Invention (Patent): McCandliss R. Coaxial ligamented hip prosthesis. US5702474A (1997).
US2765787A United States
Inventor: Robert McCandliss
Current Assignee: Individual
Worldwide applications 1996 US
Application US08/589,644 events:
1996-01-22 Application filed by Individual
1996-01-22 Priority to US08/589,644
1997-12-30 Application granted
1997-12-30 Publication of US5702474A
2016-01-22 Anticipated expiration
Status Expired - Fee Related
Coaxial ligamented hip
prosthesis
Robert McCandliss
Abstract
A
hip prosthesis is disclosed herein intended to be fitted into a skeletal pelvis
socket and which has a replacement socket that includes a metal semi-spherical
acetabulum base with a plastic acetabulum liner for movably holding a spherical
ball against the liner by a ligament rod. The rod passes through a head of a
stem implanted into a femur and terminates with a ligament anchor plate fitted
in the acetabulum base via an eyelet and pin connection. A tensioning nut is
carried on the stem head in threadable connection with the rod. A conical
cutout in the spherical ball permits movement of the ball with the apex of the
cone at the center of the spherical ball under adjustable tensioning of the
rod. A Wear compensation system is included by incorporating an open passageway
in the base which communicates with a blister in the liner for accommodating
the introduction of cement to compensate for wear. A boot of mesh material
encloses portions of the base, liner and the ball.
Description
BACKGROUND OF THE INVENTION
1. Field of the
Invention
The present
invention relates to the field of hip prosthesis, and more particularly to a
novel replacement connection between a skeletal femur and pelvis socket that
permits a substantial degree of articulation and includes wear particle
containment as well as a wear compensation system.
2. Brief
Description of the Prior Art
In the past, hip
replacement devices and systems have been employed so that a person may have
normal mobility with respect to leg movement. Problems and difficulties have
been encountered when employing conventional hip replacement devices which stem
largely from the fact that such devices provide limited rotational movement and
stability. For example, conventional hip prosthesis will not permit a person to
sit cross-legged with comfort or even at all without dislocation of the
prosthesis and redoing the surgery. Furthermore, no provisions are made for
subsequent surgery which may be required due to excessive wear on the component
parts. Usually, subsequent surgery requires complete replacement of the
prosthesis. Also, conventional hip prosthesis will not permit for deflection of
debris or particles of components which are ground loose from adjacent
components when the joint is articulated.
Therefore, a
long-standing need has existed to provide a novel hip prosthesis which will
readily provide for torsional loading and which provides rotational stability
over a wide angular range. Additional means should be incorporated into such a
prosthesis which not only provides for particle collection which is due to wear
and which will also compensate for wear conditions between moving parts.
SUMMARY OF THE INVENTION
Accordingly, the
above problems and difficulties are avoided by the present invention which
provides a novel hip prosthesis having a ball joint adapted to be placed into a
pelvis socket, which includes a semicircular base having a lining defining a
socket into which a ball is movably carried. The ball is secured to the end of
a stem head at one end while a ligament tensioning means is carried on the head
of the stem and passes through the ball, terminating in an anchor connection
with the base. The opposite end of the ligament rod includes a square
cross-section length and a threaded section engaging a threaded nut rotatable
against the head of the stem to provide adjust accordingly. An elongated
portion of the stem is implanted into the shaft of a femur. The ball includes a
conical recess with its apex at the center of the sphere through which the
ligament rod passes so that the ball may rotate through a wide angle of
articulation within the liner of the base without stretching the ligament rod.
A close-mesh boot is disposed about the exposed portion of the ball in order to
collect debris and particles which may be ground from component parts during
articulation of the joint. A retaining means is employed for holding the boot
in place and for securement of the component parts together.
Means are further
provided on the base for accommodating cement that may be forced into a
compensation blister within the base and liner without necessity of boot
removal.
Therefore, it is
among the primary objects of the present invention to provide an adjustable
ligament rod within a hip joint prosthesis that provides positive restraint
against dislocation when in use by a recipient.
Another object of
the present invention is to provide a hip prosthesis which may move at extreme
angles of rotation about a femur axis, or in a lateral direction, a ligament
tends to be stretched providing increased elastic resistance to further travel.
Still, a further
object of the present invention is to provide a hip prosthesis wherein the
ligament length remains unchanged during normal rotations of the ball joint in
the acetabulum in the lateral plane, about the femur axis, or in the
front-to-back plane, due to the ligament guide point location at the center of
the spherical ball.
