U.S. patent application number 16/684801 was filed with the patent office on 2020-03-12 for anatomical motion hinged prosthesis.
The applicant listed for this patent is Smith & Nephew, Inc.. Invention is credited to Paul Charles Crabtree, JR., Roger Ryan Dees, JR., Jonathan Kirk Nielsen.
Application Number | 20200078181 16/684801 |
Document ID | / |
Family ID | 38663123 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200078181 |
Kind Code |
A1 |
Dees, JR.; Roger Ryan ; et
al. |
March 12, 2020 |
ANATOMICAL MOTION HINGED PROSTHESIS
Abstract
A hinged knee prosthesis comprises a tibial component and a
femoral component. The tibial component is configured to attach to
a tibia. The tibial component has a bearing surface. The femoral
component is configured to hingedly attach to the tibial component
and rotate relative to the tibial component. The femoral component
comprises a medial condyle and a lateral condyle. The medial and
lateral condyles have an eccentric sagittal curvature surface
configured to rotate and translate on the bearing surface of the
tibial component. A method of rotating a hinged knee through a
range of flexion is provided. The method fixedly attaches a femoral
component to a tibial component. Axial rotation of the femoral
component is induced relative to the tibial component when the
hinged knee is flexed.
Inventors: |
Dees, JR.; Roger Ryan;
(Senatobia, MS) ; Crabtree, JR.; Paul Charles;
(Nesbit, MS) ; Nielsen; Jonathan Kirk; (Dana
Point, CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Smith & Nephew, Inc. |
Memphis |
TN |
US |
|
|
Family ID: |
38663123 |
Appl. No.: |
16/684801 |
Filed: |
November 15, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15676024 |
Aug 14, 2017 |
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16684801 |
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13964306 |
Aug 12, 2013 |
9730799 |
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15676024 |
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12307102 |
Feb 3, 2010 |
8523950 |
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PCT/US2007/072611 |
Jun 30, 2007 |
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13964306 |
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60806383 |
Jun 30, 2006 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/384 20130101;
A61F 2/385 20130101; A61F 2/3859 20130101; A61F 2/38 20130101 |
International
Class: |
A61F 2/38 20060101
A61F002/38 |
Claims
1. A method of rotating a hinged knee through a range of flexion,
comprising the steps of: a. fixedly attaching a femoral component
to a tibial component; b. inducing axial rotation of the femoral
component relative to the tibial component when the hinged knee is
flexed.
2. The method of claim 1, further comprising the step of inducing
translation of the femoral component in an anterior/posterior
direction relative to the tibial component when the hinged knee is
flexed.
3. The method of claim 2, wherein the inducing translation step and
the inducing axial rotation steps occur simultaneously.
4. The method of claim 1, wherein the inducing axial rotation step
occurs through a portion of the range of flexion of the prosthetic
knee.
5. The method of claim 1, wherein the inducing axial rotation step
occurs through a first portion of the range of flexion of the
prosthetic knee and a second portion of the range of flexion of the
prosthetic knee.
6. The method of claim 5, wherein the first portion of the range of
flexion is not adjacent to the second portion of the range of
flexion.
7. The method of claim 1, wherein the inducing axial rotation step
occurs at varying angular velocities as the hinged knee passes
through the range of flexion of the knee.
8. The method of claim 1, wherein the fixedly attaching step
comprises the steps of: a. connecting a sleeved post to the tibial
insert such that a sleeved portion of the sleeved post and a post
portion of the sleeved post axially rotate relative to each other;
and b. fixing an axial hinge pin to the sleeved post such that the
axial hinge pin transversely connects a medial condyle of the
femoral component to the lateral condyle of the femoral
component.
9. The method of claim 8, further comprising the step of fixing the
sleeved portion of the sleeved post to a stem in the tibial
component.
10. The method of claim 8, further comprising the step of axially
displacing the sleeved portion of the sleeved post relative to the
post portion of the sleeved post when the hinged knee is flexed.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a division of pending U.S. patent
application Ser. No. 15/676,024, filed Aug. 14, 2017, which is a
continuation of U.S. patent application Ser. No. 13/964,306, filed
Aug. 12, 2013, now U.S. Pat. No. 9,730,799, issued Aug. 15, 2017,
which is a continuation of U.S. patent application Ser. No.
