ASTM F1223-96
(Test Method)Standard Test Method for Determination of Total Knee Replacement Constraint
Standard Test Method for Determination of Total Knee Replacement Constraint
SCOPE
1.1 The purpose of this test method is to establish a database of total knee replacement (TKR) motion characteristics with the intent 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 the inherent articular design as determined while under 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, and distraction, as applicable. Also covered is the identification of geometrical parameters of the contacting surfaces which would influence this motion and the means of reporting the test results. (See Practices E4.)
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F 1223 – 96
Standard Test Method for
Determination of Total Knee Replacement Constraint
This standard is issued under the fixed designation F 1223; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.4 AP draw load—the force applied to the movable
component with its vector aligned in the AP direction causing
1.1 The purpose of this test method is to establish a database
or intending to cause an AP displacement.
of total knee replacement (TKR) motion characteristics with
3.1.5 biconcave—a condylar design with pronounced AP
the intent of developing guidelines for the assignment of
and ML condylar radii seen as a “dish” in the tibial component
constraint criteria to TKR designs. (See the Rationale in
or a “toroid” in the femoral component.
Appendix X1.)
3.1.6 bearing surface—those regions of the component
1.2 This test method covers the means by which a TKR
which are intended to contact its counterpart for load transmis-
constraint may be quantified according to motion delineated by
sion.
the inherent articular design as determined while under specific
3.1.7 condyles—entity designed to emulate the joint
loading conditions in an in vitro environment.
anatomy and used as a bearing surface primarily for transmis-
1.3 Tests deemed applicable to the constraint determination
sion of the joint reaction force with geometrical properties
are antero-posterior draw, medio-lateral shear, rotary laxity,
which tend to govern the general kinematics of the TKR.
and distraction, as applicable. Also covered is the identification
3.1.8 distraction—the separation of the femoral compo-
of geometrical parameters of the contacting surfaces which
nent(s) from the tibial component(s) in the z-direction.
would influence this motion and the means of reporting the test
3.1.9 flexion angle—the angulation of the femoral compo-
results. (See Practices E 4.)
nent (about an axis parallel to the y-axis) from the fully
1.4 This standard does not purport to address all of the
extended knee position to a position in which a “local” vertical
safety concerns, if any, associated with its use. It is the
axis on the component now points posteriorly.
responsibility of the user of this standard to establish appro-
3.1.9.1 Discussion—For many implants, 0° of flexion can
priate safety and health practices and determine the applica-
be defined as when the undersurface of the tibial component is
bility of regulatory limitations prior to use.
parallel to the femoral component surface that in vivo contacts
2. Referenced Documents
the most distal surface of the femur. This technique may not be
possible for some implants that are designed to have a posterior
2.1 ASTM Standards:
tilt of the tibial component. In these cases, the user shall
E 4 Practices for Force Verification of Testing Machines
specify how the 0° of flexion position was defined.
3. Terminology
3.1.10 hinge—a mechanical physical coupling between
femoral and tibial components which provides a singular axis
3.1 Definitions—Items in this category refer to the geo-
about which flexion occurs.
metrical and kinematic aspects of TKR designs as they relate to
3.1.11 hyperextension stop—a geometrical feature which
their human counterparts:
arrests further progress of flexion angles of negative value.
3.1.1 anterior curvature—a condylar design which is gen-
3.1.12 internal-external rotation—the relative angulation of
erally planar except for a concave—upward region anteriorly
the moveable component about an axis parallel to the z-axis.
on the tibial component.
3.1.13 joint reaction force—the applied load whose vector
3.1.2 anterior posterior (AP)—any geometrical length
is directed parallel to the z-axis, generally considered parallel
aligned with the AP orientation.
to tibial longitudinal axis.
3.1.3 AP displacement—the relative linear translation be-
3.1.14 medio-lateral (ML)—the orientation that is aligned
tween components in the AP direction.
with the y-axis in the defined coordinate system.
3.1.15 ML condylar radius—the geometrical curvature of
This test method is under the jurisdiction of ASTM Committee F-4 on Medical
the component’s condyle in the frontal plane.
