Note: Descriptions are shown in the official language in which they were submitted.
~073~
This in~ention rela~es to a pros~heti~ joint, and more
particularly to a prosth~tic joint for total knee replace- -
mentO The prosthe~ic joint is adapted to be implanted in
the body of a sub;ect human or animal.
Heretofore, prosthetic joi~ts have been used to "
replace defec~ive natural joints in humans and animals when such ~'
joints have become diseased,or injured through accident.
However, prior art prosthet~G members ha~e no~ been-whollY sa~ '
10 i8factory for knee implantation because they do not provide - ~;
for the complexity involved when flexing the tibia relative
to the femur. Furthermore, the prior art prosthetic joints
do not provide for replacement of wear surfaces without com-
pletely removing the implanted unit. Some prior art pros~
thetic joints tend to become inoperative because of wear.
This may reduce,their abllity to perform the complicated move
ments inherent in nat~ral ~nee joints, While suitable prosthetic
members h~ve been devised utilizing simple ball joi~t
construction, it has been found that a surface-to-surface
20 conta t o~ the external parts of the joint provide better move-
ment. This surface-to-surface external contact of the spaced-
apart prosthetic members cause wear of the surfaces and in
time replacement is required.
Accordingly, it is an object of this invention to
provide a new and improved jbint prosthesi~ for total knee
replacement which enables replacement of worn par~s without
necessitating the complete removal of the implanted units.
,........................................ .
73~5~ ~ -
Thus the present invention provides a joint
prosthesis comprising a first prosthetic member for fixation
to a first skeleton element and including a convexly shaped
articulation surace or location at the distal end of said first
skeleton element, a second prosthetic member or fixation to
a second skeleton eIement adjacent said first skeleton element,
link means interconnecting first and second prosthetic members
for pivotal movement relative to one another, a removable plateau
secured to said second prosthetic member and providing an
engagement surface for said first prosthetic member, said link ~`~
means pivotally connecting-said first and second prosthetic
members to provide a sliding engagement between said convexly
shaped articulation surface and said engagement surface of said
plateau, and removable fastener means extending through said
plateau and engaging with the said second prosthetic member,
whereby said plateau can be selectively removed and replaced
when worn.
In one aspect of the invention a preferred embodiment
is provided wherein said second prosthetic member has a boss
extending upwardly therefrom, and a recess formed in said
plateau to receive said boss and prevent rotational movement
of said plateau relative to said second prosthetic member.
Preferably, said plateau includes a front wall portion
immediately in front of said boss to define an end wall surface
of said recess, aligned apertures extending through said front
wall portion and said boss, and fastener means extending through
said aligned aperture to retain said plateau to said second
prosthetic member. Also preferably the joint prosthesis is ;~
provided wherein said fastener means is a threaded shaft having
one end thereof split, a chamfer ormed at one end o~ said boss
to receive the split end of threaded shaft, by the split end
can be spread to retain the threaded shaft in position.
~ 3~S~
Briefly, the femoral member of the joint pros-
thesis includes two locking pins designed to prevent the
ball and socke~ components from subluxating after insertion.
The tibial member is provided with a boss to receive a
recess in a plateau which forms a bearing surface between
the femoral and tibial members. The plateau structure
allows a surgeon to replace.it in the event of signiflcant
wearing bf th~ bearing material~ Also the ball and
socket unit can be replaced by the construction o~ the
present invention.
Instead of being pressed over a narrow pin,
which makes replacement very difficult, the plateau slides
oveL a metal boss formed on the upper surface of the
tibial member and ls held in place by a ball stud anchor
screw. The ball stud is inserted into a blind hole and
held in place by the ball stud anchor screw which extends
~ra~sversely therethrough. There~ore, threading o~ the
ball stud into the tibial member is unnecessary and ~hereby
fac~litates removal o the components.
In order to avoid the possibility of the anchor
screw moving or backing out of the boss member, druc~ate
slots have been cut into the posterior aspect of the anchor
screw to provide diametrically opposed locking tab members
at the end thereof. The locking tab members are flared
out to conform to the shape of a chamfer on the po3terior
aspect of the metal boss of the tibial component. If re-
placemen~ of the ball and/or plateau is necessary, the
: `` 3L073~
anchor screw can be easily removed with a socket head
hexagon wrench. During removal of the ball and/or plateau,
the femoral and tibial components inserted into the corres-
ponding bone members remain intact.
