1、Designation: F 2267 04Standard Test Method forMeasuring Load Induced Subsidence of Intervertebral BodyFusion Device Under Static Axial Compression1This standard is issued under the fixed designation F 2267; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, 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 specifies the materials and methods forthe axial compressive sub
3、sidence testing of non-biologic inter-vertebral 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 intervertebral body fusio
4、n 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 type and a specifi
5、c 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 UnitsThe values stated i
6、n SI units are to be regardedas the standard with the exception of angular measurements,which may be reported in terms of either degrees or radians.1.6 Since some intervertebral body fusion devices requirethe use of additional implants for stabilization, the testing ofthese types of implants may not
7、 be in accordance with themanufacturers recommended usage.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 user of this stan
8、dardto establish appropriate safety and health practices anddetermine the applicability of regulatory limitations prior touse.2. Referenced Documents2.1 ASTM Standards:2E 4 Practices for Force Verification of Testing MachinesF 1582 Terminology Related to Spinal ImplantsF 1839 Specification for Rigid
9、 Polyurethane Foam for Useas a Standard Material for Testing Orthopaedic Devicesand InstrumentsF 2077 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 Definitions:3.2
10、.1 coordinate system/axesthree orthogonal axes aredefined by Terminology F 1582 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 X in thean
11、terior 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 applicatio
12、nintervertebral 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 for the inte
13、rvertebral 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 existdifferent anatomical surgical approaches, which will result indifferent implant orientation at
14、 different levels of the spine.1This test method is 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 Apr. 1, 2004. Published April 2004. Originallyapproved in 20
15、03. Last previous edition approved in 2003 as F 2267 03.2For 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 Document Summary page onthe ASTM website.1Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.5 intervertebral subsidencethe process of a vertebralbody cavitating or sinking around an implanted intervertebralbody fusion device resulting in the loss of intradiscal height.3.2.6 int
17、radiscal 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 BlocksF22670423.2.7 load pointthe point throug
18、h 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 thoracicdevices, and 2 mm for lumbar devices (see distanc
19、e 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 Fig. 2).3.2.11 test block heightthe linear dis
20、tance 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 forlumbar, thoracic, and cervical intervertebral
21、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 found by plottingline BC with stiffness, K, ori
22、ginating 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 axial compressive subsidence testing of the
23、inter-vertebral body fusion device will be conducted in a simulatedmotion segment via a gap between two polyurethane foamblocks.4.3 Grade 15 foam shall be employed conforming to Speci-fication F 1839.5. Significance and Use5.1 Intervertebral body fusion devices are generally simplegeometric shaped d
24、evices, 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 designs of intervertebral body fusionFIG. 3 Typical
25、Load-Displacement Plot Comparison for Test Specimens in Metallic and Polyurethane Test BlocksF2267043devices since this is a potential clinical failure mode. Thesetests are conducted in vitro in order to simplify the comparisonof simulated vertebral body subsidence induced by the inter-vertebral bod
26、y 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 used to directly predictin vivo performance. The results,
27、 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 intervertebral body fusion device with respect tothe loading axi
28、s will be dependent upon the design andmanufacturers recommendation for implant placement.6. Apparatus6.1 Test machines will conform to the requirements ofPractices E 4.6.2 The intradiscal height, H, (Fig. 1) shall be determinedfrom vertebral body and disc morphometric data at the in-tended level of
29、 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.6.3 Axial Compressive Testing ApparatusAn exampleaxia
30、l 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 socket joint or universal joint (that is, unconstraine
31、d 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 the basesocket so that no rotation occurs. The hollow p
32、ushrod 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 sphere joint (the geometric center of the device beingtest
33、ed). 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 theintervertebral device is initially coincident with the pushro
34、dsaxis 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 tominimize deviation of the pushrods axis (direction of appli
35、edforce, 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 intervertebralbody fusion device. For example,a1mmdispl
36、acement of thespherical surfaces center in the XY plane would produce anFIG. 4 Subsidence Test FixtureF2267044angle between axes of 0.15, (10 mm producing 1.5). Figs. 4and 5 are schematics of this test set up.7. Sampling7.1 Implants may be retested provided that the tested devicehas undergone a micr
37、oscopic 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 blocks) shall be labeled and shall bemaintained according to
38、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 normally be used clinically.8. Procedure for Static Axial Compres
39、sion 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.FIG. 5 Subsidence Test FixtureF22670458.1.2 Polyurethane blocks will be used to determine thedevices propensity to subside.8.2 The intervertebral
40、 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 vivo conditions). The initial intradiscal height, H, (Fig. 1)shall be c
41、onstant for all tests for a given intervertebral bodyfusion device.8.3 The stiffness of the device shall be determined accord-ing to Test Methods F 2077. (Note that five new devices will beused for the subsidence test since Test Methods F 2077 is adestructive test.)8.4 The intervertebral body fusion
42、 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). The initial intradiscal height, H,(Fig. 1) shall be constant for
43、 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 be recorded. Theyield load (N), and stiffness (N/mm) for both testin
44、g 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 relationship between thestiffness of the intervertebral body fusion dev
45、ice 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 device(section 8.3), andKs = stiffness of the system (sections 8.4-
46、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 body fusiondevice. From Test Methods F 2077, the average stiffness v
47、alueof 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 thecomponent
48、s 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.9.2 Exact loading configurations for the testing apparatusshall be
49、 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. A typical load-displacement curve for the inter-vertebral body fusion device tested with metallic blocks and inthe po
