1、Designation: F2694 16Standard Practice forFunctional and Wear Evaluation of Motion-PreservingLumbar Total Facet Prostheses1This standard is issued under the fixed designation F2694; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 f
3、acetprostheses 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 prosthesiscomponen
4、ts. 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 a Stress-Life(S-N) characterization.1.3 Biocompatibility of the materials used in a total facetprosthesis are not addressed in this
5、 practice.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4.1 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.
6、5 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-bility of regulatory limitations prior to use.2. Referenced Doc
7、uments2.1 ASTM Standards:2F561 Practice for Retrieval and Analysis of MedicalDevices, and Associated Tissues and FluidsF732 Test Method for Wear Testing of Polymeric MaterialsUsed in Total Joint ProsthesesF1714 Guide for Gravimetric WearAssessment of ProstheticHip Designs in Simulator DevicesF1877 P
8、ractice for Characterization of ParticlesF2346 Test Methods for Static and Dynamic Characteriza-tion of Spinal Artificial DiscsF2423 Guide for Functional, Kinematic, and Wear Assess-ment of Total Disc Prostheses3. Terminology3.1 All functional and kinematic testing terminology isconsistent with the
9、referenced standards, unless otherwisestated.3.2 Definitions of Terms:3.2.1 mechanical failure, nfailure associated with a defectin the material (for example, fatigue crack) or of the bondingbetween materials that may or may not produce functionalfailure. F24233.2.2 run out (cycles), nmaximum number
10、 of cycles that atest needs to be carried to if functional failure has not yetoccurred. F24233.3 Definitions of Terms Specific to This Standard:3.3.1 coordinate systems/axes, nglobal XYZ orthogonalaxes are defined following a right-handed Cartesian coordinatesystem in which the XY plane is parallel
11、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 coor
12、dinate system attached to the superiorvertebral body with directions initially coincident with those ofthe global XYZ axes, respectively. The 3D motion of thesuperior relative to the inferior vertebra is specified and is to bemeasured in terms of sequential Eulerian angular rotationsabout the xyz ax
13、es, respectively (z axial rotation, x lateral bend,and y flexion-extension).3.3.1.1 origin, ncenter of the global coordinate systemthat is located at the posterior medial position on the superiorendplate of the inferior vertebral body.3.3.1.2 X-axis, npositive X-axis is to be directed anteriorlyrela
14、tive to the specimens initial unloaded position.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 Devices.Current edition approved Dec. 1, 2016. Published January 2017. Originall
15、yapproved in 2007. Last previous edition approved in 2013 as F2694 07 (2013).DOI: 10.1520/F2694-16.2For 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 Doc
16、ument Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on
17、Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.3.1.3 Y-axis, npositive Y-axis is directed laterally (to-ward the left) relative to the specimens initial unloadedposition.3.3.1.
18、4 Z-axis, npositive Z-axis is to be directed superi-orly relative to the specimens initial unloaded position.3.3.2 fluid absorption, nfluid absorbed by the devicematerial during testing or while implanted in vivo.3.3.3 functional failure, npermanent deformation or wearthat renders the total facet pr
19、osthesis assembly ineffective orunable to perform its intended function.3.3.4 interval net volumetric wear rate VRi during cycleinterval i (mm3/million cycles), nVRi= WRi/; where =mass density (for example, units of g/mm3) of the wearmaterial.3.3.5 interval net wear rate WRiduring cycle interval i(g
20、/million cycles), nWRi=(NWi NWi-1)/(number of cyclesin interval i)106; for i =1,NWi-1=0.3.3.6 total facet prosthesis, nnonbiologic structure in-tended to restore the support and motion of the naturalvertebral facet joint.3.3.7 kinematics profile, nrelative motion between adja-cent vertebral bodies t
21、hat the total facet prosthesis is subjectedto while being tested.3.3.8 load profile, nloading that the device experienceswhile being tested under a defined kinematics profile or theloading that the total facet prosthesis is subject to if tested inload control.3.3.9 radius of rotation, nthe distance
22、between the centerof rotation and the functional position (for example, load-bearing contact point) of the total facet prosthesis, for a givenmotion (that is, flexion/extension, lateral bending, or axialrotation).3.3.10 weight Siof soak control specimen (g), nS0initialand Siat end of cycle interval
23、i.3.3.11 weight Wiof wear specimen (g), nW0initial and Wiat end of cycle interval i.3.3.12 net wear NWiof wear specimen (g), nNWi=(W0Wi)+(Si S0); loss in weight of the wear specimen correctedfor fluid absorption at end of cycle interval i.3.3.13 net volumetric wear NViof wear specimen (mm3),nNVi= NW
