1、Designation: F 2423 05Standard Guide forFunctional, Kinematic, and Wear Assessment of Total DiscProstheses1This standard is issued under the fixed designation F 2423; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is intended to provide guidance for thefunctional, kinematic, and wear testing of total disc prosthesesand, to
3、 this end, describes test methods for assessment of thewear or functional characteristics, or both, of total discprostheses.1.2 Both lumbar and cervical prostheses are addressed.1.3 Load and kinematic profiles for lumbar and cervicaldevices are not identical and, therefore, are addressed sepa-rately
4、 in the guide.1.4 Partial disc replacements, such as nucleus replacementsor facet joint replacements, are not intended to be addressed.1.5 Wear is assessed using a weight loss method in a testingmedium as defined in this guide.1.6 This guide is not intended to address any potentialfailure mode as it
5、 relates to the fixation of the implant to itsbony interfaces.1.7 It is the intent of this guide to enable comparison ofintervertebral disc (IVD) prostheses with regard to kinematic,functional, and wear characteristics when tested under thespecified conditions. It must be recognized, however, that t
6、hereare many possible variations in the in vivo conditions. A singlelaboratory simulation with a fixed set of parameters may not beuniversally representative.1.8 In order that the data be reproducible and comparablewithin and between laboratories, it is essential that uniformprocedures are establish
7、ed. This guide is intended to facilitateuniform methods for testing and reporting of data for total discreplacement prostheses.1.9 Without a substantial clinical retrieval history of IVDprostheses, actual loading profiles and patterns cannot bedelineated at the time of the writing of this guide. It
8、thereforefollows that the load and motion conditions specified by thisguide do not necessarily accurately reproduce those occurringin vivo. Rather, the maximum loads and motions specified inthis guide represent a severe and therefore conservative casefor testing the wear properties of IVD prostheses
9、. Because ofthis, a substantially greater rate of wear may be realized thanthat which may occur during the routine daily activities of atypical patient. It should be noted, however, that a fullcharacterization of a candidate IVD prosthesis should includetesting under both typical and extreme conditi
10、ons.1.10 The values stated in SI units are to be regarded as thestandard with the exception of angular measurements, whichmay be reported in either degrees or radians.1.11 This guide is not intended to be a performance stan-dard. It is the responsibility of the user of this guide tocharacterize the
11、safety and effectiveness of the prosthesis underevaluation.1.12 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-b
12、ility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F 561 Practice for Retrieval and Analysis of Medical De-vices, and Associated Tissues and FluidsF 1582 Terminology Relating to Spinal ImplantsF 1714 Guide for Gravimetric Wear Assessment of Pros-thetic Hip-Design
13、s in Simulator DevicesF 1877 Practice for Characterization of ParticlesF 2077 Test Methods For Intervertebral Body Fusion De-vices3. Terminology3.1 DefinitionsAll functional and kinematic testing termi-nology is consistent with the referenced standards, unlessotherwise stated.3.1.1 coordinate system
14、/axes, nglobal XYZ orthogonalaxes are defined following a right-handed Cartesian coordinatesystem in which the XY plane is to bisect the sagittal planeangle between superior and inferior surfaces that are intendedto simulate the adjacent vertebral end plates. The global axesare stationary relative t
15、o the IVD prostheses inferior end plate1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.25 on Spinal Devices.Current edition approved Nov. 15, 2005. Published January 2006.2For referenced ASTM
16、 standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
17、ken, PA 19428-2959, United States.fixture, which, in this guide, is also considered to be stationarywith respect to the test machines frame. Lower case letters,xyz, denote a local, moving orthogonal coordinate systemattached to the superior end plate fixturing with directionsinitially coincident wit
18、h those of the global XYZ axes, respec-tively. The 3-D motion of the superior relative to inferior endplate fixture is specified and is to be measured in terms ofsequential Eulerian angular rotations about the xyz axes,respectively (z, axial rotation; x, lateral bending; and y,flexion-extension).3.1
