Surgical prosthesis including a woven mesh for surgical use and a method of manufacturing thereof

The present invention relates to a prosthesis including a woven mesh for surgical use, suitable for use with tension-free techniques and in particular with the tension-free sutureless technique.

More particularly the present invention relates to a prosthesis including a woven mesh for surgical use having properties of softness and extreme lightness (ultralightness), as well as stability.

More specifically, the present invention relates to a prosthesis including a woven mesh for surgical use, which is soft and ultra-lightweight as well as being stable, and is suitable for use as a prosthesis for hernioplasty, and more specifically for inguinal hernioplasty. The prosthesis according to the invention may also be used for repairing and reinforcing the abdominal wall and the inguinal region of the pelvic floor, and for the treatment of incontinence.

Hernia is the most frequent surgical problem throughout the world. It occurs when the intestines pass out of the abdominal cavity, where they are normally contained, through the muscular wall together with the peritoneum, which forms the hernial sac, that is the natural enclosure for the abdominal cavity.

The most frequent locations of this condition are: the inguinal region (inguinal hernia), the crural region, which is a little further down than the inguinal region and precisely at the head of the thigh (crural hernia), the umbilical and periumbilical region (umbilical hernia), the epigastric region which lies on the median line between the umbilicus and the xiphoid of the sternum (epigastric hernia). There are also other very much rarer types of hernia which may occur at several points in the abdominal wall.

Hernia takes the form of a non-painful swelling which can be reduced manually and is initially of small size. Over time it can however increase in volume, become painful and no

longer reducible.

The technique of hernipplasty comprises repairing and strengthening the yielding part of the muscular wall, thus closing the breach through which hernia formation has occurred.

Of the many reparatory surgical techniques available, there are some which use prostheses and are referred to as being tension-free, in that they permit the hernial defects to be repaired without sutures under tension, which may cause yielding and recurrence. Tension- free techniques do not provide for opening of the fascia trasversalis and substantially comprise positioning a prosthesis above that fascia, the prosthesis being secured with or without sutures.

In the situation where sutures are not provided in order to secure the prosthesis, the term tension-free sutureless is used. This recently developed technique is particularly suitable for the correction of inguinal hernia, and makes use of a prosthesis which is positioned so as to reinforce the posterior wall of the inguinal canal.

Prostheses developed according to the abovementioned tension-free sutureless technique are known for example from European Patent application no. EP 0 827 724 A2 in the name of Herniamesh S.r.l.. This application describes prostheses for hernioplasty constructed using a mesh of biocompatible plastics material and more precisely a pre-shaped mesh of polypropylene monofilament, preferably in the anatomical shape of a nail.

The mesh prosthesis described in the abovementioned patent application has the desired surgical quality, which is imparted by adequate porosity to encourage fibroblast infiltration and consequently resistance to infections; the said prosthesis is also stable, that is to say it does not tend to shrink, as a result of appropriate treatments which confer upon it so-called controlled memory. This prosthesis is however somewhat rigid and thick to be positioned and held in position without the need of sutures as envisaged in the tension-free sutureless technique. These properties are influenced by the diameter of the monofilament and the type of mesh and produce a mesh of some weight, which has the inconvenience that it may be somewhat uncomfortable for the patient, particularly when engaging in working and

sporting activities.

More generally, the . prostheses used with tension-free techniques are normally overdimensioned with regard to the actual tensions which they have to withstand. This gives rise to excessive quantity and a not insignificant weight of extraneous material introduced into the patient's body, which is therefore uncomfortable for the patient.

In order to overcome these disadvantages ultra-lightweight and macroporous surgical meshes have been developed. It is in fact known that the higher the porosity of the mesh the more rapid will be fibroblast infiltration, and consequently resistance to infections. These lightweight prostheses are currently available on the market. Mention will be made by way of example of the mesh prosthesis marketed by BARD S. p. A. under the name SoftMesh, or that marketed by Braun under the name Optilene. These mesh prostheses are however not sufficiently stable and tend to shrink, not only in the absence of sutures securing them to the musculature (which makes them unsuitable for applications using the tension-free sutureless technique) but also when the surgeon uses a tension-free technique, in that, since these prostheses cannot be readily held while extended, they are quite difficult to handle and position correctly in the intended anatomical position, and therefore do not guarantee either correct positioning or an adequate hold when sutures are present. When subjected to a pull in one direction these meshes also shrink considerably in the direction perpendicular to it.

