ASTM F2423-05

Standard Guide for Functional, Kinematic, and Wear Assessment of Total Disc Prostheses

SIGNIFICANCE AND USE
This guide can be used to describe the function, kinematics, and wear behavior of IVD prostheses subjected to cyclic loading/motion for relatively large numbers of cycles (for example, various designs of IVD prostheses, as well as the effects of materials, manufacturing techniques and other design variables on one particular design can be studied using this guide).
This guide is intended to be applicable to IVD prostheses that support and transmit motion by means of an articulating joint or by use of compliant materials. Ceramics, metals, or polymers, or combination thereof, are used in IVD prosthesis design, and it is the goal of this guide to enable a kinematic wear comparison of these devices, regardless of material and type of device.
SCOPE
1.1 This guide is intended to provide guidance for the functional, kinematic, and wear testing of total disc prostheses and, to this end, describes test methods for assessment of the wear or functional characteristics, or both, of total disc prostheses.
1.2 Both lumbar and cervical prostheses are addressed.
1.3 Load and kinematic profiles for lumbar and cervical devices are not identical and, therefore, are addressed separately in the guide.
1.4 Partial disc replacements, such as nucleus replacements or facet joint replacements, are not intended to be addressed.
1.5 Wear is assessed using a weight loss method in a testing medium as defined in this guide.
1.6 This guide is not intended to address any potential failure mode as it relates to the fixation of the implant to its bony interfaces.
1.7 It is the intent of this guide to enable comparison of intervertebral disc (IVD) prostheses with regard to kinematic, functional, and wear characteristics when tested under the specified conditions. It must be recognized, however, that there are many possible variations in the in vivo conditions. A single laboratory simulation with a fixed set of parameters may not be universally representative.
1.8 In order that the data be reproducible and comparable within and between laboratories, it is essential that uniform procedures are established. This guide is intended to facilitate uniform methods for testing and reporting of data for total disc replacement prostheses.
1.9 Without a substantial clinical retrieval history of IVD prostheses, actual loading profiles and patterns cannot be delineated at the time of the writing of this guide. It therefore follows that the load and motion conditions specified by this guide do not necessarily accurately reproduce those occurring in vivo. Rather, the maximum loads and motions specified in this guide represent a severe and therefore conservative case for testing the wear properties of IVD prostheses. Because of this, a substantially greater rate of wear may be realized than that which may occur during the routine daily activities of a typical patient. It should be noted, however, that a full characterization of a candidate IVD prosthesis should include testing under both typical and extreme conditions.
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.
1.11 This guide is not intended to be a performance standard. It is the responsibility of the user of this guide to characterize the safety and effectiveness of the prosthesis under evaluation.
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

• Status: Historical
• Publication Date: 14-Nov-2005
• 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

Relations

• Replaced By: ASTM F2423-11 - Standard Guide for Functional, Kinematic, and Wear Assessment of Total Disc Prostheses
• Effective Date: 01-Jul-2011
• Referred By: ASTM F2789-10(2020) - Standard Guide for Mechanical and Functional Characterization of Nucleus Devices
• Effective Date: 15-Nov-2005
• Referred By: ASTM F2759-19 - Standard Guide for Assessment of the Ultra-High Molecular Weight Polyethylene (UHMWPE) Used in Orthopedic and Spinal Devices
• Effective Date: 15-Nov-2005
• Referred By: ASTM F2624-12(2020) - Standard Test Method for Static, Dynamic, and Wear Assessment of Extra-Discal Single Level Spinal Constructs
• Effective Date: 15-Nov-2005
• Referred By: ASTM F3295-18 - Standard Guide for Impingement Testing of Total Disc Prostheses
• Effective Date: 15-Nov-2005
• Referred By: ASTM F3292-19 - Standard Practice for Inspection of Spinal Implants Undergoing Testing
• Effective Date: 15-Nov-2005
• Referred By: ASTM F2694-16(2020) - Standard Practice for Functional and Wear Evaluation of Motion-Preserving Lumbar Total Facet Prostheses
• Effective Date: 15-Nov-2005

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: F2423 – 05
Standard Guide for
Functional, Kinematic, and Wear Assessment of Total Disc
Prostheses
This standard is issued under the fixed designation F2423; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. 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 this, a substantially greater rate of wear may be realized than
that which may occur during the routine daily activities of a
1.1 This guide is intended to provide guidance for the
typical patient. It should be noted, however, that a full
functional, kinematic, and wear testing of total disc prostheses
characterization of a candidate IVD prosthesis should include
and, to this end, describes test methods for assessment of the
testing under both typical and extreme conditions.
wear or functional characteristics, or both, of total disc
1.10 The values stated in SI units are to be regarded as the
prostheses.
standard with the exception of angular measurements, which
1.2 Both lumbar and cervical prostheses are addressed.
may be reported in either degrees or radians.
