ASTM F2694-07(2013)
(Practice)Standard Practice for Functional and Wear Evaluation of Motion-Preserving Lumbar Total Facet Prostheses
Standard Practice for Functional and Wear Evaluation of Motion-Preserving Lumbar Total Facet Prostheses
SIGNIFICANCE AND USE
5.1 Total Facet Prosthesis Components—The total 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 Spinal Testing Apparatus:
5.2.1 Test Chambers—In case of a multispecimen machine, each chamber shall be isolated to prevent cross-contamination of the test specimens. The chamber shall be made entirely of corrosion resistant materials, such as acrylic plastic or stainless steel, and shall be removable from the machine for thorough cleaning between tests.
5.2.2 Component Clamping/Fixturing—Since the purpose of the test is to characterize the wear and kinematic function of the total facet prosthesis, the method for mounting components in the test chamber shall not compromise the accuracy of assessment of the weight loss or stiffness variation during the test. For example, prostheses having complicated superior and inferior surfaces for contacting bone (for example, sintered beads, hydroxylapatite (HA) coating, plasma spray) may be specially manufactured to modify that surface in a manner that does not affect the wear simulation.
5.2.3 The device should be securely (rigidly) attached at its bone-implant interface to the mating test fixtures.
5.2.4 The motion of the superior test fixture (more posterior fixture in Figs. 1 and 2) relative to the inferior testing fixture shall be constrained in three-dimensional space except for the components in the direction of specified test motions/loads. Note 1—This setup would require two rotational actuators and one translational actuator.
FIG. 1 Diagrams of Possible Test Apparatus for Allowing Simultaneous Lateral Bending and Axial Rotation Motions with Anterior-Posterior Directed Facet LoadingNote 1—This setup would requ...
SCOPE
1.1 This practice provides guidance for the functional, kinematic and wear testing of motion-preserving total facet prostheses for the lumbar spine. These implants are intended to allow motion and lend support to the functional spinal unit(s) through replacement of the natural facets.
1.2 This test method is not intended to address the bone implant interface or the static characteristics of the prosthesis components. Fatigue characteristics are included, but only as a by-product of cyclic wear testing under facet load and thus are not addressed in the typical process of generating an S-N characterization.
1.3 Biocompatibility of the materials used in a total facet prosthesis are not addressed in this practice.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4.1 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.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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: F2694 − 07 (Reapproved 2013)
Standard Practice for
Functional and Wear Evaluation of Motion-Preserving
Lumbar Total Facet Prostheses
This standard is issued under the fixed designation F2694; 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 Used in Total Joint Prostheses
F1714 GuideforGravimetricWearAssessmentofProsthetic
1.1 This practice provides guidance for the functional,
Hip Designs in Simulator Devices
kinematic and wear testing of motion-preserving total facet
F1877 Practice for Characterization of Particles
prostheses for the lumbar spine.These implants are intended to
F2346 Test Methods for Static and Dynamic Characteriza-
allow motion and lend support to the functional spinal unit(s)
tion of Spinal Artificial Discs
through replacement of the natural facets.
1.2 This test method is not intended to address the bone 3. Terminology
implant interface or the static characteristics of the prosthesis
3.1 All functional and kinematic testing terminology is
components. Fatigue characteristics are included, but only as a
consistent with the referenced standards, unless otherwise
by-product of cyclic wear testing under facet load and thus are
stated.
not addressed in the typical process of generating an S-N
3.2 Definitions:
characterization.
3.2.1 coordinate systems/axes, n—global XYZ orthogonal
1.3 Biocompatibility of the materials used in a total facet
axes are defined following a right-handed Cartesian coordinate
prosthesis are not addressed in this practice.
system in which the XY plane is parallel to and co-planar with
the superior endplate of the inferior vertebral body. The global
1.4 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this axes are fixed relative to the inferior vertebral body, which in
this practice is also considered to be stationary with respect to
standard.
1.4.1 The values stated in SI units are to be regarded as the thetestmachine’sframe.Lowercaseletters, xyz,denotealocal
moving orthogonal coordinate system attached to the superior
standard with the exception of angular measurements, which
may be reported in either degrees or radians. vertebral body with directions initially coincident with those of
the global XYZ axes, respectively. The 3D motion of the
1.5 This standard does not purport to address all of the
superior relative to inferior vertebra is specified and is to be
safety concerns, if any, associated with its use. It is the
measured in terms of sequential Eulerian angular rotations
responsibility of the user of this standard to establish appro-
about the xyz axes, respectively (z axial rotation, x lateral bend,
priate safety and health practices and determine the applica-
and y flexion-extension).
bility of regulatory limitations prior to use.
3.2.1.1 origin, n—center of the global coordinate system
2. Referenced Documents
that is located at the posterior medial position on the superior
endplate of the inferior vertebral body.
2.1 ASTM Standards:
F561 Practice for Retrieval and Analysis of Medical 3.2.1.2 X-axis, n—positive X-axisistobedirectedanteriorly
Devices, and Associated Tissues and Fluids relative to the specimen’s initial unloaded position.
