U.S. patent application number 15/599778 was filed with the patent office on 2017-09-07 for total knee implant.
The applicant listed for this patent is Zimmer, Inc.. Invention is credited to Jeffrey D. Brown, Christopher M. Byrd, Jody L. Claypool, Brian D. Earl, John E. Pendleton, Adam H. Sanford.
Application Number | 20170252172 15/599778 |
Document ID | / |
Family ID | 42077511 |
Filed Date | 2017-09-07 |
United States Patent
Application |
20170252172 |
Kind Code |
A1 |
Byrd; Christopher M. ; et
al. |
September 7, 2017 |
TOTAL KNEE IMPLANT
Abstract
A knee prosthesis is provided for use in knee arthroplasty. In
one exemplary embodiment, the present invention provides a tibial
prosthesis having a tibial baseplate with a fixed medial bearing
component and a mobile lateral bearing component. In one exemplary
embodiment, the lateral bearing component is secured to the lateral
portion of the tibial baseplate utilizing at least one prosthetic
ligament. Additionally, in one exemplary embodiment, a stop is
provided to limit anterior or posterior movement of the lateral
bearing component relative to the tibial baseplate. For example,
the stop may be defined by cooperating shoulders formed on the
lateral bearing and the tibial baseplate.
Inventors: |
Byrd; Christopher M.;
(Elkhart, IN) ; Sanford; Adam H.; (Los Angeles,
CA) ; Earl; Brian D.; (South Bend, IN) ;
Claypool; Jody L.; (Warsaw, IN) ; Brown; Jeffrey
D.; (Palo Alto, CA) ; Pendleton; John E.;
(Dunwoody, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zimmer, Inc. |
Warsaw |
IN |
US |
|
|
Family ID: |
42077511 |
Appl. No.: |
15/599778 |
Filed: |
May 19, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14520923 |
Oct 22, 2014 |
9687349 |
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15599778 |
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12694343 |
Jan 27, 2010 |
8888856 |
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14520923 |
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61147492 |
Jan 27, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30387
20130101; A61F 2/468 20130101; A61F 2/4684 20130101; A61F 2/3836
20130101; A61F 2002/4666 20130101; A61F 2250/0018 20130101; A61F
2/3868 20130101; A61F 2220/0075 20130101; A61F 2002/30014 20130101;
A61F 2250/0073 20130101; A61F 2220/0025 20130101; A61F 2002/3895
20130101; A61F 2250/006 20130101; A61F 2002/304 20130101; A61F 2/08
20130101; A61F 2002/30462 20130101; A61F 2/385 20130101 |
International
Class: |
A61F 2/38 20060101
A61F002/38; A61F 2/08 20060101 A61F002/08 |
Claims
1. A prosthetic knee system, comprising: a femoral component having
a lateral condyle and a medial condyle; a tibial component
comprising: a baseplate having a bone facing surface and an
opposing support surface; a medial bearing component having a
medial articulation surface and a medial attachment surface, said
medial attachment surface coupleable with said support surface of
said baseplate to fix said medial component to said baseplate,
whereby movement of said medial component relative to said
baseplate is substantially entirely prevented; and a lateral
bearing component having a lateral articulation surface and a
lateral attachment surface, said lateral attachment surface
slidingly securable to said support surface of said baseplate,
wherein said lateral component is translatable relative to said
baseplate a first prosthetic ligament detachably connected to the
baseplate and the lateral condyle; and a second prosthetic ligament
detachably connected to the baseplate and the medial condyle.
2. The prosthetic knee system of claim 1, further comprising: a
T-shaped projection formed on one of said lateral attachment
surface of said lateral component and said support surface of said
baseplate, a T-shaped groove formed on the other of said lateral
attachment surface of said lateral component and said support
surface of said baseplate, said T-shaped projection sized and
positioned to cooperate with said T-shaped groove to form a
securement mechanism when said lateral attachment surface of said
lateral component is slidingly secured to said support surface of
said baseplate, said securement mechanism allowing translation of
said lateral component in an anterior direction and a posterior
direction.
3. The prosthetic knee system of claim 1, wherein said lateral
component is translatable relative to said baseplate independent of
said medial component.
4.-8. (canceled)
9. The prosthetic knee system of claim 3, wherein: the baseplate
further comprises a projection extending from the support surface
between the medial bearing component and the lateral bearing
component, the projection extending in an anterior-posterior
direction; and the first and second prosthetic ligaments connect to
the baseplate at the projection.
10. The prosthetic knee system of claim 1, wherein the first
prosthetic ligament is the only ligament attaching the lateral
condyle to the tibial component and the second prosthetic ligament
is the only ligament attaching the medial condyle to the tibial
component.
11. The prosthetic knee system of claim 1, wherein each of the
first and second prosthetic ligaments comprises: an elongate body
having a width and extending between a first end and a second end;
a first head connected to the first end; and a second head
connected to the second end; wherein the first and second heads are
wider than the width.
12. The prosthetic knee system of claim 11, further comprising: a
first groove located in the lateral condyle for receiving the first
head of the first prosthetic ligament; a second groove located in
the medial condyle for receiving the first head of the second
prosthetic ligament; a third groove located in the baseplate for
receiving the second head of the first prosthetic ligament; and a
fourth groove located in the baseplate for receiving the second
head of the second prosthetic ligament.
13. The prosthetic knee system of claim 12, wherein the first and
second heads are spherical and the first, second, third and fourth
sockets are shaped to mate with the spherical heads.
