FR2744010A1 - Osseous implant manufacturing procedure, for e.g. osteosynthetic screws or tibial fixation plates etc - Google Patents

Abstract

The procedure consists of cutting out and shaping a blank (10b) made from a section of perforated sheet material, especially stainless steel. Depending on the requirement of the implant, the blank can be shaped, for example, into a cylinder with a ribbed or spiral outer surface, and fitted with auxiliary components such as end stoppers or screw heads and pointed tips. The blank can be shaped, for example, by bending it round a matrix (11) and compressing it with jaws (15), to produce the required shape. Implants made using the procedure can be employed as vertebral intersomatic implants, long bone reinforcements or joint prostheses.

Description

 The present invention relates to a method for manufacturing bone implants comprising an internal cavity and lateral openings putting this cavity in communication with the outside. The anchoring of these implants to the bone is carried out by bone growth in said cavity, through said openings, such implants being in particular intended to be implanted in cancellous bone.

 Depending on their dimensions, the implants obtained by this method can in particular be inter-vertebral cages, osteosynthesis or fixation screws for prosthetic elements, in particular screws for fixing tibial plates of knee prostheses or acetabular prostheses, so-called "interference" screws for fixing the ends of a prosthetic ligament to a bone, or anchor rods for articulation prosthesis elements.

 Such implants are currently produced by machining, which implies substantial material means and numerous successive operations.

 These implants therefore have the disadvantages of being particularly long, delicate and expensive to manufacture.

 In addition, the manufacture of existing implants presents limits as to the shape or dimensions that it is possible to give to these implants or as to the thickness or the nature of the material used.

 The present invention aims to remedy these drawbacks.

To this end, the process to which it relates consists
- to constitute, by cutting, shaping and possibly drilling operations, a part forming a main part of the implant, so that this part delimits an internal cavity and includes holes or cutouts of shape, dimensions, density and distribution adapted to the implant to be manufactured, and
- to fix on the part obtained complementary elements making it possible to constitute the implant, in particular plugs or walls for closing the cavity, in the case where the implant to be obtained is an inter-vertebral cage, a screwing head and a end point, in the case where the implant to be obtained is a screw, a part which can receive a hinge means, in the case where the implant to be obtained is a hinge prosthesis element, longitudinal reinforcements or other.

 Thus, the method according to the invention allows the manufacture of bone implants without any complex machining, but only by simple and rapid operations of cutting, shaping and possibly drilling a part forming a main part of the implant, then d assembly of this piece of complementary elements to constitute the implant.

 This process has great flexibility of implementation.

 Indeed, the part forming a main part of the implant can be arranged in a material whose shape, thickness or nature can be chosen without restriction depending on the implant to be manufactured. This part can in particular be fitted out from a tube section, when the implant to be obtained is a part of revolution, or by conformation and possible assembly of one or more blanks cut from a flat piece of material, in particular a sheet stainless steel.

 This tube or this flat part can have an openwork structure, in mesh or lattice, so that it is not necessary to drill holes therein.

 In the case of a part with a non-perforated structure, the shape, dimensions, density and distribution of these holes can also be chosen without restriction, depending on the implant to be manufactured.

 The arrangement of the holes can be carried out before any shaping of the blank (s), in particular by drilling or with a punch.

When said part forming a main part of the implant is fitted from a flat piece of material, the method according to the invention consists
- To carry out in any order the following operations: cutting from a flat piece of material, such as a sheet, of at least one blank of dimensions adapted to the dimensions and to the shape of the implant to be obtained; arrangement, if necessary, of holes or cutouts through this or these blanks
- to carry out in any order the following operations: shaping, and, if necessary, assembling this or these blanks to each other to constitute a part delimiting an internal cavity assembling the adjacent edges of the wall of this part, to confer continuity to this wall, and
- to attach additional elements to the part obtained to constitute the implant.

 The shaping of the blank can be carried out by mechanized means, and the assembly of the adjacent edges of the part obtained as well as the fixing of any additional parts can be carried out by welding.

 The method according to the invention is in particular intended for the manufacture of bone implants comprising circular projections or a support support thread in the bone.

When said part forming the main part of the implant is formed from a section of tube, the method consists, after the operations of cutting this section of tube and possible fitting of the holes
- to deform this section of tube so as to arrange said circular projections or said thread, and
- to carry out the aforementioned operation of assembly of the complementary elements making it possible to constitute the implant.

When said part forming the main part of the implant is formed from a blank, the method consists, after the operations of cutting this blank and of any arrangement of the holes
- rolling the blank so as to form a tubular part forming the blank of the part to be obtained;
- To carry out in any order the following operations: deformation of this blank so as to arrange said circular projections or said thread; assembly of the adjacent edges of the blank or of the part obtained after deformation, and
- to carry out the aforementioned operation of assembly of the complementary elements making it possible to constitute the implant.

