WO2008018096A1

WO2008018096A1 - Intervertebral spacer with applicator device

Info

Publication number: WO2008018096A1
Application number: PCT/IT2006/000611
Authority: WO
Inventors: Radames Binotto
Original assignee: Radames Binotto
Priority date: 2006-08-08
Filing date: 2006-08-08
Publication date: 2008-02-14
Also published as: EP2049049A1

Abstract

A new intervertebral spacer (S) for interosseous positioning suitable for insertion between two vertebrae (V), comprising an extendible membrane (M) forming an internal space suitable for being filled wholly or partly with cementing substances, and wherein said membrane (M) can increase/reduce its extension, adapting in form and/or dimensions to the intervertebral space. The new spacer (S) comprises one or more protruding parts or teeth (D) positioned on one or both surfaces (Sv) facing said vertebrae (V).

Description

TITLE INTERVERTEBRAL SPACER WITH APPLICATOR DEVICE

DESCRIPTION

The present patent relates to the field of medical devices for spinal neurosurgery, neurotraumatology and orthopaedics, and in particular concerns a new intervertebral spacer and related applicator device. Intervertebral spacers are known for interosseus positioning, used in the treatment of vertebral pathologies, of degenerative or traumatic origin for example, and having the purpose of restoring or correcting the connection between the vertebrae of the spinal column at one or more levels, also stimulating cervical fusion.

A first problem common to the spacers currently used is due to the occlusion, by the spacer, of the haversian canals via which the bone tissue is nourished. This results in undesired high intraoperative morbidity.

Furthermore the spacers generally have low mechanical strength and are able to provide only a limited degree of intersomatic fusion. Spacers provided with holes are known, which reduce the risk of occlusion of the haversian vessels and guarantee a greater degree of fusion.

In operations for implanting one or more intervertebral spacers, the expression primary immobilisation is used, meaning the initial position at the time of the operation, and secondary immobilisation, meaning the intersomatic fusion which guarantees that the implant remains correctly positioned also in the long term.

Many of the known spacers have the drawback that they cannot be positioned in a stable manner, with the risk that the final position of the spacer is not the position desired, consequently resulting in problems for the patient.

To solve these problems, at least partially, particularly in the case of implant of intervertebral spacers at two o\ more levels, the use of plates is known connecting said spacers located in an anterior position with respect to the vertebral column and fixed to the vertebrae by means of screws.

This ensures primary and secondary immobilisation of the implant, but the operation is extremely invasive and traumatic for the patient and involves very long recovery times and the formation of calluses.

The operation for implant of the known intervertebral spacers usually entails an anterior approach, i.e. the surgical incision is made on the anterior part of the patient's body and the operation therefore also involves the internal organs, the vascular and visceral structures, with consequent serious risks for the patient.

To remedy all the above-mentioned drawbacks a new type of intervertebral spacer and related applicator device has been studied and produced.

The object of the new spacer with applicator device is to allow the surgeon to operate on the patient with a posterolateral approach, thus limiting the invasive nature of the operation and consequent risks.

A further object of the new spacer with applicator is to guide the surgeon to correct positioning and implanting in the intervertebral space(s).

A further object of the present invention is to have initially reduced dimensions with respect to the known intervertebral spacers, the spacer then being able to adapt to the intervertebral space in which it is implanted. A further object of the present invention is to permit stable initial positioning, i.e. primary immobilisation.

A further object is to permit a high degree of spinal intersomatic fusion, i.e. guarantee secondary immobilisation, not obstructing the growth of the bone trabeculae.

A further object of the present invention is not to require the use of connection plates or vertebrae fixing screws, particularly in the case of implant on two or more levels. A further object of the present invention is to limit the invasiveness of the operation.

A further object is to obtain mechanical strength comparable to that of the vertebrae.

