1、Designation: F2267 04 (Reapproved 2011)Standard Test Method forMeasuring Load Induced Subsidence of Intervertebral BodyFusion Device Under Static Axial Compression1This standard is issued under the fixed designation F2267; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, 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 test method specifies the materials and methods forthe axial
3、compressive subsidence testing of non-biologic in-tervertebral body fusion devices, spinal implants designed topromote arthrodesis at a given spinal motion segment.1.2 This test method is intended to provide a basis for themechanical comparison among past, present, and future non-biologic interverte
4、bral body fusion devices. This test method isintended to enable the user to mechanically compare interver-tebral body fusion devices and does not purport to provideperformance standards for intervertebral body fusion devices.1.3 This test method describes a static test method byspecifying a load typ
5、e and a specific method of applying thisload. This test method is designed to allow for the comparativeevaluation of intervertebral body fusion devices.1.4 Guidelines are established for measuring test blockdeformation and determining the subsidence of intervertebralbody fusion devices.1.5 Since som
6、e intervertebral body fusion devices requirethe use of additional implants for stabilization, the testing ofthese types of implants may not be in accordance with themanufacturers recommended usage.1.6 UnitsThe values stated in SI units are to be regardedas the standard with the exception of angular
7、measurements,which may be reported in terms of either degrees or radians.1.7 The use of this standard may involve the operation ofpotentially hazardous equipment. This standard does not pur-port to address all of the safety concerns, if any, associatedwith its use. It is the responsibility of the us
8、er of this standardto establish appropriate safety and health practices anddetermine the applicability of regulatory limitations prior touse.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesF1582 Terminology Relating to Spinal ImplantsF1839 Specificat
9、ion for Rigid Polyurethane Foam for Useas a Standard Material for Testing Orthopaedic Devicesand InstrumentsF2077 Test Methods For Intervertebral Body Fusion De-vices3. Terminology3.1 All subsidence testing terminology is consistent with thereferenced standards above, unless otherwise stated.3.2 Def
10、initions:3.2.1 coordinate system/axesthree orthogonal axes aredefined by Terminology F1582 as seen in Fig. 4. The center ofthe coordinate system is located at the geometric center of theintervertebral body fusion device assembly. The X-axis is alongthe longitudinal axis of the implant, with positive
11、 X in theanterior direction, Y is lateral, and Z is cephalic.3.2.2 ideal insertion locationthe implant location withrespect to the simulated inferior and superior vertebral bodies(polyurethane) dictated by the type, design, and manufacturerssurgical installation instructions.3.2.3 intended method of
12、 applicationintervertebral bodyfusion devices may contain different types of stabilizingfeatures such as threads, spikes, and knurled surfaces. Eachtype of feature has an intended method of application orattachment to the spine.3.2.4 intended spinal locationthe anatomic region of thespine intended f
13、or the intervertebral body fusion device.Intervertebral body fusion devices may be designed anddeveloped for specific regions of the spine such as the lumbar,thoracic, and cervical spine. Also, there potentially exist1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Sur
14、gical Materials and Devices and is the direct responsibility of SubcommitteeF04.25 on Spinal Devices.Current edition approved Dec. 1, 2011. Published January 2012. Originallyapproved in 2003. Last previous edition approved in 2004 as F2267 04. DOI:10.1520/F2267-04R11.2For referenced ASTM standards,
15、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 Conshohocken, PA 1942
16、8-2959, United States.different anatomical surgical approaches, which will result indifferent implant orientation at different levels of the spine.3.2.5 intervertebral subsidencethe process of a vertebralbody cavitating or sinking around an implanted intervertebralbody fusion device resulting in the
17、 loss of intradiscal height.3.2.6 intradiscal heightthe straight-line distance along theZ-axis between the unaltered simulated vertebral bodies. SeeFig. 1.FIG. 1 Intradiscal Height DiagramFIG. 2 Typical Load-Displacement Curve with 1.5 mm (Thoracic Device) Offset for Polyurethane Foam Test BlocksF22
18、67 04 (2011)23.2.7 load pointthe point through which the resultantforce on the intervertebral device passes (that is, the geometriccenter of the superior fixtures sphere) (Fig. 4).3.2.8 offset displacementoffset on the displacement axisequal to 1 mm for cervical disc devices, 1.5 mm for thoracicdevi