 The deformation of the tube section or of the tubular blank is in particular carried out by engaging this tube or this blank on a matrix comprising the relief to be arranged in the part to be obtained, and by tightening this tube or this blank radially around the matrix at jaw means comprising a relief complementary to that of the die, or by "fluo-turning", that is to say by circulating a roller, with radial pressing, around this tube or this blank, at the level of the hollow parts of the matrix.

 These projections and net allow, in addition to the support of the implant in the bone, to radially stiffen the side wall of the implant. Implants of small diameters, made of thin material, which can hardly be produced by machining, can thus be easily manufactured using the method according to the invention.

 The holes can be arranged outside the portions of the tube or the blank intended to be deformed to constitute the circular projections or the turns of the net. These holes can also be arranged on said portions intended to be deformed, so as to extend at least partially on the outer edge of the projections or of the thread. The deformation of the tube or the blank makes it possible to project the edges delimited by the holes. The implant obtained thus has circular protrusions or an aggressive thread coming to sharpen the bone wall in which the implant is inserted, which makes it possible to promote bone growth.

 For a good understanding, the invention is again described below with reference to the appended diagrammatic drawing representing, by way of nonlimiting examples, several stages of implementation of the process which it relates to, and several bone implants obtained by this process.

Figure 1 is a perspective view of a perforated blank, from which a main part of a bone implant is made
Figure 2 is a perspective view of a tubular part obtained by a rolling operation of the blank of Figure 1
Figure 3 is a perspective view of the tubular part and a device for its forming, before a forming operation
Figure 4 is a perspective view of the tubular part after forming, before assembly with an additional element for constituting the implant
Figure 5 is an enlarged view of a portion of the wall of this implant
Figure 6 is a side view of an inter-vertebral cage obtained by the method according to the invention
Figure 7 is a longitudinal sectional view of this cage, after implantation between two vertebrae and establishment of a complementary arthrodesis device
Figure 8 is a side view of two inter-vertebral cages connected to each other
FIG. 9 is a view in longitudinal section of a part obtained by the method according to the invention, before assembly with two complementary elements making it possible to constitute a bone screw
Figure 10 is a longitudinal sectional view of a bone screw obtained by the method according to the invention
FIG. 11 is a view in longitudinal section of an "interference screw" obtained by the method according to the invention, and
Figures 12 and 13 are perspective views of two articulation prosthesis elements, also obtained by this method.

 FIG. 4 represents a bone implant 1 formed by assembling a tubular part 2, forming the main part of the implant, and a head 3. The part 2 comprises radial openings 4 placing the internal cavity which it delimits in communication with the outside, the anchoring of the implant 1 to the bone being produced by bone growth in this cavity, through the openings 4.

 Figure 1 shows a blank 5 from which the part 2 was made.

 This blank 5 has been cut from a sheet, for example of stainless steel. I1 comprises a series of holes 6 arranged in an area 5a of its surface, but is devoid of such holes in an area 5b of this same surface.

 As can be deduced from FIGS. 2 to 4, the length and the width of this blank 5 correspond respectively to the circumference and to the length of the part 2.

To obtain the latter
- the blank 5 is rolled, until a substantially tubular part 10 forming the blank of the part 2 is obtained, as shown in FIG. 2
- The tubular part 10 is engaged, as shown in FIG. 3, on a matrix 11 of cylindrical envelope, having a diameter corresponding substantially to that of the part 10, or slightly greater; this matrix 11 comprises a portion 11a in which a series of grooves 12 is arranged, and a portion 11b devoid of such grooves 12, the part 10 being positioned on the matrix 11 so that its portion 10a corresponding to the portion 5a of the blank 5 extends over the portion 11a of the matrix 11, while its portion 10b corresponding to the portion 5b of the blank 5 extends over the portion 11b
- The matrix 11 and the part 10 are then engaged between three jaws 15 which can be moved radially, capable of coming to clamp the part 10 around the matrix 11; each of these jaws 15 has a rounded end surface, extending over a circular arc of 120 degrees, so that in the clamping position the jaws 15 completely envelop the part 10; portions 15a of these surfaces include projections 16 in an arc, of a shape complementary to that of the grooves 12, and are intended to come to apply in clamping position on the portion 10a of the part 10 so that these projections 16 come to engage in these grooves 12; portions 15b of these end surfaces have a cylindrical wall segment shape and are intended to be applied in the clamping position on the surface 10b of the part 10, and
- The adjacent edges 10c of the part 10 are then assembled to each other by welding.

