Abstract:
An implant and a method for producing an implant for plastic surgery comprising an injection stage, wherein an elastomeric material is injected into a mould in order to produce a flexible envelope for forming a pocket.

Description:
PRIORITY CLAIM  
       [0001]     This patent application is the U.S. National Phase of International Application No. PCT/FR/2004/001890, having an International Filing Date of Jul. 16, 2004, which claims priority to French Patent Application No. FR-03 09102, having a Filing Date of Jul. 24, 2003, the disclosures of which are incorporated herein by reference in their entirety.  
       FIELD OF THE INVENTION  
       [0002]     This invention relates to the technical field of artificial devices of the implant or prosthesis types, designed to remodel the shape of part of the human body, for aesthetic and/or therapeutic purposes.  
         [0003]     This invention relates more particularly but not exclusively to the domain of breast implants designed to assure breast reconstruction following a mastectomy, or to increase the size of the breasts for aesthetic purposes.  
         [0004]     This invention relates to a plastic surgery implant designed to be implanted in the body of the patient, the said implant comprising at least one flexible pouch delimiting a predetermined internal volume, the said flexible pouch being formed from at least one envelope made from an elastomer material.  
         [0005]     This invention also relates to a process for making a plastic surgery implant.  
       BACKGROUND OF THE INVENTION  
       [0006]     It is known that a foreign body can be implanted in the body of the patient to perform plastic surgery, either to reconstruct a part of the body for example following an accident or a disease, or for aesthetic purposes to modify the appearance of part of the body.  
         [0007]     In particular, it is known that an implant can be placed in a patient&#39;s breast to create a breast implant in order to reconstruct and increase the volume of the breast following a mastectomy and/or for aesthetic purposes.  
         [0008]     It is also known that such foreign bodies can be implanted for purely aesthetic purposes in the buttocks, the legs, the arms or for example the pectoral muscles.  
         [0009]     These foreign bodies are generally referred to as a “prosthesis” or “implant”, and are usually in the form of a flexible envelope, for example made from a biocompatible elastomer material, containing a quantity of a filling material, for example such as a silicone gel or physiological serum which gives the functional volume to the prosthesis.  
         [0010]     These implants are usually inserted subcutaneously by making an incision close to the final implantation zone of the implant.  
         [0011]     In the special case of breast implants, they are usually inserted subcutaneously at the patient&#39;s thorax, on or under the pectoral muscle, by making an incision that may be made close to the armpit, along the sub-mammary groove, or around the areola of the nipple.  
         [0012]     Such plastic surgery implants are usually made by dipping.  
         [0013]     The dipping process consists of dipping a core with the required shape for the implant (for example hemispherical, ovoid, ellipsoid) in a silicone bath dispersed in a solvent, drying the film formed on the surface of the core by this dipping, and then “stripping” the core to obtain a flexible pouch.  
         [0014]     Another frequent technique is insert moulding of the pouch obtained by dipping so as to obtain a flexible envelope formed from a stack of layers.  
         [0015]     Each layer may be different from the others, the surface layer in particular having texture properties facilitating its implantation.  
         [0016]     Such a dipping manufacturing process is generally satisfactory, but it has many disadvantages.  
         [0017]     Due to the presence of an inflammable and toxic solvent in the dipping bath, special equipment has to be used both for the machines and for the civil works (explosion-proof room) to guarantee the safety and health of operators.  
         [0018]     Furthermore, this process is particularly difficult to implement because it requires precise control over the fluidity of the dipping bath, which requires surveillance and constant re-supply of solvent, since the solvent is usually very volatile. Therefore, this process requires highly qualified personnel.  
         [0019]     This process also includes a large number of tasks particularly justifying the use of a conveying carousel, such that the resulting cycle time to obtain an implant is relatively long.  
         [0020]     Moreover, the dipping process is generally incapable of precisely controlling the thickness of the envelope of the implant. Implants obtained by dipping are generally satisfactory, but they do not have sufficient dimensional precision resulting in overthickesses in some parts of the implant which increases production costs of the implant, or underthicknesses in other places which could possibly cause weakening of the implant.  
         [0021]     Finally, the scope of this process is limited particularly because it cannot be used to achieve controlled variations of the thickness and/or shape on the same part. Consequently, the design of a plastic surgery implant to be produced using this process depends on a liquid running on a core, which considerably reduces the possibilities of combining shapes, dimensions and finally functions, on the same part.  
