U.S. patent application number 11/956998 was filed with the patent office on 2008-04-24 for constrained prosthetic knee with rotating bearing.
This patent application is currently assigned to ZIMMER TECHNOLOGY, INC.. Invention is credited to Jerry L. Aikins, Rodney L. Bays, Michael Cook, Marvin Figueroa, Adam Griner, Bill H. Haywood, G. Doug Letson, John E. Meyers, Bill N. Sisk, Peter S. Walker, Vincent A. Webster, Russell Windsor.
Application Number | 20080097616 11/956998 |
Document ID | / |
Family ID | 33492592 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080097616 |
Kind Code |
A1 |
Meyers; John E. ; et
al. |
April 24, 2008 |
CONSTRAINED PROSTHETIC KNEE WITH ROTATING BEARING
Abstract
A constrained prosthetic knee having a modular hinge post and a
rotating bearing. A cannulated hinge post is rotatably connected to
the femoral component of the knee prosthesis so that a hinge post
extension may be anteriorly positioned through the hinge post and
into the tibial component of the knee prosthesis, after positioning
of the femoral component in the femur and the tibial component in
the tibia. The hinge post is preassembled to the femoral component
so that such assembly is not required during the implantation
procedure. A meniscal component forming the rotating bearing of the
knee prosthesis is packaged together with the hinge post extension
so that the appropriate hinge post extension is readily available.
The meniscal component includes a mechanism for preventing lift off
of the meniscal component from the tibial component, while allowing
rotation of the meniscal component relative to the tibial
component.
Inventors: |
Meyers; John E.; (Columbia
City, IN) ; Letson; G. Doug; (Tampa, FL) ;
Windsor; Russell; (Larchmont, NY) ; Webster; Vincent
A.; (Warsaw, IN) ; Sisk; Bill N.; (Claypool,
IN) ; Haywood; Bill H.; (Warsaw, IN) ; Griner;
Adam; (Columbia City, IN) ; Cook; Michael;
(Claypool, IN) ; Bays; Rodney L.; (Pierceton,
IN) ; Aikins; Jerry L.; (Warsaw, IN) ;
Figueroa; Marvin; (Warsaw, IN) ; Walker; Peter
S.; (New York, NY) |
Correspondence
Address: |
ZIMMER TECHNOLOGY - BAKER & DANIELS
111 EAST WAYNE STREET, SUITE 800
FORT WAYNE
IN
46802
US
|
Assignee: |
ZIMMER TECHNOLOGY, INC.
P.O. BOX 708 345 East Main Street
Warsaw
IN
46582
|
Family ID: |
33492592 |
Appl. No.: |
11/956998 |
Filed: |
December 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10805056 |
Mar 19, 2004 |
|
|
|
11956998 |
Dec 14, 2007 |
|
|
|
10001000 |
Nov 2, 2001 |
6719800 |
|
|
10805056 |
Mar 19, 2004 |
|
|
|
09771061 |
Jan 29, 2001 |
6485519 |
|
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10001000 |
Nov 2, 2001 |
|
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|
Current U.S.
Class: |
623/20.29 ;
623/20.14 |
Current CPC
Class: |
A61F 2/3868 20130101;
A61F 2/385 20130101 |
Class at
Publication: |
623/020.29 ;
623/020.14 |
International
Class: |
A61F 2/38 20060101
A61F002/38 |
Claims
1. A prosthetic femoral component, comprising: a femoral component
body; a hinge post rotatably connected to said femoral component
body, said hinge post rotatable relative to said femoral component
body about an axis of rotation, said hinge post including an
elongate aperture, said elongate aperture transverse to said axis
of rotation.
2. The prosthetic femoral component of claim 1, further comprising:
a hinge post extension, said elongate aperture of said hinge post
sized for placement of said hinge post extension therein, whereby
said hinge post extension traverses a first end of said elongate
aperture of said hinge post and protrudes from a second end of said
elongate aperture of said hinge post, said first and second ends of
said elongate aperture of said hinge post comprising opposing ends
of said elongate aperture of said hinge post.
3. The prosthetic femoral component of claim 2, further comprising:
securing means for securing said hinge post extension to said hinge
post.
4. The prosthetic femoral component of claim 3, wherein said
securing means comprises: a male taper positioned on said hinge
post extension; and a female taper positioned in said elongate
aperture, said male taper engageable in said female taper to secure
said hinge post extension to said hinge post.
5. The prosthetic femoral component of claim 1, further comprising:
a bearing box connected to said femoral component body, said
bearing box interposed between said hinge post and said femoral
component body, said bearing box including a hyperextension stop,
said hinge post including a hyperextension stop surface, said
hyperextension stop contacting said hyperextension stop surface to
prevent further hyperextension of the prosthetic femoral component
body beyond a predetermined point of hyperextension.
6. The prosthetic femoral component of claim 5, wherein said
predetermined point of hyperextension comprises four degrees of
hyperextension of the prosthetic knee body.
7. The prosthetic femoral component of claim 5, wherein said
hyperextension stop comprises a convex protrusion.