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
3.1.16 ML dimension—any geometrical length aligned with
F04.15 on Material Test Methods.
the ML orientation.
Current edition approved April 10, 1996. Published June 1996. Originally
published as F 1223 – 89. Last previous edition F 1223 – 95.
Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F1223–96
3.1.17 ML displacement—the relative linear translation be- inferior direction of the distal component. A third axis, x,
tween components in the ML direction. mutually orthogonal to the two previous axes is directed
3.1.18 ML shear load—the force applied to the moveable posteriorly. For determination of contact points, see Annex A1
component with its vector aligned in the ML direction causing and Fig. 2. The contact point shall be located to a tolerance of
or intending to cause an ML displacement. 61 mm. In the case of multiple contact points on a condyle, an
3.1.19 post-in-well feature—a TKR design which tends to average location of the contact points shall be used.
influence kinematics through the coupling of a prominent 3.2.3 degrees of freedom—although the knee joint is noted
eminence with a recess or housing in a mating component. to have 6 df, or directions in which relative motion is guided
3.1.20 rotary laxity (RL)—degree of relative angular mo- (three translations: AP, ML, vertical; three angulations: flexion,
tion permitted of moveable component about the z-axis as internal-external, varus-valgus), the coupling effects due to
governed by inherent geometry and load conditions. geometrical features reduce this number to the four which are
3.1.21 rotary torque—the moment applied to the moveable the bases of this test method: AP draw, ML shear, internal-
component with its vector aligned to an axis parallel to the external rotation, and distraction.
z-axis and causing or intending to cause an internal or external 3.2.4 neutral position (see 7.2)—that position in which the
rotation. TKR is at rest with no relative linear or angular displacements
3.1.22 tibial eminence—a raised geometrical feature sepa- between components.
rating the tibial condyles. 3.2.4.1 Discussion—This is design-dependent and there
3.2 Definitions of Terms Specific to This Standard: may be a unique neutral position at each flexion angle. It may
3.2.1 constraint—the relative inability of a TKR to be be indicated that the femoral component, when implanted, be
further displaced in a specific direction under a given set of positioned at some angle of hyperextension as seen when the
loading conditions as dictated by the TKR’s geometrical patient’s knee is fully extended; this, then becomes the neutral
design. This motion is limited, as defined in this test, to the position for negative flexion angle tests. The neutral position
available articular or bearing surfaces found on the tibial may be determined by either applying a compressive force of
component. The actual relative motion values will be provided 100 N and allowing the implant to settle or by measuring the
as an indicator of this type of constraint. vertical position of the movable component with respect to the
3.2.2 coordinate system —(see Fig. 1) a set of arbitrary stationary and using the low point of the component as the
cartesian coordinates affixed to the stationary component and neutral point. In those implants with a flat zone and no unique
aligned such that the origin is located at the intersection of the
y and z axes.
3.2.2.1 Discussion—The y-axis is parallel to the ML direc-
tion, directed medially, and is coincident with the mated
components’ contact points when the knee is in the neutral
position (see 7.2). The z-axis is located midway between the
mated components’ contact points (or in the case of a singular
contact point, located at that point) and aligned in the superior-
FIG. 1 Defined Coordinate System Examples FIG. 2 Tibial Condyle Contact Point Location Examples
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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F1223–96
low point, the midpoint of the flat zone can be used as the 5.1.3 Load or torque actuators producing input vectors
neutral point. For those implants having a tibial component which tend to displace the movable component relative to the
with a posterior tilt, the user may use other means to define the stationary component according to the guidelines of the spe-
neutral point, but will report on how it was found. cific tests shall be provided with a means of gradually applying
3.2.5 set point—that numeric quantity assigned to an input the load or torque to the set point of that test.
such as a load. 5.1.4 Displacement sensing devices shall be arranged so as
to measure relative motion between components in accordance
3.2.6 movable component—that component identified either
through design or test equipment attributes as providing the with the prescribed coordinate system.
actual relative motion values. 5.1.5 Output graphs depicting the relationship of load and
3.2.6.1 Discussion—Depending upon the user’s fixtures and displacement may provide the investigator with insight into the
device’s behavior or test setup, or both. It is therefore recom-
the stationary component, it can be either the tibial or femoral
component. mended that such capabilities of the apparatus be included in
these tests. (See Fig. 3.)
