Invention (Patent Application Publication): Pedersen WB, Steenstrup FR, Olsen OI, Jakobsen LD, Vraa E, Lauritzen JB, Bechgaard K. A prosthetic device. WO2001045595A2 (2001).
Inventors: Walther Batsberg Pedersen , Frederik Resen Steenstrup , Ole Ingemann Olsen , Lene Diness Jakobsen , Erik Vraa , Jes Bruun Lauritzen , Klaus Bechgaard
Worldwide applications: 2000 IL KR CA US JP EE EP DE AU NZ YU SK HU MX CZ AT WO PL BR EA CN 2002 ZA NO BG 2003 HK 2007 US
Application PCT/DK2000/000697 events:
2000-12-14 Priority to IL14995000A
2000-12-14 Priority to EEP200200329A
2000-12-14 Priority to EP00983081A
2000-12-14 Priority to BR0016474-7A
2000-12-14 Priority to AU19964/01A
2000-12-14 Priority to DE60026585T
2000-12-14 Priority to KR1020027007787A
2000-12-14 Priority to JP2001546337A
2000-12-14 Priority to EA200200664A
2000-12-14 Priority to MXPA02005863A
2000-12-14 Application filed by Cartificial A/S
2000-12-14 Priority to HU0500988A
2000-12-14 Priority to US09/926,756
2000-12-14 Priority to NZ520073A
2000-12-14 Priority to CA002392782A
2000-12-14 Priority to SK823-2002A
2001-06-28 Publication of WO2001045595A2
2002-03-07 Publication of WO2001045595A3
2002-06-17 Priority to NO20022905A
2002-06-24 Priority to BG106862A
2003-03-08 Priority to HK03101692.6A
A prosthetic device
Walther Batsberg Pedersen , Frederik Resen Steenstrup
, Ole Ingemann Olsen , Lene Diness Jakobsen , Erik Vraa , Jes Bruun Lauritzen, Klaus
Bechgaard
Abstract
The
present invention relates to a method and a device for alleviating and/or
preventing conditions relating to damaged joints involving articulating
surfaces, a prosthetic device for insertion into a joint cavity of a joint of a
vertebrate, such as a human, said device consisting of a biocompatible material
comprising at least a first polymeric component and a second polymeric
component, wherein the chain length of the first polymeric component is longer
than the chain length of the second polymeric component, the polymeric
components in particular being polyethylene, polypropylene and/or
polyvinylpyrrolidone. A further aspect of the invention relates to a method for
introducing the prosthetic device into a joint, such as a method comprising
locking the device to an intro-articular component, thereby fixing or retaining
the device in the joint cavity in a manner which is substantially non-invasive
with respect to cartilage and bone natively present in the joint cavity. Also
the invention relates to an instrument for inserting a prosthetic device
according to the invention, comprising means for deforming the prosthetic
device into a reduced volume or a slender shape and means for grasping the
intra-articular component to which the device is capable of interlocking.
Description
FIELD OF INVENTION
The present
invention relates to a method and a device for alleviating and/or preventing
conditions relating to damaged joints involving articulating surfaces.
GENERAL BACKGROUND
At present, joint
damage, such as cartilage damage, is treated by replacing the joint with an
artificial joint. However, serious complications are caused by the replacement
of artificial joints, in particular a high occurrence rate of loosening
problems resulting in breakage of the bones around the artificial joint.
In particular, the
invasive character of the fixation of the prostheses such as anchoring of the
prosthesis with screws and pins results in numerous side-effects such as risk
of infection, loosening as mentioned above, damage on excising bone due to
interruption of blood supply and necrosis.
A device for
replacement within a joint should preferably enable the normal function and
movements of the joint. Weight-bearing joints, in which movement in more than
one direction takes place, are normally rather difficult to replace.
A prosthetic device
should enable the normal movement of the joint. During walking, the normal
movement of for example the hip joint corresponds to about 37°-41°
flexion/extension, 2°-14° adduction/abduction and a rotation of about 2°-16°.
During movement from standing to sitting position a flexion of hip joint
corresponds to a movement from 0 to 90 degrees. When studying the movement of
femoral caput to the acetabulum the latter movement includes a rotation of 90
degrees.
So far, no
satisfactory device for placement within a joint has been achieved in the prior
art.
SUMMARY OF THE INVENTION
In a first aspect
the present invention relates to a prosthetic device for insertion into a joint
cavity of a joint of a vertebrate, such as a human, said device consisting of a
biocompatible material comprising at least a first polymeric component and a
second polymeric component, wherein the chain length of the first polymeric
component is longer than the chain length of the second polymeric component.
The invention
disclosed furthermore relates to a prosthetic device for insertion into a joint
cavity of a joint of a vertebrate such as a human, wherein the body of the
device comprises a polymer material, and wherein the device is non-invasive with
regards to the intra-articular components when the device is in the joint
cavity, said device being adapted to alleviate conditions associated with worn
cartilage, and in a third aspect the present invention provides: a prosthetic
device for insertion into a joint cavity of a vertebrate such as a human,
wherein the body of the device comprises a polymer material, and wherein the
device comprises a hole extending through the body of the device.
By the term
"non-invasive" is meant that the device is preferably not attached to
joint components through the use of screws, stitches or the like.
Also, the invention
relates to a method for introducing a prosthetic device into a joint, such as a
method comprising locking the device to an intra-articular component, thereby
fixing or retaining the device in the joint cavity in a manner which is
substantially non- invasive with respect to cartilage and bone natively present
in the joint cavity.
Another aspect of
the invention is an instrument for inserting a prosthetic device according to
the invention, comprising means for deforming the prosthetic device into a
reduced volume or a slender shape and means for grasping the intra-articular
component to which the device is capable of interlocking.
Yet a further
aspect of the invention relates to the use of a prosthetic device for
establishing slidabihty and/or distributing pressure in a joint of a vertebrate
such as a human, by inserting into the joint cavity of the joint a prosthetic
device, preferably a prosthetic device as defined in this invention, capable of
locking itself to an intra-articular component and thereby being fixed or
retained in the joint cavity in a manner which is substantially non-invasive
with respect to cartilage and bone natively present in the joint cavity.
Another aspect
relates to a method for establishing slidability and/or pressure distribution
in a joint of a vertebrate such as a human, comprising inserting into the joint
cavity of the joint, a prosthetic device, preferably a prosthetic device as defined
herein, which is capable of locking itself to an intra-articular component and
thereby being fixed or retained in the joint cavity in a manner which is
substantially non-invasive with respect to cartilage and bone natively present
in the joint cavity.
Yet another aspect
is a kit comprising:
a) an
intra-articular prosthetic device for a joint having
a.1 ) a spacer
function and/or capability to exert pressure distribution and/or
sliding/rotating movement of the joint by internal movement of the device by
means of a resilient member, and
a.2) a locking
mechanism adapted to fix the device to an intra-articular component by means of
an element of the device surrounding the component in such a manner that
displacement of the device is limited by inter-locking with the component; and
b) an instrument
for inserting the prosthetic device into a joint cavity.
DETAILED
DESCRIPTION OF THE INVENTION
The device and
units are designed to occupy at least part of the intra-articular cavity to
partly or completely fill the role of natural cartilage within a joint. The
device or its units may be designed so as to occupy the whole of the cavity or
merely a portion of the intra- articular cavity, such as the portion of the
cavity where cartilage is worn or where much of the pressure is exerted. The
device and its units may radially encircle an intra-articular component
spanning a longitudinal axis of the cavity or may occupy one or more portions
of the cavity laterally removed from the intra-articular component and its
axis.
The device and
units may be designed not to interfere and to be non-invasive with regards to
intra-articular components when the device is in the joint cavity by means such
as a slit in the body of the device.
Moreover,
non-interference of the intra-articular components may be achieved by a hole
which runs through the body of the device; that is to say the device may
comprise a hole through which intra-articular components may pass. When loading
the device, the slits may serve to pass intra-articular components through the
body of the device. The slits in this embodiment run from the periphery of the
body of the device to the hole through which the intra-articular components
pass after the device is implanted or loaded.
Typically, and to
at least some extent, the device is adapted in its structure and/or material
composition to alleviate conditions associated with worn cartilage by providing
a spacer function and/or to exert pressure distribution in the joint when the
joint is loaded and/or to provide at least part of the sliding/rotating
movement of the joint by internal movement of at least part of the device.
It is also an
object of the present invention to provide a method for non-invasive locking of
a device within a joint. In addition, the method is independent of use of
cement or bony ingrowth of the device.
A still further
object of the present invention is to provide a kit for use in the method for
non-invasive locking of a device within a joint.
It is also an
object of the present invention to provide a method for preventing damage
between mating surfaces or articulating surfaces within a joint such as between
the femoral head and the acetabulum of a hip joint.
A more specific
object of the present invention relates to a prosthetic device for insertion
into a joint cavity of a joint of a vertebrate such as a human, the device is
being adapted to provide a spacer function and/or to exert stress distribution
in the joint when the joint is loaded and/or to provide at least part of the
sliding/rotating movement of the joint by internal movement in the material of
at least part of the device, the device being capable of locking itself to an intra-articular
component and thereby being fixed or retained in the joint cavity in a manner
which is substantially non-invasive with respect to cartilage and bone natively
present in the joint cavity.
Physical-Structural
Features of the Device
The physical-structural
features of the device relate to the size, form or shape of the device as well
as the structural components and design components of the device.
Size and Shape
The overall shape
of the device is such that it substantially fits into the excising anatomical
dimensions of the joint. In general, the size and shape of the device are such
that the device fits into the intra-articular cavity in that it may partially
or fully occupy the space defined by the cavity. For some of the joints it is
preferred that the extent of the device, when positioned in the joint cavity,
is larger than the normal extent of cartilage on the bone end in that joint.
In a preferred
embodiment, a hole runs through the body of the device to allow intra-
articular components to traverse the body of the device and thus be surrounded
by the device.
In this embodiment,
the device may be construed in a liberal sense as essentially torus- shaped in
that the device can be of a plurality of geometrical shapes, symmetrical and
asymmetrical, comprising a hole which runs through the body to create an
internal tubular passage through which intra-articular components may pass.
