Surgical implant

Abstract

A surgical implant (20) comprises a flexible basic structure (22) having a face and a plurality of resorbable film pieces (26) attached to the face of the basic structure (22). Each film piece (26) comprises a plurality of solid protrusions (28) emerging from the respective film piece (26) is a direction away from the basic structure (22).

Claims

1. A process of manufacturing a surgical implant the implant comprising a flexible basic structure having a face and a plurality of resorbable film pieces attached to the face of the basic structure, wherein each film piece comprises a plurality of protrusions emerging from the respective film piece in a direction way from the basic structure, characterized by the steps of: providing a mold containing an array of cavities, each cavity having the shape of one protrusion, filling the mold with a fluid material forming the film pieces and the protrusions according to a pattern defining the shapes and locations of the film pieces, hardening the fluid material, attaching the film pieces to a basic structure, with the protrusions pointing away from the basic structure, and removing the mold; wherein the pattern defining the shapes and locations of the film pieces is determined by a mask placed between the basic structure and the material to be filled in the mold and the process further characterized by the steps of providing a layered assembly comprising, in this order: the mold, a surgical mesh as the basic structure, the mask, a sheet of material for the film pieces having a lower melting point than the surgical mesh, a flexible plate device, heating the sheet of material to a temperature higher than its melting point and lower than the melting point of the surgical mesh, pressing the mold and the plate device towards each other, whereby the material for the film pieces is transferred through the mask into the mold and embeds the surgical mesh, and lowering the temperature and removing the mold.

2. The process according to claim 1, characterized in that the mold is flexible and comprises at least one of the following materials: flexible material, silicone, polyurethane, natural rubbers, synthetic rubbers.

3. The process according to claim 1, characterized in that the flexible plate device has one of the following properties: comprising a closed surface being designed as a second mold, which is flexible and contains an array of cavities, each cavity having the shape of one protrusion.

Description

(1) In the following, the invention is further explained by means of embodiments. The drawings show in.

(2) FIG. 1 in part (a) a three-dimensional view of an embodiment of the surgical implant according to the invention and in part (b) an enlarged view of a film piece comprising protrusions of this embodiment,

(3) FIG. 2 a three-dimensional view of a variant of the embodiment of FIG. 1,

(4) FIG. 3 another embodiment of the surgical implant according to the invention, i.e. in part (a) an enlarged three-dimensional view of a film piece including mushroom-shaped protrusions and in part (b) a plan view of part of the implant,

(5) FIG. 4 in parts (a) to (h) three-dimensional representations of several embodiments of protrusions for film pieces of surgical implants according to the invention,

(6) FIG. 5 another embodiment of the surgical implant according to the invention, i.e. in part (a) a plan view of part of the film piece pattern of the implant, in part (h) a magnified view of a film piece according to part (a) and in part (c) a three-dimensional view of the film piece of part (b),

(7) FIG. 6 another embodiment of the surgical implant according to the invention, i.e. in part (a) a plan view of part of the film piece pattern of the implant, in part (b) a magnified view of a film piece according to part (a) and in part (c) a three-dimensional view of the film piece of part (b),

(8) FIG. 7 a schematic illustration of an embodiment of a process of manufacturing a surgical implant according to the invention, see Example 1,

(9) FIG. 8 a diagram illustrating a geometric calculation related to the embodiment of the surgical implant according to the invention described in Example 1,

(10) FIG. 9 a top view of the embodiment of the surgical implant according to the invention described in Example 3,

(11) FIG. 10 a schematic illustration of another embodiment of a process of manufacturing a surgical implant according to the invention, see Example 4, and

(12) FIG. 11 a schematic illustration of another embodiment of a process of manufacturing a surgical implant according to the invention, see Example 7,

(13) FIG. 1 illustrates a surgical implant 1, which comprises a flexible basic structure designed as a surgical mesh 2 serving as a soft-tissue repair sheet. The face of the mesh 2 pointing upwards in the three-dimensional view of FIG. 1(a) is designated by 3. In the embodiment, the mesh 2 includes pores 4 of a hexagonal shape, which are arranged in a honeycomb pattern.

