WO1995001864A1

WO1995001864A1 - Surgical prosthesis having a flexible hollow body, and device and method for producing same

Info

Publication number: WO1995001864A1
Application number: PCT/FR1994/000854
Authority: WO
Inventors: Claude Ugray
Original assignee: Claude Ugray
Priority date: 1993-07-09
Filing date: 1994-07-08
Publication date: 1995-01-19
Also published as: FR2707156A1; FR2707156B1

Abstract

A prosthesis having a flexible shell (21') made of a biocompatible material and moulded as a single shaped hollow piece by injecting the moulding material from the pouring ladle into a mould (1) through a core (14) which is positioned and supported within the mould (1) by an elongate tube (13). The core (14) is rigid and hollow and the core wall (15) has injection holes (14'). Said tube (13) and said holes (14') in the core (14) enable a vacuum to be created in the mould (1) before casting. The moulded wall of the shell (21') has a variable thickness defined by the shape of the casting recess as determined by computer modelling to generate the shape of the mould (1) and the mould core (14).

Description

SURGICAL PROSTHESIS WITH HOLLOW AND FLEXIBLE BODY, DEVICE AND METHOD OF MANUFACTURE

The invention relates to the technical field of surgical prostheses, and more specifically relates to a prosthesis with a hollow and flexible body, intended for use in plastic surgery and / or anatomical reconstruction, as well as to its method and device for fabrica¬ tion. The particularity of the process makes it possible to control the thickness of the walls and the shape of the prosthesis or implant by adapting it as best as possible to its use.

This adaptation is preferably defined and controlled beforehand by a computer modeling study (similar to those carried out in the industry for mechanical parts) taking into account the characteristics of the material from which it is made. implant and the forces exerted on it in situation (gravity, muscular pressure, particular shocks), and also the wear and aging of the material in the long term.

This preliminary study ensures the best possible suitability of the implant, thus defined, for its use. It determines the production of a casting mold necessary for the implementation of the manufacturing process. As a particular application, the surgical prosthesis according to the invention is a breast implant, the hollow body of which consists of a flexible shell of a biocompatible synthetic material and, preferably, prerem¬ fold of physiological saline. Numerous embodiments of such surgical prostheses are already known. In particular, breast implants have already been used, the hollow body of which consists of a flexible shell, of which at least the part of the external envelope is made of a synthetic material, such as medical silicone.

It has been known since 1988 that the external surface of such flexible surgical implants must have a micro-texturing to avoid the defense reaction of the organism consisting mainly of the formation, around the prosthesis, of a fibrous shell creating a hardening of the tissues resulting from the secretion of collagen fibers by myofibroblasts, and which, over time, becomes hard or even stony and adopts an increasingly spherical form, this reaction may be accompanied by side reactions such as tissue inflammation, intense macrophagic contact reaction, even creation of giant multinucleated cells with large vacuoles filled with migration or infiltration silicone, when the im¬ plant used is filled with liquid or gel silicone. This microtextured external surface is a surface which has hollows, for example from 20 to 400 μm in depth, perpendicular to the surface, which make it possible to disorganize the constructive structure of the collagen fibers.

It should be noted that the common techniques for manufacturing such implants make it possible to obtain a microtextured surface by taking an impression of the microtex¬ ture of a mandrel soaked in a tank of polymerizable liquid, generally silicone. After several soaking, the layer of material formed around the mandrel is deemed to be of sufficient thickness. The pocket thus produced is then turned over like a glove, to release it from the mandrel.

This manufacturing and microtexturing technique is relatively slow to implement and does not make it possible to obtain, in a single operation, a variation in the thickness of the wall of the pocket produced.

The present invention proposes to remedy these drawbacks. It allows the creation in a single pour of extra thicknesses of the wall. The advantage of local extra thicknesses of the wall of an implant is to stiffen the implant and these parts and / or allow the formation of anchoring bridges. It also introduces the possibility of a more elaborate shape search on the external and / or internal face of the wall of the implant.

This freedom of design is authorized by the production of the casting mold of the invention, and reinforced by the surface microtexture of the implant which attenuates the formation of a fibrous shell, deforming the implant in the long term, and which s opposes aesthetic research so far.

