1、Designation: F 2694 07Standard Practice forFunctional and Wear Evaluation of Motion-PreservingLumbar Total Facet Prostheses1This standard is issued under the fixed designation F 2694; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last 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 practice provides guidance for the functional,kinematic and wear testing of motion-preserving total
3、 facetprostheses for the lumbar spine. These implants are intended toallow 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 boneimplant interface or the static characteristics of the prosthesiscompon
4、ents. Fatigue characteristics are included, but only as aby-product of cyclic wear testing under facet load and thus arenot addressed in the typical process of generating an S-Ncharacterization.1.3 Biocompatibility of the materials used in a total facetprosthesis are not addressed in this practice.1
5、.4 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.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us
6、er of this standard to establish appro-priate safety and health practices and determine the applica-bility 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 732 Test Meth
7、od for Wear Testing of Polymeric MaterialsUsed in Total Joint ProsthesesF 1714 Guide for Gravimetric Wear Assessment of Pros-thetic Hip-Designs in Simulator DevicesF 1877 Practice for Characterization of ParticlesF 2346 Test Methods for Static and Dynamic Characteriza-tion of Spinal Artificial Discs
8、3. Terminology3.1 DefinitionsAll functional and kinematic testing termi-nology is consistent with the referenced standards, unlessotherwise stated.3.1.1 coordinate systems/axes, nglobal XYZ orthogonalaxes are defined following a right-handed Cartesian coordinatesystem in which the XY plane is parall
9、el to and co-planar withthe superior endplate of the inferior vertebral body. The globalaxes are fixed relative to the inferior vertebral body, which inthis practice is also considered to be stationary with respect tothe test machines frame. Lower case letters, xyz, denote a localmoving orthogonal c
10、oordinate system attached to the superiorvertebral body with directions initially coincident with those ofthe global XYZ axes, respectively. The 3D motion of thesuperior relative to inferior vertebra is specified and is to bemeasured in terms of sequential Eulerian angular rotationsabout the xyz axe
11、s, respectively (z axial rotation, x lateral bend,and y flexion-extension).3.1.1.1 origin, ncenter of the global coordinate systemthat is located at the posterior medial position on the superiorendplate of the inferior vertebral body.3.1.1.2 X-axis, npositive X-axis is to be directed anteri-orly rel
12、ative to the specimens initial unloaded position.3.1.1.3 Y-axis, npositive Y-axis is directed laterally (to-ward the left) relative to the specimens initial unloadedposition.3.1.1.4 Z-axis, npositive Z-axis is to be directed superi-orly relative to the specimens initial unloaded position.3.1.2 fluid
13、 absorption, nfluid absorbed by the devicematerial during testing or while implanted in vivo.3.1.3 functional failure, npermanent deformation or wearthat renders the total facet prosthesis assembly ineffective orunable to perform its intended function.3.1.4 interval net volumetric wear rate VRidurin
14、g cycleinterval i (mm3/million cycles), nVRi= WRi/r; where r =mass density (for example, units of g/mm3) of the wearmaterial.1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.25 on Spinal Dev
15、ices.Current edition approved Dec. 1, 2007. Published December 2007.2For referenced ASTM 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 w
16、ebsite.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.5 interval net wear rate WRiduring cycle interval i(g/million cycles), nWRi=(NWi NWi-1)/(number of cyclesin interval i)106; for i =1,NWi-1=0.3.1.6 total facet prosthesis, nno
17、nbiologic structure in-tended to restore the support and motion of the naturalvertebral facet joint.3.1.7 kinematics profile, nrelative motion between adja-cent vertebral bodies that the total facet prosthesis is subjectedto while being tested.3.1.8 load profile, nloading that the device experiences
18、while being tested under a defined kinematics profile or theloading that the total facet prosthesis is subject to if tested inload control.3.1.9 radius of rotation, nthe distance between the centerof rotation and the functional position (for example, load-bearing contact point) of the total facet pr