These and other objects, direct and complementary, are achieved by the new intervertebral spacer suitable for insertion with posterolateral approach, by means of applicator device, in the anterior intervertebral space, i.e. between two vertebrae, and in which the opposite sides facing the two vertebrae comprise protrusions or teeth suitable for permitting and guaranteeing primary and secondary immobilisation of the spacer. The new spacer can vary its thickness, for example as a result of injection inside it of specific substances as described and claimed below, so as to adapt to and be constrained in a stable manner in the intervertebral space. In the preferred solution, the new spacer comprises two opposite plates, provided with said protruding parts for immobilisation, which, if not subject to any external stress, tend to position themselves on substantially parallel planes. One or more spacer elements and/or extendible shock absorber elements, i.e. able to vary their surface extension by increasing/reducing the distance between the plates, are positioned between said plates.

Said plates have a preferably bean-shaped form, i.e. a substantially curvilinear profile suitable for being inserted and positioned in the anterior intervertebral space and where said profile has at least one concave part which is positioned facing towards the spinal cord.

On one or both of said plates one or more holes are preferably obtained for the passage of cells and to permit growth of the bone trabeculae inside them, thus favouring secondary immobilisation of the spacer and fusion with the adjacent bodies. In detail, it is envisaged that between said two plates at least one membrane and/or other shock absorbing body will be positioned and constrained, having the function of spacing the two plates, countering the relative movements between the plates and delimiting an empty space between the plates, inside which cementing or similar substances can then be injected, for example substances suitable for stimulating bone re- growth, i.e. fusion, or plastic substances suitable for favouring shock absorption of the spacer.

Alternatively or in conjunction, one or more springs acting as shock absorbers and spacers can be positioned between said plates, where said springs are made of Nitinol, for example, a nickel-titanium shape memory alloy.

The new intervertebral spacer can be conveniently positioned by means of an applicator device comprising a variously shaped hollow tubular element suitable for being gripped by the surgeon during application and having, at one end, a connection element for the fitting of said spacer.

Said applicator device furthermore comprises at least one element with the function of indicating the position of the spacer. Said indicator element, integral with -said tubular element, has a preferably flat shape and lies on a plane parallel to the main plane on which said spacer lies, constrained at the end of the tubular element. The form, dimensions and actual spatial arrangement of the spacer are also illustrated on it, so that during the spacer implant operation the surgeon always knows and can therefore control the position of the spacer. Said applicator device also comprises seats, hooks or holes for the passage of at least one thread, for example a suture thread which, fixed both to the applicator device and to the spacer, ensures assembly of the applicator on the spacer during the connection operation.

Said membrane is also extendible, i.e. it permits variation of the relative distance between the two plates. For said purpose said membrane can be a balloon, for example, where the substance injected inside it causes swelling of the membrane, therefore moving the plates away from each other.

Alternatively, said membrane can be a concertina-type membrane. During the operation for implant of the spacer, the latter has for example a thickness of approximately 4-8 mm and can therefore be inserted in the intervertebral space with minimum difficulty on the part of the surgeon, who operates on the patient with posterolateral approach, also requiring smaller surgical incisions than at present.

After appropriately positioning the spacer, the surgeon inserts a needle/catheter through a duct inside said tubular element of the applicator device, bringing it out of the opposite end, i.e. where the spacer is positioned, and puncturing said membrane.

Said membrane can be provided with a valve through which said substances are injected. Via said needle, it is therefore possible to inject between said plates, i.e. in the space delimited by said membrane, the cementing and/or adhesive substance and/or the diversified stem cells or other types of material in gel or liquid form. By injecting said substance the distance between the plates is increased, i.e. the overall thickness of the spacer is increased, even up to 15 mm for example, thus adapting perfectly to the intervertebral space. The overall diameter or thickness of the spacer depends on the dimensions of said membrane used, which can be sized according to the dimensions of the intervertebral space.

Alternatively to or in conjunction with the injection of said substances, it is envisaged that one or more Nitinol springs will be positioned and retained between said plates; said springs will be initially compressed, therefore keeping the plates close to each other. The increase in temperature causes expansion of the springs, which consequently move the plates apart.

