ASTM_F_2723_-_13a.pdf

Designation:F272313aStandard Test Method forEvaluating Mobile Bearing Knee Tibial Baseplate/BearingResistance to Dynamic Disassociation1This standard is issued under the fixed designation F2723;the number immediately following the designation indicates the year oforiginal 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 describes a laboratory method forevaluating the potential for mobile bearing knee tibialbaseplate/bearing disassociation under repeated forces.1.2 The test described is applicable to any bicompartmentalmobile bearing knee with a bearing retention mechanism.Withmodification,the test can be applied to a unicompartmentalmobile bearing knee with a bearing retention mechanism.1.3 Although the methodology described does not replicateall physiological force conditions,it is a means of in vitrocomparison of mobile bearing knee designs and the strength ofthe bearing retention mechanism between the tibial baseplateand bearing components under the stated test conditions.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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 to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Terminology2.1 Definitions:2.1.1 bearing axisthe line connecting the lowest points onboth the lateral and medial condyles of the superior surface ofthe mobile bearing.2.1.2 bearing retention mechanismmechanical means pre-venting tibial baseplate/bearing disassociation.2.1.3 inferior articulating interfacesany interface inwhich relative motion occurs between the underside of themobile bearing component and the tibial tray.2.1.4 limiting positionthe position of the femoral compo-nent relative to the bearing at which the shear force is at amaximum with anterior-posterior(AP)movement of the femo-ral component on the bearing.2.1.5 mobile bearingthe component between fixed femo-ral and tibial knee components with an articulating surface onboth the inferior and superior sides.2.1.6 mobile bearing knee systema knee prosthesissystem,comprised of a tibial component,a mobile bearingcomponent that can rotate or rotate and translate relative to thetibial component,and a femoral component.2.1.7 superior articulating interfacesany interface inwhich relative motion occurs between the topside of the mobilebearing component and the femoral bearing component.2.1.8 tibial baseplate/bearing disassociation unrecover-able physical separation of the bearing and tibial baseplatecomponents as a result of bearing distraction or tilting.2.1.9 2-axis orthogonal load framea test machine capableof applying forces and displacements that act at 90 to eachother.3.Significance and Use3.1 This test method includes the use of static and fatigueshear and bending force conditions to evaluate the bearingretention mechanism of a mobile bearing knee design and itsability to prevent disassociation.3.2 In general,disassociation does not occur during activi-ties where the contact locations are within the boundaries of thebearing surfaces.Disassociation is most likely to occur withforces at the edges of the bearing component or with large APshear forces on a posterior stabilized knee tibial componentpost.Extreme bearing rotation,bone/bearing impingement,severe varus or valgus moments,high flexion or any combi-nation of the above can increase the likelihood of disassocia-tion.3.3 The test method described is applicable to any bicom-partmental mobile bearing knee with a bearing retentionmechanism.With modification,the test can be applied to aunicompartmental mobile bearing knee with a bearing reten-tion mechanism.1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved July 15,2013.Published August 2013.Originallyapproved in 2008.Last previous version approved in 2013 as F2723 13.DOI:10.1520/F2723-13A.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.Apparatus and Materials4.1 A2-axis orthogonal load frame with feedback control onboth axes be required for dislocation testing.The machine mustbe able to record force and displacement in both axes.4.1.1 Component SizeTest specimens should be chosen tomaximize the force on the bearing retention mechanism.Considerations should include bearing thickness(a thickerbearing would tend to increase the forces on the lockingmechanism,but could also increase the material support for thelocking mechanism),bearing profile/size and tibial baseplateprofile/