INTERVERTEBRAL FUSION DEVICE COMPRISING AN INTERVERTEBRAL STABILISING SCREW AND A COMPOSITION FOR BONE REMODELLING

Abstract

The invention relates to an intervertebral fusion device comprising an intervertebral stabilizing screw and a composition for bone remodeling. The intervertebral stabilizing screw comprises: a main body with an axial through-hole and a distal thread that is secured to the bone, located at a distal end of the main body; a hollow proximal secondary body that can slide along the length of the main body; and a travel stop for the proximal secondary body, located on an outer surface of the main body. According to the invention, the proximal secondary body also includes an external thread for securing to the bone, and the main body comprises at least one fill hole, located between the distal thread and the travel stop, for connecting an intervertebral space to the aforementioned axial hole.

Claims

1. An intervertebral stabilizing screw comprising a main body with an axial through hole and a distal thread for securing to the bone, located at a distal end of the main body, a hollow proximal secondary body that can slide along the length of the main body and a travel stop for the proximal secondary body, located on an outer surface of the main body, wherein the proximal secondary body also includes an external thread for securing to the bone, and said main body comprises at least one fill hole, located between the distal thread and said stop, for connecting an intervertebral space to said axial hole.

2. The screw, according to claim 1, wherein the external diameter of the thread of the proximal secondary body is greater than the diameter of the distal thread.

3. The screw, according to claim 1, wherein said stop consists of a step which impedes the travel of the proximal secondary body up to said fill.

4. The screw, according to claim 3, wherein the step is formed by a variation in the external diameter of the main body.

5. The screw, according to claim 1, wherein said screw comprises at least two fill holes.

6. The screw, according to claim 1, wherein said fill hole or holes has or have a radial course.

7. The screw, according to claim 6, wherein said fill hole or holes has or have a diametric course, with two outlets that connect opposite points of the wall of the main body.

8. The screw, according to claim 1, wherein both the main body and the proximal secondary body have at the proximal end thereof devices for receiving a percutaneous tool.

9. The screw, according to claim 1, further comprising a proximal cover to close off access to the axial hole once the screw is installed.

10. The screw, according to claim 1, wherein the main body and the proximal secondary body are threaded together, in such a way that said sliding along the length of the main body comprises a relative rotation therebetween.

11. A composition for bone remodelling comprising: polymerizable bone cement, a calcium phosphate provider, and an oxygen providing compound.

12. The composition, according to claim 1 further comprising an osteogenic factor.

13. The composition, according to claim 11 further comprising a contrast agent.

14. The composition, according to claim 11, wherein the oxygen providing compound is selected from the group consisting of oxygenated water, ozone and an oxygen solution.

15. The composition, according to claim 14, wherein the oxygen provider is oxygenated water.

16. The composition, according to claim 11, wherein the polymerizable e bone cement comprises a polymer selected from the group made up of poly(methyl methacrylate) (PMMA), bisphenol A glycidyl methacrylate (bis GMA) and poly(lactic co glycolic acid) (PLGA).

17. The composition, according to claim 16, wherein the polymerizable e bone cement comprises PMMA.

18. The composition, according to claim 11, wherein the calcium phosphate provider is hydroxyapatite, brushite or tricalcium phosphate.

19. The composition, according to claim 18, wherein the calcium phosphate provider is hydroxyapatite.

20. The composition, according to claim 11, wherein the osteogenic factor is selected from blood derived growth factors, whole blood or osteogenic stem cells.

21. The composition, according to claim 20, wherein the osteogenic factor is a blood derived growth factor.

22. The composition, according to claim 11, wherein the contrast factor is a non ionic contrast factor.

23. The composition, according claim 11, wherein the polymerizable bone cement is present in a quantity of between 55% and 80% by weight of the composition.

24. The composition, according to claim 11, wherein the calcium phosphate provider is present at between 15% and 30% by weight of the composition.

25. The composition, according to claim 11, wherein the oxygen providing compound is present in a quantity equal to or less than 5% by weight.

26. The composition, according to claim 12, wherein the osteogenic factor is present in a quantity of less than 5% by weight.

27. The composition, according to claim 13, wherein the contrast agent is present in a quantity of less than 1% by weight.

28. An intervertebral fusion device comprising: at least one vertebral stabilizing screw according to claim 1 and a composition for bone remodeling, which comprises: polymerizable bone cement, a calcium phosphate provider, and an oxygen providing compound.