To sum up, the prior art substantially offers two types of mesh prosthesis for surgical use:

(1) prostheses based on thick rigid meshes which ensure good mechanical stability because of the fact that they close off the hernial defect causing the maximum scar tissue formation; the mesh itself and the substantial scar formation ensure a lasting and strong repair of the hernia. These meshes, which have pore dimensions of typically less than 1 mm in both breadth and length and are suitable for use with the tension-free sutureless technique nevertheless have the disadvantage that they cause the patient some discomfort because of their rigidity and thickness. Cases of an excessive scar-forming response to the prosthesis causing rigidity in the abdominal wall with consequent discomfort for the

patient have also been reported in the literature;

(2) prostheses based on lightweight meshes which have been conceived in order to follow the physiological movement of the abdominal wall and the inguinal region are manufactured with a small monofilament diameter and large pores, typically larger than 1 mm in both breadth and length. These prostheses give rise to less scar tissue formation, but their excessive softness makes them very difficult to use with tension-free techniques and does not in fact make it possible to use the tension-free sutureless technique. They also have unsatisfactory mechanical properties.

The applicant has now selected a woven mesh which extremely advantageously combines the properties of stability and sufficient rigidity required for use as prosthesis in hernioplasty surgery using tension-free techniques, and more specifically the tension-free sutureless technique, with those of ultralightness, softness and macroporosity which render prostheses based on such mesh particularly comfortable for the patient and particularly effective in preventing the occurrence of infections, as well as being capable of reestablishing abdominal functions and being physiologically incorporated in the abdominal wall with maximum biocompatibility. A prosthesis based on such a mesh also reduces the occurrence of long term complications such as recurrence, infections or chronic pain, and also offers optimum handling properties for easy repair of the hernia, thus achieving a balanced relationship between the material introduced into the patient's body and the need for a correct and reliable hold.

Advantageously, therefore, the use of the woven mesh identified by the applicant for the construction of implantable prostheses for repair surgery, in particular hernioplasty, makes it possible to overcome the limitations of the prior art.

The present invention therefore relates to a surgical prosthesis including a woven mesh for surgical use comprising a biocompatible monofilament of plastics material, the said mesh having a weight per unit area within the range 25 to 100 g/m ² , a three-dimensional percentage porosity within the range 80 to 95% and a tensile strength in the longitudinal direction in the range of approximately 16 to 32 N/cm.

The two-dimensional porosity of the mesh is preferably 60%; values between 55% and 75% will however impajt the desired physical and mechanical properties to the mesh.

The abovementioned weight per unit area and porosity values are substantially comparable with those for lightweight meshes (for example BARD'S SoftMesh or FEG's Dynamesh-PP Light). However, the prosthesis according to the invention at the same time demonstrates mechanical properties which are superior to those of lightweight meshes, which make it more like heavy meshes. These properties make the aforementioned mesh particularly suitable for use as a prosthesis for the repair of hernial defects and defects of the abdominal wall using tension-free techniques, and more specifically using the tension-free sutureless technique.

In addition to this, advantageously, the mesh used for construction of the prosthesis according to the invention can be manufactured using simple and economical processes.

The prosthesis according to the invention will now be described in greater detail with reference to the following figures provided by way of a non-limiting example in which:

- figure 1 shows a plan view of a preferred embodiment of a prosthesis including a woven mesh for surgical use according to the invention,

- figure 2 shows a detail of the prosthesis in Figure 1 relating to the structure of the larger pores of the mesh and the four threads connecting two opposite sides of each of the aforesaid larger pores,

- figure 3 shows a detail of the prosthesis in Figure 1 relating to the structure of the smaller pores in the mesh,

- figures 4A and 4B show a diagrammatical plan view and lateral view respectively of a first embodiment of the prosthesis illustrated in Figure 1,

- figures 5A and 5B show a diagrammatical plan view and lateral view respectively of a second embodiment of the prosthesis illustrated in Figure 1,

