U.S. patent number 3,816,855 [Application Number 05/257,910] was granted by the patent office on 1974-06-18 for knee joint prosthesis.
This patent grant is currently assigned to National Research Development Corporation. Invention is credited to Bahaa Botros Seedhom Saleh.
United States Patent |
3,816,855 |
Saleh |
June 18, 1974 |
KNEE JOINT PROSTHESIS
Abstract
A prosthetic knee joint device comprises a femoral component in
the form of a shell member having two condylar portions with major
convex bearing surfaces areas, which portions are bridged at one
end by a portion defining a trough between the convex areas. An
associated tibial component has similar portions in a platform
bearing member defining major concave bearing surface areas and a
ridge therebetween. The convex bearing areas are longer than the
concave bearing areas and generally U-shaped longitudinally to
simulate the corresponding shaping in the natural joint from which
the shell member can in fact be derived. The concave bearing areas
however simulate the menisci of the natural joint different phases
of rotation to provide an optimized congruity between the bearing
surfaces during rotation of the predetermined geometry of the
prosthesis as compared to the variable geometry in the natural
joint.
Inventors: |
Saleh; Bahaa Botros Seedhom
(Leeds, EN) |
Assignee: |
National Research Development
Corporation (London, EN)
|
Family
ID: |
10109721 |
Appl.
No.: |
05/257,910 |
Filed: |
May 30, 1972 |
Foreign Application Priority Data
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|
|
|
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Jun 1, 1971 [GB] |
|
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18278/71 |
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Current U.S.
Class: |
623/20.31;
264/222; 264/DIG.30 |
Current CPC
Class: |
A61F
2/38 (20130101); Y10S 264/30 (20130101) |
Current International
Class: |
A61F
2/38 (20060101); A61f 001/24 () |
Field of
Search: |
;3/1
;128/92C,92CA,92R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
MG.H. Femoral Condyle Replacements (NO. 6662), Vitallium Surgical
Appliances Catalog, Austenal Company, New York, N.Y., page 62,
1964. .
"Acrylic Prosthesis Replacing Lower End of the Femur For Benign
Giant-Cell Tumor" by G. L. Kraft et al., Journal of Bone &
Joint Surgery, Vol. 36-A, No. 2, Apr. 1954, pages 368-374. .
"Developments In Total Hip Joint Replacement" by G. K. McKee,
Proceedings of the Institution of Mechanical Engineers, Vol. 181,
part 3J, 1966-1967, pages 85-89..
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
I claim:
1. A prosthetic knee joint device comprising:
a femoral component including a shell bearing member having two
first elongate portions and a first bridge portion, said first
elongate portions each being of generally U-shaped form in the
longitudinal direction and generally dished form in the lateral
direction, and the curvatures of such forms being of the same sense
to provide a smooth major surface of overall convex curvature for
each of said first elongate portions, said first elongate portions
being disposed in spaced side-by-side longitudinal relation, said
first bridge portion integrating said first elongate portions in
continuous manner partway along the U-bases and along one pair of
corresponding U-arms thereof, and said major convex surfaces follow
a generally spiral curvature in their longitudinal directions with
increasing radius of curvature towards their non-bridged ends,
and a tibial component including a platform bearing member having
two second elongate portions and a second bridge portion,
said second elongate portions each having a major surface of
generally dished form in both the longitudinal and lateral
directions to provide smooth overall concave curvature,
said second elongate portions being disposed in spaced side-by-side
longitudinal relation;
said second bridge portion integrating said second elongate
portions in continuous manner partway therealong from one pair of
corresponding ends,
and said major concave surfaces follow a more uniform curvature in
their longitudinal directions than do said major convex surfaces,
with said major concave surfaces being more congruous with the
bridged ends of said major convex surfaces,
said femoral and tibial components being disposed in mutual bearing
relationship with their respective bridge portions generally
superposed and their respective non-bridged elongate portion convex
and concave surfaces engaged for mutual sliding and rotation along
the longitudinal directions thereof;
and wherein the major surfaces of said components opposite to said
convex and concave surfaces are adapted by the provision of shallow
configurations thereon for respective fixation to the femur and
tibia by a gap-filling agent.
2. A device according to claim 1 wherein said first bridge portions
defines a first trough, relative to said convex curvature, between
said first elongate portions integrated thereby; and said second
bridge portion defines a ridge relative to said concave curvature,
between said second elongate portions integrated thereby.
3. A device according to claim 1 wherein said convex surfaces are
generally divergent in their longitudinal directions from their
bridged ends, and said concave areas are similarly divergent.