12/307,102, filed Feb. 3, 2010, now U.S. Pat. No. 8,523,950, issued
Sep. 3, 2013, which is a U.S. National Phase of International
Application No. PCT/US2007/072611, filed Jun. 30, 2007, which
claims the benefit of U.S. Provisional Application No. 60/806,383,
filed Jun. 30, 2006. Each of the prior applications is incorporated
by reference herein in its entirety.
BACKGROUND
1. Field
[0002] This application relates generally to knee prostheses and,
more particularly, the application relates to hinged knee
prostheses.
2. Related Art
[0003] Most hinged-knee prostheses only provide a mechanical means
to restore the joint in a hinge-like function. Other hinged-knee
prostheses provide for more kinematically-correct prostheses;
however, they rely mostly on remaining soft tissue to restore
normal kinematics to the joint. In most cases, the remaining soft
tissue has been compromised and/or missing/removed during surgery.
Thus the soft tissue cannot contribute significantly to restoring
normal kinematics, particularly anterior/posterior (A/P)
translation or normal axial rotation including rotation to the
`screw-home` position. Moreover, the remaining soft tissue may be
damaged when restoring normal kinematics by forcing motion of the
prostheses.
[0004] In prosthetic systems that address axial rotation, current
systems address rotation by allowing a rotating platform.
Generally, one of the two articulating prostheses (usually the
tibial insert or construct) is allowed rotational freedom. This
allows the soft tissues to rotate the joint in a more normal
fashion. However, most soft tissue has been compromised and cannot
reproduce normal or near normal rotation.
[0005] A/P translation is a motion that is seldom addressed. In
those prostheses that do address A/P translation, a cam mechanism
against the joint-linking mechanism (usually a post) or against the
tibial articular geometry is used to force the tibia anteriorly
relative to the distal femur as the knee flexes. This method of A/P
translation is common in a primary total knee arthroplasty (TKA) by
the use of a cam and post method in which the cam is on the femoral
articulating prosthesis and the post is found on the tibial
articulating prosthesis. This is commonly referred to as a
posterior or cruciate stabilized knee implant. These hinged knees
generally focus forces on a small area (such as a cam with point
and/or line contact and post), which may increase wear and decrease
the life span of the implant.
[0006] In U.S. Pat. Nos. 5,358,527 and 5,800,552, A/P translation
is allowed through flexion, yet the hinged knee does not control
and/or maintain a constant limit on A/P translation. In other
words, the femoral can be flexed and can translate posteriorly when
contact to the tibial bearing surface is not maintained. Thus the
femoral component does not maintain contact with the tibial
component when A/P translation occurs.
[0007] There remains a need in the art for kinematically-correct
prostheses including A/P translation and/or normal axial rotation.
In addition, there remains a need for kinematically-correct
prostheses that reduce wear on the prosthesis and reduce forces on
the remaining soft tissue.
SUMMARY
[0008] The disclosure provides a hinged knee prosthesis comprising
a tibial component and a femoral component. The tibial component is
configured to attach to a tibia. The tibial component has a bearing
surface. The femoral component is configured to hingedly attach to
the tibial component and rotate relative to the tibial component.
The femoral component comprises a medial condyle and a lateral
condyle. The medial and lateral condyles have a sagittal curvature
surface configured to induce axial rotation on the bearing surface
of the tibial component.
[0009] The medial and lateral condyles may have a plurality of
eccentric sagittal curvature surfaces configured to rotate on the
bearing surface of the tibial component.
[0010] The bearing surface of the tibial component is configured
with an anterior portion and a posterior portion. The posterior
portion of the bearing surface has a portion configured to guide
the medial and lateral condyles of the femoral component. Contact
points between the femoral component and the tibial component
translate in the anterior/posterior direction and rotate
axially.
[0011] The hinged knee may further comprise an axle hinge pin. The
axle hinge pin is located transversely between the medial and
lateral condyles. The eccentric sagittal curvature surface has a
center of rotation not aligned with the axle hinge pin.
[0012] The hinged knee prosthesis may further comprise a post
configured to extend from the tibial component to the femoral
component. A proximal portion of the post is configured to attach
to the axle hinge pin.
[0013] The center of rotation of a portion of the eccentric
sagittal curvature surface of the medial condyle may not be aligned
with the center of rotation of a portion of the eccentric sagittal
curvature surface of the lateral condyle. The medial and lateral
condyles direct axial rotation of the femoral component relative to
the tibial component.