- figures 6A and 6B show a diagrammatical plan view and lateral view respectively of a third embodiment of the prosthesis illustrated in Figure 1,

- figures 7 A and 7B show a diagrammatical plan view and lateral view respectively of a fourth embodiment of the prosthesis illustrated in Figure 1,

- figures 8A and 8B show a diagrammatical plan view and lateral view respectively of a fifth embodiment of the prosthesis illustrated in Figure 1,

- figures 9A and 9B show a diagrammatical plan view and lateral view respectively of a sixth embodiment of the prosthesis illustrated in Figure 1,

- figure 10 shows the bend angle for various types of mesh prosthesis for surgical use characterised by different weights.

With reference to Figure 1, a preferred embodiment of the prosthesis according to the invention which includes the woven mesh for surgical use indicated by 1 is illustrated diagrammatically. A mesh similar to mesh 1 is in itself known. For example it is manufactured by Tessitura TEXIVA s.r.l. (product code 18bisl2), but hitherto this mesh has only been used for applications such as the manufacture of industrial filters, which have nothing to do with medical devices and even less with prostheses for hernioplasty or other types of surgery using tension-free or tension-free sutureless techniques.

For the purposes of this description by woven mesh is meant a mesh manufactured using known techniques for weaving fabrics by weaving warp and weft threads.

Figure 1 shows an embodiment in which the prosthesis is shaped and includes a mesh 1 substantially shaped in the form of a nail, having two longer sides 7a, 7b which are substantially parallel to each other, joined at one extremity by a substantially straight shorter side 9 and at the other extremity by a side 11 having a curvilinear profile. The prosthesis including mesh 1 preferably has a hole 3 located approximately in the centre of the prosthesis, and a slit 5 which extends from said hole 3 parallel to said longer sides 7a, 7b as far as said shorter side 9. Hole 3 and slit 5 are obtained for example by a process of hot cutting with a predetermined shape.

Figures 4A and 4B respectively show a diagrammatical plan view and a lateral view of a preferred embodiment of the prosthesis according to the invention, that is a prosthesis substantially shaped in the form of a nail with a hole. By way of example, in this

embodiment the dimensions of the prosthesis are 45.00 mm x 100.00 mm, but they may have any value up to 80.00 mm x 150 mm according to the envisaged application; the hole diameter is 12.00 mm and the thickness of the mesh is from 0.59 mm to 0.8 mm.

Mesh 1, whose structure is illustrated in Figure 1, is manufactured from a monofilament of biocompatible plastics material produced by extrusion, preferably of polypropylene, which is woven through the use of suitable looms capable of producing a weave of the Raschel type. By a weave of the Raschel type is meant a system of knotted mesh weaving which renders the fabric non-running. This weaving is carried out using suitable looms known as Raschel looms.

Again with reference to Figure 1 it will be seen that according to the shape of the preferred embodiment illustrated therein mesh 1 has larger pores 4a and smaller pores 4b, as well as woven knots 6.

The diameter of the polypropylene monofilament constituting mesh 1 is preferably approximately 120 microns. However, a monofilament diameter which has any value within the range of 114 micron to 135 micron is sufficient to ensure the desired balance between the physical and mechanical properties of mesh 1 and its weight per unit area.

As far as the weight per unit area of mesh 1 is concerned, this is preferably 48 g/m ± 5 %; however, a weight per unit area of between 25 g/m ² and 100 g/m ² is acceptable in order to ensure the desired comfort for the patient.

On examination mesh 1 has larger pores 4a of substantially hexagonal shape. The substantially hexagonal shape of said larger pores 4a may be clearly seen in Figure 2. Each pore 4a is delimited by a ring having opposite sides (2a, 2b) connected by at least four threads (8a, 8b, 8c, 8d).

The presence of the said at least four threads 8a, 8b, 8c and 8d confers sufficient rigidity and stability upon mesh 1 for it to be used as a prosthesis in tension-free techniques, preferably in the tension-free sutureless technique.

This structure confers the desired stability and rigidity properties upon the mesh to ensure easy and secure positioning of the mesh. In addition to this the four threads 8a, 8b, 8c and 8d present in the hexagonal pore favour the use of adhesive as a means of attaching the prosthesis because they represent a suitable substrate for the material.