       SUMMARY OF THE INVENTION  
       [0022]     The features of the present invention are to correct the various disadvantages listed above and to propose a new plastic surgery implant with higher strength and better uniformity.  
         [0023]     Another feature of the invention is to propose a new process for fabricating a plastic surgery implant to be used for simpler and more reliable fabrication of implants, at lower cost.  
         [0024]     Another feature of the invention is to propose a new process for fabricating a plastic surgery implant to fabricate implants quickly and with an excellent dimensional uniformity.  
         [0025]     Another feature of the invention is to propose a new process for fabricating a plastic surgery implant, with a smaller number of steps.  
         [0026]     The features of the invention are achieved using a process for fabrication of a plastic surgery implant characterised in that it comprises an injection step in which an injection press is used to inject an elastomer material into a mould to obtain a flexible envelope that will participate in the formation of a pouch ( 2 ).  
         [0027]     The features of the invention are also achieved by means of a plastic surgery implant to be implanted into the body of a patient, the said implant being obtainable by a fabrication process according to one of claims  1  to  5 , characterised in that the said implant comprises at least one flexible pouch delimiting a predetermined internal volume, the said flexible pouch being formed from at least one envelope made from an elastomer material, the dimensional tolerance of the thickness of the said at least one envelope being between 1% and 20%.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     Other features and advantages of the invention will become clearer after reading the following description with reference to the appended drawings that are given purely for illustrative and non-limitative features, in which:  
         [0029]      FIG. 1  shows a side view of a mould in a closed position used to implement the process according to the invention,  
         [0030]      FIG. 2  shows a side view of the mould in  FIG. 1  in the open position, and in the stripping position,  
         [0031]      FIG. 3  shows a diagrammatic view of a plastic surgery implant with a multi-layer pouch according to the invention,  
         [0032]      FIGS. 4 and 5  diagrammatically show a top view and a side view respectively of a first exemplary embodiment of a breast implant according to the invention,  
         [0033]      FIGS. 6 and 7  diagrammatically show a top view and a side view respectively of a second exemplary embodiment of a breast implant according to the invention.  
         [0034]      FIGS. 8 and 9  diagrammatically show a top view and a side view respectively of a third exemplary embodiment of a breast implant according to the invention. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0035]     FIGS.  3  to  9  show a plastic surgery implant  1  according to the invention.  
         [0036]     In the following, “plastic surgery” means surgery designed to modify the shape of an organ or a part of the body, so as to correct a congenital or acquired anomaly, and/or to modify the aesthetics of the body of a patient, for example to increase the volume.  
         [0037]     The plastic surgery particularly includes a branch called “aesthetic surgery” that is particularly applicable to remodelling of parts of the body for essentially aesthetic purposes.  
         [0038]     Therefore, this invention relates to plastic surgery, and preferably aesthetic surgery.  
         [0039]     The plastic surgery implant  1  conforming with the invention is designed to be inserted under the skin of a patient to reconstruct and/or remodel and/or increase the volume of a part of the body, for example a breast, to the extent that the said implant that has a predetermined functional volume increases the size of or replaces biological tissues, for example and preferably breast tissues.  
         [0040]     The insertion of the plastic surgery implant  1  conforming with the invention is usually and preferably done by inserting the said implant  1  subcutaneously by making an incision previously made by the surgeon.  
         [0041]     In the special case in which the implant  1  is a breast implant (see FIGS.  4  to  9 ), the said breast implant may in particular be implanted using an axillary, sub-mammary, peri-areolar or trans-areolar method.  
         [0042]     The plastic surgery implant according to the invention may for example be an arm implant (forearm, biceps), a leg implant (calves, thighs), a buttock or a chest implant (breast implant for women, pectoral implant for men). The breast implant will be the preferred example of plastic surgery implants within the scope of the invention.  
         [0043]     The plastic surgery implant  1  according to the invention conventionally comprises a flexible pouch  2  delimiting a predetermined internal volume, controlled by its external walls.  
         [0044]     The said at least one flexible pouch  2  is preferably made from elastomer materials, for example based on one or several silicones. The flexible pouch  2  may be made using a single layer construction, in other words it is formed from a single envelope (not shown) or a multilayer method, in which the flexible pouch  2  is formed from the stack of different envelopes  2 A,  2 B possibly with different compositions and/or properties.  
