1、Designation: F1798 13Standard Test Method forEvaluating the Static and Fatigue Properties ofInterconnection Mechanisms and Subassemblies Used inSpinal Arthrodesis Implants1This standard is issued under the fixed designation F1798; the number immediately following the designation indicates the year o
2、foriginal 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 covers the measurement of uniaxialstatic
3、and fatigue strength, and resistance to loosening of thecomponent interconnection mechanisms of spinal arthrodesisimplants.1.2 The purpose of this test method is to provide a means ofmechanically characterizing different designs of spinal implantinterconnections. Ultimately, the various components a
4、nd in-terconnections should be combined for static and fatiguetesting of the spinal implant construct. It is not the intention ofthis test method to address the analysis of spinal implantconstructs or subconstructs or to define levels of performanceof spinal implants as insufficient knowledge is ava
5、ilable topredict the consequences of the use of particular spinal implantdesigns.1.3 This test method sets out definitions for use in measur-ing the strength of component interconnections of spinalimplants, possible test methods themselves, and the reportingof test results.1.4 The values stated in S
6、I units are to be regarded asstandard, with the exception of angular measurements, whichmay be reported in terms of either degrees or radians.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard
7、 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:2E4 Practices for Force Verification of Testing MachinesF383 Practice for Static Bend and Torsion Testing of In-tramedullary Rods (
8、Withdrawn 1996)3F1582 Terminology Relating to Spinal Implants3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 active length of longitudinal elementthe span be-tween rigid supports (for example, 50 mm is the active lengthin Fig. 1, Fig. 2, Fig. 3(a), Fig. 3(b), and Fig. 4.3.1.2
9、global coordinate systemspinal column motion hassix degrees of freedom, having translational motion along, androtational motion about three axes. The axes are labeledanterior-posterior or a-p (X), medial-lateral or transverse (Y),and caudal-cranial or axial (Z). This coordinate system is righthanded
10、 with +X in the anterior direction, +Y towards the leftside of the body, and +Z in the cranial direction. Positiverotations are defined by the right hand rule (see Fig. 5(a).3.1.3 gripping capacitythe maximum applied load ormoment across an interconnection mechanism within the first1.5 mm of permane
11、nt displacement or 5 of permanent rotationbetween the connected components.3.1.4 local coordinate systemthe spines global coordinatesystem shall be applied locally at the position of the intercon-nection. The local direction, z, shall be centered through thelongitudinal element of the x-y plane. The
12、 local direction, x,shall be defined as parallel to the axis of a screw or back of ahook. The local transverse axis, y, shall be parallel to atransverse element (See Fig. 5(b) and Fig. 5(c).3.1.5 loosening torquethe torque required to disconnectthe various threaded fasteners that might comprise the
13、im-plants interconnection mechanism.3.1.6 major directions of loadingdirections of the pre-dominant forces and moments (relative to the local axes) towhich vertebral connection elements are subjected, (that is,axial load, Fz; A-P load, Fx; axial torsion, Mz; and flexion-extension moment, My).1This t
14、est method is under the jurisdiction of ASTM Committee F04 onMedicaland Surgical Materials and Devices.Current edition approved Dec. 1, 2013. Published February 2014. Originallyapproved in 1997. Last previous edition approved in 2008 as F1798 97(2008).DOI: 10.1520/F1798-13.2For referenced ASTM stand
15、ards, 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.3The last approved version of this historical standard is referenced onwww.astm.org.Cop
16、yright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.7 maximum run out load/momentthe maximum loador moment that can be applied to a subassembly where all thetested constructs have withstood 2.5 106 cycles without afailure.3.1.8 relevant
17、directions of loadingthose directions ofloading in which a particular component interconnection isdesigned to provide resistance to loading. For example, aparticular spinal hook may be designed to withstand a positiveaxial load, A-P load, and flexion-extension moment, but not anegative axial load or
18、 axial torsion. Hence, positive axial load,A-P load, and flexion-extension moment are the relevantdirections of loading.3.1.9 spinal arthrodesis implantan implant applied to thespine with the intention of providing temporary correction andstability to vertebrae while bony fusion occurs.3.1.10 subass