4. A device according to claim 1 wherein said femoral component is
adapted for fixation to the femur with a gap-filling agent by the
provision of a plurality of relatively short members projecting
from the major surface thereof opposite to said convex
surfaces.
5. A device according to claim 1 wherein said tibial component is
adapted for fixation to the tibia with a gap-filling agent by the
provision of a grooved formation on the major surface thereof
opposite to said concave surfaces.
6. A device according to claim 5 wherein each groove of said
grooved formation has a dovetail cross-sectional form.
7. A device according to claim 5 wherein said grooved formations
define generally central regions of the respective surfaces of said
second elongate portions which central regions extend further than
the remainder of such surfaces to define plateaus.
8. A device according to claim 1 wherein said femoral and tibial
components are respectively made of metal and plastics
material.
9. A prosthetic knee joint device, comprising a femoral component
and a tibial component;
the femoral component being a shell having two laterally spaced
convex bearing surfaces respectively closely conforming to the
surface shapes and spatial orientation of the femoral condyles of
the natural knee joint, and having a trough portion bridging
between the two bearing surfaces adjacent their respective
convergent ends for receiving and guiding the patella and
associated tendon should these be retained;
the tibial component being a platform having two laterally spaced
concave bearing surfaces closely conforming to shapes developed
from menisci of the natural knee joint in a plurality of different
phases of rotation thereof, with one pair of corresponding end
portions of said concave bearing surfaces respectfully closely
conforming to the surface shapes of the anterior aspect of said
menisci when said natural knee joint is in a rotational phase of
relatively full extension, the other pair of corresponding ends of
said concave bearing surfaces similarly conforming to the surface
shapes of the posterior aspect of said menisci when said natural
knee joint is in a phase of relatively full flexion, and
intermediate portions of said concave bearing surfaces between the
respective ends smoothly bridging therebetween, said concave
bearing surfaces being dished both longitudinally and laterally,
the corresponding anterior end portions of said platform being held
in spaced, side-by-side relation by a bridge portion which forms a
ridge between the concave dished surfaces and extends into the
trough of said femoral component when these two components are
engaged in a bearing relation representing maximum extension;
the convex bearing areas being longer than the concave bearing
areas and being generally U-shaped longitudinally and low relief
protuberance and recess means formed on the reverses of the two
components from the bearing surfaces, for keying, spacing and
permitting resin fixation of the components without need for
removal of so large amounts of bone from the natural knee joint of
the patient as is generally the case with hinged forms of knee
joint prostheses and without lengthy excursions of foreign material
along the medullary canals.
Description
Various proposals have been made for knee joint prostheses in the
past with varying degrees of success in practice. The more
successful proposals, in terms of alleviation of pain and long term
provision of a useful range of flexion, have involved hinge
devices. However, these last devices are not fully satisfactory in
that they invariably involve the removal of the natural ligaments
and the patella, and, while such devices have their place when the
ligaments have deteriorated beyond possible preservation, it is
frequently only the condition of the cartilage and the adjacent
underlying bone layers which give rise to the need for surgery.
An object of the present invention is to alleviate this
situation.
According to one aspect of the present invention, there is provided
a prosthetic knee joint device comprising:
A FEMORAL COMPONENT INCLUDING A SHELL BEARING MEMBER HAVING TWO
FIRST ELONGATE PORTIONS AND A FIRST BRIDGE PORTION,
SAID FIRST ELONGATE PORTIONS EACH BEING OF GENERALLY U-shaped form
in the longitudinal direction, and generally dished form in the
lateral direction, and the curvatures of such forms being of the
same sense to provide a major surface of overall convex curvature
for each of said first elongate portions,
SAID FIRST ELONGATE PORTIONS BEING DISPOSED IN SPACED SIDE-BY-SIDE
LONGITUDINAL RELATION,
AND SAID FIRST BRIDGE PORTION INTEGRATING SAID FIRST ELONGATE
PORTIONS IN CONTINUOUS MANNER PARTWAY ALONG THE U-bases and along
one pair of corresponding U-arms thereof;
AND A TIBIAL COMPONENT INCLUDING A PLATFORM BEARING MEMBER HAVING
TWO SECOND ELONGATE PORTIONS AND A SECOND BRIDGE PORTION,
SAID SECOND ELONGATE PORTIONS EACH HAVING A MAJOR SURFACE OF
GENERALLY DISHED FORM IN BOTH THE LONGITUDINAL AND LATERAL
DIRECTIONS TO PROVIDE OVERALL CONCAVE CURVATURE,
SAID SECOND ELONGATE PORTIONS BEING DISPOSED IN SPACED SIDE-BY-SIDE
LONGITUDINAL RELATION,
AND SAID SECOND BRIDGE PORTION INTEGRATING SAID SECOND ELONGATE
PORTIONS IN CONTINUOUS MANNER PARTWAY THEREALONG FROM ONE PAIR OF
CORRESPONDING ENDS;
AND WHEREIN THE MAJOR SURFACES OF SAID COMPONENTS OPPOSITE TO SAID
CONVEX AND CONCAVE SURFACES ARE ADAPTED FOR RESPECTIVE FIXATION TO
THE FEMUR AND TIBIA.
