U.S. patent number RE28,895 [Application Number 05/579,006] was granted by the patent office on 1976-07-13 for artificial hip joint.
This patent grant is currently assigned to United States Surgical Corporation. Invention is credited to Douglas G. Noiles.
United States Patent |
RE28,895 |
Noiles |
July 13, 1976 |
Artificial hip joint
Abstract
An artificial hip joint having an acetabulum prosthesis for the
cotyloid cavity defining a socket and including a head having a
plurality of blades extending outwardly away from the socket for
engaging the prepared wall of the cotyloid cavity and having at
least one insert removably connected to the head to form the
socket. A prosthesis of the head of the femur is movably
interconnected with the acetabulum prosthesis and includes a pin to
be driven into the bone-marrow channel of the femur, a curved neck
integral with the pin, and a hip ball positioned on the neck,
movably located within the socket and in movable contact with the
removable insert. Means are provided in operative relationship with
the femur head prosthesis for preventing rotation of the femur head
prosthesis with respect to the femur.
Inventors: |
Noiles; Douglas G. (New Canaan,
CT) |
Assignee: |
United States Surgical
Corporation (Baltimore, MD)
|
Family
ID: |
26912033 |
Appl.
No.: |
05/579,006 |
Filed: |
May 19, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
217540 |
Jan 13, 1972 |
03848272 |
Nov 19, 1974 |
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Current U.S.
Class: |
623/22.31 |
Current CPC
Class: |
A61F
2/30728 (20130101); A61F 2/30739 (20130101); A61F
2/32 (20130101); A61F 2002/3401 (20130101); A61F
2002/3241 (20130101); A61F 2002/30975 (20130101); A61F
2/367 (20130101); A61F 2002/30495 (20130101); A61F
2002/3233 (20130101) |
Current International
Class: |
A61F
2/32 (20060101); A61F 2/30 (20060101); A61F
2/34 (20060101); A61F 2/36 (20060101); A61F
001/24 () |
Field of
Search: |
;3/1,1.9-1.913
;128/92C,92CA,92R,92BA,92BB,92BC,92F,92G ;403/131,140,141,143 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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109,415 |
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Dec 1939 |
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AU |
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1,047,640 |
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Jul 1953 |
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FR |
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163,476 |
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Jun 1958 |
|
SW |
|
162,762 |
|
Apr 1958 |
|
SW |
|
459,462 |
|
Sep 1968 |
|
CH |
|
1,215,737 |
|
Dec 1970 |
|
UK |
|
Other References
"Factors in the Design of an Artificial Hip Joint," by J. Charnley,
The Institute of Mechanical Engineers, Proceedings, 1966-1967, vol.
181, Part 3J, pp. 108-111 relied upon. .
"A Femoral-Head Prosthesis for the Hip Joint," by E. D. McBride,
The Journal of Bone & Joint Surgery, vol. 32-A, No. 4, Oct.
1952, pp. 989-995..
|
Primary Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Fleit & Jacobson
Claims
What is claimed is:
1. An artificial hip joint, comprising:
an acetabulum prosthesis of the cotyloid cavity defining an
aperture having screw threads on the inner surface thereof and a
plurality of blades extending outwardly away from said aperture for
engaging the prepared wall of the cotyloid cavity;
at least one insert having an outer threaded surface and an inner
bearing surface inserted into said aperture and threadedly
connected by means of said threads to said acetabulum prosthesis to
form a socket, the outer surface of said at least one insert
engaging and being supported by the inner surface of said aperture;
and
a prosthesis of the head of the femur movably interconnected with
said acetabulum prosthesis and including a pin to be driven into
the bone-marrow channel of the femur, a .[.curved.]. neck integral
with the pin, and a hip ball positioned on the neck, movably
located within said socket and in movable contact with said insert,
said socket enveloping more than one-half of the hip ball to
prevent withdrawal of the hip ball from the socket, said artificial
hip joint composed of surgical grade materials suitable for
implantation into the body.
2. An artificial hip joint as in claim 1 wherein said insert is
comprised of plastic.
