U.S. patent number 3,774,244 [Application Number 05/224,479] was granted by the patent office on 1973-11-27 for knee-joint prosthesis.
This patent grant is currently assigned to New York Society for The Relief of The Ruptured and Crippled. Invention is credited to Peter S. Walker.
United States Patent |
3,774,244 |
Walker |
November 27, 1973 |
KNEE-JOINT PROSTHESIS
Abstract
A knee-joint prosthesis comprises a femoral condyle component
and a tibial condyle component secured, respectively, to the
femoral and tibial condyles by a cement in resected areas of the
bones. The femoral component is an elongated, doubly-curved member
that extends from the anterior to the posterior of the femoral
condyle and has an external surface shaped to match closely the
anatomical shape of the femoral condyle. The tibial component is an
elongated member extending from adjacent the anterior extremity to
adjacent the posterior extremity of the tibial condylar plateau and
positioned for engagement by and support of the fmoral component.
The external surface of the tibial component closely matches in
transverse cross-sections along its length the transverse shape of
the external surface of the femoral component and is generated by a
generally straight, anterior-posterior line moved along said
transverse curvature. The prosthesis may be duo-condylar, or it may
be made uni-condylar by provision of the components on only one
pair of condyles.
Inventors: |
Walker; Peter S. (New York,
NY) |
Assignee: |
New York Society for The Relief of
The Ruptured and Crippled (New York, NY)
|
Family
ID: |
22840883 |
Appl.
No.: |
05/224,479 |
Filed: |
February 8, 1972 |
Current U.S.
Class: |
623/20.3 |
Current CPC
Class: |
A61F
2/38 (20130101); A61F 2002/3895 (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
|
|
|
|
|
|
|
1,964,781 |
|
Jul 1971 |
|
DT |
|
1,047,640 |
|
Jul 1953 |
|
FR |
|
Other References
Vitallium Surgical Appliance (Catalog), Austenal Medical Div.,
Howmet Corp., New York, N.Y., 1964, page 62, M.G.H. Femoral Condyle
Replacements/No. 6662..
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Claims
I claim:
1. A knee-joint prosthesis comprising a femoral condyle component
adapted to be secured to one of the femoral condyles, and a tibial
condyle component adapted to be secured to the tibial condyle
corresponding to said femoral condyle, the femoral condyle
component being an elongated, doubly curved member shaped and
dimensioned to extend from the anterior to the posterior of the
femoral condyle and having a varying curvature in the
anterior-posterior direction closely matching the anatomical shape
of the femoral condyle and having in transverse cross-sections
along its length a laterally outwardly located essentially flat
zone and a laterally inwardly located curved zone that is
externally convex, the tibial condyle component being an elongated
member shaped and dimensioned to extend from adjacent the anterior
extremity to adjacent the posterior extremity of the
femoral-engaging surface of the tibial condylar plateau and adapted
to be positioned for engagement by and support of the femoral
component, and the tibial component having an external surface
closely matching in transverse cross-sections along its length the
transverse shape of the external surface of the femoral component
and being a surface generated by a substantially straight
anterior-posterior line moved along said transverse shape.
2. A knee-joint prosthesis according to claim 1 and further
comprising a cement bonding medium adapted to secure the femoral
and tibial components to the femoral and tibial condyles.
3. A knee-joint prosthesis according to claim 1 wherein he femoral
condyle component further includes a multiplicity of projections
extending from its internal surface and adapted to be received in a
resected area of the condyles to anchor the femoral component in
place thereon.
4. A knee-joint prosthesis according to claim 3 wherein the
projections include an elongated relatively massive main post
projecting from the internal surface of the femoral component and
positioned on the component to have its major axis in the direction
of elongation aligned generally with the line of load transfer that
obtains at the knee joint when the leg is straight.
5. A knee-joint prosthesis according to claim 4 wherein the surface
of the massive post has a multiplicity of concavities disposed in
zones generally transverse to its longitudinal axis.