In use of the proposed device, the femoral component replaces the
bearing area of the femoral condyles, on the one hand, and the
tibial component replaces the lateral and medial menisci together
with an area of the tibial condyles, on the other hand. For this
purpose the menisci and appropriate parts of the femoral and tibial
condyles are removed, and the respective components secured to
dispose the same in mutual bearing relationship with their bridge
portions generally superposed in the anterior aspect and their
non-bridged elongate portion convex and concave surfaces engaged
for mutual sliding and rotation along the longitudinal directions
thereof.
Regarding the more particular geometry of the device: the convex
bearing surfaces of the femoral component simulates the femoral
condyles and, in fact, it is preferred that such surfaces closely
follow the natural shaping of the condyles. Similarly, it is
preferred that the corresponding surface of the associated bridge
portion should define a trough between the convex bearing surfaces
to simulate, and again preferably follow, the natural form of the
inter-condylar trough which receives and guides the patella and
associated tendon.
The concave bearing surfaces of the tibial component, on the other
hand, do not follow the natural form of the tibial condyles since
the latter are not markedly concave in the natural joint, but
rather the medial one tends to a flat form and the lateral one to a
convex form. Thus, very high stresses would result from direct
engagement between natural condyle shaping for each of the engaging
surfaces of the prosthesis, with inevitable failure in use. In the
present device, the bearing surface form of the tibial component
largely follows that of the menisci which are concave and engage
the femoral condyles in the natural joint. Even then, the shaping
of the menisci varies with the degree of flexion in the natural
joint, and to simulate one phase of the menisci with a prosthetic
part of fixed shaping would also give rise to undesirably high
stresses when the femoral component was in a position corresponding
to a degree of flexion other than that for which the menisci
shaping had been simulated. For this reason, in a preferred form of
the invention, the concave bearing surfaces of the tibial component
follow shapings developed from that of the menisci in different
phases to provide enhanced congruity and reduce stress between it
and the associated femoral part when in use together.
More specifically, according to another aspect of the invention
there is provided a method of making a prosthetic knee joint device
including a femoral component and a tibial component having
respective bearing surfaces for mutual sliding and rotational
bearing engagement, which method comprises:
making a first former with two side-by-side spaced elongate convex
bearing surface areas respectively closely conforming to the
surface shapes of the femoral condyles of a natural knee joint;
making a second former with two side-by-side spaced elongate
concave bearing surface areas respectively closely conforming to
shapes developed from the menisci of said joint in different phases
of rotation thereof, with one pair of corresponding end portions of
said concave areas respectively closely conforming to the surface
shapes of the anterior aspect of said menisci when said joint is in
a rotational phase of relatively full extension, the other pair of
corresponding ends of said concave areas similarly conforming to
the surface shapes of the posterior aspect of said menisci when
said joint is in a rotational phase of relatively full flexion, and
intermediate portions of said concave areas being developed to
smoothly bridge said ends portions;
smoothing said convex and concave bearing surface areas to provide
optimised congruity therebetween in said bearing engagement;
making from said first and second formers respective moulds for
said femoral and tibial components; and
casting said components in said moulds.
In order that the invention may be more fully understood, the same
will now be described by way of example with reference to the
accompanying drawings, in which:
FIGS. 1 and 2 diagrammatically illustrate, in one side view,
femoral and tibial components of the natural knee joint in
extension and flexion, respectively,
FIGS. 3 and 4 similarly illustrate the same components in the
opposite side view,
FIG. 5 diagrammatically illustrates tibial components in a superior
view associated with FIGS. 1 and 2,
FIGS. 6 to 11 illustrate the femoral component of one embodiment of
the present invention in respective plan (inferior) view, inverted
plan (superior) view, one side (medial) view, the other side
(lateral) view, front (anterior) view, and rear (posterior) view,
the bracketed terms indicating the sense of these views in medical
terminology relative to the leg,
FIGS. 12 to 17 similarly illustrate the associated tibial component
of the same embodiment, except that in this instance the plan and
inverted plan views respectively represent the superior and
inferior views, and
FIGS. 18 to 23 respectively illustrate the tibial component in
cross-sectional views taken at I--I to VI--VI.
