1、Designation: F2790 10Standard Practice forStatic and Dynamic Characterization of Motion PreservingLumbar Total Facet Prostheses1This standard is issued under the fixed designation F2790; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the 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 static anddynamic testing of Lumbar Total Facet Prostheses (FP
3、). Theseimplants are intended to allow motion and lend support to oneor more functional spinal unit(s) through replacement of thenatural facets.1.2 These test methods are intended to provide a basis forthe mechanical comparison among past, present, and futurenon-biologic FP. These test methods allow
4、 comparison ofdevices with different methods of application to the lumbarspine. These test methods are intended to enable the user tomechanically compare devices and do not purport to provideperformance standards for them.1.3 These test methods describe static and dynamic tests byspecifying load typ
5、es and specific methods of applying theseloads.1.4 These test methods do not purport to address all clini-cally relevant failure modes for FP, some of which will bedevice specific. For example, these test methods do not addressimplant wear resistance under expected in vivo loads andmotions. In addit
6、ion, the biologic response to wear debris is notaddressed in these test methods.1.5 Requirements are established for measuring displace-ments and evaluating the stiffness of FP.1.6 Some devices may not be testable in all test configura-tions.1.7 The values stated in SI units are to be regarded as th
7、estandard with the exception of angular measurements, whichmay be reported in terms of either degrees or radians.1.8 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand
8、are not considered standard.2. Referenced Documents2.1 ASTM Standards:2D638 Test Method for Tensile Properties of PlasticsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE468 Practice for Presentation of Constant Amplitude Fa-tigue Test
9、Results for Metallic MaterialsE739 Practice for Statistical Analysis of Linear or Linear-ized Stress-Life ( S-N) and Strain-Life (e-N) Fatigue DataF1582 Terminology Relating to Spinal Implants3. Terminology3.1 DefinitionsAll functional and kinematic testing termi-nology is consistent with the refere
10、nced standards (includingTeminology E6 and Terminology F1582), unless otherwisestated.3.1.1 coordinate systems/axesGlobal XYZ orthogonalaxes are defined following a right-handed Cartesian coordinatesystem in which the XY plane is parallel to and co-planar withthe superior endplate of the inferior ve
11、rtebral body. Alternativecoordinate systems may be used with justification. The globalaxes are fixed relative to the inferior vertebral body. Lowercase letters, xyz, denote a local moving orthogonal coordinatesystem attached to the superior vertebral body with directionsinitially coincident with tho
12、se of the global XYZ axes, respec-tively. The 3D motion of the superior relative to inferiorvertebra is specified and is to be measured in terms ofsequential Eulerian angular rotations about the xyz axes,respectively (z axial rotation, x lateral bend, and y flexion-extension).3.1.1.1 origincenter of
13、 the global coordinate system thatis located at the posterior medial position on the superiorendplate of the inferior vertebral body.3.1.1.2 X-axispositive X-axis is to be directed anteriorlyrelative to the specimens initial unloaded position.1This practice is under the jurisdiction ofASTM Committee
14、 F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.25 on Spinal Devices.Current edition approved Jan. 1, 2010. Published February 2010. DOI: 10.1520/F279010.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custome
15、r 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.3.1.1.3 Y-axispositive Y-axis is direc
16、ted laterally (towardthe left) relative to the specimens initial unloaded position.3.1.1.4 Z-axispositive Z-axis is to be directed superiorlyrelative to the specimens initial unloaded position.3.1.2 failurefunctional failure or substantial mechanicalfailure.3.1.2.1 functional failurepermanent deform
17、ation resultingfrom fracture, plastic deformation, or loosening beyond theultimate displacement or loosening that renders the spinalimplant assembly ineffective or unable to adequately resistload.3.1.2.2 mechanical failurefailure associated with a defectin the material (for example, fatigue crack) o
18、r of the bondingbetween materials that may or may not produce functionalfailure.3.1.3 fatigue lifethe number of cycles, N, that the FP cansustain at a particular load or moment before failure occurs.3.1.4 intended method of applicationa FP may containdifferent types of features to stabilize the impl
