U.S. patent application number 09/897654 was filed with the patent office on 2003-11-06 for modular elbow.
Invention is credited to Block, D. Steven, Mutchler, Austin W., Wack, Michael A., Weiss, Arnold-Peter C..
Application Number | 20030208277 09/897654 |
Document ID | / |
Family ID | 25506798 |
Filed Date | 2003-11-06 |
United States Patent
Application |
20030208277 |
Kind Code |
A1 |
Weiss, Arnold-Peter C. ; et
al. |
November 6, 2003 |
Modular elbow
Abstract
A modular elbow prothesis includes a humeral component, an ulnar
component and three bearing components. The ulnar component
includes a stem for implantation in the intramedullary canal of an
ulna and a body including a slot. Two of the three bearing
components include flanges that mate with the slot of the ulnar
component. The humeral component includes a stem for implantation
in the intramedullary canal of the humerus and two arms extending
from one end of the stem. An opening is formed in each arm and in
two of the three bearing components. The modular elbow may be used
in an unconstrained mode by attaching one bearing component to the
ulnar component and the other to the humeral component by inserting
a pin through the openings in the arms and the bearing component.
The two bearing components are then placed adjacent each other such
that they articulate about their bearing surfaces. Alternatively,
the prosthesis can be utilized in a constrained mode by positioning
the flange of the third bearing component in the slot on the ulnar
component and positioning the third bearing component between the
arms of the humeral component and inserting a pin through the
openings in the arms of the third component. In one embodiment, two
of the bearing surfaces are configured to permit axial rotation
without becoming disengaged.
Inventors: |
Weiss, Arnold-Peter C.;
(Barrington, RI) ; Block, D. Steven; (Warsaw,
IN) ; Wack, Michael A.; (Warsaw, IN) ;
Mutchler, Austin W.; (Warsaw, IN) |
Correspondence
Address: |
Paul J. Maginot
Maginot, Addison & Moore
Bank One Center/Tower
111 Monument Circle, Suite 3000
Indianapolis
IN
46204-5130
US
|
Family ID: |
25506798 |
Appl. No.: |
09/897654 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09897654 |
Jun 29, 2001 |
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09222601 |
Dec 29, 1998 |
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6290725 |
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09222601 |
Dec 29, 1998 |
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08963138 |
Nov 3, 1997 |
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6027534 |
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Current U.S.
Class: |
623/20.12 ;
623/20.13 |
Current CPC
Class: |
A61F 2/3804 20130101;
A61F 2002/30535 20130101; A61F 2250/0058 20130101 |
Class at
Publication: |
623/20.12 ;
623/20.13 |
International
Class: |
A61F 002/38 |
Claims
What is claimed is:
1. A prosthetic elbow, including: an ulnar component having a stem
with a first end adapted to fit within the medullary canal of an
ulna and a second end; a first bearing component adapted to engage
the ulnar component; a humeral component having a stem with a first
end adapted to fit within the medullary canal of a humerus; and a
second bearing component having a spherical surface, the second
bearing component being adapted to engage the humeral component and
mate with the first bearing component so as to be held in place by
the soft tissues of the elbow, wherein said second bearing
component is releasably coupled to said humeral component.
2. A prosthetic elbow according to claim 1, wherein the spherical
surface of the second bearing component mates with the first
bearing component.
3. A prosthetic elbow according to claim 1, wherein the ulnar
component includes a slot and the first bearing component includes
a flange configured to mate with the slot.
4. A prosthetic elbow according to claim 1, wherein the first
bearing component includes a spherical surface.
5. A prosthetic elbow according to claim 4, wherein the spherical
surface of the first bearing component mates with the spherical
surface of the second bearing component.
6. A prosthetic elbow according to claim 1, wherein the ulnar
component further has a ridge configured to inhibit rotation of the
ulnar component relative to the ulna when the ulnar component is
located within the medullary canal of the ulna.
7. A prosthetic elbow according to claim 1, wherein the humeral
component further includes at least one ear configured to inhibit
rotation of the humeral component relative to the humerus when the
humeral component is located within the medullary canal of the
humerus.
8. A prosthetic elbow according to claim 1, wherein the first
bearing component further includes a nubbin which contacts at least
a portion of the ulnar component.
9. A prosthetic elbow according to claim 8, wherein the ulnar
component further includes an opening defined therein for engaging
the nubbin.
10. A prosthetic elbow according to claim 8, wherein the ulnar
component further includes a sloped notch defined therein for
guiding the nubbin during coupling of the first bearing component
to the ulnar component.
