U.S. patent application number 10/185492 was filed with the patent office on 2004-01-01 for modular knee joint prosthesis.
Invention is credited to Wyss, Joseph.
Application Number | 20040002767 10/185492 |
Document ID | / |
Family ID | 29718002 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040002767 |
Kind Code |
A1 |
Wyss, Joseph |
January 1, 2004 |
Modular knee joint prosthesis
Abstract
A knee joint prosthesis includes a femoral component for
engaging the femur having an articular surface and a recess within
the articular surface, and a tibial component for engaging the
tibia with a bore, and a meniscal component comprising a rotation
pin configured for rotatable mounting within the bore of the tibial
component. The meniscal component also includes a bearing surface
for sliding contact with the articular surface of the femoral
component and an elongated channel defined amid the bearing
surface. A stabilizing post is provided that includes a base
slidably mounted with the elongated channel and a spine post
projecting from the base through the channel and into the recess
when the articular surface is in contact with said bearing surface.
The stabilizing post thus slides within the channel when contacted
by the interior of the recess in the femoral component. In a method
of the invention, a plurality of stabilizing posts can be provided
for temporary mounting within the channel. A stabilizing post can
be selected that provides an optimum joint movement.
Inventors: |
Wyss, Joseph; (Fort Wayne,
IN) |
Correspondence
Address: |
Paul J. Maginot
Maginot, Moore & Bowman
Bank One Center/Tower
111 Monument Circle, Suite 3000
Indianapolis
IN
46204-5115
US
|
Family ID: |
29718002 |
Appl. No.: |
10/185492 |
Filed: |
June 28, 2002 |
Current U.S.
Class: |
623/20.27 ;
623/20.29 |
Current CPC
Class: |
A61F 2/3868 20130101;
A61F 2/3886 20130101 |
Class at
Publication: |
623/20.27 ;
623/20.29 |
International
Class: |
A61F 002/38 |
Claims
What is claimed is:
1. A joint prosthesis comprising: a first joint component having a
bone engaging portion, an articular surface, and a recess defined
within said articular surface; a mating component having a bone
engaging portion and defining a bearing surface for sliding contact
with said articular surface of said first joint component; and a
stabilizing post slidably mounted to said mating component amid
said bearing surface, said post projecting from said mating
component and into said recess when said articular surface is in
contact with said bearing surface.
2. The joint prosthesis of claim 1, wherein said mating component
includes: a second joint component including the bone engaging
portion; and an intermediate component connected to said second
joint component, said intermediate component including said bearing
surface.
3. The joint prosthesis of claim 2, wherein: said second joint
component defines a bore; and said intermediate component includes
a pin sized to be received within said bore.
4. The joint prosthesis of claim 3, wherein said bore and said pin
are configured to permit relative rotation therebetween when said
pin is received within said bore.
5. The joint prosthesis of claim 1, wherein: said mating component
defines an elongated channel; and said stabilizing post includes a
base configured for sliding engagement within said channel and a
spine projecting from said base through said channel and into said
recess when said articular surface is in contact with said bearing
surface.
6. The joint prosthesis of claim 5, wherein: said channel is open
at one end; and said mating component includes a locking member
configured to close said one end with said base of said stabilizing
post disposed within said channel.
7. The joint prosthesis of claim 6, wherein said locking member is
configured for a press-fit within said channel.
8. The joint prosthesis of claim 6, wherein: said channel includes
an enlarged groove at opposite sides of said channel, said base is
configured for sliding engagement within said grooves; and said
locking component is configured for locking engagement within said
grooves.
9. The joint prosthesis of claim 6, wherein said locking member is
selectable from a plurality of locking members having different
lengths when disposed within said channel.
10. The joint prosthesis of claim 5, wherein: said channel includes
an enlarged groove at opposite sides of said channel; and said base
is configured for sliding engagement within said grooves with said
spine projecting through said channel.
11. The joint prosthesis of claim 10, wherein said base has a
length and said channel has a length greater than the length of
said base.
12. The joint prosthesis of claim 1, wherein said stabilizing post
is selectable from a plurality of stabilizing posts having
different profiles.