14. The prosthetic knee system of claim 12, wherein the fourth
groove is located anterior of the third groove.
15. The prosthetic knee system of claim 14, wherein the first and
second prosthetic ligaments crossover each other in a
medial-lateral direction extending between the femoral component
and the baseplate.
16. The prosthetic knee system of claim 11, wherein the first and
second heads are formed of a resiliently deformable material.
17. The prosthetic knee system of claim 1, wherein the first
prosthetic ligament has a first stiffness and the second prosthetic
ligament has a second stiffness that is different than the first
stiffness.
18. A prosthetic knee system comprising: a femoral component having
a lateral condyle and a medial condyle; a tibial component
comprising: a medial portion for engaging the medial condyle; a
lateral portion for engaging the lateral condyle; and a central
portion positioned between the medial and lateral portions; a first
prosthetic ligament solely coupling the lateral condyle to the
central portion; and a second prosthetic ligament solely coupling
the medial condyle to the central portion.
19. The prosthetic knee system of claim 18 wherein: the first
prosthetic ligament is attached to the central portion posterior of
where the second prosthetic ligament is attached to the central
portion; the first prosthetic ligament is attached to the central
portion closer to a medial side of the central portion than a
lateral side of the central portion; and the second prosthetic
ligament is attached to the central portion closer to the lateral
side of the central portion than the medial side of the central
portion.
20. The prosthetic knee system of claim 18, wherein the first and
second prosthetic ligaments are detachably coupled to the femoral
component and the tibial component at attachment points.
21. The prosthetic knee system of claim 20, wherein each attachment
point comprises: a spherical head attached to an end of one of the
first and second prosthetic ligaments; and a spherical socket
positioned on the femoral component or the tibial component to
receive the spherical head.
22. The prosthetic knee system of claim 21, wherein each spherical
head is resilient.
23. A prosthetic knee system comprising: a femoral component having
a lateral condyle and a medial condyle; a tibial component
comprising: a medial portion for engaging the medial condyle; a
lateral portion for engaging the lateral condyle; and a central
portion positioned between the medial and lateral portions; a first
prosthetic ligament coupling the lateral condyle to a medial
portion of the central portion; and a second prosthetic ligament
coupling the medial condyle to a lateral portion of the central
portion.
24. The prosthetic knee system of claim 23, wherein the first
prosthetic ligament attaches to the central portion posterior of
where the second prosthetic ligament attaches to the central
portion.
25. The prosthetic knee system of claim 23, wherein the first
prosthetic ligament and the second prosthetic ligament each
comprises: a first resilient spherical head; a second resilient
spherical head; and a resiliently deformable elongate body
extending between the first resilient spherical head and the second
resilient spherical head.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under Title 35, U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application Ser. No.
61/147,492, entitled TOTAL KNEE IMPLANT, filed on Jan. 27, 2009,
the entire disclosure of which is expressly incorporated herein by
reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to orthopedic prostheses and,
particularly, to knee prostheses.
[0004] 2. Description of the Related Art
[0005] In a natural knee joint, the meniscus is positioned between
the distal end of the emur and the proximal end of the tibia to
provide cushioning and support to the tibia and femur as they
rotate relative to one another. Additionally, the medial side of
the meniscus is more stationary than the lateral side of the
meniscus, which is more flexible and/or mobile. The mobility of the
lateral meniscus increases the ability of the lateral condyle of
the femur to roll off of the tibial plateau during high flexion of
the knee, i.e., it increases the ability of the femur to rotate
into a position in which the lateral condyle is not entirely
supported by the tibial plateau.
[0006] In a fixed bearing tibial prosthesis, external rotation of
the femoral component against the tibial component can be limited
due to the fixed nature of the prosthesis. Thus, the lateral
condyle of the femur is prevented from rolling off the tibial
plateau. In order to provide for articulation of the knee joint
that better replicates the natural articulation of the knee joint,
a mobile bearing tibial prosthesis may be used. In a mobile bearing
tibial prosthesis, the entirety of the tibial bearing, including
both the medial and lateral condyles, is rotatable relative to a
tibial baseplate. Additionally, in some mobile bearing tibial
prostheses, the tibial bearing is rotatable about a point
positioned on the medial condyle of the tibial baseplate. This
results in increased lateral rotation of the bearing component,
which better mimics natural knee joint articulation.
[0007] Additionally, during a total knee arthroplasty, it may be
necessary to resect the cruciate ligaments of the knee joint. This
may result, for example, in decreased support and stability in the
patient's knee joint.
SUMMARY
[0008] The present disclosure provides knee prostheses for use in
knee arthmplasty. In one exemplary embodiment, the present
invention provides a tibial prosthesis having a tibial baseplate
with a fixed medial bearing component and a mobile lateral bearing
component. In one exemplary embodiment, the lateral bearing
component is secured to the lateral portion of the tibial baseplate
utilizing at least one prosthetic ligament. Additionally, in one
exemplary embodiment, a stop is provided to limit anterior or
posterior movement of the lateral bearing component relative to the
tibial baseplate. For example, the stop may be defined by
cooperating shoulders formed on the lateral bearing and the tibial
baseplate.
[0009] By providing a fixed medial component and a mobile lateral
component for a tibial prosthesis, an articulating surface of a
medial condyle of a femoral component may be highly conforming with
an articulating surface on the medial component of the tibial
prosthesis, which acts to control anterior and posterior movement
of the joint. Additionally, the mobile lateral component of the
tibial component allows for a lateral condyle on a femoral
component to undergo additional rollback, which is normally
prevented in both fixed and mobile tibial prostheses, in order to
more accurately replicate the natural articulation of the knee
joint.