This moving apart of the plates furthermore permits quick release of the connection element of the applicator device, which is therefore disengaged from the spacer. At this point the surgeon cuts the suture thread, pulls it out and extracts the applicator, while the spacer remains anchored in the intervertebral space, in the required position.

The cementing substance also has the function of stimulating bone or cartilaginous fusion, without obstructing growth of the bone trabeculae. Said substance injected, furthermore, reaches and fills the interstices between the new spacer and the vertebrae between which the spacer is inserted, ensuring that the new spacer and the vertebrae are joined. The material used for construction of the new spacer is biocompatible, i.e. it integrates perfectly with the human tissue, and has mechanical characteristics similar to those of the adjacent vertebrae.

In particular, it is envisaged that said plates will be made preferably of plastic polymeric material, for example caprolactone or its derivatives and/or fine metal materials.

Said membrane is made for example of silicone or similar medical plastic materials, natural or synthetic polymers, also latest generation materials, with the possibility of insertion of differentiated cellular material suitable for activating bone growth and/or the growth of cartilage or other.

Other examples of materials that can be used are: hydroxylapatite mixed with plasma and gelatins of various origins and growth factors, ceramic bioglass suitable for bone fusion mixed with gelatins of various origins and growth factors, metal implantology products, elastic medical plastic silicone materials, synthetic and natural polymers, tissues, resins, polyethylene with the possibility of injection of cells suitable for colonising and transforming the supporting material.

The characteristics of the new intervertebral spacer with applicator device will be better clarified by the following description with reference to the drawings, attached as a non-limiting example.

Figure 1 shows a three-dimensional view of the spacer (S) with plates

(Pi, Ps) and concertina membrane (M).

Figure 2 shows an exploded view of the spacer e (S) and the connection end (Al) of the applicator device (A). Figure 3 shows a three-dimensional view of the applicator device (A).

Figure 4 shows schematically the position of the spacer (S) with respect to the vertebrae (V). Figure 5 shows a three-dimensional view of the spacer (S) with balloon membrane (M), while figure 6 shows aUhree-dimensional view of a further possible embodiment of the new spacer (S) with concertina membrane (M). Figures 7a₃ 7b, 7c schematise the process for implanting the new spacer

(S), initially enveloped and contained in a needle (G) for percutaneous insertion (figure 7a), extracted from the needle (G) (figure 7b) and with normal dimensions, and after the injection of substances (figure 7c). Figure 8 shows an exploded view of the spacer (S) with membrane (M) and non-compressed springs (T).

The new intervertebral spacer (S), suitable for insertion by means of applicator device (A) in the intervertebral space, comprises on the opposite sides (Sv) facing the vertebrae one or more protrusions or teeth (D) suitable for permitting and guaranteeing primary and secondary immobilisation of the spacer (S).

The new spacer (S) can vary its thickness, as a result of injection inside it of specific substances and/or due to the expansion of springs (T), made for example of Nitinol and appropriately positioned inside the spacer (S). In the solution shown in figure 1, the new spacer (S) comprises two opposite plates (Pi, Ps), bean-shaped for example, i.e. with substantially curvilinear profile with at least one concave part (Ll) which is positioned facing towards the spinal cord (L), as in figure 4.

One or more holes (B) are furthermore preferably obtained on one or both of said plates (Pi, Ps) for the passage of cells and to permit growth of the bone trabeculae inside them, thus favouring secondary immobilisation of the spacer and fusion with the adjacent bodies. It is envisaged that between said two plates (Pi, Ps) at least one membrane (M) and/or springs (T) and/or other shock absorbing body and spacer will be positioned and constrained, having the function of spacing the two plates (Pi, Ps), countering the relative movements thereof, and delimiting an empty space between the plates (Pi, Ps) inside which the cementing substances can then be injected.

In particular, said membrane (M) is extendible, i.e. it is possible to increase/reduce the height extension of its surface by increasing/reducing the distance between said plates (Pi, Ps). In the preferred solution, said membrane (M) has a concertina or balloon- shaped lateral wall (Ml).

