U.S. patent application number 10/370154 was filed with the patent office on 2003-08-21 for knee arthroplasty prosthesis and method.
Invention is credited to Coon, Thomas M., Smucker, Donald M., Tria, Alfred J. JR., Van Zile, Richard R..
Application Number | 20030158606 10/370154 |
Document ID | / |
Family ID | 27757712 |
Filed Date | 2003-08-21 |
United States Patent
Application |
20030158606 |
Kind Code |
A1 |
Coon, Thomas M. ; et
al. |
August 21, 2003 |
Knee arthroplasty prosthesis and method
Abstract
A knee arthroplasty prosthesis includes a femoral component
having multiple pieces with engagement means provided for engaging
various pieces of the femoral component to one another following
their insertion in the incised area of the femur. A tibial
component includes multiple pieces designed for assembly following
positioning in the incision. The tibial component includes a Morse
taper cavity on one piece of the tibial component and a Morse taper
extension on another member of the component for receipt
therein.
Inventors: |
Coon, Thomas M.; (Redding,
CA) ; Tria, Alfred J. JR.; (Princeton, NJ) ;
Smucker, Donald M.; (Perrysburg, OH) ; Van Zile,
Richard R.; (Bryan, OH) |
Correspondence
Address: |
EMCH, SCHAFFER, SCHAUB & PORCELLO CO
P O BOX 916
ONE SEAGATE SUITE 1980
TOLEDO
OH
43697
|
Family ID: |
27757712 |
Appl. No.: |
10/370154 |
Filed: |
February 19, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60358174 |
Feb 20, 2002 |
|
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|
Current U.S.
Class: |
623/20.15 ;
623/20.34; 623/20.35 |
Current CPC
Class: |
A61F 2002/30604
20130101; A61F 2220/0025 20130101; A61F 2002/30515 20130101; A61F
2002/30433 20130101; A61F 2002/30616 20130101; A61F 2250/0084
20130101; A61F 2002/30878 20130101; A61F 2002/30708 20130101; A61F
2/30744 20130101; A61F 2002/30405 20130101; A61F 2002/30332
20130101; A61F 2002/3079 20130101; A61F 2220/0033 20130101; A61F
2002/30339 20130101; A61F 2002/4638 20130101; A61F 2002/30492
20130101; A61F 2002/30387 20130101; A61F 2002/30975 20130101; A61F
2002/30331 20130101; A61F 2002/30884 20130101; A61F 2/4637
20130101; A61F 2/38 20130101; A61F 2002/4631 20130101; A61F
2002/30797 20130101; A61F 2002/30892 20130101; A61F 2220/0041
20130101; A61F 2/3859 20130101; A61F 2/389 20130101; A61F
2002/30822 20130101 |
Class at
Publication: |
623/20.15 ;
623/20.34; 623/20.35 |
International
Class: |
A61F 002/38 |
Claims
We claim:
1. A femoral component for knee arthroplasty in a knee having a
natural patella or a prosthetic patella comprising (a) a first
piece having a patellar femoral flange portion including an
articulating surface for engagement by said patella, said first
piece extending from an anterior end toward a posterior end and
having one or more engagement surfaces defining one side of a
joint; (b) a second piece defining at least one condylar portion
and having an articulating surface, said second piece extending
from said posterior end toward said anterior end and having one or
more abutment surfaces cooperating with said engagement surfaces to
define said joint; and (c) a fastener for securing said first piece
and said second piece together.
2. The femoral component of claim 1 further including a third piece
defining a second condylar portion extending from said posterior
end toward said anterior end and having at least one abutment
surface cooperating with said engagement surface to define a second
joint and further including a second fastener for securing said
third piece to said first piece.
3. The femoral component of claim 1 wherein said second piece
includes first and second condylar portions and at least one
laterally extending cross member supporting said first condylar
portion to said second condylar portion.
4. The femoral component of claim 3 wherein said cross member is
located adjacent said posterior end.
5. The femoral component of claim 3 wherein there is provided a
first cross member located adjacent said posterior end and a second
cross member located adjacent said abutment surfaces.
6. The femoral component of claim 3 wherein said at least one
laterally extending cross member is located adjacent said abutment
surfaces.
7. The femoral component of claim 6 wherein said first piece
includes a central surface extending laterally and first and second
side engagement surfaces extending from said central surface
angularly away from each other in a direction toward said anterior
end, and wherein said second piece cross member has (i) a medial
surface spaced from said condylar portion articulating surface,
(ii) an opposed bone engaging surface, and (iii) a leading surface
facing said first piece and extending between said medial surface
and said bone engaging surface and wherein said first piece
includes a ledge extending anteriorly from said central surface,
said ledge engaged to said cross member medial surface.
8. The femoral component of claim 7 further including a first piece
extension extending superiorly from said ledge and a second piece
extension extending superiorly from said cross member, said first
piece extension and said second piece extension having a mating
tongue and groove configuration for joining together.
9. The femoral component of claim 3 wherein said first piece
includes a central surface extending laterally and first and second
side engagement surfaces extending from said central surface
angularly away from each other in a direction toward said anterior
end.
10. The femoral component of claim 1 wherein the articulating
surface of said first piece in the area of said joint and the
articulating surface of said second piece in the area of said joint
cooperate to form a recess.
11. The femoral component of claim 1 wherein said joint is in an
area of low stress from sliding engagement by the patella.
12. The femoral component of claim 1 wherein said second piece has
(i) two condylar portions, each having an articulating surface, and
(ii) a connecting section having an articulating surface extending
smoothly from both of said condylar portions articulating surfaces
to said one or more abutment surfaces.
13. The femoral component of claim 12 wherein said one or more
engagement surfaces and said one or more abutment surfaces each
define a series of intermeshing valleys and projections with
apertures extending through or into projections of each of said
first piece and said second piece and an engagement pin or screw
extending into apertures of both said first piece and said second
piece.
14. The femoral component of claim 12 wherein one of said one or
more abutment surfaces of said first piece extends transversely of
said first piece and superiorly from its said articulating surface
throughout only a portion of the thickness of said first piece and
further including a wall extending anteriorly from said first piece
one abutment surface and a first ledge spaced from said wall and
cooperating therewith to define an insert slot and wherein one of
said one or more abutment surfaces of said second piece extends
transversely of said second piece and superiorly from its said
articulating surface throughout only a portion of the thickness of
said second piece and an insert ledge extending from said second
piece one abutment surface and engaged in said insert slot.
15. The femoral component of claim 14 wherein one of said first
ledge or said insert ledge is provided with a slot and the other of
said first ledge or said insert ledge is provided with a tongue
received in said slot.
16. The femoral component of claim 15 wherein said slot and said
tongue are provided with mating reverse tapers.
17. The femoral component according to claim 16 wherein said insert
ledge extends only partially into said slot leaving a transverse
space between said insert ledge and said first piece and further
including an elongated member extending into said space.
