U.S. patent number 3,874,003 [Application Number 05/347,621] was granted by the patent office on 1975-04-01 for artificial hip joint.
This patent grant is currently assigned to Oscobal AG. Invention is credited to Kurt Karpf, Heinz Moser.
United States Patent |
3,874,003 |
Moser , et al. |
April 1, 1975 |
Artificial hip joint
Abstract
An artificial hip joint, wherein an artificial femur head is
fixed in the femur and a socket having two pins is secured in the
pelvis. The apparatus includes special tools for fixing the socket
in the pelvis in a proper position particularly determined by bores
taking up said pins, and the ball head may be located in different
positions on a pin of the femur shank and is secured from
unintentional twisting once it is mounted thereon in its final
position.
Inventors: |
Moser; Heinz (Selzach,
CH), Karpf; Kurt (Holderbank, CH) |
Assignee: |
Oscobal AG (Selzach,
CH)
|
Family
ID: |
4283699 |
Appl.
No.: |
05/347,621 |
Filed: |
April 4, 1973 |
Foreign Application Priority Data
Current U.S.
Class: |
623/23.11;
606/85; 606/96 |
Current CPC
Class: |
A61B
17/1668 (20130101); A61F 2/4609 (20130101); B62D
49/007 (20130101); A61F 2/32 (20130101); A61B
17/1659 (20130101); A61F 2002/365 (20130101); A61F
2002/30906 (20130101); A61F 2002/30892 (20130101); A61F
2002/4619 (20130101); A61F 2002/3412 (20130101); A61F
2002/3417 (20130101); A61F 2002/4631 (20130101); A61F
2230/0058 (20130101); A61B 17/175 (20130101); A61F
2002/3429 (20130101); A61F 2220/0033 (20130101); A61F
2/4603 (20130101); A61F 2002/30179 (20130101); A61F
2002/3054 (20130101); A61F 2002/30772 (20130101); A61F
2002/30879 (20130101); A61F 2310/00029 (20130101); A61F
2002/30331 (20130101); A61F 2002/30332 (20130101); A61F
2002/3631 (20130101) |
Current International
Class: |
A61B
17/16 (20060101); A61F 2/32 (20060101); B62D
49/00 (20060101); A61B 17/17 (20060101); A61F
2/00 (20060101); A61F 2/30 (20060101); A61F
2/34 (20060101); A61F 2/46 (20060101); A61F
2/36 (20060101); A61F 001/00 () |
Field of
Search: |
;3/1
;128/92C,92CA,92R,92BA,92BB,83 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Yasko; J.
Attorney, Agent or Firm: Imirie, Smiley & Linn
Claims
What we claim is:
1. An artificial hip joint, comprising an artificial femur head
having a femur shank and ball head mounted thereon, and a socket,
said femur shank having a support pin projecting from an upper end
thereof and a collar about the base of said pin, said ball head
having a bore which is disposed on said pin of the femur shank and
is secured from unintentional twisting by pegs projecting axially
at a face of the ball head for cooperative engagement with
depressions in said collar of the femur shank, said bore of the
ball head having an axis offset from a diameter line of the ball
head, whereby said ball head may be disposed on said pin and fixed
by said pegs and depressions in various relative angular positions
for selection of various positions of said ball head relatively to
said femur shank.
2. An artificial hip joint as claimed in claim 1, in which the ball
head has a neck extension on which the pegs are disposed.
3. An artificial hip joint as claimed in claim 1, in which the ball
head has a bore, the axis of which is offset between 5.degree. and
15.degree. from a diameter line.
4. An artificial hip joint as claimed in claim 1, in which the ball
head has four axially projecting pegs arranged cross-wise.
5. An artificial hip joint as claimed in claim 1, in which the
artificial femur shank has at least approximately smooth
surfaces.
6. An artificial hip joint as claimed in claim 1, in which the
shank has annular teeth.
7. An artificial hip joint as claimed in claim 1, in which the
collar has a bore in its rear portion.
8. An artificial hip joint as claimed in claim 1, in which the
collar has four depressions arranged cross-wise at whose point of
intersection said pin is disposed and is tapered.