(14) A plurality of film pieces 6 is attached to face 3 of the mesh 4. In the embodiment, the film pieces 6 do not adhere to each other. Each film piece 6 carries a plurality of solid protrusions 8 emerging from the respective film piece 6 in a direction away from the mesh 2, as is best visible in the magnified view of FIG. 1(b). In the embodiment, the protrusions 8 are rod-like, the angle between the longitudinal axis of each protrusion 8 and the surface of the film piece 6 being about 90°. The film pieces 6 have a hexagonal shape as well, but the area of a film piece 6 is greater than that of a pore 8.

(15) A variant of the surgical implant 1 is shown in FIG. 2 and designated by 10. The surgical implant 10 is basically designed like surgical implant 1 so that for corresponding parts the same reference numerals are used as in FIG. 1. In addition to the implant 1, however, the implant 10 comprises a barrier sheet 12 attached to the opposite face 13 of mesh 2. The barrier sheet 12 is designed as a non-porous film and is to prevent ingrowth of bodily tissue via the opposite face 13 into mesh 2 after implantation of the surgical implant 10. In the embodiment, the barrier sheet 12 is larger than the mesh 2, which results in the presence of margins 14 around mesh 2. The margins 14 may assist the handling of implant 10.

(16) FIG. 3 shows another embodiment of the surgical implant, which is designated by 20 and can be manufactured as described in Example 1 further below FIG. 3(a) is a drawing according to a microscopic picture of a film piece carrying a plurality of protrusions, and FIG. 3(b) is a plan view of part of the implant 20, which, in the embodiment, extends beyond the limits indicated in FIG. 3(b).

(17) The implant 20 comprises a mesh-like basic structure 22 having rhombic pores 24. Its face carries a plurality of hexagonal film pieces 26. The area of each film piece 26 is somewhat larger than the area of one pore 24. A plurality of protrusions 28 emerges from the upper face of each film piece 26. The protrusions 28 are mushroom-like, each protrusion 28 including a stem 30 and a head 32 laterally projecting with respect to the stem 30.

(18) FIG. 3(a) shows that the fibers of the mesh. 22 are almost completely embedded in the material of the film pieces 26.

(19) In the embodiment, the mesh 22 is a commercial “Ultrapro” mesh of Ethicon, which is a lightweight, monofil, partially resorbable surgical mesh made of fibers of polypropylene (non-resorbable) and “Monocryl” (see above; resorbable) having a pore width of about 2.27 mm in one direction and a pore width of about 3.17 mm in a direction perpendicularly thereto. The film pieces 26 are hexagonal having a width in the range of about 3.7 mm to 4.1 mm. The distance between adjacent film pieces 26 is about 4.4 mm. The film pieces 26 cover about 20% of the area of the face of mesh 22. They extend over crossing points of the pores 24. The film pieces 26 including the protrusions 28 are made of poly-p-dioxanone (PDS), which is resorbable. For further details, see Example 1 below.

(20) FIG. 1, in parts (a) to (h), displays several types of solid protrusions, which are all designated by reference numeral 40. Most of the protrusions 40 comprise a stem 42 (some of them a stem with a pronounced foot section 43) and a head 44, which at least partially projects laterally with respect to the stem 42, see FIGS. 4 (a) to 4(e) and 4(g). Some protrusions include a spike 46 extending beyond the head 44, see FIGS. 4(c), 4(e) and 4(g). The protrusion according FIG. 4(f) is completely designed as a spike. FIG. 4(h) shows a protrusion shaped as a bent rod 48. A particularly advantageous form is like a mushroom, see FIG. 4(d).

(21) In detail in FIG. 4(a), the stem 42 and the head 44 are hexagonal, with the head. 44 symmetrically projecting laterally with respect to the stem 42. In FIG. 4(b), stem 42 and head 44 are hexagonal, while the head 44 is asymmetrically arranged with respect to the stem 42. In FIG. 4(c), the protrusion is similar to that of FIG. 4(b), but carries a trigonal pyramidal spike. The protrusion of FIG. 4(d) is mushroom-like and has a frusto-conical foot section 43, a tapered middle section of the stem 42 and a relatively flat head 44. In FIG. 4(e), the protrusion is similar to that of FIG. 4(d), but has an additional pyramidal spike. The protrusion of FIG. 4(f) comprises a circular base section 43 with a diameter decreasing down into a sharp tip or spike 46. FIG. 4(g) shows a mushroom-like protrusion similar to that of FIG. 4(e), wherein the head 44 includes some cuts. The protrusion of FIG. 4(h) is shaped as a bent rod 48 made of three straight sections angled with respect to each other; in a variant, it is smoothly bent along its entire length.