19、.1.1 origin, ncenter of the global coordinate system islocated at the initial position of the total disc replacementsinstantaneous center of rotation (COR). F 15823.1.1.2 X-axis, npositive X-axis is a global fixed axisrelative to the testing machines stationary base and is to bedirected anteriorly r
20、elative to the specimens initial unloadedposition.3.1.1.3 Y-axis, npositive Y-axis is a global fixed axisrelative to the testing machines stationary base and is directedlaterally relative to the specimens initial unloaded position.3.1.1.4 Z-axis, npositive Z-axis is a global fixed axisrelative to th
21、e testing machines stationary base and is to bedirected superiorly relative to the specimens initial unloadedposition.3.1.1.5 x-axis, npositive x-axis is a fixed axis relative tothe IVD prosthesis and a moving axis relative to the globalcoordinate system and is directed anteriorly relative to thepro
22、sthesis.3.1.1.6 y-axis, npositive y-axis is a fixed axis relative tothe IVD prosthesis and a moving axis relative to the globalcoordinate system and is directed laterally relative to theprosthesis.3.1.1.7 z-axis, npositive z-axis is a fixed axis relative tothe IVD prosthesis and a moving axis relati
23、ve to the globalcoordinate system and is directed superiorly relative to theprosthesis.3.1.2 degradation, nloss of material or function or mate-rial properties as a result of causes other than that associatedwith wear.3.1.3 fluid absorption, nfluid absorbed by the devicematerial during testing or wh
24、ile implanted in vivo.3.1.4 functional failure, npermanent deformation or wearthat renders the IVD prosthesis assembly ineffective or unableto resist load/motion or any secondary effects that result in areduction of clinically relevant motions or the motions in-tended by the design of the device.3.1
25、.5 interval net volumetric wear rate VRiduring cycleinterval i (mm3/million cycles), nVRi= WRi/r, where r =mass density (for example, units of g/mm3) of the wearmaterial.3.1.6 interval net wear rate WRiduring cycle interval i(g/million cycles), nWRi=(NWi NWi-1)/(number of cyclesin interval i)*106.3.
26、1.6.1 DiscussionFor i =1,NWi-1=0.3.1.7 intervertebral disc (IVD) prosthesis, nnonbiologicstructure intended to restore the support and motion or aportion thereof between adjacent vertebral bodies.3.1.8 kinematic profile, nrelative motion between adja-cent vertebral bodies that the IVD prosthesis is
27、subjected towhile being tested.3.1.9 load profile, nloading that the device experienceswhile being tested under a defined kinematic profile or theloading that the IVD prosthesis is subject to if tested in loadcontrol.3.1.10 mechanical failure, nfailure associated with adefect in the material (for ex
28、ample, fatigue crack) or of thebonding between materials that may or may not producefunctional failure.3.1.11 net wear NWiof wear specimen (g), n NWi5W0 Wi! 1 Si S0!; loss in weight of the wear specimencorrected for fluid absorption at end of cycle interval i.3.1.12 net volumetric wear NViof wear sp
29、ecimen (mm3),n NVi5 NWi/r at end of cycle interval i where r = massdensity (for example, units of g/mm3) of the wear material.3.1.13 preload, nThe resultant force Fpreloadapplied tothe superior or inferior fixture-end plate that simulates the invivo load that an IVD prosthesis (original healthy disc
30、) mustresist.3.1.13.1 DiscussionBased on a healthy disc, the primarycomponent would be an axial compressive force FZin thedirection of the negative global Z axis, and it would passthrough the in vivo physiologic instantaneous center of rotation(COR) of the IVD prosthesis. Shear components in the XYp
31、lane would be FXand FY. Lateral bending moment MXandflexion/extension moment MYcomponents would be createdabout the initial COR when the preload force does not passthrough it.3.1.14 run out (cycles), nmaximum number of cycles thata test needs to be carried to if functional failure has not yetoccurre
32、d.3.1.15 wear, nprogressive loss of material from the de-vice(s) or device components as a result of relative motion atthe surface with another body as measured by the change inmass of the IVD prosthesis or components of the IVDprosthesis. Or in the case of a nonarticulating, compliant IVDprosthesis
33、, wear is defined simply as the loss of material fromthe prosthesis.3.1.15.1 DiscussionNote that inferior and superior boneinterface components are excluded from this definition; see5.2.2.3.1.16 weight Siof soak control specimen (g), nS0initialand Siat end of cycle interval i.3.1.17 weight Wiof wear
34、 specimen (g), nW0initial and Wiat end of cycle interval i.4. Significance and Use4.1 This guide can be used to describe the function, kine-matics, and wear behavior of IVD prostheses subjected tocyclic loading/motion for relatively large numbers of cycles(for example, various designs of IVD prosthe