[0010] In one exemplary embodiment, the present invention also
includes a femoral component. In one exemplary embodiment, the
femoral component includes a crossbar extending between opposing
medial and lateral condyles. In this embodiment, a prosthetic
ligament is wrapped around the crossbar and secured to attachment
points on the tibial baseplate. The prosthetic ligament acts to
replicate the function of the patient's resected anterior cruciate
ligament (ACL) by restricting movement of the femoral component
relative to the tibial component. In other exemplary embodiments, a
plurality of prosthetic ligaments may be provided that are
configured for attachment to a plurality of attachment points on
the tibial baseplate and femoral components. In this manner, by
selectively positioning the prosthetic ligaments with respect to
the femoral component and tibial baseplate, the natural
articulation of the knee joint for an individual patient may be
more accurately replicated.
[0011] In other exemplary embodiments, provisional prosthetic
ligaments may be utilized to facilitate the trialing of the femoral
component and the tibial component. For example, in one exemplary
embodiment, the provisional prosthetic ligaments are designed to
fail if the ligaments are subjected to a tension that exceeds a
predetermined tension limit. In one exemplary embodiment, opposing
portions of the provisional prosthetic ligaments may be secured to
one another by magnets. Once a tension that exceeds the
predetermined amount of tension is applied to the ligaments, the
magnetic force between the two magnets that holds the opposing
portions of the ligaments together is overcome, causing the
ligaments to fail. This allows a surgeon to trial the prosthetic
component and, if the ligaments fail, the surgeon is provided with
a visual and tactile indication that the patient's knee joint is
too tight. In other exemplary embodiments, the provisional
prosthetic ligaments may be designed to break if a tension in
excess of a predetermined tension limit is applied to the
ligaments. In another exemplary embodiment, the provisional
prosthetic ligaments may be designed to separate from one of the
femoral component and tibial component if a tension is applied to
the ligaments that exceeds a predetermined amount of tension.
[0012] Additionally, by allowing tier the use of prosthetic
ligaments, the ability of a surgeon to replicate the natural
articulation of a knee joint for a particular patient is increased.
For example, when a plurality of attachment sites are provided on
the tibial and/or femoral components, the surgeon may individually
select attachment sites based on specific physical characteristics
of an individual patient. As a result, the surgeon may more
accurately replicate the natural knee articulation for an
individual patient. Further, by providing provisional prosthetic
ligaments that allow for separation and/or failure of the
provisional prosthetic ligaments if a tension that exceeds a
predetermined tension is applied to the provisional prosthetic
ligaments, the surgeon may also test the knee joint to determine
whether the joint is too tight. The provisional prosthetic
ligaments provide a visual and/or tactile feedback that immediately
indicates whether the joint is too tight.
[0013] In one form thereof, the present invention provides a
prosthetic knee system including a femoral component having a
lateral condyle and a medial condyle and a tibial component having
a base plate, a medial bearing surface and a lateral bearing
surface. The baseplate includes a bone facing surface and an
opposing support surface. The medial bearing component includes a
medial articulation surface and a medial attachment surface, with
the medial attachment surface coupled with the support surface of
the baseplate to fix the medial component to the baseplate, so that
movement of said medial component relative to said baseplate is
substantially entirely prevented. The lateral bearing component
includes a lateral articulation surface and a lateral attachment
surface, with the lateral attachment surface slidingly secured to
the support surface of the baseplate. The lateral component is
translatable relative to the baseplate.
[0014] In one aspect, a T-shaped projection may be formed on either
the lateral attachment surface of the lateral component or the
support surface of the baseplate, with a T-shaped groove formed on
the other surface, i.e., the surface without the T-shaped
projection. The T-shaped projection may be sized and positioned to
cooperate with said T-shaped groove to form a securement mechanism
when the lateral attachment surface of the lateral component is
slidingly secured to the support surface of the baseplate, with the
securement mechanism allowing translation of the lateral component
in an anterior direction and a posterior direction,
[0015] In another aspect, the baseplate may include a first
baseplate shoulder formed on the support surface, and the lateral
component may include a first lateral component shoulder formed on
the lateral attachment surface. The first baseplate shoulder and
the first lateral component shoulder may cooperate to limit either
anterior translation or posterior translation of the lateral
component.
[0016] In yet another aspect, the prosthetic knee system may
include a first prosthetic ligament with an elongate body, a first
end, and a second end, with the first end and the second end
attachable to the tibial component. The femoral component may
include a crossbar disposed between the medial condyle and the
lateral condyle, with the elongate body of the first prosthetic
ligament wrapped around the crossbar to couple the femoral
component to the tibial component,
[0017] In another form thereof, the present invention provides a
prosthetic knee system includes a femoral component, a tibial
component and a first prosthetic ligament. The femoral component
has a lateral condyle and a medial condyle, and defines at least
one femoral attachment point. The tibial component has a lateral
articulating surface and a medial articulating surface, and defines
at least one tibial attachment point. The first prosthetic ligament
having an elongate body, a first end, and a second end, with the
first end attachable to the femoral attachment point of the femoral
component and the second end attachable to the tibial attachment
point of the tibial component, so that the femoral component is
coupled with the tibial component when the first prosthetic
ligament is attached to the femoral attachment point and the tibial
attachment point.