29. The device, according to claim 28, comprising at least two of said vertebral stabilizing screws.

Description

[0038] FIG. 1 is a side view of an embodiment of a screw according to the present invention.

[0039] FIG. 2 is a view in cross section through the lateral mid-plane of the screw of FIG. 1.

[0040] FIG. 3 is a view in cross section through a mid-plane perpendicular to the cutting plane of FIG. 2.

[0041] FIG. 4 is a view from a sagittal plane of the vertebral level that will be fused. The figure shows the lower vertebra and the disk space, the upper vertebra having been omitted. The trajectory of introduction of the screw according to the present invention has also been shown.

[0042] FIG. 5 is a view from an axial plane of the level to be fused of the previous figure, in which the placement trajectory of the screw has also been marked.

[0043] FIG. 6 is a view from a coronal plane of the spine shown in the previous figures, with the placement trajectory of two screws according to the present invention also marked.

[0044] FIG. 7 shows a first phase of an example of the process of putting in place the device according to the present invention, in which the disk content (nucleus) has been omitted.

[0045] FIG. 8 shows diagrammatically a second phase of the device placement process.

[0046] FIG. 9 shows diagrammatically a third phase of the device placement process.

[0047] FIG. 10 shows diagrammatically a fourth phase of the device placement process.

[0048] FIG. 11 shows diagrammatically a fifth phase of the device placement process.

[0049] FIG. 12 shows diagrammatically a sixth phase of the device placement process.

[0050] FIG. 13 shows diagrammatically a seventh phase of the device placement process.

[0051] FIG. 14 shows diagrammatically an eighth phase of the device placement process.

[0052] FIG. 15 shows from a lateral viewpoint a device according to the present invention already in place and prepared for the fusion of a vertebral level.

[0053] FIG. 16 is a perspective view of a second embodiment of a screw according to the present invention.

[0054] FIG. 17 is an exploded perspective view of the second embodiment.

[0055] FIG. 18 is a view in cross section through the lateral mid-plane of the screw of the second embodiment.

[0056] FIG. 19 is a perspective view of three auxiliary tools for actuating the screw of the second embodiment.

[0057] FIGS. 20 and 21 are diagrammatic views of a first method of actuating the screw of the second embodiment.

[0058] FIGS. 22 and 23 are diagrammatic views of a second method of actuating the screw of the second embodiment.

[0059] FIG. 24 shows a third embodiment of a screw according to the present invention.

[0060] FIGS. 25 to 27 show diagrammatically a process of putting in place the third embodiment, using two concentric sleeves.

[0061] FIGS. 1 to 3 show an embodiment of a screw according to the present invention.

[0062] The example of a screw shown in the figures comprises two parts that can move relative to one another:

[0063] a main body -1- and a proximal secondary body, hereinbelow, a proximal body -2-. The proximal body -2- slides along the length of the main body, in an axial direction. The references to distal and proximal take as their reference the transcutaneous process of placing a screw in a patient.

[0064] The main body -1- has at its distal end a distal thread -11- for securing to bone. The rest of the main body is separated into two areas -12-, -13- separated by a limit stop -123- formed by a step produced by a sudden change in the external diameter thereof. A proximal body -2-, which also has a proximal thread -21- for securing to bone, is able to travel over the outside of the most proximal area -13-. Since the proximal thread -21 must be secured to bone in an area through which the distal thread -11- has already passed, it may be advantageous for the external diameter of the proximal thread -21- to be greater than that of the distal thread -11-, in order to improve securing. The limit of travel of the proximal portion -2- is defined by the interference of the most distal face -213- thereof with the limit stop -123-.

[0065] Both the main body -1- and the proximal body -2- have at their proximal ends areas or devices -19-, -29- which allow said bodies to be suitably operated using percutaneous devices. It will be appreciated that said areas may be different from those shown.

[0066] Both the main body -1- and the proximal body -2- are hollow, and have an axial hole. In the case of the proximal body, this allows said body to slide along the length of the main body -1-, but it would also be possible, alternatively, for both bodies to be threaded together.

[0067] The axial hole of the main body terminates in a distal hole -14-. This allows the main body to be guided in its travel. In addition, the example has fill holes arranged diametrically with opposite outlets -17-, 17-, -18-, -18- in the area -12- between the limit stop -123- and the distal thread -11-. Said holes will allow the intervertebral space (inside the vertebral disk) to be filled with a bone remodelling composition through the axial hole and the fill holes.

