Note: Descriptions are shown in the official language in which they were submitted.
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PROSTHETIC MENISCUS FOR THE REPAIR OF JOINTS
~ This application is related to the inventor's
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~copending applications serial numbers 431,151 and 431,152
both filed 3une 24, 1983.
Technïcal Field
The present invention relates to
prosthetic devices for repairing damaged joints in
animals and humans, and more particularly relates
to a prosthetic substitute for the natural meniscus
or cartilage found in such joints.
Background Ar~
The general function of the meniscus or
cartilage which separates the bones of the joint is
to cushion and lubricate the joint. When the
lS natural meniscus is damaged as the result of
traumatic injury or deterioration, the natural
meniscus is often removed surgically. In the
absence of the meniscus,~the bones of the joint are
not properly positioned, cushioned or lubricated.
Therefore stresses arise in the operation of the
joint, the range of motion and flexibilîty of the
joint can be restric~ed, and arthritis commonly
develops in the jvint.
In response to the problems which arise
from the mere removal of the natural meniscus,
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total joint replacements have been proposed. As
shown in U.S. Patents No. 4,0B5,446; 4,224,696 and
4,224,697, such prosthetic joints generally inc}ude
replacement of the articular surfaces of the bones
as well as provision of a mechanical joint or other
interface between the artiEicial articular
surfaces. Such total joint replacements are
- subject to failure of the components or weakening
of the bond between the bone and the implanted
articular surfaces, and experience has shown that
20-30% of such replacements are ultimately
unsuccessful. Furthermore, attempts to provide
complete natural movement of joints such as the
knee have led to the development of highly complex
artificial joints.
U.S. Patent 4,085,466 also suggests that
a meniscal component can be made from a resilient
plastic material and inserted alone between the
natural femoral and tibial articular surfaces. It
is further suggested that differential resilience
be achieved in such an insert by making the insert
in the shape of a disc and wrapping a sock of nylon
or other synthetic fiber around the circumferential
surface of the disc. However, no means is
suggested for holding the disc in place within the
joint.
Thus, there is a need in the art for a
successful manner in which to avoid the problems of
cartilage removal without resort to the complexity
and post-operative complications of total joint
replacement.
Summary of the Invention
The present invention fills an important
need in the art by providing a novel prosthesis
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designed to replace or augment the natural meniscus
or cartilage and to bear against the natural
articular surfaces of the bones of the joint.
Generally described, a prosthesis embodying the
present invention comprises a resilient insert
shaped to be received within the joint to provide
at least substantially the same area of bearing
surface as the natural meniscus, and reinforcing
means embedded within the insert. The prosthetic
meniscus of the present invention preferably
further comprises an extra-articular extension of
the reinforcing material, either alone or embedded
in the resilient material J and means for attaching
the extension to an exterior bone surface outside
the joint so as to permit relative movement between
the insert and the extension. Portions of the
reinforcing material can extend outwardly from the
exterior of the insert within the joint for
attachment of the insert to ligaments which
encapsulate the joint.
The resilient insert is preferably shaped
to match the form of the natural meniscus, and is
preferably constructed of a resilient plastic
material such as silicone rubber, or
polytetrafluoroethylene. However, ~ natural
materials such as rubber might be appropriate for
some joints. The reinforcing material preferably
comprises a tightly woven mesh of strainless steel
or nylon strands. The~extra-articular extension
can be protected with a stainless steel cover and
attached to the bone surface outside the joint by
means of screws passing through the cover and the
extension. The reinforcing mesh strengthens the
meniscal insert, helps to maintain the basic shape
of the insert while permitting a degree of
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resilient deformation thereof, prevents tearing of
the insert, and provides a strong bond between the
intra-articular insert and its extra articular
extension which is attached to the bone.
A prosthetic meniscus e!mbodying the
present invention is intended to be constructed in
various shapes to replace the natura] meniscus of
any joint~ including but not limited to, the knee,
hip, elbow, shoulder, jaw, fingers and even the
spine. Such a prosthetic meniscus can be used in
the natural joint or a prosthetic partial or total
replacement of the joint; it can also be used to
augment the natural meniscus if the latter need not
be removed.
~5 Thus, the present invention seeks to provide a
novel prosthetic meniscus for ~eplacement of the natural '~
meniscus of a joint.
~Further, the pres~nt invention seeks to
provide a prosthetic meniscus capable of
replacing a natural m~Riscus without affecting
the extent and types of movement of the joint, and
capable of providing the cushioning and lubricating
functions of a natural meniscus.