 As can be seen in FIG. 4, the part 2 has, following the clamping operation of the part 10 around the matrix 11, a series of circular projections 20 at its part 2a corresponding to the part 10a, and a tubular part 2b, corresponding to the part 10b of the part 10.

 The head 3 is engaged and is fixed by welding in the cavity delimited by this part 2b. It includes for example an axial recess 21 with a hexagon socket allowing the implant 1 to be mounted on an impact tool and the possible rotation of this implant when it is placed in the bone.

 The end of the implant 1 opposite the head 3 can, for its part, be closed by welding a transverse wall in the form of a circular patch.

 It appears in Figure 4 that the openings 4 extend at least partially on the outer edge of the projections 20, the corresponding holes 6 having been arranged so as to be located in particular at the portions of the part 10 intended to be deformed to form the projections 20.

 As shown in FIG. 5, the deformation of the part 10 to form these projections 20 makes it possible to project the edges 22 delimited by the openings 4 extending on the external edge of the projections 20.

 The part 2 thus has a relatively aggressive outer wall at the level of these projections 20, coming to sharpen the bone wall in which the implant 1 is inserted, which makes it possible to promote bone growth.

 FIGS. 6 and 7 show an implant 30 constituting an intersomatic cage, of structure similar to that of implant 1.

 This implant 30 is intended to receive a graft or chips of cancellous bone and to be inserted into a bore arranged between two vertebrae 31, 32 located on either side of a damaged intervertebral disc 33. Bone growth through the lateral openings 4 allows the fusion of the graft and the cancellous bone of the vertebrae 31, 32, and immobilizes these two vertebrae.

 This implant 30 is produced in the aforementioned manner, except that, in this case, the matrix comprises not successive grooves 12 but a thread, and that the jaw clamping surfaces comprise portions of thread, complementary to the thread of the matrix.

 After deformation of the tubular part 10, the implant 30 comprises a thread 35 allowing it to be screwed between the vertebral plates previously resected from the vertebrae 31 and 32.

 In the example shown, the openings 4 are arranged outside the net 35. These openings could of course be located on the turns of the net 35, to give this net, in the aforementioned manner, a relatively abrasive surface allowing to sharpen the cancellous bone of the vertebral plates.

 In addition, FIG. 7 shows that the tubular portion 30b is, in this example, tapped and comprises lateral notches 36 for its mounting on a screwing instrument. Once the implant 30 is in place, this portion 30b can receive a threaded plug of the same type as the above-mentioned head 3.

 The arthrodesis device 40 represented in FIG. 7 is of the same type as that described in document FR-A-2 681 776, the content of which is incorporated into the present description by reference, and will therefore not be particularly described.

 FIG. 8 shows that two implants 30, when they are put in place by the anterior approach, can be connected to each other by means of a rod 45 and two sets 46 for tightening this rod 45.

Each of these assemblies 46 being provided with a threaded stud 47, screwed into the threaded bore of the corresponding portion 30b of the implant 30. The assemblies 46 are of the same type as those described in the document
FR-A-2 681 776.

 The portion 30b can, in general, be used for mounting any type of complementary means for fixing the implants 30, if necessary.

 Figures 9 and 10 show bone screws 50, 51 made in the same way as the implant 30. In this case, the tubular part 52 receives by welding a screw head 53 at one end and a tip 54 at its other end .

 FIG. 9 shows a screw 50 with a relatively large diameter core and a thread 55 of limited height, more particularly intended to be inserted into cancellous bone, for carrying out osteosyntheses or fixing prosthetic elements such as tibial plates of knee prosthesis or acetabular elements of hip prosthesis, while FIG. 10 shows a screw 51 with a core of smaller diameter than that of screw 50 and with a thread 55 of greater height, more particularly intended to be inserted into the cortical bone.

 The above method allows these different types of threads to be obtained simply by using dies 11 and jaws 15 of suitable shapes.

 FIG. 11 represents an "interference screw" 60, that is to say a screw allowing the fixing of the ends of a prosthetic ligament, in particular of the knee.

This screw is also formed by assembling a tubular part 62, similar to part 2, with a screw head 63 and a tip 64.

 Figure 12 shows a femoral stem 70 of hip prosthesis. In this case, the medullary part 71 of this rod 70 is produced by suitable cutting then folding of one, or, if necessary, two, sheet blank (s), previously perforated (s). This medullary part 71, once formed, receives an upper endpiece 72, comprising a femoral neck 73 at the end 74 in the form of a Morse cone, intended to support a spherical articulation head.

 FIG. 13 shows a medullary rod 80 for a trapezo-metacarpal prosthesis, comprising a flared metaphyseal part. In this case, the tubular blank 10 can be formed in a slightly conical shape and can be deformed cold or hot so as to take the flared shape shown in the drawing. Once shaped, the part 82 thus obtained receives an end piece comprising a support flange 83 and a central bore 84, this bore being intended to receive a neck secured to a spherical head.

