Prosthetic spinal disc and related methods

Abstract

An intervertebral disc prosthesis including a core of elastomeric material provided within an inner component of fabric. The inner component is provided with an outer component of fabric. By providing a smooth inner contact surface between the inner component and the core, movement between the inner and outer components is facilitated in preference to movement between the inner component and core. Core abrasion is thus avoided. The use of an inner component and an outer component also means that the characteristics of each can be optimized to meet different aims. The elastomeric core is provided with an additive to enhance radiopacity under medical imaging.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein:

FIG. 1 is a plan view of a core suitable for use in the present invention;

FIG. 2 is a cross-sectional front view of the core of FIG. 1;

FIG. 3 is a cross-sectional side view of the core of FIG. 1;

FIG. 4 is a plan view comparing the profile of a core according to the invention with a natural disc;

FIG. 5 illustrates an inner jacket according to the present invention, prior to assembly;

FIG. 6 illustrates an outer jacket according to the present invention, prior to assembly;

FIG. 7 illustrates an outer jacket according to another embodiment of the present invention, prior to assembly;

FIGS. 8 a, 8b and 8c show respectively an assembled disc outer, disc outer in plan view and disc outer in combination with core;

FIGS. 9 a, 9b and 9c show respectively an assembled disc outer with an inner, annular reinforcement, the disc outer in plan view and the disc outer in plan view with the inner annular reinforcement and core;

FIG. 10 a and 10b show respectively an assembled disc outer with inner reinforcement and core and plan view of the same;

FIG. 11 a illustrates a further embodiment, of the outer jacket prior to assembly;

FIG. 11 b illustrates the embodiment of FIG. 11a in assembled format in a plan view;

FIG. 11 c illustrates the embodiment of FIG. 11a in assembled, perspective view;

FIG. 12 a illustrates a view of an embodiment of an inner reinforcement, prior to assembly;

FIG. 12 b illustrates the outer of FIG. 12a in assembled form, in plan view;

FIG. 12 c shows the inner of FIG. 12a in assembled form, and contained within an outer jacket;

FIG. 13 shows a still further embodiment of an outer jacket, prior to assembly;

FIG. 14 a shows an embodiment of a disc outer potentially assembled from a disc outer according to FIG. 13;

FIG. 14 b shows an assembled disc outer with buttress elements, potentially formed from an outer jacket according to FIG. 13;

FIG. 14 c shows an assembled disc outer with buttress elements, potentially formed from an outer jacket according to FIG. 13;

FIG. 14 d is a perspective view of an assembled outer jacket including the buttress elements;

FIG. 15 a shows another embodiment of an outer jacket, prior to assembly;

FIG. 15 b shows the embodiment of FIG. 15a, with certain sections highlighted;

FIG. 16 illustrates an assembled outer jacket according to one form, left hand side, and according to another form, right hand side;

FIG. 17 illustrates the use of two assembled discs, with outer jackets according to the another form of FIG. 16, between adjacent vertebrae; and

FIG. 18 illustrates in a closer view the use of two assembled discs, with outer jackets according to the another form of FIG. 16, between adjacent vertebrae.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decision must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The method of inducing ischemia according to the present invention will be discussed in detail below with respect to its exemplary utility in treating cancer. However, it will be appreciated by those skilled in the art (and is within the scope of the present invention) that the methodology of the present invention may also find use in removing organs as method of treatment or for transplant and/or draining and subsequent reduction and isolation of an organ for removal or for an organ to maintain its contents for removal. The prosthetic spinal disc disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination.

The prior art contains examples of elastomeric discs, with the motion of the elastomer being contained by bonding it to metallic end-plates. In use, this results in high strains at the exterior faces of the disc and this in turn can give rise to tearing and eventually failure of the core.

The previously developed artificial intervertebral disc detailed in U.S. Pat. No. 6,093,205, was developed particularly for the cervical region of the spine. The combination of an elastomeric inner core surrounded by a single embroidered outer textiles jacket has been shown to offer particular benefit in terms of the encapsulation preventing the initiation or propagation of any fissures in the elastomer component of the artificial disc.

To provide an optimized artificial disc for use in the lumbar region of the spine a number of further developments and improvements have been made. The artificial disc may act as a complete disc replacement, or a partial replacement, for instance for the nucleus. Anterior or posterior insertion is possible. The further developments and improvements are also useful in the context of other disc prostheses too.