19、ant-tissue inter-face such as threads, spikes, and textured surfaces. Each typeof feature has an intended method of application or attachmentto the spine.3.1.5 insertion point of an anchorthe location where theanchor is attached to the test block. The insertion points shownin Fig. 1 are to be adhere
20、d to if possible. In situations where thedesign of the spinal implant assembly or the manufacturerssurgical instructions for installation dictate otherwise, theattachment points may deviate from these dimensions.3.1.6 longitudinal directionthe initial spatial orientationbetween the insertion points
21、in the superior test blocks and theinferior test blocks.3.1.7 maximum run-out load or momentthe maximumload or moment for a given test that can be applied to a FPwhere all of the tested constructs have withstood 10 000 000cycles without failure.3.1.8 mechanical deteriorationdeterioration that is vis
22、ibleto the naked eye and is associated with mechanical damage tothe device under test (for example, initiation of fatigue crack orsurface wear).3.1.9 permanent deformationthe remaining linear or an-gular displacement (axialmm, angulardegrees or radians)relative to the initial unloaded condition of t
23、he FP after theapplied load or moment has been removed.3.1.10 radius of rotationthe distance between the centerof rotation and the functional position (for example, load-bearing contact point) of the FP, for a given motion (that is,flexion/extension, lateral bending, or axial rotation).3.1.11 spinal
24、 implant assemblya complete spinal implantconfiguration as intended for surgical use. A spinal implantassembly may contain anchors, interconnections, and longitu-dinal elements and may contain transverse elements.3.1.12 stiffness (axialN/mm, angularNmm/degree orNmm/radian)the slope of the initial li
25、near portion of theload-displacement curve or the slope of the initial linearportion of the moment-angular displacement curve. This isillustrated as the slope of the line OG in Fig. 2. The device maynot exhibit an isolated linear portion on the load/displacementcurve, due to the complicated nature o
26、f these devices. As such,these data are information only.FIG. 1 UHMWPE Test Block FIG. 2 Typical Load Displacement CurveF2790 1023.1.13 superior/inferior spinal implant constructthe supe-rior or inferior spinal implant assembly attached to the testblock.3.1.14 test blockthe component of the test app
27、aratus formounting the FP in the intended test configuration.3.1.15 tightening torquethe specified torque that is ap-plied to the various fasteners of the spinal implant assembly.3.1.16 torsional ultimate load (Nm)the maximum torqueapplied to a spinal implant assembly (the torque at Point E inFig. 2
28、). The ultimate torque should be a function of the deviceand not of the load cell or testing machine.3.1.17 total facet prosthesisnonbiologic structure in-tended to restore the support and motion of the vertebral facetjoint.3.1.18 ultimate displacement (axialmm, angulardegrees or radians)the linear
29、or angular displacement asso-ciated with the ultimate load or ultimate moment. This isillustrated as the displacement, OF,inFig. 2.3.1.19 ultimate load or moment (axialN, angularNmm)the maximum applied load, F, or moment, M, trans-mitted to the FP. This is illustrated as point E in Fig. 2.3.1.20 zer
30、o displacement intercept (mm)the intersectionof the straight line section of the load displacement curve andzero load axis (the zero displacement reference Point O in Fig.2).4. Summary of Practice4.1 This practice is proposed for the mechanical testing ofFP.4.2 All tests are to be performed on the p
31、rosthesis size withthe smallest safety factor for the levels indicated for implan-tation. If this worst-case size cannot be determined usingtheoretical or experimental methods such as simple stresscalculations or finite element analysis, then all available sizesor a justified selection are to be tes
32、ted and the complete rangeof results are to be reported.4.3 Static and dynamic testing of the devices will simulate amotion segment via a gap between two Ultra High MolecularWeight Polyethylene (UHMWPE) test blocks (Fig. 1, Fig. 3,orFig. 4). The UHMWPE used to manufacture the test blocksshould have
33、a tensile breaking strength equal to 40 6 3 MPa(see Specification D638). The UHMWPE will eliminate theeffects of the variability of bone properties and morphology forthe fatigue tests.4.4 Static and dynamic tests will evaluate the devices. Theuser of this practice must decide which series of tests a
34、reapplicable to the device in question. The user of this practicemay choose to use all or a selection of the tests described fortesting a particular device.4.5 This practice is intended to be applicable to FP thatsupport and transmit motion by means of an articulating jointor by use of compliant mat