Still further,- the pres`ent invention
seeks to provide a prosthetic menis~us that can
be inserted into a joint for cooperation with the
natural articular surfaces of the Lones of the
jointO
~t is a still further aspect of the present
invention to provide a prosthe~tic meniscus for
insertion into a joint, the position of the
meniscus being maintained to prévent undesirable
dislocation o~ the meniscus during articulation of
the joint.
Other aSpects~ features and advantages of
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the present invention will become apparent upon
reading the following detailed description of
emb,odiments oE the invention, when taken in
conjunction with the drawing and the appended
claims.
Brie Description of the Drawing
Fig. 1 is a pictorial view of a
prosthetic meniscus embodying the present invention
for use in the lateral position of a knee joint.
Fig. 2 is a pictorial illustration of a
prosthetic meniscus embodying the present i~vention
for use in the medial portion of a knee joint.
Fig. 3 is a pictorial illustration of a
prosthetic meniscus of the type shown in Fig. 1,
showing an alternate embodiment wherein the
extra-articular extension is formed of only the
reinforcing material.
2 Fig, 4 is a bottom plan view of a
prosthetic meniscus of the type shown in Fig. 1,
including projections of the reinforcing material
outside the prosthetic meniscus for attachment to
adjacent ligaments, soft ~issues, or both.
Fig. 5 is a lateral plan view of a knee
joint fitted Wit~h a prosthetic meniscus e~bodying
the present invention.
Fig. 6 is a medial view of the knee joint
of Fig. 5.
Fig. 7 is a rear view of the knee joint
of Figs. 5 and 6, showing some ligaments.
Fig. 8 is a top plan view of the tibial
portion of the knee joint of Fig. 5~7~ the femur
being removed to expose interior detail.
Fig. 9 is a pictorial illustration of a
prosthetic meniscus embodying the present invention
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for use in a hip joint.
Fig. 10 is a front plan view of a hip
joint fitted with a prosthetic meniscus of the type
shown in Fig. 9.
Fig. 11 is a pictorial illustration of a
prosthetic meniscus embodying the present invention
for use in the temporo-mandibular joint, appearing with Figs.
Fig. 12 is a side plan view of a
temporo-mandibular joint fitted with a prosthetic
meniscus of the type shown in Fig. 11.
Detailed Description
Referring now in more detail to the
drawing, in which like numerals represent like
parts throughout the several views, Figs. 1, 2 and
5-8 show an embodiment of a prosthetic meniscus
according to the invention mounted in a knee joint.
Since a knee joint has two menisci two prosthetic
menisci embodying the invention are also provided.
Fig. 1 shows a lateral prosthetic meniscus 10
embodying the invention, including an
intra-articular body or insert portion 11 formed of
a resilient material and shaped to match the shape
; 25 of the natural meniscus that it replaces. The
meniscus 10 further defines an extra-articular
extension or strut 12 designed to extend outside of
the joint for attachment to the surface of the
demur. Embedded within the body 11 and strut 12 of
the meniscus 10 is a continuous reinforcing
material 14. The resilient material of the
meniscus 10 can comprise one o-f several materials
having somewhat differing characteristics. Silicone
rubber having a slick surface is sufficiently
3 resilient and movable with respect to the articular
surfaces of the bone to provide the desired
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cushioning and lubricating functions. Silastic
material is one suitable brand~of silicone rubber.
Polytetrafluoroethylene (Teflo~) can be deformed
to a lesser degree than the ~aterials previously
mentioned, but has good lubricative qualities and
is suitable where the natural meniscus is thin such
as in the temporo-mandibular joint of the jaw.
Other materials exhibiting some degree of
resiliency, such as natural rubber or suryical
foams used for bone rebuilding (such as the
fiber-reinforced polytetrafluoroethylene foam
described in U.S~ Patents No. ~,129,470 and
3,992,725), could be useful to form prosthetic
menisci for particular joints.
The reinforcing material 14 is preEerably
a closely-woven fine fabric mesh of stainless steel
or nylon, Dacron~or rayon strands. Other stranded
material of similar strength could be used, such as
polyaramid fabric. When the fabric or mesh is
embedded in the resilient material, such as by
casting or molding a meniscus with the fabric held
in place at the center of the molds, the resilient
material extends through the openings between
strands of the fabric to prevent separation of the
resilient material from the fabric. Alternately, a
sheet of reinforcing material ha~ing some
flexibility but being more rigid than the resilient
material of the body 11 could be embedded therein.