8. The prosthetic femoral component of claim 5, wherein said hinge
post includes an internal wall, said hyperextension stop surface
comprising said internal wall of said hinge post.
9. The prosthetic femoral component of claim 2, further comprising:
a male taper positioned on said hinge post extension; and a female
taper positioned in said elongate aperture, said male taper
engageable in said female taper to secure said hinge post extension
to said hinge post.
10. The prosthetic femoral component of claim 1, further
comprising: a set screw, said first end of said elongate hinge post
extension aperture being threaded, whereby said set screw will
engage the threads of said elongate hinge post extension aperture,
said hinge post extension including a locking taper, a hinge post
extension aperture including a cooperating taper, whereby threading
of said set screw into said elongate hinge post extension aperture
forces said locking taper into locking engagement with said
cooperating taper.
11. The prosthetic femoral component of claim 1, wherein said hinge
post is rotatably connected to said femoral component body via a
hinge pin, said hinge post rotatable about a longitudinal axis of
said hinge pin, said hinge pin including an indentation on a first
end thereof, and a hinge pin plug positioned within said
indentation and being flush with said first end of said hinge
pin.
12. The prosthetic knee of claim 11, wherein said hinge pin plug is
formed from an ultra-high molecular polyethylene.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of patent application Ser. No.
10/805,056 filed Mar. 19, 2004, which is a continuation of patent
application Ser. No. 10/001,000 filed Nov. 2, 2001, now U.S. Pat.
No. 6,719,800, which is a continuation-in-part of patent
application Ser. No. 09/771,061 filed Jan. 29, 2001, now U.S. Pat.
No. 6,485,519, the disclosures of which are expressly incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to prosthetic joints, and,
more particularly to a constrained prosthetic knee having a modular
hinge post and a rotating bearing.
[0004] 2. Description of the Related Art
[0005] Generally, the knee is formed by the pair of condyles at the
distal portion of the femur, the lower surfaces of which bear upon
the correspondingly shaped proximal surface plateau of the tibia.
The femur and tibia are connected by means of ligaments such as,
the posterior cruciate ligament, the lateral collateral ligament,
the medial collateral ligament, and the anterior cruciate ligament.
These ligaments provide stability to the joint formed by the femur
and tibia (i.e., the knee).
[0006] In a broad sense, prosthetic knee joints can be considered
either constrained or unconstrained. For the purposes of this
discussion, constrained prosthetic knees include femoral and tibial
prosthetic components which are mechanically linked or constrained
to each other by a hinge structure. An unconstrained prosthetic
knee includes femoral and tibial components which are not
mechanically linked. An unconstrained knee utilizes the patient's
existing ligaments to provide joint stability. With this in mind,
constrained prosthetic knees have particular applicability to cases
in which a patient has experienced ligament loss and/or the
existing ligaments do not provide adequate support and stability to
the knee.
[0007] Tibial components of a prosthetic knee can be formed as a
one-piece configuration in which the tibial tray forms the meniscal
component of the prosthetic knee. Various other prosthetic knees
utilize a modular meniscal component separate from the tibial
component. Devices utilizing modular meniscal components include
those in which the meniscal component (i.e., tibial bearing
surface) is fixed to the tibial tray portion of the tibial
component and is incapable of movement relative thereto.
Alternative devices utilize a modular meniscal component capable of
movement relative to the tibial tray. Devices in which relative
rotational movement occurs between the meniscal component and the
tibial component are typically referred to as rotating bearing
knees. Rotating bearing knees thus allow movement between the
bearing (i.e., meniscal component) and the tibial tray, as well as
movement between the femoral component and the tibial bearing.
[0008] Constrained knees of the prior art include constructions in
which a hinge post extension is first positioned within a tibial
component (with an end protruding therefrom) and is thereafter
connected to the femoral component by positioning the hinge post
(rotatably attached to the femoral component) over the top of the
protruding end of the hinge post extension and thereafter
connecting the hinge post extension to the hinge post, e.g., by
threading the hinge post extension into the hinge post. After
making this connection, the meniscal component is thereafter slid
into position between the femoral component and the tibial
component. Meniscal components utilized with these prior art
prosthetic knees are fixed to the tibial component.
[0009] The present invention is directed to a constrained knee
prosthesis with a rotating bearing. The knee prosthesis of the
present invention is structured to facilitate implantation thereof.
The present invention is further directed to a prosthetic knee
implant set having a plurality of matched modular hinge post and
meniscal component pairs.
SUMMARY OF THE INVENTION
[0010] The present invention provides an improved constrained knee
prosthesis having a cannulated hinge post facilitating implantation
of the knee prosthesis in a relatively minimally invasive
procedure. The prosthetic knee implant set of the current invention
includes a separately packaged femoral component, a separately
packaged tibial component, and a third package containing a hinge
post extension and the meniscal component. Packaging the individual
components of a knee prosthesis in this fashion insures that the
appropriate hinge post extension is readily available. A bearing
box is interposed between the hinge post and the femoral component.