11. A prosthetic elbow, comprising: a humeral component; an ulnar
component; and a plurality of bearings for providing axial rotation
of the ulnar component relative to the humeral component, wherein
said plurality of bearings includes a first bearing component and a
second bearing component which contact each other, wherein said
first bearing component is releasably coupled to said ulnar
component, and wherein said second bearing component is releasably
coupled to said humeral component.
12. A prosthetic elbow according to claim 11, wherein at least one
of the bearings has a spherical bearing surface.
13. A prosthetic elbow according to claim 12, wherein the spherical
bearing surface mates with a bearing surface of another of the
plurality of bearings.
14. A prosthetic elbow according to claim 11, wherein at least two
of the bearings have a spherical surface.
15. A prosthetic elbow according to claim 14, wherein a spherical
bearing surface of one bearing mates with a spherical bearing
surface of another bearing.
16. A prosthetic elbow according to claim 11, wherein the bearings
provide at least two degrees of freedom.
17. A prosthetic elbow according to claim 11, wherein the bearings
provide at least three degrees of freedom.
18. An elbow prosthesis, comprising: an ulnar component; a humeral
component; and means for providing axial rotation of the ulnar
component with respect to the humeral component, wherein said axial
rotation providing means includes a first bearing component and a
second bearing component which contact each other, wherein said
first bearing component is releasably coupled to said ulnar
component, and wherein said second bearing component is releasably
coupled to said humeral component.
19. The elbow prosthesis according to claim 18, wherein the means
for providing axial rotation includes a bearing component having a
spherical bearing surface.
20. The elbow prosthesis according to claim 18, wherein the means
for providing axial rotation includes two spherical bearing
surfaces configured to mate with one another.
21. An elbow prosthesis, comprising: an ulnar component; a humeral
component; and means for providing at least three degrees of
freedom between the ulnar and humeral components, wherein said
three degrees of freedom providing means includes a first bearing
component and a second bearing component which contact each other,
wherein said first bearing component is releasably coupled to said
ulnar component, and wherein said second bearing component is
releasably coupled to said humeral component.
22. The elbow prosthesis according to claim 21, wherein the means
for providing at least three degrees of freedom includes a bearing
having a spherical surface.
23. The elbow prosthesis according to claim 21, wherein the means
for providing at least three degrees of freedom includes a first
bearing component having a spherical bearing surface and a second
bearing component having a spherical bearing surface configured to
mate with the spherical bearing surface of the first bearing
component.
Description
[0001] This application is a continuation of co-pending application
Ser. No. 09/222,601 filed on Dec. 29, 1998 which in turn is a
continuation-in-part of U.S. application Ser. No. 08/963,138 filed
Nov. 3, 1997.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] The present invention relates to artificial joints and, in
particular, to a modular elbow prosthesis.
[0003] In the human elbow, three degrees of freedom are present.
These are flexion-extension, varus-valgus (carrying angle) and
axial rotation. Various elbow prostheses have been constructed as a
replacement for the natural human elbow. The two basic types of
elbow prosthesis known in the prior art are constrained and
unconstrained. In constrained prosthesis, the prosthetic joint is
held together mechanically, by components of the prosthesis. Such
devices are shown, for example, in U.S. Pat. No. 5,376,121 to Huene
et al., U.S. Pat. No. 3,708,805 to Scales, et al., U.S. Pat. No.
3,939,496 to Ling, et al., and U.S. Pat. No. 4,224,695 to Grundei,
et al. In an unconstrained device, the prosthetic device is held
together by the patient's natural soft tissues. Such a device is
shown in U.S. Pat. No. 4,293,963 to Gold, et al. In each of these
devices, one portion of the prosthesis is implanted in the humerus
of the patient and the other portion is implanted in the ulna. The
two portions then mate in some manner to allow articulation of the
joint. In the '695 patent to Grundei, et al., an additional portion
of the prosthesis is implanted in the radius of the patient.
[0004] A surgeon may not always know prior to beginning an
operation whether a patient would be better served by a constrained
or unconstrained elbow prosthesis. Thus, it would be desirable to
provide an elbow prosthesis that may be utilized in either the
constrained or unconstrained manner.
[0005] It may also be necessary to convert an unconstrained elbow
prosthesis to a constrained one, or vice versa, after implantation
and use for a period of time. In order to do so, it is typically
necessary to remove the portion of the prosthesis implanted in the
humerus and ulna and to replace the entire prosthesis with either
the constrained or unconstrained variety.