19、ces, and 2 mm for lumbar devices (see distance AB in Fig.2)3.2.9 simulated vertebral bodiesthe component of the testapparatus for mounting the intervertebral body fusion device.3.2.10 stiffness, (N/mm)the slope of the initial linearportion of the load-displacement curve (see the slope of lineAE in F
20、ig. 2).3.2.11 test block heightthe linear distance along theZ-axis from the top surface of the superior simulated vertebralbody to the bottom surface of the inferior simulated vertebralbody with the intervertebral body fusion device in position.The block heights shall be 70 mm, 60 mm, and 40 mm forl
21、umbar, thoracic, and cervical intervertebral disc devices re-spectively. See Fig. 4.3.2.12 yield loadthe applied load, F, transmitted by thepushrod (assumed equal to force component parallel to andindicated by load cell), required to produce a permanentdeformation equal to the offset displacement fo
22、und by plottingline BC with stiffness, K, originating at point B (see Point D inFig. 2).4. Summary of Test Method4.1 To measure load induced subsidence, a test method isproposed for the axial compression of intervertebral bodyfusion devices specific to the lumbar, thoracic, and cervicalspine.4.2 The
23、 axial compressive subsidence testing of the in-tervertebral body fusion device will be conducted in a simu-lated motion segment via a gap between two polyurethanefoam blocks.4.3 Grade 15 foam shall be employed conforming to Speci-fication F1839.5. Significance and Use5.1 Intervertebral body fusion
24、devices are generally simplegeometric shaped devices, which are often porous or hollow innature. Their function is to support the anterior column of thespine to facilitate arthrodesis of the motion segment.5.2 This test method is designed to quantify the subsidencecharacteristics of different design
25、s of intervertebral body fusionFIG. 3 Typical Load-Displacement Plot Comparison for Test Specimens in Metallic and Polyurethane Test BlocksF2267 04 (2011)3devices since this is a potential clinical failure mode. Thesetests are conducted in vitro in order to simplify the comparisonof simulated verteb
26、ral body subsidence induced by the in-tervertebral body fusion devices.5.3 The static axial compressive loads that will be applied tothe intervertebral body fusion devices and test blocks willdiffer from the complex loading seen in vivo, and therefore, theresults from this test method may not be use
27、d to directly predictin vivo performance. The results, however, can be used tocompare the varying degrees of subsidence between differentintervertebral body fusion device designs for a given density ofsimulated bone.5.4 The location within the simulated vertebral bodies andposition of the interverte
28、bral body fusion device with respect tothe loading axis will be dependent upon the design andmanufacturers recommendation for implant placement.6. Apparatus6.1 Test machines will conform to the requirements ofPractices E4.6.2 The intradiscal height, H, (Fig. 1) shall be determinedfrom vertebral body
29、 and disc morphometric data at the in-tended level of application. Suggested heights are as follows:10 mm for the lumbar spine, 6 mm for the thoracic spine and4 mm for the cervical spine. The user of this test method shouldselect the intradiscal height that is appropriate for the devicebeing tested.
30、6.3 Axial Compressive Testing ApparatusAn exampleaxial compressive test fixture can be referenced in Figs. 4 and5. Two pieces of polyurethane foam or rigid metal are rigidlymounted inside the test fixture. The actuator of the testingmachine is connected to the pushrod by a minimal friction balland s
31、ocket joint or universal joint (that is, unconstrained inbending). The pushrod is connected to the superior fixture by aminimal friction sphere joint (that is, unconstrained in bendingand torsion). The inferior sphere portion firmly holds theinferior polyurethane block and is rigidly fixed within th
32、e basesocket so that no rotation occurs. The hollow pushrod andsuperior sphere should be of minimal weight so as to beconsidered a “two force” member. It thus applies to theintervertebral device a resultant force directed along thepushrods axes and located at the center of the superiorfixtures spher
33、e joint (the geometric center of the device beingtested). The polyurethane blocks are to have surfaces that mategeometrically with the intervertebral device similar to how thedevice is intended to mate with vertebral end plates. The testapparatus will be assembled such that the Z-axis of theinterver
34、tebral device is initially coincident with the pushrodsaxis and collinear with the axis of the testing machinesactuator and load cell. The length of the pushrod between thecenter of the ball-and-socket joint to the center of the sphericalsurface is to be a minimum of 38 cm. This is required tominimi