35、erials and/or design. Ceramics,metals, and/or polymers may be used in FP design, and it is thegoal of this practice to enable a comparison of these devices,regardless of material and type of device.5. Significance and Use5.1 Facet Prosthesis ComponentsThe facet replacementmay comprise a variety of s
36、hapes and configurations. Its formsmay include, but are not limited to, ball and socket articulatingjoints, joints having a free-floating or semi-constrained thirdNOTE(A) Anterior-Posterior, (B) Superior-Inferior, (C) Medial-Lateral setups are shown. These setups require one translational actuator a
37、nd mayrequire specific fixturing. Test blocks are shown in grey. The arrow indicates the loading direction.FIG. 3 Diagrams of Possible Test Setups for Translational Loading of a FPF2790 103body, metallic load-bearing surfaces, and spring and dampen-ing mechanisms.Additionally, it may be a unilateral
38、 or bilateraldesign.5.2 These test methods are designed to quantify the staticand dynamic characteristics of different designs of FP. The testsare conducted in vitro in order to allow for analysis ofindividual devices and comparison of the mechanical perfor-mance of multiple designs.5.3 The loads ap
39、plied to the FP may differ from the complexloading seen in vivo, and therefore, the results from these testsmay not directly predict in vivo performance. The results,however, can be used to compare mechanical performance indifferent devices.5.4 Fatigue testing in a simulated body fluid or saline may
40、cause fretting, corrosion, or lubricate the interconnections andthereby affect the relative performance of tested devices. Thistest should be conducted in a 0.9 % saline environmental bathat 37C at a maximum rate of 10 Hz for all metallic devices and2 Hz for non-metallic devices. Other test environm
41、ents such asa simulated body fluid, a saline drip or mist, distilled water,other type of lubrication or dry could also be used withadequate justification. Likewise, alternative test frequenciesmay be used with adequate justification to ensure that it doesnot impact the device performance.5.5 It is w
42、ell known that the failure of materials is depen-dent upon stress, test frequency, surface treatments, and envi-ronmental factors. Therefore, when determining the effect ofchanging these parameters (for example, frequency, material,or environment), care should be taken to allow for appropriateinterp
43、retation of the results. In particular, it may be necessaryto assess the influence of test frequency on device fracturewhile holding the test environment, implant materials andprocessing, and implant geometry constant.6. Apparatus and Setup6.1 Test machines will conform to the requirements ofPractic
44、es E4.6.2 The test apparatus will allow multiple loading regimesto be applied to all forms of FP.6.3 The test block should be created according to Fig. 1.Variations from this design to accommodate a devices fixationmethod or features should be reported and justified.6.4 The interpedicular spacing (s
45、uperior-to-inferior center-to-center distance between bone anchors) shall be set at 38 mmwhen installing the device and at the beginning of each test.The implants should be placed in the UHMWPE blocksaccording to the recommended surgical technique. For devicesthat do not require pedicular fixation a
46、ppropriate test blocksshould be manufactured to ensure proper evaluation of thefixation components.6.5 Install the FP in the UHMWPE blocks according to themanufacturers instructions. If necessary, utilize an aluminumspacer block between the superior and inferior UHMWPEblocks to fix them with respect
47、 to each other during installationand remove after installation is complete. The spacer blockshould ensure that the device is installed with the proper activelongitudinal length.NOTE(A) Simulated Flexion-Extension, (B) Axial Rotation, (C) Lateral Bending setups are shown. These setups require one ro
48、tational actuator andmay require specific fixturing. The arrow indicates the rotation direction. Test blocks are shown in grey. The position of the axis of rotation should bebased on the information in Table X1.1.FIG. 4 Diagrams of Possible Test Setups for Rotational Loading of a FPF2790 1046.6 The
49、motion of the superior test construct relative to theinferior test construct shall be constrained in three-dimensionalspace except for the components in the direction of specifiedtest motions/loads.6.7 Translational Test Option Setup:6.7.1 The linear actuator of the test frame is connected to thesuperior test block so that its axis is collinear with the testdirection (Fig. 3).6.7.2 The inferior test block should be rigidly attached to thebase of the test frame so that it is aligned appropriately withrespect to the superior construc
