U.S. patent number 3,924,277 [Application Number 05/447,993] was granted by the patent office on 1975-12-09 for knee joint prosthesis.
This patent grant is currently assigned to National Research Development Corporation. Invention is credited to Michael Alexander Reykers Freeman, Sydney Alan Vasey Swanson.
United States Patent |
3,924,277 |
Freeman , et al. |
December 9, 1975 |
Knee joint prosthesis
Abstract
A prosthetic knee joint device of `hingeless` form having
femoral and tibial components held in mutual sliding and rolling
bearing engagement by natural muscle and ligaments. The femoral
component includes a generally U-shaped channel member having an
outer surface with a generally convex curvature in the
circumferential sense relative to the channel longitudinal axial
direction, and a smooth form with a single curvature in the axial
sense. This single curvature need not necessarily be convex. The
tibial component includes a platform member having one of its major
surfaces concavely dished in generally complementary manner to at
least the convex curvature of the femoral component. The inner
surface and the other major surface of channel and platform members
are adapted for fixation with cement to the femur and tibia.
Inventors: |
Freeman; Michael Alexander
Reykers (London, EN), Swanson; Sydney Alan Vasey
(Carshalton, EN) |
Assignee: |
National Research Development
Corporation (London, EN)
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Family
ID: |
27256908 |
Appl.
No.: |
05/447,993 |
Filed: |
March 4, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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247873 |
Apr 26, 1972 |
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Foreign Application Priority Data
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May 4, 1971 [UK] |
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12919/71 |
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Current U.S.
Class: |
623/20.21 |
Current CPC
Class: |
A61F
2/38 (20130101) |
Current International
Class: |
A61F
2/38 (20060101); A61F 001/24 () |
Field of
Search: |
;3/1,1.9-1.913
;128/92C,92CA,92R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,047,640 |
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Jul 1953 |
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FR |
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1,122,634 |
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May 1956 |
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FR |
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923,383 |
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Feb 1955 |
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DT |
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Other References
Vitallium Surgical Appliances (catalog), Austenal Co., Howmet
Corp., New York, N.Y., 1964, p. 62, Femoralcondule Replacement (No.
6662) relied upon..
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Primary Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Parent Case Text
This application is a continuation of our copending application
Ser. No. 247,873, filed Apr. 26, 1972, which was abandoned upon the
assigning of a serial number to the present application.
Claims
We claim:
1. A prosthetic knee joint device comprising: a femoral bearing
member of generally U-shaped form having a first side wall, a base,
and a second side wall, defining relative to said U-shape a major
outer surface and a major inner surface, said outer surface having
a convex first profile extending in a circumferential direction
around said U-shape and including a convexly curved first profile
part extending over said first wall and partway across said base, a
rectilinear second profile part continuing across said base from
said first profile part, and a convexly curved third profile part
continuing across said second wall from said second profile
part;
and a tibial bearing member in the form of a platform having a
major upper surface and a major lower surface, said upper surface
being dished in one direction thereacross to provide a concave
second profile generally complementary to said convex first
profile, said concave second profile including a concavely curved
central profile part of the same order of curvature as and in
mutual articulatory bearing engagement with said first profile
part, and a rectilinear outer profile part continuing from said
central profile part in similar angular relationship therewith to
that between said femoral first and second profile parts, said
femoral second and tibial outer profile parts engaging to limit
said articulatory engagement.
2. A device according to claim 1 wherein said first and central
profile parts are both curved in circular arcuate manner with the
same radius of curvature.
3. A device according to claim 2 wherein said third profile part is
curved in circular arcuate manner with a lesser radius of curvature
than said first profile part.
4. A device according to claim 1 wherein said concave second
profile comprises a further rectilinear outer part continuing from
said central profile part in similar manner to and symmetrical
relationship with the first-mentioned rectilinear outer profile
part.
5. A device according to claim 1 wherein said outer surface is
formed with a first groove extending across said second wall in
said circumferential direction.
6. A device according to claim 1 wherein said first wall extends
further from said base in said circumferential direction than said
second wall.
7. A device according to claim 1 wherein said first side wall is of
greater extent in a direction orthogonal to said circumferential
direction than said second wall, and said base is symmetrically
convergent between said differing first and second side wall
extents.
