1、Designation: F 1223 08Standard Test Method forDetermination of Total Knee Replacement Constraint1This standard is issued under the fixed designation F 1223; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 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 withthe intent of deve
3、loping 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 specificloading conditions
4、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 surfaces which would
5、 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 to address all
6、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 Practices for Force
7、 Verification of Testing MachinesF 2083 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 is gen-erally pl
8、anar 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 to the movablec
9、omponent 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 regions of the compo
10、nentwhich 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 kinematics of the TKR.3
11、.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 duringtesting.3.1.10 flex
12、ion 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 the undersurfac
13、e 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 how the 0 of f
14、lexion position was defined.3.1.11 hingea mechanical physical coupling betweenfemoral and tibial components which provides a single axisabout which flexion occurs.3.1.12 hyperextension stopa geometrical feature whicharrests further progress of flexion angles of negative value.1This test method is un
15、der the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved June 1, 2008. Published June 2008. Originallyapproved in 1989. Last previous edition approved in 2005 as F 1223 05.2
16、For 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C
17、700, West Conshohocken, PA 19428-2959, United States.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 angulation ofthe moveable component about an
18、 axis parallel to the z-axis.3.1.15 joint reaction forcethe applied load whose vectoris directed parallel to the z-axis, generally considered parallelto tibial longitudinal axis.3.1.16 medio-lateral (ML)the orientation that is alignedwith the y-axis in the defined coordinate system.3.1.17 ML condyla
19、r 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 shear loadthe force applied to the moveable
20、component with its vector aligned in the ML direction andcausing or intending to cause an ML displacement.3.1.21 mobile bearing componentthe ultra-high molecu-lar weight polyethylene (UHMWPE) component that, bydesign, articulates against both the femoral bearing and thetibial tray.3.1.22 mobile bear
21、ing knee systema knee prosthesis sys-tem, 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 kinematics through the coupling of a p
22、rominenteminence with a recess or housing in a mating component.3.1.24 rotary laxity (RL)degree of relative angular mo-tion permitted for a moveable component about the z-axis asgoverned by inherent geometry and load conditions.3.1.25 rotary torquethe moment applied to the moveablecomponent with its
23、 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 femoral bearing component.3.1.27 tibial em
24、inencea raised geometrical feature sepa-rating the tibial condyles.3.1.28 tibial side constraintthat constraint provided bythe inferior articulating interface.3.1.29 valgus-varus constraintdegree of relative angularmotion allowed between the femoral and tibial components ofpost-in-well designs (or s
25、imilar 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. This motion is limited, as defined
26、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 affixed to the stationary component andali
27、gned 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 ML direc-tion, directed medially, and is coincident with the matedcomponents contact points when the knee is in the neutralposition (see 7.2). The z-axis is located midway betw
28、een 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 determination of contact points, se
29、e 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 directions in which relative motion is
30、 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 rotation, valgus-varus rotation, a
31、nd 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. It maybe indicated that the femoral
32、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 positionmay be determined either by applying a compressive force of100 N and allowing the impl
33、ant to settle or by measuring theFIG. 1 Defined Coordinate System ExamplesF1223082vertical 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 no uniquelow point, the midpoint of the flat
34、 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 inputsuch as a load.3.2.6 movable componentthat
35、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 stationary componentthat component identified ei
36、-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, y, zaxes of neutral position coordinate s
37、ystem 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 to provide a database ofproduct functionali
38、ty capabilities (in light of the suggested testregimens) that is hoped to 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) needs is more likelyprovided for by a rational t
39、esting 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 condition depends on several geometrical and kine-mat
40、ic 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 systems, the constraint of theentire implant c
41、onstruct 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 recognize thatevaluating isolated implants (t
42、hat 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 varying frequencies,depending on the patients a
43、natomy, 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 distraction test. In the distractiontest it is
44、 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 anterior ridge of the tibial bearing insertma
45、y 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 both condyles remain incontact. If one does all
46、ow 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. If a different centerof rotation is used, it sh
47、all be stated in the report section.5.1.2 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.3Walker PS, Haider H, “Characterizing the Motion of Total Knee Replacementsin Laboratory Te
48、sts,” Clin. Ortho. Rel. Res., 410, 2003, pp. 5468.4Haider H, Walker PS, Measurements of Constraint of Total Knee Replacement,Journal of Biomechanics, Vol. 38, No. 2, 2005, pp. 341348.FIG. 2 Tibial Condyle Contact Point Location ExamplesF12230835.1.3 Load or torque actuators producing input vectorswh
49、ich 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 (see Fig. 3).5.1.6 The moveable component shall be mount