9. An artificial hip joint as claimed in claim 1, in which the axis
of the shaft and the axis of the pin subtend an angle of
126.degree..
10. An artificial hip joint as claimed in claim 1, in which the
neck of the ball head is symmetrical.
11. An artificial hip joint as claimed in claim 1, in which the
ball head has an asymmetrical neck.
12. An artificial hip joint as claimed in claim 1, in which the
femur shank is curved and the rear part of its upper end is
provided with a reinforcement.
13. An artificial hip joint as claimed in claim 1, in which the
ball head consists of plastics material.
14. An artificial hip joint as claimed in claim 1, in which the
shank consists of Co - Cr - Mo alloy.
15. An artificial hip joint as claimed in claim 1, in which the
femur shank is sand-blasted.
16. An artificial hip joint as claimed in claim 1, in which the
socket has two pins.
17. An artificial hip joint as claimed in claim 1, in which the
socket is provided on its outer surface with radially extending
ribs.
18. An artificial hip joint as claimed in claim 1, in which the
socket is at least partially provided with a rim on its
circumference.
19. An artificial hip joint as claimed in claim 1, in which the
socket is chamfered on the medial side.
20. An artificial hip joint as claimed in claim 1, in which the
inner radius of the socket corresponds approximately to that of the
ball head.
21. An artificial hip joint as claimed in claim 1, in which the
socket consists of a Co-Cr-Mo alloy.
Description
BACKGROUND OF THE INVENTION
The present invention concerns an artificial hip joint.
The purpose of artificial hip joints is the replacement of natural
hip joints in order to return freedom of movement to a person with
a diseased hip joint.
Artificial joints for the replacement of the hip joint are known.
It should be noted that at first only the ball at the top of the
femur was replaced. Only later were both parts of the hip joint
replaced, that is to say, the socket in the pelvis and the ball at
the top of the femur. Operations which require only the replacement
of the ball of the joint were and still are today carried out using
an artificial femur head. This artificial femur head has a shank
for insertion into the medullar cavity of the femur, the shank
being provided near one end with an enlargement having a bearing
surface for abutting the upper surface of the femur and adjoining
this, a pin for receiving the ball of the joint. Conventional
artificial femur heads have a capitulum in contact with the
acetabulum and a shank portion intended for insertion into the
medullar cavity of the femur, a demountable joint being provided
between the capitulum and the shank part.
Another known embodiment comprises a rod-like portion and an
enlarged portion and a ball head which is intended to be provided
on the top of the remainder femur by a supporting surface and the
center of the ball head is disposed externally of the longitudinal
axis of the stem. The ball head is provided on a neck part and the
plane through the center of the ball head and the supporting
surface, viewed in the direction of the narrow side of the
artificial joint to the center plane of the flat stem, subtends an
angle, and that the supporting surface on the underside of the neck
member, viewed in the direction of the wide side of the artificial
joint, is arranged perpendicularly to the said plane through the
middle of the ball head, whilst the lower rod-like part of the
shank is approximately twice as long as its enlarged part.
In conventional artificial joints, the ball is mounted on a
cylindrical part. If, for any reason, the ball does not run freely
in the socket, attrition occurs on account of the friction of the
ball on the pin of the shank and is considerable because of the
relatively small diameter of the pin leading rapidly to an unsteady
connection. Furthermore, in a subsequent operation for replacing
the artificial joint, there are often difficulties in extracting
the rooted or cemented-in artificial joint, so that the operation
takes a long time, a feature which has extremely harmful
consequences on the patient.
In addition to these artificial femur heads, total artificial hips
are also known in which both parts of the joint, that is to say,
both the ball and the socket, can be replaced. However, with such
artificial joints difficulties arise which should not be neglected,
since, due to the strong forces arising with the loading of the
joints, the originally good joint surfaces become deformed or even
damaged. The resultant bad qualities or frictional characteristics
of the joint make movement difficult, causing pain and the
surrounding tissues may, due to the resultant products of
attrition, tend to produce corresponding reactions and this may
lead to the artificial joints having to be replaced in a further
operation.