Referring to the drawings more particularly: FIGS. 1 and 2 are
schematic views in the lateral aspect and show the femoral condyles
at 1, the tibial condyles at 2, and the lateral meniscus at 3.
These views show the joint in different phases of rotation, in
which the joint is in maximum extension and maximum flexion,
respectively, and clearly indicate the large excursion (normally of
the order of 10 mm) of the lateral meniscus and associated change
of superior form which occurs between these positions.
FIGS. 3 and 4 illustrate corresponding rotational phase views in
the medial aspect direction to indicate the corresponding, but
smaller (normally of the order of 2mm), excursion and associated
change in superior form of the medial meniscus 4.
FIG. 5 indicates these excursions in the menisci after notionally
fixing the anterior aspects of the menisci at maximum extension and
the posterior aspects at maximum flexion, with resultant gaps in
the menisci being indicated at 3a and 4a. FIG. 5 also indicates the
anterior and posterior cruciate ligaments at 5 and 6.
The femoral component of FIGS. 6 to 11 comprises a shell bearing
member 10 having two elongate portions 11 and 12 and a bridge
portion 13. The elongate portions 11 and 12 are each of generally
U-shaped form in the longitudinal direction and generally dished
form in the lateral direction to provide a major surface of overall
convex curvature. These major surfaces of the portions 11 and 12
serve as bearing surfaces to respectively replace the corresponding
function of the femoral, lateral and medial condyles. For this
purpose the portions 11 and 12 are disposed in spaced side-by-side
relation. The portions 11 and 12 are held in such relationship by
the bridge portion 13 which integrates the same in continuous
manner partway along the U-bases and one pair of corresponding
U-arms.
The pair of U-arms in question are those which represent the
anterior end portions of the femoral condylar bearing surfaces, and
the bridge portion is shaped to define a trough between the
portions 11 and 12 relative to their convex curvature. This trough
also serves as a bearing surface to replace the corresponding
function of the similar trough in the natural joint which guides
the patella and associated tendon.
In its preferred form, as illustrated, the bearing surfaces of the
shell member of the femoral component closely conform to the
natural shapings of the corresponding parts of the knee joint and
these shapings are such that the member will be normally most
conveniently produced by casting. A mould for this purpose can be
developed from a former in which the relevant surfaces are derived
by direct moulding from the femur of a natural joint.
The remaining parts of the illustrated femoral component are those
concerned with its fixation. This is intended to be by use of
acrylic resin or other gap-filling agents or cements such as used
with bone joint prostheses and, in this connection, the concave
surface areas of the elongate portions 11 and 12, and the
associated rear surface of the bridge portion 13, are formed with a
plurality of relatively short studs 14. These studs serve to space
the main body component from the cancellous bone of a suitably
prepared femur to allow flow of resin therebetween over a
sufficient area and to an adequate thickness to afford good
securement. Also, the studs enhance the securement by providing a
key between the component and the cement.
The associated tibial component of FIGS. 12 to 23 comprises a
platform bearing member 20 which also has two elongate portions 21
and 22, and a bridge portion 23. The portions 21 and 22 each have a
major surface of generally dished form in both the longitudinal and
lateral directions to provide overall concave curvature. These
major surfaces serve as bearing surfaces to respectively replace
the corresponding function of the lateral and medial menisci and
tibial condyles, and to co-operate with the convex bearing surfaces
of the illustrated femoral component. Accordingly, the portions 21
and 22 are held in spaced side-by-side relation by the bridge
portion 23 which integrates the same in continuous manner partway
therealong from one pair of corresponding ends. The corresponding
ends in question represent the anterior part of the component and
the bridge portion is shaped to define a ridge between the concave
dished surfaces, which ridge extends into the trough of the
associated femoral component when the two components are engaged in
bearing relation in a position representing maximum extension. This
position can be envisaged from the four pairs of FIGS. 8 and 14, 9
and 15, 10 and 16 and 11 and 17, which show the components in their
respective dispositions for this position, but separated in the
longitudinal direction of the relevant leg.
Also, it is to be noted that the bridge portion 23 does not depend
below the bearing surface areas of the tibial component to the same
extent as the elongate portions 21 and 22, but is relieved to
provide a cavity 24 therebelow.
Regarding fixation of the tibial component:
This also involves use of a resin or cement as used for the femoral
component, although in this instance it is preferred to afford
spacing and keying by the provision of grooves 25 over the
non-concave major surfaces of the elongate portions 21 and 22.