18. A femoral knee prosthesis component for use with a tibial
component having an articulating surface comprising: (a) a condylar
piece having (i) a superior surface contoured to engage a prepared
surface at the distal end of a femur, (ii) an opposing articulating
surface contoured for sliding engagement with said tibial component
articulating surface and extending from (I) a posterior end to (II)
an abutment end; (b) a second piece having (i) a superior surface
contoured to engage a prepared surface at the distal end of a femur
(ii) an opposing articulating surface contoured for sliding
engagement by a natural of prosthetic patella and extending from
(I) an anterior end (II) an engagement end contoured for mating
engagement with said condylar piece abutment end; and (c)
engagement means for securing said condylar piece to said second
piece.
19. The prosthesis of claim 18 wherein said condylar piece abutment
end and said second piece engagement end are positioned to be
located, following implantation, in an area of low stress from
sliding engagement of said patella.
20. The prosthesis of claim 18 wherein said second piece comprises
(a) a condylar portion and (b) a patellar flange portion.
21. The prosthesis of claim 18 wherein said engagement means
includes (a) apertures in said condylar piece and said second
piece, and (b) a fastening member extending into apertures of both
said condylar piece and said second piece.
22. The prosthesis of claim 18 wherein said condylar piece includes
first and second spaced apart condylar portions joined together by
one or more cross members and said second piece is a patellar
flange member.
23. The prosthesis of claim 22 wherein said one cross member is
positioned adjacent said posterior end.
24. The prosthesis of claim 22 wherein said one cross member is
positioned at said abutment end.
25. The prosthesis of claim 24 wherein said cross member has (i) a
superior bone engaging surface, (ii) a medial surface spaced from
said superior bone engaging surface, and (iii) a second piece
engaging surface extending between said superior bone engaging
surface and said medial surface.
26. The prosthesis of claim 25 wherein said second piece includes a
laterally extending surface positioned between said second piece
superior surface and said second piece articulating surface, said
laterally extending. surface being engageable with said cross
member.
27. The prosthesis of claim 18 wherein said engagement means
includes a recess on one of said condylar piece or said second
piece and a projection engageable in said recess on the other of
said condylar piece or said second piece.
28. The prosthesis of claim 27 further including (i) apertures in
said condylar piece and said second piece, at least one aperture in
said projection and (ii) a fastening member extending into both an
aperture of said condylar piece and an aperture of said second
piece.
29. A tibial component for use in knee arthroplasty comprising (a)
a tibial base having (i) an inferior surface for engagement with a
prepared surface at the proximal end of a tibia and (ii) a
passageway extending through said base; (b) a tibial stem extending
distally from said base; and (c) means for engaging said stem to
said base.
30. The tibial component of claim 29 wherein said passageway in the
area of said tibial stem has a wall surface portion defining a
Morse taper and said tibial stem has a portion defining a Morse
taper sized to be snugly engaged in said passageway Morse taper
portion.
31. The tibial component of claim 30 wherein a threaded aperture is
provided in said tibial stem proximal end portion and further
including a screw extending through said tibial base passageway
engaged to said threaded aperture.
32. The tibial component of claim 30 wherein said passageway Morse
taper portion tapers outwardly in a distal direction.
33. The tibial component of claim 32 wherein a threaded aperture is
provided in said tibial stem proximal end portion and further
including a screw extending through said tibial base passageway
engaged to said threaded aperture.
34. The tibial component of claim 32 wherein said tibial stem is
provided with an outwardly facing annular groove spaced distally
from said Morse taper portion.
35. The tibial component of claim 30 wherein said passageway Morse
taper portion tapers inwardly in a distal direction.
36. The tibial component of claim 35 wherein a threaded aperture is
provided in said tibial stem proximal end portion and further
including a screw extending through said tibial base passageway
engaged to said threaded aperture.
37. The tibial component of claim 35 wherein said tibial base
passageway is enlarged proximally of said Morse taper portion to
define a shoulder extending outwardly from said Morse taper portion
and further including inwardly facing threads proximally of said
shoulder.
38. The tibial component of claim 37 wherein said tibial stem has a
flange portion proximally of said stem Morse taper portion and
outwardly facing threads engaged to said inwardly facing
threads.
39. The tibial component of claim 38 wherein said flange portion is
spaced from said shoulder when said stem Morse taper portion is
snugly engaged to said base Morse taper portion.
40. The tibial component of claim 29 further including alignment
means on said tibial base alignment with alignment means on said
tibial stem.
41. A tibial component for a knee prosthesis comprising (a) a
tibial base having an inferior surface for engaging prepared bone
at the proximal end of the tibia, an extension extending distally
from said inferior surface to a distal end, a passageway extending
through said tibial base, including through said extension, the
distal end of said passageway defining a Morse taper; (b) a tibial
stem extending from a proximal end to a distal end, said proximal
end defining a Morse taper receivable in said passageway Morse
taper.
42. The tibial component according to claim 41 wherein said tibial
stem has a recess extending from said proximal end toward said
distal end, said recess having threads or other retention means
formed therein and further including an engagement member extending
through said tibial base passageway and engaged to said threads or
other retention means.
43. The tibial component of claim 41 wherein said passageway Morse
taper portion tapers outwardly in a distal direction.
44. The tibial component of claim 43 wherein a threaded aperture is
provided in said tibial stem proximal end portion and further
including a screw extending through said tibial base passageway
engaged to said threaded aperture.
45. The tibial component of claim 44 wherein said tibial stem is
provided with an outwardly facing annular groove spaced distally
from said Morse taper portion.
46. The tibial component of claim 41 wherein said passageway Morse
taper portion tapers inwardly in a distal direction.
47. The tibial component of claim 46 wherein a threaded aperture is
provided in said tibial stem proximal end portion and further
including a screw extending through said tibial base passageway
engaged to said threaded aperture.
48. The tibial component of claim 46 wherein said tibial base
passageway is enlarged proximally of said Morse taper portion to
define a shoulder extending outwardly from said Morse taper portion
and further including inwardly facing threads proximally of said
shoulder.
49. The tibial component of claim 48 wherein said tibial stem has a
flange portion proximally of said stem Morse taper portion and
outwardly facing threads engaged to said inwardly facing
threads.
50. The tibial component of claim 49 wherein said flange portion is
spaced from said shoulder when said stem Morse taper portion is
snugly engaged to said base Morse taper portion.
51. The tibial component of claim 41 further including alignment
means on said tibial base alignable with alignment means on said
tibial stem.
52. A method of performing knee arthroplasty comprising the steps
of (a) providing a multi-piece femoral component, said femoral
component including (i) a first piece extending from an anterior
end to an engagement surface and having a patellar femoral flange
portion including an articulating surface and an opposed superior
bone engaging surface, (ii) a second piece defining at least one
condylar portion extending from a posterior end to an abutment
surface and having an inferior surface and an opposed superior bone
engaging surface, and (iii) means for securing said first piece and
said second piece together; (b) preparing the distal end of a femur
to receive said first piece and said second piece; (c) positioning
one of said first piece or said second piece on said prepared femur
distal end; (d) thereafter positioning the other of said first
piece or said second piece on said prepared femur distal end with
said engagement surface and said abutment surface in contact with
one another and cooperating to define a joint; and (e) securing
said first piece and said second piece together.
