ASTM_F_2724_-_08_2014.pdf

Designation:F272408(Reapproved 2014)Standard Test Method forEvaluating Mobile Bearing Knee Dislocation1This standard is issued under the fixed designation F2724;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 is designed to provide a standardizedmethod to determine the dislocation resistance of mobile-bearing knee designs with regard to femoral componentdisassociation and spin-out/spit-out of the mobile bearinginsert.1.2 Although the methodology described does not replicateall physiological loading conditions,it is a means of in-vitrocomparison of mobile bearing knee designs and their ability toresist dislocation of the mobile bearing from the femoral ortibial components under stated test conditions.1.3 The test method applies only to mobile bearing totalknee designs.1.4 The values stated in SI units are regarded as standard.The values given in parentheses are mathematical conversionsto inch-pound units that are provided for information only andare not considered standard.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.Referenced Documents2.1 ASTM Standards:2F1223 Test Method for Determination of Total Knee Re-placement Constraint3.Terminology3.1 Definitions:3.1.1 bearing axis,nthe line connecting the lowest pointson both the lateral and medial condyles of the superior surfaceof the mobile bearing.3.1.2 centerline axis,na line through the neutral pointperpendicular to the bearing axis and in a plane parallel to theplane of the flat portion of the inferior articulating surface ofthe mobile bearing at 0 posterior tibial slope.3.1.3 mobile bearing(insert),nthe component betweenfixed femoral and tibial knee components with an articulatingsurface on both the inferior and superior sides.3.1.4 neutral point,nmidpoint of the bearing axis.3.1.5 spin-out,nexcessive rotation of the bearing compo-nent in a rotating platform knee or multi-directional platformknee such that there is dislocation between the femoral or tibialcomponents and the mobile bearing.3.1.6 spit-out,nescape of the bearing component frombeneath the femoral component either anteriorly or posteriorly.3.1.7 2-axis orthogonal load frame,na test machinecapable of applying forces and displacements that act at 90 toeach other.4.Significance and Use4.1 This test method is designed to provide a standardizedmethod to determine the constraint of mobile-bearing kneedesigns with regards to spin-out and spit-out of the mobilebearing.4.2 Similar to constraint testing of total knees(see TestMethod F1223),it is important to note that the test methoddoes not simulate the soft tissues and laxity of the knee joint,which may be key factors related to the occurrence of spin-outor spit-out.3For instance,a patient with good soft tissuerestraints will perhaps require a lower spin-out/spit-out resis-tance whereas a patient with major bone loss or destroyedligamentous structures will likely require an implant with ahigher spin-out/spit-out resistance.Therefore,the results fromthe test should be taken into account along with the conditionof the patients soft tissues to determine the relative safety forthe device.5.Apparatus and Materials5.1 A engineering analysis should be performed on all sizesof a knee design to justify a“worst case”size for this test.At1This 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 March 15,2014.Published April 2014.Originallyapproved in 2008.Last previous edition approved in 2008 as F2724 08.DOI:10.1520/F2724-08R14.2For 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.3Weale,A.E.,et al,“In Vitro Evaluation of the Resistance to Dislocation of aMeniscal-Bearing Total Knee Prosthesis Between 30 and 90 of Knee Flexion,”J.Arthroplasty,17(4),2002,pp.475483.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 least five mobile bearing inserts of that size should be tested.The tibial tray and knee femoral component may be reused formultiple trials as long as they are not damaged during testing.5.2 The mobile bearing surfaces shall be lightly coated withbovine serum,olive oil,mineral oil,or deionized water toreduce friction effects during testing.5.3 A 2-axis orthogonal load fra