Firstly the core design has been designed specifically to provide optimal performance in the context of the lumbar region. FIG. 1 represents a plan view of the core, in effect looking down on the disc as positioned in the spine, with the anterior top and posterior bottom in the figure. The core is octagonal with a greater width (left to right in the figure) than depth (top to bottom). The sides 10 are planar with rounded corners between them. The core is made of a long term implantable grade silicone material. A 50° Shore hardness material is preferred. FIG. 2 is a cross-sectional view along axis A-A of FIG. 1 and hence is a view of the posterior half of the core viewed from the anterior side. The planar upper surface 12 and lower surface 14 are visible. FIG. 3 is a cross-sectional view along axis B-B of FIG. 1 and hence shows the transition from anterior to posterior side. As can be seen, the thickness at the anterior edge 16 is less than the thickness at the posterior edge 18. Both upper 20 and lower 22 sides of the core increase symmetrically in thickness relative to the centerline of the core X-X during the transition from anterior edge 16 to posterior edge 18.

The plan profile 40 of the optimized core design is seen in comparison with the plan profile 42 of the natural disc it is intended to replace in FIG. 4. The naturally curved shape of the disc has been squared off in to an octagonal design. This allows easier design of the embroidery element of the disc. Additionally the anterior to posterior length, AP dimension, is reduced compared with the natural disc so as to keep the artificial disc away from the great vessels. When anchoring the device, as described in more detail below, centrally located anchoring on the anterior face, position X, of the vertebrae is avoided, with a preference for anchoring on the adjacent sides, positions Y.

Various alternative constructions of the core around this basic principle can be used. The core could be constructed as a single piece, in a manner such as that suggested above. Alternatively, particularly where minimally invasive surgery is required, the core may be formed of multiple core pieces which are inserted and assembled to form the overall core in-situ. Such core pieces can be individually inserted and assembled within a single inner jacket, but more preferably are individually wrapped in inner jackets which are then maintained in position by a single outer jacket.

In more varied forms, the core can be formed of potentially tens or hundreds of small beads. The inner jacket would serve to maintain these in position. Cores formed of elastomer or hydrogel with elastomeric properties are also possible. As alternatives to the illustrated octagonal shape, hexagonal or rounded shapes can be used.

Around the core, an inner jacket is provided. This may be embroidered and/or woven. This is separate from a subsequent outer jacket. The inner jacket provides complete encapsulation of the core. As shown in FIG. 5, the jacket is in the form of a first side wall 50a which is connected to a top wall 51 and bottom wall 52. The first side wall 50a is connected to a second side wall 50b in a first direction. In a second direction, the first side wall 50a is connected, in sequence to a third side wall 50c, fourth side wall 50d, fifth side wall 50e, sixth side wall 50f, seventh side wall 50g and eighth side wall 50h. These side walls are stitched to the top wall 51 and bottom wall 52 so as to give an octagonal box form to the inner jacket and close completely around the core.

The material used for the inner jacket uses densely packed fibers to define as smooth a surface as possible for the fabric. This is particularly desirable for the inner surfaces which contact the core. This ensures the most uniform contact surface area between the inner jacket and the elastomer core.

Connected to the eighth side wall 50h is the first of a series of additional elements also formed from the same embroidery. These additional elements, in sequence 55b, 55a, 55c, 55d, 55e, 55f, 55g and 55h are wrapped around the side walls 50 of the assembled inner jacket. As a result they form an additional ring of material around the side of the core. In effect this extra band of material strengthens the ability of the inner jacket to act as a natural annulus would and resist expansion sideways by the core when placed under compressive load. The additional elements can be secured with further stitching. The additional elements 55 could of course be provided by a suitably configured, but separate element to the element providing the walls 51, 52, 50.

The side walls 50 and additional elements 55 are provided with a length and height pattern intended to define an inner jacket which matches the length and height variation pattern of the core.

An inner jacket provided in this way offers at least two key benefits. Firstly it allows the jacket in contact with the core to have relatively low movement levels, whilst still enabling the overall desired level of movement for the artificial disc due to the outer jacket's presence and design. Low movement levels for the inner jacket mean that abrasion of the core is minimized. A single jacket would not achieve this.