[0018] In one aspect, a second prosthetic ligament, or a plurality
of prosthetic ligaments may be provided to extend between posterior
and/or anterior attachment points on the tibial component and
lateral and/or medial attachment points on the femoral component.
In another aspect, means for severing the prosthetic ligament may
be provided, such as a pair of cooperating magnets disposed a first
end and a second end of the prosthetic ligament, a weakened portion
along a portion of the elongate body of the first prosthetic
ligament, and/or a connection between the prosthetic ligament and
the femoral component or the tibial component.
[0019] In yet another form thereof, the present invention provides
a method of intraoperatively defining tension between components of
a prosthetic knee system, the method including: providing a femoral
component having a lateral condyle and a medial condyle, the
femoral component defining at least one femoral attachment point;
providing a tibial component having a lateral articulating surface
and a medial articulating surface, the tibial component defining at
least one tibial attachment point; attaching a first end of a
prosthetic ligament to the femoral attachment point of the femoral
component; attaching a second end of the prosthetic ligament to the
tibial attachment point of the tibial component; and selecting a
tension of the prosthetic ligament.
[0020] In one aspect, a plurality of prosthetic ligaments may have
first ends attached to respective femoral attachment points, and
the plurality of prosthetic ligaments may have second ends attached
to respective tibial attachment points. In another aspect, a
provisional prosthetic ligament may be attached to the femoral
attachment point and tibial attachment point before the prosthetic
ligament is attached and a tension thereof is selected. A tension
in the provisional prosthetic ligament may be measured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following descriptions of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0022] FIG. 1 is a perspective view of a tibial component and
femoral component of a total knee arthroplasty system;
[0023] FIG. 2 is an elevational view of the total knee arthroplasty
system of FIG. 1;
[0024] FIG. 3 is a perspective view of the tibial component of the
total knee arthroplasty system of FIG. 1;
[0025] FIG. 4 is a cross-sectional view of the total knee
arthroplasty system of FIG. 1, taken along line 4-4 of FIG. 1;
[0026] FIG. 5 is an elevational view of a tibial component
according to another exemplary embodiment;
[0027] FIG. 6 is a cross-sectional view of the tibial component of
FIG. 5 taken along line 6-6 of FIG. 5;
[0028] FIG. 7 is a cross-sectional view of a total knee
arthroplasty system depicting a femoral component at 90 degrees of
flexion with respect to the tibial component, wherein the
cross-section is taken in a medial/lateral direction that is
slightly posterior relative to the total knee arthroplasty system,
and in which prosthetic ligaments according to an exemplary
embodiment are also depicted;
[0029] FIG. 8 is a cross-sectional, plan view of a femoral
component according to another exemplary embodiment depicting a
plurality of prosthetic ligaments connected thereto;
[0030] FIG. 9A is a plan view of tibial component according to
another exemplary embodiment depicting a plurality of prosthetic
ligaments connected to anterior and posterior sides thereof;
[0031] FIG. 9B is a plan view of tibial component according to
another exemplary embodiment depicting a plurality of prosthetic
ligaments connected to a posterior side thereof;
[0032] FIG. 10 is a cross-sectional view of a total knee
arthroplasty system according to an exemplary embodiment depicting
the femoral component in 90.degree. of flexion with respect to the
tibial component, wherein the cross-section is taken in a
medial/lateral direction that is slightly posterior relative to the
total knee arthroplasty system, and in which prosthetic ligaments
according to another exemplary embodiment are also depicted;
[0033] FIG. 11 is a fragmentary cross-sectional view of the total
knee arthroplasty system of FIG. 10 taken along line 11-11 of FIG.
10; and
[0034] FIG. 12 is a cross-sectional view of a total knee
arthroplasty system according to another exemplary embodiment
depicting a femoral component at 90 degrees of flexion with respect
to the tibial component, wherein the cross-section is taken in a
medial/lateral direction that is slightly posterior relative to the
total knee arthroplasty system, and in which provisional prosthetic
ligaments according to an exemplary embodiment are also
depicted.
[0035] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate preferred embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION
[0036] Referring to FIG. 1, total knee arthroplasty system 10 is
shown including femoral component 12 and tibial component 14.
Femoral component 12 includes anterior flange 16 and opposing
condyles 18, 20, that extend from anterior flange 16. As shown in
FIG. 1, total knee arthroplasty system 10 is configured for use in
a left knee and, as such, condyle 18 is a lateral condyle and
condyle 20 is a medial condyle. However, the principles of the
present disclosure are equally applicable to a right or left knee.
Extending between opposing condyles 18, 20 is crossbar 22. Crossbar
22 is secured to opposing condyles 18, 20 by base 24 and is
designed to receive prosthetic ligament 26 therearound, as defined
in detail below. Crossbar 22 may also be integrally formed in base
24, for example.
[0037] Tibial component 14 includes stem or keel 28 connected to
baseplate 30. Tibial component 14 is configured for securement to a
resected proximal tibia, such that stem or keel 28 is received
within the resected proximal tibia and baseplate 30 sits atop the
resected proximal tibia. Extending upward from baseplate 30 is
projection 32 that extends in an anterior/posterior direction
across tibial component 14 and defines opposing medial and lateral
sides of tibial component 14. Projection 32 includes attachment
points 34, 36 for receipt of opposing ends of prosthetic ligament
26. When prosthetic ligament 26 is wrapped around crossbar 22 as
shown in FIG. 4, affixing ligament 26 to projection 32 via
attachment points 34, 36 secures femoral component 12 to tibial
component 14. Attachment points 34, 36 may include an adhesive,
such as bone cement, to affix ligament 26 to projection 32.