F732 Test Method for Wear Testing of Polymeric Materials
3.2.1.3 Y-axis, n—positive Y-axis is directed laterally (to-
ward the left) relative to the specimen’s initial unloaded
position.
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
3.2.1.4 Z-axis, n—positive Z-axis is to be directed superi-
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.25 on Spinal Devices. orly relative to the specimen’s initial unloaded position.
Current edition approved March 1, 2013. Published March 2013. Originally
3.2.2 fluid absorption, n—fluid absorbed by the device
approved in 2007. Last previous edition approved in 2007 as F2694—07. DOI:
material during testing or while implanted in vivo.
10.1520/F2694-07R13.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.2.3 functional failure, n—permanent deformation or wear
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
that renders the total facet prosthesis assembly ineffective or
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. unable to perform its intended function.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2694 − 07 (2013)
3.2.4 interval net volumetric wear rate VR during cycle 4. Summary of Practice
i
interval i (mm /million cycles), n—VR = WR/ρ; where ρ =
i i
4.1 This practice can be used to describe the function,
mass density (for example, units of g/mm ) of the wear
kinematics, and wear behavior of total facet prostheses sub-
material.
jected to cyclic loading/motion for relatively large numbers of
3.2.5 interval net wear rate WR during cycle interval i
cycles. (For example, various designs of total facet prostheses,
i
(g/million cycles), n—WR =((NW – NW )/(number of cycles
as well as the effects of materials, manufacturing techniques
i i i-1
in interval i))·10 ; for i=1, NW =0.
and other design variables on one particular design can be
i-1
studied using this practice.)
3.2.6 total facet prosthesis, n—nonbiologic structure in-
tended to restore the support and motion of the natural
4.2 This practice is intended to be applicable to total facet
vertebral facet joint.
prostheses that support and transmit motion by means of an
articulating joint or by use of compliant materials. Ceramics,
3.2.7 kinematics profile, n—relative motion between adja-
metals, and/or polymers may be used in total facet prosthesis
cent vertebral bodies that the total facet prosthesis is subjected
design, and it is the goal of this practice to enable a kinematic
to while being tested.
wear comparison of these devices, regardless of material and
3.2.8 load profile, n—loading that the device experiences
type of device.
while being tested under a defined kinematics profile or the
loading that the total facet prosthesis is subject to if tested in
5. Significance and Use
load control.
5.1 Total Facet Prosthesis Components—The total facet
3.2.9 radius of rotation, n—the distance between the center
replacement may comprise a variety of shapes and configura-
of rotation and the functional position (for example, load-
tions. Its forms may include, but are not limited to, ball and
bearing contact point) of the total facet prosthesis, for a given
socket articulating joints, joints having a free-floating or
motion (that is, flexion/extension, lateral bending, or axial
semi-constrained third body, metallic load-bearing surfaces,
rotation).
andspringanddampeningmechanisms.Additionally,itmaybe
3.2.10 mechanical failure, n—failure associated with a de-
a unilateral or bilateral design.
fect in the material (for example, fatigue crack) or of the
5.2 Spinal Testing Apparatus:
bonding between materials that may or may not produce
5.2.1 Test Chambers—In case of a multispecimen machine,
functional failure.
each chamber shall be isolated to prevent cross-contamination
3.2.11 weight S of soak control specimen (g), n—S initial
i 0
of the test specimens. The chamber shall be made entirely of
and S at end of cycle interval i.
i
corrosion resistant materials, such as acrylic plastic or stainless
steel, and shall be removable from the machine for thorough
3.2.12 weight W of wear specimen (g), n—W initial and W
i 0 i
at end of cycle interval i. cleaning between tests.
5.2.2 Component Clamping/Fixturing—Since the purpose
3.2.13 net wear NW of wear specimen (g), n—NW =(W –
i i 0
of the test is to characterize the wear and kinematic function of
W)+(S – S ); loss in weight of the wear specimen corrected
i i 0
the total facet prosthesis, the method for mounting components
for fluid absorption at end of cycle interval i.
in the test chamber shall not compromise the accuracy of
3.2.14 net volumetric wear NV of wear specimen (mm ),
i
assessment of the weight loss or stiffness variation during the
n—NV = NW/ρ at end of cycle interval i; where ρ = mass
i i
test. For example, prostheses having complicated superior and
density (for example, units of g/mm ) of the wear material.
inferior surfaces for contacting bone (for example, sintered
3.2.15 run-out (cycles), n—maximum number of cycles that beads, hydroxylapatite (HA) coating, plasma spray) may be
specially manufactured to modify that surface in a manner that
a test needs to be carried to if functional failure has not yet
occurred. does not affect the wear simulation.