These disadvantages were avoided by the feature that different
materials were used for the socket and the ball. Plastics materials
were used for the sockets and metals for the balls. The metal heads
were fixed into the previously prepared medullar cavity of the
femur. Either the artificial femur shank had so-called windows for
this purpose, through which it was possible for the bone to grow or
a plain shank was cemented into the medullar cavity.
Similarly, the plastics material socket was cemented into the
pelvis. The outer radius of the plastics material socket, however,
depends on the structure of the skeleton, just as its wall
thickness depends on the loads to be expected. The consequence of
this is that the inner radius and, therefore, the radius of the
ball, are small, whereby, after a certain lapse of time the socket
becomes worn out from friction, since the resultant forces exceed
the resistance of the surface of the plastics material socket, and
this naturally necessitates the replacement of the joint.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the
disadvantages of conventional artificial femur heads.
Another object of the present invention is to provide a total
artificial hip joint having none of the disadvantages of
conventional joints of this kind.
A further object of the present invention is to provide a hip joint
which can be adjusted to the given conditions of the skeleton.
Yet another object of the present invention is to construct an
artificial hip joint in which all the individual parts are inserted
into the body in a predetermined position.
A further object to be achieved by means of the present invention
is to provide an artificial hip joint which can be easily and
rapidly inserted.
Another object of the present invention is to indicate a method of
operating for inserting the artificial hip joint.
These objects are achieved in accordance with the present
invention, on the one hand, by an artificial hip joint, comprising
an artificial femur head with a femur body and ball head and a
joint socket, in which the ball head is located on a pin of the
femur shank and is secured against unintentional twisting by means
of pegs which engage in depressions in the collar of the femur
shank, and the joint socket has two pins which determine and secure
its position in the pelvis.
A preferred embodiment of the artificial hip joint of the present
invention is characterised in that the ball head has a ball neck
extension on which the pegs are disposed.
The most important advantages of the present invention reside in
the feature that it is possible to comply within very wide limits
with the given conditions of the skeleton, since it is possible to
copy the direction of the bones, medially, laterally, posteriorly
and anteriorly, so that the ball head is mounted on the pins of the
artificial femur head in the appropriate corresponding
position.
Furthermore, the two pins of the socket are protected from small
movements which could lead to subsequent loosening.
The present invention will be described further, by way of example,
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a section through part of a skeleton with inserted
artificial joints, the right hip joint being replaced by an
artificial femur head and a left hip joint by a total artificial
hip according to the present invention;
FIG. 2 is a side elevation of the artificial femur head with a
mounted ball head of this invention;
FIG. 3 is a plan view of the artificial femur shank shown in FIG.
2;
FIG. 4 is a section through a joint socket of the present
invention;
FIG. 5 is a plan view of the socket shown in FIG. 4;
FIGS. 6a,b,c,d,e and f are side views of the present ball head in
the normal, lateral and medial directions and plan views in the
normal, anterior and posterior directions;
FIG. 7 is an alternative embodiment of the upper part of an
artificial femur shank with an alternative mounting of the ball
head according to the present invention;
FIG. 8 shows a view of a rasp used for shaping the medullar cavity
in the femur shank;
FIG. 8a shows a milling cutter associated with the rasp according
to FIG. 8;
FIG. 9 is a section through a socket inserting device with mounted
socket;
FIG. 10 is a section through a drill gauge for drilling two holes
in the acetabulum, in which the pins of the joint socket engage;
and
FIG. 10a is a plan view of the drill gauge according to FIG.
10.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a pelvis 13 and two femurs 14 and 15, in which shanks
16 and 17 of artificial femur heads are inserted in the medullar
cavities 56 and 57. The artificial femur heads are positioned on
the surfaces 22 and 23 of the remaining part of the femurs by
bearing surfaces 18 and 19 of collars 20 and 21. The left side of
FIG. 1 shows a right hip joint in which a ball head 24 extends
directly into the natural socket 25 of the joint and co-operates
therewith. The right side of FIG. 1 shows a left hip joint which is
replaced by a total artificial hip, since the natural socket is
replaced by an artificial socket 26.