6. A knee-joint prosthesis according to claim 3 wherein the
projections include a multiplicity of spaced-apart small pins.
7. A knee-joint prosthesis according to claim 1 wherein there are
two femoral condyle components positioned in spaced relation to be
secured to the lower extremity of each femoral condyle and two
tibial condyle components adapted to be secured to each tibial
condyle opposite the respective femoral components for engagement
thereby and support thereof.
8. A knee-joint prosthesis according to claim 7 wherein the two
femoral condyle components are inter-connected by a crossbar to
form a unit.
9. A knee-joint prosthesis according to claim 8 wherein the
crossbar is integral with the said condyle components and has a
curvature in the lateral direction, relative to the condyle
components generally matching the anatomical shape of and adapted
to be received in the anterior intercondylar notch of the
femur.
10. A knee-joint prosthesis according to claim 1 wherein the tibial
component has undercut grooves formed in its internal surface and
adapted to receive a cement to enhance by mechanical locking the
connection of the tibial component to the tibial condyle.
Description
BACKGROUND OF THE INVENTION
This invention relates to a knee-joint prosthesis and, in
particular, to a prosthesis that provides for replacement of the
inter-engaging surfaces of the femoral and tibial condyles by which
the weight of the body above the knee is transmitted from the femur
to the tibia.
The knee joint is the largest joint of the body and is also subject
to the greatest stresses of any joint in the body. It supports the
entire weight of the body above the knee and does so in various
relative angular positions of the femur (thighbone) and the tibia
(legbone) upon articulation of the joint. In addition to sustaining
high stresses, the knee joint must also provide freedom of
articular movement. Injury or disease of the knee joint can, of
course, be extremely painful and prevent functioning of the
joint.
At present, as far as is known to the inventor, two forms of
knee-joint prosthesis of a form generally similar to the invention
are being used. In one form, large metal and plastic components
occupying most of the surface areas of the extremities of the femur
and tibia, respectively, and shaped to match the surfaces of the
extremities are implanted. This form requires considerable
resection of the extremities of the bones and removal of the
cruciate ligaments. The removal of the cruciate ligaments can
seriously impair joint durability and function.
The other type of knee-joint prosthesis consists of femoral and
tibial components in the form of metal and plastic bands received
on the femoral and tibial condyles. The components are arcuate in
both the lengthwise and transverse directions. Substantial bone
resection is required for placement of both components, and the
matching curvatures in both the anterior-posterior and lateral
directions significantly restrict flexiblity of joint movement and
only partially duplicate natural articular function.
SUMMARY OF THE INVENTION
There is provided, in accordance with the invention, a knee-joint
prosthesis that provides partial or total replacement of the
engaging surfaces of the femoral and tibial condyles, affords
relief from pain and restores function and load-bearing capability
to the knee-joint. Although the knee-joint prosthesis of the
invention represents an appropriate appliance for correction of
various injuries and diseases of the knee joint, its use is
particularly advantageous in cases of arthritis.
The prosthesis comprises a femoral condyle component and a tibial
condyle component mounted, respectively, on the femoral and tibial
condyles in positions so that the two components match and provide
load transfer and motion capability. The femoral component includes
an elongated, doubly curved member that is secured to one of the
femoral condyles and extends from the anterior to the posterior of
the femoral condyle. It has an external surface that is shaped in
the anterior-posterior direction to match closely the anatomical
shape of the femoral condyle and has in transverse cross-sections
along its length a laterally outwardly located, essentially flat
zone and a laterally inwardly located curved zone that is
externally convex. The tibial component is an elongated member that
extends from adjacent the anterior extremity to adjacent the
posterior extremity of the tibial plateau and is secured to the
tibial condyle in a position for engagement by and support of the
femoral component of the prosthesis. The supporting or external
surface of the tibial component is shaped closely to match, in
transverse cross-sections along its length, the transverse shape of
the external surface of the femoral component and is a surface
generated by a generally straight, anterior-posterior line moved
along a line matching the external transverse shape of the femoral
component. The components are secured to the femoral and tibial
condyles by cement-like bonding medium, the condyles being resected
in the areas occupied by the components so that the components are
received with their external surfaces generally contiguous to the
anatomical surfaces of the condyles.