The dimensions of each larger pore 4a, in both breadth and length, suitable for ensuring the desired balance between the physical and mechanical properties of mesh 1 and its porosity, preferably lie between 2 mm and 6 mm. Preferred dimensions are 3.97 mm x 2.37 mm.

Figure 3 shows the substantially rhombus shape of smaller pores 4b. The dimensions of each smaller pore 4b in both breadth and length preferably lie within the range 2.25 to 2.36 mm; however a value of between 2.00 mm and 3.00 mm is suitable for ensuring the desired balance between the physical and mechanical properties of mesh 1 and its porosity.

The three-dimensional percentage porosity of mesh 1 is preferably 87.8% (equivalent to a mean pore area of approximately 890 x 10 ³ μm ² ); however a value of between 80% and 95% imparts the desired physical and mechanical properties upon mesh 1.

Reference should be made to Table 3 for a comparison between the meshes described in abovementioned European Patent application no. EP 0 827 724 A2 and other meshes in the prior art. In Table 3 the term "porosity" is used to indicate the mean area of the pores. Meshes according to the prior art have only one type of pore, while the preferred embodiment of mesh 1 used to manufacture the prosthesis according to the present invention has two types of pores, which are indicated as "large pores" and "small pores" in Table 3. In the rest of this description larger pores 4a and smaller pores 4b will sometimes be referred to as first pores and second pores respectively.

For the purposes of this description, by three-dimensional percentage porosity of mesh 1 is meant the ratio between the volume of the voids and the total volume expressed as a percentage.

Mesh 1 used to construct the prosthesis according to the invention is marked by optimum

stability which in addition to the structure of the mesh itself (in particular the diameter of the monofilaments and the configuration of pores 4a and 4b and knots 6, that is the type of weave), is also due to the presence of at least four threads 8a, 8b, 8c and 8d within each larger pore 4a of substantially hexagonal shape, as previously illustrated.

By the stability of the mesh is meant its ability to remain substantially flat and not shrink; this property essentially derives from the fact that the mesh has resistance to deformation.

As mentioned previously, the stability of mesh 1 depends among other things on the configuration of pores 4a and 4b and knots 6. Some mesh prostheses according to the prior art, for example the abovementioned SoftMesh mesh, have rhombus-shaped pores with two threads passing through each pore, which has the disadvantage of rendering the mesh less stable.

Optionally stability may be further improved by also subjecting the prosthesis including mesh 1 to a thermofixing process, which is a known process in the textile industry and is used to improve the dynamometric strength as well as the tear resistance and wear resistance of fabrics, as well as their thermal stability. The said thermofixing process has the result that the course of the threads in the weave is stabilised, that is to say the compression forces at the points at which they cross are reduced, thus rendering the fabric more flexible and easier to handle.

As a result of the abovementioned process the polypropylene monofilaments are further stabilised, while being marked by good physical and mechanical properties. A sample of mesh 1 used for the construction of a prosthesis according to the invention has been subjected to a series of evaluation tests carried out in a specialist research centre.

The sample of thermofixed mesh tested had dimensions of 150.00 mm x 150.00 mm and provided the following results:

- a mean size of 118.5 den - 132 dtex - 13.2 tex with a mean filament diameter of 135 μm (standard deviation 7.92 μm and coefficient of variance 5.9 %), the said size being determined on the basis of the mean filament diameter (in μm) and the filament density

(0.92 g/cm ³ ); the test was carried out using a Orthoplan optical microscope interfaced with an ASM 68K image analyser as the test instrumentation,

- a mean thickness of 0.46 mm; the test was carried out according to method UNI EN ISO 9073-2/1998, using a micrometer as the test instrumentation,

- a mean mass per unit area (weight) of 51.1 g/m ² corresponding to a mean mass of 0.203 g; the test was carried out according to method ISO 9073-1/1989 using a circular template of diameter 5.13 mm and an AE 163 analytical balance as the test instrumentation,