1.3 Load and kinematic profiles for lumbar and cervical
1.11 This guide is not intended to be a performance stan-
devices are not identical and, therefore, are addressed sepa-
dard. It is the responsibility of the user of this guide to
rately in the guide.
characterizethesafetyandeffectivenessoftheprosthesisunder
1.4 Partial disc replacements, such as nucleus replacements
evaluation.
or facet joint replacements, are not intended to be addressed.
1.12 This standard does not purport to address all of the
1.5 Wear is assessed using a weight loss method in a testing
safety concerns, if any, associated with its use. It is the
medium as defined in this guide.
responsibility of the user of this standard to establish appro-
1.6 This guide is not intended to address any potential
priate safety and health practices and determine the applica-
failure mode as it relates to the fixation of the implant to its
bility of regulatory limitations prior to use.
bony interfaces.
1.7 It is the intent of this guide to enable comparison of
2. Referenced Documents
intervertebral disc (IVD) prostheses with regard to kinematic,
2.1 ASTM Standards:
functional, and wear characteristics when tested under the
F561 Practice for Retrieval and Analysis of Medical De-
specified conditions. It must be recognized, however, that there
vices, and Associated Tissues and Fluids
are many possible variations in the in vivo conditions.Asingle
F1582 Terminology Relating to Spinal Implants
laboratorysimulationwithafixedsetofparametersmaynotbe
F1714 Guide for Gravimetric Wear Assessment of Pros-
universally representative.
thetic Hip Designs in Simulator Devices
1.8 In order that the data be reproducible and comparable
F1877 Practice for Characterization of Particles
within and between laboratories, it is essential that uniform
F2077 Test Methods For Intervertebral Body Fusion De-
procedures are established. This guide is intended to facilitate
vices
uniform methods for testing and reporting of data for total disc
replacement prostheses.
3. Terminology
1.9 Without a substantial clinical retrieval history of IVD
3.1 Definitions—All functional and kinematic testing termi-
prostheses, actual loading profiles and patterns cannot be
nology is consistent with the referenced standards, unless
delineated at the time of the writing of this guide. It therefore
otherwise stated.
follows that the load and motion conditions specified by this
3.1.1 coordinate system/axes, n—global XYZ orthogonal
guide do not necessarily accurately reproduce those occurring
axes are defined following a right-handed Cartesian coordinate
in vivo. Rather, the maximum loads and motions specified in
system in which the XY plane is to bisect the sagittal plane
this guide represent a severe and therefore conservative case
angle between superior and inferior surfaces that are intended
for testing the wear properties of IVD prostheses. Because of
to simulate the adjacent vertebral end plates. The global axes
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
Surgical Materials and Devices and is the direct responsibility of Subcommittee For referenced ASTM standards, visit the ASTM website, www.astm.org, or
F04.25 on Spinal Devices. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved Nov. 15, 2005. Published January 2006. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
F2423-05. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2423 – 05
are stationary relative to the IVD prostheses’inferior end plate 3.1.8 kinematic profile, n—relative motion between adja-
fixture, which, in this guide, is also considered to be stationary cent vertebral bodies that the IVD prosthesis is subjected to
with respect to the test machine’s frame. Lower case letters, while being tested.
xyz, denote a local, moving orthogonal coordinate system 3.1.9 load profile, n—loading that the device experiences
attached to the superior end plate fixturing with directions while being tested under a defined kinematic profile or the
initially coincident with those of the global XYZ axes, respec- loading that the IVD prosthesis is subject to if tested in load
tively. The 3-D motion of the superior relative to inferior end control.
plate fixture is specified and is to be measured in terms of 3.1.10 mechanical failure, n—failure associated with a
sequential Eulerian angular rotations about the xyz axes, defect in the material (for example, fatigue crack) or of the
respectively (z, axial rotation; x, lateral bending; and y, bonding between materials that may or may not produce
flexion-extension). functional failure.