         [0045]     In particular, the flexible pouch  2  may be a complex formed from a stack of layers  2 A,  2 B fixed relative to each other, preferably over their entire surface of each layer. Therefore, the flexible pouch  2  is preferably a single-piece unit.  
         [0046]     Such a multilayer construction can provide a properties gradient depending on the thickness of the pouch  2 , in other words for example an excellent seal provided by the internal layer  2 A, and a “velvety” texture conferred by the external layer  2 B.  
         [0047]     Without going outside the scope of the invention, it would also be possible for the implant  1  to include two pouches (not shown) with different volumes, one contained in the other and each containing a different filling material.  
         [0048]     The following description refers particularly to a single flexible pouch  2  formed from a two-layer complex and made by stacking an internal layer  2 A and a surface layer  2 B, as shown in  FIG. 3 .  
         [0049]     However, without going outside the scope of the invention, it would be possible for the flexible pouch  2  to comprise a larger number of layers, for example three, four, five or more.  
         [0050]     Conventionally, the predetermined internal volume defined by the flexible pouch  2  contains a filling material  3 , which gives the required consistency and functional volume to the implant  1 .  
         [0051]     As a person skilled in the art is well aware, the filling material  3  may be a liquid, a gel or even a gas. For example, the filling material  3  could be a silicone gel, a saline solution, a physiological liquid, soya oil, polyvinylpyrrolidone (PVP) or a hydrogel.  
         [0052]     According to one important characteristic of the invention, the dimensional tolerance T of the nominal thickness e nom  of at least one of the envelopes  2 A,  2 B participating in formation of the pouch  2 , is between 1% and 20%, in other words the real thickness e real  of the envelope  2 A may vary between e nom (1−T) and enom(1+T).  
         [0053]     In other words, the general concept of the invention is based on the presence of an envelope  2 A,  2 B with a tolerance T between 1% and 20%, regardless of whether this envelope alone forms a pouch  2  or if it is associated with other envelopes in a multilayer structure.  
         [0054]     In the case of a multilayer structure (for example shown in  FIG. 3 ), one or several or even all envelopes  2 A,  2 B may have the dimensional tolerance characteristic conforming with the invention.  
         [0055]     For example, if the dimensional tolerance T is 10%, namely 0.1, the real thickness e real  may vary between e nom (1−0.1) and e nom (1+0.1), in other words between 0.9 e nom  and 1.1 e nom , for the envelope  2 A,  2 B considered.  
         [0056]     Any metrological method usually used in industry can be used to check if a particular envelope  2 A,  2 B actually satisfies the dimensional tolerance mentioned above.  
         [0057]     For illustrative and non-limitative purposes only, a metrological method could be adopted using the following steps:  
         [0000]     a. calculate the deviation E using the following formula: 
 
 E= 100( e   max   −e   nom )/ e   nom  if | e   max   −e   nom   |≧|e   min   −e   nom |
 
         [0058]     or 
 
 E= 100( e   nom   −e   min )/ e   nom  if | e   max   −e   nom   |≦|e   min   −e   nom |
 
         [0059]     where: e nom  could be considered to be the arithmetic mean of envelope thicknesses recorded at a significant number N of measurement points distributed on the envelope, e min  being the minimum measured thickness on the N points and e max  being the maximum measured thickness on the N points.  
         [0000]     a. comparison of E with T:  
         [0060]     if E|≦|T, the checked envelope is conforming with the purpose of the invention.  
         [0061]     The thickness measurement may be made using a mechanical thickness comparator, for example the Mitutoya mechanical comparator NO7304.  
         [0062]     Obviously, all N measurement points must be chosen such that they are all applicable to the same material category. Thus, care will be taken in general to assure that no measurement point is placed on a singularity of the envelope  2 A,  2 B, regardless of whether this singularity consists of a joint plane, a reinforcement (for example at a valve), or any other element.  
         [0063]     Advantageously, the dimensional tolerance of the thickness of envelope  2 A,  2 B is within a range varying from 15% to 20%. For example, it is worth mentioning the case of a silicone envelope with a nominal thickness equal to approximately 0.5 mm with a tolerance between 15% and 20%. This means that the nominal thickness of the envelope  2 A,  2 B is 0.5 mm, while the real thickness can vary from between 0.5±0.075 mm (when the tolerance T is equal to 15%) to between 0.5±0.1 mm (when the tolerance T is equal to 20%).  