However, as described in detail below, various securement methods
are available to provide proper affixation of ligament 26 to tibial
component 14, as well as to impart a desired tension between
femoral component 12 and tibial component 14. For example, multiple
prosthetic ligaments 26 may be secured to femoral component 12 to
achieve a desired tension between femoral component 12 and tibial
component 14. The length of prosthetic ligament 26 may also be
varied.
[0038] Lateral and medial bearing components 38, 40, respectively,
are positioned atop and secured to baseplate 30. Lateral and medial
components 38, 40 define articulating surfaces 42, 44,
respectively, that cooperate with condyles 18, 20 of femoral
component 12 during knee articulation. In one exemplary embodiment,
medial bearing component 40 is fixedly secured to tibial baseplate
30, such as by a snap-fit, to form a fixed medial component. Thus,
in this embodiment, medial component 40, once secured to baseplate
30, is substantially prevented from moving relative to baseplate
30. In contrast, lateral bearing component 38 is secured to
baseplate 30 to form a mobile bearing component. Thus, in this
embodiment, lateral component 38 is moveable relative to baseplate
30 to encourage normal articulation and relative rotation between
femoral component 12 and tibial component 14.
[0039] Specifically, in a normal knee joint, the femur rotates
about a point that is medially offset, i.e., a point that is on the
medial side of the knee joint, as the knee joint transitions
between flexion and extension. As a result, lateral condyle 18 of
femoral component 12 travels a substantially greater arcuate
distance than medial condyle 20 of femoral component 12 along a
plane extending across the proximal end of the resected proximal
tibia as the knee travels between various stages of flexion and
extension. In the illustrated embodiment of FIGS. 1-3, lateral
condyle 18 is substantially symmetrical to medial condyle 20 in
femoral component 12, and lateral component 38 is substantially
symmetrical to medial component 40 in tibial. component 14. The
larger distance traveled by lateral condyle 18 is facilitated by
fixing medial component 40 and allowing lateral component 38 to
move, as described below. However, it is also within the scope of
the present disclosure that asymmetrical tibial and/or femoral
components may be used, such as by using relatively larger
articulating surfaces on the lateral portions of the
components.
[0040] As indicated above, medial component 40 of tibial component
14 is a fixed bearing component. For example, in one exemplary
embodiment, articulating surface 44 may be a highly conforming
articulating surface, meaning surface 44 is highly congruent with a
mating structure such as medial condyle 20. As a highly conforming
articular surface, articulating surface 44 has a concave shape that
substantially corresponds to the convex shape of the articulating
surface of medial condyle 20 of femoral component 12. As a result,
the anterior and posterior movement of medial condyle 20 is
controlled, while allowing for rotation of femoral component 12
atop articulating surface 44 of medial condyle 20. In this manner,
the natural movement of an anatomic medial condyle with respect to
an anatomic tibia is replicated by medial condyle 20 and medial
component 40.
[0041] In contrast to medial component 40 of tibial component 14,
lateral component 38 of tibial component 14 is a mobile bearing
component. For example, in one exemplary embodiment, lateral
component 38 may be advanced anteriorly as femoral component 12
transitions from extension into flexion and, correspondingly,
lateral component 38 may be advanced posteriorly as femoral
component 12 transitions from flexion into extension. Articulating
surface 42 may be a less conforming articulating surface as
compared to articulating surface 44, meaning articulating surface
42 is somewhat less congruent with the mating lateral condyle 18.
As a less conforming articular surface, articulating surface 42 has
a concave shape that defines a larger radial profile than lateral
condyle 18 of femoral component 12. This reduced congruence allows
some anterior and posterior movement of lateral condyle 18 within
lateral component 38, consistent with the natural movement of an
anatomic lateral condyle with respect to an anatomic tibia.
Although conformity is somewhat reduced, articulating surface 42
and lateral condyle 18 still sufficiently conform to facilitate
transmission of force from lateral condyle 18 to lateral component
38, with the transmitted force sufficient to drive the anterior and
posterior motion of lateral component 38. Alternatively,
articulating surface 42 may be a highly conforming surface similar
to articulating surface 44.
[0042] In one exemplary embodiment, shown in FIGS. 1-3, an anterior
stop is provided to prevent lateral component 38 from subluxing
anteriorally. In this embodiment, baseplate 30 includes a stepped
portion that defines shoulder 46, while lateral component 38
includes a corresponding stepped portion that defines shoulder 48.
As lateral component 38 is advanced anteriorally, shoulder 48 of
lateral component 38 contacts shoulder 46 of baseplate 30 to
prevent additional anterior movement of lateral component 38
relative to baseplate 30. Once in this position, additional flexion
of femoral component 12 may result in femoral roll-off, i.e.,
additional movement of lateral condyle 18 in a posterior direction
away from lateral component 38 of tibial component 14.
Advantageously, by allowing for femoral roll-off of lateral condyle
18, total knee prosthesis system 10 more accurately replicates the
natural articulation of a knee joint. To maintain the overall
stability of knee arthroplasty system 10 during femoral roll-off,
lateral component 38 may include a convex portion at a posterior
end thereof which is adapted to cooperate with a concave posterior
end formed in lateral condyle 18 during deep flexion. One exemplary
knee implant with such cooperating convex and concave portions is
described in a U.S. Patent Application entitled LATERAL CONDYLE
POSTERIOR INFLECTION FOR TOTAL KNEE IMPLANT (Attorney Docket
ZIM0730), filed on even date herewith, the disclosure of which is
hereby incorporated by reference herein in its entirety.