19、embly failurepermanent deformation result-ing from fracture, plastic deformation, loosening or slippagethat renders the subassembly ineffective or unable to ad-equately resist load.3.1.11 subassembly permanent deformationthe displace-ment (mm) or angular displacement (degree of the subassem-bly rela
20、tive to the unloaded condition) remaining after theapplied load moment or torque has been removed. Care mustbe taken to ensure that the loading fixtures are rigid and do notcontribute to the measurement of deflection.3.1.12 tightening torquethe specified torque that is ap-plied to the various thread
21、ed fasteners that might comprise theimplants interconnection mechanism.3.1.13 ultimate load/moment of the subassemblymaximum load or moment applied to a subassembly (see PointEinFig. 6).3.1.14 yield load/moment of the subassemblythe load ormoment required to produce a permanent deformation equal to0
22、.020 times the active length of the longitudinal element (seePoint D in Fig. 6).4. Summary of Test Methods4.1 Vertebral attachment components (for example, hook,screws, bands) and transverse elements must be attached tolongitudinal elements (for example, rods, plates) to form spinalimplant subassemb
23、lies.4.2 The interconnections are tested only in the relevantdirections of loading by applying loads at specific locationsrelative to the local coordinate system.4.3 The interconnections and subassemblies are tested stati-cally in a load-to-failure mode and also can be tested cyclicallyto estimate t
24、he maximum run out value at 2.5 106cycles.5. Significance and Use5.1 Spinal implants are generally composed of severalcomponents that, when connected together, form a spinalimplant construct. Spinal implant constructs are designed toprovide some stability to the spine while arthrodesis takesplace. T
25、his test method outlines standardized evaluations ofdifferent interconnection mechanisms to facilitate comparisonbetween different designs. Comparisons must be made cau-tiously and with careful analysis, taking into account the effectsthat design differences can have on the loading configurations.5.
26、2 This test method is used to quantify the static andfatigue properties of different implant interconnection designs.The mechanical tests are conducted in vitro using simplified,unidirectional loads and moments. Fatigue testing in a simu-lated body fluid or saline may have a fretting, corrosive, orl
27、ubricating effect on the interconnection and thereby affect therelative performance of tested devices. Hence, the testenvironment, whether a simulated body fluid, saline (9g NaClper 1000 mL H2O), with a saline drip, or dry, is an importantcharacteristic of the test and must be reported accurately.5.
28、3 The loading of spinal implant constructs in vivo will, ingeneral, differ from the loading configurations used in this testmethod. The results obtained here cannot be used directly toFIG. 1 A-P Test Apparatus for SubassemblyFIG. 2 Transverse Test Apparatus for SubassemblyF1798 132FIG.3Flexion-Exten
29、sionMomentTestApparatusforSubassemblyF1798 133predict in vivo performance. However, the results can be usedto compare different component designs in terms of relativemechanical parameters.6. Apparatus6.1 Machines used for the test shall conform to the require-ments of Practices E4.6.2 The apparatus
30、for axial (z) gripping capacity measure-ments of an interconnection mechanism is depicted in Fig.7(a). One end of the longitudinal element shall be clampedrigidly, leaving 5 mm exposed between the interconnectionmechanism and the test machine base.Asection of longitudinalelement at least 5 mm shall
31、extend beyond the interconnectionlinkage and remain unfixed. Axial loads are applied to theinterconnection mechanism along the axis of the longitudinalelement via a sleeve (collar) which freely surrounds thelongitudinal element. The sleeve (collar) should evenly distrib-ute the load around the inter
32、connection. An alternate method,depicted in Fig. 7(b), applies the load to the longitudinalelement and pushes it through the interconnection clamp.6.3 The apparatus forA-P(x) mechanical property measure-ments of a subassembly is depicted in Fig. 1. Both ends of thelongitudinal element shall be clamp
33、ed rigidly, with the inter-connection centered on a 50-mm section of the longitudinalelement. The local origin of the interconnection mechanismshall be centered between the mounts. Loads are applied to theFIG. 4 Transverse Moment Test Apparatus for SubassemblyF1798 134FIG. 5 Coordinate SystemF1798 1
34、35interconnection (perpendicular to the longitudinal element) viaa clamp on the hook, screw, or band. The load should becentered through the local x coordinate axis.6.4 The apparatus for transverse (y) mechanical propertymeasurements of a subassembly is depicted in Fig. 2. Bothends of the longitudin