[0068] The fill holes preferably have two or more cores and the arrangement thereof may be symmetrical. The ideal fill hole core and the composition thereof depend on the anatomy and vertebral condition of the patient.

[0069] FIGS. 4 to 6 show the preferred placement trajectory of two screws according to the present invention for fusing a vertebral level. Two screws are sufficient. The introduction thereof is transpedicular, passing through the disk space in such a way that the distal thread will be threaded in the upper vertebra and the proximal thread in the lower vertebra.

[0070] The preferred access point for percutaneous placement is situated in the pedicle, in the centre of the upper articular process and approximately 1 mm below the lower edge of the transverse process of the vertebra, varying according to the specific anatomy and other factors.

[0071] The angle of introduction (defined by the value of the angles -A-, -B-, -C-) also varies depending on the specific anatomy of the vertebra. An optimal value for an L4-L5 fusion would be 355 for each of the three values (-A-, -B-, -C-), more preferably 35.

[0072] FIGS. 7 to 14 show an example of an installation process of an embodiment of an intervertebral fusion device according to the present invention.

[0073] In said figures, elements that are the same or equivalent to those shown in the previous figures have been identified with identical numerals and will therefore not be explained in detail.

[0074] Initially, the guides may be installed following the direction shown in FIGS. 4 to 6. For reasons of clarity, the guides have not been shown in any of the figures. For the application shown, an 11G Jamshidi-type trocar may be used for example for accessing and penetrating the pedicle and a Kissner needle as a guide for the placement of the screw. Placement is transcutaneous, bilateral and pedicular. Using fluoroscopic techniques, its passage through the disk space and penetration 5-10 mm into the body of the upper vertebra and through the lower platform of the upper vertebra can be controlled.

[0075] At any time in the process (not shown in the figures) it may be useful to check the state of the seal of the ring using radiological discography, in order to verify that the technique is viable and/or to adjust the viscosity of the bone cement.

[0076] The process begins with ablation or nucleolisis, for example by radiofrequency, of the material inside the disk -1000-. This can be carried out with a Jamshidi-type cannula, as shown in FIG. 7. This technique appears viable, as it has already been applied to the ablation of metastatic posterior vertebral body osseous tumours using a bipolar device for ablation by radiofrequency. Alternatively, the material may also be removed mechanically. The cannula -901- may have been inserted by guiding, using sufficiently known percutaneous techniques. In the figure, a single cannula has been shown, but two may be inserted, one on either side. This technique has the advantage of making possible the preservation of the disk ring.

[0077] Next the waste disk material produced by the nucleolisis is drawn off. To do this, a cleaning fluid is introduced at one side and removed at the other side, which draws out the waste material. To do this, two transpedicular cannulas may be used such as the cannula -901- shown in FIG. 7, one on either side. In FIGS. 8 and 9 an alternative technique has been shown in which two screws are introduced, said screws being threaded using the appropriate tool -900-, until the distal hole -14- of both screws is situated in the distal space and the cleaning fluid is then circulated through the two axial holes of both screws.

[0078] Once the disk space has been cleaned, the vertebral platforms of the adjacent vertebrae -1001-, -1002- are scraped (or stippled) (see FIG. 10). This can be done in various ways and with different tools. For example, as an alternative to the tool shown in FIG. 10, an osteotome may be used, for example the osteotome marketed under the name DFINE Midline, or the like, to make multiple perforations in the platforms. Using this technique, new bone will grow from the platforms and will remain connected thereto.

[0079] Once the nucleus of the ring has been cleaned and the vertebral platforms have been scratched, the screw according to the present invention can be introduced up to the end of its travel (see FIGS. 11 to 13).

[0080] Initially, the main body -1- enters until the distal thread -11- is threaded into the upper vertebra -1001- and the holes -17-, -18- are in the interior disk space -1000-. The bilateral placement process, with two screws, allows some correction of any vertebral deviations.

[0081] Next, the proximal body -2- is threaded inside the pedicle and the body of the lower vertebra -1002- until reaching the limit stop. Once the limit stop has been reached, it is possible to continue threading the proximal thread -21- against the limit stop. This creates a distraction which produces slight intervertebral lordosis. This effect is recommended, as most patients who require fusion have lost lordosis. The use of this over-threading also allows vertebral distractions to be corrected.

[0082] Once the screws have been put in place, the Kissner-type guide needle (not shown in the figures) can be removed and the void created in the disk space can be filled with a bone remodelling composition.