3. An artificial hip joint as in claim 1 wherein said acetabulum
prosthesis includes two of said inserts.
4. An artificial hip joint as in claim 1 wherein said insert is
comprised of ultra high molecular weight polyethylene.
5. An artificial hip joint as in claim 4 wherein said hip ball is
comprised of titanium or a titanium alloy.
6. An artificial hip joint as in claim 1 wherein said insert is
comprised of cobalt alloy ASTM F75-67.
7. An artificial hip joint as in claim 1 wherein said hip ball is
comprised of cobalt alloy.
8. An artificial hip joint as in claim 1 wherein all of said
acetabulum prosthesis but the insert and all of the prosthesis of
the head of the femur but the hip ball are comprised of titanium or
a titanium alloy.
9. An artificial hip joint as in claim 8 wherein the titanium alloy
is ASTM F136-70.
10. An artificial hip joint as in claim 8 wherein the titanium is
ASTM F67-66.
11. An artificial hip joint as in claim 1 wherein said insert
includes an integral threaded ring portion for threadedly engaging
grooves in said acetabulum prosthesis.
12. An artificial hip joint as in claim 11 wherein said insert
further defines notches adjacent said threaded ring for enabling
said insert to be screwed into position with said ring threadedly
engaging said grooves.
13. An artificial hip joint as in claim 1 wherein said insert is
formed as one unitary piece.
14. An artificial hip joint comprising:
an acetabulum prosthesis of the cotyloid cavity defining an
aperture having screw threads on the inner surface thereof;
at least one insert having an outer threaded surface and an inner
bearing surface inserted into said aperture and threadedly
connected by means of said threads to said acetabulum prosthesis to
form a socket, the outer surface of said at least one inert
engaging and being supported by the inner surface of said aperture;
and
a prosthesis of the head of the femur movably interconnected with
said acetabulum prosthesis and including a pin to be driven into
the bone-marrow channel of the femur, a .[.curved.]. neck integral
with the pin, and a hip ball positioned on the neck, movably
located within said socket and in movable contact with said insert,
said socket enveloping more than one-half of the hip ball to
prevent withdrawal of the hip ball from the socket, said artificial
hip joint composed of surgical grade materials suitable for
implantation into the body.
15. An artificial hip joint as in claim 14 wherein said insert
includes an integral threaded ring portion for threadedly engaging
said acetabulum prosthesis threads.
16. An artificial hip joint as in claim 15 wherein said insert
further defines notches adjacent to said threaded ring for enabling
said insert to be screwed into position with said ring threadedly
engaging said threads.
17. An artificial hip joint as in claim 14 wherein said insert
socket defines more than a hemisphere.
18. An artificial hip joint as in claim 14 wherein said insert is
formed as one unitary piece.
19. An artificial hip joint as in claim 18 wherein said insert is
comprised of plastic.
20. An artificial hip joint as in claim 19 wherein said plastic is
ultra high molecular weight polyethylene.
21. An artificial hip joint as in claim 14 wherein said insert is
formed as two pieces.
22. An artificial hip joint as in claim 21 wherein said insert is
comprised of cobalt alloy.
23. An artificial hip joint as in claim 22 wherein said cobalt
alloy is ASTM F75-67.
24. An artificial hip joint as in claim 14 further including means
in operative relationship with said femur head prosthesis for
preventing rotation of the femur head prosthesis with respect to
the femur.
Description
The present invention relates to artificial joints and more
particularly to an artificial hip joint.
Numerous types of artificial hip joints have been developed and
used. One successful example of such an artificial hip joint is
that described in U.S. Pat. application Ser. No. 189,261 filed Oct.
14, 1971, .Iadd.now U.S. Pat. No. 3,820,167 .Iaddend.as a
continuation-in-part of U.S. Pat. application Ser. No. 737,910,
filed June 18, 1968, now abandoned.
Previously used hip joint prostheses have been made with various
types of materials in attempts to provide both a strong joint and
one that will not be unduly corroded by the body environment.