35、ses, as well as theeffects of materials, manufacturing techniques and other designvariables on one particular design can be studied using thisguide).4.2 This guide is intended to be applicable to IVD prosthe-ses that support and transmit motion by means of an articulat-ing joint or by use of complia
36、nt materials. Ceramics, metals, orF2423052polymers, or combination thereof, are used in IVD prosthesisdesign, and it is the goal of this guide to enable a kinematicwear comparison of these devices, regardless of material andtype of device.5. Apparatus5.1 Total Disc Prosthesis ComponentsThe total dis
37、c re-placement may comprise a variety of shapes and configura-tions. Some known forms include ball and socket articulatingjoints, biconcave joints having a free-floating or semi-constrained third body, metallic endplates bonded to elastomercores, and single-axis hinge joints.5.2 Spinal Testing Appar
38、atus:5.2.1 Test ChambersIn case of a multispecimen machine,each chamber shall be isolated to prevent cross-contaminationof the test specimens. The chamber shall be made entirely ofnoncorrosive components, such as acrylic plastic or stainlesssteel, and shall be easily removable from the machine forth
39、orough cleaning between tests.5.2.2 Component Clamping/FixturingSince the purposeof the test is to characterize the wear and kinematic function ofthe IVD prosthesis, the method for mounting components inthe test chamber shall not compromise the accuracy of assess-ment of the weight loss or stiffness
40、 variation during the test.For example, prostheses having complicated superior andinferior surfaces for contacting bone (for example, sinteredbeads, hydroxylapatite (HA) coating, plasma spray) may bespecially manufactured to modify that surface in a manner thatdoes not affect the wear simulation.5.2
41、.3 The device should be securely (rigidly) attached at itsbone-implant interface to the mating test fixtures.5.2.4 The motion of the superior test fixture relative to theinferior testing fixture shall be unconstrained in three-dimensional space except for the components in the directionof specified
42、test motions/loads.5.2.5 Load and Motion (components in Table 1 and Table2):5.2.5.1 An axial preload is to be a compressive load appliedin the direction of the negative Z-axis. Deviations from this asthe IVD moves from its initial position are to be reported asshear components FX, FY, and moments MX
43、and MY.5.2.5.2 Flexion load and motion are positive moment, MY,and rotation about the y-axis.5.2.5.3 Extension load and motion are negative moment,MY, and rotation about the y-axis.5.2.5.4 Lateral bend load and motion are positive andnegative moments, MX, and rotations about the x-axis.5.2.5.5 Torsi
44、onal load and motion are positive and negativemoments, MZand rotations about the z-axis.5.2.6 FrequencyTest frequency is to be determined andjustified by the user of this guide, and shall not exceed 2 Hzwithout adequate justification ensuring that the applied motion(load) profiles remain within spec
45、ified tolerances and that theIVD prosthesis wear and functional characteristics are notsignificantly affected. See 6.1.5.5.2.7 Cycle CounterOne complete motion is the entirerange from starting position through the range of motion (orload when in load control) and returning to the starting position(l
46、oad). Cycles are to be counted using an automated countingdevice.6. Reagents and Materials6.1 Testing Medium:6.1.1 A solution containing bovine serum diluted to aprotein concentration of 20 g/L in deionized water shall beused as the testing medium.6.1.2 To retard bacterial degradation, freeze and st
47、ore theserum until needed for test. In addition, the testing mediummay contain 0.2 % sodium azide (or other suitable antibiotic/antimycotic) to minimize bacterial degradation. Other lubri-cants should be evaluated to determine appropriate storageconditions.6.1.3 It is recommended that ethylene-diami
48、netetraaceticacid (EDTA) be added to the serum at a concentration of 20mMto bind calcium in solution and minimize precipitation ofcalcium phosphate onto the bearing surfaces. The latter eventhas been shown to affect the friction and wear propertiesstrongly, particularly of polyethylene/ceramic combi
49、nations.The addition of EDTA to other testing media should beevaluated.6.1.4 The bulk temperature of the testing medium shall bemaintained at 37 6 3C, unless otherwise specified.6.1.5 The user is cautioned that internal heating of theprosthesis may cause localized temperatures to fall outside the37 6 3C of the testing medium. Internal local temperaturesmay depend on a number of factors, including but not limitedto joint friction, material hysteresis, conductivity of the device-fixture materials, design, and test frequency. Localized el
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