Secondly, the inner jacket can be designed with properties ideal for its purpose, whilst allowing the outer jacket to be designed with properties ideal for its purpose. Thus the inner jacket aims to provide as dense and hence smooth a fabric surface as possible in contact with the core. In this way the risk of individual fibers protruding relative to the others is reduced. Protruding fibers can potentially cause wear due to the micro-motion of the jacket against the core in use. This is a particular potential issue in the context of the high loads encountered in the lumber region. Whilst such properties are desirable here, they are not consistent with those found to be desirable for the outer surface/outer jacket of the artificial disc. Using two separate jackets allows better optimization in each case.

In a modified embodiment of the inner jacket, its properties may be tailored to facilitate tissue in-growth into the space between the inner jacket and the core. The formation of a layer of tissue directly between the jacket and the core of the disc should be beneficial in reducing still further wear in the device. Because the dense fiber form used to provide the most smooth surface contacting the core is not the most conducive to tissue in-growth, the make up of the inner jacket may be carefully controlled to assist.

By forming the inner jacket with a portion of the fibers or material formed of bio-absorbable material, as tissue in-growth occurs the inner jacket can be partially absorbed to provide further room for the in-growth. The non-bioabsorbable material of the inner jacket serves to provide the required structure for the inner jacket over its lifetime, supplemented by the assistance provided by the tissue itself. The use of quickly, moderately and slowly absorbed biomaterials in conjunction with non-absorbable materials can provide a gradual transition from the desired function being provided by the inner jacket alone to the point where it is shared between jacket and tissue. In some cases, an entirely bio-absorbable inner jacket may be provided. Various distributions for the non-absorbable and bio-absorbable material are possible in the inner jacket. The non-absorbable material may particularly form the outside of the inner jacket.

In addition to the core and inner jacket, an outer jacket is provided. A suitable outer jacket is illustrated in FIG. 6. This is intended to substantially surround the inner jacket. The outer jacket has a bottom wall 60 and top wall 62, which are connected by side wall 64a. Further side walls 64b, 64c are provided to one side of side wall 64a. Further side walls 64d, 64e are provided to the other side of side wall 64a. Attached to the top wall 62 is a sixth side wall 64f. The top, bottom and side walls are connected to one another by stitching. This leaves two sides of the outer jacket open, in effect the openings defined by edges 66 in one case and 68 in the other.

The edge 66 of the bottom wall 60 is provided with a flange 70. This has a hole 72 in it. The edge 66 of the top wall 62 is provided with a flange 74 which is thinner than flange 70, so as to be able to pass through the hole 72 in flange 70. Similarly, the edge 68 of the bottom wall 60 is provided with a flange 76. This has a hole 78 in it. The edge 68 of the top wall 62 is provided with a flange 80 which is thinner than flange 76, so as to be able to pass through the hole 78 in flange 76. To close the remaining two sides, therefore, flanges 70 and 74 and flanges 76 and 80 are interdigitated.

The flanges 70, 74, 76 and 80 are all significantly longer than the height of the disc space the artificial disc is to be used in. As a result the ends 82 of the flanges 70, 74, 76, 80 can be anchored to the vertebra above the disc replacement in the case of flanges 70 and 76 and to the vertebra below the disc replacement in the case of the flanges 74, 80.

A similar outer jacket to that illustrated in FIG. 6 is provided in FIG. 7. In this case, bottom wall 100 is connected to the top wall 102 by means of side wall 104. Further side walls 106 are provided. Two flanges 108 are provided connected to the top wall 102. These flanges are provided with a hole 110 in each case which is intended to receive the fixing used to collect the device to the spine. These holes are provided towards the ends of the flanges. Close to the top wall 102 two further holes 112 are provided. These have the inner flanges 114 which are connected to the bottom wall 100 passed through them in use (see FIG. 8a). These flanges are also provided with holes 110 to receive fixings in use.

In its assembled form, such a disc outer can appear as shown in FIG. 8a. Here the flanges 114 are clearly shown as interdigitated with the flanges 110 by virtue of their being passed through the holes 112 therein. The completed structure formed by the bottom wall 100, top wall 102, side wall 104 and further side walls 106, together with the flanges, totally encloses the core. Once again, an octagonal plan view is provided (FIG. 8b) with a similarly shaped octagonal core 116 provided therein (FIG. 8c). The core 116 in this case, as with the previous embodiments, is generally centered within the outer jacket.

