Patent Publication Number: US-2022211479-A1

Title: Barbed prosthetic knit and hernia repair mesh made therefrom as well as process for making said prosthetic knit

Description:
The present invention relates to a prosthetic knit equipped with barbs, capable of being rolled up on itself, then unrolled effortlessly. Such a knit can particularly be used for producing wall-reinforcing prostheses intended to be introduced into a patient by coelioscopy. 
     Wall-reinforcing prostheses, for example prostheses for reinforcing the abdominal wall, are widely used in the surgical field. These prostheses are intended to treat hernias by temporarily or permanently filling a tissue defect. These prostheses are generally made of biocompatible prosthetic fabric and can have a number of shapes, for example rectangular, circular or oval, depending on the anatomical structure to which they are to be fitted. Some of these prostheses are made from entirely bioresorbable yarns and are intended to disappear after having carried out their reinforcing role while cell colonization takes place and tissue rehabilitation takes over. Other prostheses comprise non-bioresorbable yarns and are intended to remain permanently in the body of the patient. 
     Some of these prostheses are made from an arrangement of yarns, a knit, a woven fabric or non-woven fabric, comprising barbs that protrude outwards from one face of the prosthesis: these barbs constitute hooks that are able to fix themselves either in another prosthetic fabric, belonging to the same prosthesis or not, or directly in the biological tissues, for example the abdominal wall. 
     Furthermore, for the sake of minimizing the traumatisms subsequent to any surgical operation, patients are increasingly often operated on via coelioscopic surgery when the type of operation carried out permits it. Coelioscopic surgery requires only very small incisions, through which a trocar is passed, within which the prosthesis is conveyed to the implantation site. Thus open surgery is avoided and the patient can leave hospital rapidly. Coelioscopic surgery is particularly popular in surgical operations carried out in the abdomen, such as for example the treatment of hernias. 
     However, the trocars used in coelioscopic surgery generally have a relatively small calibrated diameter, which may vary, for example, from 5 to 15 mm, in order to reduce the size of the incision made as much as possible. The prosthesis must therefore be conveyed within a channel of reduced diameter and it must then be deployed at the implantation site. 
     In order to carry out this step, the prosthesis is generally rolled up on itself in order to make it slide in the channel of the trocar or directly introduced by force. However, when the prosthetic fabric forming the prosthesis comprises barbs on one face, it may happen that these barbs become entangled in the body of the fabric and upset the subsequent deployment of the prosthesis at the implantation site. Furthermore, due to the fact that they are not protected, the barbs may be damaged during the unrolling of the prosthesis or during its transportation through the trocar to the implantation site. 
     Thus, there remains the need for a prosthetic fabric comprising barbs, that can be used for manufacturing prostheses, such as for example abdominal wall reinforcements, capable of being rolled up on itself in order to be conveyed within a channel such as that of a trocar, without damaging the barbs, and then capable of being completely deployed, and preferably in an easy manner, once it has reached the implantation site in the body of the patient. 
     The present invention aims to meet such a need. 
     A first aspect of the invention is a prosthetic knit based on at least a first yarn of biocompatible polymer material defining first and second opposite and openwork faces, and on at least a second biocompatible and heat-fusible monofilament yarn, forming barbs that protrude outwards from at least said first face and are obtained by melting loops generated by said second yarn, the chart followed for the knitting of said first and second yarns on a warp knitting machine having three guide bars B1, B2, B3 being the following, according to the ISO 11676 standard:
         Bar B1: 1.0/0.1//   Bar B2: 1.0/7.7/6.6/7.7//   Bar B3: 2.1/5.5/3.4/0.0//       