53. The method of claim 52 wherein step (e) is performed
simultaneously with step (d).
54. The method of claim 52 wherein step (e) is performed following
step (d).
55. A method of performing knee arthroplasty comprising the steps
of (a) providing a multi-piece tibial component, said tibial
component including (i) a tibial base having an inferior surface
for engagement with a prepared surface at the proximal end of a
tibia and a passageway extending through said base, (ii) a tibial
stem extending distally from said base, and (iii) means for
engaging said stem to said base; (b) preparing the proximal end of
a tibia including forming a cavity along the intramedullary canal
of said tibia; (c) positioning one of said tibial base or said
tibial stem on said prepared tibia; (d) thereafter positioning the
other of said tibial base or said tibial stem on said prepared
tibia; and (e) securing said tibial base and said tibial stem
together.
56. The method of claim 55 wherein said passageway includes a
portion in the area of said inferior surface which tapers outwardly
in a distal direction and said tibial stem includes a tapered
extension shaped to snugly engage said tapered portion of said
passageway including the steps of positioning said tibial stem in
said prepared cavity and thereafter positioning said tibial base on
said tibial stem with said tibial stem extension in said tapered
position.
57. The method of claim 56 further including the step of supporting
said tibial stem in said prepared cavity prior to positioning said
tibial base thereon.
58. The method of claim 56 wherein said tibial stem has an annular
groove distally of said tapered extension and further including the
step of engaging said groove with a tool to support said tibial
stem in said prepared cavity prior to positioning said tibial base
thereon.
59. The method of claim 56 wherein said tibial stem tapered
extension has a threaded cavity and further including the step of
extending a screw through said passageway and engaging it in said
threaded cavity.
60. The method of claim 55 wherein said passageway included a
portion which tapers inwardly in a distal direction and said stem
includes a tapered extension shaped to snugly engage the tapered
portion of said passageway and including the steps of positioning
said tibial base on said prepared tibia proximal end and thereafter
positioning said tibial stem through said passageway, into said
prepared cavity and into engagement with said tibial base.
61. The method of claim 60 wherein said tibial base has inwardly
facing threads and said tibial stem has outwardly facing threads
proximally of said tapered extension and further including the step
of engaging said outwardly facing threads to said inwardly facing
threads.
62. The method of claim 61 wherein said tibial component further
includes an insert engageable with said base, said insert having a
passageway and said tibial stem extension having a threaded cavity
and further extending a screw through said insert passageway and
engaging it in said extension threaded cavity.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims priority under
U.S. Provisional Application Serial No. 60/358,174 filed Feb. 20,
2002.
BACKGROUND OF THE INVENTION
[0002] In performing knee arthroplasty with conventional knee
prostheses, it has been necessary to form large incisions in order
to accommodate the preparation of the femur to receive the
prosthesis and to accommodate the reception of a fairly large
prosthesis into the incised femur for implantation on the prepared
distal end of the femur. As is appreciated by those skilled in the
art, it is desirable to minimize the size of any incision as the
smaller the incision, the more rapidly the patient may recover.
Prior art prostheses formed with a single piece metal component
having both left and right condylar portions integral with the
patellar flange area require large incisions in order to
accommodate implantation in the prepared femur. In contrast, under
the present invention, through the use of multiple pieces for the
femoral component, it is possible to greatly reduce the size of any
such incision, thereby reducing the amount of damage to soft tissue
from any such arthroplasty and speeding the time of recovery.
Similarly, it is desirable to minimize the size of any incision in
the tibia during any implantation of the tibial component.
SUMMARY OF THE INVENTION
[0003] The present invention is directed to a prosthesis for use in
knee arthroplasty including total knee arthroplasty which is
minimally invasive to the patient and to a method for performing
surgery using such prosthesis including the femoral and tibial
components thereof. Under the invention, the femoral component and,
preferably, the tibial component are manufactured in at least two
and possibly three or more pieces. However, it is possible that the
tibial component could be a single piece, monoblock construction as
well as modular multipiece construction. In both the single piece
and multipiece construction, there is also provided a plastic
articular surface insert piece. The pieces are designed to be
assembled together following insertion into the knee. This allows
total knee arthroplasty to be performed through very small
incisions, as small as three inches, in each of the distal end of
the femur and proximal end of the tibia. Following insertion, the
pieces of the femoral component implanted at the distal end of the
femur are joined together with a locking mechanism to form the
modular femoral component and the pieces of the tibial component
implanted at the proximal end of the tibia are assembled to form
the modular tibial component.
[0004] Femoral Component
[0005] The femoral component may have three component pieces for a
cruciate retaining design and two component pieces for a cruciate
sacrificing design. It may be manufactured as two or three separate
pieces or manufactured as a single unitary member which is
subsequently cut or otherwise divided into two or three separate
pieces. The pieces are provided with a locking joint for retaining
the pieces together following insertion in distal end of the femur.
The locking joint for the pieces is placed at the area of low
patella/femoral contact, a low stress area of the femur. This
corresponds to the anterior chamfer cut of a routine total knee
arthroplasty and the area can be easily reinforced to accommodate
the additional thickness of the locking joint. Various locking
mechanisms may be employed for joining the pieces together
including screws or a transverse locking pin which may be inserted
from the medial side and/or lateral side. The locking mechanisms of
whatever type lock the component pieces together into a solid
assembled prosthesis. The prosthesis will be additionally
reinforced by the underlying bone and/or cement fixation and will
produce a durable construction. The patellar flange and the area of
any joint between assembled components which may be contacted by
the patella should be smoothed and, possibly, recessed to prevent
premature wear of the patellar member as it tracks over the joint
in the femoral component.
[0006] Tibial Component
[0007] The tibial component preferably has two pieces, namely, a
tibial base and a tibial stem. It is also inserted in pieces from
the side. It may also be a monoblock, one-piece tibial component
with pegged or short stem fixation. The tibial base may have of a
flat baseplate with anterior and posterior dovetails and may have a
tapered transverse keel. The other piece of the tibial component is
a modular stem which is inserted from the top after the baseplate
is inserted. This design allows the components to be inserted
through the minimal incision and still have long term stability.
The stem is preferably fixed with a reverse Morse taper so that it
can be driven through the baseplate like a spike.
[0008] Patellar Component
[0009] A standard conforming dome configuration patellar component
is utilized, with the main difference being its method of
insertion. It may be inserted without everting the patella. This is
accomplished with the use of special instrumentation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of one embodiment of femoral
component showing the medial condyle as a separate piece from the
remainder of the femoral component.