8. A device according to claim 1 wherein said outer surface is
formed with a second groove extending across said first wall and
partway across said base in said circumferential direction, and
said platform member is provided with a peg upstanding from said
upper surface and slidably engaged in said second groove.
9. A device according to claim 1 wherein said femoral bearing
member is slotted therethrough in said circumferential direction
wholly across said first side wall and partway across said base,
and said platform member is correspondingly slotted partway
thereacross from its periphery.
10. A device according to claim 1 wherein said femoral bearing
member is adapted for fixation to the femur by the provision of an
intramedullary stem upstanding from said inner surface across said
base to an extent intermediate that of said first and second side
walls.
11. A device according to claim 1 wherein said femoral bearing
member is adapted for fixation to the femur by the provision of
inturned portions around at least part of the periphery thereof
communicating said inner and outer surfaces.
12. A device according to claim 1 wherein said tibial bearing
member is adapted for fixation to the tibia by the provision of a
subsidiary platform extending from said lower surface, which
subsidiary platform has undercut edges.
13. A device according to claim 1 wherein said femoral bearing
member is symmetrical about a first plane wholly including said
U-shaping, and said tibial bearing component is symmetrical about
both said first plane and a second plane which is mutually
orthogonal with said first plane and said upper and lower
surfaces.
14. A prosthetic knee joint device comprising: a femoral bearing
member of generally U-shaped form having a first side wall, a base,
and a second side wall, defining relative to said U-shape a major
outer surface and a major inner surface, said outer surface having
a convex first profile extending in a circumferential direction
around said U-shape and including a convexly curved first profile
part extending over said first wall and partway across said base, a
relatively flat second profile part continuing across said base
from said first profile part, and a convexly curved third profile
part continuing across said second wall from said second profile
part;
and a tibial bearing member in the form of a platform having a
major upper surface and a major lower surface, said upper surface
being dished in one direction thereacross to provide a concave
second profile generally complementary to said convex first
profile, said concave second profile including a concavely curved
central profile part of the same order of curvature as and in
mutual articulatory bearing engagement with said first profile
part, and a relatively flat outer profile part continuing from said
central profile part in similar angular relationship therewith to
that between said femoral first and second profile parts, said
femoral second and tibial outer profile parts engaging to limit
said articulatory engagement.
15. A device according to claim 14 wherein said concave second
profile comprises a further relatively flat outer part continuing
from said central profile part in similar manner to and symmetrical
relationship with the first-mentioned relatively flat outer profile
part.
16. A device according to claim 14 wherein said first and central
profile parts are both curved in circular arcuate manner with the
same radius of curvature.
17. A device according to claim 14 wherein said outer surface is
formed with a first groove extending across said second wall in
said circumferential direction.
18. A device according to claim 14 wherein said first wall extends
further from said base in said circumferential direction than said
second wall.
19. A device according to claim 14 wherein said first side wall is
of greater extent in a direction orthogonal to said circumferential
direction than said second wall, and said base is symmetrically
convergent between said differing first and second side wall
extents.
20. A device according to claim 14 wherein said outer surface is
formed with a second groove extending across said first wall and
partway across said base in said circumferential direction, and
said platform member is provided with a peg upstanding from said
upper surface and slidably engaged in said second groove.
21. A device according to claim 14 wherein said femoral bearing
member is slotted therethrough in said circumferential direction
wholly across said first side wall and partway across said base,
and said platform member is correspondingly slotted partway
thereacross from its periphery.
22. A device according to claim 14 wherein said femoral bearing
member is adapted for fixation to the femur by the provision of an
intramedullary stem upstanding from said inner surface across said
base to an extent intermediate that of said first and second side
walls.
23. A device according to claim 14 wherein said femoral bearing
member is adapted for fixation to the femur by the provision of
inturned portions around at least part of the periphery thereof
communicating said inner and outer surfaces.
24. A device according to claim 14 wherein said tibial bearing
member is adapted for fixation to the tibia by the provision of a
subsidiary platform extending from said lower surface, which
subsidiary platform has undercut edges.
25. A device according to claim 14 wherein said femoral bearing
member is symmetrical about a first plane wholly including said
U-shaping, and said tibial bearing component is symmetrical about
both said first plane and a second plane which is mutually
orthogonal with said first plane and said upper and lower surfaces.