To this end, the invention provides a method of manufacturing an implantable surgical prosthesis, in particular a breast implant, with a hollow and flexible body, having the desired anatomical shape, consisting of a shell made of a flexible and biocompatible material. , such as a silicone elastomer or a hydrogel, and having a filling orifice, and which is characterized in that it comprises a step which consists in molding this shell in shape and in a single flexible membrane, possibly of thickness variable, by injection of a flexible and biocompatible mouldable material, such as a polymerizable composition can be, in a mold having an internal imprint whose shape corresponds to the external shape of the shell, and with a micro-textured surface , and in which a hollow and rigid core, with a wall pierced with injection orifices, and the shape of which corresponds to the shape of the internal housing of the shell, is positioned in the mold by a single key formed by 'a thin, elongated tube. This key constitutes an access axis to the pouring trough. It defines the filling opening of the shell produced. The moldable material is injected into the casting trough through the key channel, through and through the core and the holes in the wall of the core. The embodiment of the shell molding also comprises p ^r éalablement to injecting the moldable material (α compositi pclymérisa- ble), the creation of the vacuum suction of air into the casting cavity in the core and in the key, by a suction nozzle, connected to a pump outside the mold, and positioned in the key. This suction nozzle works independently from the injection circuit of the casting material. On this condition, it can therefore be separated or included in the injection valve of the casting material positioned on the key and out of the mold. In addition, the stage of making the shell by molding also comprises, after the creation of the vacuum inside the hollow for casting the core and the key, the opening of a valve hitherto hermetically closed, and by which a volume of moldable material, equal to the volume of the casting hollow, enters the mold. This material sucked in by the vacuum takes its place in the hollow.

Advantageously, this operation being carried out, the moldable material being positioned in the casting cavity, a gas is then blown through the injection valve under low pressure for the time necessary for the moldable material to transform into a flexible molded shell. This air pressure avoids the incrustation of said material in the orifices of the wall of the core through which it entered the hollow. Finally, the casting material being formed in a solid and flexible shell molded around the core, the mold is opened. The pressure of the blown gas is then increased which distances the flexible shell and unmoulds it around the core. The invention also relates to an implantable surgical prosthesis, of the breast implant type with a hollow and flexible body having a substantially asymmetrical cone shape with rounded apex, and comprising a shell with a micro-textured external surface and molded in shape in a single layer. of a flexible and biocompatible material, with a filling orifice, by the method as defined above, and which is characterized in that its flexible shell has a variable thickness in different parts of the shell, one of which substantially conical shape, connects to a substantially flat base by a thinned free edge. Advantageously moreover, at least one of the parts of the flexible shell present in its partial thickenings- the at least one anchoring bridge projecting inwards or outwards from the hull.

Such a prosthesis makes it possible to avoid the formation of a fibrous shell over the entire external surface of its body, and can have an appropriate shape and an optimal consistency, in particular thanks to a modulation of the thickness of the wall of the flexible body, in particular an extra thickness of a part of the base allowing in-vivo anchoring bridges, as well as by the thinning of the edge connecting the relatively flat base of the prosthesis to its domed part.

The invention finally relates to a device for manufacturing the flexible shell in a single piece of biocompatible material of an implantable surgical prosthesis, in particular of a breast implant, by the method as presented above, the device characterized in that it comprises a mold for casting in at least two complementary mold parts, each provided with a hollow imprint with micro-textured surface, and closing against each other so that their definite imprints feels an internal imprint of shape corresponding to the external anatomical shape of the shell, a hollow and rigid core, the external shape of which is that of the internal housing of the shell, and which is positioned in the mold by a key formed by 'a thin and elongated tube, constituting an access axis, so as to delimit between the micro-textured surface of the internal imprint of the mold and the external surface, possibly microtextured, of the core, a ladle e having the shape of the shell, the core having a wall pierced with injection orifices, and being in communication with the e .rieur of the mold through d- the key delimiting a coach. →. for the aspiration of air in the ladle, in the core and in the key, before aspiration by vacuum then, optionally, injection under pressure, in the ladle of a moldable material constituting said biocompatible material, then gas blowing under pressure in the key and the core and towards the surface and the holes in the wall of the core.

