1、Designation: F1223 08 (Reapproved 2012)Standard 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, the year o
2、f 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 databaseof total knee replacement (TKR) motion characteristics withth
3、e intent of developing guidelines for the assignment ofconstraint criteria to TKR designs. (See the Rationale inAppendix X1.)1.2 This test method covers the means by which a TKRconstraint may be quantified according to motion delineated bythe inherent articular design as determined under specificloa
4、ding conditions in an in vitro environment.1.3 Tests deemed applicable to the constraint determinationare antero-posterior draw, medio-lateral shear, rotary laxity,valgus-varus rotation, and distraction, as applicable. Alsocovered is the identification of geometrical parameters of thecontacting surf
5、aces which would influence this motion and themeans 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 asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport
6、 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:2E4 Pra
7、ctices for Force Verification of Testing MachinesF2083 Specification for Total Knee Prosthesis3. Terminology3.1 DefinitionsItems in this category refer to the geo-metrical and kinematic aspects of TKR designs as they relate totheir human counterparts:3.1.1 anterior curvaturea condylar design which i
8、s gen-erally planar except for a concaveupward region anteriorlyon the tibial component.3.1.2 anterior posterior (AP)any geometrical lengthaligned with the AP orientation.3.1.3 AP displacementthe relative linear translation be-tween components in the AP direction.3.1.4 AP draw loadthe force applied
9、to the movablecomponent with its vector aligned in the AP direction causingor intending to cause an AP displacement.3.1.5 biconcavea condylar design with pronounced APand ML condylar radii seen as a “dish” in the tibial componentor a “toroid” in the femoral component.3.1.6 bearing surfacethose regio
10、ns of the componentwhich are intended to contact its counterpart for load transmis-sion.3.1.7 condylesentity designed to emulate the jointanatomy and used as a bearing surface primarily for transmis-sion of the joint reaction force with geometrical propertieswhich tend to govern the general kinemati
11、cs of the TKR.3.1.8 distractionthe separation of the femoral compo-nent(s) from the tibial component(s) in the z-direction.3.1.9 femoral side constraintthat constraint provided bythe superior articulating interfaces, determined by fixing theinferior surface of the mobile bearing component duringtest
12、ing.3.1.10 flexion anglethe angulation of the femoral compo-nent (about an axis parallel to the y-axis) from the fullyextended knee position to a position in which a “local” verticalaxis on the component now points posteriorly.3.1.10.1 DiscussionFor many implants, 0 of flexion canbe defined as when
13、the undersurface of the tibial component isparallel to the femoral component surface that in vivo contactsthe most distal surface of the femur. This technique may not bepossible for some implants that are designed to have a posteriortilt of the tibial component. In these cases, the user shallspecify
14、 how the 0 of flexion position was defined.3.1.11 hingea mechanical physical coupling betweenfemoral and tibial components which provides a single axisabout which flexion occurs.1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the
15、direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Dec. 1, 2012. Published December 2012. Originallyapproved in 1989. Last previous edition approved in 2008 as F1223 08. DOI:10.1520/F1223-08R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or
16、contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.12 hyperextensi
17、on stopa geometrical feature whicharrests further progress of flexion angles of negative value.3.1.13 inferior articulating interfacesany interface inwhich relative motion occurs between the underside of themobile bearing component and the tibial tray.3.1.14 internal-external rotationthe relative an
18、gulation ofthe moveable component about an axis parallel to the z-axis.3.1.15 joint reaction forcethe applied load whose vector isdirected parallel to the z-axis, generally considered parallel totibial longitudinal axis.3.1.16 medio-lateral (ML)the orientation that is alignedwith the y-axis in the d
19、efined coordinate system.3.1.17 ML condylar radiusthe geometrical curvature ofthe components condyle in the frontal plane.3.1.18 ML dimensionany geometrical length aligned withthe ML orientation.3.1.19 ML displacementthe relative linear translation be-tween components in the ML direction.3.1.20 ML s