- a mean porosity of 87.8 %, corresponding to a mean pore area of 888.2 μm x 1000 μm (minimum pore area 14.9 μm x 1000 μm and maximum pore area of 2,814.6 μm x 1000 μm), the said porosity, expressed as a %, being determined on the basis of the mean mass per unit area (in g/m ), the mean thickness (in mm) and the filament density (0.92 g/cm ) by interpolation from 20 readings; the test was carried out using an ASM 68K image analyser interfaced with an Orthoplan optical microscope as the test instrumentation,

- a mean perforation resistance of 6.28 x 10 ² kPa corresponding to a mean applied perforating force of 20.1 kg; the test was carried out according to method ASTM D 3787/1989, using a lever dynamometer (sphere diameter 20 mm) as the test instrumentation,

- a tensile strength in three dimensions as shown in Table 1 below (in Which the longitudinal direction is the direction of the four threads 8a, 8b, 8c, 8d, identified in Figure 1 by arrow x):

Table 1

The test was carried out according to method ASTM D 1682/1964, using a CRE electronic dynamometer with a constant increase in elongation as the instrumentation, the initial distance being 100 mm, the width of the test specimen being 10 mm and the velocity of the cross-member being 50 mm/min, by interpolation from 2 test specimen, - a tear resistance in three directions according to Table 2 below (in which the longitudinal direction is the direction of the four threads 8a, 8b, 8c, 8d, identified in Figure 1 by arrow

X):

Table 2

the test was carried out according to method UNI EN ISO 13937/2002, using a CRE electronic dynamometer with a constant increase in elongation as the test instrumentation, the initial distance being 25 mm, the dimensions of the test specimen, one in each direction, being 20 mm x 120 mm, and the velocity of the cross-member being 100 mm/min.

Unlike the meshes available on the market, such as for example Dynamesh-PP mesh, which are soft and corrugated and must therefore be secured with sutures in order to perform as desired, the prosthesis including mesh 1 according to the invention which has the abovementioned stability characteristics remains flat in the appropriate anatomical position and can therefore be positioned without sutures in accordance with tension-free sutureless hernia repair techniques.

This stability also makes the prosthesis easier to handle when it is being positioned anatomically, and the prosthesis can therefore be optimally positioned; stability then helps to hold the prosthesis in position over time and prevents it from shrinking and being displaced.

With reference now to Figures 5 to 9, these illustrate a number of embodiments of the prosthesis according to the invention which the applicant feels that it will be useful to describe briefly, in that they can be potentially used for applications other than hernioplasty.

Figures 5 A and 5B show a diagrammatical plan view and a lateral view respectively of an embodiment of the prosthesis according to the invention in which the prosthesis is substantially shaped in the shape of a nail without a hole. Preferably the dimensions of the said prosthesis are 45.00 mm x 100.00 mm, but may have any values up to 60.00 mm x

120 mm depending upon the envisaged application, the thickness of the mesh being preferably of any value between 0.59 mm and 0.78 mm.

Figures 6A and 6B show a diagrammatical plan view and a lateral view respectively of an embodiment in which the prosthesis is shaped in a substantially circular shape. Preferably the diameter of this prosthesis is 7.00 mm, but it may be reduced down to 5.00 mm depending upon the envisaged application, the thickness of the mesh being preferably 0.59 mm.

Figures 7A and 7B show a diagrammatical plan view and a lateral view respectively of an embodiment in which the prosthesis is shaped in a substantially elliptical shape. Preferably the dimensions of this prosthesis are 80.00 mm x 120.00 mm, but they may have any value up to 140.00 mm x 190 mm depending upon the envisaged application, the thickness of the mesh being preferably 0.80 mm.

Figures 8 A and 8B show a diagrammatical plan view and a lateral view respectively of an embodiment in which the prosthesis is shaped in a substantially square shape. Preferably the sides of the said prosthesis are 150.00 mm, but may have any value up to 300.00 mm depending upon the envisaged application, the thickness of the mesh preferably having any value from 0.45 mm to 0.80 mm.

Figures 9A and 9B show a diagrammatical plan view and a lateral view respectively of an embodiment in which the prosthesis is shaped in a substantially rectangular shape. Preferably the dimensions of the said prosthesis are 80.00 mm x 150.00 mm, but may have any value from 60.00 mm x 110.00 mm to 250.00 mm x 355.00 mm depending upon the envisaged application, the thickness of the mesh preferably having any value from 0.45 mm to 0.80.