3.1.1.1 origin, n—center of the global coordinate system is 3.1.11 net wear NW of wear specimen (g), n— NW 5
i i
~W – W ! 1 ~S – S !; loss in weight of the wear specimen
located at the initial position of the total disc replacement’s
0 i i 0
instantaneous center of rotation (COR). F1582 corrected for fluid absorption at end of cycle interval i.
3.1.12 net volumetric wear NV of wear specimen (mm ),
3.1.1.2 X-axis, n—positive X-axis is a global fixed axis
i
n— NV 5 NW/r at end of cycle interval i where r = mass
relative to the testing machine’s stationary base and is to be
i i
density (for example, units of g/mm ) of the wear material.
directed anteriorly relative to the specimen’s initial unloaded
3.1.13 preload, n—The resultant force F applied to
position.
preload
the superior or inferior fixture-end plate that simulates the in
3.1.1.3 Y-axis, n—positive Y-axis is a global fixed axis
vivo load that an IVD prosthesis (original healthy disc) must
relative to the testing machine’s stationary base and is directed
resist.
laterally relative to the specimen’s initial unloaded position.
3.1.13.1 Discussion—Based on a healthy disc, the primary
3.1.1.4 Z-axis, n—positive Z-axis is a global fixed axis
component would be an axial compressive force F in the
Z
relative to the testing machine’s stationary base and is to be
direction of the negative global Z axis, and it would pass
directed superiorly relative to the specimen’s initial unloaded
through the in vivo physiologic instantaneous center of rotation
position.
(COR) of the IVD prosthesis. Shear components in the XY
3.1.1.5 x-axis, n—positive x-axis is a fixed axis relative to
plane would be F and F . Lateral bending moment M and
X Y X
the IVD prosthesis and a moving axis relative to the global
flexion/extension moment M components would be created
Y
coordinate system and is directed anteriorly relative to the
about the initial COR when the preload force does not pass
prosthesis.
through it.
3.1.1.6 y-axis, n—positive y-axis is a fixed axis relative to
3.1.14 run out (cycles), n—maximum number of cycles that
the IVD prosthesis and a moving axis relative to the global
a test needs to be carried to if functional failure has not yet
coordinate system and is directed laterally relative to the
occurred.
prosthesis.
3.1.15 wear, n—progressive loss of material from the de-
3.1.1.7 z-axis, n—positive z-axis is a fixed axis relative to
vice(s) or device components as a result of relative motion at
the IVD prosthesis and a moving axis relative to the global
the surface with another body as measured by the change in
coordinate system and is directed superiorly relative to the
mass of the IVD prosthesis or components of the IVD
prosthesis.
prosthesis. Or in the case of a nonarticulating, compliant IVD
3.1.2 degradation, n—loss of material or function or mate-
prosthesis, wear is defined simply as the loss of material from
rial properties as a result of causes other than that associated
the prosthesis.
with wear.
3.1.15.1 Discussion—Note that inferior and superior bone
3.1.3 fluid absorption, n—fluid absorbed by the device
interface components are excluded from this definition; see
material during testing or while implanted in vivo.
5.2.2.
3.1.4 functional failure, n—permanent deformation or wear
3.1.16 weight S of soak control specimen (g), n—S initial
i 0
that renders the IVD prosthesis assembly ineffective or unable
and S at end of cycle interval i.
i
to resist load/motion or any secondary effects that result in a
3.1.17 weight W of wear specimen (g), n—W initialand W
i 0 i
reduction of clinically relevant motions or the motions in-
at end of cycle interval i.
tended by the design of the device.