     said second yarn following the chart of bar B3. 
     The knit according to the invention has both openwork faces, which favour cell recolonization, and barbs, suitable for hooking into biological tissues or any other textile, and an ability to be rolled up on itself, then unrolled effortlessly. 
     The knit according to the invention can be used as is in order to constitute a reinforcing prosthesis for repairing a hernia, or it may constitute one part of a reinforcing prosthesis for repairing hernias: for example, it may be partially or completely coated over part or all of its faces with a coating made of a biocompatible, for example non-stick, material; alternatively or in combination, the knit according to the invention may be combined with another textile in order to form a composite reinforcing prosthesis. 
     In the present application, the expression “openwork face” is understood to mean that said face comprises openings or pores: these openings or pores are in particular generated by the chart followed for the knitting of the yarns of the knit according to the invention, and may correspond to the various meshes of said knit. 
     The barbs of the knit according to the invention may protrude from the first face substantially perpendicular to the plane of said face or alternatively along one or more planes that are inclined relative to the plane of said face. These barbs are intended to function as fastening means, either by becoming entangled in one or more arrangements of yarns, fibres, filaments and/or multifilaments of another prosthetic fabric, for example in order to form a composite reinforcing prosthesis, or by anchoring directly in the biological tissues, such as for example an abdominal wall, once the prosthesis comprising this knit or constituted of this knit is implanted. Generally, these barbs have the shape of a shaft, having the diameter of the yarn used for their formation, surmounted by a head having a diameter greater than that of the shaft. 
     In the knit according to the invention, the chart followed for the knitting of the yarns of the knit generates a particular structure of the knit, that is to say a specific arrangement between the various openings of the faces of the knit, the respective size of these various openings and the position and distribution of the barbs being such that, even if some of the barbs present on the first face are caused to be trapped within some of the openings present on the second face when the knit is rolled up on itself under the effect of an external stress, such as for example the stress exerted by the surgeon when he rolls the knit or the prosthesis comprising the knit up on itself in order to introduce it into a trocar, and subsequently the stress exerted by the internal walls of the trocar, then a large number of the barbs trapped will be released automatically, or under the effect of a very small unrolling force, when said stress is relieved. 
     The knit according to the invention can be used to produce a reinforcing prosthesis for repairing a hernia. Thus, when the surgeon wishes to implant a prosthesis formed of a knit according to the invention, he can easily roll the knit up on itself, for example by folding the face provided with barbs outwards. It is then possible to introduce the knit according to the invention, thus rolled up, into a trocar, for example having an internal diameter of 10 mm. Once the knit according to the invention has been thus conveyed in the form of a roll to the implantation site via the trocar, it can be unrolled and deployed easily: indeed, even if some of the barbs were trapped within some of the openings present on the second face of the knit during the rolling up of the knit according to the invention and during its passage in the trocar, the particular structure of the knit according to the invention obtained by means of the particular chart followed during the knitting of the knit according to the invention means that these trapped barbs can be released very easily by exerting a minimal force for unrolling the knit. Thus, even if the barbs were entangled when the prosthesis was rolled up, they can be easily disentangled, and the surgeon can deploy the knit and/or the prosthesis easily in order to position it correctly on the implantation site. 
     The knit can then be fastened either to another fabric, or to a biological wall, owing to the anchoring abilities of the barbs. 
     In one embodiment of the invention, the first yarn or yarns are monofilament yarns. The first yarn or yarns of the knit according to the invention are those that follow the charts of bars B1 and B2. They constitute the ground structure or alternatively the base of the knit according to the invention, since the second yarn, namely a heat-fusible monofilament yarn, so as to generate the barbs, is regularly cut at the loops that it forms. The generation of barbs from loops made of heat-fusible yarn is known and is described, for example in document WO 01/81667. When the first yarn or yarns are monofilament yarns, the possible presence of protrusions or anchorage points of the barbs is limited and the force needed to unroll the knit after the rolling up as described above is very small. 
     The first yarns of the knit according to the invention may be made of any biodegradable or non-biodegradable biocompatible material. Thus, the biodegradable materials suitable for the first yarns of the knit of the present invention may be selected from polylactic acid (PLA), polyglycolic acid (PGA), oxidized cellulose, polycaprolactone (PCL), polydioxanone (PDO), trimethylene carbonate (TMC), polyvinyl alcohol (PVA), polyhydroxyalkanoates (PHAs), copolymers thereof and mixtures thereof. The non-biodegradable materials suitable for the first yarns of the knit of the present invention may be selected from polyethylene terephthalate (PET), polyamides, aramids, expanded polytetrafluoroethylene, polyurethane, polyvinylidene difluoride (PVDF), butyl ester polymers, polyetheretherketone (PEEK), polyolefins (such as polyethylene or polypropylene), polyethers, copper alloys, silver or platinum alloys, medical grades of steel such as medical-grade stainless steel, and combinations thereof. 
     In one embodiment of the invention, the first yarns are monofilament yarns made of polyester terephthalate (PET) having a diameter of 0.09 mm. Such yarns have an intrinsic stiffness meaning that when these yarns follow the particular charts of bars B1 and B2 of the knit according to the present invention, the knit obtained naturally tends to return to a flat configuration when it is unrolled under the effect of a stress as described above. 
     The second heat-fusible monofilament yarn may be made of a bioresorbable or non-bioresorbable material. For example, the heat-fusible monofilament yarn is made of a material selected from polypropylene, polyglycolic acid, polylactic acid, and mixtures thereof. In one embodiment, the heat-fusible monofilament yarn is a polylactic acid monofilament yarn having a diameter of 0.15 mm: such a yarn having such a diameter makes it possible to obtain barbs that have good anchoring abilities in biological tissues or in another openwork textile, while maintaining the ability of the knit according to the invention to be unrolled easily. 
     Another aspect of the invention is a process for manufacturing a prosthetic knit as described above, comprising the following steps: 
     i) knitting, on a warp knitting machine, of biocompatible yarns distributed over three guide bars, according to the following chart, according to the ISO 11676 standard:
         Bar B1: 1.0/0.1//   Bar B2: 1.0/7.7/6.6/7.7//   Bar B3: 2.1/5.5/3.4/0.0//       