24、i/ at end of cycle interval i; where = massdensity (for example, units of g/mm3) of the wear material.3.3.14 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
25、 prosthesis or components of the totalfacet prosthesis. In the case of a non-articulating, complianttotal 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).3.3.15
26、facet load, nAP directed force (applied in thedirection of the global X-axis) representing the resultant 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. S
27、ummary of Practice4.1 This practice can be used to describe the function,kinematics, and wear behavior of 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, man
28、ufacturing techniquesand other design variables on one particular design can bestudied using this practice.)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
29、/or polymers may be used in total facet prosthesisdesign, and it is the goal of this practice to enable a 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
30、of shapes and configura-tions. Its forms may include, but are not limited to, ball andsocket articulating joints, joints having a free-floating orsemi-constrained third body, metallic load-bearing surfaces,and spring and dampening mechanisms. Additionally, it mayhave a unilateral or bilateral design
31、.5.2 Spinal Testing Apparatus: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 ofcorrosion-resistant materials, such as acrylic plastic or stainlesssteel, and shall be removabl
32、e from the machine for thoroughcleaning between tests.5.2.2 Component Clamping/FixturingSince the purposeof 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 o
33、f the weight loss or stiffness variation during thetest. 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
34、affect the wear simulation.5.2.3 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 (more posteriorfixture in Figs. 1 and 2) relative to the inferior testing fixtureshall be constrained in three-dime
35、nsional space except for thecomponents in the direction of specified test motions/loads.5.2.5 Load and Motion: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
36、and motion are negative moment androtation about the Y-axis.F2694 1625.2.5.4 Lateral bend load and motion are positive 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 frequen
37、cy shall be determined andjustified by the user of this practice, and shall not exceed 2 Hzwithout adequate justification ensuring that the applied motion(load) profiles remain within specified tolerances and that thetotal facet prosthesiss wear and functional characteristics arenot significantly af
38、fected. See X1.6.5.2.7 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(load). Cycles are to be counted using an automated countingdevice.6. Reagents and Materials6.1 Testing Me
39、dium: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 store theserum until needed for testing. In addition, it is recommendedthat the serum contain a mass fract
40、ion of a suitable antibacterialagent to minimize bacterial degradation. Alternate lubricants(other than 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 o
41、f 20mM (7.45 g/L) to bind calcium in solution and minimizeprecipitation of calcium phosphate onto the bearing 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 mediums
42、should be evaluated.NOTE 1This 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 Motionswith Anterior-Posterior Directed Facet LoadingNOTE 1This setup would require two r
43、otational actuators and one translational actuator.FIG. 2 Diagrams of Possible Test Apparatus for Allowing Simultaneous Flexion-Extension and Lateral Bending Motionswith Anterior-Posterior Directed Facet LoadingF2694 1636.1.4 The bulk temperature of the testing medium shall bemaintained at 37 6 3C u
44、nless otherwise justified.6.1.5 The user may wish to reference Test Method F732 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 temperaturesm
45、ay depend on a number of factors including, but not limitedto, joint friction, material hysteresis, conductivity of thedevice-fixture materials, design, and test frequency. Localizedelevated temperatures may have an effect on the mechanical aswell as wear properties of the prosthesis. If the devicee
46、xperiences 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 insignificant. Refer to X1.5 for further information.7. Sampling and Test Specimens7.1 It is suggested that
47、 a minimum sample size of six beused for each kinematic/load profile. However, note that, as forany 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 sta
48、tistical significance desired.7.2 The test assemblies (that is, total facet prosthesis com-ponents 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 surfa
49、ce conditions.8. Preparation of Apparatus8.1 The functional portion of the device to be tested must 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, plasma-spray titanium, and beads may be omitted since they mayabrade the fixtures and thus produce an unwanted mixture offunctional and nonfuncti