[0014] The center of rotation of a portion of the eccentric
sagittal curvature surface of the medial condyle may be aligned
with the center of rotation of a portion of the eccentric sagittal
curvature surface of the lateral condyle, wherein the medial and
lateral condyles direct anterior/posterior translation of the
femoral component relative to the tibial component.
[0015] The medial condyle of the femoral component may further
comprise a concentric sagittal curvature surface. The center of
rotation of the concentric sagittal curvature surface of the medial
condyle is not aligned with the center of rotation of a portion of
the eccentric sagittal curvature surface of the lateral condyle.
The medial and lateral condyles direct axial rotation of the
femoral component relative to the tibial component.
[0016] The center of rotation of a first eccentric sagittal
curvature surface of the medial condyle may not be aligned with the
center of rotation of a first eccentric sagittal curvature surface
of the lateral condyle. The medial and lateral condyles direct
axial rotation and anterior/posterior translation of the femoral
component relative to the tibial component when the first eccentric
sagittal curvature surfaces contact the tibial component. The
center of rotation of a second eccentric sagittal curvature surface
of the medial condyle is aligned with the center of rotation of a
second eccentric sagittal curvature surface of the lateral condyle,
wherein the medial and lateral condyles direct anterior/posterior
translation of the femoral component relative to the tibial
component when the second eccentric sagittal curvature surfaces
contact the tibial component.
[0017] The hinged knee prosthesis may comprise a sleeve configured
to receive the post. The sleeve is configured to allow axial
rotation of the femoral component relative to the tibial
component.
[0018] The disclosure provides a method of rotating a hinged knee
through a range of flexion. The method fixedly attaches a femoral
component to a tibial component. Axial rotation of the femoral
component is induced relative to the tibial component when the
hinged knee is flexed.
[0019] The method may further comprise the step of inducing
translation of the femoral component in an anterior/posterior
direction relative to the tibial component when the hinged knee is
flexed.
[0020] The inducing translation step and the inducing axial
rotation steps may occur simultaneously.
[0021] The inducing axial rotation step may occur through a portion
of the range of flexion of the prosthetic knee.
[0022] The inducing axial rotation step may occur through a first
portion of the range of flexion of the prosthetic knee and a second
portion of the range of flexion of the prosthetic knee.
[0023] The first portion of the range of flexion may not be
adjacent to the second portion of the range of flexion.
[0024] The inducing axial rotation step may occur at varying
angular velocities as the hinged knee passes through the range of
flexion of the knee.
[0025] The fixedly attaching step may include connecting a sleeved
post to the tibial insert such that a sleeved portion of the
sleeved post and a post portion of the sleeved post axially rotate
relative to each other. Further the fixedly attaching step may
include fixing an axial hinge pin to the sleeved post such that the
axial hinge pin transversely connects a medial condyle of the
femoral component to the lateral condyle of the femoral
component.
[0026] The method may further comprise the step of fixing the
sleeved portion of the sleeved post to a stem in the tibial
component.
[0027] The method may further comprise the step of axially
displacing the sleeved portion of the sleeved post relative to the
post portion of the sleeved post when the hinged knee is
flexed.
