U.S. patent application number 10/302066 was filed with the patent office on 2004-05-27 for modular knee prosthesis.
Invention is credited to Saladino, Joseph.
Application Number | 20040102851 10/302066 |
Document ID | / |
Family ID | 32324667 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040102851 |
Kind Code |
A1 |
Saladino, Joseph |
May 27, 2004 |
MODULAR KNEE PROSTHESIS
Abstract
A modular knee prosthetic system used to replace the natural
knee and including two distal posterior femoral components and one
patellar-femoral joint component. The components have a smooth
outer condylar surface and an inner bone-engaging surface and are
connectable to form either an unicompartmental or bicompartmental
femoral knee prosthesis.
Inventors: |
Saladino, Joseph;
(Pflugerville, TX) |
Correspondence
Address: |
ZIMMER TECHNOLOGY, INC.
150 N. WACKER DRIVE
SUITE 1200
CHICAGO
IL
60606
US
|
Family ID: |
32324667 |
Appl. No.: |
10/302066 |
Filed: |
November 22, 2002 |
Current U.S.
Class: |
623/20.15 ;
623/20.35 |
Current CPC
Class: |
A61F 2002/30331
20130101; A61F 2002/30892 20130101; A61F 2002/3895 20130101; A61F
2002/30616 20130101; A61F 2220/0033 20130101; A61F 2/3859 20130101;
A61F 2002/30332 20130101; A61F 2002/30975 20130101; A61F 2230/0034
20130101; A61F 2002/30878 20130101; A61F 2/389 20130101; A61F
2002/30604 20130101; A61F 2002/30187 20130101 |
Class at
Publication: |
623/020.15 ;
623/020.35 |
International
Class: |
A61F 002/38 |
Claims
What is claimed is:
1. A tricompartmental femoral knee prosthesis, comprising: a medial
distal posterior femoral component having a smooth articulating
medial surface and a bone engaging medial surface oppositely
disposed from the articulating medial surface; a lateral distal
posterior femoral component having a smooth articulating lateral
surface and a bone engaging lateral surface oppositely disposed
from the articulating lateral surface; and a patellar-femoral
component having a smooth articulating patellar-femoral surface and
being connected to the medial distal posterior femoral component
and the lateral distal posterior femoral component, wherein the
patellar-femoral component, the medial distal posterior femoral
component, and the lateral distal posterior femoral component are
three separate components that connect together to form the
tricompartmental femoral knee prosthesis.
2. The tricompartmental femoral knee prosthesis of claim 1 in which
the patellar-femoral component is removeably connectable to both
the medial distal posterior femoral component and the lateral
distal posterior femoral component.
3. The tricompartmental femoral knee prosthesis of claim 2 in which
the articulating patellar-femoral surface and the articulating
lateral and medial surfaces meet and form a continuous and seamless
articulating surface.
4. The tricompartmental femoral knee prosthesis of claim 3 in which
the patellar-femoral component includes a connection mechanism
adapted to engage and connect to both the medial and lateral distal
posterior femoral components.
5. The tricompartmental femoral knee prosthesis of claim 4 in which
the medial distal posterior femoral component includes a medial
connector adapted to receive the connection mechanism; and the
lateral distal posterior femoral component includes a lateral
connector adapted to receive the connection mechanism.
6. The tricompartmental femoral knee prosthesis of claim 5 in which
the medial and lateral connectors are configured as recesses; and
the connection mechanism is configured as two spaced-apart
projections, wherein each projection is adapted to fit into one
recess.
7. The tricompartmental femoral knee prosthesis of claim 5 in which
the medial and lateral connectors are configured as projections;
and the connection mechanism is configured as two spaced-apart
recesses, wherein each projection is adapted to fit into one
recess.
8. A unicompartmental modular knee prosthesis, comprising: a
femoral component having a smooth articulating surface on one side,
a bone engaging surface on another side, and a stem projecting
outwardly from the bone engaging surface; and a patellar-femoral
component having a smooth articulating patellar-femoral surface and
being connected to the femoral component, wherein the
patellar-femoral component and the femoral component are two
separate components, and the articulating patellar-femoral surface
and the articulating surface of the femoral component connecting to
form a continuous surface adapted to articulate with a tibial
insert.
