1、Designation: F2724 08 (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 r
2、evision. 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
3、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 disloc
4、ation 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 unit
5、s 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 t
6、he 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
7、 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 (
8、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-directiona
9、l 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 forc
10、es 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 kne
11、es (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-
12、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 determ
13、ine 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 of ASTM Committee F04 on Medicaland Surgical Materials and Devices a
14、nd 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.ast
15、m.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 Betwe
16、en 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 States1least five mobile bearing inserts of that size should be tested.The tibial tray and knee femoral component may be
17、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 frame with feedback controlshall be used
18、 for dislocation testing. The machine must be ableto record force and displacement in both axes.5.4 Fixtures shall be required to allow for an 80 % medialand 20 % lateral load distribution to be applied through thecondyles of the femoral component.45.5 During testing, the tibial tray posterior slope
19、 and femo-ral component degree of flexion should be set according to therecommended surgical alignment.6. Specimen Preparation6.1 All components should be inspected prior to testing toensure that they meet the geometrical and material specifica-tions. The tibial inserts should undergo sterilization
20、as wouldnormally be employed with actual implants.6.2 The test components should be exposed to a cleanatmosphere at a temperature of 25 6 5C for 24 h prior totesting.7. Procedure7.1 Dislocation testing should be performed at 0, 60, and90 of flexion, as well as the maximum flexion angle that theimpla
21、nt is intended to achieve. The test procedure shall addressspin-out and spit-out simultaneously if allowed by the design.7.2 Either the tibial tray or the femoral component shall befree to translate under actuator control in the anterior andposterior (A/P) directions. A compressive joint reaction fo
22、rceshall be applied to the mobile bearing knee through either thetibial tray or the femoral component along the superior/inferior(S/I) direction. The femoral component should be oriented inthe desired flexion angles for the testing. The femoral compo-nent shall be constrained in all other translatio
23、ns/rotations.7.3 The tibial tray should be mounted into fixtures thatallow varus/valgus tilt. The pivot axis for the tilt should beselected based on calculations to apply 80 % of the force on themedial condyle and 20 % of the force on the lateral condyle.This can be accomplished by offsetting the pi
24、vot axis from thecenterline axis in the medial direction by 30 % of total bearingspacing. The posterior slope of the tibial plate should be theslope recommended in the surgical procedure for the device.7.4 The tibial tray shall be constrained in all othertranslations/rotations not mentioned in 7.2 o
25、r 7.3.7.5 The components should be adjusted to the zero rotationposition prior to testing. A joint reaction force of 710 N (160lbf) should be applied along the S/I axis and held constant. Thefemoral component should be positioned on the articulatingsurface at the same starting location, the approxim
26、ate low pointper design of both the lateral and medial condylar articulatingsurfaces at zero rotation, under a 50 N load prior to testing. Thefemoral component should be displaced anteriorly until contactis lost with either of the insert condyles.7.6 The components will be realigned to the original
27、posi-tion. The joint load of 710 N (160 lbf) will be reapplied alongthe S/I axis and the femoral component should then bedisplaced posteriorly until contact is lost with either of theinsert condyles.8. Reporting Results8.1 Report the following information:8.1.1 Justification for the choice of the kn
28、ee size tested.8.1.2 The total femoral displacement relative to the tibialtray and the S/I axis should be reported for each individualtrial.8.1.3 The maximum loads should be reported for eachindividual trial.8.1.4 The mode of failure that occurs first, spin-out orspit-out, should be reported for eac
29、h individual trial.APPENDIX(Nonmandatory Information)X1. RATIONALEX1.1 Spin-out and spit-out of mobile bearing inserts hasbeen found clinically to be a mode of failure, with a rate of lessthan 9.3 % reported in the literature.5X1.2 The applied load of 710 N (160 lbf) was selectedbased on the applied
30、 load in Test Method F1223. The load wasselected to provide a relative comparison between devices andis not intended to be related to any physiological load.X1.3 The 80 % medial/20 % lateral load distribution speci-fied in this test method was selected to represent an extremecase where the majority
31、of the load is applied to a singlecondyle, increasing the probability that spin-out/spit-out mayoccur. Based on one study reported in the literature,4the mostcommon loading distribution was 60 % medial/40 % lateral,with the majority of patients below the 80 % medial load level4Hurwitz, D. E., et al,
32、 “Dynamic Knee Loads During Gait Predict ProximalTibial Bone Distribution,” J. Biomechanics, 31, 1998, pp. 423430.5Bert, J. M., “Dislocation/Subluxation of Meniscal Bearing Elements After NewJersey Low-Contact Stress Total Knee Arthroplasty,” Clin. Orthop., 254, May 1990,pp. 211215.F2724 08 (2014)2t
33、hat was selected as a worst case for this test method.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent r
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36、ng you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard m
37、ay be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).F2724 08 (2014)3