[0006] The present invention provides an elbow prosthesis that can
be utilized in either a constrained or unconstrained fashion. The
elbow prosthesis of the present invention can be converted from a
constrained to an unconstrained prosthesis and from an
unconstrained to a constrained prosthesis after implantation in a
patient's body. Certain embodiments of the present invention also
provide an elbow prosthesis that allows for three degrees of
freedom: flexion-extension, varus-valgus (carrying angle) and axial
rotation.
[0007] These features are attained by the provision of a modular
prosthetic joint having a first stem, a second stem and three
bearing components. The first stem has a first end and a second end
and a body connected to it. A slot is formed in the body. The first
bearing component has a flange configured to mate with the slot. A
pair of arms extend from one end of the second stem. The second
bearing component is adapted to fit between the arms of the second
stem and configured to mate with the bearing surface of the first
bearing component. The third bearing component is interchangeable
with the first and second bearing components and is adapted to fit
between the arms of the second stem. The third bearing component
also includes a flange configured to mate with the slot.
[0008] According to one embodiment of the invention, the prosthesis
includes an opening in each of the arms, an opening in the second
bearing component and a pin adapted to extend through the openings
in the arms and second bearing component.
[0009] In another embodiment, the prosthesis includes an opening in
each of the arms, an opening in the third bearing component and a
pin adapted to extend through the openings in the arms and the
third bearing component.
[0010] In one embodiment of the invention, the bearing surface of
the first bearing component is concave and the second bearing
component includes a convex surface.
[0011] According to another embodiment of the invention, a modular
prosthetic elbow includes an ulnar component having a stem with a
first end adapted to fit within the medullary canal of a human ulna
and a second end, a humeral component having a stem with a first
end adapted to fit within the medullary canal of a human humerus, a
first bearing component adapted to engage the ulnar component, a
second bearing component adapted to engage the humeral component
and mate with the first bearing component so as to be held in place
by the soft tissues of the elbow, and a third bearing component
interchangeable with the first and second bearing components, the
third bearing component adapted to engage the ulnar component and
be held in place by the humeral component.
[0012] In one embodiment, the ulnar component includes a slot and
the first bearing component includes a flange configured to mate
with the slot. The humeral component includes a pair of arms and
the second bearing component is adapted to fit between the arms. An
opening is formed in each of the arms and in the second bearing
component and a pin is adapted to extend through the openings in
the arms and the second bearing component.
[0013] In one embodiment, the humeral component includes a pair of
arms and the third bearing component is adapted to fit between the
arms. An opening is formed in each of the arms and in the third
bearing component. A pin is adapted to extend through the openings
in the arms and the third bearing component.
[0014] In another embodiment, a slot is formed in the ulnar
component and a flange is connected to the third bearing component
and configured to engage the slot. In another embodiment, a slot is
formed in the ulnar component, a flange is connected to the first
bearing component and configured to engage the slot, and another
flange is formed on the third bearing component and configured to
engage the slot.
[0015] In another embodiment of the invention, a prosthetic modular
elbow includes an ulnar component having a proximal end and a
distal end and a humeral component having a proximal end and a
distal end. A first bearing mount is formed on the humeral
component for engagement with at least two of a plurality of
bearing components. A second bearing mount is located on the ulnar
component for engagement with at least two of a plurality of
bearing components. In one embodiment, the first bearing mount
includes a pair of spaced apart arms extending from the humeral
component. The arms may be located at the distal end of the humeral
component. In another embodiment of the invention, the second
bearing mount is located at the proximal end of the ulnar component
and may include a slot formed in a portion of the ulnar component.
In one embodiment of the invention, the first and second bearing
mounts are configured to simultaneously engage one of the plurality
of bearing components.
[0016] According to another embodiment of the present invention, a
modular elbow prosthesis includes a humeral component with a
bearing mount and an ulnar component with a bearing mount. First
and second bearing components are configured to engage the humeral
and ulnar bearing mounts respectively so as to form an
unconstrained prosthesis. A third bearing component,
interchangeable with the first and second bearing components, is
configured to engage the humeral and ulnar components so as to form
a constrained prosthetic elbow. The humeral bearing mount may
include a pair of spaced apart arms. The ulnar bearing mount may
include a slot. The third bearing component may include a
cylindrical body with an opening therein and may have a flange
attached thereto. The flange is configured to mate with the ulnar
bearing mount. The first bearing component may include a flange
configured to mate with the ulnar bearing mount. The second bearing
component may include an opening.
[0017] In another embodiment of the present invention, a modular
prosthetic elbow includes a humeral component, an ulnar component,
a first bearing for joining the humeral and ulnar components to
form a constrained prosthetic elbow and a set of bearings
interchangeable with the first bearing for providing pivotal
movement of the ulnar component relative to the humeral component
in an unconstrained manner.