[0028] Thus, kinematically-correct prostheses including A/P
translation and/or normal axial rotation may be achieved by the
structures in the disclosure. These kinematically-correct
prostheses may reduce wear on the prosthesis and reduce forces on
the remaining soft tissue. Further features, aspects, and
advantages of the present invention, as well as the structure and
operation of various embodiments of the present invention, are
described in detail below with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate embodiments and
together with the description, serve to explain the principles of
the invention. In the drawings:
[0030] FIG. 1 is an isometric view of an embodiment of a hinged
knee;
[0031] FIG. 2 is a cutaway view of the embodiment of FIG. 1;
[0032] FIG. 3 is a side view of the embodiment of FIG. 1;
[0033] FIG. 4 is a cutaway view of the embodiment of FIG. 3;
[0034] FIG. 5 is an isometric view of an embodiment of a hinged
knee;
[0035] FIG. 6 is a cutaway view of the embodiment of FIG. 5;
[0036] FIG. 7 is a side view of the embodiment of FIG. 5;
[0037] FIG. 8 is a cutaway view of the embodiment of FIG. 7;
[0038] FIG. 9 is an isometric view of an embodiment of a tibial
insert;
[0039] FIG. 10 is a top view of the tibial insert of FIG. 9;
[0040] FIG. 11 is a side view of an embodiment of femoral component
of a hinged knee;
[0041] FIGS. 12 and 13 are a side view and an isometric view,
respectively, of an embodiment of a hinged knee at extension;
[0042] FIGS. 14 and 15 are a side view and an isometric view,
respectively, of the hinged knee of FIG. 12 at 20 degrees
flexion;
[0043] FIGS. 16 and 17 are a side view and an isometric view,
respectively, of the hinged knee of FIG. 12 at 40 degrees
flexion;
[0044] FIGS. 18 and 19 are a side view and an isometric view,
respectively, of the hinged knee of FIG. 12 at 90 degrees
flexion;
[0045] FIGS. 20 and 21 are a side view and an isometric view,
respectively, of the hinged knee of FIG. 12 at 120 degrees
flexion;
[0046] FIGS. 22 and 23 are a side view and an isometric view,
respectively, of the hinged knee of FIG. 12 at 150 degrees
flexion;
[0047] FIGS. 24-26 are a side view, an isometric view, and a top
view, respectively, of an embodiment of a hinged knee at
extension;
[0048] FIGS. 27-29 are a side view, an isometric view, and a top
view, respectively, of the hinged knee of FIG. 27 at 20 degrees
flexion;
[0049] FIGS. 30-32 are a side view, an isometric view, and a top
view, respectively, of the hinged knee of FIG. 27 at 40 degrees
flexion;
[0050] FIGS. 33-35 are a side view, an isometric view, and a top
view, respectively, of the hinged knee of FIG. 27 at 90 degrees
flexion;
[0051] FIGS. 36-38 are a side view, an isometric view, and a top
view, respectively, of the hinged knee of FIG. 27 at 120 degrees
flexion; and
[0052] FIGS. 39-41 are a side view, an isometric view, and a top
view, respectively, of the hinged knee of FIG. 27 at 150 degrees
flexion.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0053] Referring to the accompanying drawings in which like
reference numbers indicate like elements, FIGS. 1-4 show views of
an embodiment of a hinged knee.
[0054] Turning now to FIG. 1, FIG. 1 is an isometric view of an
embodiment of a hinged knee 10. The hinged knee 10 includes a
femoral component 14, a tibial component 16, a pin sleeve 18 and a
pin 20. The tibial component 16 includes a tibial insert 24 and a
tibial base 26. The femoral component 14 includes a medial condyle
30 and a lateral condyle 32. The pin 20 connects the condyles 30
and 32 to the sleeve 18. The sleeve 18 connects to the tibial
component through a sleeved post (discussed below).
[0055] As the knee flexes, the femoral component 14 rotates
relative to the tibial component 16. The femoral component 14
rotates about the pin 20. Axial rotation and anterior/posterior
(A/P) translation of the femoral component 14 is urged by the shape
of the tibial insert 24 and the condyles 30 and 32. The axial
rotation and anterior/posterior (A/P) translation of the femoral
component 14 may occur because the pin 20 is able to axial rotate
and be axially translated relative to the post and sleeve of the
hinged knee 10.
[0056] The femoral component 14 and the tibial component 16 are
connected to the femur and tibia, respectively. Stems 36 are
inserted into the femur and tibia to fix the femoral component and
tibial component to the bones. The length and thickness of these
stems may be adjusted based upon required fixation, size of the
bones, and size of the intramedullary canals in the bones.
[0057] Turning now to FIG. 2, FIG. 2 is a cutaway view of the
embodiment of FIG. 1. The cutaway is taken in a sagittal plane
between the femoral condyles. FIG. 2 shows the pin 20 in the sleeve
18. The sleeve 18 is attached to a post sleeve 40 which surrounds a
post 42. The post 42 is attached to the tibial base 26, and may be
attached asymmetrically to the tibial base 26. The post sleeve 40
may be axially rotated and axially translated relative to the post
42. The sleeve 18 (and thus the pin 20) may rotate axially and
translate axially relative to the tibial component 16. The rotation
and translation allow for the femoral component 14 to axially
rotate and to translate in the A/P direction. The A/P translation
may be accomplished by the condyle surface having a curvature with
a center of rotation outside the pin 20. As the femoral component
14 rotates, a bushing 46 stops hyper extension so that the knee may
not over extend.
