1、Designation: F2777 10F2777 16Standard Test Method forEvaluating Knee Bearing (Tibial Insert) Endurance andDeformation Under High Flexion1This standard is issued under the fixed designation F2777; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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 standard specifies a test method for determining the endurance properties and deformatio
3、n, under specified laboratoryconditions, of ultra high molecular weight polyethylene (UHMWPE) tibial bearing components used in bicompartmental ortricompartmental knee prosthesis designs.1.2 This test method is intended to simulate near posterior edge loading similar to the type of loading that woul
4、d occur duringhigh flexion motions such as squatting or kneeling.1.3 Although the methodology described attempts to identify physiological orientations and loading conditions, theinterpretation of results is limited to an in vitro comparison between knee prosthesis designs and their ability to resis
5、t deformationand fracture under stated test conditions.1.4 This test method applies to bearing components manufactured from UHMWPE.1.5 This test method could be adapted to address unicompartmental total knee replacement (TKR) systems, provided that thedesigns of the unicompartmental systems have suf
6、ficient constraint to allow use of this test method. This test method does notinclude instructions for testing two unicompartmental knees as a bicompartmental system.1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This
7、 standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.
8、1 ASTM Standards:2F1223 Test Method for Determination of Total Knee Replacement ConstraintF2003 Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in AirF2083 Specification for Knee Replacement Prosthesis2.2 Other Standards:3ISO 496549651 Axial Load Te
9、sting MachinesDynamic Force CalibrationStrain Gauge TechniqueMetallic materialsDynamic Force Calibration for uniaxial fatigue testing Part 1: Testing systemISO 5833 Implants for SurgeryAcrylic Resin Cements3. Terminology3.1 Definitions:3.1.1 anatomic (mechanical) axis of the femurthe line between th
10、e center of the femoral head and the center of the femoralknee.1 This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Sept. 15, 2010July 1, 2016.
11、Published October 2010August 2016. Originally approved in 2010. Last previous edition approved in 2010 asF277710. DOI: 10.1520/F2777-10.10.1520/F2777-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM St
12、andardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user
13、of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as p
14、ublished by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2 bearing centerlinethe line running anteroposterior that is the mirror line of the femoral articulating surface. Forasymme
15、tric bearing tibial tray designs, the appropriate tibial tray centerline shall be determined and reported along with therationale for the location.3.1.3 bearing retention mechanismmechanical means for preventing tibial tray/bearing disassociation.3.1.4 femoral component centerlinea line running ante
16、roposterior between the femoral condyles and parallel to the femoralcondyles. The line should be equidistant between the condyles. For asymmetric or non parallel non-parallel condyles designs, theappropriate centerline shall be determined, and the rationale for that location reported.3.1.5 fixed bea
17、ring systema knee prosthesis system comprised of a femoral component and a tibial component, where the tibialarticulating surface is not intended to move relative to the tibial tray.3.1.6 mobile bearingthe component between fixed femoral and tibial knee components with an articulating surface on bot
18、hthe inferior and superior sides.3.1.7 mobile bearing knee systema knee prosthesis system comprised of a femoral component, a tibial component, and amobile bearing component that can rotate and/or translate relative to the tibial component.3.1.8 posterior slopethe angle that the perpendicular axis o
19、f the tibial tray makes when it is tilted posteriorly away from thetibial axis (see Fig. 1).3.1.9 R valuethe ratio of the minimum force to the maximum force (that is, R = minimum force/maximum force).3.1.10 tibial axisnominal longitudinal axis of the tibia, which corresponds with the central axis of
20、 the medullary cavity of theproximal tibia.3.1.11 tibial tray/bearing disassociationunrecoverable physical separation of the tibial bearing and tibial tray components asa result of bearing distraction or tilting.3.1.12 tibial tray centerlinea line running anteroposterior that is the mirror line of t
