ASTM F2790-10(2014)
(Practice)Standard Practice for Static and Dynamic Characterization of Motion Preserving Lumbar Total Facet Prostheses
Standard Practice for Static and Dynamic Characterization of Motion Preserving Lumbar Total Facet Prostheses
SIGNIFICANCE AND USE
5.1 Facet Prosthesis Components—The facet replacement may comprise a variety of shapes and configurations. Its forms may include, but are not limited to, ball and socket articulating joints, joints having a free-floating or semi-constrained third body, metallic load-bearing surfaces, and spring and dampening mechanisms. Additionally, it may be a unilateral or bilateral design.
5.2 These test methods are designed to quantify the static and dynamic characteristics of different designs of FP. The tests are conducted in vitro in order to allow for analysis of individual devices and comparison of the mechanical performance of multiple designs.
5.3 The loads applied to the FP may differ from the complex loading seen in vivo, and therefore, the results from these tests may not directly predict in vivo performance. The results, however, can be used to compare mechanical performance in different devices.
5.4 Fatigue testing in a simulated body fluid or saline may cause fretting, corrosion, or lubricate the interconnections and thereby affect the relative performance of tested devices. This test should be conducted in a 0.9 % saline environmental bath at 37°C at a maximum rate of 10 Hz for all metallic devices and 2 Hz for non-metallic devices. Other test environments such as a simulated body fluid, a saline drip or mist, distilled water, other type of lubrication or dry could also be used with adequate justification. Likewise, alternative test frequencies may be used with adequate justification to ensure that it does not impact the device performance.
5.5 It is well known that the failure of materials is dependent upon stress, test frequency, surface treatments, and environmental factors. Therefore, when determining the effect of changing these parameters (for example, frequency, material, or environment), care should be taken to allow for appropriate interpretation of the results. In particular, it may be necessary to assess the influence of test frequency on de...
SCOPE
1.1 This practice provides guidance for the static and dynamic testing of Lumbar Total Facet Prostheses (FP). These implants are intended to allow motion and lend support to one or more functional spinal unit(s) through replacement of the natural facets.
1.2 These test methods are intended to provide a basis for the mechanical comparison among past, present, and future non-biologic FP. These test methods allow comparison of devices with different methods of application to the lumbar spine. These test methods are intended to enable the user to mechanically compare devices and do not purport to provide performance standards for them.
1.3 These test methods describe static and dynamic tests by specifying load types and specific methods of applying these loads.
1.4 These test methods do not purport to address all clinically relevant failure modes for FP, some of which will be device specific. For example, these test methods do not address implant wear resistance under expected in vivo loads and motions. In addition, the biologic response to wear debris is not addressed in these test methods.
1.5 Requirements are established for measuring displacements and evaluating the stiffness of FP.
1.6 Some devices may not be testable in all test configurations.
1.7 The values stated in SI units are to be regarded as the standard with the exception of angular measurements, which may be reported in terms of either degrees or radians.
1.8 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
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Designation: F2790 − 10 (Reapproved 2014)
Standard Practice for
Static and Dynamic Characterization of Motion Preserving
Lumbar Total Facet Prostheses
This standard is issued under the fixed designation F2790; 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 2. Referenced Documents
1.1 This practice provides guidance for the static and 2.1 ASTM Standards:
dynamic testing of Lumbar Total Facet Prostheses (FP). These D638 Test Method for Tensile Properties of Plastics
implants are intended to allow motion and lend support to one E4 Practices for Force Verification of Testing Machines
or more functional spinal unit(s) through replacement of the E6 Terminology Relating to Methods of Mechanical Testing
natural facets. E468 Practice for Presentation of Constant Amplitude Fa-
tigue Test Results for Metallic Materials
1.2 These test methods are intended to provide a basis for
E739 PracticeforStatisticalAnalysisofLinearorLinearized
the mechanical comparison among past, present, and future
Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
non-biologic FP. These test methods allow comparison of
F1582 Terminology Relating to Spinal Implants
devices with different methods of application to the lumbar
spine. These test methods are intended to enable the user to
3. Terminology
mechanically compare devices and do not purport to provide
3.1 All functional and kinematic testing terminology is
performance standards for them.
consistent with the referenced standards (including Teminol-
1.3 These test methods describe static and dynamic tests by
ogy E6 and Terminology F1582), unless otherwise stated.
specifying load types and specific methods of applying these
3.2 Definitions:
loads.