         [0064]     In the above, we considered the case of an envelope  2 A,  2 B made of silicone, or based on silicone. However, it would be quite possible for this envelope to be made from any other material, and particularly elastomer, without going outside the scope of the invention.  
         [0065]     The invention also relates to a process for fabrication of a plastic surgery implant  1 , the said implant being designed to be implanted subcutaneously into the body of a patient.  
         [0066]     Preferably, the invention relates to a process for fabrication of a plastic surgery implant from the following group: 
        breast implant,     pectoral implant,     leg implant,     arm implant,     buttocks implant.        
 
         [0072]     According to one important characteristic of the invention, the fabrication process comprises an injection step in which an injection press is used to inject an elastomer material such as silicone into a mould to obtain a flexible envelope  2 A,  2 B that will participate in the formation of the pouch  2  of the implant  1 .  
         [0073]     Therefore, the fabrication process is an injection moulding process performed using an injection press, in other words an injection moulding press. Therefore, the term “injection” in this description must be understood as being related to an operation performed using a press, rather than a simple transfer of material such as by pouring, which could be done without an injection press.  
         [0074]     Preferably, the injected elastomer material is not very foaming or foamy, and is more in “solid” form.  
         [0075]     In general, the process according to the invention is designed to eliminate practically all air bubbles that could be trapped within the elastomer material. Thus, the process can be used to obtain a regular and homogenous flexible envelope that can be used in particular to form the outside shell of a surgical implant.  
         [0076]     Advantageously, the mould comprises:  
         [0077]     an upper cavity  40  comprising a concave conformation  40 A forming a hollow defining a portion of the surface of the flexible envelope to be obtained,  
         [0078]     a lower cavity  41 , comprising a concave conformation  41 B that defines a hollow defining a surface complementary to the surface of the upper cavity  40 , such that when the upper cavity  40  comes into contact with the complementary lower cavity  41 , the result is a closed internal volume with a fairly good seal delimited by a surface  40 A,  41 A, with a shape that corresponds approximately to the shape of the required flexible envelope  2 A,  2 B.  
         [0079]     The mould also comprises a core  42  formed by a convex body for which the outside surface is practically complementary to the outside surface of the internal volume defined by the upper cavity  40  and the lower cavity  41 , except on a different scale. The outside surface of the core  42  is thus geometrically similar to the surface of the internal volume defined by the upper cavity  40  and the lower cavity  41 , but is smaller. The core  42  will be positioned within the internal volume, preferably equidistant from the walls defining the internal volume. The result is thus described in  FIG. 1 , in which the upper cavity  40  and the lower cavity  41  surround the core  42 , so as to define an interstice or air gap  43  that is a free space delimited firstly by the outside surface  42 A of the core  42 , and secondly by the inside surface  40 A,  41 A of the internal volume defined by the upper cavity  40  associated with the complementary lower cavity  41 .  
         [0080]     In the purely illustrative case corresponding to  FIGS. 1 and 2  in which it is required to obtain an approximately spherical and single-piece envelope, the injection process thus includes a mould preparation step before the injection step, in which a generally hemispherical-shaped upper cavity  40  is brought into contact with a complementary generally hemispherical-shaped lower cavity  41 , so as to obtain an approximately spherical internal volume, after positioning the two cavities  40 ,  41  concentrically with the said internal volume, a spherical core  42  with a diameter less than the diameter of the said internal volume defined by the upper cavity  40  and the lower cavity  41 . This mould preparation step is followed by an injection step in which an elastomer material such as for example gum silicone or liquid silicone is injected into the interstitial space between the core  42  and the upper cavity  40  and the lower cavity  41 , so as to obtain a generally spherical shaped envelope  2 A,  2 B that will participate in forming the pouch  2  of the implant.  
         [0081]     Advantageously, the cavity  40  is fixed to an upper flange  44 , such that the inner space  40 B defined by the concave conformation  40 A of the cavity  40  is in fluid communication with the upper flange  44 , that itself supports the elastomer material injection means, that are themselves in communication with the injection press (not shown).  
         [0082]     The injection means preferably include three injection nozzles distributed at regularly distributed angles (spacing of 120°) around or at the summit  45  of the internal volume defined by the upper cavity  40  and the lower cavity  41 . The summit  45  is thus approximately at the concave conformation point  40 A of the upper cavity  40  closest to the upper flange  44 .  
         [0083]     Preferably, all injection nozzles have exactly the same flow.  