21、he tibial articulating surface. Forasymmetric bearing tibial tray designs, the appropriate tibial tray centerline shall be determined and reported along with therationale for the location.4. Significance and Use4.1 This test method can be used to describe the effects of materials, manufacturing, and
22、 design variables on the fatigue/cycliccreep performance of UHMWPE bearing components subject to substantial rotation in the transverse planplane (relative to thetibial tray) for a relatively large number of cycles.4.2 The loading and kinematics of bearing component designs in vivo will, in general,
23、 differ from the loading and kinematicsdefined in this test method. The results obtained here cannot be used to directly predict in vivo performance. However, this testmethod is designed to enable comparisons between the fatigue performance of different bearing component designs when testedunder sim
24、ilar conditions.4.3 The test described is applicable to any bicompartmental knee design including mobile bearing knees that have mechanismsin the tibial articulating component to constrain the posterior movement of the femoral component and a built in built-in retentionmechanism to keep the articula
25、ting component on the tibial plate.FIG. 1 Incline of the TtibialTibial Tray Relative to the Tibial Axis at the Recommended Angle (Posterior Slope)F2777 1625. Apparatus and Materials5.1 Testing Machine, Testing machine, with the following characteristics:5.1.1 A sinusoidal, dynamic-forcing waveform.5
26、.1.2 An error in applied force not greater than62 % at the maximum force magnitude (in accordance with ISO 4965).49651).5.1.3 The axial Axial force peak representative of what could occur during daily activities of high flexion is a force of about2275 N.(about 2275 N). During the tests, the values o
27、f the maximum and minimum forces shall be maintained to an accuracy of62 % of the maximum force. The test shall be stopped if this accuracy is not maintained.5.1.4 The forcing accuracy must be maintained as bearing component deformation occurs.5.1.5 Instrumentation to record the number of cycles.5.2
28、 Fixturing:Fixturing, with the following characteristics:5.2.1 Means of mounting and enclosing the test specimens using a corrosion-resistant material that is capable of holding thefemoral component and tibial tray.5.2.2 The fixtures shall maintain the tibial and femoral components in their required
29、 orientations for the duration of the test.5.2.3 If necessary, bone cement (see ISO 5833) or a high-strength epoxy may be used to lock the femoral and tibial componentsin their fixtures.5.2.4 The test apparatus or fixture should allow the force to be applied through the center of the femoral compone
30、nt and ensureequal force transmission through the medial and lateral condyles.5.3 Fluid Medium:5.3.1 The test assembly shall be immersed in deionized water at 37 6 2C.5.3.2 Water Deionized water should be added as necessary to keep the test components at the test temperature for the durationof the t
31、est.6. Specimen Selection6.1 The metallic components shall follow the complete manufacturing process (machining, surface treatment, laser marking,passivation, cleaning, and so forth) until the sterilization stage. Because sterilization has no known effect on the mechanicalproperties for metallic com
32、ponents, it is not necessary for these to be sterilized. Unlike the metal components, the The UHMWPEcomponents shall be sterilized in a manner consistent with the clinical use for such devices, as this may affect the mechanicalproperties of the material.6.2 The UHMWPE component(s) shall be artificia
33、lly aged according to Practice F2003, except when the mechanical propertiesof the UHMWPE have been proven not to be detrimentally affected by aging.6.3 Most of the knee systems allow the tibial tray to be upsized, size for size, or downsized relative to the bearing componentsize. Consistent with the
34、 principle of this test method, the smallest tibial tray compatible with a given bearing component size(according to the manufacturer) shall be used.6.4 There may be some small variation in the amount of cold flow of the bearing component depending on the tibial bearingthickness. However, the possib
35、le effect of the cold flow is the worst on the thinnest bearing components. Consequently, the thinnestbearing component in the knee system scope shall be used in this test.7. Procedure7.1 On one representative sample, make the initial measurements on the bearing surface to characterize the subsequen