     the yarn threaded on bar B3 being a heat-fusible monofilament yarn that generates loops that protrude outwards with respect to said first face, 
     ii) cutting, by melting, of each loop, each loop thus generating two barbs. 
     In the process according to the invention the yarns threaded on bar B1 and bar B2 are the first yarns made of biocompatible polymer material: these yarns may be identical or different. Thus, as seen above, these yarns may be monofilament yarns, in particular monofilament yarns made of polyester terephthalate (PET) having a diameter of 0.09 mm. 
     In one embodiment of the invention, the yarns are threaded one full, one empty on bars B1 and B2, and one full, three empty on bar B3. 
     Another aspect of the invention is a knit capable of being obtained according to the above process. 
     Another aspect of the invention is a prosthesis for repairing a hernia, comprising a knit as described above or obtained according to the process described above. 
     The knit according to the invention and/or the prosthesis according to the invention may be used in a method for treating a hernia, in particular the abdominal wall. The knit and the prosthesis according to the invention are particularly suitable for coelioscopic or laparoscopic surgery. 
    
    
     
       The advantages of the present invention are illustrated by means of the experimental section which follows and the following supporting figures: 
         FIGS. 1A to 1C : are diagrams showing the charts followed for the knitting of the yarns of the knits according to the invention, 
         FIG. 2 : is a diagram showing a chart followed for the knitting of the yarns of a knit from the prior art, 
         FIG. 3 : is a diagram illustrating the method for rolling up a knit, 
         FIGS. 4A and 4B : are diagrams illustrating the test for evaluating the force for unrolling a rolled-up knit, 
         FIG. 5 : shows the curve representing the force applied, in N, as a function of the extension, in mm, of a knit during the unrolling thereof. 
     
    
    
     EXAMPLE 1 
     Produced on a warp knitting machine having three guide bars B1, B2 and B3, were a knit A, according to the invention, and a comparative knit B, the chart of which differs from that of the knit according to the invention. 
     Knit A: according to the invention, having the following chart according to the ISO 11676 standard:
         Bar B1: 1.0/0.1//   Bar B2: 1.0/7.7/6.6/7.7//   Bar B3: 2.1/5.5/3.4/0.0//       

     These charts are illustrated in  FIGS. 1A to 1C  according to a representation known to a person skilled in the art: the chart of bar B1 is illustrated in  FIG. 1A ; the chart of bar B2 is illustrated in  FIG. 1B  and the chart of bar B3 is illustrated in  FIG. 1C . 
     Bar B1 and bar B2 are each threaded 1 full, 1 empty, with a monofilament yarn made of polyester terephthalate (PET) having a diameter of 0.09 mm; bar B3, which gives rise to the barbs, is threaded 1 full, 3 empty, with a heat-fusible monofilament yarn made of polylactic acid having a diameter of 0.15 mm. 
     Knit B: comparative, having the following chart according to the ISO 11676 standard:
         Bar B1: 1.0/0.1//   Bar B2: 1.0.0/5.5/1.0/3.3//   Bar B3: 2.1/5.5/3.4/0.0//       

