S of soak control specimen (g)—S initial and S at end of cycle interval i.
i 0 i
3.2.27 weight W of wear specimen (g)—W initial and W at end of cycle interval i.
i 0 i
3.2.28 ultimate displacement (mm or degrees)—(Displacement OF—Fig. 1)—the displacement associated with the ultimate
force.
3.2.29 ultimate load (N or N-m)—(Point E—Fig. 1)—the maximum applied force, F, transmitted by the actuator that can be
applied to the spinal construct.
3.2.30 yield displacement—(Distance OA—Fig. 1)—the displacement (mm or degrees) when a spinal construct has a permanent
deformation equal to the offset displacement.
3.2.31 yield force—(Point D—Fig. 1)—the applied force, F, or moment transmitted by the actuator required to produce a
permanent deformation equal to the offset displacement.
4. 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.
F2624 − 12 (2016)
NOTE 1—All dimensions are in mm.
FIG. 3 Simulated Vertebral Body Testing Block
FIG. 4 Schematic of Anterior/Posterior Shear Testing Apparatus
F2624 − 12 (2016)
FIG. 5 Schematic of Single Level Compression Bending Test
TABLE 1 Loading Modes and Associated Apparatus Listing
Possible Tests That May Be Conducted (see 1.9)
NOTE 1—For all loading modes, static, dynamic, and wear tests are
described in this test method.
NOTE 2—“Offset” refers to 8 mm of offset induced in the spinal
construct (see Fig. 6) before subjecting the construct to rotational
flexion/extension moments (see Fig. 2).
Associated Associated
Loading Mode
Apparatus Figure
Rotational Fig. 2 Flexion
Extension
Lateral Bending
Axial Rotation
Fig. 2 and Fig. 6 Offset Flexion and Off-
set Extension
Shear Fig. 4 Anterior/Posterior
Shear
Compression Fig. 5 Compression Bending
Bending
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, dy
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