Description
Various proposals have been made for knee joint prostheses in the
past, but none of these appears to have proved generally
satisfactory. Among the disadvantageous features found to arise
with these prior proposals are the need to remove a relatively
large amount of bone in the region of the natural joint together
with, in many instances, removal of the patella and the natural
ligaments, and the need to implant foreign matter for a relatively
long distance along the medullary canals. These features in fact
commonly arise with proposals for the use of prosthetic devices of
mechanically coupled hinge form, and such devices normally bring
their own disadvantage in the form of a requirement for the surgeon
to assemble the hinge during implantation.
It is usual in any case, whether the device be of hinged form or
not, for a knee joint prosthesis to be non-symmetrical so that
different versions are required as between the left and right
knees.
An object of the present invention is to provide an improved
prosthesis which affords a reduction in the above
disadvantages.
To this end there is provided a knee joint prosthetic device
comprising a femoral component including a generally U-shaped
channel member in which at least that part of the outer surface
extending over one side wall of said channel member, and continuing
partway across the base of said channel member, is of a form having
a generally convex curvature in the circumferential direction
relative to the longitudinal axis of said channel member, and of a
form having a single sense of curvature, which is not necessarily
convex, in the axial direction relative to said channel member; and
a tibial component including a platform member having one of its
major surfaces concavely dished in a form generally complementary
to at least said form having generally convex curvature of said
channel member for mutual sliding and rolling engagement therewith;
and wherein the inner surface and other major surface of said
members are respectively adapted for cement fixation to the femur
and tibia.
In this connection it is to be noted that a U-shaped channel is
regarded as having a base and two side walls to define the
U-shaping, and that such a channel has a longitudinal or axial
direction running along the base and spaced between the side walls,
and also a circumferential direction which is that passing
successively across one side wall, the base, and the other side
wall, in a sense to wrap around the longitudinal axial direction.
For clarity, these directions are indicated in FIGS. 1 and 3 of the
drawings described hereinafter.
In practice the channel and platform members serve the respective
roles of the femoral condyles on the one hand and the tibial
condyles and menisci on the other hand, with said one channel side
wall representing the posterior aspect, and are held in engagement
by the relevant muscles and collateral ligaments. It will be
appreciated then that the presently proposed prosthesis is of
hingeless form and this serves to reduce the possibility of
undesired and large moments which, it is considered, can cause
loosening of the prosthesis fixation. The more particular
requirements of curvature expressed above also serve, in this
connection, to reduce the possibility of undesirable torsional
moments which can otherwise arise if an attempt is made to
eliminate torsional movement.
In any event the present invention allows the prosthesis to be more
compact than is the case with the use of a hinge device, with a
consequent reduction in the requirement for removal of bone, and
this advantage is enhanced by an associated reduction in the
required intramedullary or other penetration for the purposes of
fixation. At the same time, the proposed curvature for the mutual
bearing surfaces is such that the components can bear over an area
which is large enough to ensure, so far as is practicable, a rate
of production of wear particles or solutes that will be
biologically innocuous. Also, the proposed curvature for the mutual
bearing surfaces and the absence of long intramedullary or other
stems for fixation are such that both components can be symmetrical
about a plane transverse to the lateral aspect, which plane is
radial relative to the longitudinal axis of the channel member.
This symmetry means that the usual requirement to produce
differently handed components for the left and right knees is
avoided.
The mutual bearing surfaces of the components are, of course, of
generally rounded form in the lateral aspect. However, in a
preferred form the bearing surface of the femoral component has a
first lateral profile part around the posterior side wall and an
adjacent portion of the channel base, which profile part is
continuously curved, suitably in circular arcuate manner, while a
second lateral profile part extends from the first such part across
the remainder of the base in substantially rectilinear manner. The
bearing surface of the tibial component intended for use with the
above surface preferably has a central lateral profile part curved
to conform with the first profile part of the femoral component,
and extends into outer lateral profile parts of which at least one
is substantially rectilinear. These profile parts co-operate so
that the first part of the femoral component engages the central
part of the tibial component during flexion and extension, and
extension will be limited by engagement of the second part of the
former component with the corresponding rectilinear outer part of
the latter component. In fact it is preferred that this last
engagement does not normally occur during walking, but that such
engagement, together with natural muscular control limitations,
provides stability with a small and limited amount of
hyperextension. This can be achieved by orientating the relevant
rectilinear profile parts relative to their respective curved
profile parts so that the rectilinear parts are mutually divergent
at a small angle when the curved parts are engaged in the position
of zero flexion.