The device may also be ball-shaped, disc-shaped, spherical, globular-shaped, cup- shaped, cone-shaped, ring-shaped, cylindrical and have convex, concave, or flat surfaces. Accordingly, the body of the device shape can e.g. be in the form of a horseshoe, a curl, ring-shaped, circular or semicircular so as to be suitable for fitting into the anatomical dimensions of the particular joint. Furthermore, the device may be unsymmetrical.
The body of the device may be of a geometrical shape comprising a surface having the form of body shaped by rotating a circle about a coplanar axis which does not intersect the circle. It may be ball-shaped, disc-shaped, globular-shaped, cup-shaped, cone- shaped, ring-shaped, cylindrical and may comprise convex, concave, or flat surfaces. In some aspects it is characterised in that it comprises a hole extending from one surface of the body of the device to the same or another surface, creating an internal tubular cylinder. This internal tubular cylinder may be straight if the hole extended to two parallel surfaces, curved if the hole extends to perpendicular surface, U-shaped if the hole extends to two parts of the same surface or a combination of one or more of these internal shapes and thus tortuous.
Certainly, given
that the overall shape of the device is such that it substantially fits into
the excising anatomical dimensions of the joint, it is anticipated that the
body of the device may be asymmetrical or of no definable shape so as the fill
the intra-articular cavity, to allow for the movement of the intra-articular
components during the flexing of the joint, to support intra-articular components
or to support matter which form the walls of the cavity.
It is preferable
that the shape of the device is such that it does not impede the normal
functioning of the joint and its components.
It is particularly
anticipated that the body of the device may be asymmetrical or of no definable
or uniform shape when the device is for use in a hip joint. Alternatively, the
shape of the device may be such that it resembles the native cartilage, or part
thereof, naturally present in the joint cavity.
Accordingly, in the
case of a hip joint, the shape of the device is preferably such that it fits
into the existing space of the joint cavity comprising ligamentum capitis
femoris, the "walls" of the space being defined by the concave shape
of the acetabulum and by the convex shape of the femoral head.
Moreover, the
overall shape of the device may be a result of an assembly of more than one
units of the device, such as the assembly of two or more rings of different
sizes stacked upon each other so as to form a cone-shaped device. The assembly
of units may be done in vivo or ex- vivo.
Furthermore, in
preferred embodiments, the overall shape is such that the device is capable of
locking itself to an intra-articular component if present in said joint and
thereby being fixed or retained in the joint cavity. When the intra-articular
component is a ligament, the shape is such that the ligament is surrounded or
substantially surrounded by the device.
However, the
overall shape of the device may have any other form as long as the material is
of such a character that the device when present in situ fits into the joint
cavity, for example due to elastical deformation of the device.
Preferably, the
elastical deformation of the device is such that the presence of ligamentum
capitis femoris results in a shape leaving room for the ligamentum. Otherwise,
the surface of the upper part of the device facing the acetabular cavity may
comprise a groove embedding the ligament.
Typically, the
shape of the device is formed from a moulding of its materials or from a
casting process. It may alternatively be the result of a framed structural
construction or skeletal assembly. It is typically solid in that the body of
the device is not hollow but rather such that the material of the device
comprises all or essentially all of the space between two surfaces. The
moulding, casting, construction or assembly may form a device into a uniform or
non-uniform shape.
The device is
essentially uniform in its stiffness or compressibility. However, when loaded,
the material may have a tendency to deform in such a way that the locking
mechanism is altered. This may occur if the element adapted to surround the
ligament, when present in situ, has a slit which expands or gapes upon loading
when the device is pressed together. This gaping may be further pronounced when
the patient is e.g. walking whereby the ceiling of the acetabulum is pressed
down on the upper surface of the device and the lower surface of the device is
pressed down on the spherical surface of the femoral head.
Due to the rolling
movement (rotation within the joint) of the femoral head, the possibility
exists that the femoral head may press itself up into the slit of the device
during the movement. In such cases, the press distribution and/or internal
movement of the device may be limited to a minor part of the device that may
result in an undesirable increased pressure on that portion of the device.
Finally, contact between the femoral head and the acetabulum may occur in case
the femoral head penetrates through the device. However, a device comprising
parts overlapping each other can prevent this possible undesirable effect.
Accordingly, as
mentioned above, the device may be curl-shaped whereby the device with respect
to the slit or opening has overlapping parts which do not represent a complete
opening in the loading direction.
The size of the
prosthetic device according to the invention may be of any size corresponding
to the dimensions of the joint. In a hip joint, a suitable size is normally one
that allows the diameter of the device to be about the same or less than the
diameter of the femoral head. However, on some occasions the diameter may
exceed that of the femoral head. The size may also depend on the degree of
damage of the native cartilage of the joint. Moreover, the space available
within the joint in the individual may have an effect on the preferred
diameter. Also the compressibility of the material should be taken into
account. In the case in which the material is highly compressible, the device
may increase in diameter upon loading of the joint; when loaded, the device
should generally cover the surface area which is covered with cartilage in the
normal joint, e.g., in the hip joint, the surface of caput femoris should
preferably be substantially covered when the joint is loaded to avoid contact
of the surface of the femoral head with the acetabulum.
The length of the
diameter of the device is designed to fit into the particular joint, such as
between 15-80 mm, such as between 25-70 mm, preferable between 30-60 mm, more
preferable between 35-50 mm, most preferred about 40 mm, when the joint is
loaded.
The prosthetic
device according to the invention may vary in thickness depending on the load
on the joint, and the thickness of the device may also vary within the device.
The thickness of
the device is at least 0.5 mm, such as at least 1.0 mm preferably between 2-60
mm, such as between 6-40 mm, preferably 8-30 mm, more preferably about 10-20
mm, most preferably about 15 mm in the unloaded stage. Depending on the
material, the device may be highly compressible, whereby the initial thickness
may exceed the above-mentioned upper limit. If only a limited rotation takes
place in the joint, the thickness of the device may be decreased.
In one embodiment
of the invention, the device is capable of locking itself to the intra- articular
component by at least one element of the device surrounding the component in
such a manner that displacement of the element, and thereby the device, is
limited by interlocking with the component. The intra-articular component which
is surrounded is preferably a ligament, such as a ligament natively existing in
the joint cavity.
In one embodiment
of the device according to the invention, the element completely or
substantially completely surrounds the ligament.
Thus, one
embodiment of a prosthetic device according to the invention relates to a
device wherein the element interlocking with a ligament, when present in situ,
permits the ligament to extend through the element and substantially exert its
natural function on the joint.
In one aspect of
the invention, the prosthetic device is intended for the articulation of a hip
of a human, said device being adapted such that when present in situ in the
human hip joint cavity, it comprises at least one element surrounding
ligamentum capitis femoris. Accordingly, ligamentum capitis femoris represents
the surrounded intra-articular element mentioned above.
It is contemplated
that the surrounding of the intra-articular component by the element may be a
completely or substantially completely encircling of the ligament.
It is also
preferred that the prosthetic device, when present in situ, comprises at least
one ring-shaped or substantially ring-shaped element.
According to
another aspect of the invention, the element of the prosthetic device which is
adapted to surround the ligament when present in situ has such a shape and such
properties that it can be placed around the ligament and stay interlocked with
the ligament.
Structural
Components
The device preferably comprises structural components which permit arrangement of the body of the device around native intra-articular components.
When the prosthetic
device according to the invention is a hip endoprothesis, the device has a
shape and structural components permitting arrangement of the body of the
device around ligamentum capitis femoris.
A prosthetic device
according to the invention comprises a device wherein the element of the device
interlocking with the device with an intra-articular component has such a shape
and/or properties that it is capable of replacing or supplementing worn or
damaged cartilage in the joint and/or is capable of preventing wear of the
native cartilage of the joint or of the bone tissue of the joint.
The structure of
the material of the device or of a part of the device may be in the form of
fibres and filaments which can be incorporated into the matrix in a braided,
woven, spongy or spiral pattern, the fibres and filaments having reinforcing
properties. The fibres may be inorganic fibres such as carbide, nitride,
boride, carbon and oxide fibres, or the reinforcement may be of organic origin
such as Dacron™. In a preferred embodiment the fibres are selected from
polyethylene fibres, polypropylene fibres or a combination thereof.
The structure of
the material of the device may comprise a layered or laminated structure, a
core of one material or one or more interposed layers with different properties
enabling an overall function of the devise suitable for providing a spacer
function and/or to exert pressure distribution in the joint when the joint is
loaded and/or to provide at least part of the sliding/rotating movement of the
joint by internal movement of the device, or relevant part of the device.
However, it is preferred that the material itself does not comprise interposed
layers resulting in sliding between the layers and thereby tear on the mating
surfaces within the device. Accordingly, the body of the device should be one
continuous solid or semi-solid material.
In one preferred embodiment of the invention, the device comprises a tubular passage through which the ligament can pass and be surrounded by the body of the device, as depicted in Figure 5. Circular movement around the substantially central ligament is possible but replacement of the device is prevented. A further feature of the structure of the device may be that of a slit extending from the outer surface of the device and through the body of the device into the central tubular passage. The slit may be curl-shaped in the radial direction with the axis of the tubular passage being the centre as depicted in Figures 7, 9 and 11.
The slit may curl
or curve into the body of the device so as to form an S-, or C-shaped slit, or
zigzag or spiral slit. The curl of the slit may be in the two dimensions of a
disc shaped device, as in Figures 7, or may curl in all three dimensions in the
case of a globular, spherical, cone-shaped or cup-shaped device, as depicted in
Figures 9, 19, 22, or 27.
Furthermore, in
embodiments where the device comprises more than one unit, the curvature of the
slit may be such as to form a zigzag, spiral or S- or C-shaped multi-unit slit.
In multi-unit
devices, the outer surfaces of the parts of the unit which are in contact with
each other may have a surface pattern preventing the units from sliding apart
such as grooves or etching or jagged surface pattern, as depicted in Figure 23.
Moreover, the
overall shape of the device may be from an assembly of two or more elements of
one device, such as two semi-circular elements assembled to form a ring or from
the assembly of two elements obtainable from the cross-sectioning of a ring or
globular device along their longest axis. As was the case for the surface of
two units, two elements may have a surface pattern preventing the elements from
sliding apart such as grooves or etching or jagged surface pattern. Thus, a
device and its shape may be the result of an assembly of two or more elements
and/or two or more units, each comprising surfaces designed to preventing
slippage of units and/or elements, as depicted in Figures 26-28.