These grooves are preferably of dovetail cross-sectional form to
provide an enhanced key, and are also preferably aligned with both
the longitudinal and lateral directions of their respective
elongate portions to provide a "cross-hatched" effect.
In addition, a central part of each grooved area extends further
than the remainder of such area to provide a plateau 26. This has a
similar spacing function to the studs 14 of the femoral component
in ensuring an adequate layer of resin or cement below the tibial
component as well as entry of such material into the grooves.
In its preferred form, as illustrated, the bearing surfaces of the
tibial component closely conform to those of the menisci in FIG. 3
with the gaps 3a and 4a effectively reconstructed. Thus, one pair
of corresponding ends of the concave bearing surface areas
respectively closely conform to the surface shapes of the anterior
portions of the menisci of the natural joint when the joint is in a
rotational phase of relatively small flexion angle, the other pair
of corresponding ends of such areas similarly conform to the
surface shapes of the menisci when the joint is in a rotational
phase of relatively large flexion angle, and intermediate portions
of such areas conform to developments smoothly bridging said
anterior and posterior portions. As with the femoral component,
such shaping in the tibial component will be normally best achieved
by use of casting techniques. A suitable former from which the
desired shaping can be obtained has been produced from a natural
joint on which a menisectomy was first carried out, leaving all of
the ligaments intact. Then a wax was poured into the joint space
with the joint at full extension. After at least peripheral
setting, the wax was heated at the rear and side regions of the
joint, and the joint flexed to generate a fixed surface which had
the maximum effective congruence with the femoral condyles
throughout the range of flexion.
While the femoral and tibial components can be cast from moulds
produced, as described above, from formers which are directly
moulded from a natural joint, it is preferred that the bearing
surface areas of the moulds, and so of the cast components, be
idealized. Thus all undulations resulting from the presence of
cartilage should be smoothed, the indentations of the menisci on
the natural femoral condyles are not reproduced, and a mutual
lapping operation in production of the relevant moulds is effected
to provide an optimized fit. Also, it will be normally appropriate
to extend the bridge portion of the femoral component to ensure the
provision of a bearing surface for the patella in the final degrees
of extension.
Features of the final shaping which can be appreciated from the
drawings are that the condylar bearing surfaces of the femoral
component follow smooth generally spiral curves in their
longitudinal directions with increasing radius of curvature from
back to front, while the corresponding curvatures of the tibial
component are more uniform. More particularly, the components have
greater congruity at the front than the rear when engaged in
bearing relation in the position corresponding to full extension.
Indeed the components are highly congruous, both longitudinally and
laterally, in this position in their front parts and bridge
portions. This reduces stresses when standing and also assists
positioning of the tibial component relative to the femoral
component during implantation.
Also, the longitudinal directions of the elongate portions of the
femoral component, and those of the tibial component similarly,
diverge from their bridged ends by an angle of about 10.degree. -
15.degree., as do the natural condyles. This enhances
antero-posterior stability.
The invention is, of course, not intended to be limited to the form
which has been more particularly described with reference to the
drawings, but can be varied within the scope of the appendant
claims. For example, either of the femoral and tibial components
can be provided with suitably located grooves or ribbed formations,
studs, spikes, stems, or other fixation formations or members.
Indeed, in a presently proposed modification, the majority of the
studs of the femoral component are to be replaced by a pair of
intracondylar webs extending partway along the longitudinal
directions of the respective elongate portions, generally centrally
of the bridged parts thereof, while retaining one or two studs at
the other ends thereof.
Also, the components can be made in any materials suited to the
purpose, although the present preference is for a metal/plastics
material combination for the respective components. More
particularly, the present preference is that the femoral component
be of a metal such as chrome/cobalt alloy, and that the tibial
component be of a plastics material such as high density
polyethylene.
Lastly, it is useful to mention practical advantages of the device
of the invention. Since the bearing surfaces closely simulate those
of the natural joint, the former can afford a range of flexion and
extension closely approximating that of the latter. The use of
shell and platform bearing members does not involve removal of
large amounts of bone from the natural joint as is commonly the
case with hinged forms of knee joint prostheses. Also, the proposed
device need not involve the use of long intramedullary stems or
like members for the purposes of fixation, and so obviates the need
for lengthy excursions of foreign material into and along the
medullary canals. These last two points mean that the device can,
if the need arises, be removed without undue difficulty after
implantation and, more important, still afford the possibility of
alternative remedial action such as use of another form of joint
prosthesis (including a hinge device), or arthrodesis. These
possibilities are significantly reduced if large amounts of bone
are removed in an initial remedial action.
Further factors of advantage are that all of the natural ligaments,
and also the patella, can be retained.
* * * * *