[0058] Turning now to FIG. 3, FIG. 3 is a side view of the
embodiment of FIG. 1. The pin 20 is located posterior to the center
of the knee 10. The curve 50 of the condyle 32 is eccentric with
respect to the center of rotation of the femoral component 14,
which is the pin 20. With respect to the tibial component 16, the
pin 20 axially rotates and axially translates as the knee
flexes.
[0059] Turning now to FIG. 4, FIG. 4 is a cutaway view of the
embodiment of FIG. 3. The cutaway is taken along the same sagittal
plane of the cutaway in FIG. 2. The cutaway shows the post sleeve
40 and post 42 of the hinged knee 10. A screw 56 fixes a post
receiver 58 to the post to lock the post sleeve 40 on the post 42.
The post sleeve 40 and pin sleeve 18 then may rotate and translate
axially without pulling off the post 42.
[0060] Turning now to FIGS. 5-8, these FIGs. show views of another
embodiment of a hinged knee 70. Turning now to FIG. 5, FIG. 5 is an
isometric view of an embodiment of the hinged knee 70. The hinged
knee 70 includes a femoral component 74, a tibial component 76, a
pin sleeve 78 and a pin 80. The tibial component 76 includes a
tibial insert 84 and a tibial base 86. The femoral component 74
includes a medial condyle 90 and a lateral condyle 92. The pin 80
connects the condyles 90 and 92 to the sleeve 78. The sleeve 78
connects to the tibial component through a sleeved post.
[0061] As the knee flexes, the femoral component 74 rotates
relative to the tibial component 76. The femoral component 74
rotates about the pin 80. Axial rotation and anterior/posterior
(A/P) translation of the femoral component 74 is urged by the shape
of the tibial insert 84 and the condyles 90 and 92. The axial
rotation and anterior/posterior (A/P) translation of the femoral
component 74 may occur because the pin 80 is able to axially rotate
and be axially translated relative to the post and sleeve of the
hinged knee 70.
[0062] The femoral component 74 and the tibial component 76 are
connected to the femur and tibia, respectively. Stems 96 are
inserted into the femur and tibia to fix the femoral component and
tibial component to the bones. The length and thickness of these
stems may be adjusted based upon required fixation, size of the
bones, and size of the intramedullary canals in the bones.
[0063] Turning now to FIG. 6, FIG. 6 is a cutaway view of the
embodiment of FIG. 5. The cutaway is taken in a sagittal plane
between the femoral condyles. FIG. 6 shows the pin 80 in the sleeve
78. The sleeve 78 is attached to a post 100 which is inserted into
a post sleeve 102. The post sleeve 102 is attached to the tibial
base 86. The post 100 may be axially rotated and axially translated
relative to the post sleeve 102. The pin sleeve 78 (and thus the
pin 80) may rotate axially and translate axially relative to the
tibial component 76. The rotation and translation allow for the
femoral component 74 to axially rotate and to translate in the A/P
direction. The A/P translation may be accomplished by the condyle
surface having a curvature with a center of rotation outside the
pin 80. As the femoral component 74 rotates, a bushing 106 stops
hyper extension so that the knee may not over extend.
[0064] Turning now to FIG. 7, FIG. 7 is a side view of the
embodiment of FIG. 5. The pin 80 is located posterior to the center
of the knee 70. The curve 110 of the condyle 92 is eccentric with
respect to the center of rotation of the femoral component 74,
which is the pin 80. With respect to the tibial component 76, the
pin 80 axially rotates and axially translates as the knee
flexes.
[0065] Turning now to FIG. 8, FIG. 8 is a cutaway view of the
embodiment of FIG. 7. The cutaway is taken along the same sagittal
plane of the cutaway in FIG. 6. The cutaway shows the post 100 and
post sleeve 102 of the hinged knee 70. An enlarged portion 106 of
the post 100 fixes the post 100 to the femoral component 74 so that
when the post 100 is inserted in the post sleeve 102, the femoral
component 74 is aligned and held in place relative to the tibial
component 76. The post 100 and pin sleeve 78 then may rotate and
translate axially without pulling the femoral component 74 off the
tibial base 76.