[0043] In order to secure lateral component 38 to baseplate 30,
baseplate 30 may, in one exemplary embodiment, include projection
50 having a T-shaped cross-section that is received within a
corresponding groove 52 formed in lateral component 38. Due to the
interaction of projection 50 with the portion of lateral component
38 defining groove 52, lateral component 38 may move anteriorly and
posteriorly in the direction of double-headed arrow A of FIG. 3,
but is prevented from substantial movement in a medial or lateral
direction. In other exemplary embodiments, projection 50 and groove
52 may be arcuate to allow for lateral component 38 and
correspondingly condyle 18 to move along an arcuate path that has
an axis of rotation that is medially offset within respect to the
knee joint to further replicate the natural, anatomical
articulation of the knee joint.
[0044] Referring to FIGS. 5 and 6, another exemplary embodiment of
tibial component 14 is shown as tibial component 54. Tibial
component 54 is substantially similar to tibial component 14 and
corresponding reference characters have been used to identify
identical or substantially identical parts therebetween. Referring
to FIG. 5, lateral component 55 of tibial component 54 includes
internal groove 56, shown in dashed lines in FIG. 5, that allows
for lateral component 55 of tibial component 54 to be snap-fit or
otherwise secured to projection 58 of tibial baseplate 60. In this
embodiment, movement of lateral component 55 relative to tibial
baseplate 60 is constrained only by the interaction of internal
side wails 61 and end walls 63, shown in dashed lines in FIG. 5,
that define groove 52 with projection 58. For example,
medial/lateral movement of lateral component 55 is substantially
prevented by the interaction of sidewalls 61, shown in FIG. 6, with
projection 58. However, because projection 58 has a length that i
less than the length of groove 52, lateral component 55 may move in
an anterior/posterior direction until one of end walls 63 that
define groove 52 contact a corresponding end of projection 58. As a
result of the increased length of groove 52 relative to projection
58, lateral component 55 of tibial component 54 may be configured
to be advanced substantially further in an anterior direction than
lateral component 38 of tibial component 14.
[0045] Additionally, due to the ability to configure lateral
component 55 to move further in an anterior direction than lateral
component 38, a highly conforming articulating surface may be
formed on lateral component 55. In this embodiment, as condyle 18
of femoral component 12 moves in a posterior direction as the knee
joint transitions from extension to flexion, lateral component 55
would move in a posterior direction with condyle 18. Similarly, as
condyle 18 of femoral component 12 moves in an anterior direction
as the knee joint transitions from flexion to extension, lateral
component 55 would move in an anterior direction with condyle 18.
By having lateral component 55 of tibial component 54 move with
condyle 18 of femoral component 12, condyle 18 may advance further
in a posterior direction than can be achieved with known femoral
components.
[0046] In yet another exemplary embodiment (not shown), a lateral
component similar to lateral components 42, 55 may not have any
restriction on movement in the anterior or posterior directions.
Thus, the lateral component may he adapted to slide in a linear or
arcuate path without any shoulders or end walls preventing the
lateral component from further motion along the path.
[0047] As discussed in detail above, prosthetic ligament 26, shown
in FIGS. 1 and 4, may be secured to femoral component 12 and tibial
component 14. By utilizing prosthetic ligament 26, movement of
femoral component 12 and tibial component 14 relative to one
another is restricted. The specific restriction in the movement of
femoral component 12 and tibial component 14 relative to one
another that is created by prosthetic ligament 26 may be designed
to replicate the restrictions imposed on movement of a natural knee
joint by the cruciate ligaments. However, as shown in FIG. 2, knee
arthroplasty system 10 may also be used without prosthetic ligament
26.
[0048] In still another alternative, only one of the two cruciate
ligaments in a natural knee is replicated using prosthetic ligament
26. For example, a partial or total knee arthroplasty may utilize
fixed medial component 40 and/or mobile lateral component 38, while
still retaining one or both of the natural cruciate ligaments. In
one exemplary embodiment shown in FIG. 9B, tibial component 14 may
be designed for surgeries in which both the posterior cruciate
ligament (PCL) and the anterior cruciate ligament (ACL) are
resected, but only the PCL is replaced with one or more prosthetic
ligaments 26. In this "cruciate retaining" design, lateral
component 40 and medial component 38 may be joined by bridge 39.
Alternatively, a partial knee arthroplasty may be performed in
which only a single side of the natural tibial plateau is replaced,
so that either medial component 40 or lateral component 38 may be
used to replace a resected articular surface on the medial or
lateral side of the tibia, respectively.
[0049] In another exemplary embodiment, shown in FIG. 7, a pair of
prosthetic ligaments 62 is shown. Referring to FIG. 7, each of
prosthetic ligaments 62 includes opposing spherical heads 66 and
elongate body 68 extending between opposing heads 66. In an
exemplary embodiment, spherical heads 66 are resiliently deformable
and are sized to be received within corresponding spherical grooves
70 provided at attachment points 72, 74 that may formed on tibial
component 14 and femoral component 12, respectively. The spherical
shape of heads 66 and grooves 70 allow heads 66 to articulate with
grooves 70 as femoral component 12 and tibial component 14 move
relative to one another. By securing prosthetic ligaments 62 to
femoral component 12 and tibial component 14, as shown in FIG. 7,
the function of the anterior and posterior cruciate ligaments may
be replicated by prosthetic ligaments 62. However, heads 66 may be
rigid or non-resilient, and need not articulate with attachment
points 72, 74. For example, heads 66 may be formed of a solid
material, and/or may be fixedly or permanently attached to
attachment points 72, 74. For example, in some embodiments,
prosthetic ligaments 62 may be sufficiently flexible to obviate the
benefits of spherical heads 66 and spherical grooves 70.