13. The joint prosthesis of claim 1, wherein: said recess includes
surfaces at its opposite ends; said stabilizing post includes a
face opposing one of said opposite end surfaces; and said face and
said one of said opposite end surfaces are configured to provide a
camming movement of said stabilizing post as said one of said
opposite end surfaces moves in contact with said face.
14. The joint prosthesis of claim 13, wherein: said stabilizing
post includes an opposite face opposing the other of said opposite
end surfaces; and said opposite face and the other of said opposite
end surfaces are configured to provide a camming movement of said
stabilizing post as said other of said opposite end surfaces moves
in contact with said opposite face.
15. The joint prosthesis of claim 14, wherein said face and said
opposite face are differently curved.
16. In a prosthetic knee joint having a femoral component with
femur engaging portion, an articular surface and a recess within
the articular surface, and a tibial component with a tibia engaging
portion and a bore, a meniscal component comprising: a rotation pin
configured for rotatable mounting within the bore of the tibial
component; a bearing surface for sliding contact with the articular
surface of the femoral component; an elongated channel defined amid
said bearing surface; and a stabilizing post including a base
slidably mounted with said elongated channel and a spine post
projecting from said base through said channel and into the recess
when the articular surface is in contact with said bearing
surface.
17. The meniscal component of claim 16, wherein: said channel has
an open end; and said meniscal component further comprises a
locking member configured for locking engagement at said open end
of said channel to trap said stabilizing post within said
channel.
18. A method for fitting a prosthetic joint to a patient comprising
the steps of: engaging a first component to a first bone of the
patient, the first component having an articular surface and a
recess defined within said articular surface; engaging a mating
component to a second bone of the patient, the mating defining a
bearing surface for sliding contact with the articular surface of
the first component; selecting one of a plurality of stabilizing
posts; slidably mounting the selected stabilizing post to the
mating component amid the bearing surface with the post projecting
from the mating component and into the recess when the articular
surface is in contact with the bearing surface; evaluating the
movement of the prosthetic joint in situ; and replacing the
selected stabilizing post with another stabilizing post from the
plurality of posts to optimize the movement of the joint.
19. The method of claim 18, wherein: the mating component defines a
channel having an open end; and the method further comprises the
step of closing the open end when a stabilizing post has been
selected to optimize the movement of the joint.
20. The method of claim 18, wherein: the mating component includes
a second component and an intermediate component; and the step of
engaging a mating component includes engaging the second component
to the second bone and rotatably mounting the intermediate
component to the second component.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to prosthetic joints, and
particularly to a prosthesis for the knee joint.
[0002] Implantable knee prostheses for diseased and/or damaged
knees typically include three components, namely a femoral
component, a tibial component and a meniscal component. The femoral
component may also include a patellar element, or a separate
patellar component may be provided. The prosthesis components are
generally configured to restore or emulate as much of the natural
motion of the knee joint as possible. The selection of the
particular prosthesis components is usually dictated by the
condition of the patient's knee. For instance, the condition of the
distal end of the femur and proximal end of the tibia, as well as
the patency of the surrounding ligaments and soft tissue can affect
the form of the joint prosthesis.
[0003] Generally, a total knee joint replacement includes a tibial
component having a platform portion which replaces the entire
superior surface of the tibial plateau and substitutes for the
tibial condylar surfaces. The femoral component also includes
laterally-spaced condylar portions joined by an intercondylar
bridge and a patellar surface.
[0004] The tibial component typically includes a tibial tray and
stem for surgical attachment to the proximal end of the tibia. The
component also includes an intermediate articulating surface member
that is connected to the tibial tray. The intermediate member
defines a bearing surface for articulation of the femoral component
thereon. The mating surfaces are smoothly curved in the
anterior-posterior (AP) direction to generally match the lateral
profile of the natural femoral and tibial condyles, and to
ultimately replicate the normal joint movement.
[0005] This normal joint movement includes a translational
component in the AP direction, as well as a rolling of the femoral
condyles on the tibial condyles when the knee is flexed. In
addition, the natural tibia is capable of rotation relative to the
femur about the axis of the tibia. Thus, an ideal knee prosthesis
will be able to achieve all three degrees of freedom of movement.
In some cases, the patient's knee lacks adequate posterior support
due to a deficient posterior cruciate ligament. In these cases, the
modular knee is preferably posteriorly stabilized, meaning that
posterior movement of the tibia relative to the femur is
restricted. This posterior stabilization can be achieved in a
typical implant by a projection or eminence on the tibial insert
that engages a box-like intercondylar portion of the femoral
component. Intact collateral ligaments keep the projection within
the box-like portion as the knee is flexed to inhibit dislocation
of the joint at hyper-extension or hyper-flexion.
[0006] In order to increase the lifetime of the prosthetic knee
joint, the mating bearing surfaces between the tibial and femoral
components generally permit a combination of rolling and
translational movement as the knee joint is flexed. These two
degrees of freedom of movement change the direction of forces
between the two components so the force transmitted through the
joint is not focused on one location. In response to this optimum
design aspect, some prosthetic knees include a translating
intermediate bearing component. One problem with modular implants
of this type is that the articulating and sliding components can be
exposed to the soft tissue surrounding the joint.
SUMMARY OF THE INVENTION
[0007] In one embodiment of the invention, a modular joint
prosthesis comprises a first joint component having a bone engaging
portion, an articular surface, and a recess defined within the
articular surface. The prosthesis further includes a mating
component having a bone engaging portion and defining a bearing
surface for sliding contact with the articular surface of the first
joint component. In one feature of the invention, a stabilizing
post is slidably mounted to the mating component amid the bearing
surface with the post projecting from the mating component and into
the recess when the articular surface is in contact with the
bearing surface.
[0008] In certain embodiments, the mating component includes a
second joint component including the bone engaging portion and an
intermediate component connected to the second joint component, the
intermediate component including the bearing surface. When the
modular joint prosthesis is a total knee prosthesis, the first
component is the femoral component, the second component is the
tibial component and the intermediate is the meniscal
component.
[0009] The second joint component can define a bore, while the
intermediate component can includes a pin sized to be received
within the bore. The bore and pin can be configured to permit
relative rotation therebetween when the pin is received within the
bore to add a rotational degree of freedom between the femoral and
tibial components.
[0010] In one aspect of the invention, the mating component or the
intermediate component defines an elongated channel. The
stabilizing post includes a base configured for sliding engagement
within the channel and a spine projecting from the base through the
channel and into the recess when the articular surface is in
contact with the bearing surface. In certain embodiments, the
channel is open at one end. In these embodiments, a locking member
can be provided that is configured to close the one end with the
base of the stabilizing post disposed within the channel. The
locking member can be configured for a press-fit within the
channel.
[0011] In some embodiments, the channel includes an enlarged groove
at opposite sides of the channel. The base of the stabilizing post
can then be configured for sliding engagement within the grooves,
while the locking component can be configured for locking
engagement within the grooves. Preferably, the channel has a length
greater than the length of the base so that the base can translate
within the channel.
[0012] The recess of the first joint component can define surfaces
at its opposite ends. The stabilizing post preferably includes a
face opposing each of the opposite end surfaces. The recess
surfaces and a corresponding opposing face of the stabilizing post
are configured to provide a camming movement of the stabilizing
post as the recess end surface moves in contact with the opposing
face. Thus, as the first joint component rolls and translates
relative to the mating component, the camming movement causes the
stabilizing post to slide between the ends of the channel.
[0013] In some embodiments, two faces of the stabilizing post are
differently curved to provide different camming effects at opposite
ends of the channel. In one feature of these embodiments, a
plurality of stabilizing posts can be provided having different
profiles. An appropriate stabilizing post can be selected during a
total knee procedure to optimize the movement of the resulting
prosthetic joint.
[0014] It is one object of the present invention to provide a
prosthetic joint that permits relative rolling and translation
between two bone engaging components. A further object is achieved
by features of the invention that reduce the exposure of
articulating surfaces and components of the prosthetic joint to
soft tissue surrounding the joint.
[0015] These objects and certain benefits of the invention can be
ascertained from the following written description taken together
with the accompanying figures.
DESCRIPTION OF THE FIGURES
[0016] FIG. 1 is an exploded perspective view of the components of
a joint prosthesis in accordance with one embodiment of the
invention.