In the embodiment of FIGS. 9a, 9b and 9c, an additional ring of material is provided around the core, inside the outer jacket 118 by an inner 120. vIn practice, this provides additional strength to the device when resisting lateral expansion when the core is compressed, i.e. into or out of the paper in the plan view shown in FIG. 9c.

The FIG. 9a embodiment shows in perspective view the overall assembly consisting of the outer jacket, inner reinforcement and core. In this case an additional annular reinforcement 122 is provided.

The FIG. 11a embodiment of the invention provides for a similar outer jacket to that described in FIG. 7 above. However, in this case the side walls 106 are extended by a very substantial amount via a series of additional elements 200a, 200b, 200c etc. A large number of repeats of these additional elements are provided, a number too great to be shown on the FIG. 11a drawing sheet. This device is assembled by folding the additional elements, starting at one end, so as to form a spiral of generally octagonal outline. The result is shown in FIG. 11b where a spiral 202 is formed extending from the very center of the device 204, out to its outer wall 206. Such a spiral can provide the core itself, or additional core material can be provided between the turns of the spiral, for instance hydrogel or other material which can be caused to flow into the device and then allowed to set. In FIG. 11c, an interdigitated, assembled form of the device of FIG. 11a and FIG. 11b is shown. The spiral core forms the core function for this device, as well as providing substantial reinforcement against expansion when the device is placed under compression. In effect the spiral provides the core, inner component and outer component in this embodiment.

In FIG. 12a, an unassembled form for the inner component is provided, including top wall 220, bottom wall 222, side walls 224 and a large number of additional elements 226a, 226b etc. Once again, these additional elements can be folded so as to provide an octagonal spiral core with the walls 224, 220 and 222 completing the exterior 228 of this inner component. This in turn is received within an outer component 230, the assembled form for which is shown in FIG. 12c. Again, the folded additional elements may form the core on their own or together with other core material, such as hydrogels. Again, a core structure of this type provides substantial resistance to sideways expansion when the device is placed under compression. In the FIG. 13 and FIG. 14a to 14d illustrations, a form of device is provided in which the center of the core is correctly located in the center of the disc space it is to be provided in. This is achieved by the use of a buttress zone formed in the device. This structure for the device allows the fixation flanges, with their interdigitation, to be flush with the anterior surface of the vertebral bodies, but still allow the disc itself to sit recessed by at least 4 mm within the disc space. Correct centering of the core, acting as the replacement, is thus provided. Additionally, such replacement reduces the risk of the main body of the device being pinched by the anterior lip of the vertebrae as the spine is flexed.

While it is possible to form the buttress from an entirely separate component, such as a folded fabric, in the preferred format, it is formed from a series of further elements 300-309. In effect, side walls are provided on the left hand side of the device, as seen in the simple plan view in FIG. 14a by means of the panel L8, L7, L6 and L4. The right hand side is provided by panels R2, R3. The further elements 300-309 are folded to form the buttress structure. A variety of configurations are possible, but in the illustrated form of FIG. 14b, the first part of the buttress is formed by panel 300 which extends inside the outer profile of outer jacket from the edge formed by the contact of panel R3 and L4. Further element 302 extends across the end of panel L5, further element 303 across the inside of panel L6. The further element 304 is then folded back across the inside of further element 303, with further element 305 being across the inside of further element 302. Similarly, further element 306 is provided across the inside of further element 300, before there is a further fold so as to provide further element 307 across the inside of further element 306. Further element 308 is provided across the inside of further element 305 with further element 309 being provided across the inside of the further element 304. Further folds of material can be provided if needed.

An alternative format for the buttress structure, formed in a similar way, is shown in FIG. 14c. Here, further elements provided at one end of the outer jacket form the inner-most further elements 400, 401 and 402. Further elements provided between there and the outer wall 405 of the outer jacket are provided by further element 406 through to 414, with further element 414 being the end and lying between further element 400 and further element 409.

A perspective view of such a device, showing the anterior edge 500 of the core 502 recessed relative to the anterior edge 504 of the overall device is shown in FIG. 14d.

The outer jacket has at least three beneficial functions. Firstly, it provides a jacket against the vertebral endplates which is separate from the inner jacket that surrounds the core. This reduces micro-motion between the core and the inner jacket, but still means that the overall level of movement is as desired for the disc replacement as a whole.