As an alternative to the embodiments illustrated in Figures 5 to 9, which are all substantially two-dimensional, mesh 1 may also be used to make three-dimensional prostheses. By three-dimensional prosthesis is meant a prosthesis made using mesh 1 provided with three dimensions during processing in order to obtain a medical device characterised by three dimensions.

The prosthesis incorporating mesh 1 in the various possible embodiments described above is particularly suitable for surgical use, in particular for hernioplasty and in particular using the tension-free and mpre specifically the tension-free sutureless hernia repair techniques, because it is very light and soft while having a stable behaviour which is similar to that of the heavy rigid meshes described in European Patent application no. EP 0 827 724 A2 cited above.

Table 3 provides a comparison between the properties of a prosthesis according to the present invention and that of other meshes according to the prior art and, in particular, the meshes described in European Patent application no. EP 0 827 724 A2, the SoftMesh meshes from BARD S. p. A. mentioned above and a standard type of mesh which is also marketed by BARD. S.p.A. which has a rigidity intermediate between the above, as well as meshes from other manufacturers such as BRAUN and FEG.

The data provided confirm that the mesh used in this invention has ultralightness, softness and macroporosity as well as stability characteristics which make it particularly suitable for surgical use as prostheses, specifically for hernioplasty.

Table 3

As far as mechanical properties are concerned, the prosthesis according to the present invention constructed using mesh 1 has a tensile strength in the longitudinal direction which is less than that .of the heavy meshes but sufficient to guarantee repair of the defect in that it lies within the range of values from 16 to 32 N/cm which are regarded as physiological values in the literature. Preferably the strength of the prosthesis according to this invention is approximately 30 N/cm. This value does not go beyond the range of physiological values, unlike heavy meshes in which the tensile strength in the longitudinal direction reaches values of around 80-100 N/cm.

Finally, with reference to Figure 10, a comparative evaluation has been made between mesh 1 used in this invention and a number of meshes according to the prior art with regard to their stability characteristics. In particular Figure 10 is a diagrammatical representation of the bend angle from the horizontal plane observed for the following types of mesh: A = heavyweight mesh, with a weight per unit area of approximately 220 g/m ² ; B = ultra-lightweight mesh according to this invention, with a weight per unit area of approximately 34 g/m ² ; C = ultra-lightweight mesh according to this invention, with a weight per unit area of approximately 48g/m ² ; D = medium weight mesh, with a weight per unit area of approximately 127g/m ² ; E: ultra-lightweight mesh (weight per unit area approximately 48g/m ² ) according to the known art. The samples used for this measurement were preshaped meshes of dimensions 4.5 x 10 cm. Experimentally the prostheses were placed on a stable support and 1 cm of the mesh was attached thereto. The bend angle was measured from the horizontal direction clockwise using optical techniques.

As can be seen in Figure 10, heavyweight mesh A, as expected, is the most stable, having the least bend angle from the horizontal plane. Surprisingly meshes B and C according to the invention, although being ultra-lightweight, have because of their structure a bend angle which is not only less than that of the ultra-lightweight meshes according to the known art, but also than that of medium weight meshes.

In an alternative embodiment of the prosthesis according to the invention, the mesh constituting the prosthesis has only one type of pore, that is larger pores 4a, while smaller pores 4b are absent. This embodiment is less preferred, at least at the present time, than the

embodiment shown in Figure 1 characterised by two types of pores, that is larger pores 4a and smaller pores 4b.

In a further alternative embodiment provision is made for imparting non-slip properties brought about by greater roughness in at least one of the two surfaces of the mesh prosthesis, in order to improve its adhesion to the muscular wall. These properties may be imparted by known means. More specifically, non-slip properties may be imparted to the mesh by the method of manufacture, which makes one of the two sides of the mesh rough. As a consequence of this provision, that is giving the mesh one surface without non-slip properties and a reverse surface with non-slip properties, this alternative embodiment will provide a right handed and a left handed prosthesis which can be more suitably used according to the type of application, more specifically the side, whether the right hand or left hand, on which the patient has to be operated.