[0017] FIG. 2 is a side exploded view of the intermediate component
of the joint prosthesis shown in FIG. 1.
[0018] FIG. 3 is a top elevational view of the intermediate
component shown in FIG. 2.
[0019] FIG. 4 is an end elevational view of the intermediate
component shown in FIG. 2.
[0020] FIG. 5 is a side elevational view of the intermediate
component shown in FIG. 2, with the stabilizing post shown in
different positions.
[0021] FIG. 6 is a side elevational view of the femoral component
of the prosthetic joint shown in FIG. 1.
[0022] FIG. 7 is a side elevational view showing one position of
the femoral component relative to the intermediate component of the
prosthetic joint shown in FIG. 1.
[0023] FIG. 8 is a side elevational view showing another position
of the femoral component relative to the intermediate component of
the prosthetic joint shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and described in the
following written specification. It is understood that no
limitation to the scope of the invention is thereby intended. It is
further understood that the present invention includes any
alterations and modifications to the illustrated embodiments and
includes further applications of the principles of the invention as
would normally occur to one skilled in the art to which this
invention pertains.
[0025] Referring first to FIG. 1, a modular joint prosthesis 10 is
depicted that comprises a first joint component 12, a second joint
component 14 and an intermediate joint component 16. From the
perspective of a knee prosthesis, the first joint component 12 can
be referred to as the femoral component, the second joint component
14 as the tibial component, and the intermediate joint component 16
as the meniscal component.
[0026] The femoral and tibial components can be configured
according to known designs for these elements. For the purposes of
the present disclosure, certain details of these components will be
described. The femoral component 12 can include an articular
surface, or more particularly a pair of condylar articular surfaces
25. These surfaces are smoothly curved and configured to emulate
the shape of the natural femoral condyles. The component 12 also
includes a bone engaging portion 27 which can include fixation
posts 28. The bone engaging portion 27 can be configured in a known
manner for attachment to the distal femur. The femur can be
prepared in a conventional manner to accept the femoral component
12.
[0027] The femoral component 12 can further include a patellar
element 30 that is integral with the articular surfaces 25. A
separate patellar element can also be provided for connection to
the femoral component. The component 12 also includes an
intercondylar recess 32 which is preferably a box-like structure
spanning the AP dimension of the component. A slot 33 can be
included in the proximal face of the recess 32. In one feature of
the femoral component 12 of the present embodiment, a tab 34 can be
provided at the posterior end of the recess 32. The tab 34 can
operate as a control for roll-back of the tibia relative to the
femur as the joint is articulated.
[0028] The tibial component 14 can be in the form of a conventional
tibial tray. The component includes a proximal surface 35 that
parallels the tibial plateau cut into the proximal end of the tibia
to receive the component. A fixation stem 37 projects downwardly
from the tibial tray and is configured for solid, permanent
fixation within the prepared end of the tibia. A connection bore 39
extends from the proximal surface 35 into the fixation stem 37. The
bore is configured to receive a mating stem 45 of the intermediate
joint component 16 in a known fashion. To approximate the shape of
the prepared end of the tibia, the tibial component 14 can define a
posterior recess 41.
[0029] Turning now to the intermediate component 16, details of its
design can be gleaned from FIGS. 1-4. In general, the intermediate
component can be configured like similar components from known
modular knee prostheses. Thus, the intermediate component 16 can
include opposite spaced-apart bearing surfaces 43 that are
configured for articulating contact with the articular surfaces 25
of the femoral component 12. The component 16 can also include a
rotation pin 45 that is rotatably mounted within the connection
bore 39 of the tibial component 14. The interface between the
rotation pin and the tibial component bore can be of conventional
design that permits relative rotation between the intermediate
component 16 and the patient's tibia. In the illustrated
embodiment, the axis of rotation of the intermediate component 16
is at the center of the component and of the tibial component 14;
however, other axes of rotation are contemplated as required for
the particular joint anatomy and the desired movement of the joint
prosthesis.