Various styles and arrangements of hip joints having an artificial
acetabulum articulately connected to an artificial caput femoris
have been developed; however, use of some of these joints has made
evident inherent disadvantages due to the shapes of the hips and
because of the materials used. Frequently, bone growth stimulated
as a result of mechanical irritation by the artificial joints has
resulted in partial immobilization of the joints with a concomitant
gradual increase of painful sensations.
Experience has also shown that it may often be desirable, due to
wear or malfunction of the artificial hip joint, to replace the
bearing surfaces of the joint after some period of use by the
patient. In the past, however, it has not been possible to remove
and replace the bearing surfaces from the implanted hip and the
patient has thus been required to endure use of a poorly
functioning artificial hip or has been required to undergo the
procedures necessary for the complete replacement of the entire
artificial hip joint.
Accordingly, it is an object of the present invention to provide an
artificial hip joint that will have all of the functions inherent
in a normal human hip joint and which possesses great strength and
long service life.
Another object is to provide an artificial hip joint that is light
in weight.
A further object of the invention is the provision of an artificial
hip joint, portions of which can be replaced even after
implantation in the patient.
Still another object of the present invention is the provision of
an artificial hip joint that is relatively simple and inexpensive
to manufacture and which is relatively easy to insert into the
body.
Another object is to provide an artificial hip joint that is
provided with means for preventing rotation of the femur head
prosthesis with respect to the femur.
Additional objects and advantages of the invention will be set
forth in part in the description which follows and in part will be
obvious from the description, or may be learned by practice of the
invention. The objectives and advantages are realized and attained
by the instrumentalities and combinations particularly pointed out
in the appended claims.
To achieve these and other objects, the present invention provides
an artificial hip joint having an acetabulum prosthesis of the
cotyloid cavity defining a socket and including a head, a plurality
of blades extending outwardly away from the socket for engaging the
prepared wall of the cotyloid cavity and further including at least
one insert removably connected to the head to form the socket. A
prosthesis of the head of the femur is movably interconnected with
the acetabulum prosthesis and includes a pin to be driven into the
bone-marrow channel of the femur, a curved neck integral with the
pin and a hip ball positioned on the neck, movably located within
the socket and in movable contact with the insert.
As here embodied, the acetabulum prosthesis head has a channel
therein and the insert has a groove therein the groove and the
channel being positioned in communicating relationship with respect
to one another when the insert is positioned in connecting
relationship with the acetabulum prosthesis head. In addition, a
flexible ring member is positioned within the groove and within the
channel to retain the insert in position within the acetabulum
prosthesis head.
The acetabulum prosthesis head preferably has an entry slot therein
in communication with the channel and the insert preferably has an
entry passage therein in communication with the groove for enabling
the ring to be inserted through the entry slot, and the entry
passage and into the insert groove and the acetabulum prosthesis
channel.
In a preferred embodiment, the insert further defines an extension
well in communication with the entry passage for facilitating
insertion and removal of the flexible ring. As here embodied, the
artificial hip joint also preferably includes means in operative
relationship with the femur head prosthesis for preventing rotation
of the femur head prosthesis with respect to the femur.
It is to be understood, of course, that both the foregoing general
description and the following detailed description are explanatory
only and are not restrictive of the invention.
The accompanying drawings, which are incorporated in and constitute
part of the specification, illustrate the invention and together
with the description, serve to explain the principles of the
invention.