[0011] FIG. 2 is a perspective view of a second embodiment of
femoral component showing the lateral condyle as a separate piece
from the remainder of the femoral component.
[0012] FIG. 2A is a sectional view showing a patellar member
engaged to the articulating surface of the patellar femoral flange
piece.
[0013] FIG. 3 is a perspective view of another embodiment of
femoral component showing both the medial condyle and the lateral
condyle as separate pieces from the patellar femoral flange piece
of the femoral component.
[0014] FIG. 4 is a perspective view showing the patellar femoral
flange piece of FIG. 3 taken from a different angle.
[0015] FIG. 5 is a perspective view of an embodiment of femoral
component showing the patellar femoral flange piece as a separate
piece from the remainder of the femoral component.
[0016] FIG. 6 is a front view of the embodiment of the femoral
component of FIG. 5.
[0017] FIG. 7 is a side view of the embodiment of the femoral
component of FIG. 5.
[0018] FIG. 8 is a sectional view taken through line 8-8 of FIG.
6.
[0019] FIG. 9 is a sectional view taken through line 9-9 of FIG.
6.
[0020] FIGS. 10 and 11 are perspective views of other embodiments
of the femoral component showing the patellar femoral flange piece
as a separate piece from the remainder of the femoral
component.
[0021] FIG. 11A is a view similar to FIG. 9 for the embodiment of
FIG. 11.
[0022] FIG. 11B is a sectional view through line 11B-11B of FIG. 11
A.
[0023] FIG. 12 is a perspective view of another embodiment of
femoral component showing the patellar femoral flange piece as a
separate piece from the remainder of the femoral component and
showing one form of design for connecting the patellar femoral
flange piece to the remainder of the femoral component.
[0024] FIG. 13 is an enlarged view of the circled portion of FIG.
12.
[0025] FIG. 14 is a perspective view of an embodiment of femoral
component showing the lateral condyle as a separate piece from the
remainder of the femoral component.
[0026] FIG. 15 is an enlarged view of the circled portion of FIG.
14.
[0027] FIG. 16 is a perspective view of another embodiment of
femoral component showing the patellar femoral flange piece as a
separate piece from the remainder of the femoral component.
[0028] FIG. 17 is an enlarged view of the circled portion of FIG.
16.
[0029] FIG. 18 is a perspective view of the tibial component
showing the stem portion thereof as a separate piece from the
base.
[0030] FIG. 18A is a view similar to FIG. 18 with the added feature
of a stem extension as part of the tibial component.
[0031] FIG. 19 is a sectional view of another embodiment of tibial
component showing the stem portion thereof as a separate piece from
the base.
[0032] FIG. 20 is a perspective view of another embodiment of
tibial component showing the stem portion thereof as a separate
piece from the base.
[0033] FIG. 21 is a side view of the tibial component of FIG. 20
showing its implantation in the proximal end of a prepared
tibia.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0034] Referring to FIG. 1, there is shown one embodiment of
femoral component generally designated by the numeral 10. The
femoral component includes a first piece 12 having a patellar
flange portion 14 and an integral, unitary lateral condyle portion
16 extending therefrom. A prior art femoral component would also
have an integral, unitary medial condyle on the opposite side from
the lateral condyle portion 16. Under the present invention, there
is provided, as a separate piece, a medial condyle piece 18
intended to be assembled to the first piece 12 following
implantation of both the first piece 12 and the medial condyle
piece 18 in the patient. The assembly mechanism or locking joint
for securing the medial condyle piece 18 to the first piece 12 will
be hereinafter described.
[0035] As shown in FIG. 1, the medial condyle piece 18 is provided
with a recess 15 for receiving bone cement and a pair of fixation
pins 17. The first piece 12 may also be provided with one or more
recesses and fixation pins. If it is desired to have a prosthesis
for implantation without bone cement, the recesses such as the
recess 15 can be replaced by one of several types of porous
surfaces well known in the art for bone in-growth.
[0036] Referring to FIG. 2, there is shown a second embodiment of a
femoral component 20 having a first piece 22 with a patellar
femoral flange portion 24 and an integral, unitary medial condyle
portion 26. The second component of this embodiment is a lateral
condyle piece 28 which may be joined with the first piece 22
following implantation of both the first piece 22 and the lateral
condyle piece 28 in the femur of the patient.
[0037] FIG. 2A shows a sectional view of patellar member P in
contact with the articulating surface of the patellar femoral
flange portion 24.
[0038] FIG. 3 shows yet another embodiment of a three-piece femoral
component 30. Under this embodiment, there is provided a patellar
femoral flange piece 32, a second piece 34 which is a medial
condyle piece and a third piece 36 which is a lateral condyle piece
assuming, of course, implantation in the right knee of a patient.
If the femoral component 30 were implanted in the left knee of a
patient, the second piece 34 would be the lateral condyle piece and
the third piece 36 would be the medial condyle piece. Each of the
second piece 34 and the third piece 36 are joined to the patellar
femoral flange piece 32 following insertion in the patient's femur
by use of a locking joint to be hereinafter described.
[0039] All three of the pieces of the femoral component may be
provided with fixation pins 37 and recesses 35 if intended for use
with bone cement or a porous surface if intended for non-cemented
implantation.
[0040] FIG. 4 is a perspective view of the patellar femoral flange
piece of FIG. 3 taken from a different angle.
[0041] The femoral components 10, 20 and 30 of FIGS. 1 through 3
could be used for implantation in either knee. The foregoing
description for each of the femoral components 10, 20 and 30 is
based on the assumption of implantation in the right knee. If they
were used for implantation in the left knee, the pieces identified
by the numerals 18 and 34 would be lateral condyle pieces, the
pieces identified by the numerals 28 and 36 would be medial condyle
pieces, the portion identified by the numeral 16 would be a medial
condyle portion and the portion identified by the numeral 26 would
be a lateral condyle portion.
[0042] Referring to FIGS. 5, 6, 7, 8 and 9, there is shown an
embodiment of femoral component 40 having two pieces, namely, a
patellar femoral flange piece 41 and a condylar piece 42. The
patellar femoral flange piece 41 has a patellar engaging surface 43
shaped to allow anatomical tracking of a natural or prosthetic
patella P. As shown in FIG. 5, the patellar femoral flange piece 41
has a superior bone engaging surface 46 and a patellar engaging
surface 43 defining a portion of an inferior articulating surface.
The patellar femoral flange piece 41 extends from an inferior end
45 to a leading end 48 which is contoured to engage the condylar
piece 42. The condylar piece 42 includes a first condylar portion
50 and a second condylar portion 52 and extends from an engagement
end 54 contoured to receive the leading end 48 of the patellar
flange 41 to a posterior end 55. As will be appreciated by those
skilled in the art, the femoral component 40 could be used for
implantation in either a right knee or left knee and the first and
second condylar portions will be either lateral or medial facing
depending upon the knee in which the femoral component 40 is
implanted.