9. The unicompartmental modular knee prosthesis of claim 8 in which
a junction between the articulating patellar-femoral surface and
the articulating surface of the femoral component is seamless.
10. The unicompartmental modular knee prosthesis of claim 9 in
which the patellar-femoral component includes a connection
mechanism that engages and connects to the femoral component.
11. The unicompartmental modular knee prosthesis of claim 10 in
which the femoral component includes a connector adapted to engage
and connect to the connection mechanism.
12. The unicompartmental modular knee prosthesis of claim 11 in
which the connection mechanism and the connector are one of a
recess or projection.
13. The unicompartmental modular knee prosthesis of claim 11 in
which the connection mechanism and connector press-fit
together.
14. The unicompartmental modular knee prosthesis of claim 11 in
which the connection mechanism and connector are removeably
connected together.
15. The unicompartmental modular knee prosthesis of claim 11 in
which the connection mechanism and connector are permanently
connected together using a Morse taper connection.
16. A femoral knee implant, comprising: at least three separate
components that include two medial distal posterior components and
one patellar-femoral component, all three components having a
smooth outer condylar surface adapted to articulate with a tibial
insert and an inner bone-engaging surface adapted to engage bone;
each medial distal posterior component includes a connector; and
the patellar-femoral component includes a connection mechanism
adapted to engage and connect to each connector.
17. The femoral knee implant of claim 16 in which the connection
mechanism and the connectors slideably engage.
18. The femoral knee implant of claim 17 in which the connection
mechanism and the connectors press-fit to lock together.
19. The femoral knee implant of claim 16 in which each medial
distal posterior component is formed of two separate components
that are connectable.
20. The femoral knee implant of claim 19 in which the medial distal
posterior component are formed from a top half and a bottom half,
wherein the top half and bottom half are removeably connectable
together.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a modular knee prosthetic
system used to replace the natural knee and, more particularly, to
a unicompartmental and bicompartmental modular knee system having
various distal posterior femoral components that are
interchangeable with each other and with various patellar-femoral
joint components.
BACKGROUND OF THE INVENTION
[0002] In knee arthroplasty, portions of the natural knee joint are
replaced with prosthetic knee components. Typically, these
components include a tibial component, a femoral component, and a
patellar component. The femoral component generally includes a pair
of spaced condyles that articulate with the tibial component. The
components are made of materials that exhibit a low coefficient of
friction when they articulate against one another.
[0003] When the articulating ends of both the femur and tibia are
replaced, the procedure is referred to as total knee replacement or
TKR. Much effort has been devoted to performing a TKR that restores
normal, pain-free, functions of the knee in a short period of
postoperative time.
[0004] Several factors lead to long-term success of TKR. One
important factor is soft-tissue balancing. The normal, non-diseased
knee is considered properly balanced when the deflection between
the medial and lateral condyles and the tibial plateau is equal
throughout the entire range of motion. If this balance is not
achieved, abnormal knee kinematics occurs, and the TKR components
and surrounding soft tissue can experience excessive forces even
during normal range of motion. These excessive forces can further
cause an abnormal gait, pain, and early failure of total knee
replacements.
[0005] Soft-tissue balancing can be achieved in TKR if the
components are correctly sized and properly placed. In order to
achieve proper placement during a TKR surgery, equal tibial-femoral
flexion gaps and extension gaps must be achieved. The flexion gap
is defined as the space between the posterior coronal cut on the
distal femur and transverse cut on the proximal tibia, while the
knee is in 90.degree. of flexion. The extension gap is defined as
the space between the transverse cut on distal femur and the
transverse proximal tibial cut while the knee is in complete
extension. Soft tissue balance occurs when stability is achieved in
both flexion and extension.
[0006] During a TKR surgery, a series of surgical compromises is
often used to achieve a balance of flexion and extension gaps.
Elevation of the joint line is one such compromise. An elevation of
the joint line occurs when there is a change in distance from the
original articular surface to the newly reconstructed surface. This
change in distance is typically measured as a vertical distance
from a fixed point on the tibia.
[0007] For several reasons, the joint line can become elevated.
Excessive medial or lateral releases and insertion of thicker
plastic inserts can cause the line to elevate. Further, the joint
line can become elevated when the femoral component is undersized.
