Patent Description:
Implantable repair fabrics are employed by surgeons for soft tissue repair and reconstruction, including the repair of anatomical defects such as soft tissue and muscle wall defects. The fabric is typically sutured, stapled, tacked, or otherwise provisionally anchored in place over, under or within the defect. Tissue integration with the fabric, such as tissue ingrowth into and/or along the mesh fabric, eventually completes the repair.

Soft tissue and muscle wall defect repairs may be accomplished using various surgical techniques, including open, laparoscopic and hybrid (e.g., Kugel procedure) techniques. During open procedures, a repair fabric is placed through a relatively large incision made in the abdominal wall and layers of tissue and then the defect is filled or covered with the repair fabric. During laparoscopic and hybrid procedures, the fabric may be collapsed, such as by rolling or folding, into a reduced configuration for entry into a subject, either directly through a comparatively smaller incision or through a slender laparoscopic cannula that is placed through the incision.

Various repair fabrics are known and used for repairing soft tissue and muscle wall defects. BARD MESH and VISILEX, available from C. R Bard, and the repair fabric described in <CIT> or <CIT> are examples of implantable fabrics that have been successfully used in soft tissue and muscle wall repair. Such fabrics are fabricated from polypropylene monofilaments that are knitted into meshes having pores or interstices that promote tissue ingrowth and integration with the fabric.

Scar tissue may form about a repair fabric into a scar plate as tissue ingrowth occurs. The volume and rigidity of the scar plate that forms about the fabric may be affected by various factors, including the amount of foreign material introduced into a patient by the fabric.

It is an object of the disclosure to provide a prosthetic repair fabric for repair of soft tissue and muscle wall defects.

According to the invention, an implantable prosthetic repair fabric comprises a knit mesh that includes a plurality of generally polygonal shaped primary pores defined by knitted strands of first filaments having a first diameter; and a pair of individual second filaments that extend across each primary pore to define a plurality of secondary pores within each primary pore, each of the pair of individual second filaments extending substantially parallel to one another, each of the second filaments having a second diameter which is greater than the first diameter.

In one illustrative embodiment, the implantable prosthetic repair fabric according to claim <NUM> comprises a biologically compatible, implantable dual bar warp knit mesh produced according to a first bar pattern chain of <NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM> and a second bar pattern chain of <NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM>. The mesh has a ball burst strength of <NUM> to <NUM> (<NUM> lbs to <NUM> lbs), a suture pullout strength of <NUM> to <NUM> (<NUM> lbs to <NUM> lbs) in the machine direction and <NUM> to <NUM> (<NUM> lbs to <NUM> lbs) in the cross direction, and a tensile strength of <NUM> to <NUM> (<NUM> lbs to <NUM> lbs) in the machine direction and <NUM> to <NUM> (<NUM> lbs to <NUM> lbs) in the cross direction.

Various embodiments of the disclosure will now be described, by way of example, with reference to the accompanying drawings, in which:.

Embodiments of the present disclosure include a prosthetic fabric comprising a mesh fabric that is relatively flexible, thin and light weight and meets the performance and physical characteristics for soft tissue repair and reconstruction procedures. The surgical repair fabric may be used for reinforcing and closing soft tissue defects, and is particularly indicated for chest wall reconstruction and/or the repair of hernias, such as inguinal hernias. The mesh fabric is formed of a biologically compatible, flexible and strong implantable material.

The mesh fabric may employ a knit construction that provides relatively large openings or pores to ensure good visibility of the underlying anatomy without sacrificing mechanical properties of the mesh. The porous character of the fabric allows tissue infiltration to incorporate the prosthetic. The knitted fabric is sufficiently strong and structured to prevent or minimize potential pullout of anchoring fasteners, such as sutures, staples, tacks, and the like. The flexible repair fabric may promote an easy reduction in size for entry into the subject. In this manner, the flexible fabric may be collapsed into a slender configuration, such as a roll, which can be supported in, and advanced through, a narrow laparoscopic cannula for use in laparoscopic procedures.

The mesh fabric employs a relatively lighter weight, thinner, and/or more flexible fabric construction that may introduce less foreign body material into a patient as compared to other repair fabrics. The porous prosthetic repair fabric allows a prompt fibroblastic response through the interstices of the mesh, forming a secure fibrous/prosthetic layer. The fabric may promote a thinner and more compliant scar plate that may result in a relatively more comfortable soft tissue or muscle wall repair for a patient.

In one illustrative embodiment shown in <FIG>, the repair fabric comprises a knit mesh <NUM> including knitted strands of filaments <NUM> that define larger, primary pores <NUM> arranged in a uniform pattern. A pair of individual filaments <NUM> extend across the primary pores to define a plurality of smaller, secondary pores <NUM> therein.

In the illustrated embodiment, the primary pores <NUM> are bounded by knitted strands of filaments <NUM>. However, it is to be appreciated that one of more boundaries of the primary pores <NUM> may be defined by individual filaments as would be apparent to one of skill in the art. As shown, the primary pores <NUM> may have a generally polygon shape, such as hexagon, diamond or square shaped, although aspects of the disclosure are not limited. In this regard, it is to be understood that other pore shapes are also contemplated, including, but not limited to, circular, non-circular, round, oval and the like, as would be apparent to one of skill in the art.