FIG. 1 is an elevation view, partly in section of one embodiment of
the artificial hip joint of this invention;
FIG. 2 is a view taken on the line 2--2 of FIG. 1 and looking in
the direction of the arrows;
FIG. 3 is a view taken on the line 3--3 of FIG. 2 and looking in
the direction of the arrows;
FIG. 4 is an exploded perspective view of one embodiment of the
acetabulum prosthesis head inserts and of the flexible ring member
used to hold the inserts in place;
FIG. 5 is a fragmentary sectional view of another embodiment of the
invention for holding the inserts in position;
FIG. 6 is a fragmentary sectional view of still another embodiment
of the invention for holding the inserts in position;
FIG. 7 is a fragmentary perspective view of one anti-rotation
embodiment of the invention;
FIG. 8 is a fragmentary perspective view of another anti-rotation
embodiment;
FIG. 9 is a sectional view taken on the line 9--9 of FIG. 8 and
looking in the direction of the arrows;
FIG. 10 is a fragmentary view of another anti-rotational embodiment
of the invention;
FIG. 11 is a fragmentary view of still another anti-rotation
embodiment;
FIG. 12 is a fragmentary view, partly in section, of an alternative
anti-rotation embodiment for preventing rotation of the femur head
prosthesis with respect to the femur;
FIG. 13 is a perspective view of a collar for use with the
embodiment illustrated in FIG. 12;
FIG. 14 is a fragmentary view, partly in section, of still another
anti-rotation embodiment;
FIG. 15 is a fragmentary view, partly in section, of a further
anti-rotation feature of the invention;
FIG. 16 is a fragmentary view of an additional anti-rotation
embodiment;
FIG. 17 illustrates a further embodiment of the invention;
FIG. 18 is a fragmentary exploded perspective view of an embodiment
of the invention for preventing rotation of the inserts within the
acetabulum prosthesis;
FIG. 19 is a fragmentary view of a feature of the invention
providing for removal of the hip ball;
FIG. 20 is a fragmentary view of another embodiment permitting
removal of the hip ball;
FIG. 21 is a fragmentary perspective view of an additional
embodiment of the invention; and
FIG. 22 is a fragmentary perspective view of a further embodiment
of the invention.
With reference now to the drawings, wherein like reference
characters designate like or corresponding parts throughout the
several views, there is shown a machined acetabulum prosthesis 10
of the cotyloid cavity defining a socket 12 and including a head
13. A plurality of blades 14, 16, 18 and 20 extend outwardly away
from the socket for engaging the prepared wall (not shown) of the
cotyloid cavity.
A machined prosthesis 22 of the head of the femur is movably
interconnected with the acetabulum prosthesis 10 and includes a pin
24 to be driven into the bone-marrow channel of the femur (not
shown), a curved neck 26 integral with pin 24, and a hip ball 28
positioned on the neck and movably located within socket 12.
As here embodied, acetabulum prosthesis 10 includes at least one
but preferably two inserts 30 removably connected to head 13 to
form socket 12. The total area of the inserts forming the socket
and bearing against hip ball 28 is more than one-half the spherical
surface of the hip ball in order to retain the hip ball in position
in the socket and to prevent the possibility of postoperative
dislocation. The acetabulum prosthesis also has a plurality of
blades 14, 16, 18 and 20 with notches and holes therein as
described in pending U.S. Pat. application Ser. No. 189,261 filed
Oct. 14, 1971.
The insert or plurality of inserts 30 are connected to head 13, and
may be connected in a removable or in a permanent condition as will
be explained more fully later in this specification.
Prosthesis 22 of the head of the femur, in addition to pin 24 and
neck 26, also preferably includes an enlarged shoulder 60 integral
with and positioned between the pin and the neck, and the neck is
preferably formed with a base 62 joined to the shoulder and
eccentrically positioned with respect to the central axis 64 of the
pin. Shoulder 60 defines a side portion 66 and a lower surface 68,
and it is surface 68 that rests on the upper portion of the severed
femur when the artificial hip joint is installed. In a preferred
construction of the artificial hip joint, an innermost portion 70
of the neck also extends in a continuous manner from side portion
66 of the shoulder.
It is also preferable and the preferred embodiment illustrated
provides for a curvature of neck 26 so as to form an angle of
substantially 120.degree. with pin axis 64. The angle is measured
between the pin axis and an imaginary line passing from the pin
axis through the center of hip ball 28 and tangentially to the
innermost curved surface 70 of the neck.