Such an undersize can create a larger flexion gap than extension
gap. To balance these gaps, more bone may need to be removed from
the distal femur; and this additional bone loss raises the joint
line.
[0008] Unfortunately, a change in the joint line can negatively
affect a wide array of components and operations of the knee, such
as the functions of the PCL, collateral ligaments, and
patello-femoral joint mechanics. These problems can be avoided or
minimized if elevation of the joint line is reduced or, better yet,
eliminated.
[0009] Another surgical compromise often occurs when soft tissue
gaps are balance when implanting a distal femoral knee prosthesis.
A healthy balance of these gaps maintains the natural kinematics of
the patient. The compromise occurs when the operating surgeon must
choose one of six or seven differently sized distal femur
prostheses; and the size of these prostheses may not exactly match
the size of an ideal prosthesis for the patient. For example,
current anterior referencing methodology to achieve balanced
flexion and extension gaps in most patients requires the surgeon to
slightly alter the joint line. If an anterior referencing sizing
guide falls between two sizes, the surgeon could be forced to
choose a smaller size prosthesis so the flexion gap is not
overstuffed. A smaller prosthesis, in such an instance however, can
consequently enlarge the flexion gap as much as 3.5 mm to 4 mm.
[0010] Another important factor that contributes to the long-term
success of total knee replacements is loading and kinematics of the
patellar-femoral joint. Complications associated with patella
failures account for up to 50% of TKR revision procedures. Many of
these complications occur because of improper or unnatural loading
or kinematics of the patellar-femoral joint. For example,
overstuffing the patellar-femoral joint is one major cause of
improper soft tissue loading and kinematics. In this regard, many
surgeons use posterior referencing instrumentation when sizing and
preparing the femur for implant resurfacing. On the one hand,
posterior referencing allows the surgeon to balance the
tibial-femoral flexion and extension gaps without necessarily
changing the joint line. On the other hand though, the use of
posterior referencing increases the risk of notching the anterior
cortex and overstuffing the patellar-femoral joint.
[0011] In short, current knee systems often require an unwanted
surgical compromise. Such compromises can alter the natural joint
line of the patient or overstuff the patellar-femoral joint.
Unfortunately, these compromises also negatively affect the natural
kinematics of the patient and can, for example, increase strain on
the PCL and other tendons and ligaments, increase implant wear, and
decrease implant function. Patients may be more likely to
experience pain, reduced function, and more frequent revision
surgeries.
[0012] Current knee systems have other disadvantages as well.
Distal femoral prostheses are simply too large to fit through small
incisions that are used during a minimally invasive surgery or MIS.
MIS has many advantages over traditional surgical techniques since
it provides shorter incisions, faster recovery times, and generally
less pain for the patient. The surgical technique, though, has
limitations. As noted, current tricompartmental distal femoral
prostheses cannot fit through the small incision, usually three
inches in length. To date, MIS has been generally limited to
unicondylar or unicompartmental knee replacement prostheses that
are much smaller in size and able to fit through the incision.
[0013] It would be advantageous to have a modular knee prosthetic
system that has advantages over prior knee prosthetic systems and
techniques. Such a system would have greater modular versatility to
accommodate different patient anatomies and joint conditions while
maintaining a relatively low component count.
SUMMARY OF THE INVENTION
[0014] The present invention is directed toward a modular knee
system having various distal posterior femoral components that are
interchangeable with each other and with various patellar-femoral
joint components. Preferably, the modular knee system has a variety
of components that are interchangeable and connectable to resurface
the distal femur using either a unicompartmental femoral knee
prosthesis or a bicompartmental femoral knee prosthesis. These
components include a medial distal posterior femoral component, a
lateral distal posterior femoral component, a patellar-femoral
joint component, and an interconnection mechanism to modularly
connect the components together.
[0015] The knee system of the present invention allows for
modularity between the distal posterior femoral components and the
patellar-femoral joint components. The interchangeability of these
components enables mixing and matching of multiple sizes and
thicknesses of all components. This interchangeability allows the
surgeon to resurface the distal femur without overstuffing the
patellar compartment or changing the natural tibial-femoral joint
line.
[0016] One advantage of the present invention is that the
modularity of components gives the surgeon more diversification
when choosing sizes for the medial and lateral condyles. The
deflection between these condyles and the tibial plateau, thus, can
be more easily equalized throughout the range of motion. As such,
the soft-tissue can be more easily balanced.
[0017] Another important advantage of the present invention is that
the various knee components are interchangeable and can be more
correctly sized for an accurate fit. As such, more equal
tibial-femoral flexion gaps and extension gaps can be achieved. In
particular, excessive medial or lateral releases and insertion of
thicker plastic inserts can be more easily avoided. Elevation of
the joint line in these situations can be minimized or, better yet,
avoided.
[0018] Further, modularity of the knee components enables a more
natural balance between soft tissue gaps when implanting a distal
femoral knee prosthesis. If, for example, different sizing occurs
between the medial and lateral sides of the distal posterior
components, differently sized distal posterior femoral components
can be connected together to accommodate this variance of sizing.
Thus, differently sized condyles may be implanted on the medial and
lateral sides to more closely replicate the natural anatomy of the
patient. Further, additional bone may be saved and not
unnecessarily removed from the distal femur or from the tibia.
[0019] Since the present invention can more readily accommodate
various sizes during knee replacement surgery, the natural location
of the joint line can be maintained. Certain problems associated
with altering the joint line can be avoided or minimized.
[0020] The present modular knee system can also help achieve
natural loading and kinematics of the patellar-femoral joint. For
example, the various sizes and interchangeability of knee
components can enable more correctly sized patellar-femoral joints.
In some situations, overstuffing can be avoided.
[0021] As another important advantage, all of the individual
components of the modular knee system of the present invention is
small enough to be used during minimally invasive surgery or MIS.
Each modular component can fit through a three inch incision. Even
more importantly, the modular components can be assembled after
being inserted through the incision. Thus, the modular knee system
can be used with either unicompartmental, bicompartmental, or
tricompartmental procedures (i.e., either unicondylar, bicondylar,
or tricompartmental knee replacements).
[0022] As yet even another advantage, the modularity of the present
knee system reduces the overall number of individual components
required in a knee product line. This reduction has significant
cost savings.
[0023] Accordingly, the present invention comprises a combination
of features and advantages that overcome various problems,
deficiencies, or shortcomings associated with prior devices. The
various features and advantages of the invention will be readily
apparent to those skilled in the art upon referring to the
accompanying drawings and reading the following detailed
description of the preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] For a more detailed description of preferred embodiments of
the present invention, reference will now be made to the
accompanying drawings, wherein:
[0025] FIG. 1 illustrates a perspective view of two medial distal
posterior femoral components of the present invention.
[0026] FIG. 2 illustrates a side view of the femoral components of
FIG. 1.
[0027] FIG. 3 illustrates a perspective view a patellar-femoral
joint component of the present invention.
[0028] FIG. 4 illustrates the condylar surface of the
patellar-femoral joint component of FIG. 3.
[0029] FIG. 5 illustrates an exploded view of the two medial distal
posterior femoral components of FIG. 1 connecting to the
patellar-femoral joint component of FIG. 3.
[0030] FIG. 6 illustrates a perspective view of a bicompartmental
femoral knee with the two medial distal posterior femoral
components of FIG. 1 connected to the patellar-femoral joint
component of FIG. 3.
[0031] FIG. 7 illustrates a single medial distal posterior femoral
component.
[0032] FIG. 8 illustrates an exploded view of a unicompartmental
femoral knee with the single medial distal posterior femoral
component of FIG. 7 and a single patellar-femoral joint
component.
[0033] FIG. 9 illustrates a unicompartmental femoral knee with the
medial distal posterior femoral component and the patellar-femoral
joint component of FIG. 8 connected together.
[0034] FIG. 10 illustrates an exploded view of a first modular
connection of a single medial distal posterior femoral component
connecting to a patellar-femoral component with dual condylar
surfaces.
[0035] FIG. 11 illustrates a perspective view of the components of
FIG. 10 connected together.
[0036] FIG. 12 illustrates an exploded view of a second modular
connection of a single medial distal posterior femoral component
connecting to a patellar-femoral component with dual condylar
surfaces.
[0037] FIG. 13 illustrates a perspective view of the components of
FIG. 11 connected together.
