1、Designation: F 2624 07Standard Test Method forStatic, Dynamic, and Wear Assessment of Extra-DiscalSpinal Motion Preserving Implants1This standard is issued under the fixed designation F 2624; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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 test method is intended to provide test methods forthe static, dynamic, and wear testing of
3、 extra-discal motionpreserving implants. These implants are intended to augmentspinal stability without significant tissue removal while allow-ing motion of the functional spinal unit(s).1.2 Wear is assessed using a weight loss method and adimensional analysis for determining wear of components used
4、in extra-discal spinal motion preserving procedures, usingtesting medium as defined in this test method (6.1).1.3 This test method is not intended to address any potentialfailure mode as it relates to the fixation of the device to its bonyinterfaces.1.4 It is the intent of this test method to enable
5、 comparisonof motion preserving, extra-discal implants with regard tokinematic, functional, and wear characteristics when testedunder the specified conditions. It must be recognized, however,that there are many possible variations in the in vivo condi-tions. A single laboratory simulation with a fix
6、ed set ofparameters may not be universally representative.1.5 This test method is not intended to address facetarthroplasty devices.1.6 This test method prescribes the use of pure angularrotations for assessing the mechanical characteristics of extra-discal motion preserving implants. This test meth
7、od does not,however, prescribe methods for assessing the mechanicalcharacteristics of the device in translation (for example,anterior/posterior translation), though this type of linear motionmay be clinically relevant.1.7 In order that the data be reproducible and comparablewithin and between labora
8、tories, it is essential that uniformprocedures are established. This test method is intended tofacilitate uniform testing methods and data reporting forextra-discal motion preserving implants.1.8 Without a substantial clinical retrieval history of spinal,motion preserving extra-discal implants, actu
9、al loading profilesand patterns cannot be delineated at the time of the writing ofthis test method. It therefore follows that the motion profilesspecified by this test method do not necessarily accuratelyreproduce those occurring in vivo. Rather this method providesuseful boundary/endpoint condition
10、s for evaluating implantdesigns in a functional manner.1.9 This test method is not intended to be a performancestandard. It is the responsibility of the user of this test methodto characterize the safety and effectiveness of the device underevaluation.1.10 The values stated in SI units are to be reg
11、arded as thestandard. The values given in parentheses are for informationonly.1.11 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.1.12 This standard does not purport to address all of thesa
12、fety 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 Documents2.1 ASTM Standards:2F 561 Practice for Retrieval a
13、nd Analysis of Medical De-vices, and Associated Tissues and FluidsF 1714 Guide for Gravimetric Wear Assessment of Pros-thetic Hip-Designs in Simulator DevicesF 1717 Test Methods for Spinal Implant Constructs in aVertebrectomy ModelF 1877 Practice for Characterization of ParticlesF 2003 Practice for
14、Accelerated Aging of Ultra-High Mo-lecular Weight Polyethylene after Gamma Irradiation inAirF 2423 Guide for Functional, Kinematic, and Wear Assess-ment of Total Disc Prostheses3. Terminology3.1 All terminology is consistent with the referenced stan-dards, unless otherwise stated.1This test method i
15、s under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.25 on Spinal Devices.Current edition approved Dec. 15, 2007. Published March 2008.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
16、ntact 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 Conshohocken, PA 19428-2959, United States.3.1.1 center of rota
17、tion (COR)the point about which thesimulated vertebral bodies rotate in performing the range ofmotion (ROM) specified in this test method.3.1.2 coordinate system/axesthree orthogonal axes aredefined following a right-handed Cartesian coordinate system.The XY-plane is to bisect the sagittal plane bet
18、ween superiorand inferior surfaces that are intended to simulate the adjacentvertebral end plates. The positive Z-axis is to be directedsuperiorly. Force components parallel to the XY-plane are shearcomponents of loading. The compressive axial force is definedto be the component in the negative Z-di