4. Significance and Use
3.1.5 interval net volumetric wear rate VR during cycle
i
interval i (mm /million cycles), n—VR = WR/r, where r =
i i 4.1 This guide can be used to describe the function, kine-
mass density (for example, units of g/mm ) of the wear
matics, and wear behavior of IVD prostheses subjected to
material.
cyclic loading/motion for relatively large numbers of cycles
3.1.6 interval net wear rate WR during cycle interval i
(for example, various designs of IVD prostheses, as well as the
i
(g/million cycles), n—WR =((NW – NW )/(number of cycles
effectsofmaterials,manufacturingtechniquesandotherdesign
i i i-1
in interval i))*10 .
variables on one particular design can be studied using this
3.1.6.1 Discussion—For i=1, NW =0.
guide).
i-1
3.1.7 intervertebral disc (IVD) prosthesis, n—nonbiologic 4.2 This guide is intended to be applicable to IVD prosthe-
structure intended to restore the support and motion or a ses that support and transmit motion by means of an articulat-
portion thereof between adjacent vertebral bodies. ing joint or by use of compliant materials. Ceramics, metals, or
F2423 – 05
TABLE 1 Test Profiles and Associated Parameters for Cervical TABLE 2 Test Profiles and Associated Parameters for Lumbar
IVD Prostheses IVD Prostheses
Preferred Alternate Preferred Alternate
Axial Axial
Displacement Control: Load Control: Displacement Control: Load Control:
Test Profile Preload, N Test Profile Preload, N
Range of Motion Applied Moment Range of Motion Applied Moments,
(3-5) (6)
A A
(ROM), degree (4) Ranges, Nm (4) (ROM), degree Nm
B
Flexion/extension 100 67.5 62.0 Flexion/extension 1200 67.5 610
Lateral bend/ 100 66 62.0 Rotation 1200 63 (7,9) 610
rotation 66 64.0 Lateral bending 1200 66 (7,9) 612
A A
TheuseroftheguidemustdeterminewhethertheROMwillbeequallydivided Approximated based on a review of ROM (p. 111) and average flexibility and
between flexion and extension or weighted more toward one of the motion stiffness coefficients (p. 47) (7).
B
directions. Depending on the device design, the balance of ROM should be appropriate
to the expected ROM in a clinical situation (8).
polymers, or combination thereof, are used in IVD prosthesis
design, and it is the goal of this guide to enable a kinematic
5.2.5.5 Torsional load and motion are positive and negative
wear comparison of these devices, regardless of material and
moments, M and rotations about the z-axis.
Z
type of device.
5.2.6 Frequency—Test frequency is to be determined and
justified by the user of this guide, and shall not exceed 2 Hz
5. Apparatus
without adequate justification ensuring that the applied motion
5.1 Total Disc Prosthesis Components—The total disc re-
(load) profiles remain within specified tolerances and that the
placement may comprise a variety of shapes and configura-
IVD prosthesis’ wear and functional characteristics are not
tions. Some known forms include ball and socket articulating
significantly affected. See 6.1.5.
joints, biconcave joints having a free-floating or semi-
5.2.7 Cycle Counter—One complete motion is the entire
constrained third body, metallic endplates bonded to elastomer
range from starting position through the range of motion (or
cores, and single-axis hinge joints.
loadwheninloadcontrol)andreturningtothestartingposition
5.2 Spinal Testing Apparatus:
(load). Cycles are to be counted using an automated counting
5.2.1 Test Chambers—In case of a multispecimen machine,
device.
each chamber shall be isolated to prevent cross-contamination
of the test specimens. The chamber shall be made entirely of
6. Reagents and Materials
noncorrosive components, such as acrylic plastic or stainless
6.1 Testing Medium:
steel, and shall be easily removable from the machine for
6.1.1 A solution containing bovine serum diluted to a
thorough cleaning between tests.
protein concentration of 20 g/L in deionized water shall be
5.2.2 Component Clamping/Fixturing—Since the purpose
used as the testing medium.
of the test is to characterize the wear and kinematic function of
6.1.2 To retard bacterial degradation, freeze and store the
the IVD prosthesis, the method for mounting components in
serum until needed for test. In addition, the testing medium
the test chamber shall not compromise the accuracy of assess-
may contain 0.2 % sodium azide (or other suitable antibiotic/
ment of the weight loss or stiffness variation during the test.
antimycotic) to minimize bacterial degradation. Other lubri-
For example, prostheses having complicated superior and
cants should be evaluated to determine appropriate storage
inferior surfaces for contacting bone (for example, sintered
conditions.
beads, hydroxylapatite (HA) coating, plasma spray) may be
6.1.3 It is recommended that ethylene-diaminetetraacetic
specially manufactured to modify that surface in a manner that
acid(EDTA)beaddedtotheserumataconcentrationof20mM
does not affect the wear simulation.
to bind calcium in solution and minimize precipitation of
5.2.3 The device should be securely (rigidly) attac
...