Secondly, the outer jacket serves to effectively anchor the artificial disc in place. The interdigitation of the outer jacket effectively retains the inner jacket and core within it. Furthermore, the anchoring for the whole disc achieved through the fixation of the flanges to the vertebrae with screws, bone anchors or a similar type of fixation system is strong. It may be possible, in alternative embodiments to provide a more “free floating” device with the annulus of the disc sutured closed around the device to prevent migration.

Thirdly, the material of the outer jacket can be configured to give the desired structural properties, whilst also providing a relatively open structure for the material. This assists in providing good conditions for tissue in-growth, both through the outer jacket and eventually through the inner jacket. The outer jacket can provided the desired access, but also act as a scaffold. As with the inner jacket, various combinations of bio-absorbable and non-absorbable materials can be used to assist this process.

The use of an inner jacket and outer jacket is also beneficial in that the use of multiple jackets allows the proportion of embroidery to elastomer to remain similar to that established as beneficial in the cervical disc.

In designing the artificial lumbar disc the aim has been to provide a disc having appropriate compressive stiffness. The decompression of the spinal cord through the opening of the disc space is one of the key principles in the relief of pain through disc replacement or fusion. To achieve this the artificial disc is provided with a compressive stiffness curve (force against displacement) similar or higher to the natural disc it is intended to replace. The properties of the core can be modified by doping or the like. For instance, the core may be provided with 13% barium sulphate. Alternatively (or additionally) the core may be provided with various concentrations of zinc oxide, iodine and iodine compounds, ionic contrast agents and nonionic contrast agents and the like to enhance visualization under radiograph, fluoroscopy, and magnetic resonance imaging (MRI).

Ideally, the artificial disc mimics as many of the motion stiffnesses as possible of a natural disc. Flexion/extension motions are both the most common and the largest (in terms of angle) motions that occur in the lumbar spine. This is the key stiffness which the above artificial disc seeks to match. The ability to carry shear and torsional loads on the disc itself should help protect the facet joints and is therefore also mimicked as far as possible.

One of the intentions with disc prostheses of the above mentioned type and type described in U.S. Pat. No. 6,093,205 is to encourage tissue in-growth into the disc prosthesis. The in-growth of such soft tissue into the outer jacket and/or inner jacket and/or flanges may occur. The benefit of this is that biological fixation of the prosthesis in the disc space occurs in the long term and this in turn resists undesirable migration of the prosthesis out of the correct position within the disc space. The flanges and the anchoring they provide are particularly useful in this context as they provide secure fixation of the prosthesis whilst this biological fixation develops over the first few months after implantation. The flanges may also provide a useful scaffold for the development of a biological anterior longitudinal ligament.

While the flanges need to provide a high level of fixation during the first few months after implantation, once in-growth has occurred this level of fixation is not needed. As a result, the level of tension in the flanges needed to give fixation may be undesirably high in the long term as it resists the full extension range of the spine. This is particularly a potential issue for optimum performance in the case of neck disc prostheses, where the extension range is greater.

To address this issue and provide still further improved disc prostheses, designs have been developed which reduce the tension in the flanges a few months after implantation. This may be through a reduction in the tension or its removal through the detachment of the flanges. As a result, once the biological fixation has had time to develop under preferred conditions and with mechanical restraint of the prosthesis, the prosthesis allows the full range of movement and does not compromise the spines operation long term.

A number of designs suitable for general use in the spine, including lumbar and cervical disc spaces have been developed.

Referring to FIG. 15a, an outer jacket in its flat form, before assembly to surround the core, is shown. The core would be surrounded by bottom wall 1100, by the two side walls 1104 and 1106 attached to the bottom wall 1100 and by the top wall 1102. A first pair of flanges 1108a, 1108b extend from the top wall 1102 and are joined together by a web 1110. The web 1110 and flanges 1108a, 1108b define the bounds of a hole 1112. The second pair of flanges 1114a, 1114b are attached to the bottom wall 1100 and in use are passed through the hole 1112 to provide the above mentioned interdigitation. The ends of the flanges 1108a and 1108b both have apertures 1116 which accommodate fixing screws inserted into the spine in use. The ends of the flanges 1114a, 1114b could be provided with such apertures for fixing screws, but in this case are provided with sections 1118 for receiving sutures (not shown). The operation of this feature is described in more detail below, and of course such a structure could be used in the case of both flange pairs as the fixing.