[0018] A method according to the present invention includes the
steps of implanting a first component of a prosthesis in the ulna,
implanting a second component of the prosthesis in the humerus and
selecting from a group of three bearing components two bearing
components, one to be joined to the first component of the
prosthesis and a second to be joined to the second component of the
prosthesis, or selecting the remaining bearing component and
securing it to the first and second components of the
prosthesis.
[0019] In one embodiment, the method further comprises the step of
joining the first two bearing components to the first and second
components so as to form an unconstrained prosthetic elbow. In
another embodiment, the method further includes the step of joining
the third bearing component to the first and second component so as
to form a constrained prosthetic elbow.
[0020] In another embodiment of the invention, a prosthetic joint
includes a first stem having a first end and a second end, a body
connected to the first stem, a slot formed in the body, a first
bearing component having a spherical bearing surface, a flange
connected to the first bearing component and configured to mate
with the slot, a second stem having a first end and a second end, a
pair of arms extending from one end of the second stem and a second
bearing component adapted to fit between the arms of the second
stem and configured to mate with the bearing surface of the first
bearing component. The second bearing component may include a
spherical bearing surface. The prosthetic joint may include an
opening in each of the arms, an opening in the second bearing
component and a pin and sleeve adapted to extend through the
openings in the arms and second bearing component. A ridge may be
formed on a portion of the first stem and/or a portion of the body.
A recessed area may be provided in the second bearing component for
engaging at least one of the arms. An ear may be provided on the
second stem. A nubbin may be located on the first bearing component
and an opening may be provided in the body for engaging the
nubbin.
[0021] In another embodiment of the invention, a prosthetic elbow
includes an ulnar component having a stem with a first end adapted
to fit within the medullary canal of an ulna and a second end, a
first bearing component adapted to engage the ulnar component, a
humeral component having a stem with a first end adapted to fit
within the medullary canal of a humerus and a second bearing
component having a spherical surface, the second bearing component
being adapted to engage the humeral component and mate with the
first bearing component so as to be held in place by the soft
tissues of the elbow.
[0022] In another embodiment of the invention, an elbow prosthesis
includes a humeral component having a bearing mount, an ulnar
component having a bearing mount and first and second bearing
components, each including a spherical bearing surface, the first
bearing component configured to engage the ulnar bearing mount and
the second bearing component configured to engage the humeral
bearing mount.
[0023] In another embodiment of the invention, a prosthetic elbow
includes a humeral component, an ulnar component and a plurality of
bearings for providing axial rotation of the ulnar component
relative to the humeral component. At least one of the bearings may
include a spherical bearing surface. The prosthetic elbow may
provide a total of two or three degrees of freedom.
[0024] In another embodiment of the invention, an elbow prosthesis
includes an ulnar component, a humeral component and means for
providing axial rotation of the ulnar component with respect to the
humeral component. The means for providing axial rotation may
include a spherical bearing surface.
[0025] Another embodiment of the invention provides an elbow
prosthesis including an ulnar component, a humeral component and
means for providing at least three degrees of freedom between the
ulnar and humeral components.
[0026] Other features of the present invention will become apparent
from the following detailed description of the preferred
embodiments and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is an exploded perspective view of a modular elbow
according to the present invention for use in the unconstrained
configuration.
[0028] FIG. 2 is a longitudinal cross-sectional view showing the
modular elbow of FIG. 1 implanted in the arm of a person.
[0029] FIG. 3 is a cross-sectional view taken along line 3-3 in
FIG. 2.
[0030] FIG. 4 is an exploded perspective view of the modular elbow
according to the present invention for use in the constrained
mode.
[0031] FIG. 5 is a longitudinal cross-sectional view showing the
modular elbow of FIG. 4 implanted in the arm of a person.
[0032] FIG. 6 is a plan view of an alternative second bearing
component that forms a component of a modular elbow according to
the present invention.
[0033] FIG. 7 is a plan view of the bearing component of FIG. 6
attached to a humeral component that is a component of modular
elbow according to the present invention.
[0034] FIG. 8 is an exploded view of another embodiment of a
modular elbow according to the present invention for use in the
unconstrained configuration.
[0035] FIG. 9 is a partial cut-away, side elevational view of a
sleeve that forms a component of the modular elbow shown in FIG.
8.
[0036] FIG. 10 is a side elevational view of a pin that forms a
component of the modular elbow shown in FIG. 8.