The bearing box includes a hyperextension stop which cooperates
with the hinge post to prevent hyperextension of the knee
prosthesis. Various structures are utilized to prevent the
disengagement of the constrained knee prosthesis of the present
invention.
[0011] A prosthetic knee constructed in accordance with the present
invention includes a femoral component having a pair of condyler
surfaces and a hinge post rotatably connected to the femoral
component between the condyler surfaces. The hinge post is
cannulated and accommodates insertion of a hinge post extension
shaft therein. The hinge post and hinge post extension include
cooperating locking tapers for locking the hinge post extension to
the hinge post. Additionally, the hinge post includes internal
threads so that a set screw may be threaded therein to further hold
the hinge post extension in place. In one exemplary embodiment, the
proximal end of the hinge post extension is threaded to facilitate
locking the hinge post extension to the hinge post. The tibial
component includes a hinge post extension aperture into which the
hinge post extension is seated. The meniscal component similarly
includes an aperture to accommodate the hinge post and hinge post
extension. The meniscal component of the current invention is free
to rotate about the hinge post during flexion and extension of the
knee joint.
[0012] Having a cannulated hinge post through which a hinge post
extension may be anteriorly positioned and secured advantageously
allows for a relatively minimally invasive knee replacement
procedure.
[0013] The present invention advantageously provides a constrained
prosthetic knee having a rotating bearing flush with the condyler
surfaces of the femoral component.
[0014] Another advantage of the present invention is the packaging
of the prosthesis components and specifically the packaging of the
appropriate hinge post extension together with a meniscal
component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above-mentioned and other features and advantages of
this invention, and the manner of attaining of them, will become
more apparent and the invention itself will be better understood by
reference to the following description of an embodiment of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0016] FIG. 1 is a perspective view of an assembled knee prosthesis
in accordance with the present invention;
[0017] FIG. 2 is an exploded view thereof;
[0018] FIG. 2A is a perspective view of a hinge post extension of
the present invention;
[0019] FIG. 3 is a cutaway, exploded view illustrating assembly of
the knee prosthesis of the current invention including the anterior
positioning of the hinge post extension into the hinge post;
[0020] FIG. 4 is a cutaway view illustrating securement of the
hinge plug (i.e., set screw) in the hinge post to facilitate
locking of the hinge post extension therein;
[0021] FIG. 5 is a cutaway, exploded view illustrating removal of
the hinge post extension;
[0022] FIG. 6 is a bottom elevational view of the meniscal
component of the present invention;
[0023] FIG. 7 is a front elevational view thereof;
[0024] FIG. 8 is a top elevational view of a tibial component in
accordance with the present invention;
[0025] FIG. 9 is a sectional view of a hinge plug in accordance
with the present invention;
[0026] FIG. 10 is a side elevational view of a bearing box in
accordance with the present invention;
[0027] FIG. 11 is a front elevational view thereof;
[0028] FIG. 12 is a top elevational view thereof;
[0029] FIG. 13 is a cutaway, exploded view of an alternative
embodiment of the knee prosthesis of the present invention;
[0030] FIG. 14 is a cutaway view of an assembled knee prosthesis in
accordance with the embodiment illustrated in FIG. 13;
[0031] FIG. 15 is a fragmentary, cutaway view of an alternative
embodiment of the hinge post extension and tibial bushing of the
present invention;
[0032] FIG. 16 is a fragmentary, cutaway view of the embodiment of
FIG. 15 illustrating insertion of the hinge post extension into the
tibial bushing;
[0033] FIG. 17 is a fragmentary, cutaway view of the embodiment of
FIG. 15 illustrating the hinge post extension fully inserted into
the tibial bushing;
[0034] FIG. 18 is an exploded view of an alternative embodiment of
the knee prosthesis of the current invention;
[0035] FIG. 19 is a sectional view of a meniscal component in
accordance with an alternative embodiment of the present
invention;
[0036] FIG. 20 is an elevational view of a hinge post in accordance
with an alternative embodiment of the present invention;
[0037] FIG. 21 is a top elevational view of a meniscal component in
accordance with the present invention;
[0038] FIGS. 22, 23, 24, and 25 are bottom, back, front, and side
elevational views thereof; respectfully;
[0039] FIG. 26 is a sectional view thereof;
[0040] FIG. 27 is a sectional view illustrating initial placement
of a meniscal component of the present invention on a tibial
component of the present invention;
[0041] FIGS. 28-30 are sectional views progressively illustrating
placement of a meniscal component of the present invention on a
tibial component of the present invention, whereby the meniscal
component is operable to rotate relative to the tibial component
when operably positioned thereon, but is constrained from movement
in an axial direction relative to the tibial stem, i.e., the
meniscal component will not lift away from the tibial
component;
[0042] FIG. 31 is a top elevational view of a tibial component in
accordance with the present invention;
[0043] FIGS. 32, 33, 34, and 35 are bottom, back, front, and side
elevational views thereof, respectively; and
[0044] FIG. 36 is a sectional view thereof.