Advantages deriving from the use of the prosthesis including woven mesh 1 for surgical use according to this invention are obvious from the description given above; in particular:

- extreme lightness (ultra-lightness) provides maximum comfort for the patient in whom the prosthesis is implanted,

- softness allows the patient's abdominal functions to be re-established without giving rise to long term complications such as recurrence, infection or chronic pain,

- macroporosity has the effect of preventing the occurrence of infections following implantation of the prosthesis in the patient,

- macroporosity also has the effect that it is physiologically incorporated into the patient's abdominal wall, thus ensuring maximum biocompatibility,

- the combination of softness and adequate stability makes handling the prosthesis easier for the surgeon and enables it to be positioned more accurately in its intended anatomical position, for easier repair of the hernia,

- stability makes it possible for position to be maintained over time, thus avoiding incorrect positioning, which may give rise to tension, and thus also ensuring long term performance,

- adequate rigidity makes it possible to use the prosthesis for repair using the tension-free sutureless technique, therefore without the complications due to the presence

of sutures, and consequent further induced tensions.

In terms of the advantages conferred through the prosthesis including the woven mesh for surgical use according to the invention, the simplicity and economic nature of the process for manufacturing such meshes, and therefore the economy of the mesh itself, in addition to its reliability from the point of view of the absence of induced infections, must also not be undervalued.

It is obvious that the prosthesis including the woven mesh for surgical use according to the invention described herein through a preferred embodiment and its variants provided by way of a non-limiting example may be modified in ways known to those skilled in the art without thereby going beyond the scope of protection of this invention.

In particular the prosthesis including the woven mesh according to this invention has been designed for use as a prosthesis for hernioplasty, and more specifically for inguinal hernioplasty, and also for repairing and strengthening the abdominal wall and the inguinal region of the pelvic floor, and for the treatment of incontinence, but may however be validly applied in all those sectors of surgery, for example in gynaecology, which use tension-free or tension- free sutureless techniques.

In one embodiment which is designed to achieve a specific biological response to the prosthesis the mesh may be coated with a film of resorbable and/or non-resorbable polymer material on one or both sides. This film, which generally has a thickness of between a few microns and a millimetre, may be attached to the mesh by welding, sewing or chemical and physical and/or thermal techniques. As far as non-resorbable films are concerned, polypropylene films characterised by a specific microporosity likely to reduce problems caused by the occurrence of fistulas are preferably used. Among resorbable films, the use of polylactic acid (PLA) and polyethylene oxide (PEO) film obtained by solvent evaporation is preferred. Other resorbable and non-resorbable materials which may be used are silicone, polytetrafiuoroethylene, polyurethanes, polyglycolic acid, hyaluronic acid, polycaprolactone, and biological molecules such as for example collagen.

In another particularly preferred embodiment the prosthesis including the mesh for surgical use according to this invention is coated on at least one side with a coating network of fibres and nanofibres . of polymer material, the said fibres and nanofibres having a distribution of diameters within the range from 50 nanometres to 500 micrometres, preferably from 100 nanometres to 50 micrometres, as described in Italian patent application TO2007A000846 which is incorporated herein by reference.

The polymer materials which can be used to produce the fibre and nanofibre coating are materials capable of reducing and/or preventing adhesion and tissue erosion; reducing adhesion and bacterial growth and/or stimulating cell growth in a particular tissue. Among these mention may be made by way of example of polyethylene glycol, chiosan, polyglycolic acid, polylactic acid, hyaluronic acid, polycaprolactone, polyethylene oxide and biological macromolecules (such as for example collagen, cellulose, gelatin). Among these polyethylene oxide (PEO) and polylactic acid or lactic polyacid (PLA) are most preferred. PEO in fact makes it possible to improve the biocompatibility of the prosthesis and reduce bacterial adhesion, given that this material has greater compatibility with the physiology of the pelvic abdominal muscular wall. PLA makes it possible to obtain fibres with better biological and mechanical properties and with a rate of resorption which is more compatible with physiological needs.

The network of fibres and nanofibres characterising this embodiment of the prosthesis according to the invention is obtained by the electrospinning technique.

Electrospinning is a technique which makes use of interactions of an electrostatic nature to excite tensile forces. This technique makes it possible to obtain thin fibres thanks to uniaxial stretching of a viscoelastic jet originating from a polymer solution (or spindle).