[0083] To produce the bone regeneration composition according to the present invention any type of polymerisable bone cement can be used. Polymerisation allows the cured bone cement to be introduced in a liquid or semi-liquid state with immediate hardening of the bone cement inside the intervertebral disk.

[0084] There are different grades of commercial polymers which are biocompatible and which, owing to the selection of components and/or additives, have polymerisation temperatures that are close to body temperature. Said polymers are generally commercialised in the form of a powder which must be mixed with a liquid polymerisation activator. Once the activator and powder have been mixed, with some commercial bone cements, the viscosity can be modified, for example by heating. An example of such a bone cement is that named StabiliT, the main component of which is PMMA. The hardening time is under 30 minutes, which allows the relative position of the vertebrae to have consolidated by the end of the operation, which makes it possible to dispense with splints and exoskeletons during the bone formation period.

[0085] Control of viscosity may allow a bone-growth-promoting bed to be produced inside the disk which serves as a support including in cases where the ring is damaged. In particular, greater viscosity allows for controlled delivery and solidification before the composition leaves the disk space.

[0086] The process of producing the composition according to the present invention comprises the addition of a calcium phosphate provider, an oxygen provider and, optionally, an osteogenic factor and a contrast agent, more preferably, a non-ionic contrast agent.

[0087] For example, to produce a composition according to the present invention, StabiliT bone cement (PMMA) is used, using a mixture of commercial activator with 5% by weight of oxygenated water as an activator, which is mixed with a mixture of StabiliT and hydroxyapatite powders at 20% by weight. It was observed that polymerisation was not stopped by the presence of oxygenated water. Once hardened, it was observed that greater porosity of the hardened bone cement was visible with the naked eye.

[0088] The same test was carried out by also adding blood-derived bone growth factors and a contrast agent (Lopamir or similar) to the activator liquid in quantities of less than 5%. Polymerisation was also successful.

[0089] Before the end of polymerisation the composition is introduced into the disk void that has been produced (see FIG. 4) while checking that said composition does not come out of the disk space limited and contained by the disk ring and waiting for a few minutes until polymerisation is complete. The composition comes out through the outlet fill holes -17-, -18-, -17-, -18-.

[0090] In addition, a cover -920- should be put in place which closes off access to the disk space by extraneous items.

[0091] Once hardened, the composition introduced inside the disk -1000- produces a bed -30- with numerous pores -31- in which bone will grow from the damaged areas of the platforms of the upper -1001- and lower -1002- vertebrae. Growth is maximised by the presence of oxygen and osteogenic growth factors inside the disk space and enhanced by the availability of calcium phosphate, preferably hydroxyapatite.

[0092] FIGS. 16 to 23 show a second embodiment of the screw according to the present invention. Elements that are identical or similar and/or equivalent to those explained earlier have been identified with identical numerals and will not be explained in greater detail.

[0093] In the second embodiment, the proximal ends -19-, -29- of the main body -1- and of the proximal body respectively have been modified. In particular, the proximal end -19- of the main body -1- does not project from/beyond the proximal body -2- and consists of an indented area. Furthermore, the proximal end -29- of the proximal body -2- comprises a hexahedron-shaped outer portion for receiving an actuation tool and an inner thread -31- for receiving, for example, a cover -3- (or other actuation tool).

[0094] The cover -3- has a thread -31- that fits with the inner thread -31- of the proximal body and a hexahedral recess -39- for receiving an actuation tool.

[0095] Compared with the first embodiment shown in FIGS. 1 to 15, an extra pair of holes -16- has been arranged positioned at 90o relative to the rest of the fill holes -17-, -18-.

[0096] FIG. 19 shows three auxiliary tools, in particular, an adaptor head -903- and two actuation tools -901-, -902-, which can be used alternately. Either of the two actuation tools produces a relative movement between the main body -1- and the proximal body -2- of the screw, which also produces a relative rotation between the main body -11- and the proximal body -2- (using the auxiliary tool -901-) or not (using the auxiliary tool -902-).

[0097] More specifically, the adaptor head -903- comprises an outer surface which is adapted to a tool -913- (which has a hexagonal surface) and a thread -933- that fits with the inner thread -31- of the proximal end -29- of the proximal body -2-. The body of the adaptor head is hollow, and has a through-hole with a section of internal thread (not visible in FIG. 19).