[0045] Corresponding reference characters indicate corresponding
parts throughout the several views. Although the drawings represent
embodiments of the invention, the drawings are not necessarily to
scale and certain features may be exaggerated to better illustrate
and explain the invention. The exemplifications set out herein
illustrate embodiments of the invention, in alternative forms, and
such exemplifications are not to be construed as limiting the scope
of the invention in any manner.
DETAILED DESCRIPTION
[0046] Referring now to the drawings and particularly to FIG. 2,
knee prosthesis 20 in accordance with the present invention is
illustrated. Knee prosthesis 20 generally includes femoral
component 22, tibial component 24, and meniscal component 26. Hinge
post 40 is rotatably connected to femoral component 22 and includes
elongate hinge post extension aperture 112 (FIGS. 3-6, 13, and 14).
Elongate aperture 112 accommodates placement of hinge post
extension 42 therein. Hinge post extension 42 thereafter traverses
hinge post aperture 114 in meniscal component 26 and hinge post
extension aperture 110 (FIGS. 3-6, 13 and 14) in tibial component
24. Elongate hinge post extension aperture 112 of hinge post 40
advantageously allows for anterior placement of hinge post
extension 42 during surgical implantation of knee prosthesis 20 of
the present invention.
[0047] As illustrated in FIG. 2, hinge post extension 42 includes
locking taper 46 and cylindrical extension 48. Hinge post extension
aperture 112 includes a mating locking taper to cooperate with
locking taper 46 and lock hinge post extension 42 to hinge post 40.
After positioning hinge post extension 42 through apertures 112,
114, and 110, hinge plug 38 may be threaded into hinge plug threads
54 in elongate aperture 112 of hinge post 40 (FIG. 4). Hinge plug
38 abuts the end of hinge post extension 42 and thereby facilitates
locking of morse taper 46 in elongate aperture 112. In one
exemplary embodiment, locking taper 46 comprises a two degree
locking taper. In an alternative embodiment, the hinge post
extension includes integral threads to facilitate locking of the
hinge post extension to the hinge post. As illustrated in FIG. 2A,
hinge post extension 42B includes locking taper 46B as well as
threaded proximal end 150. If hinge post extension 42B is utilized,
hinge plug 38 is unnecessary. When prosthetic knee 20 is assembled
as illustrated in FIG. 1, condyler bearing surfaces 28, 30 abut
bearing surfaces 86, 88 (see, e.g., FIG. 2) of meniscal component
26.
[0048] Hinge post extension 42 is typically formed as a one-piece
construction of an inert metal such, e.g., a cobalt-chromium alloy.
Hinge post extension 42 may, however, be constructed of other
bio-compatible metals or alloys, such as titanium. Throughout this
document reference will be made to various components formed of a
cobalt-chromium alloy. Any such component may also be constructed
of other bio-compatible metals or alloys such as titanium, as is
well-known. As illustrated in FIG. 4, hinge plug wrench 102 is
utilized to thread hinge plug 38 into hinge plug threads 54 of
hinge post 40. As illustrated in FIG. 9, hinge plug 38 includes
locking material 100 to provide a locking connection between hinge
plug 38 and hinge plug threads 54 in hinge post 40. Hinge plug 38
is, in one exemplary embodiment formed of a cobalt-chromium alloy.
Locking material 100 comprises any suitable biocompatible polymer
such as, e.g., ultra-high molecular weight polyethylene
(UHMWPE).
[0049] As illustrated, e.g., in FIG. 2, femoral component 22
includes condyler bearing surfaces 28, 30 with bearing box wall 76
positioned therebetween. Femoral component 22 further includes
external side walls 82, only one of which can be seen in FIG. 2.
Condyler bearing surfaces 28, 30 are smooth and highly polished,
generally spheroidally shaped and extend outwardly from external
side walls 82, as is well known in the industry. Femoral component
22 further includes modular femoral stem 32 for insertion into
femur 116 (FIGS. 3-5, 13, and 14), as is known in the art. Femoral
component 22 further includes internal side walls 80, only one of
which is illustrated in FIG. 2. Internal side walls 80 are
substantially perpendicular to bearing box wall 76 and extend
outwardly therefrom. Femoral component 22 is typically formed as a
one-piece construction of an inert metal such as, e.g., a
cobalt-chromium alloy.
[0050] Bearing box 70 is designed for placement between condyler
bearing surfaces 28, 30 of femoral component 22 as illustrated,
e.g., in FIG. 1. Bearing box 70 is further illustrated in FIGS.
10-12 and includes affixing protrusions 72, hinge pin aperture 62,
hyperextension stop 66, and anti-rotation surface 78. As
illustrated in FIG. 2, femoral component 22 includes affixing
protrusion apertures 74 sized to receive affixing protrusions 72.
FIG. 1 illustrates bearing box 70 operably positioned on femoral
component 22, with anti-rotation surface 78 flush with bearing box
wall 76 of femoral component 22, and affixing protrusions 72
received in affixing protrusion apertures 74. The abutting
relationship of anti-rotation surface 78 with bearing box wall 76
discourages rotation of bearing box 70 about the longitudinal axis
of affixing protrusions 72. When bearing box 70 is positioned on
femoral component 22, hinge pin apertures 62 of bearing box 70
align with threaded hinge pin aperture 56 and hinge pin aperture 58
of femoral component 22. Bearing box 70 can be formed of any
suitable plastic, such as, e.g., UHMWPE.
