Biocompatible material in granules made of metal material or metal alloys and use of said granules for vertebroplasty

Abstract

More specifically, granules made of biocompatible metal material, preferably osteoinductive metal, for use in vertebroplasty surgery, as well as the use of these granules for this purpose, are the object of the present invention.

Claims

1. A granule made of biocompatible metal material or alloys of said metal material, wherein said granule comprises a solid spherical structure with an outer diameter of between 3 and 4 millimeters, and an outer surface having a trabeculated porous structure, wherein the trabeculated pores of the outer surface have a diameter of between 400 and 800 microns.

2. The granule according to claim 1, wherein the pore diameter is about 600 microns.

3. The granule according to claim 1, wherein said granule is made of titanium or titanium alloys.

4. The granule according to claim 1, wherein said granule is made by means of production techniques that provide for at least one step of localized micro-fusion of powders through high energy electron beams (EBM) or laser.

5. The granule according to claim 1, wherein said granule has an average size of smaller than 7 mm.

6. The granule according to claim 1, wherein said granule comprises a connecting means for connecting said granule to at least another granule.

7. Two or more granules of claim 6 connected together to form a chain of granules.

8. The granule according to claim 1, wherein the pore diameter is 640 microns.

9. The granule according to claim 1, wherein said granule is between 1 and 6 mm in size.

10. The granule according to claim 1, wherein said granule is between 4 and 6 mm in size.

11. The granule according to claim 1, wherein said granule has an outer diameter of about 3 millimeters.

12. The granule according to claim 1, wherein said granule has an outer diameter of 3.3 millimeters.

13. A method of performing a vertebroplasty surgery, said method comprising: selecting a subject in need of vertebroplasty surgery; providing a composition comprising a plurality of the granules of claim 1; and depositing said composition into an internal cavity of one or more vertebra of the selected subject.

Description

LIST OF DRAWINGS

(1) Further characteristics and advantages of the present invention shall become clearer from the following detailed description, provided by way of a non-limiting example and illustrated in the accompanying drawings, wherein:

(2) FIG. 1 shows a drawing representing a side view of a portion of vertebral column;

(3) FIG. 2 shows a section of biconcave collapsed vertebra wherein the main body, the cancellous bone, and a cannula inserted into said main body with pedicular access are visible;

(4) FIG. 3 shows a section of the collapsed vertebra with wedge-shape and with cannula inserted into the main body;

(5) FIG. 4 shows the insertion of a known balloon into the main body of the vertebra;

(6) FIG. 5 shows a porous trabecular surface made of titanium or titanium alloy;

(7) FIG. 6 shows an electron microscopic view of the structure of the trabecular bone.

DETAILED DESCRIPTION

(8) According to the present invention, granules made of biocompatible metal material, more particularly based on titanium and/or its alloys, are produced with characteristics such as to make the insertion of granules and osseointegration, once in place, simultaneously possible during the surgical phase.

(9) The term granules is used in the present description to indicate solid particles having any geometry whatsoever, preferably, but not exclusively an approximately spherical geometry, and having average size of the order of a few millimeters, preferably less than 7 mm, even more preferably but not necessarily between 4 and 6 mm.

(10) In the case in which these granules have a spherical geometry, they will be characterized by an outer diameter of a few millimeters, preferably less than 7 mm, more preferably but not necessarily between 4 and 6 mm.

(11) According to a preferred embodiment of the present invention, said granules will have spherical shape, in particular they will have a solid spherical structure. According to a less preferred variant, said granules could have a hollow spherical shape.

(12) Preferably, said spheres will have a porous outer surface.

(13) Even more preferably, the surface of said spheres will have a trabeculated and perforated structure, so as to promote osseointegration.

(14) Granules or spherical particles with solid or hollow and outer surface having a trabeculated structure according to the present invention were obtained by the applicant by means of production techniques that envisage the localised precision casting of powders (metal or polymeric) by means of high-energy electron beams. Nowadays, these techniques, known as EBM, acronym of the English expression Electron Beam Melting, are extremely avant-garde manufacturing technologies that allow objects having even very complex geometry and with different surface roughness to be produced starting from a computer drawing of the finished product, which is processed by computerised machines that guide the electron beam in its action.

(15) Electron beam melting is a relatively new rapid prototyping technique for producing structures for implants, and allows complex three-dimensional geometries to be produced.

(16) Using this technique, many surface characteristics can be designed so as to develop the superficially optimal structure for osseointegration, proliferation, and differentiation for non-cemented prostheses.