[0098] Both auxiliary tools -901-, -902- have tool adaptor heads -911-, -912- and threaded rods -921-, -922-, the thread of which fits with the thread of the through-hole of the adaptor head -903-. The distal ends -931-, -932- of both tools vary. In one case (-901-), the distal end -931- is indented and fits with the proximal end -19- of the main body. In the other case (-902-), the distal end -932- is planar. As a result, both tools actuate the main body -1- differently.

[0099] FIGS. 20 and 21 show the actuation produced by the first auxiliary tool -901-. The adaptor head -903- is threaded into the proximal head -29- of the proximal body -2- and the threaded rod of the first auxiliary tool -901- is inserted in the through-hole of the adaptor head -903- until said rod reaches the internal threaded section, so that subsequent advances of the auxiliary tool -901- must be made by rotation. When the distal end -931- of the first auxiliary tool -901- touches the proximal end -19- of the main body, the indented elements fit together, which means that the main body -1- as well as moving relative to the proximal body -2- (increasing the distance -A-) rotates drawn by the first auxiliary tool -901-, as can be seen by comparing FIGS. 20 and 21, in which the angular position of the fill holes -16-, -17-, -18, changes.

[0100] FIGS. 22 and 23 show the equivalent process with the second auxiliary tool -902-, the distal end -932- of which is planar and not hollowed out. In this case, the second auxiliary tool pushes the main body -9-, but without transmitting any rotation thereto. Using the first auxiliary tool -901- it is possible to go deeper into the thread of the main body into the corresponding vertebra, whereas with the second auxiliary tool -902- the distance between vertebrae can be increased.

[0101] FIG. 24 shows a third embodiment of a screw according to the present invention. Elements that are the same or equivalent to those shown in previous figures will be identified with identical numerals and will therefore not be described in detail.

[0102] In this embodiment auxiliary fill holes -99- have been arranged in the thread area -11- of the main body -1-. Said holes are useful in cases of osteoporosis which require distal cementing of the vertebral body. Said holes -19- may, of course, be implemented in other embodiments, for example, in those shown above.

[0103] Another modification compared with the previous embodiments is to add various threads -98-, -97- that fit together between the proximal body -2- and the main body -1-. This causes movement between both bodies to also be associated with a rotation between both portions. In addition, the proximal end -29- of the main body has an internal surface for receiving an actuation tool, for example a standard tool.

[0104] The use of two concentric external sleeves -1001-, -1002-, one inside the other (not shown in the figure) is therefore possible in order to advance both portions of the screw simultaneously while, nevertheless, being able to screw the main body -1-, the proximal body -2- independently to the bone, or both bodies at the same time.

[0105] FIGS. 25 to 27 show diagrammatically a process for the placement of a screw according to the present invention using two concentric sleeves -1001-, -1002-. The sleeves have been shown diagrammatically and without detail. It will be understood that the distal ends thereof are of a suitable shape to actuate the different bodies of the screw -1-, -2-.

[0106] With reference to FIG. 25, the screw is put in place with the aid of the internal sleeve -1001- (or alternatively the screw is put in place by other means after the internal sleeve -1001- has been put in place). The internal sleeve has a central through-hole -1011- in which the bolt that was inserted initially is housed and is used for testing the screw and internal sleeve -1001-. The internal sleeve -1001- has a pointed or conical distal end -1021- to prevent the through-hole of the screw from being blocked by unwanted particles from the patient's body. The screw may also have a conical distal point. Next (see FIG. 26), the outer sleeve -1002-, which has a through-hole -1012- in which the inner sleeve -1001- is housed, is put in place.

[0107] With the two sleeves in position, the main body of the screw can be threaded and/or moved forward (by means of the inner sleeve) or the proximal body (by means of the outer sleeve) or both at the same time (with both sleeves being actuated simultaneously). This can be achieved using tools at the proximal end that are known in the field of non-invasive surgery.

[0108] Once the screw is in place, the inner sleeve -1001- and the bolt (not shown in FIGS. 25 to 27) are withdrawn, leaving the outer sleeve -1002- in place, and the through-hole thereof -1012- is used as a guide for the bone filler or tool for injecting the bone cement or substance for treating the interdiskal space and/or vertebra. Next, the outer sleeve is withdrawn.

[0109] The divergent characteristics of the embodiments shown are applicable to other embodiments shown, either grouped together or individually.

[0110] The installation process may be different from that shown, and different percutaneous techniques or even non-percutaneous techniques may also be used. The order of the operations is also subject to change.

[0111] Although the invention has been described with respect to preferred embodiments, said embodiments should not be considered as limiting the invention, which will be defined by the widest interpretation of the following claims.