Such a sheet would preferable by perforated to
allow the resilient material to pass through the
perforations. The strut 12 defines a pair of
openings 15 therein to enable the strut 12 to be
attached to the boneO
Fig. 5 shows a lateral plan view of the
knee joint, and shows the lateral prosthetic
meniscus 10 mounted with respect to the joint. The
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body 11 of the meniscus 10 is positioned between
the natural articular surfaces of the démur 16 and
tibia 17. The strut 12 extends laterally out of
the joint and upward along the side of the femur
16. Preferably, in attaching the strut 12, a
groove is formed in the surface of the femur to
receive the strut 12 so that it can be mounted
flush with the surrounding bone surface. A
stainless steel cover 26 defines a pair of holes 27
therein positioned to mate with the holes 15 of the
strut 12. In attachment of the strut 12 to the
femur, surgical screws 28 are inserted through the
holes 27 and 15 and into the bone.
lS A medial prosthetic meniscus 20 for use
in the knee joint is shown in Fig. 2. The meniscus
20 is similar in construction to the meniscus 10,
and includes a body portion 21, a strut 22,
reinforcing material 23 embedded therein, and a
pair of attachment holes 24 in the strut. It will
be noted that the shape of the body portion 21 is
different from that of the body portion 11 of the
meniscus 10, because the shape of the natural
medial meniscus differs from that of the natural
2S lateral meniscus. Fig. 6 shows the medial
prosthetic meniscus 20 mounted in the medial
portion of the knee joint shown in Fig. 5. The
strut 22 extends downwardly and is attached to the
surface of the tibia in the same fashion that the
strut 12 was attached to the surface of the femur
Figs. 7 and 8 further show the
positioning of the prosthetic menisci 10 and 20 in
the knee joint. Fig. 7 is a rear plan view of the
joint showing the menisci 10 and 20 in position
between the articular surfaces of the femur 16 and
the tibia 17. The lateral prosthetic meniscus 10
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lies between the lateral articular surfaces 32 and
33 of the tibia and femur, respectively. The
prosthetic meniscus 20 lies between the medial
articular .swrfaces 30 and 31 of the tlbia and
femur, respectively. It wlll be noted that
insertion of the menisci 10 and 20 does not
necessitate significant relocation of any of the
ligaments of the knee. Therefore, the central
ligaments such as the posterior cruciate ligament
34 and the anterior cruciate ligament 35 are left
to perform their functions in the nGrmal manner.
Furthermore, outer ligaments such as the medial
ligament 36 and the lateral ligament 37 remain in
,
their normal positions to form the joint capsule
and assist in holding the menisci lO and 20 in the
proper posi~on. Fig. 8 is a top plan view of the
superior surface of the tibia, showing place~ent of
the prosthetic menisci lO and 20. Fig~ 8 shows how
20` the body portions ll and 21 of the menisci lO and
20 are shaped to engage the articular surfaces of
the tibia. It can be seen from Fig. 7 and 8 in
particular that replacement of the natural menisci
by the prosthetic meniscus lQ and 20 allows full
~ natural articulation of the knee j~oint and also
provides the cushioning and lubricating function
provided by the natural menisci.
~ig. 3 shows an alternate embodiment of a
lateral prosthetic meniscus 40 in which the strut
; 30 41 for extra-articular attachment of the meniscus
40 is not embedded in the resilient material that
- forms the body portion ll. The strut 41 can also
be embedded in a very thin layer of the resilient
material.
Fig. 4 shows another alternate embodiment
of a lateral prosthetic meniscus 42 for a knee
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joint. The strut for extra-articular attachment is
not seen in the bottom vlew of Fig. ll, but is
identical to the strut 12 as shown in Fig. 1. In
the meniscus 42, loops formed by strands of the
reinforcing material 14 extend horizontally
outwardly beyond the surface of the body portion
44. Such loops 43 would be primarily located
around the outer side of the meniscus and would be
used to suture the meniscus 42 to adjacent
ligaments, soft tissue or both. Thus, the meniscus
42 can have an embedded extra-articular extension
as well as non-embedded projections in the joint
capsule. Alternately the extra-articular extension
could also be non-embedded as shown in Fig. 3.
It should be understood that the
modifications described in connection with the
lateral prosthetic menisci 40 and 42 can be readily
utilized in a medial meniscus for the knee or for a
meniscus designed for any other joint. It will be
-further understood that in the case of a
reinforcing mesh embedded entirely within the body
portion, sutures can be inserted through peripheral
areas of the body portion and through the embedded
mesh to secure the meniscus to adjacent ligaments
or soft tissue.