[0050] As shown in FIG. 7, attachment points 72 of tibial component
14 are spaced apart from one another in both an anterior/posterior
dimension and a medial/lateral dimension. Thus, in one exemplary
embodiment, the anterior most attachment point 72 is positioned on
the lateral side of tibial component 14, while the posterior most
attachment point 72 is positioned on the medial side of tibial
component 14. Referring to attachment points 74 on femoral
component 12, attachment points 74 are formed in opposing lateral
and medial condyles 18, 20.
[0051] In one exemplary embodiment, ligaments 62 are formed as
solid, flexible ligaments. In one exemplary embodiment, a plurality
of ligaments 62 each having a different stiffness is provided. By
providing a plurality of ligaments 62 each having a different
stiffness, a surgeon may select an appropriate stiffness of
ligaments 62 to create a condition in which their crossing
interactions drive axial rotation of a femoral component upon a
tibial component during knee articulation. Moreover, ligaments 62
can be selected based on a variety of ligament material properties
to provide optimal joint kinematics and soft tissue balance, as
discussed in detail below.
[0052] In another exemplary embodiment, a locking mechanism (not
shown) may be attached to femoral component 12 and/or tibial
component 14 to lock spherical heads 66 of prosthetic ligaments 62
in position within spherical grooves 70. Additionally, while
described as having spherical head 66 and elongate body 68,
prosthetic ligaments 62 may be connected to femoral component 12
and tibial component 14 in any suitable manner.
[0053] Additionally, in order to replicate the function of
individual natural cruciate ligaments, a plurality of prosthetic
ligaments 62 may be used. This provides the surgeon with an
increased ability to reconstitute the function of the natural
cruciate ligaments, such as by adjusting the flexion/extension
balance of the knee joint and/or the anterior/posterior contact
point of femoral component 12 on tibial component 14. By using
multiple ligaments, the natural structure and function of the
natural anterior cruciate ligament (ACL) and/or posterior cruciate
ligament (PCL) is more closely approximated, with different fibers
potentially supporting loads that vary throughout the range of
motion.
[0054] Referring to FIGS. 8 and 9A, a plurality of attachment
points 72, 74 are shown on tibial component 14 and femoral
component 12. In use, a surgeon may attach one of spherical heads
66 of a first ligament 62 to one of attachment points 74 on femoral
component 12 and then attach the opposing spherical head 66 to one
of attachment points 72 on tibial component 14. Then, the surgeon
may trial the knee joint, i.e., actuate the patient's knee joint
through flexion and extension. Based on the surgeon's observations
during the trialing, the surgeon may determine that use of a
different attachment point 72, 74 for at least one of spherical
heads 66 of one of ligaments 62 may provide a more natural,
anatomical articulation of the knee joint for an individual patient
or that the use of an additional prosthetic ligament 62 may be
advantageous.
[0055] If the surgeon does determine that a different attachment
point 72, 74 would be beneficial for the patient, the surgeon may
then remove one of spherical heads 66 of one of prosthetic
ligaments 62 from its attachment point 72, 74 and position it
within another attachment point 72, 74. The range of motion,
testing may then be repeated to determine if a proper
flexion/extension balance of the knee joint and/or the
anterior/posterior contact point of femoral component 12 on tibial
component 14 has been achieved. If the articulation of the knee
joint is still not satisfactory to the surgeon, one of spherical
heads 66 may be removed by attachment points 72, 74 and placed at
another of attachment points 72, 74. This process may be repeated
as necessary until the surgeon has found positions for ligaments 26
that most accurately replicates the natural, anatomical
articulation of the knee joint. The illustrated embodiment of FIGS.
8 and 9A show attachment points 72, 74 for prosthetic ligaments 62
arranged in a similar fashion to the arrangement of natural
anatomic ligaments. However, the orientation of attachment points
can have different patterns or orientations within the scope of the
present disclosure, such as an orientation that is a reverse or
mirror of the illustrated orientation.
[0056] In another exemplary embodiment (not shown), a prosthetic
ligament may be provided that includes a central body portion with
a plurality of necks extending from the central body portion, such
as in a "Y" configuration where two necks extend from the central
body portion or a "pitchfork" configuration where three necks
extend from the central body portion. In addition, each of the
necks may terminate at a spherical head 66, which may be secured to
one of attachment points 72, 74 in a substantially similar manner
as described in detail above with respect to prosthetic ligaments
62. Additionally, in this embodiment, the prosthetic ligament may
be attached at a plurality of attachment points 72, 74 on each of
and/or one of femoral component 12 and tibial component 14. In this
manner, additional variability may be introduced into total knee
prosthesis system 10 to allow for a more precise adjustment of the
articulation of the knee joint, as discussed below.
[0057] Referring to FIGS. 10 and 11, another exemplary embodiment
of prosthetic ligaments 62 are shown as prosthetic ligaments 76.