If suitable, the
device may comprise a material which functions as a frame for the shape or
secures the device from opening when placed in situ, for example in the form of
a shaped component having the properties of a spring or the like.
In one embodiment,
the ring-shaped body of the device has a slit or other suitable means which
enables the device to be placed in the position encircling ligamentum capitis
femoris. Upon loading the device into the joint, the element of the device
surrounding the component, e.g. a ligament, and thereby interlocking with the
component, may tend to open up due to deformation of the device in the form of
flattening resulting in an increased diameter. When the diameter of the device
increases, e.g. the diameter of a ring-shaped device comprising a slit, the
adjoining surfaces of the slit may gape.
As stated, during
the compression, extension or rotation of the device when the device is present
in a joint, the slit may have a tendency to gape and thus result in reduced weight-
bearing effectiveness and/or result in trapping of intra-articular components
within the seam of the slit. Preferably, the seam cannot be pulled apart in the
direction of the plane of the seam by the mechanical pressure exerted by the
body of the device conferred by the elastic properties of the material.
To prevent undesired slippage of the seam perpendicular to the plane of the seam, a variety of means may be incorporated into the design of the device so as to lock or adhere the two sides of the seam. Preferably, the locking or adherence means are reversible so as to allow removal or manipulation of the device after initial loading and use. The seam is preferably characterized in that a smooth surface is formed in the plane of the seam.
To prevent the
device from opening, the device preferably comprises overlapping or
intersecting parts, such as lips or dovetails as is known by the person skilled
in the art of mechanics or moulding. The two sides of the seam may be adjoined
by means of an interlocking device such as a protrusion-hole device on sides of
the seam. Alternatively, to prevent slippage in perpendicular to the plane of
the seam, each side of the seam may be such that each side of the seam
comprises an alternating sequence of angled grooves and corresponding
extrusions. Moreover, the top and bottom portion of each side of the seam may
comprise alternating teeth and sockets to prevent slippage. To prevent gaping
such overlapping parts and their mating surfaces of the sides of the seam may
have an interlocking surface structure. The pattern of such a structure may
include depressions on the mating surface of one part and corresponding
elevations on the other mating part of the device.
Accordingly, in one
embodiment, the overlapping parts are such that the interlocking surface
structures constitute grooves. These grooves may extend radially, primarily
resulting in a decreased tendency of the device to "open up" at the
area corresponding to the slit or the gap. The grooves may also be orientated
in a circulatory structure preventing the mating surfaces from gliding or
sliding apart from each other. Additionally, the structure may comprise a
combination of both elements reducing undesired movement in both of the two
directions, when the device is deformed during loading of the joint.
The terms
"radially" and "circular" should be understood as relative
to the centre of the device or relative to the part of the device where the
ligament extends through the device. "Radially" meaning e.g. grooves
being located along radii from the centre, and the term "circular"
meaning that e.g. the grooves are located along the periphery of a circle
around the centre.
In another
embodiment, the pattern includes other prominences or knobs, including pointed
elevations. Thus, any structure comprising an elevation on one mating surface
and a corresponding depression on the other mating surface may result in a
decreased movement between the mating surfaces. Accordingly, any structure of
the mating surfaces which thereby functions as an interlocking "hook"
is within the scope of the invention. The mating surfaces of the curls may have
an interacting profile in the form of a shape or pattern such as grooved
surfaces which prevent the surfaces from sliding apart by reducing sliding
movements between the mating surfaces upon loading of the device.
Another preferred
embodiment of the invention relating to the seam created by the slit in the
body of the device, accounts for preventing of slippage or gaping of the seam
by means of a chemically treated surface of the sides of the slit. One
embodiment of this aspect of the invention anticipates adherence of the two
sides of the seam by means of photolytically or thermally activating a reaction
between the chemically treated surfaces of the sides of the seam once the
device has been loaded into the joint. Preferably, this adherence is
reversible.
In another
embodiment, the device may also comprise two or more separate rings each having
a slit which are arranged so that the slits are orientated in such a way that
no direct opening exists in the loading direction, accordingly, the slits are
displaced in the direction parallel with the axis of the device. Mating
surfaces of such rings may also have an interlocking structure as explained
above.
In a still further
embodiment, the device is in the form of a curl, wherein the ring-shaped
elements together have the overall shape of a cup. Also in this embodiment, the
mating surfaces may comprise grooves preventing sliding movements of the mating
surfaces upon loading.
In a still further
embodiment, the device may comprise minor vertical slits on the outer periphery
of the device, these minor slits, e.g., having a depth of 1-5 mm may
"absorb" the increasing diameter of the device upon loading.
Preferably, the part of the device comprising the slits (the outer periphery)
is not subject to heavy loading which could result in particulation of the
edges of the device corresponding to the slits. These minor vertical slits on
the outer periphery of the device may alternatively serve so as to not
interfere with movable or immobile components of the joint within the cavity.
The device
according to the invention may e.g. be processed by moulding of the material
including extrusion and injection moulding. However, any other means for
preparing the device of the desired shape could be utilised.
In addition, the
device may comprise a dye or other material enabling visualisation of the
device such as by X-ray.
Material Features
The material
features of the device related to features conferred by the chemical
composition of the device.
It is well known in
the orthopaedic field to use different types of materials for prostheses that
are suitable for implantation in the body. The device may be produced from any
material or combination of materials suited for implants. However, it is
preferable that the body of the device does not comprise of any substantial
extent of metallic materials. The combination of materials can be varied
according to the properties preferred for each device. However, the body of the
device, is substantially constituted of polymeric material or materials.
Preferably, the
material of which the device is made is biocompatible, e.g. hemocompatible,
thromboresistant, non-toxic, and/or non-carcinogenic. In addition, the material
should be resistant to particulation, and the solid surface of the material
should be so that the surface tension is suitable for the interaction between
the material and the biological surfaces.
Biocompatibility
may be assayed through in vitro tests as well as animal tests. Enzymatic
biodegradation may be used as indicative of biocompatibility. Furthermore,
chondrocytes and fibreblasts may be grown on the material to evaluate the
compatibility.
Finally,
biocompatibility may be evaluated by implanting devices of the material in
animals and examining the animal and/or device after a period of time.
The device is to be
substantially composed of polymeric material, particularly solid or semi-solid
polymers. Polymers are the family of synthetic or natural macromolecules
consisting of inorganic, organic polymers and combinations thereof. Organic
polymers may be natural, synthetic, copolymers, or semisynthetic polymers.
Natural polymers comprise of the class of compounds known as polysaccha des,
polypeptides, and hydrocarbons such as rubber and polyisoprene. Synthetic
polymers comprise elastomers such as nylon, polyvinyl resin, polyvinyl chloride,
polyvinyl dichloride, polyvinylpyrrolidone, polyethylene, polystyrene,
polypropylene, polyurethane, fluorocarbon resins, acrylate resins,
polyacrylates, polymethylmethacrylate, linear and cross-linked polyethylene,
phenolics, polyesters, polyethers, polypyrolidone, polysulfone, polyterpene
resin, polytetrafluoroethylene, polythiadiazole, polyvinylalcohol,
polyvinylacetal, polyvinyl oxides, and alkyds. Semisynthetic polymers may be
selected from cellulosics such as rayon, methylcellulose, cellulose acetate and
modified starches. Polymers may be atactic, stereospecific, stereoregular or
stereoblock, linear, cross-linked, block, graft, ladder, high, and/or
syndiotactic. The term graft polymer is intended to mean copolymer molecules
comprising a main backbone to which side chains are attached. The main chain
may be a homopolymer or copolymer and the side chains may contain different
inorganic or organic constituents.
The device may
comprise of cross-linked polymers elastomers such as high consistency elastomers,
rubber, elastin and collagen. The material may be selected from polyurethane,
elastin, collagen and combination products thereof. Alternative embodiments of
materials suitable for the surface of a device according to the invention
include, in addition to the materials mentioned supra and infra include
hyaluronic acids and derivatives thereof.
Preferred polymeric
materials are however presently believed to be those selected from the group
comprising poiyolefins, such as polyethylene, polypropylene, polybutene,
polyisoprene, and polyvinylpyrrolidone, combinations thereof, their copolymers,
and grafted polymers thereof, particularly polyethylene and polypropylene, most
particularly polypropylene.
Polymers and
copolymers of polypropylene or polyethylene, as well as grafted forms of each
of these are particularly interesting. Moreover, surface treated forms of these
polymers, copolymers or grafted polymers are of notable interest.
The structure of
the material of the device or of a part of the device may be in the form of
fibres and filaments which can be incorporated into the matrix in a braided,
woven, spongy or spiral pattern, the fibres and filaments having reinforcing
properties. The fibres may be inorganic fibres such as carbide, nitride,
boride, carbon and oxide fibres, or the reinforcement may be of organic origin
such as Dacron™. In a preferred embodiment the fibres are selected from
polyethylene fibres, polypropylene fibres or a combination thereof. The fibres
may be surface treated before incorporated into the matrix to obtain a better
adhesion of fibres to matrix.
The present
invention in particular relates to a device composed of material formulations
intended to meet the specifications of durability, biocompatibility, etc. These
properties are obtainable by treating polymer materials, such as polyethylene,
polypropylene or polyvinylpyrrolidone or combinations and co-polymers thereof
as well as precursor materials for polymerisation, with high-energy electrons,
gamma rays, photons, microwaves, ion implantation, plasma treatment, annealing,
thermal radiation or another radiation to obtain ideal durability and
biocompatibility of the new, modified material. Treatment of the
above-mentioned materials with radiation leads to cross-linking of polymers and
thereby generating new, modified materials. Preferably, the polymer material is
a cross-linked polypropylene material. In another embodiment the polymer
material is a cross-linked polyethylene material.
A device according
to the invention preferably comprises at least a first polymeric component and
a second polymeric component, wherein the chain length of the first polymeric
component is longer than the chain length of the second polymeric component.
The first polymeric component is providing the physical properties, such as
strength of the device as discussed below. Due to the longer chain length the
strength, in particular the tensile strength, of the device is increased. The
chain length of the first polymeric component is preferably above 100 monomer
units, such as above 120 monomer units, preferably above 150 monomer units. The
chain length of the second polymer is preferably at most 99% of the chain
length of the first polymer, such as at most 95%, such as at most 90%, such as
at most 80%, such as at most 70%, such as at most 60%, such as at most 50%.