[0037] FIG. 11 is a detail of the barb on the pin shown on FIG.
10.
[0038] FIG. 12 shows the modular elbow of FIG. 8 implanted in a
patient and illustrates one degree of freedom of motion permitted
by the elbow.
[0039] FIG. 13 is a partial cut-away view showing the modular elbow
of FIG. 8 in a neutral position.
[0040] FIG. 14 is a partial cut-away view illustrating a second
degree of freedom of motion permitted by the modular elbow of FIG.
8.
[0041] FIGS. 15-17 are partial cut-away views illustrating the
manner in which the modular elbow of FIG. 8 permits a third degree
of freedom of motion.
DETAILED DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 is an exploded perspective view of a modular elbow
according to the present invention for use in the unconstrained
mode. The modular elbow prothesis comprises ulnar component 10,
first bearing component 20, humeral component 30, second bearing
component 40, and pin 50.
[0043] Ulnar component 10 comprises a stem 11 having a first or
distal end 12 and a second or proximal end 13. A portion of stem 11
adjacent second end 13 may be coated with a material 14 to allow
bone ingrowth between the stem and ulna. Any of various known bone
ingrowth coatings, such as cobalt-chromium or titanium alloys, may
be used. A generally rectangular body 15 is secured to second end
13 and has a slot 16 formed therein. Body 15 and slot 16 form a
mount for a plurality of bearing components, as described below.
Stem 11 extends from body 15 at an angle thereto. A raised stop
member 17 is formed at the juncture of stem 11 and body 15. An
opening 18 is formed in body 15 and is configured to receive a
nubbin on first bearing component 20 or third bearing component 60,
as described below. Body 15 further includes a sloped, recessed
area or notch 18a utilized for guiding the nubbin into opening 18,
as described below. Ulnar component 10 can be made from any
surgical alloy, such as cobalt-chrome or titanium. Portions of
ulnar component 10 other than or in addition to stem 11 may include
a bone ingrowth coating. For example, bone ingrowth coating may be
applied to underside 19 of body 15.
[0044] First bearing component 20 generally comprises a base 21
with a stop member 22 extending therefrom at a generally ninety
degree angle. A flange 23 is formed on base 21 and is configured to
mate with slot 16 in body 15 of ulnar component 10, as described
below. A nubbin 23a extends from flange 23. Bearing component 20
further includes a concave bearing surface 24. Bearing surface 24
mates with second bearing component 40 as described below, when the
modular elbow prosthesis is used in the unconstrained mode.
[0045] Humeral component 30 includes a stem 31 having a first
segment 32 with a first or proximal end 33 and a second segment 34
with a second or distal end 35. Second segment 34 is integral with
first segment 32 and widens with distance from first end 33. A pair
of spaced apart arms 36 extend from second end 35 at an angle to
second segment 34 of stem 31. Each arm 36 includes an opening 37.
Arms 36 and openings 37 form a mount for a plurality of bearing
components, as described below. A locking ring 38 is disposed about
one opening 37. Humeral component 30 may also be made of a surgical
alloy, such as cobalt-chrome.
[0046] Second bearing component 40 is a generally cylindrical
member that flares outward at first end 41 and second end 42.
Middle segment 43 of second bearing component 40 has a convex outer
surface 44. The outer surface of second bearing component 40 mates
with bearing surface 24 of first bearing component 20 when the
modular elbow prosthesis is used in the unconstrained mode, as
described below. Second bearing component 40 also includes a
central opening or bore 45.
[0047] Pin 50 is a generally cylindrical member having a main body
portion 51, a first end 52 and a second end 53. First end 52
includes a slot 52a to engage with locking ring 38 and secure pin
50 in place. Second end 53 includes an enlarged head or flange 54.
Head 54 has a larger diameter than openings 37 in arms 36 of
humeral component 30. A central opening or bore 55 extends through
pin 50.