Prosthetic ligaments 76 may be substantially permanently secured to
dovetail inserts 78, 80. Dovetail inserts 78, 80 are configured to
be received in corresponding dovetail grooves 82, 84, formed in
tibial component 14 and femoral component 12, respectively. In this
manner, prosthetic ligaments 76 may be preattached and readily
positioned within or removed from femoral prosthesis system 10. In
another exemplary embodiment, prosthetic ligaments 76 are not
substantially permanently attached, but are readily removable from
dovetail inserts 78, 80. In this embodiment, prosthetic ligaments
76 may be removed from and/or added to dovetail inserts 78, 80 to
provide a desired configuration for an individual patient's knee
joint. For example, a plurality of prosthetic ligaments 76 may be
provided in which each prosthetic ligament 76 has a different
characteristic or a combination of different characteristics. For
example, each prosthetic ligament 76 may have a different stiffness
and/or different length than other prosthetic ligaments 76, or may
be made of a different material. In this manner, a surgeon may
select a prosthetic ligament 76 that has the characteristics that
allows for the most accurate replication of the natural, anatomical
articulation of the patient's knee joint.
[0058] While described in detail above as having a specific design,
including spherical heads and elongate bodies, prosthetic ligaments
26, 62, 76, may take a number of different forms. For example,
instead of being formed as a solid, flexible prosthetic ligament
and providing a variety of different thicknesses, prosthetic
ligaments 26, 62, 76 may be woven or rope-like in order to
determine the passive envelope of soft tissue in the knee joint and
to provide anterior/posterior translation limits for the femur upon
the tibia.
[0059] Additionally, variable properties of prosthetic ligaments
26, 62, 76 may be manipulated to allow the surgeon to optimize the
kinematics and feel of the knee prosthesis, e.g., by providing
tight ligaments for joint stability and loose ligaments for joint
laxity. Examples of such properties include: the number of
prosthetic ligament strands in a multi-strand design; the size or
diameter of prosthetic ligament strands; the material from which
the prosthetic ligament is made; the length and/or tension of the
prosthetic ligament within the knee prosthesis; the orientation of
fibers relative to one another, i.e. a "Y" oriented fiber as
discussed above; and the location of attachment of prosthetic
ligament strands, also discussed above. The surgeon may vary these
or other characteristics of prosthetic ligaments 26, 62, 76 for an
individual patient to better match the needs of the patient, and to
compensate for differently shaped femurs, different genders,
different expected level of athletic abilities and activities,
and/or different ages between patients.
[0060] Moreover, varying the properties of prosthetic ligaments 26,
62, 76 provides an opportunity for the surgeon to balance the soft
tissues of the knee, and to reproduce as closely as possible the
function of the natural cruciate ligaments. Further, several
ligament properties can be varied intra-operatively. For example, a
surgeon may vary the lengths of prosthetic ligaments 26, 62, 76 at
the time of implantation, such as by trimming a portion of the
ligament to create the desired length and tension. A cut-to-length
prosthetic ligament 26, 62, 76 may be pre-attached to either
femoral component 12 or tibial component 14, so that only one end
of prosthetic ligament needs to be cut to length upon attachment to
the other component. Similarly, in the multi-strand design shown in
FIGS. 8 and 9A, strands having different properties can be added,
removed or substituted until the desired soft tissue balance and
joint kinematics are achieved.
[0061] Referring to FIG. 12, provisional prosthetic ligaments 86
are shown. Provisional prosthetic ligaments 86, 88 are
substantially similar to prosthetic ligaments 62, and corresponding
reference numerals have been used to identify identical or
substantially identical parts therebetween. As shown in FIG. 12,
elongate bodies 68 of provisional prosthetic ligaments 86 are
divided into two individual sections connected to one another by
opposing attractive magnets 90, 92. In this embodiment, the force
required to separate magnets 90, 92 is known and is selected to be
at a level above which the total knee arthroplasty system 10 would
be considered to be too tight during articulation. Thus, if system
10 is too tight, then, during range of motion testing, magnets 90,
92 will separate from one another and provide immediate visual and
tactile feedback to a surgeon indicating that the knee joint is too
tight.
[0062] As an alternative to magnets 90, 92, provisional prosthetic
ligaments 86 may be designed such that elongate bodies 68 fail upon
the application of a force in excess of a predetermined limit,
either along the extent of elongate body 68 or at one end thereof
For example, elongate body 68 may have a weakened portion of known
failure strength, or the entirety of elongate body 68 may have a
known failure strength. Alternatively, the moorings between
elongate body 68 and femoral component 12 and/or tibial component
14 (such as at spherical heads 66) may have a weakened portion or
known failure strength. Thus, if the joint is too tight, elongate
bodies 68 of provisional prosthetic ligaments 86 will fail by
either breaking or releasing from their moorings on femoral
component 12 and/or tibial component 14, which will also provide
immediate visual and tactile feedback to the surgeon indicating
that the joint is too tight. Prosthetic ligaments 86 utilizing
magnets or breakage allow an indirect measurement of tension
therein, in that an unbroken prosthetic ligament signifies that
tension is below the breakage threshold and a broken prosthetic
ligament signifies a tension above the breakage threshold.
[0063] A further alternative for provisional prosthetic ligaments
68 may include coupling instrumentation to one or more of ligaments
68 to provide data feedback on the level of strain and/or force
being experienced by ligaments 68. For example, a strain gauge may
be coupled to a provisional prosthetic ligament 68 of known
elasticity, so that a given increase in length of the strain gauge
is known to correspond to a given force. Prosthetic ligaments 86
utilizing data feedback allow direct measurement of tension
therein, so that the tension at any given flexion may be
measured.
[0064] White this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *