1、Designation: F 1800 07Standard Test Method forCyclic Fatigue Testing of Metal Tibial Tray Components ofTotal Knee Joint Replacements1This standard is issued under the fixed designation F 1800; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、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 covers a procedure for the fatiguetesting of metallic tibial trays used in kne
3、e joint replacements.This test method covers the procedures for the performance offatigue tests on metallic tibial components using a cyclic,constant-amplitude force. It applies to tibial trays which coverboth the medial and lateral plateaus of the tibia. This testmethod may require modifications to
4、 accommodate other tibialtray designs.1.2 This test method is intended to provide useful, consis-tent, and reproducible information about the fatigue perfor-mance of metallic tibial trays with one unsupported condyle.1.3 The values stated in SI units are regarded as thestandard. The inch-pound units
5、 given in parentheses are forinformation only.1.4 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 to establish appro-priate safety and health practices and determine the applica-bility of regul
6、atory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 4 Practices for Force Verification of Testing MachinesE 467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing SystemE 468 Practice for Presentation of Constant Amplitude Fa-tigue Tes
7、t Results for Metallic MaterialsE 1150 Definitions of Terms Relating to Fatigue3. Terminology3.1 Definitions:3.1.1 R valueThe R value is the ratio of the minimum loadto the maximum load.R 5minimum loadmaximum load(1)3.2 Definitions of Terms Specific to This Standard:3.2.1 anteroposterior centerlinea
8、 line that passes throughthe center of the tibial tray, parallel to the sagittal plane andperpendicular to the line of load application. For asymmetrictibial tray designs, the appropriate center of the tibial tray shallbe determined by the investigator and the rationale reported.3.2.2 fixture center
9、linea line that passes through thecenter of the fixture, parallel to the anteroposterior centerline.This line represents the separation between the supported andunsupported portions of the test fixture.3.2.3 mediolateral centerlinea line that passes throughthe center of the tibial tray, parallel to
10、the coronal, or frontal,plane and perpendicular to the line of load application. Forasymmetric tibial tray designs, the appropriate center of thetibial tray shall be determined by the investigator and therationale reported.3.2.4 moment arm, dapthe perpendicular distance betweenthe mediolateral cente
11、rline of the tibia component and the lineof load application.3.2.5 moment arm, dmlthe perpendicular distance betweenthe anteroposterior centerline of the tibia component and theline of load application.4. Significance and Use4.1 This test method can be used to describe the effects ofmaterials, manuf
12、acturing, and design variables on the fatigueperformance of metallic tibial trays subject to cyclic loadingfor relatively large numbers of cycles.4.2 The loading of tibial tray designs in vivo will, in general,differ from the loading defined in this test method. The resultsobtained here cannot be us
13、ed to directly predict in vivoperformance. However, this test method is designed to allow1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Sept
14、. 15, 2007. Published October 2007. Originallyapproved in 1997. Last previous edition approved in 2004 as F 1800 04.2For 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
15、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.for comparisons between the fatigue performance of differentmetallic tibial tray designs, when tested under similar condi-tions.4.