[0051] Hinge post 40 is rotatably connected to femoral component 22
via hinge pin 34. Hinge post 40 is placed between opposing walls of
bearing box 70 and is positioned so that hinge pin aperture 52 is
aligned with apertures 56, 58, and 62. The opposing walls of
bearing box 70 thus act as a bearing surface between hinge post 40
and internal side walls 80 of femoral component 22. Prior to
placement of hinge post 40 between opposing walls of bearing box
70, hinge pin sleeve 36 is operably positioned within hinge pin
aperture 52 of hinge post 40. Hinge post 40 is formed from a
cobalt-chromium alloy, while hinge pin sleeve 36 is formed from a
suitable plastic, such as, e.g., UHMWPE. Hinge pin sleeve 36 acts
as a bearing between hinge pin aperture 52 of hinge post 40 and
hinge pin 34. Accordingly, hinge pin sleeve 36 includes hinge pin
aperture 50 sized to accommodate hinge pin 34. After positioning
hinge post 40 between the opposing walls of bearing box 70, hinge
pin 34 is positioned through apertures 56, 62, 50, and 58. Hinge
pin threads 60 are thereafter threadedly engaged in the threads of
threaded hinge pin aperture 56 until the head of hinge pin 34 is
flush with external side wall 82.
[0052] As illustrated in FIG. 1, hinge pin plug 120 is positioned
within the hexagonal indentation of hinge pin 34 after installation
of hinge pin 34 as described above. When positioned within the
hexagonal indentation of hinge pin 34, hinge pin plug 120 is flush
with the head of hinge pin 34. In use, hinge pin plug 120
substantially prohibits the entry of foreign materials into the
hexagonal indentation of hinge pin 34. For example, hinge pin plug
120 substantially prohibits bone growth into the hexagonal
indentation of hinge pin 34, as well as prohibiting positioning of
bone cement therein. The above-described connection of hinge post
40 to femoral component 22 is performed prior to implantation of
femoral component 22. Femoral component 22 is packaged and sold
with bearing box 70, hinge post 40, hinge pin sleeve 36, hinge pin
34, and hinge pin plug 120 preassembled as described above, with
the assembly preferably occurring in the manufacturing
environment.
[0053] Pre-assembly of hinge post 40 to femoral component 22
eliminates a number of meticulous assembly steps (many of which
were performed during implantation) which were required with
constrained knees of the prior art. Furthermore, the assembly of
hinge post 40 and femoral component 22 as described above
facilitates replacement of various portions of knee prosthesis 20.
Specifically, the threaded connection of hinge pin 34 to femoral
component 22 allows for removal and replacement of various
components of knee prosthesis 20 including, e.g., bearing box 70,
hinge pin sleeve 36, and hinge post 40.
[0054] In use, femoral bone stock may abut external side walls 82
of femoral component 22 and extend to the underside of condyler
bearing surfaces 28, 30. To remove hinge pin 34, a hole saw is
utilized to remove a relatively small portion of femoral bone stock
to provide access to hinge pin 34. Advantageously, femoral
component 22 does not require extensive removal of femoral bone
stock for implantation thereof (since bone stock can extend to the
underside of condylar bearing surfaces 28, 30), and, furthermore,
does not require removal of femoral component 22 to effect
replacement of, e.g., hinge post 40, bearing box 70, or hinge pin
sleeve 36. Upon accessing hinge pin 34 (e.g., utilizing a hole saw
as described above), hinge pin plug 120 is removed, e.g., with a
scalpel and forceps to provide access to the hexagonal indentation
of hinge pin 34 so that a hexagonal wrench may be inserted therein
to unthread hinge pin 34 from femoral component 22.
[0055] Knee prosthesis 20 includes a pair of hyperextension stop
mechanisms. The first hyperextension stop comprises a portion of
condylar bearing surfaces 28, 30 of increased radius of curvature
as compared to the remaining condylar bearing surface. At three
degrees of hyperextension this portion of increased radius of
curvature will contact meniscal component 26 and act to retard
further hyperextension. If hyperextension continues, the area of
increased radius of curvature will cause femoral component 22 to
lift away from meniscal component 26. The second hyperextension
stop mechanism functions at four degrees of hyperextension to
prohibit further hyperextension of knee prosthesis 20. The second
hyperextension stop mechanism comprises hyperextension stop surface
66 of hinge post 40 and hyperextension stop 68 of bearing box 70.
Hyperextension stop surface 66 comprises the concave back wall of
cannulated hinge post 40 as illustrated, e.g., in FIGS. 2 and 3.