         [0084]     Advantageously, the process also uses a lower flange  46  on which a centring shaft  47  of the core  42  is fixed. The core  42 , which may for example be in the form of a solid sphere as shown in  FIGS. 11 and 12 , comprises a reaming  48  with a shape complementary to the shape of the centring shaft  47  so that the core  42  can be force fitted onto the shaft  47 , through the lower cavity  41  in which a slot  41 B is formed for the centring shaft  47  to pass through.  
         [0085]     The reaming  48  and the centring shaft  47  are designed to limit any risk of seizure between the core  42  and the centring shaft  47 . Consequently, the steels from which the core  42  and the centring shaft  47  are made must preferably have different hardnesses, for example 49 or 50 HRc for the centring shaft  47 , and 35 HRc for the core  42  (Rockwell hardness).  
         [0086]     It is also envisaged to be able to provide the centring shaft  47  with a generally tapered base  47 A, and an also generally tapered opposite engagement end  47 B. The reaming  48  formed in the core  42  comprises a lower recess  48 B at each of its ends with a shape complementary to the shape of the base  47 A, and an upper recess  48 B with a shape complementary to the shape of the engagement end  47 B, the said centring shaft  47  and the reaming  48  being arranged so as to facilitate annular bearing between the base  47 A of the centring shaft  47  and the core  42 , the said annular bearing contributing to control over positioning of the core  42  with respect to the centring shaft  47 .  
         [0087]     The stripping operation is performed using a stripping shaft  49 , one of the ends is fixed to the lower flange  46 , while the other end or the leading end  49 A is designed to engage the lower recess  48 B of the core  42 , and consequently is provided with a conformation authorising the lower end  48 B of the reaming  48  to stop in contact with it. The core  42  of the lower cavity  41  can thus be extracted as follows:  
         [0088]     the upper cavity  40  and the lower cavity  41  are separated,  
         [0089]     the lower cavity  41  is then moved in a vertical translation movement along the direction of the centring shaft  47 , so as to take the core  42  away from the centring shaft  47 ,  
         [0090]     the sub-assembly formed by the lower cavity  41  supporting the core  42  is then inserted on the stripping shaft  48  so as to extract the core  42  outside the concave conformation  41  A of the lower cavity  41 .  
         [0091]     The final step is actual stripping of the silicone envelope matching the surface of the core  42 . The core  42  will advantageously be covered by a surface treatment coating limiting adhesion of elastomers, for example a uniform layer of Teflon® a few micrometers thick, to facilitate this operation.  
         [0092]     Thus, the process according to the invention provides a means of quickly producing a flexible envelope with a very uniform wall thickness, using a single machine and in a limited number of operations (the cycle time may be of the order of 5 minutes). For example, an envelope  2 A,  2 B made of silicone with a nominal thickness equal to 0.5 mm can be made with a tolerance of less than ±0.08 mm and possibly ±0.05 mm.  
         [0093]     Advantageously, the process according to the invention includes a complexing step after the reinjection step in which the flexible envelope  2 A obtained after the injection step is covered with a surface envelope  2 B by a dipping operation, to obtain a flexible pouch  2  similar to that shown in  FIG. 3 .  
         [0094]     This dipping operation preferably takes place as follows:  
         [0095]     the flexible envelope  2 A obtained by injection is inserted on a dipping core,  
         [0096]     the assembly formed by the core covered with the flexible envelope  2 A is dipped in a suitable bath using any well-known dipping technique, so as to cover the flexible envelope  2 A with a surface envelope  2 B, for example made of silicone.  
         [0097]     This provides a means of combining the benefit of fast injection with texture effects such as a “velvet” type texture, that can be obtained by dipping.  
         [0098]     The result is thus a flexible pouch  2  in the form of a multilayer complex, in other words a material formed by stacking of different material layers.  
         [0099]     There are two of these layers in the example in  FIG. 3 , it being understood that a larger number of layers will be quite possible without going outside the scope of the invention.  
         [0100]     In the case of a multilayer pouch  2 , it would also be possible for each of the envelopes  2 A,  2 B forming the pouch  2  to be obtained by injection, without going outside the scope of the invention.  
         [0101]     Many shapes of implants can be made using the process according to the invention, and particularly breast implant shapes like those shown diagrammatically in FIGS.  3  to  9 .  
         [0102]     The invention can be used in industrial applications for the fabrication of plastic surgery implants.