 The invention thus provides a method allowing the manufacture of bone implants of very varied shape and dimensions, without any complex machining, but only by simple and rapid operations of cutting, drilling and shaping a blank, assembly of the adjacent edges of the part obtained, and possible assembly with this part of complementary elements making it possible to constitute the implant.

 These implants, once in place, are perfectly fixed to the bone by bone regrowth inside the cavity which they delimit. However, they remain easy to remove if necessary, by ablation or unscrewing of their head, and drilling inside their cavity to remove the bone that has grown back in this cavity.

Claims (10)

 RIVBNDICATIONS  - to be fixed on the part (2,52,62,71,82) obtained from complementary elements (3,53,54,63,64,72,83) making it possible to constitute the implant, in particular plugs (3) or closing walls of the cavity, in the case where the implant to be obtained is an inter-vertebral cage (30), a screwing head (53,63) and an end point (54,64), in the case where the implant to be obtained is a screw (50,51,60), a part (72,83) capable of receiving an articulation means, in the case where the implant to be obtained is an articulation prosthesis element ( 70.80), longitudinal or other reinforcements.  - to constitute, by cutting, shaping and possibly drilling operations, a part (2,52,62,71,82) forming a main part of the implant (4,30,50,51,60,70,80 ), so that this part delimits an internal cavity and includes holes (4) or cutouts of shape, dimensions, density and distribution adapted to the implant to be manufactured, and  1- Method of manufacturing bone implants comprising an internal cavity and lateral openings putting this cavity in communication with the outside, characterized in that it consists  2 - Method according to claim 1, characterized in that it comprises the operation of arranging the aforementioned part from a section of tube.  3 - Method according to claim 1, characterized in that it comprises the operations consisting  - to carry out in any order the following operations: cutting from a flat piece of material, such as a sheet, of at least one blank (5) of dimensions adapted to the dimensions and to the shape of the implant (4, 30.50.51.60.60.70.80) to be obtained; arrangement, if necessary, of holes (6) or cutouts through this or these blanks (5);  - To carry out in any order the following operations: shaping, and, if necessary, assembling this or these blanks (5) to each other to constitute a part (2,52,62,71,82) delimiting a cavity internal; assembly of the adjacent edges (10c) of the wall of this part (2,52,62,71,82), to give continuity to this wall, and  - to be fixed on the part (2,52,62,71,82) obtained from complementary elements (3,53,54,63,64,72,83) allowing to constitute the implant.  4 - Method according to claim 3, characterized in that it comprises the operation of arranging the holes (6) before any shaping of the blank (s) (5), in particular by drilling or punching.  5 - Method according to claim 2, characterized in that it consists, after the cutting operations of the tube section and possible arrangement of the holes  - to deform this section of tube so as to arrange circular projections or a thread, and  - to carry out the aforementioned operation of assembling complementary elements making it possible to constitute the implant.  6 - Method according to claim 3 or claim 4, characterized in that it consists, after the blanking operations (5) and possible arrangement of the holes (6)  - rolling the blank (5) so as to form a tubular part (10) forming the blank of the part (2.52) to be obtained;  - To carry out in any order the following operations: deformation of this blank (10) so as to arrange circular projections (20) or a thread (35,55); assembly of the adjacent edges (10c) of the blank (10) or of the part obtained (2.52) after deformation, and  - to carry out the aforementioned operation of assembling the complementary elements (3,53,54,63,64) making it possible to constitute the implant.  7 - Method according to one of claims 5 or 6, characterized in that it comprises the operations consisting in:  - carrying out the deformation of the tube section or of the blank (10) by engaging this tube or this blank (10) on a matrix (11) comprising the relief (12) to be arranged in the part (2) to be obtained, and  - tighten radially this tube or this blank (10) around the matrix (11) by means of jaws (15) comprising a relief (16) complementary to that of the matrix (11), or circulate a roller, with radial pressing , around this tube or this blank (10), at the hollow parts (12) of the matrix (11).  8 - Method according to one of claims 5 or 6, characterized in that it comprises the operation of arranging the holes (6) outside the portions of the tube or the blank (10) intended to be deformed to constitute the circular projections (20) or the turns of the net (35).  9 - Method according to one of claims 5 or 6, characterized in that it comprises the operation of arranging the holes (6) on the portions of the tube or the blank (10) intended to be deformed to constitute the circular projections (20) or the turns of the net (35), so that these holes (6) extend at least partially over the outer edge of the projections (20) or of the net (35).  10 - Bone implants comprising an internal cavity and lateral openings (4) putting this cavity in communication with the outside, as obtained by the method according to one of claims 1 to 9.