In one embodiment
the device comprises a body constituted by the first and the second polymeric
components. The body may optionally be treated in order to optimise the
properties such as surface properties, biocompatibility and/or low friction. By
the term "body of the device" is meant the part of the device
providing the strength properties as well as the resiliency properties.
In another
embodiment the device comprises a body constituted by the first polymeric
component, whereas the second polymeric component provides optimised surface
properties.
In a preferred
embodiment the first polymeric component is selected from polymers having a
carbon-backbone.
The first polymeric
component may be selected from polyacrylates, polystyrene, polyethers,
polytetrafluorethylene, polyvinylalcohol, polyethylene, and polypropylene.
When the body is
constituted by two components, the second polymeric component may be selected
from polyacrylates, polystyrene, polyethers, polytetrafluorethylene,
polyvinylalcohol, polyethylene, and polypropylene. Preferred combinations for
the first and the second polymeric component are polyethylene and
polypropylene, polyethylene and polyethylene, or polypropylene and
polypropylene, in the latter two cases, the first and the second polymeric
components is comprised of identical monomers, whereas the polymers thereof are
of different chain length. When the monomers of the two polymeric components
are identical the prosthetic device is preferably compounded to form a
bidispergent system.
The second
polymeric may in a preferred embodiment be a cross-linked polymer. The
combination of a polymer having a high chain length and a polymer having a
shorter chain length, but being cross-linked provides a strong device yet
having the resilient properties necessary for the device.
Furthermore,
radiation also allows grafting of polymers onto existing polymer surfaces,
resulting in new mechanical properties as well as new surface properties. In
this manner, the resulting modified polymer device can be processed to meet the
necessary requirements of durability and biocompatibility.
Polymers may be
prepared by methods known to the person skilled in the art. Chemical catalysis,
thermal induction or photo induction are anecdotal non-limiting examples of
methods of preparing the polymers. The cross-linking of the polymers or
grafting may be done by radiation or other methods known to the person skilled
in the art.
The properties of
the materials to be obtained by these cross-linking and grafting processes are
preferably i) resistance to tear and wear; ii) good compressibility; iii)
flexibility and surface properties which will allow wetting with biological
fluids, and/or eventually allow growth of chondritic cells onto the prosthetic
device.
Typically, the
device is prepared by a process comprising of the following steps:
• The prosthetic
devise is formed by casting the pure polymer or a blend of polymers in a mould
of specified dimensions. The polymer is chosen from the above mentioned
polymers.
• After hardening
the cast material as formed, or after swelling in a suitable solvent, the
device is subjected to high-energy electrons, gamma rays or another radiation
in order to create cross-linking which will modify the mechanical properties of
the cast material to meet the preferred specifications.
• Finally,
eventually after removal of the swelling solvent, the surface of the cast
material is treated to achieve good surface properties as described above.
The surface of the
device can subsequently be treated to modify surface properties such as wetting
ability and/or biocompatibility. This surface treatment can be performed by
plasma treatment, chemical grafting or by a combination of plasma treatment and
chemical grafting. The surface of the device contacting with the articulating
surfaces of the joint may be of such a material which forms a uniform contact
surface reducing the overall contact stress per unit area, and thereby avoiding
corrosion of the articulating surfaces of the joint. Accordingly, the material
contacting with the biological surfaces may be smooth, biocompatible,
preferably self-lubricating, and it should be wear-resistant so that powder
generated due to wear is avoided in that this could otherwise result in foreign
matter reactions and cause further trouble to the function of the joint.
Furthermore, the
surface material should preferably be a material or a combination of materials
having self-repairing properties so that fissures, cracks or other ruptures on
the surface do not exceed uncontrollable levels. However, the surface material
is preferably continuous with the material of the rest of the device, e.g. the
material may gradually merge into the material of the inner core or matrix of
the device.
The surface of the
material may be chemically treated so as to soften, rigidity or lubricate the
surface of the device or parts thereof. The surface of the material may be
coated so that the coating confers these properties, or may be treated so as to
chemically alter the surface of the device so as to confer any of these
properties. Alternatively, certain polymer surfaces may be modified by means of
thermal or photolytic energy.
Also the surface
treatment may be provided by incorporating surface treatment polymer, such as
polyvinyl pyrrolidone, into the matrix to maintain the good surface properties.
Independent of whether
the body of the device comprises one or two components, it is preferred that
the body of the device is provided with a treatment resulting in a functional
surface of the device being wettable by the joint fluid normally present in the
joint cavity, in order to decrease any friction between the device and joint
parts, such as bone, cartilage, ligaments and mucosa.
Without being bound
by theory it is also believed that a wetted surface reduces the risk of having
the immune system recognising the device when implanted, which would otherwise
lead to adverse effects of the device.
By the term
"functional surface" is meant the external surface of the device, ie.
the surface contacting joint cavity parts. Since the body of the device is
often produced as one, two or even three dimensional networks, internal surface
may be present in the body, said internal surfaces often corresponding with the
external surfaces.
Thus, the
prosthetic device preferably comprises a third polymeric component, said third
polymeric component being different from the first and/or the second polymeric
component. The third component will preferably be grafted to the body of the
device and result in the improved surface properties. The third polymeric
component is preferably selected from polyethylene oxides, and
polyvinylpyrrolidon, most preferably from polyvinylpyrrolidon.
When the body is
comprised of one component, such as wherein the first polymeric component
comprises a copolymer of polyethylene and polypropylene or wherein the first
polymeric component is a cross-linked polymer, the second polymer may be
grafted to the first polymer and act as the third polymeric component as
described above.
Preferred devices
are composed of:
A body of
polyethylene having polyvinylpyrrolidone grafted thereto A body of two
polyethylene polymers of different chain lengths having polyvinylpyrrolidone
grafted thereto
A body of
polypropylene having polyvinylpyrrolidone grafted thereto
A body of two
polypropylene polymers of different chain lengths having polyvinylpyrrolidone
grafted thereto A body of a copolymer of polyethylene and propylene having
polyvinylpyrrolidone grafted thereto
A body of a
polyethylene and a copolymer of polyethylene and polypropylene having
polyvinylpyrrolidone grafted thereto
A body of
polypropylene and a copolymer of polypropylene and polyethylene having
polyvinylpyrrolidone grafted thereto A body of polyethylene having
2-vinylpyrrolidone grafted thereto
A body of two
polyethylene polymers of different chain lengths having 2-vinylpyrrolidone
grafted thereto
A body of
polypropylene having 2-vinylpyrrolidone grafted thereto A body of two
polypropylene polymers of different chain lengths having 2-vinylpyrrolidone
grafted thereto
A body of a
copolymer of polyethylene and propylene having 2-vinylpyrrolidone grafted
thereto
A body of a
polyethylene and a copolymer of polyethylene and polypropylene having 2-
vinylpyrrolidone grafted thereto
A body of
polypropylene and a copolymer of polypropylene and polyethylene having 2-
vinylpyrrolidone grafted thereto
Mechanical Features
The mechanical
features of the device relate to properties conferred by the structural and/or
material features of the device.
The present
invention provides new material formulations intended to meet the specifications
of a durable, biocompatible device. The present device may be produced from
materials hitherto unknown for implants as long as the following material
features and requirements are met and that the materials have optimised
properties relating to:
• Mechanical,
chemical and physical stability and optimised tribological properties. • Good
biocompatibility.
• Resistance to
elevated temperature (sterilisation).
• Affinity to the
surrounding biological components.
• Dynamic
characteristics suitable for stress distribution.
Furthermore, as
stated supra, radiation allows grafting of polymers onto existing polymer
surfaces, resulting in new mechanical properties as well as new surface
properties. In this manner, the resulting modified polymer device can be
processed to meet the necessary requirements of durability and
biocompatibility. The surface of the device can subsequently be treated to
modify surface properties such as wetting ability and/or biocompatibility.
This surface
treatment can be performed by plasma treatment, chemical grafting or by a
combination of plasma treatment and chemical grafting.
The properties of
the new materials to be obtained by these cross-linking and grafting processes
are resistance to tear and wear, good compressibility and flexibility and
surface properties which will allow wetting with biological fluids, and/or
eventually allow growth of chondntic cells onto the prosthetic device
It is believed that
the surfaces of the device in contact with biological surfaces within the joint
will be subject to interactions resulting from fnctional resistance, since only
part of the sliding/rotating movement of the joint will take place by internal
movement of the device.
The surface
material should also be elastic in order to allow deformation of the shape
without damage to the continuity of the surface but should on the other hand
also secure stability of the overall shape of the device.
The inner matrix of
the device should be suitable for stress distribution such as materials being
pressure absorbent, having elongation properties and rigidity Preferably, the
device is composed of a single homogenous material or a combination of
materials having the surface properties mentioned above as well as the relevant
dynamic characteristics suitable for stress distribution Preferably, the device
comprises exclusively of solid or semi-solid non-metallic material.
Mechanical
properties for certain relevant polymers are described by Szycher (Szycher, M
(editor), sponsored by SPE, Society of Plastics Engineers, Inc Biocompatible
Polymers, Metals, and Composites, pp 725-727, 757-61).
Mechanical
properties of polymers are controlled by the elastic parameters, the three
moduli elastic, shear, and compressive moduli These parameters are
theoretically interrelated A modulus is the ratio between the applied stress
and the corresponding deformation The reciprocals of the moduli are called
compliancies The three elastic moduli have the dimension force per unit area,
(N/m2 or Pa) Polymers are not normally ideal elastic bodies,
but under load they show (time dependant) viscoelastic properties By taking the
load into consideration, the properties should be viewed according to this
dilemma Also, ideal elastic properties and ultimate properties, are influenced
by the viscoelastic properties.
Ultimate tensile
strength is a measure of the stress required to cause the material to rupture
in tension Ultimate elongation is the percent stretch of the material before it
ruptures in tension Elongation (%) is measured as
Elongation
(percent) = SB - S0 / S0 x 100
where SB =
observed distance between bench marks of the stretched specimen at rupture, and
S0 = the original distance between bench marks.