3.2.1 coordinate systems/axes—Global XYZorthogonalaxes
1.4 These test methods do not purport to address all clini-
are defined following a right-handed Cartesian coordinate
cally relevant failure modes for FP, some of which will be
system in which the XY plane is parallel to and co-planar with
devicespecific.Forexample,thesetestmethodsdonotaddress
the superior endplate of the inferior vertebral body.Alternative
implant wear resistance under expected in vivo loads and
coordinate systems may be used with justification. The global
motions.Inaddition,thebiologicresponsetoweardebrisisnot
axes are fixed relative to the inferior vertebral body. Lower
addressed in these test methods.
case letters, xyz, denote a local moving orthogonal coordinate
1.5 Requirements are established for measuring displace-
system attached to the superior vertebral body with directions
ments and evaluating the stiffness of FP.
initially coincident with those of the global XYZ axes, respec-
tively. The 3D motion of the superior relative to inferior
1.6 Some devices may not be testable in all test configura-
vertebra is specified and is to be measured in terms of
tions.
sequential Eulerian angular rotations about the xyz axes,
1.7 The values stated in SI units are to be regarded as the
respectively (z axial rotation, x lateral bend, and y flexion-
standard with the exception of angular measurements, which
extension).
may be reported in terms of either degrees or radians.
3.2.1.1 origin—center of the global coordinate system that
1.8 The values stated in inch-pound units are to be regarded
is located at the posterior medial position on the superior
as standard. The values given in parentheses are mathematical
endplate of the inferior vertebral body.
conversions to SI units that are provided for information only
3.2.1.2 X-axis—positive X-axis is to be directed anteriorly
and are not considered standard.
relative to the specimen’s initial unloaded position.
3.2.1.3 Y-axis—positive Y-axis is directed laterally (toward
the left) relative to the specimen’s initial unloaded position.
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.25 on Spinal Devices. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2014. Published November 2014. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2010. Last previous edition approved in 2010 as F2790-2010. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F2790–10R14. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2790 − 10 (2014)
3.2.1.4 Z-axis—positive Z-axis is to be directed superiorly 3.2.7 maximum run-out load or moment—the maximum
relative to the specimen’s initial unloaded position. load or moment for a given test that can be applied to a FP
3.2.2 failure—functional failure or substantial mechanical where all of the tested constructs have withstood 10 000 000
failure. cycles without failure.
3.2.2.1 functional failure—permanent deformation resulting
3.2.8 mechanical deterioration—deterioration that is visible
from fracture, plastic deformation, or loosening beyond the
to the naked eye and is associated with mechanical damage to
ultimate displacement or loosening that renders the spinal
thedeviceundertest(forexample,initiationoffatiguecrackor
implant assembly ineffective or unable to adequately resist
surface wear).
load.
3.2.9 permanent deformation—the remaining linear or an-
3.2.2.2 mechanical failure—failure associated with a defect
gular displacement (axial—mm, angular—degrees or radians)
in the material (for example, fatigue crack) or of the bonding
relative to the initial unloaded condition of the FP after the
between materials that may or may not produce functional
applied load or moment has been removed.
failure.
3.2.10 radius of rotation—the distance between the center
3.2.3 fatigue life—the number of cycles, N, that the FP can
of rotation and the functional position (for example, load-
sustain at a particular load or moment before failure occurs.
bearing contact point) of the FP, for a given motion (that is,
3.2.4 intended method of application—a FP may contain
flexion/extension, lateral bending, or axial rotation).
different types of features to stabilize the implant-tissue inter-
3.2.11 spinal implant assembly—a complete spinal implant
face such as threads, spikes, and textured surfaces. Each type
configuration as intended for surgical use. A spinal implant
of feature has an intended method of application or attachment
assembly may contain anchors, interconnections, and longitu-
to the spine.
dinal elements and may contain transverse elements.
3.2.5 insertion point of an anchor—the location where the
3.2.12 stiffness (axial—N/mm, angular—N·mm/degree or
anchor is attached to the test block.The insertion points shown
N·mm/radian)—the slope of the initial linear portion of the
inFig.1aretobeadheredtoifpossible.Insituationswherethe
load-displacement curve or the slope of the initial linear
design of the spinal implant assembly or the manufacturer’s
portion of the moment-angular displacement curve. This is
surgical instructions for installation dictate otherwise, the
illustratedastheslopeoftheline OGinFig.2.Thedevicemay
attachment points may deviate from these dimensions.
not exhibit an isolated linear portion on the load/displacement
3.2.6 longitudinal direction—the initial spatial orientation
curve, due to the complicated nature of these devices.As such,
between the insertion points in the superior test blocks and the
these data are information only.
inferior test blocks.