[0048] To use the elbow prosthesis of the present invention in the
unconstrained mode (FIGS. 2 and 3), ulnar component 10 is implanted
in an ulna such that stem 11 is located in the intramedullary canal
as shown in FIG. 2. In a similar fashion, humeral component 30 is
inserted in the humerus such that stem 31 is located in the
intramedullary canal as shown in FIG. 2. Ulnar component 10 and
humeral component 30 can be fixed to the ulna and humerus,
respectively, with or without bone cement. First bearing component
20 is positioned such that flange 23 is adjacent slot 16 in body 15
of ulnar component 10. First bearing component 20 is then slid
toward stop member 17. As this occurs, locking nubbin 23a engages
notch 18a. As first bearing component 20 is moved into further
engagement with ulnar component 10, locking nubbin 23a rides upward
along notch 18a and is compressed by it. When first bearing
component 20 is fully seated in ulnar component 10, locking nubbin
23a is located over opening 18a and decompresses. Locking nubbin
23a thus extends into opening 18a and prevents first bearing
component 20 from pulling back out of slot 16 in body 15. Second
bearing component 40 is positioned between arms 36 of humeral
component 30 such that opening 45 is aligned with opening 37. Pin
50 is then inserted through an opening 37 in one arm 36, through
opening 45 in second bearing component 40 and through the remaining
opening 37 in the other arm 36 such that locking ring 38 engages
slot 52a. Second bearing component 40 is then placed adjacent first
bearing component 20 such that their concave and convex surfaces
mate. First and second bearing components 20 are held in position
by the soft tissues of the elbow. In this manner, bearing
components 20 and 40 articulate about their bearing surfaces and
permit movement of the lower arm.
[0049] FIG. 4 shows an exploded perspective view of the components
of the modular elbow prosthesis of the present invention for use in
the constrained mode. In this mode, ulnar component 10, humeral
component 30 and pin 50 of the unconstrained configuration are
utilized in conjunction with a third bearing component 60. Third
bearing component 60 includes a generally cylindrical member 61
having a first end 62, a second end 63 and a bore or opening 64
extending therethrough. Cylindrical member 61 is connected to base
65. A flange 66 is connected to base 65 opposite cylindrical body
61. Flange 66 is configured to mate with slot 16 of body 15 in the
same way as previously described for first bearing component 20. A
locking nubbin 66a is formed on flange 66. First bearing component
20, second bearing component 40 and third bearing component 60 may
all be made from surgical metal or plastic, such as ultra-high
molecular weight polyethylene.
[0050] To implant the modular elbow of the present invention in the
constrained mode, ulnar component 10 is implanted in the ulna such
that stem 11 is located in the intramedullary canal as shown in
FIG. 5. Similarly, stem 31 of humeral component 30 is positioned in
the intramedullary canal of the humerus as shown. Third bearing
component 60 is then secured to body 15 of ulnar component 10 by
sliding flange 66 in groove 16 of body 15 until locking nubbin 66a
engages opening 18. Cylindrical body 61 of third bearing component
60 is then positioned between arms 36 of humeral component 30 such
that opening 64 is aligned with openings 37 in arms 36. Pin 50 is
then inserted through one opening 37 in an arm 36, through opening
64 in third bearing component 60 and through opening 37 in the
remaining arm 36 such that locking ring 38 engages slot 52a. In
this manner, third bearing component 60 can articulate about pin 50
between arms 36. Third bearing component 60 is held in place by pin
50 and arms 36, rather than the soft tissues of the elbow.
[0051] Thus, with the present invention, a modular prosthesis kit
is provided that allows for intra-operative implantation of a
constrained or unconstrained elbow prosthesis. Additionally, if it
is necessary to convert an unconstrained prosthesis to a
constrained configuration, with the present invention, the change
can be made after implantation and without removing the ulnar and
humeral components. To do so, the arm is surgically opened and pin
50 and second bearing component 40 are removed from arms 36 on the
humeral component. First bearing component 20 is removed from ulnar
component 10 by compressing locking nubbin 23a and sliding flange
23 out of slot 16. Third bearing component 60 is then secured to
ulnar component 10 by inserting flange 66 into slot 16. Cylindrical
body 61 is then positioned between arms 36 such that opening 64 is
aligned with openings 37 in arms 36. A pin 50 is then inserted
through the openings in arms 36 and third bearing component 60 and
locked in place with lock ring 38. In this manner, a surgeon is
provided with a modular elbow prosthesis kit that allows the
surgeon to decide, after surgery has begun, whether to utilize a
constrained or unconstrained prosthesis. Furthermore, the present
invention provides a prosthesis that can be converted from a
constrained to an unconstrained configuration, or vice versa,
without removing the ulnar and humeral components from the
patient.
[0052] FIGS. 6 and 7 show an alternative embodiment of the second
bearing component attached to humeral component 30. Second bearing
component 140 includes a generally cylindrical member having a
first and 141 and a second and 142. The middle segment 143 of
second bearing component 140 includes a convex outer surface 144.
The outer surface of second bearing component 140 mates with
bearing surface 24 of first bearing component 20 when the modular
elbow prosthesis is used in the unconstrained mode. Bearing
component 140 also includes a central opening or bore 145 extending
therethrough. Adjacent second end 142 is an enlarged body or head
146. A pair of slots or openings 147 are formed in bearing
component 140.