(17) According to the present invention, this technology can be used to produce granules made of metal material or metal alloys, having a solid or hollow spherical structure, with trabeculated surface and surface roughness that allows and indeed promotes osseointegration and bone regeneration.

(18) Preferably, the granules according to the present invention will have a surface having a regular trabecular structure, with pore size between one trabecula and the next of the order of a hundred or so microns.

(19) One example of titanium surface having a trabecular structure is shown in FIG. 5.

(20) FIG. 6 shows an electron microscopic view of the structure of the trabecular bone.

(21) More specifically, the regular trabeculated structure will have pore diameter ranging between 300 and 1000 microns, more preferably between 400 and 800 microns, even more preferably the pore diameter will be of about 600 microns, preferably of 640 microns.

(22) In particular, thanks to an elastic module very similar to that of the natural trabecular bone, the trabecular structure made of titanium or titanium alloys restores the physiological transfer of the loads, preventing damage to the bone and, indeed, promoting the regeneration thereof.

(23) The trabecular titanium is able to stimulate osseointegration: in vitro studies demonstrate that within three weeks of implant there is already full colonisation of the trabecular structure on the part of the osteoblasts, while in vivo studies already show an excellent osseointegration at 26 weeks with new lamellar bone formations.

(24) According to a preferred embodiment of the present invention, the granules of biocompatible material are made of a metal material, preferably titanium or its alloys, such as for example the titanium-aluminium-vanadium TiAl4V alloy, or pure grade 2 titanium or chrome-cobalt alloys or other materials having analogous characteristics in terms of biocompatibility and able to promote bone regeneration. As mentioned, kyphoplasty or vertebroplasty surgery provides for the use of a balloon or analogous system that allows the now compromised cancellous bone to be compacted and the internal cavity of the body of a vertebra to be expanded.

(25) Even in the case of the use of granules according to the present invention instead of the cement in use in the state of the art, the surgical technique remains entirely unchanged.

(26) Once the balloon, or other analogous device, has been retracted and the cavity of the vertebrae prepared, the surgeon will proceed with the insertion of the granules according to the present invention instead of the PMMA.

(27) Inclusion of the granules according to the present invention can preferably take place via a cannula that is identical or altogether analogous to the one currently used in kyphoplasty surgeries with balloon and insertion of PMMA.

(28) The granules of the present invention can therefore be deposited within the cavity of the main body of the vertebra with the same methods with which the cement is currently deposited with the system of the prior art.

(29) The volume that must be filled by the granules is the same volume that is filled by the cement, it is a matter of just a few cc, more particularly of 1.5-2.0 cc.

(30) According to what has been described, the granules according to the present invention have medium sizes of the order of millimeters, necessarily smaller than the diameter of the cannula by which means the granules are introduced into the cavity of the vertebrae, but in any case a limited number of granules will easily fill the available volume.

(31) In order to facilitate insertion of the granules through the cannula, the use of a carrier substance, such as saline, serum, or other substance capable of assisting the sliding of the granules within the cannula by reducing the friction, may advantageously, but not necessarily be provided.

(32) Again, the granules can advantageously be connected to each other to form a chain by means of connecting means adapted to restrict the relative mobility of the granules, one with respect to the others.

(33) More particularly, according to a preferred embodiment of the present invention, the granules have a substantially spherical hollow shape and each sphere has a pair of slots located in diametrically opposite position, each of said slots being interconnected to a corresponding slot of an adjacent granule.

(34) A veritable chain of spheroidal granules is produced in this way so as to restrict the relative mobility of the granules, one with respect to the other.

(35) Thanks to this expedient, i.e. the presence of connecting means that restrict the relative mobility of the granules, the further advantage of compacting the granules within the cavity of the vertebrae, which is filled in an orderly fashion by the granules, is obtained. The fact of connecting the granules to each other allows greater control of the deposition process thereof within the vertebral cavity by the surgeon.

(36) Once the granules have uniformly filled the vertebral cavity, the primary stability is guaranteed by the fact that the granules fill the cavity in a compact manner, homogenously transferring the loads.

(37) Stability is then guaranteed by the osseointegration processes that the material the granules are made of and the trabeculated conformation of the surface are able to promote.

(38) The titanium and its alloys, in particular, are known in literature as having properties that are biocompatible and able to promote regeneration of the trabecular bone, and thus healing of the compromised bone, a result that is impossible to achieve with an inert material such as the current PMMA.

(39) The use of said granules in vertebroplasty or kyphoplasty surgeries is also the object of the present invention.