Hyperextension stop 68 of bearing box 70 comprises a protrusion
extending from the back wall of bearing box 70 opposite
anti-rotation surface 78. Hyperextension stop 68 includes a convex
outer surface as illustrated, e.g., in FIG. 12. Hyperextension stop
surface 66 of hinge post 40 cooperates with hyperextension stop 68
of bearing box 70 to provide a hyperextension stop for knee
prosthesis 20. Concave hyperextension stop surface 66 becomes flush
with the convex outer surface of hyperextension stop 68 of bearing
box 70 at four degrees of hyperextension to prevent further
hyperextension of knee prosthesis 20.
[0056] Tibial component 24 is depicted in FIGS. 1-5, 8, 13, and 14.
As illustrated, e.g., in FIG. 2, tibial component 24 includes
tibial tray 98 connected to tibial stem 92. Stabilizing ribs 94
stabilize tibial tray 98 relative to tibial stem 92 and impede
rotation of tibial component 24 in tibia 118 see, e.g., FIG. 3). In
one exemplary embodiment, tibial component 24 is formed from a
cobalt-chromium alloy. Tibial component 24 further includes tibial
bushing 64 positioned within hinge post extension aperture 110.
Tibial bushing 64 is formed of plastic, such as, e.g., UHMWPE and
provides a bearing surface between hinge post extension 42 and
hinge post extension aperture 110 of tibial component 24. As
described above, meniscal component 26 comprises a rotating
bearing, and, thus, hinge post extension 42 will rotate relative to
tibial component 24. Tibial bushing 64 facilitates this rotation of
hinge post extension 42.
[0057] Tibial component 24 further includes rotation protrusion 96.
As illustrated, e.g., in FIG. 3, rotation protrusion 96 protrudes
upwardly from tibial tray 98 of tibial component 24 and further
extends in a plane substantially parallel to tibial tray 98.
Rotation protrusion 96 cooperates with cutout 90 of meniscal
component 26 to guide rotation of meniscal component 26 about hinge
post extension 42, as further described hereinbelow. FIGS. 31-36
illustrate an alternative embodiment tibial component 24b. As
illustrated, e.g., in FIG. 35, tibial component 24b includes a pair
of rotation protrusions, i.e., anterior rotation protrusion 180,
and posterior rotation protrusion 182. Rotation protrusions 180,
182 protrude upwardly from tibial tray 98b of tibial component 24b
and further extend in a plane substantially parallel to tibial tray
98b. Rotation protrusions 180, 182 cooperate with anterior cutout
160, and posterior cutout 162 of meniscal component 26b,
respectively (see, e.g., FIGS. 21-26) to guide rotation of meniscal
component 26b about the hinge post extension, as further described
hereinbelow.
[0058] One embodiment of meniscal component 26 is illustrated in
FIGS. 1-7, 13, and 14. Meniscal component 26 is formed from a
suitable plastic such as, e.g., UHMWPE and provides a rotating
bearing surface between femoral component 22 and tibial component
24. Meniscal component 26 includes bearing surfaces 86, 88 which
contact condylar bearing surfaces 28, 30 of femoral component 22
during movement of knee prosthesis 20. As described above, meniscal
component 26 further includes hinge post aperture 114 accommodating
passage of hinge post 40 and, consequently, hinge post extension 42
therethrough. Meniscal component 26 is operable to rotate about the
longitudinal axis of hinge post extension 42 to form a rotating
bearing.
[0059] Meniscal components of varying heights may be constructed in
accordance with the present invention. In one advantageous aspect
of the present invention, meniscal component 26 is packaged for
sale and use together with hinge post extension 42 to facilitate
component choice and, in one embodiment, to ensure proper extension
of hinge post extension 42 into tibial component 24. The extension
of hinge post extension 42 into tibial component 24 functions to
prevent separation of knee prosthesis 20 after implantation
thereof. As is known in the art, the femoral component of a knee
prosthesis may, in some situations, move relative to and away from
the tibial component in a direction parallel to the longitudinal
axis of the hinge post extension. With this in mind, hinge post
extension 42 is made to be of sufficient length to be retained
within tibial component 24 even in situations in which femoral
component 22 moves as described immediately supra. In one exemplary
embodiment, hinge post extension 42 extends four centimeters into
hinge post extension aperture 110 in tibial component 24.
[0060] Meniscal component 26 includes cutout 90 which cooperates
with rotation protrusion 96 of tibial component 24 to guide
rotation of meniscal component 26 and to resist lifting of meniscal
component 26 from tibial tray 98 of tibial component 24. As
illustrated, e.g., in FIG. 3, cutout 90 accommodates the portion
(i.e., lip) of rotation protrusion 96 extending in a plane
substantially parallel to the plane containing tibial tray 98, with
a portion (i.e., lip) of meniscal component 26 being positioned
between rotation protrusion 96 and tibial tray 98 in a direction
substantially perpendicular to the plane containing tibial tray 98.
This configuration functions to discourage displacement of meniscal
component 26 away from tibial tray 98 in a direction parallel to
the longitudinal axis of hinge post extension 42. Furthermore,
rotation protrusion 96 acts against the back of cutout 90 to limit
rotation of meniscal component 26 about the longitudinal axis of
hinge post extension 42.