[0043] The condylar piece 42 has a superior bone engaging surface
with a series of bone engaging flats 60, 61, 62 and 63 disposed at
varying angles consistent with cuts made in preparing the distal
end of the femur to receive the condylar piece 42. If desired, the
superior bone engaging surface 46 of the patellar flange piece 41
and the superior bone engaging surfaces 60, 61, 62 and 63 of the
condylar piece 42 may be formed with recesses for receiving bone
cement or porous surfaces for bone ingrowth and may also be
provided with fixation pins.
[0044] The condylar piece 42 in the embodiment of FIGS. 5-9 is
formed as a single unitary piece for implantation. As such, the
first condylar portion 50 and the second condylar portion 52 are
joined together with a posterior cam 56 which may be formed
integral with or welded or otherwise joined to the first and second
condylar portions 50, 52. The engagement end 54 of the condylar
piece 42 also has the first and second condylar portions 50, 52
joined together by a laterally extending cross member 57. As will
be appreciated by those skilled in the art, the use of the
posterior cam 56 will result in sacrificing of the posterior
cruciate ligament. As will be appreciated, in those cases where it
may be necessary to sacrifice the posterior cruciate ligament for
other reasons, the feature of having both a posterior cam 56 and a
cross member 57 for joining the first and second condylar pieces
50, 52 will provide great rigidity to the condylar piece 42.
[0045] As can be seen in FIGS. 5, 7 and 9, the cross member 57 has
a superior bone engaging surface 57A and a medial surface 57B
approximately midway between the superior bone engaging surface 57A
and the articulating surfaces 51 and 53 of the first condylar
portion 50 and second condylar portion 52, respectively. On the
posterior side of the cross member 57 is a posterior wall surface
57C extending between the superior bone engaging surface 57A and
the surface 57B. Opposite the posterior surface 57C is a fourth
surface 57D which will engage a corresponding surface to be
described of the patellar femoral flange piece 41.
[0046] The engagement ends 54 for each of the first and second
condylar portions 50, 52 each follows a curved path defined by
sidewall engagement surface 54A as shown in FIGS. 5 and 6. Each of
the curved engagement wall surfaces 54A extends to the general area
defined by the posterior wall surface 57C of cross member 57. (See
FIG. 5). The positioning of the joint defined by the surfaces 54A
of the condylar piece 42 and the mating surfaces of the patellar
femoral flange piece 41 is important and should be in the vicinity
of the normal femoral tide mark which is a low stress area of
contact by sliding engagement of the patella. By providing the
joint in this area, the prosthesis has great ability to function as
desired with no separation of the patellar femoral flange piece 41
from the condylar piece 42 following implantation. The normal
femoral tide mark corresponds to the area of the inferior chamfer
cut of a routine total knee arthroplasty.
[0047] The patellar femoral flange piece leading end 48 has a pair
of curved engagement surfaces 64 following a contour for mating
engagement with the respective surfaces 54A of the condylar piece
42. Centrally positioned between the curved engagement surfaces 64
is a central wall surface 65 which, when the patellar femoral
flange piece 41 is engaged to the condylar piece 42, lies in
substantially the same plane as the surface 57C of cross member 57.
(See FIG. 9). The central wall surface 65 extends superiorly from
the patellar engaging surface 43 to a ledge 66 intended to rest
upon the surface 57B of cross member 57. The ledge 66 extends away
from the central wall surface 65 to a central engagement surface 67
which is intended to engage the surface 57D of cross member 57. A
bone engaging surface 68 extends from the central engagement
surface 67 toward the anterior end 45.
[0048] As shown in FIGS. 6, 7 and 9, the condylar piece 42 may be
secured to the patellar femoral flange piece 41 by means of screws
68 extending through apertures 69 extending through engagement end
area 54 of the respective first and second condylar portions 50 and
52, through the engagement end surfaces 54A and into aligned
threaded apertures 71 extending inwardly from the curved engagement
surfaces 64 of the patellar femoral flange piece 41.
[0049] Referring to FIG. 8, there is shown the articulating surface
defined by the patellar engaging surface 43 of the patellar femoral
flange piece 41 and the articulating surface 59 of the condylar
piece 42 in the area of the joint defined by the mating surface 54A
of the condylar piece 42 and surface 64 of the patellar femoral
flange piece 41. As can be seen in FIG. 8, the respective surfaces
43 and 59 are recessed slightly at such joint to provide a slight
dip 73 so that any movement of the patellar member P over such
joint will leave a slight gap between the surface of the patellar
member P and the surfaces 43 and 59 at the dip 73.
[0050] The presence of the gap and the dip 73 has a two-fold
advantage. It reduces the amount of stress in that area of the
joint defined by the mating surfaces 54A and 64 at the surfaces 43
and 59. Additionally, if there is a slight mismating of the
patellar femoral flange piece 41 relative to the condylar piece 42
such that one of the surfaces 43 or 59 were slightly high or lower
than intended for precise fixation, the presence of the dip 73 will
serve to prevent the patellar member P from contacting and being
subjected to premature wear by a sharp corner of the higher
piece.
[0051] Referring to FIG. 10, there is shown a further embodiment
similar to that of FIGS. 5 through 9 but one in which there is
provided a condylar piece 42A having the first condylar portion 50A
is joined to the second condylar portion 52A only by a posterior
cam 56A. Under this embodiment, the patellar femoral flange piece
41A has a central wall surface 65A centrally positioned between
curved engagement surfaces 64A. The central wall surface 65A
extends throughout the thickness of the patellar femoral flange
piece 41A. Therefore, there is no ledge similar to the ledge 66
shown in FIG. 5. All other features of the embodiment of FIG. 10
are similar to corresponding features of the embodiment of FIGS. 5,
6, 7, 8 and 9.
[0052] Referring to FIGS. 11, 11A and 11B, there is shown a further
embodiment of femoral component 40B similar to that of FIGS. 5
through 9 but one in which there is provided a condylar piece 42B
having the first condylar portion 50B joined to the second condylar
portion 52B only by a cross member 57B and a modified connector
means for fastening the condylar piece 42B to the patellar femoral
flange piece 41B.
[0053] The cross member 57B is provided with an extension 130
extending superiorly (i.e., downwardly as viewed in FIGS. 11 and
11A) from the cross member 57B. Both the cross member 57B and the
extension 130 are provided with a common dovetail slot 132. The
extension 130 is an integral unitary part of the cross member 57B
and, in cross section, has a generally semicircular cross sectional
configuration with the side facing the patellar femoral flange
piece 41B having a pair of flat faces on opposite sides of the
dovetail slot 132.
