1、Designation: F1223 08 (Reapproved 2012)F1223 14Standard Test Method forDetermination of Total Knee Replacement Constraint1This standard is issued under the fixed designation F1223; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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 covers the establishment of a database of total knee replacement (TKR) motion characteristi
3、cs with theintent of developing guidelines for the assignment of constraint criteria to TKR designs. (See the Rationale in Appendix X1.)1.2 This test method covers the means by which a TKR constraint may be quantified according to motion delineated by theinherent articular design as determined under
4、 specific loading conditions in an in vitro environment.1.3 Tests deemed applicable to the constraint determination are antero-posterior draw, medio-lateral shear, rotary laxity,valgus-varus rotation, and distraction, as applicable. Also covered is the identification of geometrical parameters of the
5、 contactingsurfaces which would influence this motion and the means of reporting the test results. (See Practices E4.)1.4 This test method is not a wear test.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This standar
6、d 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 Documents2.1 ASTM S
7、tandards:2E4 Practices for Force Verification of Testing MachinesF2083 Specification for Knee Replacement Prosthesis3. Terminology3.1 DefinitionsItems in this category refer to the geometrical and kinematic aspects of TKR designs as they relate to theirhuman counterparts:3.1.1 anterior curvaturecurv
8、ature, na condylar design which is generally planar except for a concaveupward regionanteriorly on the tibial component.3.1.2 anterior posterior (AP)(AP),nany geometrical length aligned with the AP orientation.3.1.3 AP displacementdisplacement, nthe relative linear translation between components in
9、the AP direction.3.1.4 AP draw loadload, nthe force applied to the movable component with its vector aligned in the AP direction causingor intending to cause an AP displacement.3.1.5 biconcavebiconcave, na condylar design with pronounced AP and ML condylar radii seen as a “dish” in the tibialcompone
10、nt or a “toroid” in the femoral component.3.1.6 bearing surfacesurface, nthose regions of the component which are intended to contact its counterpart for loadtransmission.3.1.7 condylescondyles, nentity designed to emulate the joint anatomy and used as a bearing surface primarily fortransmission of
11、the joint reaction force with geometrical properties which tend to govern the general kinematics of the TKR.3.1.8 distractiondistraction, nthe separation of the femoral component(s) from the tibial component(s) in the z-direction.1 This test method is under the jurisdiction of ASTM Committee F04 on
12、Medical and Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Dec. 1, 2012May 15, 2014. Published December 2012June 2014. Originally approved in 1989. Last previous edition approved in 20082012 asF1223 08.F1223 08 (2012). D
13、OI: 10.1520/F1223-08R12.10.1520/F1223-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not
14、 an ASTM standard and is intended only to provide the user 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
15、. In all cases only the current versionof the standard as published 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 States13.1.9 femoral side constraintconstraint, nthat constraint provided b
16、y the superior articulating interfaces, determined byfixing the inferior surface of the mobile bearing component during testing.3.1.10 flexion angleangle, nthe angulation of the femoral component (about an axis parallel to the y-axis) from the fullyextended knee position to a position in which a “lo
17、cal” vertical axis on the component now points posteriorly.3.1.10.1 DiscussionFor many implants, 0 of flexion can be defined as when the undersurface of the tibial component is parallel to the femoralcomponent surface that in vivo contacts the most distal surface of the femur. This technique may not
18、 be possible for some implantsthat are designed to have a posterior tilt of the tibial component. In these cases, the user shall specify how the 0 of flexion positionwas defined.3.1.11 hingehinge, na mechanical physical coupling between femoral and tibial components which provides a single axisabout
19、 which flexion occurs.3.1.12 hyperextension stopstop, na geometrical feature which arrests further progress of flexion angles of negative value.3.1.13 inferior articulating interfacesinterfaces, nany interface in which relative motion occurs between the underside ofthe mobile bearing component and t