In a first design approach, the flanges are joined to the rest of the outer jacket which encloses the core by a zone of different material. This different material is made of an absorbable fiber and as a consequence, after the desired controlled period, the zone disappears and so ceases to join the flanges to the outer jacket for the core anymore. As a result, the tension in provided by the flanges is released and the full range of extension is provided. The absorption process would preferably be gradual so as to provide a phase reduction in the tension and hence phased increase in the range of movement.

In a second design approach, the flanges are formed from at least two different materials. The flanges include load bearing fibers, which are placed under and maintain the desired tension, and other fibers. The load bearing fibers are made of an absorbable fiber and as a consequence, after the desired controlled period, they are absorbed and so are no longer available to bear the load and the tension is released. The other fibers are intended to be permanent and so are then all that remains of the flanges. These other fibers may serve still to define the overall shape of the flanges, maintain the interdigitation and potentially maintain a reduced level of tension. At least a slackening of the tension results and an increased or even full range of extension is provided. The absorption process would again preferably be gradual so as to provide a phase reduction in the tension and hence phased increase in the range of movement.

In a third design, the flanges include fibers which assume a zigzag path away from the rest of the outer jacket which holds the core and towards the ends of the flanges. When implanted, the zigzag path these fibers take is maintained because these fibers are not subjected to the load applied to the flanges. Instead, that load is borne by other fibers which are attached to the outer jacket and fixation locations. These other fibers are bio-absorbable and so with time disappear. The result is that the load transfers from the other fibers to the zigzag fibers and the zigzag fibers straighten. The result is a slackening of the tension in the flanges and an increase in the range of extension possible.

In a fourth design, the zigzag fibers are again used, but this time together with a series of fibers which bridge the zigzags. The bridging fibers may be stuck to the zigzag fibers and/or wound round them and/or connected to the zigzag fibers in a fixed manner. The overall result is that these bridging fibers prevent the zigzags opening up to a linear form, at the time of implantation, and so prevent the flanges extending, when the desired tension is applied. As the bridging fibers disappear, the load transfers to the zigzag fibers, they straighten, the tension slackens and the extension range for the spine is increased.

In each of these designs, the use of sets of materials in the prostheses means that the transition is made gradual. For instance, slightly different materials, diameters, dimensions and/or densities of absorbable material can be used so as to give different periods before each of those different materials is predominantly absorbed and so ceases to bear loads. Slightly different materials could also be used to vary the extent of tissue in-growth experienced by different parts of the prosthesis, and particularly within different parts of the flanges, between zero and the maximum possible. Zero growth may be desirable where in growth is of no real benefit, for instance in locations where the release of tension would soon render it redundant. Avoiding in-growth in these areas may increase the extent of in-growth where it is beneficial. In-growth may be prevented through the use of appropriate materials to define the fixing locations, for instance. Ultra-high molecular weight polyethylene may be used as such a material.

The ends of the flanges, as mentioned briefly above, are provided with sections 1118 for receiving sutures. Such an arrangement could be provided for the ends of both pairs of flanges. These sections are formed of a reinforced parts 1120 which extend across the flanges between the load bearing fibers 1122 on one side of the flange and the load bearing fibers 1122 on the other side of the flange. A series of such reinforced parts 1120 are provided spaced along the length of the flanges. Between the reinforced parts 1120 are mesh parts 1124 forming openings which are crisscrossed by a series of fibers. These mesh parts 1124 allow the suture to be readily positioned by wrapping it around the reinforced parts 1120. By providing a series of alternating mesh parts 1124 and reinforced parts 1122 along the flanges a variety of fixing locations for use in attaching to the spine are provided.

FIG. 16 shows, left hand side, an outer jacket 1500 of one form of the present invention. The body 1502 of the outer jacket 1500 surrounds the core. The flange 1504 extending from the top surface 1506 of the body 1502 passes down through a hole 1508 in the flange 1510 extending from the bottom surface 1512 of the body 1502. The resulting interdigitation closes off the opening in the body 1502 which allows the core to be introduced. Each flange 1504, 1510 is provided with two holes 1514 which receiving fixings to attach the flanges to the spine.