[0038] FIG. 14 illustrates a perspective view of a unicompartmental
femoral knee with the medial distal posterior femoral component and
the patellar-femoral joint component connected to a tibial insert
and tibial baseplate.
[0039] FIG. 15 illustrates a first exploded view of a five-piece
femoral knee.
[0040] FIG. 16 illustrates a second exploded view of the five-piece
femoral knee of FIG. 15.
[0041] FIG. 17 illustrates a perspective view of the five-piece
femoral knee of FIG. 15 wherein the five components are connected
together to form a biocompartmental femoral knee.
DETAILED DESCRIPTION
[0042] FIGS. 1 and 2 illustrate two separate distal posterior
femoral components generally at 10. One component is a medial
distal posterior femoral component (DPFC) 12, and a second
component is a lateral DPFC 14. Both femoral components 12 and 14
have a smooth outer condylar surface 16 adapted to articulate with
a tibial insert. Surface 16 is shaped as a partial femoral condyle
that extends from a proximal portion 18 to a distal portion 20. A
bone engaging surface 22 is oppositely disposed from the condylar
surface 16. This surface 22 includes several flat, planar sections
24 that extend from the proximal portion 18 to the distal portion
20. A stem 26 projects upwardly from the bone engaging surface 22.
This stem 26 has a tapering cylindrical shape and is adapted to be
inserted in the intramedullary canal of a femur.
[0043] The medial and lateral DPFC also includes a connector 28
located on an end surface 30 of the proximal portion 18. The
connectors 28 are shaped as cylindrical, tapering recesses. These
recesses extend into the body of the femoral components.
[0044] FIGS. 3 and 4 illustrate a patellar-femoral joint component
(PFJC) 40. The PFJC 40 has a smooth outer condylar surface 42
adapted to articulate with a tibial insert. Surface 42 is shaped as
a partial femoral condyle that extends from a proximal portion 44
to a distal portion 46. A bone engaging surface 48 is oppositely
disposed from the condylar surface 42. This surface 48 includes
several flat, planar sections 50 that extend from the proximal
portion 44 to the distal portion 46.
[0045] The PFJC 40 also includes a connection mechanism 54 located
on an end surface 56 of the proximal portion 44. The connection
mechanism 54 is shaped as two separate, spaced projections having a
cylindrical, tapering body. The projection extends outwardly from
the body of the PFJC.
[0046] Turning also to FIGS. 5 and 6, connection mechanism 54 of
the PFJC 40 is adapted to engage and connect with the connectors 28
on both the medial DPFC 12 and lateral DPFC 14. Specifically, the
projections of the connection mechanism 54 slideably press-fit to
lock into the recesses of the connectors 28. This connection may
utilize a Morse taper fit.
[0047] One skilled in the art will appreciate that many different
means exist for connecting the distal posterior femoral components
10 to the PFJC 40. In this regard, the connectors 28 could be
configured as tapering male projections while the connection
mechanism is configured as a tapering recess adapted to receive the
projections. Other connections exist as well. For example, the
connection mechanism could be configured to snapingly engage the
connectors or configured as a bayonet type connection. Further, the
connection between the connection mechanism 54 and the connectors
28 could be permanent or removeably connected.
[0048] It is important to note that when the medial DPFC 12 and the
lateral DPFC 14 connect to the PFJC 40, these components form a
complete, full femoral knee prosthesis 60 (see FIG. 6). This
prosthesis 60 functions as a traditional one-piece bicompartmental
femoral prosthesis. As such, the prosthesis 60 may be used as a
bicompartmental femoral prosthesis for total knee replacements. The
important advantage of the present invention, though, is that the
prosthesis 60 is composed of several modular pieces. Specifically,
the prosthesis is composed of three separate, interconnectable
pieces, namely a medial DPFC 12, a lateral DPFC 14, and a PFJC
40.
[0049] As noted, the distal posterior femoral components have a
partial condylar surface 16, and the PFJC 40 has a partial condylar
surface 42. When these components are connected together to form
the femoral knee prosthesis 60, then the surfaces 16 and 42 join
and form a full condylar surface 62. This surface 62 extends from
the distal portion 20 of the distal posterior femoral components to
the distal portion 46 of the PFJC. Preferably, this surface 62 is
continuous and seamless at the junction or union 66 from surface 16
to surface 42. No bumps, ridges, seams, indentations, channels, or
the like should exist at the junction 66 where the surfaces
meet.