19、osthesis, for a givenmotion (that is, flexion/extension, lateral bending, or axialrotation).3.1.10 mechanical failure, nfailure associated with adefect in the material (for example, fatigue crack) or of thebonding between materials that may or may not producefunctional failure.3.1.11 weight Siof soa
20、k control specimen (g), nS0initialand Siat end of cycle interval i.3.1.12 weight Wiof wear specimen (g), nW0initial and Wiat end of cycle interval i.3.1.13 net wear NWiof wear specimen (g), nNWi=(W0Wi)+(Si S0); loss in weight of the wear specimen correctedfor fluid absorption at end of cycle interva
21、l i.3.1.14 net volumetric wear NViof wear specimen (mm3),nNVi= NWi/r at end of cycle interval i; where r = massdensity (for example, units of g/mm3) of the wear material.3.1.15 run-out (cycles), nmaximum number of cycles thata test needs to be carried to if functional failure has not yetoccurred.3.1
22、.16 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 total facet prosthesis or components of the totalfacet prosthesis. In the case of a non-articulating, complianttotal
23、 facet prosthesis, wear is defined simply as the loss ofmaterial from the prosthesis. Note that inferior and superiorbone interface components are excluded from this definition(see 5.2.2).3.1.17 facet load, nAP directed force (applied in thedirection of the global X-axis) representing the resultant
24、in themid-sagittal XZ plane applied by the superior vertebra thatsimulates the in vivo AP shear load Fxtransmitted fromsuperior to inferior vertebra and resisted by the total facetprosthesis.4. Summary of Practice4.1 This practice can be used to describe the function,kinematics, and wear behavior of
25、 total facet prostheses sub-jected to cyclic loading/motion for relatively large numbers ofcycles. (For example, various designs of total facet prostheses,as well as the effects of materials, manufacturing techniquesand other design variables on one particular design can bestudied using this practic
26、e.)4.2 This practice is intended to be applicable to total facetprostheses that support and transmit motion by means of anarticulating joint or by use of compliant materials. Ceramics,metals, and/or polymers may be used in total facet prosthesisdesign, and it is the goal of this practice to enable a
27、 kinematicwear comparison of these devices, regardless of material andtype of device.5. Significance and Use5.1 Total Facet Prosthesis ComponentsThe total facetreplacement may comprise a variety of shapes and configura-tions. Its forms may include, but are not limited to, ball andsocket articulating
28、 joints, joints having a free-floating orsemi-constrained third body, metallic load-bearing surfaces,and spring and dampening mechanisms.Additionally, it may bea unilateral or bilateral design.5.2 Spinal Testing Apparatus:5.2.1 Test ChambersIn case of a multispecimen machine,each chamber shall be is
29、olated to prevent cross-contaminationof the test specimens. The chamber shall be made entirely ofcorrosion resistant materials, such as acrylic plastic or stainlesssteel, and shall be removable from the machine for thoroughcleaning between tests.5.2.2 Component Clamping/FixturingSince the purposeof
30、the test is to characterize the wear and kinematic function ofthe total facet prosthesis, the method for mounting componentsin the test chamber shall not compromise the accuracy ofassessment of the weight loss or stiffness variation during thetest. For example, prostheses having complicated superior
31、 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.5.2.3 The device should be securely (rigidly) attached at itsbone-implant interfa
32、ce to the mating test fixtures.5.2.4 The motion of the superior test fixture (more posteriorfixture in Figs. 1 and 2) relative to the inferior testing fixtureshall be constrained in three-dimensional space except for thecomponents in the direction of specified test motions/loads.5.2.5 Load and Motio
33、n:5.2.5.1 Facet loads (fx) are initially applied in the directionof the positive X-axis.5.2.5.2 Flexion load and motion are positive moment androtation about the Y-axis.5.2.5.3 Extension load and motion are negative moment androtation about the Y-axis.5.2.5.4 Lateral bend load and motion are positiv
34、e andnegative moments and rotations about the X-axis.5.2.5.5 Axial rotation load and motion are positive andnegative moments and rotations about the Z-axis.5.2.6 FrequencyTest frequency is to be determined andjustified by the user of this practice, and shall not exceed 2 Hzwithout adequate justifica