In an another form, FIG. 16 right hand side, the body 1502 and lower flange 1510 extending from it are provided in the same way as the left hand side form described above. The difference lies in the configuration of the other flange 1520. Again this flange 1520 is interdigitated with the flange 1510 by being passed through a hole 1508 in the flange 1510. The flange 1520 is provided with a single hole 1514 which receives a fixing. However, the flange 1520 does not flare out to as great a width as the flange 1504 in the left hand side form. This results in a generally Y-shaped profile presented by the parts of the flanges 1510, 1520 extending beyond the location of interdigitation.

The benefits of the Y-shaped profile are explained with reference to FIG. 17 and FIG. 18. One assembled artificial disc 1600 is inserted between a first vertebra 1602 and a second vertebra 1604. The artificial disc 1600 is fixed to the first vertebra 1602 by virtue of a fixing 1606 which passes through the hole in the flange 1608. The head of the fixing 1606 is larger than the hole in the flange 1608 it passes through so giving a secure fixing to the vertebra 1602. The artificial disc 1600 is fixed to the second vertebra 1604 by virtue of two fixings 1610. Thus the stem of the Y-shaped profile is fixed to the first vertebra 1602, whilst the fork of the Y-shaped profile is fixed to the second vertebra 1604.

A second assembled artificial disc 1612 is inserted between a third vertebra 1614 and the second vertebra 1604. The second artificial disc 1612 is provided with the Y-shaped profile in the same orientation. Thus the fork of the Y-shaped profile is fixed to the third vertebra 1614, whilst the stem of the Y-shaped profile is fixed to the second vertebra 1604. This means that the second vertebra 1604 need only accommodate one fixing 1606 from the second artificial disc 1612 and two from the first artificial disc 1600, with those fixings in different positions across the face of the second vertebra 1604. This means that the fixings take up less room because of the lower number used, at even less room because of the different positions they occupy. The central fixing 1606 of the second artificial disc 1612 can be nested between the fixings 1610 of the first artificial disc 1600.

The nesting or interlocking nature of disc flanges provided in this way enable artificial discs to be provided at adjacent levels along this spine. This arrangement is particularly useful in the context of the cervical part of the spine where space is limited. As well as using a reduced number of fixings, this form of flanges also avoids overlapping of the flange from one disc replacement with the flange of another. Overlapping material is undesirable as it increases the space occupied by the replacement disc on the anterior face of the spine and renders the replacement less minimal. The flanges of the disc replacement still provided the desired anterior longitudinal ligament replacement. The fixings still provide the desired torsional stability. This type of artificial disc is still useful where only a single disc replacement is needed, however.

While the present invention has been shown and described in terms of preferred embodiments thereof, it should be understood that this invention is not limited to any particular embodiment, and that changes and modifications may be made without departing from the true spirit and scope of the invention as defined in the appended claims. By way of example only, although shown and described in the context of a lumbar disc prosthesis, the mesh prosthesis with elastomer core disclosed herein may also find use in other areas of the spine (including cervical and thoracic discs) as well as in non-spine applications, including but not limited to void-filling (for example a hernia plug as described in U.S. Provisional Patent Application 60/737,565 filed Nov. 16, 2005 and entitled “Hernia Repair Device and Related Methods”, the entire contents of which are hereby incorporated by reference), arthritis treatment, and ligament and/or joint repair. The elastomer of the present invention may be provided as a thermoplastic or a gel, including a hydrogel, and is durable, tear resistant, and biocompatible.

Additionally, it should be understood that the combination of an elastomer (such as that described herein as forming the elastomer core) with a radiopaque material in and of itself has beneficial applications throughout the body with or without the mesh outer element. The advantages include enhanced visualization under radiograph, fluoroscopy, and magnetic resonance imaging (MRI) as well as improved structural stability. Applications include filling/repairing apertures, tears, lesions, etc. in various tissue (including but not limited to muscles, organs, and/or bone), as well as repairing and/or replacing ligaments, cartilage, or joints (e.g. knee, elbow, hip, finger, etc.), delivering drugs to specific target areas (e.g. as a stent coating), and forming long-term implantable medical devices. For example, the elastomer with radiopaque material may be used in the field of cardiology, namely cardiovascular surgery, interventional cardiology, cardiological implants (e.g. heart valves and vascular grafts including artery/vessel replacement) and cardiac rhythm management. Further applications may include pacemaker and defibrillator leads, stents, indwelling catheters and other orthopedic implants. The elastomer with radiopaque material combination of the present invention may be also be used in plastic surgery, including but not limited to tissue augmentation and breast implants, where enhanced tissue screening characteristics are desirable to help discover tumors and other irregularities.