[0066] Turning now to FIGS. 9 and 10, these FIGs. show views of a
tibial insert 120. FIG. 9 is an isometric view of an embodiment of
a tibial insert 120 and FIG. 10 is a top view of the tibial insert
120 of FIG. 9. The tibial insert 120 includes a post hole 124 for
receiving the post from either the tibial base or the femoral
component. Direction lines 126 on a bearing surface 128 show the
lines the femoral component articulates on the tibial insert 120.
As the femoral component rotates on the insert 120, the position on
the line 126 travels posteriorly. The posterior portion of the
tibial insert 120 slopes to axially rotate and translate the
femoral component posteriorly. Together in conjunction with the
curvature of the condyles, the tibial insert 120 cause A/P
translation and axial rotation of the femoral component.
[0067] Turning now to FIG. 11, FIG. 11 is a side view of an
embodiment of femoral component 130 of a hinged knee. The curvature
of a condyle 131 includes a first distal portion 132 having a first
center of rotation 134, a second posterior portion 136 having a
second center of rotation 138 concentric with a pin hole 140, and a
third proximal portion 142 having a third center of rotation 144.
The centers of rotation 134 and 144 are eccentric to the pin hole
140. As the knee rotates, the contact point between the femoral
component 130 and the tibial insert produces a force normal to the
femoral component 130 and aligned with the center of rotation for
that section of the curvature. While the contact point is within
the distal portion of the curvature, the normal force points toward
the center of rotation 134. At the interface between the distal
portion 132 and the posterior portion 136, the normal force is
collinear with the centers of rotation 134 and 138. Similarly, at
the interface between the posterior portion 136 and the proximal
portion 142, the normal force is collinear with the centers of
rotation 138 and 144. Thus, the contact points do not jump during
rotation but smoothly move.
[0068] The eccentricity of the curvatures allows for the lateral
forces at the contact points to control axial rotation and A/P
translation. Because the forces are normal to the tibial and
femoral surfaces, reactive forces at the contact points induce A/P
motion and axial rotation. The pins, sleeves, and posts of the
hinged knee allow for the translation and rotation of the femoral
component 130 with respect to the tibial component.
[0069] Turning now to FIGS. 12-23, the FIGs. show side views and
isometric views of an embodiment of a hinged knee in different
angles of flexion. FIGS. 12 and 13 are a side view and an isometric
view, respectively, of an embodiment of a hinged knee at extension.
A contact point 150 anterior to the pin axis is the contact point
between a femoral component 152 and a tibial component 154. The
tibial component is posteriorly distal sloped at the contact point
150 so there is a reactive contact force attempting to push the
femoral component backwards. FIG. 13 shows the position of the
femoral component 152 at extension.
[0070] Turning now to FIGS. 14 and 15, FIGS. 14 and 15 are a side
view and an isometric view, respectively, of the hinged knee of
FIG. 12 at 20 degrees flexion. As the knee flexes, the contact
point 150 moves posteriorly. Additionally, as shown in FIG. 15, the
femoral component 152 has rotated relative to the tibial component
154. The axial rotation is urged by a differential between the
moments created by the reactive forces at the medial and lateral
condyles.
[0071] Turning now to FIGS. 16 and 17, FIGS. 16 and 17 are a side
view and an isometric view, respectively, of the hinged knee of
FIG. 12 at 40 degrees flexion. The contact point 150 has shifted
posteriorly and the femoral component has continued to rotate
axially. This change in contact point shows the A/P translation of
the femoral component as the knee rotates. While most of the motion
during early knee flexion is axial rotation, some A/P translation
occurs. This "rollback" and rotation is similar to normal joint
kinematics. These movements are urged by the shapes of the tibial
and femoral component. This minimizes shear forces on the patella
which may otherwise try to force these movements of the femoral
components. Generation of the shear forces in the patella may cause
pain or prosthetic failure.
[0072] The contact force 150 is directed through the center of the
pin hole as the curvature of the condyle transitions from the
distal eccentric portion to the posterior concentric portion
discussed with reference to FIG. 11.
[0073] Turning now to FIGS. 18 and 19, FIGS. 18 and 19 are a side
view and an isometric view, respectively, of the hinged knee of
FIG. 12 at 90 degrees flexion. While flexion continues through the
concentric portion, the A/P translation and axial rotation stops.