[0061] Meniscal component 26b illustrated in FIGS. 21-26, includes
a pair of cutouts 160, 162 for cooperation with rotation
protrusions 180, 182 of tibial component 24b (see, e.g., FIGS.
31-36) to guide rotation of meniscal component 26b and to resist
lifting of meniscal component 26b from tibial tray 98b of tibial
component 24b. As illustrated, e.g., in FIG. 26, meniscal component
26b includes anterior cutout 160 as well as posterior cutout 162,
with anterior capture protrusion 170 and posterior capture
protrusion 172 respectively extending therefrom. As illustrated in
FIGS. 22 and 26, meniscal component 26b further includes channel
164 sized to accommodate posterior rotation protrusion 182 of
tibial component 24b as will be further described hereinbelow.
[0062] As illustrated in FIGS. 27-30, tibial component 24b includes
a pair of rotation protrusions, i.e., anterior rotation protrusion
180 and posterior rotation protrusion 182. As illustrated, e.g., in
FIG. 30, anterior cutout 160 and posterior cutout 162 in meniscal
component 26b respectively accommodate anterior capture protrusion
170 and posterior capture protrusion 172 formed in tibial component
26b. Specifically, cutouts 160, 162 accommodate the portion, i.e.,
lip of rotation protrusions 180, 182 extending in a plane
substantially parallel to the plane containing tibial tray 98b,
with a portion, i.e., lip of meniscal component 26b being
positioned between the portions of rotation protrusions 180, 182
extending in a plane substantially parallel to the plane containing
tibial tray 98, and tibial tray 98 when meniscal component 26b is
operably positioned atop tibial tray 98b as illustrated, e.g., in
FIG. 30. The cooperation of rotation protrusions 180, 182 with
capture protrusions 170, 172, as illustrated, e.g., in FIG. 30
functions to discourage displacement of meniscal component 26b away
from tibial tray 98b in a direction perpendicular to tibial tray
98b when the knee prosthesis of the current invention is operably
assembled as illustrated, e.g., in FIG. 1. Furthermore, cutouts
160, 162 are sized whereby rotation protrusions 180, 182 cooperate
therewith to limit rotation of meniscal component 26b about an axis
generally perpendicular to tibial tray 98b of tibial component 24b.
In one exemplary embodiment, meniscal component 26b is capable of a
total of sixty degrees of rotation from one extreme to the
other.
[0063] FIGS. 27-30 progressively illustrate movement of meniscal
component 26b relative to tibial component 24b to achieve proper
positioning of meniscal component 26b atop tibial tray 98b of
meniscal component 24b. As illustrated in FIG. 27, posterior
rotation protrusion 182 of tibial component 24b is positioned
within channel 164 formed in meniscal component 26b, with meniscal
component 26b resting atop rotation protrusion 180. Meniscal
component 26b is thereafter moved posteriorly as illustrated in
FIG. 28 until capture protrusions 170, 172 no longer rest atop
rotation protrusions 180, 182, and meniscal component 26b is moved
into contact with tibial tray 98b as illustrated in FIG. 29.
Meniscal component 26b is subsequently moved anteriorly so that
capture protrusions 170, 172 engage rotation protrusions 180, 182,
respectively, to prevent movement of meniscal component 26b in a
direction generally perpendicular to the plane containing tibial
tray 98b, as illustrated in FIG. 30. As illustrated in FIG. 27,
posterior rotation protrusion 82 includes bevel 184 to facilitate
posterior movement of meniscal component 26b. Once meniscal
component 26b is moved into the position illustrated in FIG. 30,
hinge post extension 42 may be operably positioned within the
tibial component as illustrated, e.g., in FIG. 4.
[0064] Positioning of meniscal component 26b as described above in
conjunction with FIGS. 27-30, may be effected in vivo with femoral
component 22 in place, i.e., implanted in femur 116 as illustrated
e.g., in FIG. 5. If meniscal component 26b is positioned with
femoral component 22 in place, the steps described above will occur
with condylar bearing surfaces 28-30 resting atop bearing surfaces
86b, 88d of meniscal component 26b, and with hinge post 40
positioned within hinge post aperture 114b of meniscal component
26b. As meniscal component 26b is moved relative to tibial
component 24b as illustrated in FIGS. 27-30, hinge post 40 will
rotate relative to femoral component 22 and move with meniscal
component 26b.
[0065] As illustrated in FIG. 5, meniscal component 26 may be slid
out from between tibial component 24 and femoral component 22 when
hinge post extension 42 has been removed from knee prosthesis 20.
As illustrated, hinge post aperture 114 is sized to allow rotation
of hinge post 40 so that meniscal component 26 may be slid out from
its position between femoral component 22 and tibial component 24.
Similarly, meniscal component 26b may be removed from position
between tibial component 24b and the femoral component when hinge
post extension 42 has been removed from knee prosthesis 20. If
meniscal component 26b and tibial component 24b are utilized,
meniscal component 26b is removed by reversing the steps utilized
to position meniscal component 26b atop tibial component 24b
described above in conjunction with FIGS. 27-30. This allows for
replacement of an implanted meniscal component 26 without requiring
removal of hinge post 40.