Claims

1. An intervertebral disc prosthesis, comprising: a core formed of elastomeric material and including at least one additive having radiopaque properties to enhance visibility of the implant under medical imaging; anda fabric component dimensioned to receive the core.

2. The intervertebral disc prosthesis of claim 1, wherein the fabric component comprises a first fabric component received within a second fabric component.

3. The intervertebral disc prosthesis of claim 1, wherein the elastomeric material is at least one of a thermoplastic, gel, and hydrogel.

4. The intervertebral disc prosthesis of claim 1, wherein the at least one additive having radiopaque properties includes at least one of barium sulphate, zinc oxide, iodine, iodine compounds, ionic contrast agents, and nonionic contrast agents.

5. The intervertebral disc prosthesis of claim 1, wherein the fabric component includes at least one flange extending therefrom.

6. The intervertebral disc prosthesis of claim 5, wherein the at least one flange includes an anchor location for attaching the fabric component to an adjacent vertebra.

7. The intervertebral disc prosthesis of claim 6, wherein the anchor location includes at least one aperture for receiving an anchor element.

8. The intervertebral disc prosthesis of claim 7, wherein the anchor element is at least one of a bone screw, staple, suture, and nail.

9. The intervertebral disc prosthesis of claim 1, wherein the fabric of the fabric component is formed by at least one of flat weaving, circular weaving, knitting, braiding, embroidery, and any combination of flat weaving, circular weaving, knitting, braiding, and embroidery.

10. The intervertebral disc prosthesis of claim 1, wherein the fabric component encapsulates the core.

11. The intervertebral disc prosthesis of claim 1, wherein the fabric of the fabric component is at least partially one of bio-absorbable, soluble, and degradable.

12. The intervertebral disc prosthesis of claim 1, wherein the fabric component has a smooth core-contacting surface.

13. The intervertebral disc prosthesis of claim 1, wherein medical imaging comprises at least one of radiography, fluoroscopy, and magnetic resonance imaging.

14. A method of performing spine surgery, comprising: providing a prosthetic spinal disc having core formed of elastomeric material and including at least one additive having radiopaque properties to enhance visibility of the implant under medical imaging, the core disposed within a fabric component; andimplanting the prosthetic spinal disc between a pair of adjacent vertebrae.

15. The method of claim 14, wherein the fabric component comprises a first fabric component received within a second fabric component.

16. The method of claim 14, wherein the elastomeric material is at least one of a thermoplastic, gel, and hydrogel.

17. The method of claim 14, wherein the at least one additive having radiopaque properties includes at least one of barium sulphate, zinc oxide, iodine, iodine compounds, ionic contrast agents, and nonionic contrast agents.

18. The method of claim 14, wherein the fabric component includes at least one flange extending therefrom.

19. The method of claim 18, wherein the at least one flange includes an anchor location for attaching the fabric component to an adjacent vertebra.

20. The method of claim 19, wherein the anchor location includes at least one aperture for receiving an anchor element.

21. The method of claim 20, further comprising the step of anchoring the intervertebral disc prosthesis to at least one of the pair of adjacent vertebrae by inserting the anchor element through the aperture and into the vertebral bone.

22. The method of claim 20, wherein the anchor element is at least one of a bone screw, staple, suture, and nail.

23. The method of claim 14, wherein the fabric of the fabric component is formed by at least one of flat weaving, circular weaving, knitting, braiding, embroidery, and any combination of flat weaving, circular weaving, knitting, braiding, and embroidery.

24. The method of claim 14, wherein the fabric component encapsulates the core.

25. The method of claim 14, wherein the fabric of the fabric component is at least partially one of bio-absorbable, soluble, and degradable.

26. The method of claim 14, wherein the fabric component has a smooth core-contacting surface.

27. The method of claim 14, wherein medical imaging comprises at least one of radiography, fluoroscopy, and magnetic resonance imaging.