Pin 24 also defines two slots 72 and 74 opening in directions
parallel to the direction of curvature of neck 26. The function of
these slots is similar to the function of the holes in prosthesis
10, and slots 72 and 74 permit bone tissue to row therethrough so
as to fix pin 24 and prosthesis 22 within the femur. Pin 24 is also
tapered away from neck 26, and the neck is tapered away from the
pin. The taper of the pin permits it to be driven downwardly and
into the bone-marrow channel of the femur.
In an alternative arrangement and use of the artificial hip joint
of this invention, shoulder 60 is provided with a hole 76 entering
the side portion 66 of the shoulder. A rod 78 is also provided, and
it is adapted to pass through a hole drilled in the greater
trochanter (not shown) and to be driven into hole 76 to hold the
greater trochanter in proper position after the artificial joint
has been installed.
In another embodiment and use of the hip joint, a collar 80 is
provided for insertion into the upper part of the femur and for
providing additional support for the artificial hip on the femur
when necessary. The collar is provided with a flange portion 82 for
engaging the lower surface 68 of shoulder 60, and the collar is
also provided with a sleeve portion 84 integral with flange portion
82 for sliding over pin 24 so that the collar can be positioned on
the upper part of the severed femur. Pin 24 can, thus, be inserted
through the collar and into the bone-marrow channel of the femur to
cause shoulder 60 to rest on flange portion 82.
It is also preferable that sleeve portion 84 of the collar be
provided with a plurality of holes 86 for enabling bone tissue to
grow through the holes and to assist in holding the collar in its
proper position on the femur.
As previously mentioned, inserts 30 are preferably removably
connected to head 13. This is particularly desirable since it
readily facilitates replacement of the inserts if they become worn
or otherwise damaged after a period of use in the body of the
patient.
In a preferred embodiment, acetabulum prosthesis head 13 has a
channel 88 therein and the insert or inserts 30 has a groove or
grooves 90 therein. The channel and the grooves are so positioned
with regard to the dimensions of head 13 and inserts 30 that when
groove 90 and channel 88 are positioned in communicating
relationship with respect to one another the inserts are tightly
positioned and engage the inner portion of head 13. A flexible ring
member 92 is normally positioned within groove 90 and within
channel 88 to retain the insert or inserts 30 in position with
acetabulum prosthesis head 13.
In order to facilitate insertion and removal of flexible ring 92,
acetabulum prosthesis head 13 is provided with an entry slot 94
located in communication with channel 88 and at least one insert 30
is provided with an entry passage 96 in communication with groove
90. Both entry slot 94 and entry passage 96 are readily accessible
for enabling the ring to be inserted into the groove and the
channel or to facilitate removal of the ring when removal of
inserts 30 is desired.
Entry slot 94 and entry passage 96 are preferably formed to each
subtend an angle of substantially 25.degree., wherein the vertex of
the angle is located at the center of hip ball 28. This provides
the necessary space for enabling easy insertion and removal of ring
member 92. In addition, channel 88 and groove 90 are dimensioned
such that ring member 92, when in its inserted position, bears
primarily against a lower surface 98 of channel 88 and against an
upper surface 100 of groove 90 so as to force inserts 30 into
tight-fitting contact with acetabulum prosthesis head 13 along
adjoining surfaces 102 and 104, for example.
Flexible ring 92 is preferably non-continuous and may be provided
with an enlarged end and an aperture 106 at one or both ends to
facilitate grasping of the ring by a tool (not shown) and to
prevent rotation of the ring within the channel and the groove so
that the aperture 106 is always accessible. In order to further
facilitate grasping of the ring member for insertion and removal
thereof, insert 30 preferably defines an extension well 108 in
communication with entry passage 96 and with groove 90. This well
enables a tool to be inserted through ring aperture 106 and permits
the tool to extend into extension well 108 during the removal or
insertion procedure.
Although not illustrated, an entry slot and an entry passage
similar and in addition to slot 94 and to passage 96 can be
provided in head 13 and in inserts 30, respectively, and located at
a different location from slot 94 and passage 96. In this
embodiment, two rings are provided instead of one and each ring
extends substantially half way around channel 88 and groove 90.
Each ring can then be inserted and removed via its respective entry
passage and entry slot.