Another object
resides in including a ligament accommodation for rotation about the
horizontal, lateral (Y-Y) by torsion between the ligament-guide-point and the
ligament anchoring pin.
Yet another object
of the present invention is to provide a novel hip prosthesis which permits
subsequent adjustment or renewal of component part fit by providing axis
passageway through which cement can be introduced under local anesthesia.
Another object of
the present invention is to provide a novel coaxial ligamented hip prosthesis
having wear-particle containment boot and which further includes wear
compensation system whereby subsequent adjustment or compensation can be made
due to wear of component parts.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the
present invention which are believed to be novel are set forth with
particularity in the appended claims. The present invention, both as to its
organization and manner of operation, together with further objects and
advantages thereof, may best be understood with reference to the following
description, taken in connection with the accompanying drawings in which:
FIG. 1 is a
diagrammatic view of a skeletal pelvis and femur connected together by the
novel hip prosthesis of the present invention;
FIG. 2 is an
enlarged cross-sectional view of the replacement connection between the femur
and socket of the pelvis shown in FIG. 1;
FIG. 3 is a
transverse cross-sectional view of the connection shown in FIG. 2 as taken in
the direction of arrows 3--3 thereof;
FIG. 4 is an
enlarged fragmentary cross-sectional view of a connection screw holding the
retainer to the base, as shown by the circles indicated by numeral 4 in FIG. 3;
FIG. 5 is an
enlarged fragmentary cross-sectional view of a rivet connection between the
retainer ring and the peripheral edge of the boot, as shown by numeral 5 in
FIG. 3;
FIG. 6 is an
enlarged fragmentary cross-sectional view as taken in the direction of arrows
6--6 Of FIG. 2 illustrating the ligament rod attachment;
FIG. 7 is a
fragmentary cross-sectional view of the wear compensation means utilized in the
present invention for introducing cement into a passageway encircled by the
numeral 7 in FIG. 3; and
FIG. 8 is a
fragmentary cross-sectional view of the square cross-section of the ligament
rod contained within the square hole in the shank of the prosthesis.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG.
1, the novel hip prosthesis of the present invention is illustrated in the
general direction of arrow 10 and the prosthesis is illustrated as
being mounted in a socket area of a pelvis bone 11 and the area is
indicated by numeral 12. The hip prosthesis connects the socket
area 12 with a femur 13. The great trochanter is indicated
by numeral 14 while the lesser trochanter is indicated
by numeral 15. The head of the femur 13 has been removed so
as to accommodate the hip prosthesis. The prosthesis includes a fixed member
taking the form of a shaft 16 which is implanted into the femur 13
which supports a ball 17 projecting into a semicircular
acetabulum base 18 which is secured by conventional means to
the pelvic socket area 12. Part of the ball 17 is exposed
from the base 18 and is fixedly secured to the shank of the
prosthesis 16. The exposed portion of the ball 17 is covered by a
closed mesh boot 20 so that particles or debris may be collected in
the boot due to wear between component parts. The boot 20 is
maintained on the base 18 about its peripheral edge by means of
a retainer 21.
Referring now in
detail to FIG. 2, it can be seen that the acetabulum base 18 is composed
of metal and includes an inner curved surface which is lined by a plastic
acetabulum liner 22. The outer surface of the ball 17 is movably
disposed with respect to the surface of the liner 22 and
the ball 17 is secured to the terminating end of shaft 16 by means of
a wedged fit with a projection 23 inserted into a hole and
terminating at the middle of the ball. Securement may be achieved through the
use of adhesives or the like. It is to be seen that the boot 20 is
fastened about the projection 23 by means of a clamp 24 and
to the retainer 21 by an outer retainer ring 25. The edge
peripheral region of the boot 20 is disposed between the inner
retaining ring 21 and the outer retaining ring 25 and a
plurality of fasteners are employed to secure the boot to
the base 18, such as by screw 26. Such a screw is
illustrated in FIG. 4. In this FIGURE, it can be seen that
the retainer 21 is held in position and releasable securement with
the base 18.
Referring to FIG.
3, the outer retaining ring 25 is held in position by means of
a rivet 27 which couples the outer retaining ring 25 to
the inner retaining ring 26 and the peripheral edge marginal region
of the boot 20 is held between the opposing surfaces of the retaining
rings.