FIGS. 2 and 3 shows in more detail how the artificial femur head is
constructed. It should be noted that the length of the shank 16 can
be adapted in accordance with the dimension of the skeleton and the
forces involved. In order to protect the shank 16 from
unintentionally sinking into the femur 14, the bearing surface 18
has been considerably enlarged on the medial side. Similarly, the
lateral reinforcement 27 on the shank minimises twisting in the
femur 14. The collar 20 is provided in its rear portion with a bore
28 serving to secure the possibly separated trochanter major in
position again by means of an incercling. Alternatively, in the
event of infection, an extracting device can be engaged in this
bore. The collar 20 is provided with four depressions 29 on its
side opposite to the shank 16 and the bearing surface 18, shown in
plan in FIG. 3 and in a side elevation in FIG. 2. In order to
receive the ball head 36, the artificial femur shank 16 has, at the
point of intersection of the depressions 29, a tapered pin 30, the
axis 58 of which normally forms an angle of 126.degree. with the
axis of the shank. The surface of the shank 16 is smooth or
sand-blasted.
FIGS. 4 and 5 show a hip socket 26 constructed in accordance with
the present invention. Its shape, which is adapted as far as
possible to that of the natural socket, is clearly shown. Two pins
31 and 32 are provided which accurately secure the socket 26 in
holes 60 in the acetabulum and, may be considered as a special
feature. The two pins are each provided with a groove 34 through
which excess cement can flow out during the cementing-in process.
Radially extending ribs 33 also serve to secure the position of the
socket 26 in the pelvis 13.
Due to the fact that metal, such as a Cr-Co-Mo alloy, is used as
socket material, and the ball head consists of plastics material,
such as, polyethylene, the inner surface 35 of the socket 26 is not
damaged in any way by the use of the hip joint. Hence any
replacement of the cemented-in socket 26, with all its
disadvantages is completely unnecessary, except in the case of
infections.
FIG. 2 shows another ball head 36 with a symmetrical neck extension
64 and a bore 65 which is slipped on the taper pin 30 of the femur
shank.
In contrast to this, FIG. 7 shows a ball head 37 with an
asymmetrical neck extension 66 and a decentred bore 67, the axis 68
of which subtends, with the center line 69 of the ball head 37, an
angle of between 5.degree. and 15.degree..
FIGS. 6a,b,c,d,e and f show the various basic directions of the
axes of the hip joint which may be considered with the same
artificial femur head, and also with a single total artificial hip
without replacing any cemented-in artificial part. It is sufficient
if the ball head 36, shown in FIG. 2, by means of which the normal
direction shown in FIGS. 6a and 6d is achieved, is replaced by the
ball head 37 shown in FIG. 7, a feature which can be realised
without difficulty, since both ball heads 36 and 37 are simply
slipped on the taper pin 30. The lateral direction, FIG. 6b, is
obtained if the ball head 37 is slipped on the pin 30 so that the
centre 61 of the ball is disposed above the axis 38 of the pin.
However, the medial direction, FIG. 6c, is obtained if the same
ball head 37 is slipped on the pin 30 so that the centre 61 of the
ball is below the axis 58 of the pin. The anterior and posterior
directions, in turn, are obtained with the same ball head 37 if the
latter, as shown in FIGS. 6e and 6f, are slipped on the taper pin
30 so that the centre 61 of the ball is disposed behind or in front
of the axis 58 of the pin. These five basic directions are
accurately determined by the position of the pegs 38 of the ball
heads 36 and 37 and the position of the corresponding depressions
29 of the collar 30, into which they fit.
The artificial femur shank 16, shown in FIG. 2 is cemented-in, as
is the socket 26. However, as cementing-in involves undesirable
side effects, heat development with the setting of the cement,
monomer separation and also longterm effects which have not yet
been completely explained, is is a great advantage if the use of
bone cement can be abandoned.
However, in order to fix the artificial shank in position, it must
be formed as shown in FIG. 7. The shank 16 is initially rasped
approximately to the thickness A. When the shank is subsequently
introduced into the medullar cavity 56 of the femur 14 (FIG. 1),
the residual bone material is rasped away by the teeth 39 of the
shank 40 so that this material collects in the depressions between
the teeth 39, a feature which may lead to adhesion of the
artificial femur shank. During the subsequent ossification the
artificial shank then becomes firmly rooted in the femur.