FIG. 1 UHMWPE Test Block FIG. 2 Typical Load Displacement Curve
F2790 − 10 (2014)
3.2.13 superior/inferior spinal implant construct—the supe- 4.2 All tests are to be performed on the prosthesis size with
rior or inferior spinal implant assembly attached to the test the smallest safety factor for the levels indicated for implan-
block. tation. If this worst-case size cannot be determined using
theoretical or experimental methods such as simple stress
3.2.14 test block—the component of the test apparatus for
calculations or finite element analysis, then all available sizes
mounting the FP in the intended test configuration.
or a justified selection are to be tested and the complete range
3.2.15 tightening torque—the specified torque that is ap-
of results are to be reported.
plied to the various fasteners of the spinal implant assembly.
4.3 Static and dynamic testing of the devices will simulate a
3.2.16 torsional ultimate load (N·m)—the maximum torque
motion segment via a gap between two Ultra High Molecular
applied to a spinal implant assembly (the torque at Point E in
Weight Polyethylene (UHMWPE) test blocks (Fig. 1, Fig. 3,or
Fig. 2). The ultimate torque should be a function of the device
Fig. 4). The UHMWPE used to manufacture the test blocks
and not of the load cell or testing machine.
should have a tensile breaking strength equal to 40 6 3 MPa
3.2.17 total facet prosthesis—nonbiologic structure in-
(see Specification D638). The UHMWPE will eliminate the
tended to restore the support and motion of the vertebral facet
effectsofthevariabilityofbonepropertiesandmorphologyfor
joint.
the fatigue tests.
3.2.18 ultimate displacement (axial—mm, angular—
4.4 Static and dynamic tests will evaluate the devices. The
degrees or radians)—the linear or angular displacement asso-
user of this practice must decide which series of tests are
ciated with the ultimate load or ultimate moment. This is
applicable to the device in question. The user of this practice
illustrated as the displacement, OF,in Fig. 2.
may choose to use all or a selection of the tests described for
3.2.19 ultimate load or moment (axial—N, angular—N·mm)
testing a particular device.
—the maximum applied load, F, or moment, M, transmitted to
4.5 This practice is intended to be applicable to FP that
the FP. This is illustrated as point E in Fig. 2.
support and transmit motion by means of an articulating joint
3.2.20 zero displacement intercept (mm)—the intersection
or by use of compliant materials and/or design. Ceramics,
of the straight line section of the load displacement curve and
metals, and/or polymers may be used in FPdesign, and it is the
zero load axis (the zero displacement reference Point O in Fig.
goal of this practice to enable a comparison of these devices,
2).
regardless of material and type of device.
4. Summary of Practice
5. Significance and Use
4.1 This practice is proposed for the mechanical testing of 5.1 Facet Prosthesis Components—The facet replacement
FP. may comprise a variety of shapes and configurations. Its forms
NOTE 1—(A) Anterior-Posterior, (B) Superior-Inferior, (C) Medial-Lateral setups are shown. These setups require one translational actuator and may
require specific fixturing. Test blocks are shown in grey. The arrow indicates the loading direction.
FIG. 3 Diagrams of Possible Test Setups for Translational Loading of a FP
F2790 − 10 (2014)
NOTE 1—(A) Simulated Flexion-Extension, (B)Axial Rotation, (C) Lateral Bending setups are shown.These setups require one rotational actuator and
may require specific fixturing. The arrow indicates the rotation direction. Test blocks are shown in grey. The position of the axis of rotation should be
based on the information in Table X1.1.
FIG. 4 Diagrams of Possible Test Setups for Rotational Loading of a FP
may include, but are not limited to, ball and socket articulating or environment), care should be taken to allow for appropriate
joints, joints having a free-floating or semi-constrained third interpretation of the results. In particular, it may be necessary
body, metallic load-bearing surfaces, and spring and dampen- to assess the influence of test frequency on device fracture
ingmechanisms.Additionally,itmaybeaunilateralorbilateral while holding the test environment, implant materials and
design. processing, and implant geometry constant.