The distance to the center of the pin hole remains constant as the
center of curvature for the posterior portion of the condyle is
concentric with the pin hole.
[0074] Turning now to FIGS. 20 and 21, FIGS. 20 and 21 are a side
view and an isometric view, respectively, of the hinged knee of
FIG. 12 at 120 degrees flexion. The contact force 150 is directed
through the center of the pin hole as the curvature of the condyle
transitions from the posterior concentric portion of the curvature
to the proximal eccentric portion discussed with reference to FIG.
11. As the contact force 150 moves posterior the center of the pin
hole, the distance from the contact point to the center of the
pinhole lessens.
[0075] Turning now to FIGS. 22 and 23, FIGS. 22 and 23 are a side
view and an isometric view, respectively, of the hinged knee of
FIG. 12 at 150 degrees flexion. As the hinged knee continues to
rotate, the contact force generally creates A/P translation, and
little axial rotation. Again, this is generally consistent with
normal knee kinematics. While this embodiment has described A/P
translation and axial rotation by surface characteristics of the
tibial and femoral components 154 and 152, other embodiments may
accomplish these motions in other ways.
[0076] The additional embodiments generally try to control lateral
forces between the femoral and tibial components. For example,
differences in the lateral forces between condyles may create
motion. Additionally keeping lateral forces on one side small or
zero while controlling the forces on the other side can control
axial rotation. For more rotation, forces may be opposite in
direction to increase axial rotation. Because rotation is
controlled by moments, another method of controlling rotation is to
control the moment arms.
[0077] Another embodiment may create contact points with
corresponding tibial articulation of the femoral articulating
surfaces to vary from a plane perpendicular to the transverse axle
hinge pin. Generally, the plane would extend through a
medial/lateral and/or lateral/medial direction. As the knee moves
through the range of motion of the knee, the corresponding insert
articulating geometry remains parallel or varies from the same
plane creating an axial rotation through whole, in part, and/or
various ranges of the range of motion of the joint.
[0078] In another embodiment, a concentric sagittal curvature of
the medial or lateral femoral condyle's articular surface relative
to the transverse hinge pin location and the opposite femoral
condyle's articular surface may have eccentric curvature sagittally
to the hinge pin location. This shifts the contact with the tibial
articulation medial/lateral or lateral/medial at least in part
through a range of motion. The tibial articulating surfaces
correspond to femoral curvatures and induce axial rotation through
whole, in part, and/or various ranges of the range of motion of the
joint.
[0079] Alternatively, a concentric sagittal curvature of the medial
or lateral condyle's articular surface relative to the transverse
hinge pin location and the opposite condyle's articular surface
having eccentric curvature sagittally to the hinge pin location may
create the motion. The tibial articulating surfaces corresponds to
femoral curvatures where the corresponding eccentric medial or
lateral compartment follows a predetermined path relative to
multiple angles of flexion and its corresponding contact points
movement. The radial translation of these contact points around the
axial rotation around the tibial post/sleeve axis and the
corresponding concentric medial or lateral compartment follows a
predetermined path relative to multiple angles of flexion and its
corresponding contact point's movement around the axial rotation
around the tibial post/sleeve axis. This induces an axial rotation
through whole, in part, and/or various ranges of the range of
motion of the joint.
[0080] Another embodiment includes a femoral prosthesis with
eccentric sagittal curvature for both of the medial and lateral
articulating condylar portions of the femoral prosthesis relative
to the transverse axle pin position. A tibial insert with the
corresponding articulating geometry, either inclining and/or
declining as the eccentric contact points of the femoral
articulation translates, shift in a medial/lateral and/or
lateral/medial direction to induce an axial rotation through whole,
in part, and/or various ranges of the range of motion of the
joint.
[0081] In another embodiment, a concentric sagittal curvature of
the medial or lateral condyle's articular surface relative to the
transverse hinge pin location and the opposite condyle's articular
surface having eccentric curvature sagittally to the hinge pin
location. The tibial articulating surfaces correspond to femoral
curvatures where the corresponding eccentric medial or lateral
compartment follows a predetermined path relative to multiple
angles of flexion and its corresponding contact points movement and
the radial translation of these contact points around the axial
rotation around the tibial post/sleeve axis. The corresponding
concentric medial or lateral compartment follows a predetermined
inclining and/or declining path relative to multiple angles of
flexion and its corresponding contact points movement around the
axial rotation around the tibial post/sleeve axis which induces an
axial rotation through whole, in part, and/or various ranges of the
range of motion of the joint.