The rest of the construction of this artificial femur shank 40
corresponds in all other requirements to that according to FIGS. 2
and 3, since otherwise the replaceability of the individual ball
heads would be placed in question.
It will be easily seen that the artificial hip joint of the present
invention, whether as an artificial femur head or as a total
artififical hip joint, represents an artificial hip on a building
block system, in which only the ball heads have to be replaced in
order to obtain the most natural positions of the femur possible.
It is obvious that extreme conditions of the bones can be further
compensated by suitably adapted artificial femur shanks and
sockets.
In order to insert the artificial hip of the present invention as
rapidly and as easily as possible, a few special instruments or
tools are necessary, as will be apparent from the following
description. For example, a rasp, as shown in FIG. 8, is required,
comprising a rasp member 41 and a handle slipped and fixed on a
pin. The medullar cavity 56 of the femur 14 is shaped with the rasp
41. This rasp 41 should preferably have the same dimensions as the
artificial femur shank 16, or thickness A of the shank 40. After
the initial rasping process, the handle is removed and the rasp 60
left in the medullar cavity so that the surface B is flush with the
stump of the femur neck. The pin now projects above the bone. The
stump of the femur neck is milled accurately plane using a milling
cutter as shown in FIG. 8a by way of this pin, and the correct
angle for the bearing surface 18 of the artificial shank is also
accurately obtained thereby.
FIG. 10 shows the drill gauge of the present invention for drilling
the holes in the acetabulum. It has a spherical end 49, the shape
of which approximately matches the shape of the socket part 26.
After the introduction of the drill gauge in the initially milled
acetabulum it is brought to the correct position (45.degree. to the
axis of the body and 10.degree.-20.degree. anteversion) and fixed
by means of the two small pins 52 and 53 which are axially
displaceable and have points 62 and 63, which are hammered into the
acetabulum. The depth of penetration of the pin is accurately
determined by the stops 54, 55. The two holes for receiving the
pins 21 and 22 of the socket 26 are drilled in the acetabulum in
this position by a special spiral drill through the holes C in the
drill gauge. The spiral drill is also provided with a stop so that
the necessary drilling depth can be accurately observed. The
position of the socket 26 is thus accurately determined.
A socket inserting device 42, as shown in FIG. 9, may also be used
with advantage, this device having a spherical end 43 of the shape
of the inner surface 35 of the socket 26, or, in the form of the
ball head 24, on which end 43 the socket 26 can be clamped. This is
effected by means of an elastic holder 44 slipped over an edge 45
of the socket 26. As soon as the socket 26, the outside of which is
filled with cement between the ribs 33 before the insertion in the
pelvis 13, is in its final position, determined by the two bores in
the acetabulum, the handle 46 is pressed in the direction of the
pelvis or towards the end 43, so that the socket 26 is pressed
firmly into the acetabulum, the result of which is that the two
pins 31 and 32 engage in the prepared holes 60 in the acetabulum. A
part 48 is then drawn towards the handle 46 against the bias of a
spring 47. Thus the holder 44 is removed from the end 43 so that it
releases the edge 45 of the socket 46. The socket 26 is thus
inserted in the pelvis and the inserting device can be withdrawn.
After the shank 16 or 40 of the artificial femur head is cemented
in the medullar cavity 52 or pressed therein, the ball head 36 or
37, selected and positioned according to the condition of the
skeleton, can be slipped on the taper pin 30. The actual insertion
of the artificial hip joint is thus completed.
The fact that none of the cemented-in or grown-in parts is
subjected to wear, has proved to be extremely advantageous if for
any reason the ball head has to be replaced, since a small
operative opening is sufficient for removing the ball head from the
taper pin of the artificial femur and mounting a new one.
It is obvious that alterations may be made to the artificial hip
itself, to the method of operation and the set of instruments used
for the purpose without departing from the scope of the present
invention.
* * * * *