20、hear loadthe force applied to the moveablecomponent with its vector aligned in the ML direction andcausing or intending to cause an ML displacement.3.1.21 mobile bearing componentthe ultra-high molecularweight polyethylene (UHMWPE) component that, by design,articulates against both the femoral beari
21、ng and the tibial tray.3.1.22 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.3.1.23 post-in-well featurea TKR design which tends toinfluence
22、 kinematics through the coupling of a prominenteminence with a recess or housing in a mating component.3.1.24 rotary laxity (RL)degree of relative angular motionpermitted for a moveable component about the z-axis asgoverned by inherent geometry and load conditions.3.1.25 rotary torquethe moment appl
23、ied to the moveablecomponent with its vector aligned to an axis parallel to thez-axis and causing or intending to cause an internal or externalrotation.3.1.26 superior articulating interfacesany interface inwhich relative motion occurs between the topside of the mobilebearing component and the femor
24、al bearing component.3.1.27 tibial eminencea raised geometrical feature sepa-rating the tibial condyles.3.1.28 tibial side constraintthat constraint provided by theinferior articulating interface.3.1.29 valgus-varus constraintdegree of relative angularmotion allowed between the femoral and tibial co
25、mponents ofpost-in-well designs (or similar designs) in the coronal plane.3.2 Definitions of Terms Specific to This Standard:3.2.1 constraintthe relative inability of a TKR to befurther displaced in a specific direction under a given set ofloading conditions as dictated by the TKRs geometricaldesign
26、. This motion is limited, as defined in this test, to theavailable articular or bearing surfaces found on the tibialcomponent. The actual relative motion values shall be providedas indicators of this type of constraint.3.2.2 coordinate system (see Fig. 1)a set of arbitrarycartesian coordinates affix
27、ed to the stationary component andaligned such that the origin is located at the intersection of they and z axes.3.2.2.1 DiscussionThe y-axis is parallel to the MLdirection, directed medially, and is coincident with the matedcomponents contact points when the knee is in the neutralposition (see 7.2)
28、. The z-axis is located midway between themated components contact points (or in the case of a singlecontact point, located at that point) and aligned in the superior-inferior direction of the distal component. A third axis, x,mutually orthogonal to the two previous axes is directedposteriorly. For
29、determination of contact points, see Annex A1and Fig. 2. The contact point shall be located to a tolerance of61 mm. In the case of multiple contact points on a condyle, anaverage location of the contact points shall be used.3.2.3 degrees of freedomalthough the knee joint is notedto have 6 df, or dir
30、ections in which relative motion is guided(three translations:AP, ML, vertical; three angulations: flexion,internal-external rotation, valgus-varus), the coupling effectsdue to geometrical features reduce this number to five whichare the bases of this test method: AP draw, ML shear,internal-external
31、 rotation, valgus-varus rotation, and distrac-tion.3.2.4 neutral position (see 7.2)that position in which theTKR is at rest with no relative linear or angular displacementsbetween components.3.2.4.1 DiscussionThis is design-dependent and theremay be a unique neutral position at each flexion angle. I
32、t maybe indicated that the femoral component, when implanted, bepositioned at some angle of hyperextension as seen when thepatients knee is fully extended; this, then becomes the neutralposition for negative flexion angle tests. The neutral positionFIG. 1 Defined Coordinate System ExamplesF1223 08 (
33、2012)2may be determined either by applying a compressive force of100 N and allowing the implant to settle or by measuring thevertical position of the movable component with respect to thestationary and using the low point of the component as theneutral point. In those implants with a flat zone and n
34、o uniquelow point, the midpoint of the flat zone can be used as theneutral point. For those implants having a tibial componentwith a posterior tilt, the user may use other means to define theneutral point, but shall report on how it was found.3.2.5 set pointthat numeric quantity assigned to an input
35、such as a load.3.2.6 movable componentthat component identified eitherthrough design or test equipment attributes as providing theactual relative motion values.3.2.6.1 DiscussionDepending upon the users fixtures andthe stationary component, it can be either the tibial or femoralcomponent.3.2.7 stati