35、tion ensuring that the applied motion(load) profiles remain within specified tolerances and that thetotal facet prosthesiss wear and functional characteristics arenot significantly affected. See X1.6.5.2.7 Cycle CounterOne complete motion is the entirerange from starting position through the range o
36、f motion (orF2694072load when in load control) and returning to the starting position(load). 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
37、shall beused as the testing medium.6.1.2 To retard bacterial degradation, freeze and store theserum until needed for testing. In addition, it is recommendedthat the serum contains a mass fraction of a suitable antibac-terial agent to minimize bacterial degradation. Alternate lubri-cants (other than
38、bovine serum solution) should be evaluated todetermine appropriate storage conditions.6.1.3 It is recommended that ethylene-diaminetetraaceticacid (EDTA) be added to the serum at a concentration of 20mM (7.45 g/L) to bind calcium in solution and minimizeprecipitation of calcium phosphate onto the be
39、aring surfaces.The latter event has been shown to affect the friction and wearproperties strongly, particularly of polyethylene/ceramic com-binations. The addition of EDTA to other testing mediumsshould be evaluated.6.1.4 The bulk temperature of the testing medium shall bemaintained at 37 6 3C unles
40、s otherwise justified.6.1.5 The user may wish to reference Test Method F 732 foradditional guidance on serum preparation.6.2 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
41、depend on a number of factors including but not limited tojoint friction, material hysteresis, conductivity of the device-fixture materials, design, and test frequency. Localized el-evated temperatures may have an effect on the mechanical aswell as wear properties of the prosthesis. If the deviceexp
42、eriences localized elevated temperatures, the user mustdescribe the effect the selected frequency and resultant local-ized temperature have on the test results or justify that theeffects are physiologically relevant. Refer to X1.5 for furtherinformation.NOTEThis setup would require two rotational ac
43、tuators and one translational actuator.FIG. 1 Diagrams of Possible Test Apparatus for Allowing Simultaneous Lateral Bending and Axial Rotation Motionswith Anterior-Posterior Directed Facet LoadingNOTEThis setup would require two rotational actuators and one translational actuator.FIG. 2 Diagrams of
44、Possible Test Apparatus for Allowing Simultaneous Flexion-Extension and Lateral Bending Motionswith Anterior-Posterior Directed Facet LoadingF26940737. Sampling and Test Specimens7.1 It is suggested that a minimum sample size of six beused for each kinematic/load profile. However, note that, as fora
45、ny experimental comparison, the total number of neededspecimens will depend on the magnitude of the difference to beestablished, the repeatability of the results (standard deviation),and the level of statistical significance desired.7.2 The test assemblies (that is, total facet prosthesis com-ponent
46、s in the tested configuration) shall be labeled so they canbe traced and must be kept in a clean environment to avoidcontamination. The test assembly can be disassembled tofacilitate examination of surface conditions.8. Preparation of Apparatus8.1 The functional portion of the device to be tested mu
47、st beproduced using equivalent manufacturing methods as theimplantable form of the total facet prosthesis, including steril-ization.8.2 It is permissible to exclude nonfunctional features thatmay interfere with obtaining wear/functional measurements.For example, bone-implant interfaces such as HA, p
48、lasma-spray titanium, and beads may be omitted since they mayabrade the fixtures and thus produce an unwanted mixture offunctional and nonfunctional component wear particles (see5.2.2).8.3 It is permissible to make entirely different bone-implantinterface components (that is, superior and inferior s
49、urfaces)provided that the modification is properly justified and does notinterfere with an accurate measurement of the wear andfunctional characteristics of the device. For example, a ball andsocket joint prosthesis may be manufactured having the pol-ished articulation component (that is, functional surfaces orfeatures of the device) and an opposite side that mountsdirectly to the testing apparatus, thereby simplifying thefixturing demands.8.4 The requirements of Guide F 1714, Specimen Prepara-tion section, shall be followed.9. Procedure9.1 Alw
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