[0054] The patellar femoral flange piece 41B, has a configuration
similar to that of the patellar femoral flange piece 41 as shown in
FIG. 5, including a central wall surface 65B extending from a
patellar engaging surface 43B, a ledge 66B and a central engagement
surface 67B. A bone engaging surface 68B extends from the central
engagement surface 67B toward the anterior end 45B. Extending
superiorly from the bone engaging surface 68B is an extension 134
having a dovetail 136 sized to be snugly received in the dovetail
slot 132 of the extension 130 with conforming mating surfaces. The
dovetail 136 and dovetail slot 132 could have other crossectional
configurations from that shown in FIGS. 11, 11A and 11B such as
circular or rectangular. As will be appreciated and as can be seen
from FIGS. 11A and 11B, the dovetail 136 is an integral unitary
part of the extension 134; however, it extends outwardly from the
surface 67B and upwardly from the surface 68B to join with surface
66B.
[0055] The respective extensions 130 of the condylar piece 42B and
134 of the patellar femoral flange piece 41B, when joined together
with the dovetail 136 positioned in the dovetail slot 132 will
cooperate to define a substantially cylindrical configuration;
however, if desired, a different configuration, such as square,
rectangular or rounded, could be utilized.
[0056] Preparatory to implantation of the condylar member 42B and
patellar femoral flange piece 41B, an aperture is drilled or
otherwise formed in the femur of sufficient size to receive the
extensions 130 and 134.
[0057] Following positioning of the condylar piece 42B in the
prepared femur with its extension 130 positioned in the prepared
bone cavity, the patellar femoral flange piece 41B is moved
therein, the dovetail 136 is aligned with the dovetail slot 132 and
the patellar femoral flange piece 41B is moved toward the prepared
femur with the dovetail 136 sliding through the dovetail slot 132
until the surface 66B of the patellar femoral flange piece 41B
contacts the anterior surface of cross member 57B. Desirably, bone
cement will be positioned in the prepared aperture of the femur to
engage the adjoined extensions 130 and 134.
[0058] Referring to FIGS. 12 and 13, there is shown an embodiment
of a two-piece femoral component 74 with a first piece 75 of a
patellar flange area having a patella engagement surface 76 and a
second piece 77 having a medial condyle portion 78 and a lateral
condyle portion 79 formed as an integral unitary piece. The second
piece 77 has a series of flats 96, 97, 98, 99 for engagement with a
prepared distal end of a femur.
[0059] The first piece 75 has an abutment wall 81 extending from
the patella engagement surface 76 and positioned to engage a
corresponding abutment wall 82 of the second piece 77. The line of
juncture between the abutment wall 81 of the first piece 75 and the
abutment wall 82 of the second piece 77 is in the area of low
patella/femoral contact which is a low stress area of the femur.
The abutment wall 81 extends only partially through the thickness
of the first piece 75. The abutment wall 81 joins with a second
wall 83 disposed substantially at right angles thereto (See FIG.
13). The second wall 83 extends to an end wall 84. Extending
outwardly from the end wall 84 toward the plane defined by the
abutment wall 81 is a ledge 85 having an upper surface 86 with a
tongue or dovetail 87 projecting upwardly therefrom. The tongue 87
and upper surface 86 extend throughout the breadth of the first
piece 75. The tongue 87 is provided with a pair of reverse taper
surfaces 88 which flare outwardly from one another in a direction
away from the upper surface 86.
[0060] Extending outwardly from the abutment wall 82 of the second
piece 77 is an insert ledge 90 having an upper surface for mating
engagement with the second wall 83 of the first piece 75. The lower
portion of the insert ledge 90 opposite the upper surface has
formed therein a dovetail groove 92 extending the full breadth of
the second piece 77 and sized to receive the tongue 87 of the first
piece 75. As can be seen from FIG. 13, when the first piece 75 and
second piece 77 are joined together, there will remain a gap 93
between the end wall 84 of the first piece 75 and the end of the
insert ledge 90 of the second piece 77. In order to prevent the
engaged first piece 75 and second piece 77 from moving laterally
relative to one another, there is provided a tapered pin 94 which
may be driven into the gap 93 to function as a wedge putting the
tongue 87 into compression in the dovetail groove 92 formed in the
lower surface of the insert ledge 90.
[0061] Referring to FIGS. 14 and 15, there is provided another
embodiment of prosthesis 100 with a first piece 101 having both a
patellar flange area 102 and an integral, unitary lateral condyle
portion 103. The prosthesis 100 also has a second piece 104 which
is a medial condyle piece. The first piece 101 has a first abutment
wall 105 extending generally laterally and a second abutment wall
106 extending generally longitudinally with a curved wall section
107 joining the first abutment wall 105 and the second abutment
wall 106. Protruding outwardly from the second abutment wall 106 is
a projection 110 having sidewalls 111 (only one of which is shown)
tapering inwardly toward one another as they extend outwardly from
the second abutment wall 106 and end walls 112 tapering inwardly
toward one another as they extend outwardly from the second
abutment wall 106. The tapering sidewalls 111 and end walls 112 are
joined by an outer wall 113 substantially parallel with the second
abutment wall 106. The projection 110 is integral and unitary with
the remainder of the first piece 101 and may be formed by a milling
process, for example. A threaded aperture 114 extends through the
projection 110 from the outer wall 113 and, preferably, extends
into the adjacent portion of the first piece 101.
[0062] The second piece 104 has a first abutment wall 115
positioned to engage the first abutment wall 105 of the first piece
101, a second abutment wall 116 positioned and sized to engage the
second abutment wall 106 of the first piece 101 and a curved wall
117 for engagement with the curved wall 107 of the first piece 101.
Formed in the second wall 116 is a recess 118 contoured to snuggly
receive the projection 110 of the first piece 101. A laterally
extending passageway 108 extends through the second piece 104 in
alignment with the threaded aperture 114 of the first piece 101
when the second piece 104 is engaged thereto.
[0063] In order to join the second piece 104 to the first piece 101
there is provided an elongated screw 120 having a threaded section
121 for mating with the threads of the threaded aperture 114 of the
first piece 101. The screw 120 has a cylindrical section 122 of
larger diameter than the threaded section 121 and sized to be
snugly received in the passageway 108 of the second piece. The
screw 120 has an enlarged head 123 sized to fit in a countersunk
area of the passageway 108 at the outer edge of the second piece
104.
[0064] Referring to FIGS. 16 and 17, there is shown a two-piece
femoral component 140 including a first piece 141 having both a
lateral condyle 142 and a medial condyle 143 formed as part of an
integral, unitary piece. The second piece 144 defines a patellar
flange area of the femoral component 140. The second piece 144 has
a contoured abutment wall 145 including a first flat surface 145A
extending inwardly from the lateral side, a second flat surface
145B extending inwardly from the medial side of the second piece
144 and a recess defined by first and second side walls 145C and a
bottom wall 145D. The sidewalls 145C taper inwardly toward one
another as they extend from their respective flat surfaces 145A and
145B to the bottom 145D. Preferably, the bottom wall 145D is
curved; however, it could be flat.