5.2.3 The device should be securely (rigidly) attached at its
3.2.16 wear, n—progressive loss of material from the de-
bone-implant interface to the mating test fixtures.
vice(s) or device components as a result of relative motion at
5.2.4 The motion of the superior test fixture (more posterior
the surface with another body as measured by the change in
fixture in Figs. 1 and 2) relative to the inferior testing fixture
mass of the total facet prosthesis or components of the total
shall be constrained in three-dimensional space except for the
facet prosthesis. In the case of a non-articulating, compliant
components in the direction of specified test motions/loads.
total facet prosthesis, wear is defined simply as the loss of
5.2.5 Load and Motion:
material from the prosthesis. Note that inferior and superior
bone interface components are excluded from this definition
5.2.5.1 Facet loads (f ) are initially applied in the direction
x
(see 5.2.2). of the positive X-axis.
5.2.5.2 Flexion load and motion are positive moment and
3.2.17 facet load, n—AP directed force (applied in the
rotation about the Y-axis.
direction of the global X-axis) representing the resultant in the
5.2.5.3 Extensionloadandmotionarenegativemomentand
mid-sagittal XZ plane applied by the superior vertebra that
rotation about the Y-axis.
simulates the in vivo AP shear load F transmitted from
x
superior to inferior vertebra and resisted by the total facet 5.2.5.4 Lateral bend load and motion are positive and
prosthesis. negative moments and rotations about the X-axis.
F2694 − 07 (2013)
NOTE 1—This setup would require two rotational actuators and one translational actuator.
FIG. 1 Diagrams of Possible Test Apparatus for Allowing Simultaneous Lateral Bending and Axial Rotation Motions
with Anterior-Posterior Directed Facet Loading
NOTE 1—This setup would require two rotational actuators and one translational actuator
.
FIG. 2 Diagrams of Possible Test Apparatus for Allowing Simultaneous Flexion-Extension and Lateral Bending Motions
with Anterior-Posterior Directed Facet Loading
5.2.5.5 Axial rotation load and motion are positive and 6.1.2 To retard bacterial degradation, freeze and store the
negative moments and rotations about the Z-axis. serum until needed for testing. In addition, it is recommended
5.2.6 Frequency—Test frequency is to be determined and
that the serum contains a mass fraction of a suitable antibac-
justified by the user of this practice, and shall not exceed 2 Hz
terial agent to minimize bacterial degradation. Alternate lubri-
without adequate justification ensuring that the applied motion
cants(otherthanbovineserumsolution)shouldbeevaluatedto
(load) profiles remain within specified tolerances and that the
determine appropriate storage conditions.
total facet prosthesis’s wear and functional characteristics are
6.1.3 It is recommended that ethylene-diaminetetraacetic
not significantly affected. See X1.6.
acid (EDTA) be added to the serum at a concentration of 20
5.2.7 Cycle Counter—One complete motion is the entire
mM (7.45 g/L) to bind calcium in solution and minimize
range from starting position through the range of motion (or
precipitation of calcium phosphate onto the bearing surfaces.
loadwheninloadcontrol)andreturningtothestartingposition
The latter event has been shown to affect the friction and wear
(load). Cycles are to be counted using an automated counting
properties strongly, particularly of polyethylene/ceramic com-
device.
binations. The addition of EDTA to other testing mediums
should be evaluated.
6. Reagents and Materials
6.1.4 The bulk temperature of the testing medium shall be
6.1 Testing Medium:
maintained at 37 6 3°C unless otherwise justified.
6.1.1 A solution containing bovine serum diluted to a
6.1.5 The user may wish to reference Test Method F732 for
protein concentration of 20 g/L in deionized water shall be
used as the testing medium. additional guidance on serum preparation.
F2694 − 07 (2013)
6.2 The user is cautioned that internal heating of the measurement. Weigh each wear and control component three
prosthesis may cause localized temperatures to fall outside the times in rotation to detect random errors in the weighing
37 6 3°C of the testing medium. Internal local temperatures process.
maydependonanumberoffactorsincludingbutnotlimitedto
9.2 Record weights, W and S , as the initial weights of the
0 0
joint friction, material hysteresis, conductivity of the device-
wear and soak controls, respectively. Place the loaded soak
fixture materials, design, and test frequency. Localized el-
control specimens in holders in a soak chamber of the testing
evated temperatures may have an effect on the mechanical as
medium, such that the total surface area exposed to the testing
well as wear properties of the prosthesis. If the device
medium is the same as that of the wear components when
experiences localized elevated temperatures, the user must
mounted in the spinal testing apparatus. Maintain the soak
describe the effect the selected frequency and resultant local-
chamber temperature at 37 6 3°C (see 6.2), or specify and
ized temperature have on the test results or justify that the
justify if different.
effects are physiologically relevant. Refer to X1.5 for further
9.3 As a weight control for the testing, a minimum of two
information.
identical loaded soak control specimens in testing medium (see
6.1) shall be used. In other words, the loaded soak control
7. Sampling and Test Specimens
specimen must be loaded statically with the same facet load
7.1 It is suggested that a minimum sample size of six be
vector as described in Figs. 1 and 2 since it is well known that
used for each kinematic/load profile. However, note that, as for
load can significantly affect fluid absorption.
any ex
...
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