36、t amountof bearing deformation after completion of the test. Use of a Coordinate Measuring Machine (CMM) is the recommended methodof making the measurements. The measurements should be in the form of a grid of points, referenced to a fixed plane on theUHMWPE bearing, 1.5 mm apart over the entire sup
37、erior surface of the UHMWPE bearing. The measurements should be madewith the bearing at 20 6 2C.7.2 On one representative sample, perform the “A-P Draw Test” (Section 9.2) and the “Rotary Laxity Test” (Section 9.4) fromTest Method F1223 at the same flexion angle used in 7.6 of this test method.7.3 T
38、he Condition the UHMWPE bearing shall be conditioned in a deionized water environment at 37 6 2C prior to initiationof the test for a long enough time to bring the bearing into equilibrium with the fluid temperature.7.4 Mount the tibial tray in the test machine. The main proximal planar surface shal
39、l be inclined at the posterior sloperecommended by the manufacturer (see Fig. 1). If more than one slope is recommended, the largest slope should be used. Mountthe bearing component on the tibial tray using the method recommended by the manufacturer.NOTE 1The tibial slope will generate a shear force
40、 and a resulting bending moment on the test frame actuator. This may cause a significant errorof the load cell, depending on the sensitivity of the load cell to off axis off-axis loading. This should be addressed in the test setup.7.5 Measure vertical distraction (when appropriate for the design) an
41、d bearing tilt (Fig. 2).F2777 1637.5.1 To measure the vertical distraction, use appropriately-sized appropriately sized feeler gauges, one set under each condyleto lift the bearing away from the tibial plate, keeping the posterior surface of the bearing parallel to the superior surface of the tibial
42、plate, until the gauges will not fit easily in the gap. The thickness of the feeler gauges is the vertical distraction value.7.5.2 To measure the posterior bearing tilt displacement, push the bearing posteriorly and raise the posterior edge of the bearingby hand. Select a location on the posterior e
43、dge of the bearing and measure the perpendicular distance from that location to thetibial plate. Change in these displacements after testing may be useful as an indicator of damage.7.6 Mount the femoral component in the test machine with an alignment such that the component is flexed in the sagittal
44、 planeat the maximum flexion angle (including the posterior slope angle) the manufacturer recommends (see Fig. 3) according to themethod in Section 6.1.36.2.3 of Specification F2083.7.7 The femoral component should be placed so that it contacts the bearing component close to the posterior edge of th
45、e bearing.The specific contact points between components should be recorded and justified.At minimum, it should be demonstrated that theanterior-posterior placement of the components would permit flexion and rotation of the femur to the prescribed angles withoutimpingement between the femur and tibi
46、a.NOTE 2If the mobile bearing knee design allows anterior-posterior translation of the mobile bearing, translate the bearing component posteriorlyFIG. 2 Vertical Distraction and Posterior Bearing Tilt DisplacementFIG. 3 Rotate the Femoral Component until the Maximum Flexion Angle is ReachedF2777 164
47、relative to the tibial tray (according to the maximum translation allowed by the knee system) to simulate a worst-case condition.7.8 Initially align the all components in neutral rotation to set the maximum flexion angle. In this position, the femoralcomponent, the bearing component and the tibial t
48、ray anterior-posterior centerlines are coplanar should be aligned in the coronalplane according to the manufacturers intended neutral alignment (see Fig. 4).7.9 Rotational Alignment:7.9.1 For mobile bearing knee system designs simulate 20 of internal rotation for the tibial tray with respect to the
49、femoral andbearing components (see Fig. 5).NOTE 3The femoral component and the anteroposterior centerlines of the bearing component are still collinear.7.9.2 For fixed designs, the components should simulate 20 of internal rotation for the tibia tray with respect to the femoralcomponent. component (see Fig. 6). If a smaller angle is used, it shall be justified (see justified. Fig. 6). On a fixed bearing system,only one femoral condyle shall be at the maximum posterior contact point after the internal rotation is simulated. The other condyleshall be