[0050] FIGS. 7-9 illustrate one of the modular properties of the
present invention. FIG. 7 shows a single distal posterior femoral
component 80. DPFC 80 is similarly configured to the distal
posterior femoral components shown in FIGS. 1 and 2. This component
80 may be shaped for use as a medial DPFC, lateral DPFC, or generic
and useable for both medial and lateral indications.
[0051] FIG. 8 shows a patellar-femoral joint component 90 that is
similarly configured to the PFJC 40 shown in FIGS. 3 and 4. One
important exception is the PFJC 90 is not shaped for
bicompartmental use but for unicompartmental use. More
specifically, the PFJC 90 has a single smooth outer condylar
surface 92 adapted to articulate with a tibial insert. Surface 92
is shaped as a partial single femoral condyle that extends from a
proximal portion 94 to a distal portion 96. A bone engaging surface
98 is oppositely disposed from the condylar surface 92. This
surface 98 includes several flat, planar sections 100 that extend
from the proximal portion 94 to the distal portion 96. The PFJC 90
also includes a connection mechanism 102 located on an end surface
104 of the proximal portion 94. The connection mechanism 102 is
shaped as a single projection having a cylindrical, tapering body.
This projection extends outwardly from the body of the PFJC and is
adapted to fit into a connector 106 shaped as a recess on the DPFC
80. The connection between the DPFC 80 and PFJC 90 are similar to
the connections discussed in connection with FIGS. 1-6; one
difference is the connection in FIGS. 7-9 uses a single connection
mechanism or projection and a single connector or recess.
[0052] As shown in FIGS. 7-9 then, one advantage of the present
invention that the DPFC 80 and the PFJC 90 connect together to form
a complete femoral knee prosthesis 110 (see FIG. 9). This
prosthesis 110 functions as a traditional one-piece
unicompartmental femoral prosthesis. One important advantage of the
present invention is that the unicompartmental prosthesis 110 is
composed of several modular pieces. Specifically, the prosthesis is
composed of two separate, interconnectable pieces, namely a DPFC 80
and a PFJC 90.
[0053] FIGS. 10-13 show more examples of the diversification of
modularity of the present invention. These figures show a DPFC 120
that is connectable to a PFJC 122. The DPFC 120 is similar to the
distal posterior femoral components shown in FIGS. 1 and 2, and
PFJC 122 is similar to the patellar-femoral joint component shown
in FIGS. 3 and 4. In FIGS. 10 and 11 though, the PFJC 122 connects
to a single DPFC 120 on the medial side. By contrast, in FIGS. 12
and 13, the PFJC 122 connects to a single DPFC 120 on the lateral
side.
[0054] FIG. 14 shows one example how the modular components of the
present invention can be utilized. Here, a DPFC 130 and a PFJC 132
are connected together to form a unicompartmental femoral
prosthesis 134. This prosthesis 134 has an extended or enlarged
stem 136, but otherwise is generally similar to the
unicompartmental prosthesis 110 shown in FIG. 9.
[0055] As shown in FIG. 14, the unicompartmental femoral prosthesis
134 has a bone engaging surface 140 with a porous or
Cancellous-Structured Titanium (CSTi) coating to enhance bone
engagement. An outer articulating condylar surface 142 abuts
against a tibial insert 144. This insert 144 is connected to a
tibial baseplate 146 having a base portion 148 and threaded screw
or stem 150 extending downwardly from the base portion. The tibial
insert 144 and baseplate 146 are known to those skilled in the art
and may be similar, for example, to those sold by Centerpulse
Orthopedics Inc. of Austin, Tex.
[0056] FIGS. 15-17 show yet more examples of the diversification of
modularity of the present invention. Here, a complete femoral knee
prosthesis 160 is shown. This prosthesis 160 includes a single PFJC
162 and two DPFC 164 and functions as a traditional bicompartmental
prosthesis as shown and described in FIG. 6. As one important
difference, each DPFC 164 is formed from two separate components,
namely a top half 166 and a bottom half 168. When the top half 166
and bottom half 168 are connected, they function as the DPFC
described in FIGS. 1 and 2. Here though, each top half 166 includes
a connector 170; and each bottom half includes a connector 172. The
connectors 170 and 172 are shown as recesses and projections,
respectively, and slideably press-fit together to form single
distal posterior femoral components.