The new intervertebral spacer (S) is positioned by means of an applicator device (A) comprising a tubular element (A2) suitable for being gripped by the surgeon during application and having, at one end, a connection element (Al) for said spacer (S). Said tubular element (A2) is preferably at least partly curvilinear to facilitate insertion and positioning of the spacer (S). Said connection element (Al) comprises for example one or more protrusions (A3) suitable for being inserted in corresponding seats (P3) obtained on one or both of said plates (Pi, Ps). Said applicator device (A) also comprises an element (N) with the function of indicating the position of the spacer (S) and where said indicator element (N) is integral with said tubular element (A2). Said indicator element (N) has a flat shape and lies on a plane parallel to the main plane on which said spacer (S) lies, fitted to the connection element (Al).

Said indicator element (N) furthermore bears, for example as a relief, engraving or drawing (R), the form, dimensions and actual spatial arrangement of the plates (Pi, Ps) of the spacer (S) fixed at the end of said tubular element (A2), so that the surgeon, during the operation for implant of the spacer (S)₅ always knows_ and can therefore control the position thereof. Said applicator device (N) and said plates (Pi, Ps) also comprise seats, hooks or holes (Gp, Fp, Ga, Fa) for the passage of at least one suture thread (F) which, fixed both to the applicator device (A) and to the spacer (S), ensures their assembly, particularly during the connection operation. In particular, as shown in figures 1 and 3, said thread (F) is kept tensioned by being retained at least at one end by means of at least one stop (Fl) inserted in a seat (Ga) obtained on said indicator element (N). The thread (F) is furthermore inserted in holes (Fa) obtained on said connection element (Al), in seats (Gp) positioned on the outer faces of said plates (Pi, Ps), in through holes (Fp) obtained on said plates (Pi, Ps) and therefore envelops and retains said plktes (Pi, Ps) on said applicator device (A) and in a suitable position.

Said thread (F) can also be partially inserted in the duct (A4) inside said tubular element (A2). As said, the extendible concertina or balloon-shaped wall (Ml) of said membrane (M) permits variation of the relative distance between the two plates (Pi, Ps).

After appropriately positioning the spacer (S), the surgeon inserts a needle or a catheter through the inner duct (A4) of said tubular element (A2) of the applicator device (A), brings it out of the opposite end, i.e. where the spacer (S) is positioned, and punctures said membrane (M).

Via said needle it is therefore possible to\inject between said plates (Pi, Ps), in the space delimited by said membrane (M), the cementing and/or adhesive substance and/or the diversified stem cells or other types of material in gel or liquid form.

By injecting said substance the distance between the plates (Pi, Ps) is increased, i.e. the overall thickness of the spacer (S) is increased, even up to 15 mm, hence it adapts perfectly to the intervertebral space.

Alternatively to or in conjunction with the injection of substances into the membrane (M), said plates (Pi, Ps) will move away from one another due to the expansion of Nitinol springs (T), positioned and retained between the plates (Pi, Ps), as shown in figure 8. Said increase in distance between the plates (Pi, Ps), furthermore, causes said protrusions (A3) of the connection element (Al) to come out of the corresponding seats (P3) on the plates (Pi, Ps), thus causing the release of said connection element (Al) from the spacer (S). The applicator device (A) can therefore be extracted, while the spacer remains anchored in a stable manner in the required position in the intervertebral space.

Said plates (Pi, Ps) comprise, on their inner face, protrusions (C) for positioning and housing said membrane (M), which fit into holes (M2) obtained in corresponding positions on said membrane (M) and where said holes (M2) also permit passage of the cementing substances and organic fluids to stimulate bone and cartilaginous fusion.