[0030] In a modification from prior intermediate components, the
component 16 of the present invention includes a channel 47 defined
between the spaced-apart bearing surfaces 43. In general, the
position of the channel 47 corresponds to the position of the
recess 32 of the femoral component 12 when the two components 12
and 16 are in articulating contact. The channel 47 can include a
posterior opening 49 at the posterior side of the intermediate
component 16. A stop surface 51 is provided at the closed anterior
end of the channel 47. Opposite grooves 53 can be formed at the
base of the channel 47 for reasons set forth below. As shown in the
figures, the channel 47 extends substantially along the entire AP
length of the intermediate joint component 16.
[0031] The channel 47 is configured to receive a further novel
component of the prosthesis 10, namely the stabilizing post 18. The
stabilizing post 18 projects upward from the intermediate component
16 to engage the intercondylar recess 32 in the femoral component
12. As best illustrated in FIGS. 1 and 2, the stabilizing post 18
includes a base 55 that is sized for sliding engagement within the
grooves 53 of the channel 47. The base 55 and grooves 53 preferably
form a close running fit so that the stabilizing post 18 can slide
freely within the channel 47 without binding.
[0032] The stabilizing post 18 includes a spine 57 that projects
from the base 55. The spine 57 is sized for sliding movement along
the exposed length of the channel 47 facing the femoral component
recess 32. The spine 57 has a height from the base 55 that is
sufficient to span the height of the recess 32 and extend at least
partially into the slot 33 when the femoral component and
intermediate component are in articulating contact. The spine 57
serves to limit the AP movement of the femoral component 12. In
addition, a close running fit between the spine 57 and the recess
32 helps ensure that the femoral component 12 does not rotate
relative to the intermediate component 16, even when the tibial
component rotates relative to the intermediate component.
[0033] As shown in FIGS. 1-3 and 5, the joint prosthesis also
includes a locking member 20 that closes the posterior opening 49
of the channel 47. Thus, the locking member 20 retains the
stabilizing post 18 within the channel 47. The locking member
includes locking edges 69 on opposite sides of the member that are
configured for locking engagement within the grooves 53 at the
posterior end of the channel 47. The locking edges 69 and grooves
53 can be configured to achieve a variety of locking engagements
therebetween to essentially permanently connect the two parts
together and close the posterior opening of the channel. Thus, in
one embodiment, the locking edges and grooves can form a press-fit
engagement. In a specific embodiment, the press-fit engagement can
be accomplished by complementary Morse taper angles. In another
embodiment, the locking edges and grooves can be configured for a
snap-fit engagement, sock as a locking tab and notch configuration.
In yet another alternative, an independent fixation, such as a
screw of even epoxy, can be used to lock the locking member 20
within the end of the channel.
[0034] The locking member 20 operates to trap the stabilizing post
18 within the channel. Thus, the member includes a stop surface 71
facing the posterior end 65 of the post 18. The stabilizing post
also includes an opposite anterior end 63 that contacts the closed
end 51 of the channel 47. The stabilizing post can thus move along
the length of the channel from an anterior position 18' to a
posterior position 18", as depicted in FIG. 5.
[0035] The spine 57 of the stabilizing post 18 includes an anterior
face 59 and an opposite posterior face 61. Each face exhibits a
pre-defined curvature for cammed movement of the stabilizing post
during articulation of the femoral component 12 on the intermediate
component 16. In order to achieve this cammed movement, the femoral
component, and more particularly the intercondylar recess 32,
defines a posterior-facing cam surface 77 at one end of the recess
and an anterior-facing cam surface 79 at the opposite end of the
recess, as shown best in FIG. 6. In essence, the two cam surfaces
77, 79 extend from the posterior and anterior ends of the slot 33
(FIG. 1). These cam surfaces bear against a corresponding face 59,
61 of the spine 57 to urge the stabilizing post 18 along the
channel in the AP direction. This feature allows the femoral
component 12 to both roll and slide relative to the tibial
component without exposing the articulating components and surfaces
to the soft tissue surrounding the joint.
[0036] This rolling and sliding movement can be appreciated from a
comparison of FIGS. 7 and 8. In FIG. 7, the stabilizing post 18 is
in its anterior position 18' and the femur and femoral component 12
is essential at its zero degree angle relative to the tibia and
tibial component 14. The posterior-facing cam surface 77 bears
against the anterior face 59 of the spine 57. As the femoral
component 12 begins to roll in the direction of the arrow R (FIG.