19、rection. Torsional loadis defined to be the component of moment about the Z-axis.3.1.3 degradationloss of material or function or materialproperties due to causes other than that associated with wear.3.1.4 extra-discal motion preserving device or implantanon-biologic structure, which lies entirely o
20、utside the interver-tebral disc space and is intended to at least partially support themotion/load between adjacent vertebral bodies. In this testmethod, this definition does not include facet arthroplastydevices.3.1.5 fluid absorptionfluid absorbed by the device mate-rial during testing or while im
21、planted in vivo.3.1.6 functional failurepermanent deformation or wearthat renders the extra-discal motion preserving implant assem-bly ineffective or unable to adequately resist load/motion orany secondary effects that result in a reduction of clinicallyrelevant motions or the motions intended by th
22、e design of thedevice.3.1.7 functional spinal unit (FSU)two adjacent vertebrae,including the intervertebral disc, and all adjoining ligamentsbetween them, specifically excluding all other connectivetissues such as muscles (Ref (1).33.1.8 interval net volumetric wear rateVRiduring cycleinterval i (mm
23、3/million cycles):VRi5WRir(1)where:r = mass density (for example, units of g/mm3) of the wearmaterial.3.1.9 interval net wear rateWRiduring cycle interval i(g/million cycles):WRi5NWiNWi1!# of cycles in interval i!3 106(2)Note, for i =1,NWi1=0.3.1.10 kinematic profilethe relative motion between adja-
24、cent vertebral bodies that the extra-discal motion preservingdevice is subjected to while being tested.3.1.11 mechanical failurefailure associated with a defectin the material (for example, fatigue crack) or of the bondingbetween materials that may or may not produce functionalfailure.3.1.12 net vol
25、umetric wearNViof wear specimen (mm3):NVi5NWir(3)at end of cycle interval i.where:r = mass density (for example, units of g/mm3) of the wearmaterial.3.1.13 net wearNWiof wear specimen (g):NWi5 W0Wi!1SiS0! (4)Loss in weight of the wear specimen corrected for fluidabsorption at end of cycle interval i
26、.3.1.14 originthe center of the coordinate system is lo-cated at the center of rotation of the testing fixture.3.1.15 run-out (cycles)the maximum number of cyclesthat a test needs to be carried to if functional failure has not yetoccurred.3.1.16 wearthe progressive loss of material from thedevice(s)
27、 or device components as a result of relative motion atthe surface with another body as measured by the change inmass of the components of the implants. Or in the case of anon-articulating, compliant device, wear is defined simply asthe loss of material from the device. Note that bone interfacecompo
28、nents of the device are excluded from this definition (see5.2.2, 5.2.4, and 5.2.5).3.1.17 weight Siof soak control specimen (g)S0initial andSiat end of cycle interval i.3.1.18 weight Wiof wear specimen (g)W0initial and Wiatend of cycle interval i.3.1.19 X-axisthe positive X-axis is a global fixed ax
29、isrelative to the testing machines stationary base and is to bedirected anteriorly relative to the specimens initial unloadedposition.3.1.20 Y-axisthe positive Y-axis is a global fixed axisrelative to the testing machines stationary base and is directedlaterally relative to the specimens initial unl
30、oaded position.3.1.21 Z-axisthe positive Z-axis is a global fixed axisrelative to the testing machines stationary base and is to bedirected superiorly relative to the specimens initial unloadedposition.4. Significance and Use4.1 This test method is designed to quantify the static,dynamic, and wear c
31、haracteristics of different designs ofextra-discal motion preserving implants using testing medium(see 6.1) for simulating the physiologic environment at 37C.Wear is assessed using a weight loss method in addition todimensional analyses. Weight loss is determined after subject-ing the implants to dy
32、namic profiles specified in this testmethod. This information will allow the manufacturer or enduser of the product to understand how the specific device inquestion performs under the test conditions prescribed in thistest method.4.2 This test method is intended to be applicable forextra-discal moti
33、on preserving implants. These implants aug-ment the motion/load bearing characteristics between adjacentvertebral bodies, and thereby fully or partially support andtransmit motion by means of an articulating joint or by use of3The boldface numbers in parentheses refer to a list of references at the
34、end ofthis standard.F2624072compliant materials. Ceramics, metals, or polymers, or com-binations thereof are used in implant design, and it is the goalof this test method to enable a comparison of the static,dynamic, and wear properties generated by these devices,regardless of material and type of d