[0082] Alternatively, a femoral prosthesis with concentric sagittal
curvature for both of the medial and lateral articulating condylar
portions of the femoral prosthesis relative to the transverse pin
position. A tibial insert with the corresponding articulating
geometry, either inclining and/or declining, form an axial rotating
path relative to the femoral articulating surfaces.
Translational/rotational freedom allows the transverse pin to
rotate and translate the femoral prosthesis.
[0083] Turning now to FIGS. 24-41, the FIGs. Show side views,
isometric views, and top views of an embodiment of a hinged knee in
different angles of flexion. FIGS. 24-26 are a side view, an
isometric view, and a top view, respectively, of an embodiment of a
hinged knee at extension. A femoral component 180 rotates about a
pin 182 relative to a tibial component 184. Contact areas 200 show
the area in which a tibial insert 186 may contact the femoral
component 180. The contact areas 200 in FIGS. 24-41 show how the
femoral component 180 rotates and translates along the tibial
insert 186.
[0084] Turning now to FIGS. 27-29, FIGS. 27-29 are a side view, an
isometric view, and a top view, respectively, of the hinged knee of
FIG. 27 at 20 degrees flexion. The femoral component 180 continues
to rotate about the pin 182 relative to the tibial component 184.
The contact areas 200, particularly the lateral contact area, have
rolled back. The roll back of the lateral contact area corresponds
to axial rotation of the femoral component 180 relative to the
tibial component 184.
[0085] Turning now to FIGS. 30-32, FIGS. 30-32 are a side view, an
isometric view, and a top view, respectively, of the hinged knee of
FIG. 27 at 40 degrees flexion. The femoral component 180 continues
to rotate about the pin 182 relative to the tibial component 184.
The contact areas 200 have continued to roll back, and again the
lateral contact area has translated farther posteriorly compared to
the medial condyle. This corresponds to more axial rotation.
[0086] Turning now to FIGS. 33-35, FIGS. 33-35 are a side view, an
isometric view, and a top view, respectively, of the hinged knee of
FIG. 27 at 90 degrees flexion. The femoral component 180 continues
to rotate about the pin 182 relative to the tibial component 184.
From 40 degrees to 90 degrees of flexion, the rotation and
translation are minimized as the rotation continues through the
concentric portion of the curvature.
[0087] Turning now to FIGS. 36-38, FIGS. 36-38 are a side view, an
isometric view, and a top view, respectively, of the hinged knee of
FIG. 27 at 120 degrees flexion. The femoral component 180 continues
to rotate about the pin 182 relative to the tibial component 184.
Similar to the flexion between 40 and 90 degrees, from 90 degrees
to 120 degrees of flexion, the rotation and translation are
minimized as the rotation continues through the concentric portion
of the curvature.
[0088] Turning now to FIGS. 39-41, FIGS. 39-41 are a side view, an
isometric view, and a top view, respectively, of the hinged knee of
FIG. 27 at 150 degrees flexion. The femoral component 180 continues
to rotate about the pin 182 relative to the tibial component 184.
As the flexion continues from 120 to 150 degrees, the contact areas
200 translate and have little axial rotation.
[0089] Thus, as the knee flexes, the rotation allows for the
patella to slide along the patellar groove without generating
forces in the patella. Additionally, with movement approximating
the natural movement, the hinged knee does not generate forces in
the soft tissue. This may help preserve soft tissue that is
initially damaged by surgery. Moreover, some soft tissue is removed
during surgery, and thus the remaining soft tissue must work harder
to complete tasks. Reducing the forces on soft tissue can reduce
swelling, pain and additional stresses on the soft tissue after
surgery.
[0090] In view of the foregoing, it will be seen that the several
advantages of the invention are achieved and attained.
[0091] The embodiments were chosen and described in order to best
explain the principles of the invention and its practical
application to thereby enable others skilled in the art to best
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated.
[0092] As various modifications could be made in the constructions
and methods herein described and illustrated without departing from
the scope of the invention, it is intended that all matter
contained in the foregoing description or shown in the accompanying
drawings shall be interpreted as illustrative rather than limiting.
Thus, the breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims
appended hereto and their equivalents.
* * * * *