Other advantages and characteristics of the invention will emerge from the description given below, without implied limitation, of an exemplary embodiment described with reference to the appended drawings in which:

FIG. 1 schematically represents the mold for casting a breast implant,

- Figure 2 shows, schematically and partly in cross section, the core and the key cooperating with the mold of Figure 1, as well as external communication circuits, for the creation of the vacuum in the mold before casting, for 1 'supply of material possibly injected and pressurization with a gas, - Figures 3, 4 and 5 show schematically, in cross section, three characteristic stages of the molding and demolding process of a breast implant using d a mold and a core similar to those of FIGS. 1 and 2, FIGS. 6 and 7 represent, respectively in vertical median section and in lateral elevation, a possible shape of the shell of the implant,

FIG. 8 shows, in vertical and schematic cross-section, another form of implant shell, and

- Figure 9 shows schematically in perspec¬ tive a core used to mold the shell of Figure 8.

The device for molding the hollow and flexible body of a breast implant comprises a casting mold 1 according to FIG. 1, comprising two half-molds 2 and 3 complementary, connected to one another by a mechanism of opening and closing 4 making it possible to apply and maintain the half-molds 2 and 3 one against the other by their planar facing faces 5 and 6, as well as to open the mold 1 by spreading the half-molds 2 and 3 from each other, to remove the molded body therefrom. In each of the faces 5 and 6 is recessed an imprint 7 or 8, the entire surface of which is micro-textured. When the half-molds 2 and 3 are closed against each other, with centering provided by a key 13, described below with reference to FIG. 2, the imprints 7 and 8 together define an internal imprint of the mold 1, and the shape of which corresponds to the desired external anatomical shape of the body to be molded.

This external anatomical shape, visible in FIGS. 6 and 7, is a shell shape 21 substantially in an asymmetrical cone with a rounded top 22 and a base 23 which is substantially flat and oval to which the substantially conical wall 24 is connected by a free edge. 25 thinned and full, defined by the constricted periphery 9 and 10 of the half-cavities 7 and 8. The base 23 may have s external anchoring bridges such as 26, and / or internal te as 27, projecting respectively towards the outside and towards the inside of the base 23 of the shell 21 (see FIG. 6), resulting from the presence of reliefs 11, projecting or recessed in the imprints 7 and 8 of the half-molds 2 and 3, and complementary or inverted volumes corresponding to those of these reliefs 11 (see FIG. 1). The anchoring bridges may be straight and extend across the base 23, as shown in solid lines at 26 and 27 in FIG. 7, or even circular or oval and substantially concentric, as shown in broken lines in the figure. 7.

The molding device also comprises a core 14, the external shape of which defines the internal anatomical shape of the body to be molded. The rigid core 14, shown in FIG. 2, is hollow and in one piece with a cylindrical key 13. The wall of the core 14 is perforated with orifices 14 'for injection. The shape of its external surface 15 corresponds to the shape of the internal housing of the flexible body to be molded, which is hollow, and the core 14 is positioned in the internal cavity of the mold 1 by the key 13 at 13 ′ and 13 ", so that a ladle, in the form of a shell of variable thickness constituting the flexible and hollow body, and analogous to the shell 21 of FIG. 6, is delimited between the micro-textured surface of the imprint (7-8) and the external surface 15 of the core 14. Depressions of the outer surface 15 of the core

14, such as the depressions 18 and 19 in FIG. 2, define extra thicknesses in the wall of the molded body, such as the extra thickness 28 of the base 23 in FIG. 6. This extra thickness 28, projecting towards the inside of the shell 21, stiffens the base 23 of the latter, and makes it possible to provide internal anchoring bridges 27 in this base 23.

The substantially conical wall 24 of the molded shell 21 may also have additional thicknesses such as 29 (FIG. 6), defined by corresponding depressions such as 19 in the surface of the core 15 (FIG. 2).

A possible variant of the anatomical shape of the shell-molded body 21a of an implant of another type is diagrammatically shown in FIG. 8. The implant has a smooth external surface and an internal volume partially partitioned by internal projections 30 , defined by depressions 31 of symmetrical shapes complementary to a corresponding core 14a (see FIG. 9), rigid and hollow, in one piece with a tubular key 13a, and the wall of which is also pierced with injection orifices 14'a.

The protrusions 30 partially partition the implant 21a, and can provide a valve function in this implant of another type, which can be opened at 32a to the circulation of a fluid. In this case, the external surface 15a of the core 14a

(Figure 9) can also be microtextured.