Referring now in
detail to FIG. 2, it can be seen that the base 18 is implanted into
the socket area 12 of the pelvis bone. The upper end of shaft 16
terminates in a frustro-conical portion 23 that is press-fitted into a
mating cavity in the ball 17. If desired, adhesive may also be
employed. Furthermore, a ligament rod 30 extends through
the head 23 of the stem 16 having one end thereof passing through a
conical cutout or recess within the spherical ball 17. The conical
cutout or recess is identified by numeral 31. The end
of ligament rod 30 terminates in a connection 32 which is
carried on an anchor plate 33 by means of an eyelet which passes
through a hole in the end of the rod 30. Such a connection is
illustrated in FIG. 6 wherein the eyelet is represented by numeral 34.
A conical opening 35 in the liner 22 further accommodates
passage of the rod from the head 23 through the conical
recess 31 and the recess 35. The opposite end
of rod 30 terminates in threaded connection with a ligament
tensioning nut 36 that is seated in a receptacle 37 in
the head 23. As the nut 36 is rotated, tension is applied
to the rod 30 to tighten or loosen its connection with
the base 18 via the anchor plate 33. An "O" ring
provides a friction lock and seal and the ring is indicated
by numeral 38. The exposed end of the nut 36 may be
configured with a hex opening 40 in order to receive a suitable
wrench for accomplishing rotation of the nut within the chamber 37.
FIG. 2 also
illustrates the retention of one marginal edge of the boot 20 to
the head 23 by means of a clamp or the like 24. The opposite edge
marginal region of the boot is captured between the opposing surfaces of the
inner and outer rings 21 and 25 respectively. Preferably,
the acetabulum 18 is composed of a metal material while the acetabulum
liner 22 is composed of a plastic material, such as a polyethylene
material. The close meshed boot 20 is composed of a dacron mesh.
A wear compensation
system is employed as part of the present invention which permits
the liner 22 or at least a portion thereof to expand in order to take
up any slack or looseness caused by wearing between the surfaces of
the ball 17 and the opposing surface of the liner 22. As
wear occurs, particles may be dislodged from either of the two components and
these particles are captured by the boot 20. In order to expand a
portion of the boot into closer contact with the surface of the ball, the
compensation system includes an opening 42, as shown in FIG. 3, which leads to
an internal passageway 44 in the base 18 so that a fitting 45, as shown
in FIG. 7, can be placed into the opening 43 in order to introduce a
cement material into the passageway 44. The fitting 45 passes through
an opening in both the inner and outer retaining rings 21 and 25 so that the
tapered and threaded nozzle of the fitting 45 can fit properly into
the passageway 44. As shown in FIG. 2, the passageway 44 is
in communication with a slit chamber or blister 46 in
the liner 22. As the material is introduced to the chamber or blister 46,
expansion occurs between the separated components of the liner 22
causing the liner component, identified by numeral 47, to expand
against the surface of the ball 17.
In FIG. 3, it can
be seen that the hole 43 is open through the base 18 and
that the screw 26 passes through both the retainer rings.
The rivet 27 illustrated in FIG. 5 holds the retaining rings in
clamping relationship with the edge marginal region of the outer peripheral
region of boot 20.
In view of the
foregoing, it can be seen that the ligament rod 30 provides positive
restraint against hip prosthesis dislocation regardless of orientation whether
the person is walking or whether the person may be in a sitting position with
legs crossed. The ligament rod 30 tends to be stretched or tensioned
so as to provide increased elastic resistance to further travel which would
cause dislocation at extreme angles or rotation about the femur axis or in the
lateral direction.
Furthermore, the
ligament length of the rod remains unchanged during normal rotation of
the ball 17 in the acetabulum in the lateral plane about the femur
axis or in the front-to-back plane because of the ligament guide point location
at the center of the spherical ball. The ligament rod accompanies rotation
about the horizontal, lateral (Y-Y) axis by torsion between the ligament guide
point and the ligament anchoring pin. The ligament anchor pin retainer plate
prevents polyurethane wear fragments from getting into tissue behind the
acetabulum and causing inflammation.
Any tension or
slack ligament adjustment is achieved by rotation of the ligament tensioning
nut and Allen type wrench inserted into the hexagon hole at the exposed end of
the nut.
With respect to the
wear compensation system, the slit chamber Dr blister in the polyethylene liner
and the associated flow passageway through the metallic base provide for the
introduction of cement, under pressure, into the chamber or blister, forcing
the worn innersurface of the liner radially inward so as to eliminate the
excessive clearance caused by the wear and, therefore, to re-establish the
spherical configuration at the top of the polyethylene liner.