3.2.7 stationary component—that component identified ei-
ther through design or test equipment attributes as being at rest 5.2 Antero-Posterior Draw Test—The movable component
shall be rigidly set in a fixture free to move in linear directions
during that test to which actual relative motion values are
referenced. parallel to the x-axis only.
5.3 Medio-Lateral Shear Test—The movable component
3.3 Symbols:Symbols—Parameters:
3.3.1 TAP—overall AP tibial surface dimension. shall be rigidly set in a fixture free to move in linear directions
parallel to the y-axis only.
3.3.2 TML—overall ML tibial surface dimension.
5.4 Rotary Laxity Test—The movable component shall be
3.3.3 x, y, z—axes of neutral position coordinate system as
rigidly set in a fixture free to move in angular displacements
defined in Annex A1.
about an axis parallel to the z-axis only.
3.3.4 x ,x ,y ,y —relative linear displacements of mov-
1 2 1 2
5.5 Distraction Test:
able component along respective axes as defined in the figures.
5.5.1 The movable component shall be rigidly set in a
3.3.5 x ,y —origin location with respect to stated plateau
o o
fixture free to move in only those directions tending to permit
landmark.
such distraction. Should distraction be possible at more than
3.3.6 ANG—relative angular displacements of movable
one angle of flexion the test should be conducted at that angle
component about z-axis as defined in the figures.
which would most likely permit the distraction.
3.3.7 DIST—a “yes/no” response to distraction test at the
5.5.2 The stationary component shall be rigidly set in a
reported angle at which distraction is most likely to occur.
fixture and not permitted to move in those directions allowed to
the movable component.
4. Significance and Use
4.1 This test method, when applied to available products
6. Test Specimens
and proposed prototypes, will attempt to provide a database of
6.1 TKR Specimens:
product functionality capabilities (in light of the suggested test
6.1.1 The TKR should be the manufacturer’s designated“
regimens) that is hoped to aid the physician in making a more
standard” or “medium” size as this is more suitable to the
informed total knee replacement (TKR) selection.
loading regimes encountered in the tests.
4.2 A proper matching of TKR functional restorative capa-
6.1.2 The implant shall be procured in its original packaging
bilities and recipient’s (patient’s) needs is more likely provided
as supplied to the user by the manufacturer.
for by a rational testing protocol of the implant in an effort to
6.1.3 If the implant is not available in its package state, the
reveal certain device characteristics pertinent to the selection
condition of the device must meet all geometry and material
process.
specifications, but may contain slight surface irregularities
4.3 The TKR product designs are varied and offer a wide
(that is, “cosmetic rejects”) not considered influential in those
range of constraint (stability). The constraint of the TKR in the
regions of the device deemed critical to the specific test.
in vitro condition is dependent on several geometrical and
kinematic interactions among the implant’s components which
can be identified and quantified. The degree of TKR’s kine-
matic interactions should correspond to the recipient’s needs as
determined by the physician during clinical examination.
5. Apparatus
5.1 General:
5.1.1 The stationary component should be free to move only
in directions parallel to the z-axis and not permitted to rotate
about this axis in all but the distraction test. In the distraction
test it is fully fixed.
5.1.2 The movable component shall be the displaced mem-
ber when under loads specific to that test and shall be
instrumented accordingly to obtain data pertinent to that test. FIG. 3 Output Graph Example
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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F1223–96
6.2 TKR Prototype—The implant shall be of quality as in
6.1.3.
7. Sample Measurement
7.1 General:
7.1.1 The constraint values refer to the relative ability of the
components to be displaced under the loads applied while
guided by the geometrical features inherent in the component
design. These features are herein identified as being solely
based on bearing surfaces, although certain designs offer
enhanced constraint (stability) due to other structures. The
tibial bearing surfaces are used as a reference for relative NOTE 1—Coronal plane sec
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