[0057] As discussed in connection with connection mechanism 54 of
PFJC 40 and connectors 28 of DPFC 12 and 14 in FIGS. 5 and 6, the
connectors 170 and 172 may have various configurations known to
those skilled in the art to achieve a permanent or removable
connection between the top half 166 and bottom half 168.
[0058] One important advantage of the present invention is that all
of the individual, separate distal posterior femoral components and
the patellar-femoral joint components are adapted to be used in
minimally invasive surgery (MIS) techniques. MIS is intended to
allow for the maximum preservation of bone stock, restoration of
kinematics, minimal disturbance of the patellar tendon, and rapid
rehabilitation postoperatively. During an MIS knee surgery, a three
inch incision is made. The DPFC and PFJC are small enough to fit
through this incision. Thus, these components can be fit through
the incision and then assembled to form a unicompartmental femoral
knee, bicompartmental femoral knee, or hybrid of these two (the
various embodiments being shown in FIGS. 1-17).
[0059] Another advantage of the present invention is the distal
posterior femoral components can be made to be completely
interchangeable. Thus, no need exists for separate medial/lateral
or left/right components. Further the DPFC and PFJC can be made to
have various sizes and thicknesses to accommodate various patient
needs. The components can even be coated with CSTi or other
coatings known to those skilled in the art to enhance bone growth
or cement retention.
[0060] As another advantage, the total modular design of the
present invention, in addition to being compatible with MIS, allows
the surgeon to resurface only the anatomy that requires
resurfacing. Thus, the surgeon can assemble a femoral knee
prosthesis to better fit the needs of the individual patient and
minimize or eliminate unnecessary bone cuts.
[0061] Further yet, modularity of the present invention can also
save the manufacturer tremendous inventory costs, especially if
existing instrumentation can be used. The charts below summarize
one potential manufacturing cost savings. The chart on the left
shows a typical number of components for a non-modular femoral knee
system. The chart on the right shows a typical number of components
utilizing the modular components of the present invention. As
shown, an inventory can be reduced by approximately 41
components.
1 1
[0062] More advantages of the present invention are listed below
and are explained in the Summary section:
[0063] Full modularity between anterior and distal and posterior
femoral components eliminates the need for the surgeon to
compromise the patient's natural gait. The system provides the
surgeon with flexibility and control in implant sizing.
[0064] Multiple distal and posterior components allow multiple
ethnic anatomies to be replicated with one knee system. For
instance, Asian patients may require longer posterior condyles to
replicate their natural anatomy. The option of attaching an Asian
unicondylar component to a PFJC will allow the surgeon to convert
the prosthesis to allow for high flexion.
[0065] A stand-alone patella-femoral component would allow the PFJC
to be included in the same system as the primary knee.
[0066] A stand-alone distal/posterior component can be used as an
MIS unicompartmental prosthesis. Thus the surgeon can make the
intraoperative choice of unicompartmental or bicompartmental
procedure.
[0067] A stand-alone Asian distal/posterior component would allow a
unicompartmental or bicompartmental procedure that would closely
replicate the Asian anatomy.
[0068] Posterior femoral components of two different thickness
options may be implanted on the medial and lateral condyles. This
option will allow the surgeon to correctly replicate the natural
patient anatomy.
[0069] An attachment or connection feature and mechanism between
the anterior PFJC and the distal components. The attachment allows
a surgeon to convert a unicompartmental knee to a primary knee by
simply attaching the anterior component to the existing
distal/posterior component(s). The attachment features would also
allow the surgeon to convert a PFJC to a total knee replacement
without revising the PFJC.
[0070] While preferred embodiments of this invention have been
shown and described, modifications thereof can be made by one
skilled in the art without departing from the spirit or teaching of
this invention. The embodiments described herein are exemplary only
and are not limiting. Many variations and modifications of the
system, apparatus, and methods are possible and are within the
scope of the inventions claimed below. Accordingly, the scope of
protection is not limited to the embodiments described herein, but
is only limited by the claims that follow, the scope of which shall
include all equivalents of the subject matter of the claims.
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