     The chart of bar B2 is illustrated in  FIG. 2 . 
     Bar B1 and bar B2 are each threaded 1 full, 1 empty, with a monofilament yarn made of polyester terephthalate (PET) having a diameter of 0.08 mm; bar B3, which gives rise to the barbs, is threaded 1 full, 3 empty, with a heat-fusible monofilament yarn made of polylactic acid having a diameter of 0.15 mm. 
     For each of the two knits A and B, bar B3 is the one that leads to the formation of the barbs. Since the bars B3 are threaded in an identical manner for the two knits, and these bars have the same chart, the density of the barbs, once the loops have been melted, is the same for both knits. 
     Once the loops have been melted and the barbs have been formed as described in WO 01/81667, the unrolling properties were evaluated after rolling these knits up on themselves, according to the following test:
         for each knit, samples of 5 cm×10 cm were cut,   as shown in  FIG. 3 , each sample  1  of knit is rolled up on itself around a rod  3  having a diameter of 5 mm, the barbs  2  on the outside, along the direction of the arrow represented in  FIG. 3 . The roll obtained is then grasped with tweezers and inserted into a trocar having an internal diameter of 10 mm, then pushed until it comes out of the trocar.       

     On exiting the trocar, as shown in  FIG. 4A , the sample  1  in the form of a roll is mounted on a machine  4  equipped with a cell loaded to 25 N, comprising a fixed part  5  and a moving part  6 . Around 2 cm of the sample  1  is unrolled and 1 cm of the sample  1  is fastened to the moving part  6 . A constant extension rate of 50 mm/min is then applied to the sample  1  tested in order to unroll it, and the corresponding force F needed to maintain said constant extension rate is measured. The force F needed is recorded as a function of the length L of the unrolled portion of the sample  1  until sample  1  is completely unrolled, as shown in  FIG. 4B . During the unrolling of the sample  1 , the force force F needed may vary as a function of the resistance encountered. In particular, points of resistance, for which the force F for successfully unrolling the sample  1  must be increased, at least occasionally, may appear during the unrolling. 
     These “points of resistance” are measured as follows: using measured values of the force F and length L of the unrolled portion as indicated above, the curve representing the force F, in newtons, is plotted as a function of the length L of the unrolled portion in mm, of the sample  1 . Next, a threshold value is determined for the force F, for example 0.5 N. Each peak of the curve having a value greater than 0.5 N is considered to be a point of resistance. An example of such a curve, showing the peaks counted encircled, is represented in  FIG. 5 . By virtue of this curve, the maximum force needed, Fmax, is also determined. 
     The results obtained for knit A according to the invention and comparative knit B are presented in Table I below: 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE I 
               
               
                   
               
               
                   
                   
                 Number of 
                   
                   
               
               
                   
                 Number of 
                 “points of 
                 Average 
                 Maximum 
               
               
                 Sample 
                 tests 
                 resistance” 
                 force (N) 
                 force (N) 
               
               
                   
               
             
            
               
                 Knit A 
                 16 
                 52 ± 11 
                 1.13 ± 0.33 
                 3.54 ± 0.85 
               
               
                 Knit B 
                 20 
                 79 ± 8  
                 4.01 ± 0.80 
                 9.56 ± 1.68 
               
               
                   
               
            
           
         
       
     
     As it emerges from this table, the knit according to the invention (Knit A) has significantly fewer points of resistance than the knit from the prior art (Knit B). The average force needed to unroll the knit of the invention, after it has been rolled up on itself then passed through a trocar having an internal diameter of 10 mm is substantially lower than that needed to unroll the knit from the prior art. Likewise, the maximum force needed to unroll knit A according to the invention is practically divided by 3 compared to the maximum force needed in the case of the comparative knit B. 
     Thus, the knit according to the invention can be unrolled easily after having been rolled up on itself then passed through a trocar having a diameter of 10 mm. The knit can thus be brought to an implantation site during laparoscopic or coelioscopic surgery for repairing a hernia, by means of a trocar, then it can be unrolled without the surgeon having to apply considerable force in order to deploy the knit and/or the prosthesis comprising said knit.