[0053] To secure bearing component 140 to humeral component 30,
arms 36 are inserted into slots 147 such that openings 37 therein
align with opening or bore 145 in bearing component 140. Openings
37 may be threaded to receive screws 150 to secure bearing
component 140 to humeral component 30. Alternatively, a pin and
locking ring arrangement, as described above, may be used.
Additional methods of securing bearing component 140 to humeral
component 30 may also be used.
[0054] FIG. 8 is an exploded perspective view of another embodiment
of a modular elbow according to the present invention for use in
the unconstrained mode. The modular elbow prothesis comprises ulnar
component 210, first bearing component 220, humeral component 230,
second bearing component 240, pin 250 and sleeve 260.
[0055] Ulnar component 210 comprises a stem 211 having a first or
distal end 212 and a second or proximal end 213. A portion of stem
211 adjacent second end 213 may be coated with a material 214 to
allow bone ingrowth between the stem and ulna. Any of various known
bone ingrowth coatings, such as cobalt-chromium or titanium alloys,
may be used. A generally rectangular body 215 is secured to second
end 213 and has a slot 216 formed therein. Body 215 and slot 216
form a mount for at least one bearing component, as described
below. Stem 211 extends from body 215 at an angle thereto. A raised
stop member 217 is formed at the juncture of stem 211 and body 215.
An opening 218 is formed in body 215 and is configured to receive a
nubbin on first bearing component 220, as described below. Body 215
further includes a sloped, recessed area or notch 218a utilized for
guiding the nubbin into opening 218, as described below. Ulnar
component 210 also includes a ridge 219a on underside 219 of body
215 and stem 211. Ridge 219a helps stabilize ulnar component 210 in
the intermedullary canal of the ulna by preventing rotation. Ulnar
component 210 can be made from any surgical alloy, such as
cobalt-chrome or titanium. Portions of ulnar component 210 other
than or in addition to stem 211 may include a bone ingrowth
coating. For example, bone ingrowth coating may be applied to
underside 219 of body 215.
[0056] First bearing component 220 generally comprises a base 221
with a stop member 222 extending therefrom at a generally ninety
degree angle. A flange 223 is formed on base 221 and is configured
to mate with slot 216 in body 215 of ulnar component 210, as
described below. A nubbin 223a extends from flange 223. Bearing
component 220 further includes a concave, spherical bearing surface
224. Bearing surface 224 mates with second bearing component 240 as
described below, when the modular elbow prosthesis is used in the
unconstrained mode.
[0057] Humeral component 230 includes a stem 231 having a first
segment 232 with a first or proximal end 233 and a second segment
234 with a second or distal end 235. Second segment 234 is integral
with first segment 232 and widens with distance from first end 233.
A pair of ears 235a is provided adjacent distal end 235 of humeral
component 230. Ears 235a help to stabilize humeral component 230 in
the intermedullary canal of the humerus by preventing rotation. A
pair of spaced apart arms 236 extend from second end 235 at an
angle to second segment 234 of stem 231. Each arm 236 includes an
opening 237. Note that in the embodiment shown, arms 236 are keyed
about openings 237 by providing a recessed area 237a. Arms 236 and
openings 237 form a mount for at least one bearing component, as
described below. Humeral component 230 may also be made of a
surgical alloy, such as cobalt-chrome.
[0058] Second bearing component 240 includes a first end 241, a
second end 242 and a middle segment 243. Ends 241 and 242 are keyed
with recessed areas 241a and 242a generally corresponding in shape
to arms 236. This prevents second bearing component 240 from
rotating with respect to arms 236. Middle segment 243 of second
bearing component 240 has a convex, spherical bearing surface 244.
Bearing surface 244 of second bearing component 240 mates with
bearing surface 224 of first bearing component 220 when the modular
elbow prosthesis is used in the unconstrained mode, as described
below. Second bearing component 240 also includes a central opening
or bore 245.
[0059] Pin 250 is a generally cylindrical member having a main body
portion 251, a first end 252 and a second end. Second end 253
includes an enlarged head or flange 254. Head 254 has a larger
diameter than openings 237 in arms 236 of humeral component 230 and
is shaped to generally correspond to the shape of areas 237a. A
barb 255 is located on body portion 251. Barb 255 includes a first,
angled segment 255a, a second segment 255b generally parallel to
body portion 251, a third, angled segment 255c and a fourth, angled
segment 255d. Barb 255 secures pin 250 to sleeve 260 as described
below. Pin 250 is preferably made from a metal material. However,
other materials can also be utilized.