16、3 In order for fatigue data on tibial trays to be comparable,reproducible, and capable of being correlated among laborato-ries, it is essential that uniform procedures be established.5. Specimen Selection5.1 The test component selected shall have the same geom-etry as the final product, and shall be
17、 in finished condition.6. Apparatus6.1 The tibial tray shall be mounted as a cantilever beam(see Fig. 1 and Fig. 2). Care shall be taken to ensure that thefixation of the tibial tray does not produce abnormal stressconcentrations that could change the failure mode of the part.One possible setup invo
18、lving fixation of the inferior surface orclamping of the superior surface is shown in Fig. 1 and Fig. 2.If necessary, bone cement or other high strength epoxy may beused on the supported aspect of the tibial tray to preventloosening during the test.6.2 The tibial tray shall be positioned such that t
19、he antero-posterior centerline and the fixture centerline are aligned withan accuracy of 61mminthex direction and 62 in the xyplane (see Fig. 1 and Fig. 2).6.3 When the tibial tray design includes a central keel orother prominence, the proper method for support of the keelmust be determined. Dependi
20、ng on the tibial tray design, it maybe necessary to evaluate the design with or without support ofthe keel (see Fig. 2). The method of supporting (or notsupporting) any such feature shall be reported.6.4 A spacer of plastic possessing sufficient stiffness andcreep resistance (for example, ultra high
21、 molecular weightpolyethylene, acetal co-polymer) shall be placed between thetibial tray and the load applicator (see Fig. 3). The spacer shallcontain a spherical indentation (or recess) for the sphericalindenter. This recess shall be greater to or equal than thediameter of the spherical indenter an
22、d is included to minimizethe chance of spacer fracture under load. The spacer shall havea minimum thickness of 6 mm (0.25 in.), measured at the domeof the sphere. It is recommended that the diameter of the spaceris 13 mm (0.5 in.).NOTE 1Actual dimensions of the spacer may vary as smaller tibialtray
23、designs may require a smaller diameter disk.6.4.1 The spacer shall be placed on the unsupported tibialcondyle. The purpose of the spacer is to distribute load to thetibial tray condyle and to eliminate possible fretting fatigueinitiated by contact between the metal indenter and the tibialtray.6.5 Th
24、e fixturing shall be constructed so that the load shallbe applied perpendicular to the undeflected superior surface ofthe tibial tray.6.6 Use one of the following two methods for determiningthe position of the loading point.FIG. 1 Schematic of Test Setup Without a Central KeelF18000726.6.1 For tibia
25、l articulating surface designs that have aconcave surface, the loading point shall be the intersection withthe tray of a line perpendicular to the tray which intersects thedeepest part of the concave recess of the articulating surface ofthe tibial component.6.6.2 For other tibial designs, the femora
26、l component, thetibial articulating surface, and the tibial tray shall be assembledat 0 flexion and the position of the center of pressuredetermined. The loading point shall be the intersection of theline perpendicular to the tray which intersects the center of thepressure contact area.NOTE 2Optiona
27、lly, define the worst-case scenario considering thepotential translation in the transverse plane and/or the potential axialFIG. 2 Schematic or Test Setup With a Central KeelFIG. 3 Recommended Spacer DrawingF1800073rotation (1)3of the femoral component relative to the tibial baseplate, andapply 6.6.1
28、 or 6.6.2. The rationale for the choice of femoral componentplacement relative to the tibial baseplate should be reported.NOTE 3If the geometry of the tibial baseplate superior surfaceprevents using and dapand dmlfor the load application (for example, thepresence of protrusion at the location of the
29、 theoretical load application),the rationale for the choice of the appropriate load location should bereported (X1.6 is an example of the variation that could occur due to tibialbaseplate misalignment).6.6.3 The dapand the dmlshall be determined from either ofthe above techniques and will be used fo
30、r all testing of thatdesign in that size.6.7 The load shall be applied by means of a sphericalindenter, a diameter of 32 mm (1.25 in.) is recommended.7. Equipment Characteristics7.1 Perform the tests on a fatigue test machine with ad-equate load capacity.7.2 Analyze the action of the machine to ensu
31、re that thedesired form and periodic force amplitude is maintained for theduration of the test (see Practice E 467 or use a validated straingaged part).7.3 The test machine shall have a load monitoring systemsuch as the transducer mounted in line with the specimen.Monitor the test loads continuously
32、 in the early stages of thetest and periodically thereafter to ensure the desired load cycleis maintained. Maintain the varying load as determined bysuitable dynamic verification at all times to within 62 % of thelargest compressive force being used.8. Procedure8.1 Determine the size of the tibial t
33、ray component used bythe investigator. Dimensions shall be reported.8.2 Position the test specimen such that the load axis isperpendicular to the undeflected superior surface of the traysince the tray surface will not remain perpendicular to the loadaxis during loading.8.3 Mount one side of a symmet
34、ric tibial component on thefixture (see Fig. 1 and Fig. 2). Use the centerline of the tray todistinguish between supported and non supported sides. Ifasymmetrical, fix the tibial component such that a worst casecondition is tested. Report the criteria used to distinguishbetween supported and not sup
35、ported sides.8.4 Apply the load by means of a spherical indenter.8.5 Test frequencyRun all tests at a frequency of 30 Hz orless. Take care to ensure that the test machine can maintain theapplied load at the chosen frequency and that resonant condi-tions are not reached.8.6 R valueRun all tests with
36、an R value of 10.0.NOTE 4In strict terms, since the force applied to the tray is compres-sive, the maximum force is the smallest negative amplitude. Conse-quently, the R value is ten when the negative signs cancel each other. Interms of applied bending moment at the cantilever plane, the R valuewoul
37、d be 0.1. See Terminology E 1150 for the definition of the R value.8.7 Measure the vertical deflection of the tibial tray using adial gage, displacement transducer, and so forth. Record thepoint at which the deflection is measured (that is, under theapplied load, at the point of maximum deflection).