The diameter of the fibres obtained is reduced by the repulsions exerted by the charges present on the surface. Elongation is obtained through a process in which traction is the result of the application of an electrical field, which involves the application of a high potential difference in order to induce the formation of a liquid jet comprising an extremely viscous polymer solution. The jet is then held continuously under tension by the

electrostatic repulsions exerted by the charges present on its surface, the solid fibre forms through evaporation of the solvent, which takes place in the section separating the needle from the collection plate. The electrospinning equipment may comprise one or more linear nozzles or nozzles positioned on rotating rollers in such a way as to obtain continuous deposition.

Use of this technique is particularly advantageous in that it makes it possible to deposit a network of fibres and nanofibres having a structure able to encourage cell colonisation and growth, thus encouraging incorporation of the prosthesis and at the same time reducing the risk of infections and complications. The network of fibres and nanofibres obtained is also characterised by a porosity of between a few nanometres and one hundred micrometres, which allows biological fluids to pass through the network, preventing the occurrence of serositis and haematomas.

The fibre and nanofibre coating obtained by electrospinning also makes the prosthesis easier to handle in both open and laparoscopic surgery, and encourages its attachment using either adhesive or sutures, or other securing techniques.

Finally, but not least importantly, the use of nanotechnological techniques of manufacture and the consequent production of a fibre coating having dimensions within the nanometric range makes it possible to improve the performance of the implanted prosthesis because the smaller quantity of material and the greater similarity to the environment and physiological conditions favour the biocompatibility of the device, consequently increasing the patient's comfort. The smaller quantity of implanted material also reduces the risks arising from degradation products which, although biocompatible and able to be disposed of through physiological metabolism, nevertheless give rise to overburdening of the organs responsible for such disposal.

The following example relates to deposition by the electrospinning technique of a coating network of PLA/PEO fibres and nanofibres on the prosthesis including macroporous ultra- lightweight mesh 1 according to this invention. This mesh is made of polypropylene and has the structure illustrated in Figure 1. The example is provided purely by way of

• illustration.

A solution of PLA/PE.O at a concentration of 20% in acetone was prepared. The ratio between the two PLA/PEO polymers by weight in the solution was 70/30. Other solvents which do not compromise the biocompatibility of the final product may be used as an alternative to acetone. Examples of suitable alternative solvents are dimethyl sulphoxide, methylene chloride, dioxan and chloroform.

Deposition of samples of PLA/PEO on the macroporous ultra-lightweight polypropylene mesh by electrospinning was carried out under the following conditions:

- Temperatures from ambient temperature to 60°C

- Atmospheric pressure

- Voltage of between 30V and 3OkV

- Capillary/collection plate distance of 15cm

- Capillary of 2 mm external diameter Teflon and approximately 0.5 mm internal diameter

- Collection plate of aluminium of any dimensions between 9cm x 1 lcm and 14cm x 17cm.

A network of fibres and nanofibres having a diameter of between 50 nanometres and tens of micrometres was obtained. The increased weight of the mesh is very small in comparison with the values for commercially available meshes, which has made it possible to maintain the innovative concept of reducing the quantity of material used and a composite lightweight mesh. The increase in weight of such meshes is indicatively between 0.1-10 mg per cm ² . Images (not shown) of the prosthesis coated with PLA/PEO by electrospinning as described above obtained using a scanning electron microscope (SEM) indicate that the PLA/PEO fibres/nanofibres are deposited on both the polypropylene thread and the porous areas, forming a continuous network.

Subsequent to deposition of the coating network of PLA/PEO fibres and nanofibres the adhesion between the support (that is the mesh) and the network may be further improved by subjecting the product to heat treatments and/or chemical treatments and/or steam treatments. As an alternative the stability of the two or more components may be increased by welding, or by sewing the two or more parts.

The conditions described above may be varied. The concentration of PLA/PEO in the solution may vary within the range from 5% to 50% by weight. The ratio between the two PLA/PEO polymers by. weight may vary from 100% PLA to 100% PEO, thus including all intermediate fractions between the two polymers (for example: PLA/PEO = 90/10, 70/30, or 50/50).