20、he tibial tray.3.1.14 internal-external rotationrotation, nthe relative angulation of the moveable component about an axis parallel to thez-axis.3.1.15 joint reaction forceforce, nthe applied load whose vector is directed parallel to the z-axis, generally consideredparallel to tibial longitudinal ax
21、is.3.1.16 medio-lateral (ML)(ML),nthe orientation that is aligned with the y-axis in the defined coordinate system.3.1.17 ML condylar radiusradius, nthe geometrical curvature of the components condyle in the frontal plane.3.1.18 ML dimensiondimension, nany geometrical length aligned with the ML orie
22、ntation.3.1.19 ML displacementdisplacement, nthe relative linear translation between components in the ML direction.3.1.20 ML shear loadload, nthe force applied to the moveable component with its vector aligned in the ML direction andcausing or intending to cause an ML displacement.3.1.21 mobile bea
23、ring componentcomponent, nthe ultra-high molecular weight polyethylene (UHMWPE) component that,by design, articulates against both the femoral bearing and the tibial tray.3.1.22 mobile bearing knee systemsystem, na knee prosthesis system, comprised of a tibial component, a mobile bearingcomponent th
24、at can rotate or rotate and translate relative to the tibial component, and a femoral component.3.1.23 post-in-well featurefeature, na TKR design which tends to influence kinematics through the coupling of a prominenteminence with a recess or housing in a mating component.3.1.24 rotary laxity (RL)(R
25、L),ndegree of relative angular motion permitted for a moveable component about the z-axis asgoverned by inherent geometry and load conditions.3.1.25 rotary torquetorque, nthe moment applied to the moveable component with its vector aligned to an axis parallel tothe z-axis and causing or intending to
26、 cause an internal or external rotation.3.1.26 superior articulating interfacesinterfaces, nany interface in which relative motion occurs between the topside of themobile bearing component and the femoral bearing component.3.1.27 tibial eminenceeminence, na raised geometrical feature separating the
27、tibial condyles.3.1.28 tibial side constraintconstraint, nthat constraint provided by the inferior articulating interface.3.1.29 valgus-varus constraintconstraint, ndegree of relative angular motion allowed between the femoral and tibialcomponents of post-in-well designs (or similar designs) in the
28、coronal plane.3.2 Definitions of Terms Specific to This Standard:3.2.1 constraintconstraint, nthe relative inability of a TKR to be further displaced in a specific direction under a given setof loading conditions as dictated by the TKRs geometrical design. This motion is limited, as defined in this
29、test, to the availablearticular or bearing surfaces found on the tibial component. The actual relative motion values shall be provided as indicators ofthis type of constraint.3.2.2 coordinate system (see Fig. 1),na set of arbitrary cartesian coordinates affixed to the stationary component andaligned
30、 such that the origin is located at the intersection of the y and z axes.3.2.2.1 DiscussionF1223 142The y-axis is parallel to the ML direction, directed medially, and is coincident with the mated components contact points whenthe knee is in the neutral position (see 7.2). The z-axis is located midwa
31、y between the mated components contact points (or inthe case of a single contact point, located at that point) and aligned in the superior-inferior direction of the distal component. Athird axis, x, mutually orthogonal to the two previous axes is directed posteriorly. For determination of contact po
32、ints, see AnnexA1 and Fig. 2. The contact point shall be located to a tolerance of 61 mm. In the case of multiple contact points on a condyle,an average location of the contact points shall be used.3.2.3 degrees of freedomfreedom, nalthough the knee joint is noted to have 6 df, or directions in whic
33、h relative motion isguided (three translations: AP, ML, vertical; three angulations: flexion, internal-external rotation, valgus-varus), the couplingeffects due to geometrical features reduce this number to five which are the bases of this test method: AP draw, ML shear,internal-external rotation, v
34、algus-varus rotation, and distraction.3.2.4 neutral position (see 7.2),nthat position in which the TKR is at rest with no relative linear or angular displacementsbetween components.3.2.4.1 DiscussionThis is design-dependent and there may be a unique neutral position at each flexion angle. It may be