Table 1 - Elastic parameters and their definitions
Examples of ranges
of the mechanical properties of the device are mentioned below However, it
should be contemplated that not all of the following characteristics may be
fulfilled by the material of the prosthetic device since, as explained above,
the numerous properties of the material are theoretically interrelated
Accordingly, conflict in fulfilling all parameters within the stated ranges may
occur.
In one embodiment,
the prosthetic device according to the invention is a device wherein the
material of the device or at least the part of the device which exerts the
pressure distribution and/or the part which exerts the sliding/rotating
movement in the joint when the joint is loaded has/have one or more of the
following properties (under biological conditions (37°C, physiological
salinity)) A compressive modulus (K) of at least 2000 MPa, a shear modulus (G)
of at least 1 MPa and an elastic module (E) of at least 10 MPa.
Furthermore,
certain requirements to the material under stress with forces that ultimately
leads to disintegration can be expressed Based on the elasticity parameters for
the material, the properties of the material with respect to pressure
elongation, torsion and displacement in the range where the material responds
elastic can be estimated The ultimate limits should preferably be within ± 20%
of the range of elastic response As a consequence thereof, the limits for the
ultimate properties (ultimate compression strength, tensile strength, torsional
strength, shearing strength) can be derived Furthermore, the material should
have an "ultimate percentage elongation" of at least 20%.
The materials
according to the invention may be a "quasi elastic" material. Y.
Shikinami and H. Kawarada, Biomaterials 19, 1998, pp. 617-635, discuss that
many materials of biological origin, has a J-form in a stress vs strain curve,
whereas may synthetic materials has an S-form.
Preferably, the
critical surface tension (γc) values should be within the "zone of biocompatibility"
corresponding to the range of about 20-30 dynes/cm (as defined by Lelah M. D.,
Cooper, S.L., Polyurethanes in Medicine- CRC Press, Inc. Boca Raton, Florida,
pp. 59-62 and 92-93).
In one embodiment
of combined features, the diameter of the device is about 35 mm and the
thickness is about 5 mm and the material of at least a part of the device has
an ultimate percentage elongation of at least 20% corresponding to an ultimate
angle of twist of about 90°.
In another such
embodiment, the diameter of the device is about 35 mm and the thickness is
about 10 mm and the material of at least a part of the device has an ultimate
percentage elongation of at least 20% corresponding to an ultimate angle of
twist of about 90°.
In a further
embodiment, the diameter of the device is about 35 mm and the thickness is
about 10 mm and the material of at least part of the device has an ultimate
percentage elongation of at least 20% corresponding to an ultimate angle of
twist of about 180°.
Insertion
It is also an
object of the present invention to provide a method for introducing a device
according to the present invention into a joint. The method comprises:
a) locking the
device to an intra-articular component and thereby fixing or retaining the
device in the joint cavity in a manner which is substantially non-invasive with
respect to cartilage and bone natively present in the joint cavity. The method
may further comprise any of the following steps before locking the device to
the intra-articular component in the joint:
i) exposing the
joint capsule by conventional surgery procedures,
ii) penetrating the
joint capsule into the joint space leaving a passage for
iii) introducing
the prosthesis into the joint capsule via the passage, the prosthesis having a
shape suitable for being introduced through this passage.
Locking the device
to the intra-articular component and thereby fixing or retaining the device in
the joint cavity in a manner which is substantially non-invasive with respect
to cartilage and bone natively present in the joint cavity may include encircling
a ligament present in the joint with a ring-shaped element of the device such
as a ring-shaped device having a slit extending from the periphery of the
device to the central opening of the "ring".
The method may
further comprise the steps of deforming the prosthetic device into a reduced
volume or a slender shape before locking the device to the intra-articular
component.
In the case of
insertion into a hip joint, the insertion of the device is preferably performed
after penetration through the head of the rectus femoris muscle leaving a
passage having a substantial width for introducing means into the joint capsule
without alteration of the function of the capsule after the surgery.
Means or
instruments for inserting the device into the joint space can be in the form of
forceps comprising means for deforming the device into a minor volume or a more
slender shape and may comprise means for grasping around the intra-articular
component to which the device is capable of interlocking.
The forceps may
further comprise means for locking the device around or substantially around
the intra-articular component and optionally means enabling the forceps to be
withdrawn without withdrawing the device. Thus, a further object of the
invention relates to a kit comprising:
a) an
intra-articular prosthetic device for a joint having
a.1) a spacer
function and/or capability to exert pressure distribution and/or
sliding/rotating movement of the joint by an internal movement of the device by
means of a resilient member, and
a.2) a locking
mechanism adapted to fix the device to an intra-articular component by means of
an element of the device surrounding the component in such a manner that
displacement of the device is limited by inter-locking with the component; and
b) an instrument
for inserting the prosthetic device into a joint cavity.
Preferably, the
elements of the kit should be sterile.
The instrument b)
may further comprise one or more of the following means b.1 to b.4:
b.1 ) means for
deforming the prosthetic device into a reduced volume or to a slender shape and
keeping this volume or shape upon introduction of the device to the joint;
b.2.) means for
grasping or encircling the intra-articular component to which the element of
the prosthetic device is capable of inter-locking;
b.3.) means for
leaving the prosthetic device in the joint with the element of the prosthetic
device surrounding an intra-articular component; and
b.4.) means for
retracting the instrument from the joint.
It is contemplated
that each of the means of b.1.), b.2.), b.3.) and b.4.) may be connected to or
form part of a handle. Moreover, the resilient member of a.1) and the element
sur- rounding the intra-articular component of a.2) may constitute the
prosthetic device. The means of b.2.) for grasping or encircling the
intra-articular component may comprise an incision of the instrument which, in
situ, is able to substantially retain the element within the "legs"
of the incision.
Biological activity
of the device
When inserted in
the joint cavity the device is capable of alleviating the pain and other
symptoms related to damaged cartilage, such as improving movements.
Furthermore, the device may be capable of healing the sick bone's structure
and/or cartilage structure- in hole of partly.
For example the device
may facilitate creation of new cartilage and/or minimise destruction, such as
fibrillation and/or fragmentation, of cartilage by relieving the pressure on
the residual cartilage/bone in the joint.
Furthermore, the
device may comprise biological active additives. Medication or biological
active substances can be used as additive to the device to facilitate healing,
minimise destruction or with other therapeutic goals, such as pain relieve,
anti-inflammation, oncology treatments, stimulation of bone growth, and/or
anti-infectious agents. Also, biological osteogenic or chondrogenic, chondral
inductive, and/or chondral conductive materials may be added to the device. In
particular patients suffering from osteoporosis or other bone degenerating
conditions may benefit from having devices comprising osteogenic inductive
materials implanted.
The medication or
biological active substances can be used as additive to the device to
facilitate cell growth, such as osteocytes, osteoblasts, chondrocytes,
chondroblasts, mesenchymal cells. Cartilage inducing factor may for example be
the factors described in US 4,774,322 and US 4,843,063
The device itself
can be used as a growth medium and/or network for the natural or artificial
cells, such as chondrocytes.
The device is capable
of being formed to suit any joint cavity of animals or human beings, therefore
the device may for example be formed to fit into any one of the following
joints: Hip joint, knee joint, ankle joints, shoulder joint, elbow joints,
wrist, fingers, spinal column joints, such as for substituting intervertebral
discs, and the jaw joint.
BRIEF
DESCRIPTION OF THE DRAWINGS
Fig. 1 shows
a cross sectional perspective view of a human hip joint.
Fig. 2 shows
a cross sectional perspective view of the hip bone corresponding to Fig. 1.
Fig. 3 shows
a cross sectional perspective view of the human hip bone in which one
embodiment of a device 11 according to the invention is shown in situ.
Fig. 4 shows
a perspective view of the human hip joint in which the femoral head has been
retracted from the acetabulum.
Fig. 5 shows
a perspective view in which one embodiment of a device 11 according to the
invention is located in situ.
Fig. 6 shows
a cross sectional perspective view of an embodiment of the device according to
the invention disclosing a device having a globular shape.
Fig. 7 shows
an elevational perspective view of a spherically shaped device.
Fig. 8 shows
a cross sectional perspective view of a cup- shaped device.
Fig. 9 shows
a perspective view of a cup-shaped device according to the device shown in Fig.
8.
Fig. 10 shows
a cross sectional perspective view of another embodiment of a cup-shaped
device.
Fig. 1 1
shows an elevational perspective view of the embodiment of a device as shown in
Fig. 10.
Fig. 12 shows
a cross sectional perspective view of a ring-shaped device. Fig. 13 shows an
elevational perspective view of a ring-shaped device.
Fig. 14 shows
a cross sectional perspective view of a substantially disc-shaped embodiment of
the device.
Fig. 15 shows
a cross sectional perspective view of a ring-formed embodiment of the device
consisting of a substantially homogeneous material.
Fig. 16 shows
a cross sectional perspective view of a double ring-shaped embodiment of the
device.
Fig. 17 shows
a perspective view of an embodiment of a device comprising two ring- shaped
elements.
Fig. 18 shows
a cross sectional perspective view of an embodiment of the device in showing
vertical lines corresponding to grooves on the surfaces representing a slit.
Fig. 19 shows
an elevational perspective view of an embodiment of the device corresponding to
the one shown in Fig. 18.
Fig. 20 shows
a cross sectional perspective view of a device substantially similar to the one
shown in Fig. 17.
Fig. 21 shows
an elevational perspective view comprising a double ring having slits of the
upper part and the lower part (the rings).
Fig. 22 shows
a cross sectional perspective view of a curl-shaped embodiment of the device.
Fig. 23 shows
a sectional perspective view of an embodiment of the device comprising
curl-shaped element or a double ring.
Fig. 24 shows
a cross sectional perspective view of a ring-formed embodiment. Fig. 25 shows a
cross sectional perspective view of a ring-shaped element in which the hole or
passage of the ring is placed eccentrically.
Fig. 26 shows
a cross sectional perspective view of an embodiment of the device corresponding
to the one seen in Fig. 16.
Fig. 27 shows
a perspective view of an embodiment similar to the one shown in Fig. 26.
Fig. 28 shows
a cross sectional perspective view of a ring-shaped element, e.g. corresponding
to the lower part of the ring-shaped element seen in Fig. 27.