35、evice.5. Apparatus5.1 Implant ComponentsThe extra-discal motion preserv-ing device may comprise a variety of shapes and configura-tions. Some known forms include screws which rigidly pur-chase the vertebral bodies coupled with flexible, elasticmembers; other forms may include rigid members coupled i
36、n asemi-constrained manner (for example, screws, and rods con-nected with a universal joint with defined motion limitations).Forms of these devices which employ hooks that engageposterior spinal elements are also envisioned; these devicesmay support extension loading only or loads in both flexionand
37、 extension.5.2 Spinal Testing Apparatus:5.2.1 Test ChambersIn case of a multi-specimen machine,each chamber shall be isolated to prevent cross-contaminationof the test specimens. The chamber shall be made entirely ofnon-corrosive components, such as acrylic, plastic, or stainlesssteel, and shall be
38、easy to remove from the machine forthorough cleaning between tests.5.2.2 For wear testing, the test chamber also must isolate thespinal motion preserving device/construct from wear centerscreated by the testing fixtures.5.2.3 For all testing, the actuator of the testing machine isconnected to the su
39、perior testing block. The user must deter-mine the appropriate degrees of freedom for the devicedepending on its intended use (see 5.2.6).5.2.4 Component Clamping/FixturingSince one of thepurposes of the test is to characterize the wear properties of theextra-discal motion preserving device, the met
40、hod for mount-ing components in the test chamber shall not compromise theaccuracy of assessment of the weight loss or stiffness variationduring the test. For example, implants having complicatedsurfaces for contacting bone (for example, sintered beads,hydroxylapatite (HA) coating, plasma spray) may
41、be speciallymanufactured to modify that surface in a manner that does notaffect the wear simulation.5.2.5 The device should be securely (rigidly) attached at itsbone-implant interface to the test fixtures.5.2.6 The extra-discal motion preserving construct matedwith the testing fixture shall be const
42、rained with the appropri-ate degrees of freedom for the intended use. For example, somedevices may only be intended to provide stability in onemotion, which would dictate that the test fixture may beconstrained in all other motions. Other devices, which providestability along multiple degrees of fre
43、edom, would necessitatehaving more degrees of freedom incorporated into the testingfixture. The user shall determine and justify the appropriatedegrees of freedom of the test fixture.5.2.7 Blocks are to be made from polyacetal homopolymer(minimum ultimate tensile strength shall be no less than 61MPa
44、). The simulated spinous process is to be made from 304series stainless steel (minimum ultimate tensile strength shallbe no less than 500 MPa). See Note 1.NOTE 1304 stainless steel is used for the simulated spinous processfor rigidity purposes to enable the user to more accurately characterize theme
45、chanical performance of the extra-discal motion preserving implant.5.2.7.1 The simulated spinous process is only needed if theimplants are intended to be attached to the spinous process invivo.5.2.7.2 The simulated spinous process must be manufac-tured in such a way as to be rigidly attached to the
46、polyacetalhomopolymer block. Modifications are allowed to conform todevice design and the manufacturers intended use of theextra-discal implant. Note that if wear is expected between theimplant and the spinous process, the user should consideraltering the surface finish of the simulated spinous proc
47、ess tooffer a more appropriate test model for assessing the mechani-cal characteristics of the implant.5.2.8 Fig. 1 and Fig. 2 are of an extra-discal motionpreserving implant attached to simulated vertebral bodies (Fig.3) and testing fixtures. Note that the represented testingfixtures, which attach
48、to the simulated vertebral bodies and thetesting instrument, are for illustrative purposes only. The usermust design the appropriate fixtures for the device being testedand means by which they are rigidly fixed to the testinginstrument.5.2.9 Range of Motion (ROM):5.2.9.1 Axial compressive loads/moti
49、ons are applied in thedirection of the negative Z-axis.5.2.9.2 Flexion loads/motions are generated by positiverotation about the Y-axis.5.2.9.3 Extension loads/motions are generated by negativerotation about the Y-axis.5.2.9.4 Lateral bend loads/motions are generated by positiveand negative rotation about the X-axis.5.2.9.5 Torsional loads/motions are generated by positiveand negative rotation about the Z-axis.5.2.9.6 Center of Rotation (COR)See X1.6 for a discus-sion on the COR. Since the COR will vary in accordance withdevice design and inte