(22) FIG. 5 illustrates another embodiment of the surgical implant, which is designated by 50. In FIG. 5(a), the pattern of film pieces 56 is shown, which have a triangular shape each (see FIG. 5(b)) and comprise essentially cuboidal protrusions (see FIG. 5(c)). The arrangement of the film pieces 56 defines three lines intersecting at respective angles of 60°, which provides for an increased flexibility of the basic structure of the implant 50 in some directions.

(23) Surgical implant 60 shown in FIGS. 6(a) to 6(c) is similar to the implant 50. In this case, however, the distance between film pieces 66 is smaller than that between the film pieces 56, and the protrusions are shaped as longitudinally extending ledges 68.

(24) Some examples follow, which also relate to manufacturing processes of the implant.

Example 1

“UltraPro” Mesh with ˜30% in Area Hexagonal PDS Film Pieces with Micro-Protrusions

(25) FIG. 7 schematically illustrates an embodiment of a manufacturing process of a surgical implant, i.e. a process of manufacturing the implant 20 already described by means of FIG. 3.

(26) In a first step, a mold 70 containing an array of cavities 71, each cavity having the shape of one protrusion, was made from a 2-component silicone precursor kit (elastomeric kit). To this end, a positive form (master) of polypropylene comprising on one surface 288 mushroom-shaped protrusions/cm.sup.2 with a total height of approximately 250 μm, a head diameter of approximately 375 μm, a stem diameter of approximately 200 μm and a foot diameter of approximately 340 μm was used. The liquid silicone elastomer was cast over the polypropylene master and, while keeping a horizontal position, cured at elevated temperatures (50° C. to 80° C.) in an oven for several hours. After cooling to room temperature, the silicone mold, comprising mushroom-shaped negatives of the protrusions, could be removed from the polypropylene master.

(27) As basic structure of the implant, an “UltraPro” mesh (Ethicon) was used (surgical mesh 72 in FIG. 7), which is a composite mesh containing about equal parts of polypropylene fibers and resorbabable “Monocryl” (polyglecaprone) fibers. The mesh could be fixated in a metal frame form to prevent movement and shrinkage.

(28) The mold 70 was placed in a metal form with the cavities 71 facing up, followed by the surgical mesh 72. Next, a hexagonally perforated thin rubber layer (schematically shown as mask 74 in FIG. 7) was placed on top of the mesh 72, followed by a sheet 76 of a material having a lower melting point than the material of the mesh 72. In the example, the sheet was a film of poly-p-dioxanone (PDS) having a thickness of 150 μm. Finally, a plate device 78 (in the example, a soft closed-cell foam material) was placed on top of the sheet 76.

(29) This assembly was placed in a heat press and allowed to heat to a temperature slightly below 130° C. for several minutes under a pressure of about 5 bar. Under these conditions, the poly-p-dioxanone material of sheet 76 got very soft and penetrated the hexagonal openings in the mask 74 and the pores of mesh 72 and filled the cavities 71 in mold 70, thus forming hexagonal film pieces well attached to the mesh and including protrusions. After cooling down the assembly to ambient temperatures (or a temperature below 50° C.), the pressure could be released and the mold 70, the mask 74 and the plate device 78 taken away. Because of its high flexibility, the silicone mold 70 could be removed from the protrusions without problems.

(30) Multiple micro-protrusions were identified under a scanning electron microscope with a total height of about 290 μm, a head width of about 360 μm with a perimeter thickness of about 20 μm, and a stem diameter of about 150 μm to 200 μm.

(31) The resulting surgical implant was flexible and conformable like the basic mesh 72. No remarkable stiffness was introduced. A handling test on a pig stomach showed a good attachment to tissue, like fat or muscle, and at the same time no self-attaching properties compromising the handling during, e.g., rolling or folding.