Fig. 29 shows
a perspective view of one embodiment of an instrument with the prosthetic
device located between the upper part of the instrument facing the surface
corresponding to the acetabulum in situ and the lower part facing the femoral
head.
Fig. 30 shows
a perspective view of the upper part of the instrument as shown in Fig. 29.
Fig. 31 shows
a sectional perspective view of an embodiment of the upper part of the
instrument comprising an edge or wall of a V-shaped incision.
Fig. 32 shows
a perspective view of the embodiment shown in Fig. 31 but seen from above.
Fig. 33 shows
a perspective view of an embodiment of the upper part of the instrument
comprising pushing means and means for securing the prosthetic device.
Fig. 34 shows
a perspective view of a scissors-like embodiment of an instrument suitable for
insertion of the device into the joint.
Fig. 35 shows a perspective elevational view of a hip joint wherein the femoral head has been retracted from the acetabulum giving space for the insertion of the device by use of an embodiment of the instrument according to the invention.
Fig. 36
shows a view similar to the one is Fig. 35 in which the insertion of the device
is taken place. The upper and lower part of the instrument now gradually opened
for delivering the device into the joint and to place the device around the
ligament.
Examples
A PROCEDURE
FOR PRODUCING A DEVICE ACCORDING TO THE INVENTION
Example 1
The device is
produced using compression molding. A preformed fibre network consisting of
polyethylene fibres (Dyneema®, DSM Holland) wetted with a plastomer of the
polyethylene type (Hostalen®, DSM Holland) is heated and compressed into the
shape of the finished device in an appropriate mold. The heating procedure ensures
that the plastomer flows together. The heating temperature is selected below
the melting temperature of the fibre crystallites in order not to loose the
crystallinity of the polyethylene fibres, ie. below 140 °C, and above the
melting temperature of the polyethylene plastomer, ie. in the range between
100-140 °C. Subsequent cross-linking of both fibres and plastomer is obtained
using treatment with accelerated electrons followed by annealing. As the
cross-linking process takes place in the amorphous polyethylene regions, the
optimal dose will depend on the fraction of amorphous polyethylene in the final
device. The optimal radiation dose is close to the gelation dose of
polyethylene and thus lie between 30 and 300 kGy (3-30Mrad). The purpose of annealing
is to eliminate long living free radicals by a heat treatment of 80°C for about
12 hours in vacuum. Subsequent surface grafting with polyvinylpyrrolidone is
obtained by irradiating the device surrounded by a solution of
polyvinylpyrrolidone, wherein the irradiation dose is in the range between 10
and 100 kGy. After the grafting procedure the device is washed with water to
remove ungrafted polyvinylpyrrolidone.
Example 2
The device is
produced as described in Example 1 , except that polyvinylpyrrolidone is
substituted with a solution of 2-vinylpyrrolidone.
Example 3
The device is
produced as described in Example 1 , except that polyvinylpyrrolidone is
substituted with a solution of a combination of polyvinylpyrrolidone and
2-vinylpyrrolidone.
A SURGICAL PROCEDURE
FOR INSERTION OF A PROSTHETIC DEVICE ACCORDING TO THE INVENTION INTO THE HIP
JOINT.
Antero-lateral
exposure of hip. Modified Smith-Petersen approach (Smith-Petersen M.N.;
Approach to and exposure of the hip joint for mold arthroplasty. J. Bone Joint
Surgery 1949; 31 A: 40)
Technique:
Position of patient: The patient may lie supine on the operation table.
Traction may be applied by use of bone traction in the femoral condyles, or by
soft tissue traction in a boot as used when osteosynthezising a proximal
femoral hip fracture. A counter extension may be applied by an external pin
placed on the symphysis. A small sandbag may be placed under the buttock of the
affected side to rotate the trochanter slightly forwards. Some may prefer the
postero-lateral approach with the patient in the lateral position, but the
approach may be more difficult with respect to reaching the teres ligament in
the hip joint.
Incision: The
incision forms an angle open anteriorly. Its upper limb begins 4 cm behind the
anterior superior spine of the ileum and extends obliquely backwards to the tip
of the greater trochanter. The lower limb of the incision extends vertically
downwards from the greater trochanter for 5 cm. The skin flaps are mobilised
from the underlying deep fascia, which is cleared of adherent adipose tissue.
The deep
exposure: When the deep fascia has been incised, the interval between the
tensor fascia latae muscle anteriorly and the gluteus medius posteriorly is
identified immediately proximal to the antero-superior corner of the greater
trochanter. This interval is widened by separating the fibres with dissecting
scissors and is continued proximally. Towards the crest of the ileum, the two
muscles are blended more closely and have to be separated by sharp dissection
with scissors. The space between the muscles is opened up by stripping part of
the muscle origins from the outer aspect of the wing of ileum. Closer to the
trochanter, the gluteus minimus may also be partly raised from the bone and
retracted posteriorly. In the lower half of the wound, the capsule of the hip
joint now comes into view with, immediately above it, the reflected head of the
rectus femoris muscle. The reflected head and the anterior part of the capsule
is to be preserved and is opened by an H-shaped incision and flaps turned
proximally and distally.
The maximal
traction is now performed. A space in the joint of 1.5 cm is needed. Relevant
elongation of muscles and tendons may be performed. Adduction tenotomy may be
performed by a small stab wound incision, whereas the rectus can be reached by
the antero-lateral approach.
The
grab-forceps with the hip joint device is now inserted, and the retractor may
help to catch the teres ligament of the head of femur.
The hip joint
must be tested to verify the stability of the hip joint device. The hip ring is
allowed to space the relaxed joint by 0.8-1.5 cm.
The capsule
is closed with two or three Vicryl sutures, after which the separated muscles
are likewise approximated with interrupted sutures. The skin is closed with
deep tension sutures and skin edge sutures. A suction drainage may be used
according to the circumstances.
DETAILED
DESCRIPTION OF THE DRAWINGS
Fig. 1 shows
a cross sectional perspective view of a human hip joint where the femoral head
1 is shown in connection with the femoral neck (collum femoris) by the joint
cavity 3 (cavum articulare). The joint cavity 3 is separated from the outside
by the joint capsule 4 (capsula articulare). From the femoral head 1 ,
ligamentum femoris 5 extends through the joint cavity 3 between the acetabulum
6 and the cartilage 7 covering the femoral head 1. Ligamentum femoris 5 is
anchored in the bone of the femoral head at one end and the ligament fibres are
attached to the acetabulum 8 which is part of the hip bone 6 (os coxae).
Fig. 2 shows
a cross sectional perspective view of the hip bone corresponding to Fig. 1. However, e.g. due to
damage of the femoral head, the cartilage is missing and the bone of the
femoral head is in direct contact with the acetabulum. Both the surface of the
acetabulum and the surface 9 of the femoral head 1 are damaged. The intact
ligamentum femoris 5 extends through the joint cavity 3.
Fig. 3 shows
a cross sectional perspective view of the human hip bone in which one
embodiment of a device 11 according to the invention is shown in situ.
Ligamentum femoris 5 extends from its attachment of the femoral head through
the device and is located between the acetabulum and the upper surface of the
device.
Fig. 4 shows
a perspective view of the human hip joint in which the femoral head 1 has been
retracted from the acetabulum 8. Ligamentum femoris 5 is anchored in the
femoral head at one end the other end is located in the acetabulum 8 of the hip
bone 6.
Fig. 5 shows
a perspective view in which one embodiment of a device 11 according to the
invention is located in situ covering the femoral head and surrounding
ligamentum femoris 5 which thereby extends through the device 11. When the
ligament is surrounded by the device, replacement of the device is prevented.
However, circular movement around the substantially central ligament is
possible.
Fig. 6 shows
a cross sectional perspective view of an embodiment of the device according to
the invention disclosing a device having a globular shape in which a tubular
passage 30 extends through the device 31. The passage extends along the central
axis from one pole to the opposite pole.
Fig. 7 shows
an elevational perspective view of a spherically shaped device having a central
tubular passage 30 extending through the device 33 and a slit 32 extending from
the outer surface of the device and through the body of the device into the
central passage 30. The slit may be curl-formed in the radial direction with
the axis of the tubular passage being the center.
Fig. 8 shows
a cross sectional perspective view of a cup- shaped device having a central
passage 34 extending from the convex upper part to the flattened bottom of the
device Fig. 9 shows a perspective view of a cup-shaped device according to the
device shown in Fig. 8. The device 37 has a slit 36 extending from the surface
of the device into the central passage 34 shown as a hole of the upper part of
the device.
Fig. 10 shows
a cross sectional perspective view of another embodiment of a cup-shaped device
39 having an upper convex surface and a lower surface 40 which is concave and
forms a half spherical cavity having a passage 38 which extends to the upper
convex surface of the device.
Fig. 11 shows
an elevational perspective view of the embodiment of a device as shown in Fig.
10. The slit 41 has a substantially S-shaped course which extends through the
device 42 from the centre to the periphery of the device.
Fig. 12 shows
a cross sectional perspective view of a ring-shaped device. The central part 44
is composed of a reinforced material compared to the rest of the device
material 45. The central surface 43 represents the part of the device in
contact with the ligament.
Fig. 13 shows
an elevational perspective view of a ring-shaped device in which the slit 46
has a substantially tongued course. Such a tongued course of the slit may
represent overlapping parts in a plane substantially perpendicular to an axis
through the central passage of the device. As appears from the figure, the slit
46 extends from the central hole to the outer periphery 47 of the device.
Fig. 14 shows
a cross sectional perspective view of a substantially disc-shaped embodiment of
the device showing the central passage 48 extending from the outer surface 49
through the device. A part of the central material 51 is shown as reinforced
compared to the rest of the material 50 of the device.
Fig. 15 shows
a cross sectional perspective view of a ring-formed embodiment of the device
consisting of a substantially homogeneous material 52. As shown, the periphery
of the device, where the upper and lower surface meet, is less rounded compared
to the corresponding central part 53. Fig. 16 shows a cross sectional
perspective view of a double ring-shaped embodiment of the device (a device
consisting of two units) having the overall shape of a cup comprising a cavity
corresponding to the lower surface which is in contact with the femoral head.
The upper ring 54 being smaller than the lower ring 55. The device may comprise
rings of different materials.