7), the cam surface 77 bears against the anterior face 59 of the
spine 57 to push the stabilizing post 18 posteriorly. Eventually,
the post is pushed to its posterior position 18", as shown in FIG.
8. The slope and curvature of the anterior face 59 dictates the
degree and speed of travel of the post along the channel 47.
[0037] Once the stabilizing post is in its posterior position 18",
the camming surface 77 no longer contacts the spine 57 as the
femoral component continues to roll and translation anteriorly
relative to the tibial component. Eventually, the femoral component
is in the relative position shown in FIG. 8 in which the femur is
at an angle of about 120.degree. relative to the tibia. The tab 34
engages the posterior indentation 73 in the locking member 20 to
prevent further relative rolling and translation (in conjunction
with tension in the collateral ligaments). In this position, the
anterior-facing cam surface 79 contacts the posterior face 61 of
the spine 57.
[0038] As the femoral component undergoes relative rolling in the
opposite direction, as designated by the arrow R' in FIG. 8, the
cam surface 79 bears against the posterior face 61 to push the
spine 57 anteriorly along the channel. When the cam surface 79
breaks contact with the spine, the stabilizing post is in its
relative anterior position 18' (FIG. 7). The spine thus prevents
further anterior relative translation of the femoral component 12.
Again, it can be seen that none of the articulating surfaces or
components impinge or are exposed to the surround soft tissue, even
where the femoral component moves between the extreme relative
positions shown in FIGS. 7 and 8.
[0039] The sliding stabilizing post 18 of the present invention
provides a significant advantage during the total knee replacement
procedure. In specifically, the specific post can be selected
during the procedure and tested to verify optimum knee movement for
the particular patient. In other words, while the post 18 shown in
the present figures exhibits a certain configuration, an array of
posts can be available, all with different profiles. For instance,
the posts can be configured to permit greater or lesser movement
within the channel 47. In addition, one or both of the faces 59, 61
can be modified to achieve a specific camming action when contacted
by the femoral component cam surfaces 77, 79.
[0040] Thus, in accordance with one feature of the present
invention, the femoral and tibial components 12, 14 can be prepared
bone surfaces. The intermediate or meniscal component 16 can be
mounted to the tibial component 14 with the knee in flexion. A
pre-selected stabilizing post 18 can be slid into the channel 47
and a temporary locking member can close the post within the
channel. The knee can then be moved with the prosthesis in situ
through certain degrees of motion to determine whether the selected
post is optimum for the particular patient's anatomy. If not, the
post can be removed and replaced with a different post having a
different profile. Once an optimum stabilizing post has been found,
the locking member 20 can be connected to the intermediate
component 16 to lock the finally selected post 18 within the
channel 47.
[0041] The same process can be followed with respect to the locking
member 20. Locking members having different lengths along the
channel can be provided to allow more or less sliding movement of
the stabilizing post 18 within the channel 47. In some cases, a
locking member can be selected that does not permit any sliding of
the post 18.
[0042] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same should
be considered as illustrative and not restrictive in character. It
is understood that only the preferred embodiments have been
presented and that all changes, modifications and further
applications that come within the spirit of the invention are
desired to be protected. For instance, the intermediate component
16 may be made integral with the tibial component 14. In this case,
the rotational degree of freedom would be eliminated.
[0043] In addition, the engagement of the stabilizing post 18 to
the channel 47 can be modified so that the both ends of the channel
are closed. For example, the channel can be provided with an
enlarged top opening and the base 55 of the post 18 can be
configured to fit through the enlarged opening and then pivot to
engage the grooves 53 at the base of the channel. Engagement of the
spine 57 within the intercondylar recess 32 will prevent pivoting
of the post once it is disposed within the channel.
[0044] In the illustrated embodiment, the channel 47 is described
as including one closed end 51 and an opposite open end 49.
Alternatively, both ends of the channel can be open with a
corresponding locking member, such as the locking member 20,
closing each end to trap the stabilizing post 18 within the.
channel. The two locking members can be selected intra-operatively
to optimize and orient the translation of the stabilizing post
within the channel.
* * * * *