The artificial hip joint of the present invention is preferably
constituted of surgical grade materials suitable for implantation
into the body.
It is desirable to use titanium or a titanium alloy for the greater
portion of the artificial hip joint because this has proven to be
highly effective in providing the desired strength while also
providing for the desired resistance to corrosion. It may be
desirable to use a cobalt alloy for the hip ball 28 and for inserts
30. However, it may also be desirable for economic and other
reasons to use a plastic material for inserts 30, such as an ultra
high molecular weight polyethylene. The use of such a plastic
material for the inserts may permit the use of titanium or a
titanium alloy for the hip ball, and the artificial hip joint can
be made lighter in weight as a result.
In one embodiment, for example, the entire artificial hip joint
with the exception of inserts 30 may be comprised of titanium or a
titanium alloy and the titanium may be, for example, ASTM F67-66
and the titanium alloy may be, for example, ASTM F 136-70, where
collar 80 and rod 78 are utilized, these elements may also be
comprised of the same titanium or titanium alloy that is used in
the remaining portions of the joint. Similarly, flexible ring
member or members 92 may also be made of the same titanium or
titanium alloy that is used in the remaining portions of the
joint.
Another embodiment of the invention, however, utilizes the same
titanium or titanium alloy for all portions of the joint with the
exception of hip ball 28 and inserts 30. In this embodiment, the
hip ball and inserts may each be comprised of cobalt alloy ASTM
F75-67, as an example.
In another embodiment of the invention wherein the inserts are
permanently positioned within acetabulum prosthesis head 13, (FIG.
5) head 13 is provided with channel 88 and inserts 30 are provided
with grooves 90. When assembled, channel 88 and grooves 90 are
positioned in communication with each other and a ring member 92,
which need not have an aperture therein, is positioned within the
channel and within the grooves for retaining inserts 30 in position
within acetabulum prothesis head 13. The ring is preferably
flexible so as to spring into channel 88 from groove 90 when
inserts 30 are properly positioned within the head 13. Conversely,
the ring may be initially expanded (FIG. 6) within channel 88 so as
to spring into grooves 90 when the channel and the grooves are
positioned in communication with one another.
When using an artificial hip joint, it is extremely important that
the artificial joint be rigidly held with respect to the femur so
that it does not rotate relative to the femur. In order to firmly
fix the artificial hip joint with respect to the femur, the present
invention provides means in operative relationship with the femur
head prosthesis for preventing rotation of the femur head
prosthesis with respect to the femur.
As here embodied, and as illustrated in FIG. 7, the rotation,
preventing means includes a fin member 110 integral with and
extending from pin 24 for engaging a slot (not shown) cut into the
femur by the surgeon. Fin 110 preferably extends only along a small
portion of pin 24 and the fin is positioned within the slot to
prevent rotation of pin 24 within the bone-marrow channel of the
femur.
Another anti-rotation embodiment of the artificial hip joint is
illustrated in FIGS. 8 and 9, wherein the rotation preventing means
includes a plurality of knife edges 118 integral with and extending
longitudinally along pin 24 for cutting into the femur so as to
prevent rotation of the femur head prosthesis relative to the
femur.
An alternative anti-rotation feature is illustrated in FIG. 10,
wherein a sharpened spade end 120 extends from the end of pin 24 to
be driven into the bone-marrow channel 114 of femur 116 beyond a
reamed portion 122 within the bone-marrow channel. The spade end
may also include blades 124 (FIG. 11) integral with the spade for
engaging the femur and for preventing rotation of pin 24 relative
to the femur.
Additional embodiments of the anti-rotation feature of the
invention are illustrated in FIGS. 12-17. As shown in FIG. 12,
shoulder 60 is provided with a key 126 connected thereto and
extending outwardly and downwardly from the shoulder for fitting
into cut-out portion or slot 112 in the femur. Where collar 80 is
utilized (FIG. 13), a keyway 128 is provided in the collar to
receive key 126 and to assist in preventing rotation of pin 24
relative to the femur.