36、onary componentthat component identified ei-ther through design or test equipment attributes as being at restduring that test to which actual relative motion values arereferenced.3.3 Symbols: Parameters:3.3.1 TAPoverall AP tibial surface dimension.3.3.2 TMLoverall ML tibial surface dimension.3.3.3 x
37、, y, zaxes of neutral position coordinate system asdefined in Annex A1.3.3.4 DISTa “yes/no” response to distraction test at thereported angle at which distraction is most likely to occur.4. Significance and Use4.1 This test method, when applied to available productsand proposed prototypes, is meant
38、to provide a database ofproduct functionality capabilities (in light of the suggested testregimens) that is hoped will aid the physician in making a moreinformed total knee replacement (TKR) selection.4.2 A proper matching of TKR functional restorative capa-bilities and the recipients (patients) nee
39、ds is more likely to beprovided by a rational testing protocol of the implant in aneffort to reveal certain device characteristics pertinent to theselection process.4.3 The TKR product designs are varied and offer a widerange of constraint (stability). The constraint of the TKR in thein vitro condit
40、ion depends on several geometrical and kine-matic interactions among the implants components which canbe identified and quantified. The degree of TKRs kinematicinteractions should correspond to the recipients needs asdetermined by the physician during clinical examination.4.4 For mobile bearing knee
41、 systems, the constraint of theentire implant construct shall be characterized. Constraint ofmobile bearings is dictated by design features at both theinferior and superior articulating interfaces.4.5 The methodology, utility, and limitations of constraint/laxity testing are discussed.3,4The authors
42、 recognize thatevaluating isolated implants (that is, without soft tissues) doesnot directly predict in vivo behavior, but will allow compari-sons among designs. Constraint testing is also useful forcharacterizing implant performance at extreme ranges of mo-tion which may be encountered in vivo at v
43、arying frequencies,depending on the patients anatomy, pre-operative capability,and post-operative activities and lifestyle.5. Apparatus5.1 General:5.1.1 The stationary component should be free to move onlyin directions parallel to the z-axis and not permitted to rotateabout this axis in all but the
44、distraction test. In the distractiontest it is fully fixed.NOTE 1In order to test asymmetrical designs, which may be asym-metrical about the sagittal or frontal planes, it may be necessary to allowadditional degrees of freedom in addition to those discussed in 5.1, 5.2,5.3, and 5.4. For example, the
45、 anterior ridge of the tibial bearing insertmay be thicker than the posterior ridge. Also the medial and lateralsurfaces may not be identical. As a result of this implant asymmetry,condylar liftoff may occur. For example, during a rotary test, one mayneed to allow valgus/varus angulation to ensure b
46、oth condyles remain incontact. If one does allow additional degree(s) of freedom, these changesto the test method shall be included in the report. For the internal/externalrotation test, asymmetrical designs may also require a different center ofrotation than as defined in Ssection 3 and Annex A1. I
47、f a different centerof rotation is used, it shall be stated in the report section.3Walker PS, Haider H, “Characterizing the Motion of Total Knee Replacementsin Laboratory Tests,” Clin. Ortho. Rel. Res., 410, 2003, pp. 5468.4Haider H, Walker PS, Measurements of Constraint of Total Knee Replacement,Jo
48、urnal of Biomechanics, Vol. 38, No. 2, 2005, pp. 341348.FIG. 2 Tibial Condyle Contact Point Location ExamplesF1223 08 (2012)35.1.2 The movable component shall be the displaced mem-ber when under loads specific to that test and shall beinstrumented accordingly to obtain data pertinent to that test.5.
49、1.3 Load or torque actuators producing input vectorswhich tend to displace the movable component relative to thestationary component according to the guidelines of the spe-cific tests shall be provided with a means of gradually applyingthe load or torque to the set point of that test.5.1.4 Displacement sensing devices shall be arranged so asto measure relative motion between components in accordancewith the prescribed coordinate system.5.1.5 Output graphs depicting the relationship of load anddisplacement are required
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