(32) In detail: A surgical implant manufactured as described in Example 1 and having a size of 7 cm×9 cm exhibited in a bench top test on a pig stomach a good attachment to muscle or fatty tissue, after a slight pressing force had been exerted to the tissue for a short period of time. The shear force (determined with a spring scale) was about 1.1 N. The implant could be easily removed and placed again without losing much attachment force.

(33) The implant could also be easily rolled, passed through a trocar, unrolled in the abdominal cavity and placed against the abdominal wall according to a TAPP procedure. In TAPP the surgeon enters the peritoneal cavity and places a mesh through a peritoneal incision over possible hernia sites. The implant of Example 1 attached well to the tissue, could be easily handled and did not undesirably stick to the bowel during handling.

(34) The total area of all film pieces turned out to be about 30% of the area of the surface of the basic structure (mesh 72). Surprisingly, even such a relatively small total film piece area exhibited a good tissue attachment to muscle and fascia, see above, without negatively compromising the elasticity and flexibility of the implant in a handling test.

(35) The total film piece area was determined by a geometrical calculation, see FIG. 8, assuming the shape of an equilateral hexagon for each film piece and equal sizes for all film pieces a=r=2.065 mm was determined by means of a microscope. Using h=[(½)√3]a, the area A of one hexagon is
A=6(½)a[(½)√3]a=1.5 √3a.sup.2=11.08 mm.sup.2.

(36) A rectangular piece of the surgical implant of Example 1 having a size of 60 mm×110 mm contained 8*13=104 film pieces. Thus, the above ratio is 104*11.08/(60*110)=0.175 or 17.5%.

Example 2

“TiGr-Matrix” with ˜20% in Area Hexagonal PDS Film Pieces with Micro-Protrusions

(37) TiGr-Matrix® by Novus Scientific is a composite mesh made from long- and short-term multifilament absorbable fibers. Fast absorbing fibers consist of a copolymer of glycolide, lactide and trimethylene carbonate and are basically absorbed within 4 months. Long-term absorbing fibers are made from a copolymer of lactide and trimethylene carbonate and are completely absorbed within about 3 years.

(38) A surgical implant was prepared as described in Example 1, but using a 7 cm×11 cm piece of TiGr-Matrix® instead of the “UltraPro” mesh as basic structure. The film pieces were irregularly rounded and were firmly attached to the basic structure.

(39) The resulting implant was only slightly stiffer than the basic structure mesh during handling and could be easily rolled up and unrolled without major mesh-to-mesh self-attachment.

Example 3

Porous cPTFE Sheet Between Circular PDS Film Pieces Having Protrusions on One Side

(40) Omyra® mesh by B. Braun is a mesh-like film for hernia repair. It is made of a condensed polytetrafluoroethylene (cPTFE), where star-shaped pores of about 2, 4 mm are cut out to introduce mesh-like properties into the cPTFE film.

(41) Nine film pieces of PDS film (8 mm diameter, thickness about 150 μm) were placed on one face of a 7 cm×7 cm perforated cPTFE patch (Omyra® mesh), the spaces between the film pieces being about 1 cm, 9 similar film pieces were placed on the other face of the patch, just opposite the first film pieces. This assembly was arranged between the silicone mold from example 1 and one non-textured silicon pad from example 1. The whole assembly was placed between two metal plates in a heat press and heated, pressed for about 5 Minutes at about 120° C. and allowed to cool down in the press to ambient temperatures.

(42) In this way, protrusions were formed on the film pieces at one face of the cPTFE patch, whereas these film pieces were firmly fused with the counterpart film pieces at the opposite face of the patch, the patch sheet being embedded in-between. The counterpart film pieces were smooth. The protrusions were easily palpatable with a finger to find the correct face for positioning the implant. Overall characteristics regarding bending during handling were not altered. In the film areas, the cPTFE struts were embedded with about 60 μm PDS film on both sides (in the protrusion-free micro-regions). Total thickness of the PDS film with protrusions was about 560 μm, with mushroom-like micro-protrusions of about 250 μm height, 390 μm width at the heads and 190 μm at the stems. The total film piece area is calculated to be about 10% of the total sheet area.