5.2 These test methods are designed to quantify the static
6. Apparatus and Setup
anddynamiccharacteristicsofdifferentdesignsofFP.Thetests
are conducted in vitro in order to allow for analysis of
6.1 Test machines will conform to the requirements of
individual devices and comparison of the mechanical perfor-
Practices E4.
mance of multiple designs.
6.2 The test apparatus will allow multiple loading regimes
5.3 TheloadsappliedtotheFPmaydifferfromthecomplex
to be applied to all forms of FP.
loading seen in vivo, and therefore, the results from these tests
6.3 The test block should be created according to Fig. 1.
may not directly predict in vivo performance. The results,
Variations from this design to accommodate a device’s fixation
however, can be used to compare mechanical performance in
method or features should be reported and justified.
different devices.
6.4 The interpedicular spacing (superior-to-inferior center-
5.4 Fatigue testing in a simulated body fluid or saline may
to-center distance between bone anchors) shall be set at 38 mm
cause fretting, corrosion, or lubricate the interconnections and
when installing the device and at the beginning of each test.
thereby affect the relative performance of tested devices. This
The implants should be placed in the UHMWPE blocks
test should be conducted in a 0.9 % saline environmental bath
according to the recommended surgical technique. For devices
at37°Catamaximumrateof10Hzforallmetallicdevicesand
that do not require pedicular fixation appropriate test blocks
2 Hz for non-metallic devices. Other test environments such as
should be manufactured to ensure proper evaluation of the
a simulated body fluid, a saline drip or mist, distilled water,
fixation components.
other type of lubrication or dry could also be used with
adequate justification. Likewise, alternative test frequencies
6.5 Install the FP in the UHMWPE blocks according to the
may be used with adequate justification to ensure that it does
manufacturer’s instructions. If necessary, utilize an aluminum
not impact the device performance.
spacer block between the superior and inferior UHMWPE
5.5 It is well known that the failure of materials is depen- blocks to fix them with respect to each other during installation
dent upon stress, test frequency, surface treatments, and envi- and remove after installation is complete. The spacer block
ronmental factors. Therefore, when determining the effect of should ensure that the device is installed with the proper active
changing these parameters (for example, frequency,
...
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: F2790 − 10 F2790 − 10 (Reapproved 2014)
Standard Practice for
Static and Dynamic Characterization of Motion Preserving
Lumbar Total Facet Prostheses
This standard is issued under the fixed designation F2790; 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 practice provides guidance for the static and dynamic testing of Lumbar Total Facet Prostheses (FP). These implants
are intended to allow motion and lend support to one or more functional spinal unit(s) through replacement of the natural facets.
1.2 These test methods are intended to provide a basis for the mechanical comparison among past, present, and future
non-biologic FP. These test methods allow comparison of devices with different methods of application to the lumbar spine. These
test methods are intended to enable the user to mechanically compare devices and do not purport to provide performance standards
for them.
1.3 These test methods describe static and dynamic tests by specifying load types and specific methods of applying these loads.
1.4 These test methods do not purport to address all clinically relevant failure modes for FP, some of which will be device
specific. For example, these test methods do not address implant wear resistance under expected in vivo loads and motions. In
addition, the biologic response to wear debris is not addressed in these test methods.
1.5 Requirements are established for measuring displacements and evaluating the stiffness of FP.
1.6 Some devices may not be testable in all test configurations.
1.7 The values stated in SI units are to be regarded as the standard with the exception of angular measurements, which may be
reported in terms of either degrees or radians.
1.8 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
2. Referenced Documents
2.1 ASTM Standards:
D638 Test Method for Tensile Properties of Plastics
E4 Practices for Force Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E468 Practice for Presentation of Constant Amplitude Fatigue Test Results for Metallic Materials
E739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
F1582 Terminology Relating to Spinal Implants
3. Terminology
3.1 All functional and kinematic testing terminology is consistent with the referenced standards (including Teminology E6 and
Terminology F1582), unless otherwise stated.
3.2 Definitions:
3.2.1 coordinate systems/axes—Global XYZ orthogonal axes are defined following a right-handed Cartesian coordinate system
in which the XY plane is parallel to and co-planar with the superior endplate of the inferior vertebral body. Alternative coordinate
systems may be used with justification. The global axes are fixed relative to the inferior vertebral body. Lower case letters, xyz,
This practice 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 Jan. 1, 2010Nov. 1, 2014. Published February 2010November 2014. Originally approved in 2010. Last previous edition approved in 2010 as
F2790-2010. DOI: 10.1520/F2790–10.10.1520/F2790–10R14.