Preferably, the femoral component has a multiplicity of projections
extending from its internal surface to enhance the anchoring of the
component in place on the femoral condyle. Such projections may
take various forms, but an advantageous construction involves the
provision of a relatively massive, elongated main post or pin
having its longitudinal axis generally aligned with the line of
load transfer at the joint when the leg is straight and a
multiplicity of relatively small pins spaced apart from each other
and projecting only a small distance from the internal surface of
the member. The surface of the main post may have several
concavities disposed in generally transverse zones to provide a
mechanical locking between the post and a layer or zone of cement
between the post and the resected bone.
It is also advantageous to provide a mechanical interlock between
the tibial component and the tibial condyle to augment the bond
provided by the cement. A mechanical interlock may be obtained, for
example, by forming undercut grooves in the internal surface of the
tibial component. In addition, undercut grooves or oblique holes
may be cut or drilled in the bone in positions underlying the
undercut grooves in the tibial component of the prosthesis. A body
of cement received in the undercut grooves in the tibial component
and in the grooves or holes in the bone affords a strong and
durable mechanical connection between the prosthesis component and
the bone.
The knee prosthesis of the invention may be placed in either one or
both femoral-tibial condyle pairs, as may be required for a given
patient. In a duo-condylar prosthesis, which will usually be
preferred, it is desirable that the two femoral condyle components
be interconnected by a crossbar extending between them and curved
in the transverse direction to match the anatomical shape of the
anterior intercondylar notch, the crossbar holding the spacing and
a parallel relationship between the two femoral members. TThe
femoral component of a duo-condyler prosthesis is preferably of
one-piece construction and symmetrical so that it can be installed
in either the right or left knee joint. Similarly, the tibial
component for both the internal and external condyles of both left
and right joints may be identical; in other words, only one form of
tibial component need be provided, and two identical pieces used in
a duo-condylar prosthesis.
Although various materials may be used for the prosthesis, the
preferred materials are Type 316-L Stainless Steel or surgical
cobalt-chrome alloy for the femoral component and a high-molecular
weight polyethylene or other appropriate high-molecular weight
plastic for the tibial component. The femoral component should have
a highly-polished surface to reduce friction to a minimum and
provide minimum wear and thus long useful life.
A knee-joint prosthesis, in accordance with the invention, provides
various significant advantages. For one thing, only the
load-bearing surfaces of the joint are replaced, and the remainder
of the joint is left intact. For example, the collateral and
cruciate ligaments are not disturbed and afford retention of joint
stability. There is a minimum of resection of the bone for
placement of the prosthesis. Accordingly, in the event of failure
of the prosthesis, which, though unlikely, is possible, there is
still adequate bone available for another procedure. The areas of
the load-bearing surfaces of the femoral and tibial components
closely match those that exist in a natural joint. As already
mentioned, it is appropriate to provide symmetry with respect to
either the internal or external condyles, which means that one form
of femoral component and one form of tibial component can be used
in either left or right knee joints, or in either internal or
external condyles of one knee joint in the case of a uni-condylar
placement. (It is evident, of course, that various sizes of the
components will be required to accommodate various sizes of joints
for different patients.) The prosthesis components are securely
fixed to the bones and are of strong, durable and long-wearing
construction. The flatness in the anterior-posterior direction of
the external or supporting surfaces of the tibial component permits
anatomical movement of the femur on the tibia while the curvatures
and orientations of the curvatures of the components limit
rotational and lateral laxity. The result is a prosthesis that
closely duplicates natural function.
DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, reference may be made
to the following description of an exemplary embodiment, taken in
conjunction with the figures of the accompanying drawings, in
which:
FIG. 1 is an anterior view of a right knee joint having an
embodiment of the knee prosthesis of the invention in place, the
extremities of the femur and tibia being shown in
cross-section;
FIG. 2 is a lateral view of the right knee joint, the view also
showing the bone extremities in cross-section, with the
cross-section taken at the outside edge of the prosthesis on the
external side of the joint;
FIG. 3 is a pictorial view of the femoral component, viewing it
from generally above, anteriorly of, and laterally inward of the
component, as it would be positioned in the joint;
FIG. 4 is a pictorial view of the femoral component, the view being
taken from generally below, posteriorally of, and laterally outward
of the component, as it would be installed in a right knee
joint;
FIG. 5 is a pictorial view of the tibial component, viewed from
above, in front of, and laterally inwardly of a component placed at
the internal condyle of a right knee joint; and
FIG. 6 is a pictorial view of the tibial component viewed from a
posterior position, below and laterally inwardly of a tibial
component in the internal position of a right knee joint.
The relative orientations of FIGS. 3 to 6 may be further understood
by comparing them with FIGS. 1 and 2.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
Referring to FIGS. 1 and 2 of the drawings, the reference numerals
10 and 12 designate generally the femur (thighbone) and the tibia
(legbone) of a human leg. Only the lower end of the femur and the
upper end of the tibia are shown in the figures. Although the
drawings illustrate the general outline of the portions of the
femur and the tibia at the knee joint, the details of the bone
shapes are not illustrated. Reference may be made to various
appropriate standard references for descriptions and illustrations
of the anatomy of a knee joint. For purposes of general
orientation, reference numerals 14 and 16 designate, respectively,
the external condyle and internal condyle of the right femur,
reference numerals 15 and 17 designate, respectively, the exterior
and interior tibial condyles, reference numeral 20 is applied to
the lateral ligaments, and reference numeral 22 is applied to the
cruciate ligaments. In FIG. 2 of the drawings, the anterior of the
joint is to the right and the posterior is to the left.
The embodiment shown in the drawings is of the duo-condylar form.
The femoral piece of the prosthesis (see FIGS. 3 and 4), which is
designated generally by the reference numeral 30, is composed of a
pair of spaced-apart, doubly curved femoral condyle components 32
and 34 interconnected by a crossbar 36. The components 32 and 34
are of identical shape, but are reversed in orientation so that the
piece is symmetrical about a vertical, anterior-posterior bisector
plane. In transverse cross-sections along its length, each
component 32 and 34 is generally flat along a laterally outward
zone (relative to the center of the joint) and is externally
convexly curved in a laterally inward zone. Viewed from the side,
each member 32 and 34 is of varying curvature, wwith a relatively
flat curvature along the anterior and bottom portions and a greater
curvature in the posterior portion. The lateral profile of the
femoral component thus conforms rather closely to the anatomical
shape of the femoral condyles, which means that it may be placed
with a minimum resection of the bone. Moreover, it provides
articulation of the joint in a manner closely resembling the
anatomical joint. The major axes or planes of the members 32 and 34
are parallel to each other and parallelism and proper spacing as
placed are assured by the crosspiece 36.
As may be seen in FIGS. 1 and 2 of the drawings, the femoral piece
is shaped and dimensioned such that the members 32 and 34 occupy
the tibial-engaging surfaces of the femoral condyles, in other
words, the areas of the femoral condyles that engage and are
supported by the tibial plateaus in the anatomical joint. The
condyle components 32 and 34 are spaced apart so that there is no
interference between the femoral piece and the cruciate
ligaments.
The crosspiece 36 is curved to present outwardly concave and
inwardly convex surfaces, the curvature generally matching the
intercondylar notch between the femoral condyles so that the
crosspiece 36 is recessed into the intercondylar notch, such that
it does not materially affect the action of the patella when the
joint is in a flexed position.
