1、Designation: F2267 04 (Reapproved 2018)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, health, and environmentalpractices and determine the applicability of regulatory limita-tions prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in th
9、e Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesF1582 Terminology Re
10、lating to Spinal ImplantsF1839 Specification for Rigid Polyurethane Foam for Use asa Standard Material for Testing Orthopaedic Devices andInstrumentsF2077 Test Methods for Intervertebral Body Fusion Devices3. Terminology3.1 All subsidence testing terminology is consistent with thereferenced standard
11、s above, unless otherwise stated.3.2 Definitions: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 longitu
12、dinal axis of the implant, with positive 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 installati
13、on instructions.3.2.3 intended method of 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 locationth
14、e anatomic region of thespine intended for the intervertebral body fusion device.Intervertebral body fusion devices may be designed anddeveloped for specific regions of the spine such as the lumbar,1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and
15、 Devicesand is the direct responsibility of SubcommitteeF04.25 on Spinal Devices.Current edition approved Feb. 1, 2018. Published April 2018. Originallyapproved in 2003. Last previous edition approved in 2011 as F2267 04(2011).DOI: 10.1520/F2267-04R18.2For referenced ASTM standards, visit the ASTM w
16、ebsite, 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United St
17、atesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to T
18、rade (TBT) Committee.1thoracic, and cervical spine. Also, there potentially existdifferent 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
19、implanted intervertebralbody fusion device resulting in the loss of intradiscal height.FIG. 1 Intradiscal Height DiagramFIG. 2 Typical Load-Displacement Curve with 1.5 mm (Thoracic Device) Offset for Polyurethane Foam Test BlocksF2267 04 (2018)23.2.6 intradiscal heightthe straight-line distance alon
20、g theZ-axis between the unaltered simulated vertebral bodies. SeeFig. 1.3.2.7 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
21、 to 1 mm for cervical disc devices, 1.5 mm for thoracicdevices, 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 o
22、f the load-displacement curve (see the slope of lineAE in Fig. 2).3.2.11 test block heightthe linear distance along the Z-axisfrom the top surface of the superior simulated vertebral body tothe bottom surface of the inferior simulated vertebral body withthe intervertebral body fusion device in posit
23、ion. The blockheights shall be 70 mm, 60 mm, and 40 mm for lumbar,thoracic, and cervical intervertebral disc devices respectively.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
24、 permanentdeformation equal to the offset displacement found 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 sp
25、ecific to the lumbar, thoracic, and cervicalspine.4.2 The 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 F18
26、39.5. Significance and Use5.1 Intervertebral body fusion devices are generally simplegeometric shaped devices, which are often porous or hollow inFIG. 3 Typical Load-Displacement Plot Comparison for Test Specimens in Metallic and Polyurethane Test BlocksF2267 04 (2018)3nature. Their function is to s
27、upport 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 designs of intervertebral body fusiondevices since this is a potential clinical failure mode. Thesetests are conducted in vit
28、ro in order to simplify the comparisonof simulated vertebral 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 t
29、herefore, theresults from this test method may not be used 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
30、 simulated vertebral bodies andposition of the intervertebral 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 h
31、eight, H, (Fig. 1) shall be determinedfrom vertebral body 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 intradisc
32、al height that is appropriate for the devicebeing tested.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
33、 connected to the pushrod by a minimal friction balland socket 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 thei
34、nferior polyurethane block and is rigidly fixed within the 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 axe
35、s and located at the center of the superiorfixtures sphere 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 testappara
36、tus will be assembled such that the Z-axis of theintervertebral 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 sphericalsurfa
37、ce is to be a minimum of 38 cm. This is required tominimize 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 loa
38、d, F,and is equal to the compressive force, Fz, on the intervertebralbody fusion device. For example,a1mmdisplacement of thespherical surfaces center in the XY plane would produce anFIG. 4 Subsidence Test FixtureF2267 04 (2018)4angle between axes of 0.15, (10 mm producing 1.5). Figs. 4and 5 are sche
39、matics of this test set up.7. Sampling7.1 Implants may be 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 (th
40、at is, intervertebral body fusiondevice and polyurethane 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
41、 should be prepared in the manner in whichthey would normally be used clinically.FIG. 5 Subsidence Test FixtureF2267 04 (2018)58. 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 d
42、evice being tested.8.1.2 Polyurethane blocks will be used to determine thedevices propensity to subside.8.2 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 geome
43、try of the implant configuration shall match thatof in vivo 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 d
44、evices will beused for the subsidence test since Test Methods 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 im
45、plant configuration shall matchthat of in vivo conditions). 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 a
46、rate of 0.1 mm/s.8.6 The load-displacement curves shall be 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
47、 systems as twosprings in series, one can derive the relationship 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(
48、1)where:Kd = stiffness of the intervertebral body fusion device (sec-tion 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,
49、and Kp(N/mm) shall be established for each intervertebral body 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 numbersof 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
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