In a further anti-rotation embodiment (FIG. 14), shoulder 60 has an
aperture 130 therein and a square headed pin 132 or other shaped
pin having a head to bear against the sides of femur slot 112 is
positioned within aperture 130 and extends outwardly and downwardly
from shoulder 60 for positioning within femur slot 112 and to
prevent rotation of pin 24 within the femur.
Rotation of pin 24 within the femur may also be prevented by means
of the embodiment illustrated in FIG. 15. In this arrangement,
shoulder 60 is provided with a cavity 134 and pin 24 is provded
with an aperture 136. A rod 138 is positioned within shoulder
cavity 134 at one end and is located along pin 24 with a second end
of the rod positioned within pin aperture 136. A femur slot 112 is
again cut into the femur for receiving rod 138, and this prevents
rotation of pin 24 within the femur.
An additional anti-rotation feature of this invention is
illustrated in FIG. 16 wherein a member 131 defining a plurality of
corners 133 is integral with the pin and immediately below
shoulders 60. Member 131 is preferably substantially square in
cross section and corners 133 preferably extend substantially
parallel with the axis of pin 24.
The dimensions of the cross-section of square member 131 may be
such that the length of each side of the square is equal to the
diameter of pin 24 adjacent to shoulder 60. Alternatively, the
sides of square member 131 may be larger than the diameter of pin
24.
In performing the operation of inserting the artificial hip joint
of this invention, it may frequently be desirable to avoid
completely severing the greater trochanter. Accordingly, it may be
desirable, for this reason, to form shoulder 60 with a flattened
side 61, as illustrated in FIGS. 16 and 17 whereby the flattened
side can be positioned in abutting relationship with the greater
trochanter 63. This positioning of shoulder 60 and of flattened
side 61 flush with the greater trochanter, of course, also prevents
rotation of the femur head prosthesis with respect to the femur,
and the anti-rotation feature of flattened side 61 is also enhanced
by the fact that side 61 is preferably oriented substantially
parallel with the axis pin 24. It is, of course, within the scope
of this invention to provide for a prosthesis as described, but
having flattened side 61 without the use of member 131 or to
provide for a prosthesis as described but having member 131 without
flattened side 61 or shoulder 60.
Another embodiment of the invention designed to prevent relative
movement or rotation between inserts 30 and acetabulum prosthesis
head 13 is illustrated in FIG. 18. Prevention of rotation between
inserts 30 and acetabulum prosthesis head 13 is important because
the hip is designed for relative movement between inserts 30 and
hip ball 28. The hip ball and the inserts are specifically designed
for this purpose and are made of materials to withstand frictional
movements therebetween. However, acetabulum prosthesis head 13 and
inserts 30 are not so designed and relative movement between head
13 and inserts 30 is to be avoided. In addition, it is desirable to
maintain entry slot 94 and entry passage 96 aligned so that it is
always possible to insert or remove flexible ring member 92. Of
course, if entry slot 94 and entry passage 96 were permitted to
move relative to one another, it would not be possible to insert or
remove the flexible ring member until entry slot 94 and entry
passage 96 were realigned.
Therefore, one embodiment of this invention provides for a
projection 140 on at least one of inserts 30, and acetabulum
prosthesis head 13 is formed with a depression 142 therein for
receiving projection 140 so as to prevent relative movement of
inserts 30 with respect to head 13. If desired, depression 142 can
be so positioned that it also acts in the manner of extension well
108 in the embodiment of FIGS. 2-4 to permit the entry of a tool
for grasping flexible ring member 92.
As previously explained, experience has shown that it may often be
desirable, due to wear or malfunction of the artificial hip joint,
to repair or replace the bearing surfaces of the joint after some
period of use by the patient. For this reason, this invention
provides for the easy removal of inserts 30 from the artificial hip
joint. However, if the bearing surfaces of the joint require
replacement or repair after some period of use by the patient, it
may be desirable to remove and replace hip ball 28, and this
removable feature is illustrated in FIGS. 19 and 20.