. Many of the obvious features and advantages
of this invention will be more fully realized and under-
stood from the following detailed description when taken
in conjunction with the accompanying drawings wherein like
reference numerals throughout the various views of the drawings
are intended to designate similar elements and components.
Brief Descriution of the Drawings
.
Fig. 1 is an assembled view of a joint prosthesis
constructed in accordance with the principles of this in-
vention;
Fig. 2 is a side sectional view of the joint
prosthesis of Fig. l; and
Fig. 3 is an exploded view illustrating the re-
moval of components in accordance with the principles of
this invention.
Detailed Description of the Illustrated Embodiment
Referring now to the drawings there is seen
a joint prosthesis which is constructed in accordance with
the principles oE this invention and designated generally
by reference numbex 10. The joint prosthesis 10 is shown
in relation to its connection to the end portions 11 and
12 of the associated distal femur and proximal tibia, respectivel~.
--4--
~ ~ 7 3~ S~
The prosthesis joint number 10 is formed of a first pros-
thetic member 13 inserted into the femur and a second pros-
thetic member 1~ inserted into the tibia. The distal end of the
femur, and proximal enfl Qf the tibia are prepared by cu~t~n~ and/or
reaming the end portions so that the prosthetic members
13 and 14 can have thelr associated stem elements 13a and
14a inserted in such a manner as to function similar to the
pivotal sliding action of the medial condyle and lateral
condyle of the actual bone elements being replaced. The
prosthetic member 13 is joined with the prosthesis member
14 by means of a ball and socket configuration indicated
generally by reference numeral 16 and an anchor pin 17.
The anchor pin 17 is nonthreaded and is slidably fitted
into an aperture 18 formed in the tibial member.
Most advantageously, a plateau member 20 is re-
movably secured to the tibia member 14 so that it can be
replaced if necessary without removing the ~emur stem 13a
or tibia stem 14a from the bone structures. The plateau
member 20 has a recess 21 formed therein to be positioned
over a boss member 22 formed on the tibia member. The pLateau
has a front wall portion 23 which has an aperture 24 extending
therethrough and which is placed în position with an aper-
ture 26 formed in the boss 22. The anchor pin 17 has an
aperture 27 which is placed in alignmen~ with apertures
24 and 26 and an anchor screw 2~ passes through the aligned
apertures. The anchor screw 28 preferably has a socket
head hexagon wrench fitting 28b formed at one end theleof
--5--
` ~73~51
to facilitate removal of the anchor screw when the plateau
is to be changed. Also when the anchor screw is removed
the anchor pin 17 can be removed to facilitate replacement
of the ball member 16b positioned within the socket 16a
- of the ball and socket unit 16.
To maintain the ball 16b within the socket 16a
in its proper position locking pins 30 and 31 are provided
through angularly disposed boss members 32 and 33, respectively.
The locking pins may be threaded and also provided with the
socket head recessed screws to facilitate removal if neces-
sary. The tibia member has upwardly directed flanges 36
and 37 formed on the side portions thereof so that flat
side margins of the plateau are held firmly in place.
To insure that the stem member 13a is held securely
within femur 11 longitudinal slots 40 and 41 are provided
thereby providing biting edge sections to prevent rotational
movement relative to the femur. Similarly, slots 42 and 43
are provided in the stem of 14a to grip the tibia and prevent
rotational movement therebetween.
The joint prosthesis disclosed herein therefore
provides a simple and efficient means for replacing parts
which may wear as a result of normal use without requiring
complete removal of the structure from the femur and tibia.
By loosening and removing the threaded pin 28 the plateau
20 can be removed. Similarly the ball 16b can be replaced
if desired.
73~5~
To insure that the thxeaded pin 28 does not in-
advertently loosen from its position it is provided with a
cruciate slot which is flared at 28a to conform to a chamfer
within the aperture 2~ of the boss 22.
What has been described is a simple and efficient
joint prosthesis structure for implanta~ion in the human
skeleton, and which joint p~osthesis is readily disassem~led
after implantation to facilitate replacement of worn parts,
if necessary. While a single specific embodiment of the pre-
sent in~ention has been disclosed herein it will be under-
stood that the var~ations and modifications may be effected
without departing from the sp~rit and scope of the novel
concepts of thls invention.