[0066] FIG. 5 illustrates removal of hinge post extension 42 to
accommodate replacement of meniscal component 26. As illustrated,
hinge plug wrench 102 engages hinge plug 38 for removal thereof.
After removal of hinge plug 38, slap hammer 104 is threadedly
engaged with threaded aperture 44 in hinge post extension 42. Slap
hammer 104 may then be utilized to unlock the engagement of locking
taper 46 in elongate hinge post extension aperture 112 so that
hinge post extension 42 may be removed. If hinge post extension 42b
illustrated in FIG. 2a is utilized, wrench 102 will be utilized to
rotate hinge post extension 42b to cause threaded proximal end 150
thereof to retreat from hinge plug threads 54 in hinge post 40,
thereby releasing engagement of locking taper 46b in elongate hinge
post extension aperture 112 and allowing for removal of hinge post
extension 42b.
[0067] FIGS. 13 and 14 illustrate a further alternative embodiment
of the knee prosthesis of the current invention. This alternative
embodiment utilizes hinge post extension 42a having locking taper
46a, cylindrical extension 48a, and flange 106. In this embodiment,
a locking instrument may be utilized to apply force atop hinge post
extension 42a so that locking taper 46a is seated in elongate hinge
post extension aperture 112 and locked therein. Flange 106 may be
utilized to facilitate removal of hinge post extension 42a. As
illustrated in FIG. 13, set screw 108 may be utilized as a
secondary lock for hinge post extension 42a.
[0068] FIGS. 15, 16 and 17 illustrate another alternative
embodiment of the hinge post extension and tibial bushing of the
present invention. In this embodiment, tibial component 24a
includes annular tibial bushing expansion groove 122 formed in
hinge post extension aperture 110. Tibial bushing 64a includes
retaining flange 130 positioned within annular tibial bushing
expansion groove 122. FIG. 15 illustrates insertion of cylindrical
extension 48b of the hinge post extension into tibial bushing 64a
positioned within tibial component 24a. As cylindrical extension
48b proceeds into tibial bushing 64a, bevel 126 contacts annular
locking protrusion 128 of tibial bushing 64a and causes outward
movement of retaining flange 130 as illustrated in FIG. 16 to allow
cylindrical extension 48b to proceed to its seated position as
illustrated in FIG. 17. Annular tibial bushing expansion groove 122
is sized to allow radial expansion of retaining flange 130 to
accommodate placement of cylindrical extension 48b within tibial
bushing 64a. In the fully seated position (FIG. 17) cylindrical
extension 48b is locked in place by the engagement of annular
locking protrusion 128 in annular locking groove 124. Furthermore,
retaining flange 130 cooperates with annular tibial bushing
expansion groove 122 to prohibit axial displacement of tibial
bushing 64a and, consequently, cylindrical extension 48b. In this
embodiment, the femoral component is retained in abutting
relationship to the meniscal component and lift off of the femoral
component is substantially prohibited. Tibial bushing 64a is, in
one exemplary embodiment, formed of UHMWPE.
[0069] FIGS. 18 and 19 illustrate yet another alternative
embodiment of the knee prosthesis of the current invention. In this
embodiment, locking clip 134 is utilized to retain the position of
hinge post 40b within hinge post aperture 114 of meniscal component
26a. Hinge post 40b is rotatably attached to femoral component 22
utilizing hinge pin 34 as described above. In this embodiment,
hinge post 40b includes locking clip grooves 132, and meniscal
component 26a includes locking clip apertures 136. Upon positioning
of hinge post 40b within hinge post aperture 114, locking clip 134
is positioned as illustrated in FIG. 19 with the prongs of locking
clip 134 being inserted into locking clip apertures 136 of meniscal
component 26a. As illustrated in FIG. 19, locking clip 134 engages
locking clip grooves 132 to retain hinge post 40b within hinge post
aperture 114 of meniscal component 26a. In this embodiment, lift
off of femoral component 22 is prohibited by the engagement of
hinge post 40b with meniscal component 26a. This embodiment of the
knee prosthesis of the current invention may further utilize a
meniscal component cutout together with a rotation protrusion on
the tibial component to resist lifting of the meniscal component
from the tibial tray as described above.
[0070] FIG. 20 illustrates a further alternative embodiment of the
hinge post of the present invention. Hinge post 40c illustrated in
FIG. 20 includes reinforcing material 138 to strengthen hinge post
40c.
[0071] While this invention has been described as a prosthetic knee
with a rotating bearing, it is contemplated that various aspects of
the present invention, including, e.g., the cannulated hinge post
will be utilized with a prosthetic knee having a fixed bearing.
[0072] While this invention has been described as having exemplary
designs, the present invention may be further modified within the
spirit and scope of this disclosure. This application is therefore
intended to cover any variations, uses, or adaptations of the
invention using its general principles. Further, this application
is intended to cover such departures from the present disclosure as
come within known or customary practice in the art to which this
invention pertains.
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