Fig. 17 shows
a perspective view of an embodiment of a device comprising two ring- shaped
elements. The upper ring 57 of the device may continue in the lower ring 58 around
the axis of the central hole 56. Accordingly, the device, having a slit which
has the course between the surfaces of the upper and the lower rings, can be
arranged around the ligament by a rotating movement until the ligament is
positioned in the centre of such curly device.
Fig. 18 shows
a cross sectional perspective view of an embodiment of the device in which the
vertical lines 70 represent top and bottom, respectively, of grooves forming a
zigzag- shaped slit extending in the radial direction from the central hole to
the periphery as well as from the upper to the lower surface of the device.
Fig. 19 shows
an elevational perspective view of an embodiment of the device corresponding to
the one shown in Fig. 18. The zigzag-shaped slit 71 has a substantially radial
direction.
Fig. 20 shows
a cross sectional perspective view of a device substantially similar to the one
shown i Fig. 17 in which the two ring-shaped elements 72 and 73 of the curl
together form an upper spherical surface fitting into the acetabulum and
comprising a lower cavity which is also of a spherical shape which fits on the
femoral head. The upper ring-shaped element 72 comprises a central passage for
the ligament which is thereby surrounded by the upper ring. The contact zone 74
constitutes part of the slit. In another embodiment each ring-shaped element
comprises its own separate slit whereby the device comprises separated rings.
Fig. 21 shows
an elevational perspective view comprising a double ring where 75 represents
the slit of the upper part 72 and 76 represents the slit of the lower part 73.
Both of the slits 75 and 76 have a substantially tongued course. Fig. 22 shows
a cross sectional perspective view of a curl-shaped embodiment of the device in
which the slits 77 and 77a extend through the entire device and contribute to
the curl-shape.
Fig. 23 shows
a sectional perspective view of a curl-shaped embodiment of the device or a
double ring in which the surfaces of the ring elements which are in contact
with each other have a surface pattern preventing the rings from sliding apart.
In the embodiment shown, the pattern is represented by circular grooves which,
as appears from the cross sectional view 78, fit into each other.
Fig. 24 shows
a cross sectional perspective view of a ring-formed embodiment of the device in
which the passage for the ligament is in the centre and in which the dimensions
of the cross section areas of the ring 79 are substantially the same.
Fig. 25 shows
a cross sectional perspective view of a ring-shaped element in which the hole
or passage of the ring is placed eccentrically and in which one part of the
ring in a cross section 81 differs in size from the corresponding part 80. The
specific dimensions of such a ring-shaped embodiment of the device may be individually
adapted in accordance with the anatomical conditions of the patient.
Fig. 26 shows
a cross sectional perspective view of an embodiment of the device corresponding
to the one seen in Fig. 16. However, in this embodiment the slit 82 extends
through each of the ring-shaped elements and furthermore, the surfaces
constituting the slit comprise grooves located in a substantially radial
direction which thereby forms a substantially zigzag course at the surface of
central passage for the ligament.
Fig. 27 shows
a perspective view of an embodiment similar to the one shown in Fig. 26. The
zigzag course of the slit 83, representing radially extending grooves which fit
into each other, is clearly seen at the outer surface of each of the ring
elements constituting the device. However, the grooves need not extend
completely from the inner to the outer surface of the device but may be present
in located areas only.
Fig. 28 shows a cross sectional perspective view of a ring-shaped element, e.g. corresponding to the lower part of the ring-shaped element seen in Fig. 27. The grooves 84 extend from the periphery into the centre 86 of the ring-shaped element 85.
Fig. 29 shows a perspective view of one embodiment of an instrument with the
prosthetic device 11 located between the upper part 21 of the instrument facing
the acetabulum (not shown) and the lower 22 part of the instrument having a
concave shape facing the femoral head 1. The prosthetic device 11 is placed
around the femoral ligament 5 when the upper 21 and lower 22 parts of the
instrument are allowed to open by operating the handle 24 connected to the part
21 and the handle 23 connected to the part 22. As appears from the drawing, the
handles 23 and 24 may be moved relatively to a common axis.
Fig. 30 shows
a perspective view of the upper part of the instrument as shown as 21 in Fig.
29 with a view into the concave surface facing the convex surface of the lower
part 22 shown in Fig. 29. Means for pushing 19 are shown which in one
embodiment substantially have the shape of a stirrup where the base pushes the
prosthetic device towards the means 20 for opening the slit of the prosthetic
device. The means 20 comprises a V-shaped incision 25 having elevated edges
forming a wedge which forces the slit of the prosthetic device to open when the
prosthetic device is pushed towards the wedge by the base portion of the means
19. The slit of the prosthetic device is gradually widening while being pushed
by 19 towards the means 20 whereby the prosthetic device can be placed around the
ligament which is fixed within the incision 25 of the instrument. The incision
25 is shown as V-shaped, however any other shape allowing the ligament to be
situated in the slit is within the scope of the invention. The means 20
encompass any embodiment suitable for placing the device around the ligament,
accordingly, the means could include a spring which separates the mating
surfaces of the slit. The upper part 21 in Fig. 29 of the instrument may also
comprise two moveable parts which together substantially form a concave cavity
mating the lower part of the instrument shown as 22 in Fig. 29. The movable
parts may furthermore form an incision 25 by having parts separated from each
other. In addition, the movable parts may be able to overlap and may comprise
fastening means for the prosthetic device, e.g. for each side of the slit, so
that when the movable parts are moved apart, the slit of the device is forced
to open allowing the device to be placed around the ligament. In a still other
embodiment, the inner surface of the upper part of the instrument 13 comprises
means for opening the slit of the prosthetic device which is operated
separately, e.g. in form of a string or wire connected to the device on each
side of the slit so that the slit can be opened by pulling the string. A
suitable direction of the pull can be secured, e.g. by fastening the string to
a suitable point at the periphery of the concave cavity 13, e.g. by letting the
string to pass through an eyelet. The means 19 as well as any string or wire
may be operated by means extending through the handle 18.
Fig. 31 shows
a sectional perspective view of an embodiment of the upper part of the
instrument comprising an edge or wall of a V-shaped incision 12 of the inner
surface 13. Pushing means 14 are connected to a handle 15 positioned within the
handle 16 of the upper part of the instrument as also shown. The pushing means
14 have a base portion which is adapted to the shape of the prosthetic device.
Fig. 32 shows
a perspective view of the embodiment shown in Fig. 31 but seen from above. The
incision 25 enables the instrument to be placed in the joint without impeding
the function or anchoring of ligamentum femoris as this is situated between the
"legs" of the incision.
Fig. 33 shows
a perspective view of an embodiment of the upper part of the instrument in
which the pushing means 27 comprise means 28 for securing the prosthetic
device. The means 28 have the shape of a hook located on each leg of the
pushing means which are adapted to guide the prosthetic device. The prosthetic
device is placed so that the outer or distal opening of the slit corresponds to
the incision 25 of the instrument, the hook 28 on each side may then be secured
to the device on the corresponding side of the slit. Preferably, in this
position, the slit is open to receive the ligament. When the handle 26 is
pushed towards the incision where the ligament is placed, the prosthetic device
will be placed around the ligament, and the slit may then allow to close as the
hook on each side (holding the device) let go when the pushing means are moved
further on. As appears from Fig. 33, the pushing means may be operated by a
part located within the outer handle of the upper part of the instrument which
thereby functions as a guide.
Fig. 34 shows a perspective view of a scissors-like embodiment of an instrument where 21 represents the upper part and 22 the lower part of the instrument. The prosthetic device is placed between those parts when inserted into the joint. Incisions as well as pushing means as described for the embodiments above may also be present.
Fig. 35 shows a perspective elevational view of a hip joint.
The femoral head 1 has been retracted from the acetabulum 8 giving a space in
the joint of approximately 1-2 cm. The outer surface of the upper part of the
instrument 17 having a handle 24 is placed on the femoral head 1. The lower
part of the instrument (not seen) is present within the upper part 17, the
ligament 5 is located in the corresponding incisions (not seen) of the lower
and upper part 17 of the instrument.
Fig. 36 shows
a view similar to the one is Fig. 35 in which the handle 23 of the lower part
of the instrument is now seen above the handle 24 of the upper part 17 of the
instrument. The prosthetic device located between the upper and lower part 22
of the instrument may now be pushed towards the ligament 5 as the upper and
lower part 22 of the instrument are now let open by operating the handles 23
and 24.
1. A prosthetic device for insertion into a joint cavity of a joint of a
vertebrate, such as a human, said device consisting of a biocompatible material
comprising at least a first polymeric component and a second polymeric
component, wherein the chain length of the first polymeric component is longer
than the chain length of the second polymeric component.
2. The prosthetic device according to claim 1 , wherein the first polymeric
component has a carbon-backbone.
3. The prosthetic device according to claim 1 or 2, wherein the first
polymeric component and the second polymeric component are compounded to form a
bidispergent system.
4. The prosthetic device according to claim 1 , wherein the first polymeric
component is selected from polyacrylates, polystyrene, polyethers,
polytetrafluorethylene, polyvinylalcohol, polyethylene, and polypropylene.
5. The prosthetic device according to any of the preceding claims, wherein
the second polymeric component is selected from polyacrylates, polystyrene,
polyethers, polytetrafluorethylene, polyvinylalcohol, polyethylene, and
polypropylene.
6. The prosthetic device according to any of the preceding claims, wherein
the second polymeric component is cross-linked.
7. The prosthetic device according to any of the preceding claims, wherein
the first and the second polymeric component comprises the same monomeric
component.
8. The prosthetic device according to any of the preceding claims,
comprising a third polymeric component, said third polymeric component being
different from the first and/or the second polymeric component.
9. The prosthetic device according to claim 8, wherein the third polymeric
component is selected from polyethylene oxides, and polyvinylpyrrolidon.
10. The prosthetic device according to any of the preceding claims 8 or 9,
wherein the third polymeric component is grafted to the first and/or the second
polymeric components.
11. The prosthetic device according to any of the preceding claims, wherein
the chain length of the first polymeric component is above 100 monomer units.
12. The prosthetic device according to claim 1 , wherein the first
polymeric component comprises a copolymer of polyethylene and polypropylene,
and the second polymer is grafted to the first polymer.
13. The prosthetic device according to claim 1 , wherein the first
polymeric component is a cross-linked polymer, and the second polymer is grafted
to the first polymer.