[0060] Sleeve 260 is a generally cylindrical member having a bore
261, an interior wall 262, an exterior wall 263, an enlarged head
264 and an edge 265. Head 264 has a larger diameter than openings
237 in arms 236 of humeral component 230 and is shaped to generally
correspond to the shape of areas 237a. Bore 261 is roughly the
diameter of body portion 251 and is smaller in diameter than second
segment 255b. Sleeve 260 is preferably made from ultra high
molecular weight polyethylene. However, other materials can also be
utilized.
[0061] To use the elbow prosthesis of the present invention in the
unconstrained mode, ulnar component 210 is implanted in an ulna
such that stem 211 is located in the intramedullary canal. In a
similar fashion, humeral component 230 is inserted in the humerus
such that stem 231 is located in the intramedullary canal. Ulnar
component 210 and humeral component 230 can be fixed to the ulna
and humerus, respectively, with or without bone cement. First
bearing component 220 is positioned such that flange 223 is
adjacent slot 216 in body 215 of ulnar component 210. First bearing
component 220 is then slid toward stop member 217. As this occurs,
locking nubbin 223a engages notch 218a. As first bearing component
220 is moved into further engagement with ulnar component 210,
locking nubbin 223a rides upward along notch 218a and is compressed
by it. When first bearing component 220 is fully seated in ulnar
component 210, locking nubbin 223a is located over opening 218a and
decompresses. Locking nubbin 223a thus extends into opening 218a
and prevents first bearing component 220 from pulling back out of
slot 216 in body 215. Second bearing component 240 is positioned
between arms 236 of humeral component 230 such that opening 245 is
aligned with opening 237 and arms 236 extend into recessed areas
241a and 242a.
[0062] Sleeve 260 is then inserted through an opening 237 in one
arm 236, through opening 245 in second bearing component 240 until
head 264 is located in recessed area 237a. Pin 250 is then inserted
through opening 237 in the other arm 236 and into bore 261 of
sleeve until head 254 is located in recessed area 237a. As pin 250
is inserted into bore 261, edge 265 rides along first segment 255a
and expands or deforms bore 261 so that barb 255 can be fully
located within bore 261. If an attempt is made to remove pin 250
from sleeve 260, barb 250 will cut into or otherwise engage
interior wall 262, thereby resisting removal.
[0063] Second bearing component 240 is then placed adjacent first
bearing component 220 such that their concave and convex surfaces
mate. First and second bearing components 220 are held in position
by the soft tissues of the elbow. In this manner, bearing
components 220 and 240 articulate about their bearing surfaces and
permit movement of the lower arm.
[0064] As shown in FIG. 12, bearing components 220 and 240
articulate to permit movement similar to the flexion-extension
type, thus providing a first degree of freedom of motion.
[0065] As shown in FIGS. 13 and 14, this embodiment of the
invention also permits lateral movement between the bearing
components. FIG. 13 shows the elbow in a neutral position, i.e.,
bearing component 220 is centered with respect to bearing component
240. FIG. 14 illustrates the relative position of bearings 220 and
240 when the prosthesis moves as indicated by the arrows in FIG.
14. As can be seen, bearing components 220 and 240 shift with
respect to one another while still maintaining contact. Thus, the
prosthesis presents a second degree of freedom of motion.
[0066] Additionally, bearing components 220 and 240 permit axial
rotation, as shown in FIGS. 15 through 17, thereby providing a
third degree of freedom of motion. FIG. 15 shows the relative
position of bearing components 220 and 240 in the neutral position.
FIGS. 16 and 17 indicate that as the joint is subject to axial
rotation, as indicated by the arrows, the bearing components 220
and 240 shift as indicated. However, because bearing surfaces 224
and 244 are spherical, they maintain contact even during axial
rotation.
[0067] As with the embodiment of FIGS. 1-5, the embodiment of FIG.
8 could also be converted for use in the constrained mode. To do
so, bearing components 220 and 240 would be removed and replaced
with a bearing component similar to third bearing component 60.
[0068] Although the present invention has been shown and described
in detail the same is to be taken by way of example only and not by
way of limitation. Numerous changes can be made to the embodiments
shown without departing from the scope of the invention. For
example, the shapes of the various component can be changed, so
long as the principals of the operation are maintained. Also,
either the pin and locking ring arrangement of FIG. 1 or the pin
and sleeve arrangement of FIG. 8 can be used with either set of
ulnar and humeral components and bearings. Accordingly, the
invention is to be limited only by the terms of the claims appended
hereto.
* * * * *