As illustrated in FIG. 19, hip ball 28 is removably positioned on
curved neck 26, and the hip ball is provided with an aperture 144
therein. Neck 26 is also provided with an aperture 146 in alignment
with hip ball aperture 144, and a holding pin 148 extends through
apertures 144 and 146 for holding hip ball 28 on neck 26. Holding
pin 148 is frictionally and tightly held within apertures 144 and
146 so that hip ball 28 is firmly and fixedly held on to neck 26
during use of the artificial hip joint. However, when it is desired
to remove hip ball 28 from the neck, pin 148 may be hammered out
from apertures 144 and 146 to facilitate repair of the hip ball or
replacement thereof.
An alternative embodiment of removable hip ball 28 is illustrated
in FIG. 20 wherein neck 26 is provided with a free and tapered end
150. Hip ball 28 is provided with a tapered opening 152 for tightly
engaging tapered end 150 of the neck. Thus, the hip ball can be
pressed onto the tapered end 150 of neck 26 to be firmly held in
position. Hip ball 28, however, is also provided with a hole 154
extending between the exterior surface of the hip ball and in
communication with tapered opening 152 within the hip ball for
facilitating removal of the hip ball from the neck by conventional
tools (not shown).
A further embodiment of the artificial hip joint, and particularly
the insert, is illustrated in FIG. 21. In this embodiment,
acetabulum prosthesis 10 is provided with threaded grooves 160.
Insert 162 is formed of one single piece and includes an integral
threaded ring portion 164 for threadedly engaging acetabulum
prosthesis grooves 160. Insert 162 further defines notches 166
adjacent to threaded ring 164 for enabling the insert to be screwed
into position with the ring threadedly engaging grooves 160.
As in the previous embodiments, the insert socket 12 defines more
than a hemisphere so that the hip ball is retained within the
socket to prevent postoperative separation.
The insert illustrated in FIG. 21 is preferably comprised of
plastic, such as ultra high molecular weight polyethylene. The
plastic is initially heated to cause expansion, and hip ball 28 is
then popped into socket 12. The insert is then allowed to cool so
that it contracts around the hip ball, and the insert with the hip
ball therein is then screwed into acetabulum prosthesis 10 by means
of threaded ring 164 and grooves 160 until the insert is tightly
positioned within the acetabulum prosthesis.
If desired, and where insert 162 is comprised of metal, insert 162
is preferably formed as two pieces. This embodiment is illustrated
in FIG. 22, and the insert in this embodiment is preferably
comprised of cobalt alloy, such as ASTM F75-67.
In assembling the embodiment illustrated in FIG. 22, the two pieces
of insert 162 are first positioned around hip ball 28. The pieces
of the insert are formed so that faces 168 abut against one another
in contiguous relationship. The assembly of the hip ball together
with the two pieces of the insert is then screwed into acetabulum
prothesis. 10 with threaded ring 164 engaging grooves 160.
The embodiments described and illustrated in FIGS. 21 and 22 are
particularly advantageous. The unitary construction of the inserts
renders the hip extremely rugged and permits it to withstand large
forces and stresses. Additionally, the threaded grooves within the
acetabulum prosthesis and the threaded ring integral with the
insert permit the insert to be readily removed from the acetabulum
prosthesis in the event that the insert needs to be replaced or
repaired. This, of course can be done even after the hip has been
inserted in the patient.
The present invention, thus provides for an extremely versatile and
durable artificial hip joint that is inexpensive to manufacture and
which is designed to facilitate easy replacement of bearing surface
portions of the artificial hip joint, if and when such replacement
becomes necessary or desirable. The artificial hip joint of this
invention also provides for novel anti-rotation means that act in
conjunction with the femur to prevent rotation of the artificial
hip joint relative to the femur. This, of course, is extremely
important for the successful use of the hip joint and this
anti-rotation feature also permits the patient to quickly gain the
full use of the hip joint after insertion of the hip joint.
The invention in its broader aspects is not limited to the specific
details described, and departures may be made from such details
without departing from the principles of the invention and without
sacrificing its chief advantages.
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