The key 13 (in FIG. 2), of cylindrical and elongated shape, which is housed in the recesses 13 'and 13 "of the half-molds 2 and 3 respectively when the mold 1 is closed, acts not only as a suspension axis of the core 14 in the cavity, but also of the centering axis of the half molds 2 and 3 when mold 1 is closed.

In addition, the key 13 also has a thin tube structure delimiting an access channel, intended to put the outside of the mold 1 in communication with the inside. Two independent circuits, one from the other, are connected to the end of the key 13 projecting from the mold 1, by means of a three-way valve 17 with at least two positions.

Thus, the key 13 is extended towards the outside of the mold, on the one hand, by the suction nozzle 12 connecting the valve 17 to a vacuum pump (not shown) of a vacuum circuit for the mold 1 closed, and, on the other hand, by the conduit 16 of a distribution circuit, possibly under pressure, of a liquid polymerizable composition to be injected into the mold, in controlled volume, for molding a shell such as 21 ( f ure 6) in a silicone elastomer for example.

The valve 17 can, in one position, close herméti¬ cally the connection between the conduit 16 and the key 13 and, simultaneously open the communication between the key 13 and the suction nozzle 12. In a second position, the valve 17 puts the key 13 in communication with the conduit 16 by cutting the connection with the suction nozzle 12.

After the core 14 and the key 13 have been placed in the half-molds 2 and 3, and the mold 1 is closed, the flexible and hollow body is molded according to a process now described with the aid of FIGS. 3 to 5.

The molding is carried out in three main stages: 1) the mold 1 is hermetically closed as well as the connection of the key 13 with the conduit 16 by the valve 17, which allows, by the nozzle 12 in communication with the key 13, a suction of the air contained in the ladle 20, the core 14 and the key 13 (see FIG. 3). 2) the communication between the key 13 and the nozzle 12 is then closed by the valve 17, which puts the key 13 in communication with the conduit 16, and the core 14 and the orifices 14 ′ on its wall are introduced by the key 13, and in the ladle 20, a volume of polymerizable product equal to the volume of the shell to be molded, ( Figures 3 to 5 relative to the shell 21 of Figure 6, has only internal anchoring bridges such as 27).

Firstly, the vacuum prevailing in the mold 1 creates an aspiration of the polymerizable material, assisted secondly by a low pressure of air blown through the conduit 16 into the whole of the mold 1 and maintained during the time of polymerization of the pouring liquid. This air pressure maintains the pouring material in the pocket 20 and prevents the polymerized shell 21 'from becoming encrusted in the openings 14' of the core 14. 3) after polymerization, the half-molds 2 and 3 are open; the polymerized shell 21 ′ is then molded around the wall of the core 15. Through the conduit 16, the air pressure is increased to facilitate the release of the shell 21 ′ (FIG. 5) from around the wall of the core 15 through the opening 32, corresponding to the passage of the key 13, this orifice makes it possible to fill the shell 21 * with a fluid such as physiological saline before it is closed.

The hollow and flexible body is thus produced by injection molding of a shell 21 'of the desired anatomical shape and in a single piece or flexible membrane, of variable thickness, with a free edge 25 thinned between the base appreciably plane 23 and the substantially conical face 24, and the entire external surface of which is micro-textured, the shell 21 'having an opening 32 which can be closed if necessary by vulcanization after filling.

In the process for manufacturing the shell described above, the advantage of injecting the polymeric material by the core 14 is to provide micro-structuring of the surface of the implant and to modulate the thickness of its wall.

In the casting space 20, the extra thicknesses internal 28, 29 to the shell 21 (FIG. 6) are obtained by corresponding reductions (depressions 18, 19) in the volume of the core 14, and the external extra thicknesses 26 of the se 23 of the implant by a corresponding increase in the volume of the imprint of the mold, thanks to the reliefs 11 recessed in the imprint of the mold 1 (see FIG. 1).

The shape and thickness of the wall of the shell of the implant being controllable by the shapes given to the casting mold and to its core, these shapes and thicknesses can therefore be defined by computer modeling prior to making the mold. This ensures that the shape of the implant matches the thickness of its walls with the characteristics of the casting material used.