35、ze deviation of the pushrods axis (direction of appliedforce, F) from that of the test machines load cell axis. In otherwords, this is to minimize the error in using and reporting thatthe force indicated by the load cell Findis the applied load, F,and is equal to the compressive force, Fz, on the in
36、tervertebralbody fusion device. For example,a1mmdisplacement of thespherical surfaces center in the XY plane would produce anangle between axes of 0.15, (10 mm producing 1.5). Figs. 4and 5 are schematics of this test set up.FIG. 4 Subsidence Test FixtureF2267 04 (2011)47. Sampling7.1 Implants may be
37、 retested provided that the tested devicehas undergone a microscopic and geometric examination withno damage or permanent deformation detected.7.2 Each pair of polyurethane foam blocks shall be used forone test only.7.3 The test assemblies (that is, intervertebral body fusiondevice and polyurethane
38、blocks) shall be labeled and shall bemaintained according to good laboratory practice. The testassembly can be disassembled to facilitate examination ofsurface conditions.7.4 All tests shall have a minimum of five test samples.7.5 All implants should be prepared in the manner in whichthey would norm
39、ally be used clinically.8. Procedure for Static Axial Compression Test8.1 Two different testing conditions shall be used:8.1.1 Rigid metallic blocks shall be used to determine thestiffness of the device being tested.8.1.2 Polyurethane blocks will be used to determine thedevices propensity to subside
40、.FIG. 5 Subsidence Test FixtureF2267 04 (2011)58.2 The intervertebral body fusion devices are to be insertedinto two prepared rigid metallic blocks following the manu-facturers suggested protocol for insertion of the implant (thatis, the geometry of the implant configuration shall match thatof in vi
41、vo conditions). The initial intradiscal height, H, (Fig. 1)shall be constant for all tests for a given intervertebral bodyfusion device.8.3 The stiffness of the device shall be determined accord-ing to Test Methods F2077. (Note that five new devices will beused for the subsidence test since Test Met
42、hods F2077 is adestructive test.)8.4 The intervertebral body fusion devices are also to beinserted into two prepared polyurethane blocks following themanufacturers suggested protocol for insertion of the implant(that is, the geometry of the implant configuration shall matchthat of in vivo conditions
43、). The initial intradiscal height, H,(Fig. 1) shall be constant for all tests for a given intervertebralbody fusion device.8.5 The load is to be applied to the intervertebral bodyfusion devices on coordinates (0, 0, Z) as described in 6.3 at arate of 0.1 mm/s.8.6 The load-displacement curves shall b
44、e recorded. Theyield load (N), and stiffness (N/mm) for both testing conditions(see 8.1.1 and 8.1.2) are to be established. Fig. 3 showsrepresentative load-displacement curves for both testing con-ditions.8.7 By modeling the subsidence testing systems as twosprings in series, one can derive the rela
45、tionship between thestiffness of the intervertebral body fusion device and thestiffness of the polyurethane foam blocks (simulated vertebralbodies). The equation for Kp, the polyurethane foam test blockstiffness, is as follows:Kp 5KsKdKd 2 Ks(1)where:Kd = stiffness of the intervertebral body fusion
46、device(section 8.3), andKs = stiffness of the system (sections 8.4-8.6).8.8 Stiffness values for kd, ks as well as the value of Kp(N/mm) shall be recorded for each intervertebral body fusiondevice, and an average stiffness value for kd, ks, and Kp(N/mm) shall be established for each intervertebral b
47、ody fusiondevice. From Test Methods F2077, the average stiffness valueof the device, kd, shall also be recorded.9. Report9.1 The report should specify the intervertebral body fusiondevice assembly components, the intervertebral body fusiondevice assembly, the intended spinal location, and the number
48、sof specimens tested. Any pertinent information about thecomponents such as name, design, manufacturer, material, thepart number, lot number, size, and so forth shall be stated. Allinformation necessary to reproduce the assembly shall also beincluded. Prior usage of any specimen shall be documented.
49、9.2 Exact loading configurations for the testing apparatusshall be included. All deviations from the recommended testprocedures shall be reported, and all relevant testing param-eters must be stated.9.3 The report of this mechanical testing shall include acomplete description of all failures, modes of failure anddeformation of the test block assembly or test apparatus. Themechanical test report shall include all load-displacementcurves for both axial compression protocols delineated in thistest method.Atypical load-displacement curve for the interv