38、8.8 Report the test environment used.9. Test Termination9.1 Continue the test until the tibial tray fails or until apredetermined number of cycles has been applied to theimplant. The suggested number of cycles is ten million. Failuremay be defined as: a fracture of the tibial tray; formation of acra
39、ck detectable by eye, fluorescent dye penetrant, or othernon-destructive means; or exceeding a predetermined deflec-tion limit.10. Report10.1 Report the fatigue test specimens, procedures, andresults in accordance with Practice E 468.10.2 In addition, report the following parameters: tibial traymate
40、rial, spacer diameter and thickness, indenter diameter,overall anteroposterior and mediolateral dimensions of the tray,location of anteroposterior and mediolateral centerlines (forasymmetric tibial trays), tibial condyle loaded (for asymmetrictibial trays), dml, dap, fixation method, largest compres
41、siveload, R value, cycles to failure, mode and location of failures,test environment, and test frequency. The method for determin-ing the loading location on the tibial tray (that is, dml, and dap)shall be documented.11. Precision and Bias11.1 The precision and bias of this test method needs to bees
42、tablished. Test results that can be used to establish precisionand bias are solicited.12. Keywords12.1 arthroplasty; orthopaedic medical devices; tibial com-ponents; total knee arthroplasty3The boldface numbers given in parentheses refer to a list of references at theend of the test.F1800074APPENDIX
43、(Nonmandatory Information)X1. RATIONALEX1.1 Fractures of tibial trays in TKR have occurred inclinical applications (2-6). The tray design, quality of bone,and other features contribute to implant fracture. One recog-nizable mode of clinical failure occurs when the lateral portionof the tray is firml
44、y anchored while bone support of the medialcondyle is absent. As the body loads are applied through thetray of the prosthesis, significant stresses can result at the areawhere the tray is still firmly supported. Because it is believedthat this lack of support is the primary reason behind fractureof
45、the tibial trays, this test method was chosen as a simplifiedmodel to use in fatigue testing of actual implants.X1.2 It is recognized that for some materials the environ-ment may have an effect on the response to cyclic loading. Thetest environment used and the rationale for that choice shall bedesc
46、ribed in the test report.X1.3 It is also recognized that actual in vivo loadingconditions are not constant amplitude. However, there isinsufficient information available to create standard load spec-trums for metallic tibial components. Accordingly, a simpleperiodic constant amplitude force is recom
47、mended.X1.4 Worst case loading of the tibial tray may varydepending on material, design, and clinical indications. Theresearcher shall evaluate the possible clinical and designrelated failure modes and attempt to determine a worst casesituation.As stated above, loss of medial bone support has beencl
48、inically and is thus incorporated in this test method. Addi-tional factor that may be of importance include wear that hasbeen reported in the posterior medial region of the tibia (7).Also, as the method of heat treatment can affect the strength ofthe tibial tray material, it shall be considered. For
49、 example, thehigh temperature sintering treatment used to apply a porouscoating to a tibial tray may affect the fatigue strength of thetibial tray.X1.5 The size of tibial tray to be tested shall be determinedby the investigator. In general, the worst case size shall bechosen based on evaluation or experience, or both. In a designwith a constant tray thickness, maximizing the dmlwill result inthe largest moment arm and therefore the highest stresses in thetray; however, a tray of non-uniform thickness may not adhereto this rule. There may also be a reason why an invest
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