Claims

CLAIMS 1. Method for manufacturing an implantable surgical prosthesis, in particular a breast implant, with a hollow and flexible body, having the desired anatomical shape, consisting of a shell (21, 21 ') made of a flexible material and biocompatible, such as a silicone elastomer or a hydrogel, and having a filling orifice (32), characterized in that it comprises a step consisting in molding the shell (21, 21 ') in shape and in a single flexible membrane, possibly of variable thickness (28, 29), by injection of a moldable material forming said flexible and biocompatible material, such as a synthéti¬ that polymerizable composition, in a mold (1) having an internal imprint (7 -8) whose shape corresponds to the external shape of the shell (21, 21 '), and with a micro-textured surface, and in which a hollow and rigid core (14), with a wall pierced with injection orifices ( 14 '), and whose shape corresponds to the shape of the internal housing of the shell (21, 21 '), is positioned by a single key (13) formed of a thin and elongated tube constituting an access axis, defining the filling orifice (32) of the shell (21, 21'), the moldable material being introduced, it is injected into the impression (7-8) by means of a regulation nozzle by the key (13), the core (14) and the orifices (14 ') of the wall of the core (15 ).

2. Method according to claim 1, characterized in that the production of the shell (21, 21 ') by molding also comprises, prior to the introduction or injection of the moldable material, the creation of the vacuum by suction air present in the mold cavity (7-8) of the mold (1), in the key (13) and in the core (14).

3. Method according to claim 2, characterized in that the step of producing the shell (21, 21 ') by molding also comprises, at least after the introduction or injection of the moldable material, an insufflation of gas under pressure by the key (13), in the core (14) and towards the surface (15) and by the orifices (14 ') of the wall of the latter.

4. Method according to claim 3, characterized in that the gas insufflation comprises, before the opening of the mold (1) a first period of insufflation, at low pressure, during at least during the transformation of the moldable material injected in said flexible and bioσompatible material.

5. Method according to claim 4, characterized in that the gas insufflation comprises, at least after the opening of the mold (1), a second period of insuffla¬ tion, at higher pressure than during the first period.

6. Implantable surgical prosthesis, of the breast implant type, with a flexible and hollow body having a substantially asymmetrical cone shape with rounded apex (22), and comprising a shell (21) with micro-textured external surface and molded into a single shape layer of a flexible and biocompatible material, with a filling orifice (32), by the method according to any one of claims 1 to 5, characterized in that its flexible shell (21) has a variable thickness (28, 29 ) in different parts of the shell (21), one of which (24) of substantially conical shape, is connected to a base (23) substantially planar by a thinned free edge (24).

7. Prosthesis according to claim 6, characterized in that at least one of the parts (28-29) of the shell

(21) flexible has at least one anchoring bridge projecting inward (27) or outward (26) of the hull.

8. Device for manufacturing the flexible shell (21, 21 ′) in a single piece of biocompatible material of an implantable surgical prosthesis, in particular of a breast implant, by the method according to one of claims 1 to 5, characterized in that it comprises a mold (1) for casting into at least two complementary mold parts (2, 3), each provided with a hollow imprint (7, 8) with a micro-textured surface , and closing against each other so that their imprints define an internal imprint (7, 8) of shape corresponding to the external anatomical shape of the shell (21, 21 '), a hollow and rigid core (14), the external shape of which is that of the internal housing to the shell (21, 21 '), and which is positioned in the mold (1) by a key (13) formed by a thin and elongated tube constituting an access axis, so as to delimit between the surface micro-textured of the internal imprint (7-8) of the mold (1) and the external surface of the wall (15) of the core, possibly microtextured, a ladle (20) having the shape of the shell (21, 21 '), the core (14) having a wall pierced with orifices (14') and being in communication with the outside of the mold (1) by the key (13) and the nozzle (17), creating a vacuum by the aspiration of air in the ladle (20), in the core (14) and in the key (13), before injection, possibly under pressure, in the ladle (20) of a moldable material const ituting said biocompatible material, then blowing pressurized gas into the key (13) and the core (14) and towards the surface of the core (15) and the orifices (14 ') in the wall of the core (14 ).

9. Device according to claim 8, characterized in that the surface of the core (15) has at least one depression (18, 19) providing an additional thickness (28, 29) towards the internal housing of the shell (21, 21a).

10. Device according to one of claims 8 and 9, characterized in that the imprint (7, 8) of at least one mold part (2, 3) has at least one relief (11) in hollow or in projection for forming an anchoring bridge (26, 27) of corresponding volume in the shell (21).