35、indicated that the femoralcomponent, when implanted, be positioned at some angle of hyperextension as seen when the patients knee is fully extended; this,then becomes the neutral position for negative flexion angle tests. The neutral position may be determined either by applying acompressive force o
36、f 100 N and allowing the implant to settle or by measuring the vertical position of the movable componentwith respect to the stationary and using the low point of the component as the neutral point. In those implants with a flat zone andno unique low point, the midpoint of the flat zone can be used
37、as the neutral point. For those implants having a tibial componentwith a posterior tilt, the user may use other means to define the neutral point, but shall report on how it was found.3.2.5 set pointpoint, nthat numeric quantity assigned to an input such as a load.FIG. 1 Defined Coordinate System Ex
38、amplesFIG. 2 Tibial Condyle Contact Point Location ExamplesF1223 1433.2.6 movable componentcomponent, nthat component identified either through design or test equipment attributes asproviding the actual relative motion values.3.2.6.1 DiscussionDepending upon the users fixtures and the stationary com
39、ponent, it can be either the tibial or femoral component.3.2.7 stationary componentcomponent, nthat component identified either through design or test equipment attributes asbeing at rest during that test to which actual relative motion values are referenced.3.3 Symbols: Parameters:3.3.1 TAPoverall
40、AP tibial surface dimension.3.3.2 TMLoverall ML tibial surface dimension.3.3.3 x, y, zaxes of neutral position coordinate system as defined in Annex A1.3.3.4 DISTa “yes/no” response to distraction test at the reported angle at which distraction is most likely to occur.4. Significance and Use4.1 This
41、 test method, when applied to available products and proposed prototypes, is meant to provide a database of productfunctionality capabilities (in light of the suggested test regimens) that is hoped will aid the physician in making a more informedtotal knee replacement (TKR) selection.4.2 A proper ma
42、tching of TKR functional restorative capabilities and the recipients (patients)(patients) needs is more likelyto be provided by a rational testing protocol of the implant in an effort to reveal certain device characteristics pertinent to theselection process.4.3 The TKR product designs are varied an
43、d offer a wide range of constraint (stability). The constraint of the TKR in the in vitrocondition depends on several geometrical and kinematic interactions among the implants components which can be identified andquantified. The degree of TKRs kinematic interactions should correspond to the recipie
44、nts needs as determined by the physicianduring clinical examination.4.4 For mobile bearing knee systems, the constraint of the entire implant construct shall be characterized. Constraint of mobilebearings is dictated by design features at both the inferior and superior articulating interfaces.4.5 Th
45、e methodology, utility, and limitations of constraint/laxity testing are discussed.3,4 The authors recognize that evaluatingisolated implants (that is, without soft tissues) does not directly predict in vivo behavior, but will allow comparisons amongdesigns. Constraint testing is also useful for cha
46、racterizing implant performance at extreme ranges of motion which may beencountered in vivo at varying frequencies, depending on the patients anatomy, pre-operative capability, and post-operativeactivities and lifestyle.5. Apparatus5.1 General:5.1.1 The stationary component should be free to move on
47、ly in directions parallel to the z-axis and not permitted to rotate aboutthis axis in all but the distraction test. In the distraction test it is fully fixed.NOTE 1In order to test asymmetrical designs, which may be asymmetrical about the sagittal or frontal planes, it may be necessary to allow addi
48、tionaldegrees of freedom in addition to those discussed in 5.1, 5.2, 5.3, and 5.4. For example, the anterior ridge of the tibial bearing insert may be thicker thanthe posterior ridge. Also the medial and lateral surfaces may not be identical. As a result of this implant asymmetry, condylar liftoff m
49、ay occur. Forexample, during a rotary test, one may need to allow valgus/varus angulation to ensure both condyles remain in contact. If one does allow additionaldegree(s) of freedom, these changes to the test method shall be included in the report. For the internal/external rotation test, asymmetrical designs mayalso require a different center of rotation than as defined in Ssection 3 and AnnexA1. If a different center of rotation is used, it shall be stated in the reportsection