The Dacron flexible
boot Which may be a sheet which is woven, knitted or crocheted, is disposed
between the prosthesis tapered shank supporting the sphere noted as being the
head of the shaft 16 and the metallic rim of the base wherein the structure
serves to confine the polyethylene wear particles, or foreign matter which
reside inside the joint and the boot prevents migration to the surrounding tissue
and the subsequent inflammation.
The subsequent
surge involved in compensation for wear is expected to be required in 10 to 20
years after prosthesis implant and this may be achieved under local anesthesia.
Only an incision is required to provide access to the threaded socket in the
upper metallic acetabulum base for the introduction of cement under pressure
via the tapered nut. The rest of the prosthesis is not disturbed and minimal
rehabilitation after surgery may be required.
The inventive
prosthesis requires precise angular positioning of the acetabulum assembly in
the pelvis machine socket so as to permit conical opening in the spherical ball
to clear the ligament rod at all normal angles of rotation about all three
axes. The square cross-section portion of the ligament rod prevents torsion of
the ligament rod during Walking from loosening the nut retaining the ligament
rod. Also, it provides torsional restraint to the ligament rod while a surgeon
is tightening the nut.
While particular
embodiments of the present invention have been shown and described, it will be
obvious to those skilled in the art that changes and modifications may be made
without departing from this invention in its broader aspects and, therefore,
the aim in the appended claims is to cover all such changes and modifications
as fall within the true spirit and scope of this invention.
What is claimed is:
1. A hip socket prosthesis for disposal
between a skeletal femur and a pelvis socket comprising:
a metal semi-spherical acetabulum base;
a spherical ball;
a plastic acetabulum liner disposed in
said metal semi-spherical acetabulum for movably holding said spherical ball;
an elongated stem having a head laterally
projecting into securement with said spherical ball; and
a ligament rod movably carried on said
head and secured to said metal semi-spherical acetabulum base for movably
holding said spherical ball.
2. The invention as defined in claim 1
wherein:
said spherical ball includes a recess
occupied by said head and a conical opening coaxially disposed with respect to
said head having its apex terminating at said head and outwardly flaring to
terminate opposite said lining; and
said ligament rod having opposite ends
separated by a midsection movable through said head;
one end of said ligament rod passing
through said conical recess to be anchored with said metal semi-spherical
acetabulum base.
3. The invention as defined in claim 2
wherein:
said end of said ligament rod opposite to
said one end is externally exposed within said head, and
means operably coupled to said end and
bearing against said head for selectively and manually moving said head about
said ligament rod to urge said spherical ball into engagement with said liner.
4. The invention as defined in claim 3
wherein:
said moving means is a tensioning nut for
adjusting the engagement force of said spherical ball against said liner.
5. The invention as defined in claim 4
including:
a boot of mesh material carried between
said head and said metal semi-spherical acetabulum base about said spherical
ball for collecting debris worn from said liner, said base and said Spherical
ball during use.
6. The invention .as defined in claim 5
including:
a wear compensation means having an
expandable portion provided in said liner; and
said base having an open passageway
leading to said expandable portion for introducing an injected cement into said
expandable portion urging said liner into forcible engagement with said
spherical ball.
7. The invention as defined in claim 6
wherein:
said liner includes a central opening
accommodating said ligament rod and said anchoring connection with said metal
semi-spherical acetabulum base.
8. A replacement hip prosthesis for
fitting into a skeletal pelvis socket comprising:
an elongated stem with a laterally
projecting held;
an arcuate socket base with an internal
liner;
a ball secured to said head and bearing
against said liner; and
a ligament rod carried on said head and
slidably extending through said ball terminating in an anchored connection with
said socket base.
9. The invention as defined in claim 8
including:
tension adjustment means disposed between
said ligament rod and said head for selectively adjusting the bearing force
applied by said ball to said liner.
10. The invention as defined in claim 8
including:
a flexible mesh boot having opposite ends
secured to said head and to said socket base respectively for collecting debris
dislodged from said liner, said ball and said socket base during use.
11. The invention as defined in claim 8
including:
means cooperating between said socket base
and said liner for expanding said liner into close load bearing relationship
with said ball.
References Cited
U.S. PATENT DOCUMENTS
2,765,787 10/1956 Pellet 623/23
External links
McCandliss
R. Coaxial ligamented hip prosthesis. US5702474A January 22, 1996. 1997.
patents.google
Authors & Affiliations
Robert McCandliss – 3836 Baywood Dr. Moss Point, Miss., US.
Keywords
ligamentum capitis femoris, ligamentum teres, ligament of head of femur, endoprosthesis, prosthesis, invention, unipolar, subtotal
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