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
F2790 − 10 (2014)
denote a local moving orthogonal coordinate system attached to the superior vertebral body with directions initially coincident with
those of the global XYZ axes, respectively. The 3D motion of the superior relative to inferior vertebra is specified and is to be
measured in terms of sequential Eulerian angular rotations about the xyz axes, respectively (z axial rotation, x lateral bend, and y
flexion-extension).
3.2.1.1 origin—center of the global coordinate system that is located at the posterior medial position on the superior endplate
of the inferior vertebral body.
3.2.1.2 X-axis—positive X-axis is to be directed anteriorly relative to the specimen’s initial unloaded position.
3.2.1.3 Y-axis—positive Y-axis is directed laterally (toward the left) relative to the specimen’s initial unloaded position.
3.2.1.4 Z-axis—positive Z-axis is to be directed superiorly relative to the specimen’s initial unloaded position.
3.2.2 failure—functional failure or substantial mechanical failure.
3.2.2.1 functional failure—permanent deformation resulting from fracture, plastic deformation, or loosening beyond the
ultimate displacement or loosening that renders the spinal implant assembly ineffective or unable to adequately resist load.
3.2.2.2 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.
3.2.3 fatigue life—the number of cycles, N, that the FP can sustain at a particular load or moment before failure occurs.
3.2.4 intended method of application—a FP may contain different types of features to stabilize the implant-tissue interface such
as threads, spikes, and textured surfaces. Each type of feature has an intended method of application or attachment to the spine.
3.2.5 insertion point of an anchor—the location where the anchor is attached to the test block. The insertion points shown in
Fig. 1 are to be adhered to if possible. In situations where the design of the spinal implant assembly or the manufacturer’s surgical
instructions for installation dictate otherwise, the attachment points may deviate from these dimensions.
3.2.6 longitudinal direction—the initial spatial orientation between the insertion points in the superior test blocks and the
inferior test blocks.
3.2.7 maximum run-out load or moment—the maximum load or moment for a given test that can be applied to a FP where all
of the tested constructs have withstood 10 000 000 cycles without failure.
3.2.8 mechanical deterioration—deterioration that is visible to the naked eye and is associated with mechanical damage to the
device under test (for example, initiation of fatigue crack or surface wear).
3.2.9 permanent deformation—the remaining linear or angular displacement (axial—mm, angular—degrees or radians) relative
to the initial unloaded condition of the FP after the applied load or moment has been removed.
FIG. 1 UHMWPE Test Block
F2790 − 10 (2014)
3.2.10 radius of rotation—the distance between the center of rotation and the functional position (for example, load-bearing
contact point) of the FP, for a given motion (that is, flexion/extension, lateral bending, or axial rotation).
3.2.11 spinal implant assembly—a complete spinal implant configuration as intended for surgical use. A spinal implant assembly
may contain anchors, interconnections, and longitudinal elements and may contain transverse elements.
3.2.12 stiffness (axial—N/mm, angular—N·mm/degree or N·mm/radian)—the slope of the initial linear portion of the
load-displacement curve or the slope of the initial linear portion of the moment-angular displacement curve. This is illustrated as
the slope of the line OG in Fig. 2. The device may not exhibit an isolated linear portion on the load/displacement curve, due to
the complicated nature of these devices. As such, these data are information only.
3.2.13 superior/inferior spinal implant construct—the superior or inferior spinal implant assembly attached to the test block.
3.2.14 test block—the component of the test apparatus for mounting the FP in the intended test configuration.
3.2.15 tightening torque—the specified torque that is applied to the various fasteners of the spinal implant assembly.
3.2.16 torsional ultimate load (N·m)—the maximum torque applied to a spinal implant assembly (the torque at Point E in Fig.
2). The ultimate torque should be a function of the device and not of the load cell or testing machine.
3.2.17 total facet prosthesis—nonbiologic structure intended to restore the support and motion of the vertebral facet joint.
3.2.18 ultimate displacement (axial—mm, angular—degrees or radians)—the linear or angular displacement associated with the
ultimate load or ultimate moment. This is illustrated as the displacement, OF, in Fig. 2.
3.2.19 ultimate load or moment (axial—N, angular—N·mm) —the maximum applied load, F, or moment, M, transmitted to the
FP. This is illustrated as point E in Fig. 2.
3.2.20 zero displacement intercept (mm)—the intersection of the straight line section of the load displacement curve and zero
load axis (the zero displacement reference Point O in Fig. 2).