35、al element shall be clamped rigidly, withthe interconnection centered on a 50-mm section of thelongitudinal element. The local origin of the interconnectionmechanism shall be centered between the mounts. Loads areapplied to the interconnection (perpendicular to the longitudi-nal element) via a clamp
36、 on the transverse connector. The loadshould be centered through the local y coordinate axis.6.5 The apparatus for flexion-extension moment (My) me-chanical property measurements of a subassembly is depictedin Fig. 3. Both ends of the longitudinal element shall beclamped rigidly, with the interconne
37、ction centered on a 50-mmFIG. 6 Load/Displacement CurveF1798 136section of the longitudinal element. The local origin of theinterconnection mechanism shall be centered between themounts. Loads are applied to the interconnection (parallel tothe longitudinal element). For spinal hooks, the load shall
38、beapplied via a cylinder set in the hook notch (see Fig. 3(a). Forother elements (screws) the load shall be applied 25 mm fromthe local z axis (see Fig. 3(b).6.6 The apparatus for transverse moment (Mx) mechanicalproperty measurements of a subassembly is depicted in Fig. 4.As in the previous test, 6
39、.5, both ends of the longitudinalelement shall be clamped rigidly, with the interconnectioncentered on a 50-mm section of the longitudinal element. Thelocal origin of the interconnection mechanism shall be centeredbetween the mounts. Loads are applied to the interconnection(parallel to the longitudi
40、nal element), 25 mm from the z axis.6.7 The apparatus for axial torque (Mz) gripping capacitymeasurements of an interconnection mechanism is depicted inFig. 8(a) and is similar to that described in 6.2 with theexception that the axial torque is applied via notches in thesleeve that surrounds the lon
41、gitudinal element. An alternativemethod is to hold the interconnection rigidly and apply thetorsional force to the longitudinal element as shown in Fig.8(b). A third alternative is to apply the torque via a forceapplied to a moment arm as shown in Fig. 8(c), but thisalternative may introduce an addi
42、tional variable of bending ofthe anchor component. In any case, care must be taken toevaluate and minimize the effect of the torsional properties ofthe longitudinal element on the results.7. Sampling7.1 The samples tested shall be previously unused parts, andshall not be re-tested.7.2 The test const
43、ructs shall be labeled and maintainedaccording to good laboratory practice.7.3 Static tests of mechanical properties should have aminimum sample size of five.7.4 Fatigue tests for determining the maximum run out loador moment of a subassembly at 2.5 106cycles shall utilize arun down, half-interval a
44、pproach4with one specimen per rundown interval or half-interval and three consecutive specimensshowing run out to 2.5 106cycles. Alternative methods fordetermining the starting point of the fatigue curve are therun-up method or choosing 75 % of the ultimate static load ormoment.8. Procedure for Meas
45、uring Static Mechanical Properties8.1 Measure the tightening torques for any set screws ornuts which are incorporated into the interconnection linkage.8.2 Apply all tightening, crimping, or locking mechanismsas specified by the manufacturer.8.3 The recommended maximum rate for applying a load is20 N
46、/s (or 25 mm/min) and is 25 N-m/min (or 25 /min) forapplying a moment or torque. Since rate is machine- andsoftware-dependent, it may be necessary to run the tests slowerto achieve accurate data.8.4 StaticA-Pload (Fx), transverse load (Fy), axial grippingcapacity (Fz), and transverse moment (Mx), fl
47、exion-extensionmoment (My), and axial torque (Mz) shall be measured usingthe apparatus described in 6.1 6.7.4“Optiminal Stress Amplitude Selection in Estimating Median Fatigue LimitsUsing Small Samples”, Little, R.E., ed., J. of Testing and Evaluation, ASTM, 1990,pp. 115122.FIG. 7 Axial Gripping Cap
48、acity Test ApparatusF1798 137FIG. 8 Axial Torque Gripping Capacity Test ApparatusF1798 1388.5 Loads and moments need to be measured only in therelevant directions of loading.8.6 After each load or moment measurement, looseningtorque shall be measured (if applicable).9. Procedure for the Measurement
49、of Fatigue Run Out9.1 Measure the tightening torques for any set screws ornuts that are incorporated into the connection linkage.9.2 Apply all tightening, crimping, or locking mechanismsas specified by the manufacturer.9.3 The maximum frequency of cyclic loading is not speci-fied but shall be measured and reported.9.4 All fatigue loading should be sinusoidal, accomplishedvia continuous load amplitude control, rather than in a con-trolled deflection manner.9.5 A-Pfatigue run out (Fx), transverse fatigue run out (Fy),axial fatigue run out