[0065] The first piece 141 is provided with an abutment wall 146
having a contour to be snuggly engaged to the abutment wall 145 of
the second piece 144. As such, the abutment wall 146 includes a
tongue 147 contoured to fit snuggly in the groove defined by
sidewalls 145C and bottom wall 145D of the second piece 144. The
tongue 147 is defined by sidewalls 146C, 146C and an end wall 146D
contoured to snuggly engaged the wall 145D forming the bottom of
the groove of the second piece 144. The walls 146C, 146C taper
inwardly toward one another as they extend toward the wall 146D and
snuggly engage the tapered sidewalls 145C of the second piece
144.
[0066] The second piece 144 has formed therein a first passageway
148A which extends inwardly from the lateral edge and is
substantially parallel to the first flat surface 145A and a second
passageway 148B which extends inwardly from the medial edge and is
substantially parallel to the second flat surface 145B. A
passageway 149 is formed in the tongue 147 in a position to be
aligned with the passageways 148A and 148B when the first piece 141
is engaged to the second piece 144, with the tongue 147 fitting in
the groove. A pin 150 may be inserted through the passageway 148B,
the passageway 149 and the passageway 148A to secure the first
piece 141 to the second piece 144. The pin 150 could be cylindrical
and press fit into the respective passageways 148A, 148B and 149
assuming the passageways were cylindrical or could be tapered
assuming such passageways had the appropriate taper. Additionally,
one of the passageways, passageway 148A, for example, could be
threaded, in which case the pin 150 would have a threaded end for
engagement therewith.
[0067] In each of the embodiments, the respective lines of juncture
between abutting walls of the assembled pieces have been selected
to be located generally in the area of the normal femoral tidemark
which is a low stress area.
[0068] Referring now to FIG. 18, there is shown a tibial component
generally designated by the numeral 161. The tibial component 161
includes a tibial base 162 and a tibial stem 163. The tibial base
162 has an inferior surface 164 intended to engage the prepared
proximal end of the tibia of the patient and a superior surface
(not shown) to which may be affixed a plastic insert contoured to
be engaged by the condylar portions of a femoral component. The
plastic insert may have one of a number of well known mechanisms
for being attached to the tibial base 162 such as a dove tail
locking mechanism, for example. The plastic insert may be inserted
either laterally or proximally depending on the specific design of
the tibial base and the condition of the patient as determined by
the surgeon. Extending distally from the inferior surface 164 is a
base extension 165 having a generally cylindrical shape but with a
pair of fixation wings or fins 166 extending outwardly from the
cylindrical portion of the base extension 165. A platform 167 is
raised from the inferior surface 164 and follows a contour
encircling the base extension 165 including the wings 166. The
wings 166 function as fixation fins for maintaining the tibial base
162 in a fixed rotational position when implanted on the prepared
proximal end of the tibia. The tibial base 162 is provided with a
notch 168 to accommodate the posterior cruciate ligament and a
plurality of apertures 169 for receiving screws for engagement to
an augmentation block, if one is needed, or for securing the tibial
base 162 to the proximal end of a prepared tibia.
[0069] The tibial base 162 has a central passageway 170 extending
from the superior surface 164 and through the cylindrical portion
of the base extension 165. That portion of the central passageway
170 in the base extension 165 has wall surface which flares
outwardly frusto conically and defines a Morse taper cavity 295 as
it approaches the end of the base extension 165. A recess defining
a notch 240 is formed in the end of the base extension 165. That
portion of the passageway adjacent the superior surface has a
diameter sized to receive a screw 158 and a countersunk area 297 to
receive the enlarged head of such screw 158.
[0070] The tibial stem 163 is provided with a pair of wings or
fixation fins 171 which, when the tibial stem 163 is engaged to the
extension 165, will be aligned with and forming extensions of the
respective wings or fins 166 of the tibial base 162. The tibial
stem 163 is provided with a Morse taper extension 298 sized to be
snugly received in the Morse taper cavity 295 of the tibial base
162. A shoulder 262 extends outwardly from the Morse taper
extension 298. A raised tab 242 extends proximally from the
shoulder 202 and is sized to fit snugly in the notch 210 and, when
so positioned, assures alignment of the fixation fins 171 of the
tibial stem 163 with the fins 166 of the tibial base 162.
[0071] A threaded passageway 172 is formed in the Morse taper
extension 298 and is aligned with the central passageway 170 when
the tibial stem 163 is engaged to the extension 165. The tibial
stem 163 is supported on the tibial base 162 by the screw 158
extending through the central passageway 170 of the tibial base 162
and engaged to the threaded passageway 172. A plug 244 is engaged
in the distal end of the tibial stem 163 to prevent blood or other
contaminates from entering the threaded passageway 172. The plug
244 may be secured to the tibial stem 163 by means of a threaded
extension engaging the threaded passageway 172.
[0072] FIG. 18A shows an embodiment similar to FIG. 18 but in which
there is provided a stem extension 250 but not a plug such as the
plug 244 of FIG. 18. The stem extension 250 is provided with a
Morse taper 252 at its proximal end 253. A threaded recess 254
extends distally from the proximal end and has a size smaller than
the threaded passageway 172. A threaded screw 258 sized to engage
the threaded recess 254 secures the stem extension 250 and the
tibial stem 163 to the tibial base 162. The threaded screw 258 is
small enough to pass through the threaded passageway 172 without
engaging its threads.
[0073] The distal end of the tibial stem 163 has a cavity 260
tapering outwardly in a distal direction and defining a Morse taper
sized to snuggly receive the Morse taper 252 of the stem extension
250. Two grooves 270 are formed in the tibial stem 163, on opposite
sides, distally spaced from the shoulder 262. The purpose of the
grooves 270 is to permit engagement and support for the tibial stem
during implantation as will be discussed hereinafter.
[0074] Referring to FIG. 19, there is a shown in section a modified
embodiment of tibial component 200. Under this embodiment there is
provided a tibial base 202, a tibial stem 204 and a plastic insert
206 for engagement with the tibial base 202. The tibial base, as
shown in FIG. 19, has a raised wall 208 and a flat superior surface
210. The tibial base 202 has an inferior surface 212 intended to
engage the prepared proximal end of the tibia of the patient. A
centrally positioned short extension 213 extends from the inferior
surface 212.
[0075] Extending through the tibial base 202 including the
extension 213 is a passageway 214. That portion of the passageway
214 adjacent the inferior surface 210 is enlarged from the
remainder of the passageway and is provided with inwardly facing
threads 215 in the area adjacent the inferior surface 210. That
portion of the passageway 214 extending away from the threads 215
is tapered to define a Morse taper cavity 216 throughout the
remainder of the thickness of the tibial base 202 including the
stem 213.
[0076] The tibial stem 204 is provided with an enlarged threaded
flange 220 sized to engage the threads 215 of the tibial base 202.
Extending from the flange 220 is a Morse taper extension 222 sized
and contoured to be snuggly received in the Morse taper cavity 216.
Extending inwardly from the inferior surface 210 is a cavity
defined by a series of flats 224 which cooperate to define a
hexagon or other conveniently shaped cavity for receipt of a tool
for engagement therein for threading the threaded flange 220 into
the threads 215.