(43) FIG. 9 shows the surgical implant (designated by 90) prepared in Example 3. It comprises the Omyra® mesh as basic structure 92, which includes reinforcement lines 94, and nine film pieces 96.

Example 4

Tight-Weight PP Mesh with Palpatable Film Pieces

(44) A light-weight polypropylene (PP) mesh having a comparable knitting structure as the UltraPro® mesh available from Ethicon, Inc., Somerville, N.J. U.S.A., used in Example 1, but without the absorbable Monocryl® filaments (polyglecaprone 25) was prepared. This mesh (basic structure) was heat-laminated similar to Example 1, but with a slightly different setup, see FIG. 10.

(45) From bottom to top, the layers are: a silicon mold 100 containing an array of cavities 101, each cavity having the shape of one protrusion, a sheet 106 of PDS for forming the film pieces including the protrusions, a rubber mask 104, the above PP mesh as basic structure 102, and a plan elastic plate device 108 of silicon (without cavities). In this case, protrusions are formed all over the mold 100 and the sheet 106, but the mask 104 shields part of the mesh 102 so that only film pieces (with protrusions) attach to the mesh.

(46) The protrusions of the film pieces were easily palpatable (even with gloves), which enables a side differentiation.

(47) The surgical implant prepared in Example 4 was tested in a rat skin friction model comparable to WO 2006/092236 A1, having a 500 g (5N) pre-load on the rat skin. The maximum friction force was about 13N for a 5 cm×10 cm contact area.

Example 5

Light-Weight PP Mesh with Palpatable Film Pieces on Both Faces

(48) In a first step, the surgical implant of Example 4 was prepared. Afterwards, the PP mesh including the film pieces (with protrusions) was placed between two silicon molds and laminated and cooled down again.

(49) This resulted in a surgical implant comprising a mesh-like basic structure having film pieces with protrusions on both faces. The implant was flexible and could be attached on both sides to tissue or fat structures.

Example 6

Porous cPTFE Sheet Between Rectangular PDS Film Pieces with Protrusions

(50) A 10 cm×10 cm perforated cPTFE patch (Omyra® mesh, B. Braun, as also used in Example 3) was placed together with five film pieces on each side, respective pairs opposing each other, of PDS film (thickness 150 μm, each one 1 cm×1 cm square; four pieces in the corners and one in the center of the patch) between two silicone molds prepared as in Example 1. This assembly was placed between two metal plates in a heat press and heated, pressed for about 5 Minutes at about 120° C. and allowed to cool down in the press to ambient temperatures.

(51) The resulting surgical implant comprised film pieces with protrusions on both faces of the cPTFE patch, the latter being well embedded in the PDS mass of the film pieces.

Example 7

Light-Weight PP Mesh with Film Pieces Having Protrusions on Both Sides

(52) As the basic structure, a light-weight polypropylene (PP) mesh as prepared in Example 4 was used.

(53) FIG. 11 schematically shows the set-up for manufacturing the surgical implant of Example 7. The layers in FIG. 11 are, from bottom to top: a silicon mold 110 containing an array of cavities 111, each cavity having the shape of one protrusion, a sheet 116 of PDS for forming the film pieces including protrusions, a rubber mask 114, the above PP mesh as basic structure 112, another rubber mask 115 and a second mold 118 containing an array of cavities, each cavity having the shape of one protrusion.

(54) In a heat lamination process similar to that of Example 4, the PDS material is pressed into the pores of mesh 112 and the cavities of both molds 110 and 118, whereas the masks 114 and 115 shield the mesh 112 at both sides and define clean borderlines of the film pieces. In this way, the film pieces formed comprise protrusions on both faces and are well attached to the mesh 112.

(55) The appearance of the film pieces was determined under the microscope: A flat film piece area showed a thickness of 240 μm to 290 μm in different areas of the film piece, top protrusions were about 290 μm high and bottom protrusions were about 320 μm high. The mushroom-like protrusions with a head width of about 360 μm and a smallest stem width of about 160 μm were not aligned between both faces. The protrusions were facing away from both mesh faces.

(56) The resulting surgical implant showed fixation properties on both sides to soft tissue like, fat, muscle, or fascia. The implant was not sticking to itself when tightly rolled up and then unrolled, which is important for laparoscopic surgery.