Each of the condyle ccomponents 32 and 34 of the femoral piece 30
has a relatively massive, elongated post or pin 40 projecting from
its internal surface and positioned and oriented so that its
longitudinal axis is generally coincident with the line of load
transfer from the femur to the tibia with the leg in its normal
straight or standing position. The surface of the post 40 is formed
with several shallow concavities 42 located in zones oriented
transversely of the longitudinal axis of the post. A number of
small pins 43, say 1/16 inch in diameter and 1/16 inch high,
project from the internal surfaces of the components 32 and 34 at
appropriate spacing.
For strength and durability, it is best for the femoral piece 30 to
be made of metal, such as Type 316-L Stainless Steel or surgical
colbalt-chrome alloy. The external surfaces of the components 32
and 34 should be highly polished to ensure low friction and minimum
wear.
The femoral piece is placed in the joint by resecting small amounts
of bone in the regions that will underlie the condyle components 32
and 34 so that the external surfaces of the components 32 and 34
will be generally contiguous to the anatomical surfaces of the
femoral condyles. In addition, a hole 44 is formed to receive the
post 40, and holes 46 and 48 are also formed near the posterior and
anterior extremities of the components 32 and 34 and extending
generally perpendicular to the surface of the condyles at these
points (see FIG. 2). The component is secured to the bone by an
appropriate cement, such as polymethyl methacrylate. A layer of
cement is applied at the interface between the internal surfaces of
the components 32 and 34, and bodies of cement are packed in the
holes 46 and 48 at the extremities of the components as well as in
the hole 44 that receives the post 40. The cement in the holes 46
and 48 and around the post locks the femoral piece securely in
place on the femur.
A duo-condylar prosthesis has two identical tibial condyle
components 50, one for each tibial condyle, mounted in reverse
orientation, laterally, on the respective medial and lateral tibial
condyles. Each tibial component is generally rectangular in plan,
although (as shown) it has rounded corners 51 that are located near
the respective lateral extremities of the tibial plateau, when the
component is in place. Each tibial component is mounted with its
longer axis oriented in the anterior-posterior direction in the
joint. The bottom surface 52 and the interiorly located side
surface 54 of each component are generally flat. The upper surface
56 is a surface generated by moving a substantially straight line
along a curve that matches the curve of the external surface of the
femoral condyle component 32 (or 34) of the femoral piece. An
undercut groove 58 is formed in the longitudinal direction along
the center of the bottom of the tibial component, and two spaced
apart, similarly undercut grooves 59 extend generally laterally
across the bottom. The bone at the tibial plateau is resected to
receive the respective tibial components so that their upper
surfaces are generally contiguous to the anatomical surfaces of the
tibial plateau. Holes 60 are drilled into the tibia in positions
generally underlying the groove 56 near each end of each component,
the holes being oblique to the bottom surface of the component. The
tibial components are secured to the tibia by cement, bodies of
cement extending into the undercut grooves 58 and 59 in the
component and the holes 60 in the bone and providing cement keys to
enhance the securing of the components in place.
In use, the flatness of the tibial components in the
anterior-posterior direction allows relatively free sliding and
rolling of the femoral component on the tibial component in a
manner resembling the function of the anatomical joint. The
transverse curvatures of the respective tibial components and the
matching of the cross-sectional shapes of the tibial and femoral
components in the areas in engagement limits rotation and lateral
laxity in the joint. The tibial components provided relatively
large surface areas for seating on the tibial plateau to ensure
strength and durability in the joint and to provide a substantial
load-bearing area, but these features are achieved without any
undesirable restriction in the freedom of articulation.
The above-described embodiment of the invention is intended to be
merely exemplary, and numerous variations and modifications may be
made by those skilled in the art without departing from the spirit
and scope of the invention. All such variations and modifications
are intended to be included within the scope of the invention as
defined in the appended claims.
* * * * *