[0077] Extending from the cavity defined by the flats 224 is a
threaded aperture 225. Extending distally from the Morse taper
extension 222 is a reduced size cylindrical extension 227.
[0078] The plastic insert 206 has molded therein a metal insert 230
having an enlarged flange 232 to ensure its firm engagement to the
insert 206. The insert 206 is provided with a passageway 234 sized
to receive a screw 236 including its enlarged head 238. The metal
insert 230 is provided with a passageway 240 sized to receive the
threaded portion of the screw 236 but smaller than the enlarged
head 238. Following engagement of the tibial stem 204 to the tibial
base 202, the plastic insert 206 is positioned on the inferior
surface 210 within the upwardly extending wall 208. The screw 236
is then engaged to the threaded aperture 225 to secure the plastic
insert 206 thereto.
[0079] In the surgical procedure for implanting the tibial
component 200, the proximal end of the tibia is prepared by cutting
a flat surface to receive the inferior surface 212 of the tibial
base 202 and a cavity is drilled in the intramedullary canal of the
tibia to receive. the stem 204. The tibial base 202 is positioned
on the prepared flat surface with the extension 213 positioned in
the cavity. The tibial stem 204 is then positioned in the
passageway 214 with the cylindrical extension 227 passing through
the Morse taper cavity 216 and into the cavity of the
intramedullary canal. Using a tool engaged to the flats 224, the
stem is threadedly engaged to the threads 215 and the base 202 to
cause the Morse taper extension 222 to firmly engage the Morse
taper cavity 216. As may be seen in FIG. 19, the tibial stem 204 is
so contoured relative to the tibial base 202, that a gap 229 will
remain between the distal side of the flange 220 and the surface of
the tibial base 202 extending radially outwardly from the Morse
taper cavity 216. This ensures that the Morse taper extension 222
will firmly engage the Morse taper cavity 216 upon threaded
engagement of the threaded flange 220 to the threads 215.
[0080] Referring now to FIGS. 20 and 21, there is shown another
embodiment of tibial component 180 along with a tool 195 for use in
implanting such tibial component in the proximal end of a prepared
tibia T. The tibial component 180 includes a tibial base 181, a
tibial stem 182 and a plastic insert 179 engaged to the tibial base
181. The tibial base 181 has an inferior surface 183 intended to
engage the prepared proximal end of the tibia T and a superior
surface 184 to which may be affixed a plastic insert 179 contoured
to be engaged by a femoral component. The tibial base 181 has
raised areas 185 along the anterior and posterior edges. Each of
the raised areas is provided with an undercut wall surface 186
defining grooves for receiving and retaining the plastic insert
179.
[0081] Extending distally from the inferior surface 183 is an
extension 187. The tibial base 181 has a central passageway 188
extending from the superior surface 184 and through the extension
187. The extension 187 and the passageway 188 may be disposed at an
angle of up to 100 relative to a line perpendicular to the superior
surface 184 in order to accommodate the anatomy of the patient.
[0082] The tibial stem 182 is provided with a recess 190 sized and
positioned to become an extension of the passageway 188 of the
tibial base 181. The recess 190 may be threaded for engagement by a
threaded screw 196 extending through the plastic insert 179 and its
articular surface and through the passageway 188 to join the tibial
stem 182 to the tibial base 181. As shown in FIG. 21, the distal
end 188A of the passageway 188 may be tapered to define a Morse
taper cavity. The tibial stem 182 is also provided, at its proximal
end, with a Morse taper extension 197 sized to snugly engage the
Morse taper cavity at the distal end 188A of the passageway 188.
The tibial stem 182 is also provided with a plurality of outwardly
facing grooves 189 to assist in fixation.
[0083] In preparing the proximal end of the tibia T to receive the
tibial component 180, the proximal end T1 of the tibia is cut to
form substantially a flat surface. A cavity T2 is formed to receive
the tibial stem 182. Since the cavity T2 may be oversized, the
tibial stem 182 is provided with an annular groove 198 sized to
receive the tines 195A of the tool 195. As can be seen in FIG. 21,
with the tines 195A engaged in the groove 198, the tool 195 can
support the tibial stem 182 at the proper location relative to the
prepared proximal end T1 of the tibia T until such time as the
screw 196 is engaged in the threaded recess 190 to support such
tibial stem 182 on the tibial base 181.
[0084] In implanting the tibial stem 163 of the embodiment of FIGS.
18 and 18A, a tool similar to the tool 195 may be used to engage
the grooves 270 to support the stem 163 until it is engaged by the
screw 158 or 258.
[0085] In each of the embodiments of FIGS. 18, 18A, 19, 20 and 21,
it is preferred that the surface of the tibial base which is to be
contacted by a plastic insert be polished to a high degree, on the
order of four (4) rms or less, to prevent premature wear on the
surface of the plastic insert engaged to the tibial base.
[0086] Description of Surgical Procedure
[0087] A medial parapatellar incision is made from the superior
pole of the patella to the tibial tuberosity. Medial parapatellar
arthrotomy is made from the inferior edge of the vastus medial is
to the tibial tuberosity. A subvastus or mid vastus arthrotomy may
be utilized, based upon patient anatomy or surgeon experience.
[0088] The knee is place in extension and the patella excised
without eversion, using a patellar clamp inserted into the
prepatellar bursa, to prevent damage to the anterior skin.
[0089] An extramedullary tibial alignment guide is placed along the
medial or lateral half of the tibia and secured with fixation pins.
An extrameduallary alignment guide of the type disclosed in
application Ser. No. 09/973,584 filed Oct. 9, 2001, assigned to the
assignee of the present invention and incorporated herein by
reference, is fixed to the femur after performing the
extramedullary alignment procedure, and the distal femoral cut is
made at the appropriate depth and angle of the implant, nominally
6.degree. valgus and 10-12 mm depth of cut. As an alternative, an
intramedullar alignment guide system could be used. This cut is
taken all the way across both distal femoral condyles, rather than
being unicondylar in nature. This cut is made at 90.degree. to the
femoral shaft.
[0090] The tibial component is implanted first. The fixation
surface is coated with cement, and the modular tibial stem is
driven through the reverse Morse taper to lock the tibial stem to
the bone.
[0091] The anterior flange component is then implanted, followed by
the lateral then medial condyles. Once all pieces are loosely
assembled inside the knee and proper alignment is assured, the
locking pin is inserted from the side and rigidly fixes the
components together. Final impaction is then accomplished.
[0092] Lastly, the patella is cemented in place.
[0093] After all cement has hardened and excess is removed, the
final poly slides in from the side, and is secured with an AP
locking clip or screw, which also helps lock the modular stem in
place.
[0094] Routine closure is performed, and rapid rehab program
initiated.
[0095] The above detailed description of the present invention is
given for explanatory purposes. It will be apparent to those
skilled in the art that numerous changes and modifications can be
made without departing from the scope of the invention.
* * * * *