4. Summary of Practice
4.1 This practice is proposed for the mechanical testing of FP.
4.2 All tests are to be performed on the prosthesis size with the smallest safety factor for the levels indicated for implantation.
If this worst-case size cannot be determined using theoretical or experimental methods such as simple stress calculations or finite
element analysis, then all available sizes or a justified selection are to be tested and the complete range of results are to be reported.
FIG. 2 Typical Load Displacement Curve
F2790 − 10 (2014)
4.3 Static and dynamic testing of the devices will simulate a motion segment via a gap between two Ultra High Molecular
Weight Polyethylene (UHMWPE) test blocks (Fig. 1, Fig. 3, or Fig. 4). The UHMWPE used to manufacture the test blocks should
have a tensile breaking strength equal to 40 6 3 MPa (see Specification D638). The UHMWPE will eliminate the effects of the
variability of bone properties and morphology for the fatigue tests.
4.4 Static and dynamic tests will evaluate the devices. The user of this practice must decide which series of tests are applicable
to the device in question. The user of this practice may choose to use all or a selection of the tests described for testing a particular
device.
4.5 This practice is intended to be applicable to FP that support and transmit motion by means of an articulating joint or by use
of compliant materials and/or design. Ceramics, metals, and/or polymers may be used in FP design, and it is the goal of this practice
to enable a comparison of these devices, regardless of material and type of device.
5. Significance and Use
5.1 Facet Prosthesis Components—The facet replacement may comprise a variety of shapes and configurations. Its forms may
include, but are not limited to, ball and socket articulating joints, joints having a free-floating or semi-constrained third body,
metallic load-bearing surfaces, and spring and dampening mechanisms. Additionally, it may be a unilateral or bilateral design.
5.2 These test methods are designed to quantify the static and dynamic characteristics of different designs of FP. The tests are
conducted in vitro in order to allow for analysis of individual devices and comparison of the mechanical performance of multiple
designs.
5.3 The loads applied to the FP may differ from the complex loading seen in vivo, and therefore, the results from these tests
may not directly predict in vivo performance. The results, however, can be used to compare mechanical performance in different
devices.
5.4 Fatigue testing in a simulated body fluid or saline may cause fretting, corrosion, or lubricate the interconnections and thereby
affect the relative performance of tested devices. This test should be conducted in a 0.9 % saline environmental bath at 37°C at
a maximum rate of 10 Hz for all metallic devices and 2 Hz for non-metallic devices. Other test environments such as a simulated
body fluid, a saline drip or mist, distilled water, other type of lubrication or dry could also be used with adequate justification.
Likewise, alternative test frequencies may be used with adequate justification to ensure that it does not impact the device
performance.
5.5 It is well known that the failure of materials is dependent upon stress, test frequency, surface treatments, and environmental
factors. Therefore, when determining the effect of changing these parameters (for example, frequency, material, or environment),
NOTE 1—(A) Anterior-Posterior, (B) Superior-Inferior, (C) Medial-Lateral setups are shown. These setups require one translational actuator and may
require specific fixturing. Test blocks are shown in grey. The arrow indicates the loading direction.
FIG. 3 Diagrams of Possible Test Setups for Translational Loading of a FP
F2790 − 10 (2014)
NOTE 1—(A) Simulated Flexion-Extension, (B) Axial Rotation, (C) Lateral Bending setups are shown. These setups require one rotational actuator and
may require specific fixturing. The arrow indicates the rotation direction. Test blocks are shown in grey. The position of the axis of rotation should be
based on the information in Table X1.1.
FIG. 4 Diagrams of Possible Test Setups for Rotational Loading of a FP
care should be taken to allow for appropriate interpretation of the results. In particular, it may be necessary to assess the influence
of test frequency on device fracture while holding the test environment, implant materials and processing, and implant geometry
constant.
6. Apparatus and Setup
6.1 Test machines will conform to the requirements of Practices E4.
6.2 The test apparatus will allow multiple loading regimes to be applied to all forms of FP.
6.3 The test block should be created according to Fig. 1. Variations from this design to accommodate a device’s fixation method
or features should be reported and justified.
6.4 The interpedicular spacing (superior-to-inferior center-to-center distance between bone anchors) shall be set at 38 mm when
installing the device and at the beginning of each test. The implants should be placed in the UHMWPE blocks according to the
recommended surgical technique. For
...
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