Said springs (T) can also be constrained -to said protrusions (C) of said plates (Pi, Ps) and therefore also have the function of ensuring assembly of the spacer (S), retaining said plates (Pi, Ps) and countering the relative movements thereof. Alternatively, said membrane (M) can be constrained to one or both of said plates (Pi, Ps) in another way, for example by gluing or by slotting in. Alternatively, said teeth (D) can be positioned directly on said membrane

(M), as shown in figures 5 and 6, and in particular on its contact surface

(Sv) with said vertebrae.

Said membrane (M) is preferably made of elastic material, for example silicone, nylon or derivatives, polyethylene or derivatives, etc., while said teeth (D) are made of rigid material, such as plastic polymeric material, for example caprolactone or its derivatives and/or metallic materials such as titanium, medical steel, etc.

In said case, said applicator (A) is a needle or thread guide or cannula needle, i.e. comprising an internal duct for the injection of substances.

It is envisaged that said applicator (A) will comprise a connection element (Al) for connection to said spacer (S), suitable for permitting release of the spacer (S) once it has been appropriately positioned in the intervertebral space. In said regard, it is envisaged that said applicator (A) will comprise a connection element (Al) with slot or thread coupling or other release devices.

The spacer (S) produced as above can have extremely compact dimensions and can therefore be inserted in the intervertebral space also percutaneously as well as surgically.

The spacer (S), adequately closed as in figure 7a, can be inserted in the intervertebral space by means of a needle (G) which is removed after positioning of the spacer (S) (figure 7b).

Via the inner duct of said applicator (A) substances are then injected suitable for extending and expanding the membrane (M) of the spacer

(S), which adapts to the intervertebral space (figure 7c).

The teeth (D) positioned on said membrane (M) block the spacer (S) between the vertebrae and the applicator (A) can be removed.

The new interosseous spacer (S) can also be wholly or partly coated in carbon or pyrolytic carbon.

Therefore with reference to the preceding description and the accompanying drawings the following claims are made.

Claims

1. Intervertebral spacer (S) for interosseous positioning suitable for insertion between two vertebrae (V), characterised in that it comprises at least one extendible membrane (M) forming an internal space suitable for being filled wholly or partly with cementing substances, and wherein said membrane (M) can increase/reduce its extension, adapting in form and/or dimensions to the intervertebral space.

2. Intervertebral spacer (S) for interosseous positioning, according to claim 1, characterised in that it comprises one or more protruding parts or teeth (D) positioned on one or both surfaces (Sv) facing said vertebrae

(V).

3. Intervertebral spacer (S), according to claims 1, 2, characterised in that it comprises parts suitable for being constrained in a removable manner to at least one applicator device (A) for insertion of said spacer (S) in the anterior intervertebral space, and wherein said applicator (A) comprises at least one duct for the injection, into said membrane (M), of cementing and/or adhesive substances and/or diversified stem cells and/or other types of material in gel or liquid form.

4. Intervertebral spacer (S) for interosseous positioning, according to claims 1, 2, 3, characterised in that it comprises at least two opposite plates (Pi, Ps) with holes (B) for the passage of cells and to permit the growth of bone trabeculae; said extendible membrane (M) and/or one or more springs (T) and/or other shock absorbing element and/or spacer suitable for permitting variation of the relative distance between said plates (Pi, Ps) are positioned between said plates (Pi, Ps).

5. Intervertebral spacer (S) according to claim 4, characterised in that said membrane (M) has an extendible lateral connection wall (Ml) between said plates (Pi, Ps) in thejform of a concertina or balloon.

6. Intervertebral spacer (S) according to claim 4, characterised in that said plates (Pi, Ps) have a flat bean-shaped form with generically curvilinear profile suitable for insertion in the anterior intervertebral space.

7. Intervertebral spacer (S) according to claims 4, 5, 6, characterised in that said springs (T), positioned and fixed between said plates (Pi, Ps) and suitable for countering the relative movements thereof, are made of Nitinol, and wherein the expansion of said springs (T) causes an increase in distance between said plates (Pi, Ps).