Conveniently, both of the lateral profile edge parts of the tibial
component are of like substantially rectilinear form so that this
component is also symmetrical in the lateral aspect, that is to
say, symmetrical about the axial plane which is mutually orthogonal
with the above-mentioned radial plane and passes between the side
walls of the channel member. This avoids any difficulty which may
otherwise arise in determining the anteroposterior disposition.
The bearing surface portions having the lateral profile parts
discussed above are, in a presently preferred form of the
invention, substantially rectilinear in the antero-posterior
aspects, that is to say, rectilinear in the axial direction of the
channel member.
The remaining third lateral profile part of the femoral component
around the anterior side wall is also preferably curved, suitably
to circular arcuate form having a higher degree of curvature than
the first such part. This third part does not, in fact, bear on the
tibial component, but a curved form is appropriate to its
engagement with adjacent tissue and other relatively soft matter.
However, the surface portion of the tibial component having this
third lateral profile part can also bear on the patella, if
retained, and for this purpose such portion is preferably grooved
centrally and in a vertical sense to retain the handed symmetry of
the component. This grooving suitably has a circular arcuate
sectional profile of intermediate degree of curvature between that
of the first and third lateral profile parts.
It is also to be noted that the anterior side wall need not extend
as far above the channel base as the posterior side wall.
Regarding fixation: the channel member is inherently shaped to
assist fixation on a suitably sectioned femur and can be adapted to
intramedullary fixation by way of a stem extending from the base
portion and spaced between the side walls of the relevant major
surface. This stem can be relatively short in length and need not
extend beyond the posterior side wall. The platform member is
preferably adapted for cement fixation by way of a subsidiary
platform depending therebelow and which has undercut edges, or by
way of ribs or studs formed on its lower surface, or by way of an
equivalent relatively shallow formation providing a good key.
Fixation of the tibial component can also involve the use of a
stable having one arm driven into the lower part of the component,
suitably in the anterior aspect, and the other arm into the tibia
therebelow.
Lastly among the more general and preferred features of the present
invention: the anterior wall of the femoral component can extend
axially along the channel member to a lesser extent than the
posterior wall, and the base is then of suitably symmetrical
divergent form from the former to latter wall; the various bearing
surface parts preferably join without forming discontinuties and so
provide generally smooth overall surfaces; and all of the external
angles are generally rounded.
In order that the above and other features may be better understood
the same will now be described, by way of example, with reference
to embodiments of the invention as illustrated in the accompanying
drawings, in which:
FIGS. 1, 2 and 3 respectively show the femoral component of a
presently preferred embodiment in side, front and plan views
(lateral, anterior and superior aspects),
FIGS. 4 and 5 show sectional detail taken at IV--IV and V--V in
FIG. 3,
FIGS. 6 and 7 respectively show the associated tibial component of
the presently preferred embodiment in side and underneath views
(lateral and inferior aspects), and
FIGS. 8 to 11 illustrate modifications of the presently preferred
embodiment.
Considering the illustrated femoral component of FIGS. 1 to 5: this
comprises a generally U-shaped channel member 1 with a base 2, a
higher anterior side wall 3, a lower posterior side wall 4, and a
step 5 extending upwardly from the base between the side walls to
an intermediate height therebetween. The channel member 1 has a
major outer surface and a major inner surface, which surfaces are
respectively represented in lateral profile by the outermost and
innermost U-shaped boundaries of the member (minus the stem 5) as
seen in FIG. 1. FIG. 1 further shows the major outer surface to
have a generally convex first profile which is constituted by a
succession of a first convexly curved first profile part, a
rectilinear second profile part, and a convexly curved third
profile part. More specifically in FIG. 1 these successive profile
parts are respectively shown and identified as a first circular
arcuate part 6 extending around the wall 3 and across the base 2 to
approximately the centre of the latter; a second substantially
rectilinear part 7 extending smoothly from the part 6 to below the
wall 4; and a third circular arcuate part 8 extending around the
wall 4. The curvature of profile part 6 is lower than that of part
8, and has its centre of curvature located to afford stability at
or about zero flexion.