14. The prosthetic device according to claim 12, wherein the second
polymeric component is selected from polyethylene oxides, and
polyvinylpyrrolidon.
15. A prosthetic device for insertion into a joint cavity of a vertebrate
such as a human, wherein the body of the device comprises a polymer material,
and wherein the device comprises a hole extending through the body of the
device.
16. A prosthetic device according to claim 2, wherein the device further
comprises a slit in the body of the device extending through the body of the
device from the surface of the body to the hole.
17. A prosthetic device according to claim 2, wherein the device further
comprises a means of enabling a passage through the body of the device to the
hole.
18. A prosthetic device according to any of the preceding claims, wherein
said device is adapted to alleviate conditions associated with worn cartilage
by providing a spacer function and/or to exert pressure distribution in the
joint when the joint is loaded and/or to provide at least part of the
sliding/rotating movement of the joint by internal movement of at least part of
the device.
19. A prosthetic device according to any of the preceding claims, wherein
the device is capable of locking itself to an intra-articular component and
thereby being fixed or retained in the joint cavity in a manner which is
substantially non-invasive with respect to cartilage and bone natively present
in the joint cavity.
20. A prosthetic device according to any of claims 1 or 2, wherein the
polymer material is obtained by cross-linking polyethylene, polypropylene or
polyvinylpyrrolidone or combinations or co-polymers thereof.
21. A prosthetic device according to claim 7, wherein the cross-linking is
achieved with radiation.
22. A prosthetic device according to claim 8, wherein the forms of
radiation are selected from the group comprising high-energy electrons, gamma
rays, photons, microwaves, and thermal radiation.
23. A prosthetic device according to any of the preceding claims, wherein
the polymer material meets mechanical properties in that the E modulus (Young's
modulus) is at least 10 MPa.
24. A prosthetic according to any of the preceding claims, wherein the
device comprises more than one more unit.
25. A prosthetic device according to claim 11 , wherein the units are
adapted not to 25 interfere with intra-articular components when the device is
in the joint cavity.
26. A prosthetic device any of the according to claim 11 , wherein the body
of the unit further comprises a hole extending through the body of the device.
27. A prosthetic device according to claim 13, wherein the body of the unit
further comprises a slit extending from the surface of the body to the hole.
28. A prosthetic device according to any of the preceding claims, wherein
the polymer is subjected or further subjected to surface treatment to obtain
optimised wetting ability and 35 to obtain biocompatibility and resistance to
heat treatment for sterilisation.
29. A prosthetic device according to claim 15, wherein the surface
treatment results in a material with critical surface tension (γc) values within the "zone of
biocompatibility" of 20- 30 dynes/cm.
30. A prosthetic device according to any of the preceding claims, which is
capable of locking itself to the intra-articular component by at least one
element of the device surrounding the component in such a manner that
displacement of the element is limited by interlocking with said component.
31. A prosthetic device according to claim 30, wherein the element
completely or substantially completely surrounds an intra-articular component
being a ligament.
32. A prosthetic device according to any of the preceding claims, which
device, when 15 present in situ, comprises at least one ring-shaped element.
33. A prosthetic device according to any of the preceding claims for the
articulation of a hip of a human, which device is adapted so that it, when
present in situ in the human hip joint cavity, comprises at least one element
surrounding ligamentum capitis femoris.
34. A prosthetic device according to any of the preceding claims, in which
the element which is adapted to surround the ligament when present in situ, has
such a shape and such properties that it can be placed around the ligament and,
when placed around the ligament, will stay interlocked with the ligament.
35. A prosthetic device according to any of the preceding claims which is a
hip endoprothese and wherein the element has a shape and properties permitting
arranging the element around ligamentum capitis femoris.
36. A prosthetic device according to any of claims 30-35, wherein the
element, when present in situ, permits the ligament to extend through the
element and substantially exert its natural function on the joint.
37. A prosthetic device according to any of the preceding claims, having
such shape 35 and/or properties that it is capable of replacing or
supplementing worn or damaged cartilage in the joint and/or is capable of
preventing wear of the native cartilage of the joint.
38. A prosthetic device according to any of claims 30-36, wherein the
element 5 surrounding the intra-articular component constitutes the device.
39. A prosthetic device according to any of the preceding claims wherein
the shape of the device mating the load bearing part of the joint is
substantially circular.
40. A prosthetic device according to claim 39, wherein the diameter of the
device in situ and when the joint is loaded is such that it substantially covers
the surface area of the load bearing part of the joint which in the normal
joint is covered with cartilage.
41. A prosthetic device according to claim 40, wherein the joint is the hip
joint, and 15 wherein the diameter of the device is such that the surface of
caput femoris is substantially covered when the joint is loaded.
42. A prosthetic device according to claim 39, wherein diameter of the
device is between 15-80 mm, such as between 25-70 mm, preferable between 30-60
mm, more preferable between 35-50 mm, most preferred about 40 mm, when the
joint is loaded.
43. A prosthetic device according to any of the preceding claims, wherein
the thickness of the device is between 2-60 mm, such as between 6-40 mm,
preferable 8-30 mm, more preferable about 10-20 mm, most preferable about 15 mm
in the unloaded stage.
44. A prosthetic device according to any of the preceding claims, wherein
the device comprises parts overlapping each other.
45. A prosthetic device according to claim 44, wherein the overlapping parts,
on their 30 mating surfaces have an interlocking surface structure.
46. A prosthetic device according to claim 45, wherein the interlocking
surface structures constitute grooves.
47. A prosthetic device according to claim 46, wherein the interlocking
surface structures are grooved in a radial direction.
48. A prosthetic device according to claim 46, wherein the interlocking
surface structures 5 are grooved in a circular direction.
49. A prosthetic device according to claim 45, wherein the interlocking
surface structures constitute elevations and corresponding depressions.
50. A prosthetic device according to any of the preceding claims, wherein
the E modulus (Young's modulus) of the material of at least part of the device
is at least 10 MPa, such as at least 13 MPa, preferably at least 16 MPa, more
preferable at least 19 MPa, still more preferable at least 22 MPa, most
preferable at least 25 MPa, such as at least 30 MPa or 50 MPa.
51. A prosthetic device according to any of the preceding claims, wherein
the material constituting the device comprises polypropylene, preferably
cross-linked polypropylene.
52. A prosthetic device according to claim 32, wherein the ring-shaped
element has a 20 shape of a horseshoe, a torus, or a curl.
53. A prosthetic device according to claim 52, wherein the ring-shaped
element has an upper convex shape and a lower concave shape.
54. A method for introducing a prosthetic device into a joint comprising
locking the device to an intra-articular component, thereby fixing or retaining
the device in the joint cavity in a manner which is substantially non-invasive
with respect to cartilage and bone natively present in the joint cavity.
55. An instrument for inserting a prosthetic device according to any of
claims 1-53, comprising means for deforming the prosthetic device into a
reduced volume or a slender shape and means for grasping the intra-articular
component to which the device is capable of interlocking.
56. The use of a prosthetic device for establishing slidability and/or
distributing pressure in a joint of a vertebrate such as a human, by inserting
into the joint cavity of the joint a prosthetic device, preferably a prosthetic
device as defined in any of the claims 1-53, capable of locking itself to an
intra-articular component and thereby being fixed or retained in the joint
cavity in a manner which is substantially non-invasive with respect to
cartilage and bone natively present in the joint cavity.
57. A method for establishing slidability and/or pressure distribution in a
joint of a vertebrate such as a human, comprising inserting into the joint
cavity of the joint, a prosthetic device, preferably a prosthetic device as
defined in any of the claims 1-53, which is capable of locking itself to an
intra-articular component and thereby being fixed or retained in the joint
cavity in a manner which is substantially non-invasive with respect to
cartilage and bone natively present in the joint cavity.
58. A kit comprising:
a) an intra-articular prosthetic device for a joint having
a.1) a spacer function and/or capability to exert pressure distribution
and/or 20 sliding/rotating movement of the joint by internal movement of the
device by means of a resilient member, and
a.2) a locking mechanism adapted to fix the device to an intra-articular
component by means of an element of the device surrounding the component in
such a 25 manner that displacement of the device is limited by inter-locking
with the component; and
b) an instrument for inserting the prosthetic device into a joint cavity.
59. The kit according to claim 58 wherein the instrument of b) comprises
one or more of the following means b.1 to b.4:
b.1.) means for deforming the prosthetic device into a reduced volume or to
a slender shape and keeping this volume or shape upon introduction of the
device to the joint,
b.2.) means for grasping or encircling the intra-articular component to
which the element of the prosthetic device is capable of inter-locking,
b.3.) means for leaving the prosthetic device in the joint with the element
of the prosthetic device surrounding the intra-articular component.
60. A kit according to claim 58 or 59, wherein the instrument further
comprises a handle.
61. A kit according to claim 59, wherein one or more of the means of b.1.),
b.2.), and b.3.) are connected to or forms part of a handle.
62. A kit according to any of claims 58-61 , wherein the resilient member
of a.1) and the element surrounding the intra-articular component of a.2)
constitutes a solid prosthetic device.
63. A kit according to any of the claims 58-62, wherein the intra-articular prosthetic device is as defined in any of the claims 1-53.
External links
Pedersen WB, Steenstrup FR, Olsen OI, Jakobsen LD,
Vraa E, Lauritzen JB, Bechgaard K. A prosthetic device. WO2001045595A2 December 14, 2000. 2001. patents.google
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2001PedersenWB_BechgaardKA
Authors & Affiliations
Walther Batsberg Pedersen, Copenhagen (DK)
Frederik Resen Steenstrup, Copenhagen (DK)
Ole Ingemann Olsen, Charlottenlund (DK)
Lene Diness Jakobsen, København (DK)
Erik Vraa, København (DK)
Jes Bruun Lauritzen, Farum (DK)
Klaus Bechgaard, København (DK)
Keywords
ligamentum capitis femoris, ligamentum teres, ligament of head of femur, endoprosthesis, prosthesis, invention, unipolar, subtotal
NB! Fair practice / use: copied for the purposes of criticism, review, comment, research and private study in accordance with Copyright Laws of the US: 17 U.S.C. §107; Copyright Law of the EU: Dir. 2001/29/EC, art.5/3a,d; Copyright Law of the RU: ГК РФ ст.1274/1.1-2,7
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