8. Intervertebral spacer (S), according to claims 3, 4, 5, 6, 7, characterised in that one or both of said plates (Pi, Ps) are suitable for being constrained to said applicator device (A) for the insertion of said spacer (S) in the anterior intervertebral space, in turn comprising: - at least one tubular element (A2) suitable for being gripped by the surgeon; at least one connection element (Al) comprising one or more protrusions (A3) suitable for being inserted in corresponding seats (P3) on one or both of said plates (Pi, Ps), to constrain said spacer (S) to ^said applicator device (A), and wherein said connection element (Al) is positioned at one end of said tubular element (A2); at least one element (N) indicating the position of said spacer element (S) constrained to it.

9. Intervertebral spacer (S), according to the preceding claim, characterised in that said tubular element (A2) is at least partly curvilinear for the insertion of said spacer (S) from the posterolateral part of the patient's body with respect to the vertebral column.

10. Intervertebral spacer (S), according to claim 8, characterised in that said applicator device (A) comprises at least one thread (F) suitable for retaining said plates (Pi, Ps), constraining them to said applicator device (A) in the correct position during insertion of the spacer (S).

11. Intervertebral spacer (S), according to the preceding claim, characterised in that said thread (F) is kept tensioned by being constrained at at least one end to said applicator device (A) and passing through seats (Ga, Gp) and/or hooks and/or holes (Fa, Fp) and/or ducts (A4) obtained on said applicator device (A) and on said plates (Pi, Ps) and wherein the removal of said thread (F) releases said spacer (S) from said applicator device (A).

12. Intervertebral spacer (S), according to claim 8, characterised in that the increase in distance between said plates (Pi, Ps) causes said protrusions (A3) of the connection element (Al) to come out of the corresponding seats (P3) on the plates (Pi, Ps), therefore causing the release of said connection element (Al) from the spacer (S).

13. Intervertebral spacer (S), according to claim 8, characterised in that said indicator element (N) comprises at least one substantially flat part lying on the same plane as the main plane on which said spacer (S), constrained to said applicator device (A), lies, and wherein said flat part bears the outline (R) of the plates (Pi, Ps) of said spacer (S) in its form, spatial position and real dimensions.

14. Intervertebral spacer (S), according |o claim 8, characterised in that said tubular element (A2) comprises internally at least one duct (A4) for access, via said tubular element (A2) and said connection element (Al), to the space between said plates (Pi, Ps), in the vicinity of the wall (Ml) of said membrane (M).

15. Intervertebral spacer (S), according to the preceding claim, characterised in that said membrane (M) is suitable for being perforated with a needle and/or catheter or other instrument for the injection of cementing and/or adhesive substances and/or diversified stem cells and/or other types of material in gel or liquid form, introduced via said duct (A4).

16. Intervertebral spacer (S), according to the preceding claims, characterised in that one or both of said plates (Pi, Ps) comprise one or more of said protruding parts or teeth (D), positioned on their outer contact surfaces (Sv) with said vertebrae (V).

17. Intervertebral spacer (S), according to claims 1, 2, characterised in that said membrane (M) comprises one or more of said protruding parts or teeth (D), positioned on its contact surface (Sv) with said vertebrae (V).

18. Spacer (S) for interosseous positioning according to the preceding claims, characterised in that it is made of one of the following materials, or in a combination thereof: hydroxylapatite mixed with plasma, ceramic bioglass suitable for bone fusion, metal implantology products, elastic medical plastic silicone materials, synthetic and natural polymers, tissues, resins, polyethylene with the possibility of injection of cells suitable for colonising and transforming the supporting material.

19. Spacer (S) for interosseous positioning according to the preceding claims, characterised in that said plates (Pi, Ps) are made of one of the following materials, or in a combination thereof: plastic polymeric materials, such as caprolactone or its derivatives, titanium, steel, ceramic or other materials suitable for facilitating and stimulating bone or cartilage fusion.

20. Spacer (S) for interossetissuesous positioning according to the preceding claims, characterised in that it is wholly or partly covered in carbon and/or pyrolytic carbon.