In the superior aspect, the wall 4 is seen to be grooved vertically
at 9, the groove having a circular arcuate section of greater
curvature than profile part 6 but less than part 8. Also, this
aspect shows the wall 4 to extend less in the longitudinal axial
direction of the channel member than the wall 3, and that the base
diverges symmetrically from the former to the latter.
The stem 5 is of circular cross-sectional shape and is slightly
tapered towards its free end.
It is also seen from the anterior and superior aspects that the
femoral component is symmetrical about a plane which is radial
relative to the longitudinal axis of the channel member.
Turning to the tibial component of FIGS. 6 and 7: this comprises a
platform member 10 having a major upper surface and a major lower
surface, which surfaces are respectively represented in lateral
profile by the uppermost and lowermost boundaries of the platform
member as seen in FIG. 6. FIG. 6 further shows the major upper
surface to have a generally convex second profile which is
constituted by a succession of a rectilinear outer profile part 12,
a concavely curved central profile part 11, and a further
rectilinear outer profile part 12. More specifically, the central
profile part 11 is of circular arcuate form equal in curvature to
the femoral first profile part 6 mentioned above, and the outer
profile parts 12 extend smoothly from the central profile part
11.
It is to be noted that, in the lateral aspects of the two
components, the second profile 7 is inclined at a greater angle to
the horizontal than the edge profile parts 12 when the components
are disposed for zero flexion. The difference of angle here is in
fact small relative to the overall angular range of movement
between maximum flexion and extension.
A subsidiary platform 13 with undercut edges 14 depends from the
other major surface of the platform 10.
It will be seen that, when the two components are disposed for zero
flexion, the tibial component is symmetrical about the
above-mentioned radial plane and the mutually orthogonal axial
plane which passes between the side walls of the channel
member.
While the embodiment as so far described is presently preferred, it
is not intended that this should limit the scope of the invention.
This will be clear from the introductory discussion of the
invention, and variations from the preferred embodiment are
possible and may be advantageous in the light of further study. For
example, it may be considered that the femoral component should be
fixed by way of a longer intrameduallary stem, but this will
normally involve angling the stem with a consequent need for handed
components. The tibial component can be fixed by way of an
intramedullary stem, and this also may be of longer angled form.
Also, the patella reception groove may be off-set from the
presently preferred symmetrical disposition, or it may pass further
across the channel base.
A further possible variation is that the mutual bearing surfaces of
the femoral and tibial components be rounded in complementary
manner in the antero-posterior aspects, that is in the axial
direction, to assist in lateral stability. Normally such rounding
will involve respectively convex and concave lateral curvatures for
the femoral and tibial component bearing surfaces as illustrated in
FIG. 8, but these curvatures can equally well be interchanged.
As one alternative to the preceding variation, lateral stability
can be enhanced by the provision of a peg 20 projecting upwardly
from the tibial component to engage a groove 21 formed centrally
along the bearing surface of the femoral component at least between
the positions of full flexion and extension, as illustrated by FIG.
9.
In yet another alternative, the possibility of enhancing lateral
stability is provided by allowing for retention of the cruciate
ligaments. In this case, both the femoral and tibial components are
respectively centrally slotted partway thereacross from their
posterior peripheral edges. These slots should extend sufficiently
to clear the cruciate ligaments in the position of full extension,
as shown in FIGS. 10 and 11 in which the femoral and tibial
component slots are respectively denoted at 22 and 23. The tibial
component of FIG. 11 is also modified by the provision of two
subsidiary platforms 13 on opposite sides of the slot 23.
Lastly the question of materials should be mentioned. The present
preference is for the femoral component to be made of appropriate
cobalt-chromium alloy and the tibial component to be made of high
density polyethylene, although there may be advantage in
interchanging these component materials. However, other materials
also appear suitable, such as stainless steel and titanium alloys
of appropriate forms. Moreover, the use of a metal other than a
cobalt-chromium alloy, which alloys are difficult to work in the
forms suited to prosthetic devices, may allow the use of simpler
working techniques. For example, it may be practicable to form the
femoral component by bending from plate, followed by grinding and
polishing, with fixation being afforded by the provision of
inturned peripheral portions as shown at 24 in FIG. 10.
* * * * *