A prosthesis 45 for a hip joint is shown
in Fig. 9. The prosthesis 45 includes a body 46
and a plurality of struts 47 extending therefrom
for extra-articular attachment of the prosthesis 45
to the ilium 18. The prosthesis 45 is constructed
in a manner generally similar to the knee joint
menisci lO and 20 described hereinabove and
includes a reinforcing mesh 49. Fig. lO is plan
view of the hip ~oint showing the prosthesis 45
positioned between the ilium 18 and the femur 16.
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_ The struts 47 are attached to the ilium in the same
manner as the struts 12 and 22 of the knee joint
are attached to the bones of the kn~ee. Since the
struts are adjacent to one another, a continuous
stainless steel cover 48 can be used to cover all
of the struts 47. Alternately, they can be
individually covered and attached in the manner
described hereinabove.
In the embodiments of the invention shown
in Figs. 1-lO, it will be seen that each
extra-articular extension of the various prostheses
is preferably attached to-the body portion alony
less than one-fourth of the length of the body
portion. This enables movement of the body portlon
within the joint within limits generally fixed by
the anchoring of the extension outside the joint.
Thus, when anchoring is needed along the length of
~he body portion, multiple extensions are
preferably used, as shown in Fig. 9, rather than a
continuous extension. The narrower extensions also
require less disruption of the tissue forming the
joint capsule. However, the broad concepts of the
invention can be embodied in a prosthesis having
one or more extensions connected along more than
one-fourth the length of the hody portion.
It should also be noted that the
thickness of the body portion can vary acrosg the
body portion to conform to the varying thickness of
a natural cartilage.
Fig. ll shows a prosthetic meniscus 52
designed to replace the natural meniscus of the
temporo-mandibular joint. The meniscus 52 includes
a body portion 53 constructed of resilient material
and an integrally formed U-shaped strut 54 which
extends outside the joint. The strut 54 includes
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at least two openings 55 therein for attachment of
the meniscus 52 to the temporal bone. Embedded in
the body 53 and strut 54 is a mesh of reinforcing
material of the type described above. Again, the
shape of the body portion 53 of the meniscus 52
conforms to the shape of the natural meniscus ofthe
temporo-mandibular joint.
Fig. 12 is a side plan view of the jaw
showing the prosthetic meniscus 52 in place in the
temporo-mandibular joint. The body portion 53 of
the meniscus 52 lies between the condyle of the
mandible 58 and the glenoid fossa of the temporal
bone 59. The meniscus can be used with artificial
condyles of the type known in the art. A
stainless steel cover 57 is provided for protection
and attachment of the strut 54 in the same manner
as described above in connection with other
embodiments of the present invention.
Although the preferred structure for the
temporo-mandibular joint is shown in Fig. ll, the
meniscus 52 can also be formed without the opening
created by the U-shaped strut 54, and having one or
more openings 55. This results in a stronger, but
somewhat less flexible connection between the body
53 and the extension.
Surgical techniques needed to implant a
prosthetic meniscus embodying the invention are
similar to known techniques for cartilage removal
and will be readily understood by those skilled in
the art. Attachment using surfical screws required
to affix the extra-articular extensions to the
bones is a well known surgical technique.
In addition to the method of attachment
of the struts using surgical screws, the struts 12,
22, 41, 47 and 54 can be attached by other means
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- such as adhesive, wire or surgical staples.
Unlike some prior prostheses showing a
thin strip of material passing only through the
center of a flexible meniscus, as shown in Russian
Patent 637,118, intended to provide means for
attaching the meniscus within the joint capsule,
the reinforcing mesh of the present invention
extends substantially over an entire cross-section
of the body of the meniscus to provide strength
across the bearing surface provided by the
meniscus. The strength thus i~parted permits the
insert portion of the prosthesis to be thin where
required ~o duplicate the natural spacing of the
joint, and permits the extension to be thin to
avoid unsightly protruding lumps in the exterior of
the limb or other body part.
It will be seen that the prosthetic
meniscus embodying the invention provides a strong
meniscal replacement that is retained in proper
position and is still able to accomplish the
cushioning and lubrication functions of the natural
meniscus and to allow the full range of normal
movement of the joint. The resilient material
comprising the meniscu~ twists, translates and
deforms under the force of the bones of the joint,
but returns to its original shape. The reinforcing
material assists in shape retention and prevents
tearing of the prosthetic meniscus even in
situations where a natural meniscus might tear. The
extra-articular extension allows the prosthesis to
be positively, though not rigidly, located, without
interfering with the functioning of the body
portion of the prosthesis.
While this invention has been described
3S in detail with particular reference to preferred
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embodiments thereof, it will be understood that
variations and modifications can be effected within
the spirit and scope of the invention as described
hereinbelow and as defined in the appended claims.
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