The prosthetic repair fabric may be constructed to increase flexibility and/or reduce the overall weight per unit area of the fabric. Such properties may facilitate an easier collapse of the repair fabric for introduction into a patient. These properties may also provide for easier manipulation of the repair fabric about the surgical site within the patient. In one illustrative embodiment, the primary pores <NUM> have an area of approximately <NUM> to <NUM><NUM> (<NUM> to <NUM> square inches). In this regard, less material may be used to produce a given area of mesh, which may result in a reduced weight mesh. Additionally, the generally greater spacing between the strands of filaments <NUM> that are associated with the larger primary pores <NUM> may also contribute to a more flexible mesh. It is to be appreciated, however, that the size of the primary pores may vary as would be apparent to one of skill in the art, as aspects of the disclosure are not limited in this respect.

For some applications, it may be desirable to provide secondary pores <NUM> within the primary pores <NUM>. In one illustrative embodiment shown in <FIG>, each primary pore <NUM> is subdivided into a plurality of secondary pores <NUM> by a pair of individual or single filaments <NUM>. In the illustrative embodiment, the pair of filaments <NUM> divides the primary pore <NUM> into a pair of generally triangular secondary <NUM> pores and a generally rectangular secondary pore <NUM> that is positioned between the two generally triangular secondary pores <NUM>. It is to be appreciated, however, that the shapes of secondary pores and/or numbers of secondary pores within each primary pore, if desired, may vary as would be apparent to one of skill in the art, as aspects of the disclosure are not limited in this respect.

In one illustrative embodiment as shown in <FIG>, the pair of individual filaments <NUM> extend substantially parallel to one another across the primary pores <NUM>. As illustrated, the pair of parallel filaments <NUM> may be generally in linear alignment with corresponding pairs of filaments in adjacent primary pores. However, it is to be understood that the individual filaments may be positioned and oriented in other suitable arrangement within the scope of the claims.

The prosthetic repair fabric may be constructed so as to be provisionally anchored to tissue or muscle using a wide variety of fasteners, such as sutures, staples, spiral tacks, Q-rings and the like. The individual filaments <NUM> that extend across the primary pores may provide additional features for engaging the fasteners used to anchor the fabric. It is to be appreciated that repair fabrics may be anchored to tissue and/or mesh with fasteners, such as spiral tacks and Q-ring constructs, that have relatively small features for engaging and holding the repair fabric in place. The smaller, secondary pores <NUM> associated with the individual filaments may provide for improved engagement with the fasteners in a manner that is sufficiently strong and structured to prevent or minimize pullout. It is to be appreciated that the size of the secondary pores may vary as would be apparent to one of skill in the art, as aspects of the disclosure are not limited in this respect.

In one illustrative embodiment, the mesh fabric includes first filaments <NUM> having a first diameter to form the primary pores and second filaments <NUM> having a second diameter that is different from the first diameter extending across the primary pores. The second filaments <NUM> have a second diameter that is greater than the first diameter of the first filaments. Such an arrangement enhances the handling of the mesh fabric by increasing its stiffness.

In one illustrative embodiment, the knit mesh <NUM> may be produced in a lapping pattern by using two partially threaded guide bars to knit the pattern over three needles in a six course repeat. The fabric structure may be of an atlas type where each knitted end travels more than two needles, which may prevent unraveling of the mesh.

In one illustrative embodiment shown in <FIG>, the repair fabric may employ a dual bar warp knit mesh structure produced using two guide bars moving according to a first bar pattern chain of <NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM> (identified as reference <NUM>) and a second bar pattern chain of <NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM><NUM>/<NUM> (identified as reference <NUM>). The mesh may be knitted on a single needle bar, <NUM> gauge Rachelle knitting machine. The mesh may be fabricated with approximately <NUM> to <NUM> courses per <NUM> (<NUM> to <NUM> courses per inch) and approximately <NUM> to <NUM> wales per <NUM> (<NUM> to <NUM> wales per inch). It is to be appreciated, however, that the mesh fabric may be knitted using any suitable knit pattern as would be apparent to one of skill in the art, as aspects of the disclosure are not limited in this respect.

The knit mesh may be produced at various widths apparent to one of skill in the art, such as from <NUM> inch to <NUM> inches, depending on the intended application for which the repair fabric is being produced.

Following knitting, the fabric may be washed to remove foreign matter, such as residual processing lubricant. A cleaning agent, such as Triton X-<NUM>, may be used to aid in the removal of such foreign matter. Following washing, the mesh may be dried at a temperature lower than the heat set and melt temperatures of the material, as would be apparent to one of skill in the art.

Embodiments of the knit mesh may be heat set to impart a shape memory to the mesh and the prosthetic fabric formed of the mesh. In one illustrative embodiment, the fabric is heat set to have a generally planar shape memory. In this manner, after the fabric is collapsed and inserted into a patient, the fabric may revert back to the planar configuration for appropriate placement against tissue of the patient. It is to be appreciated that other embodiments of the fabric may be provided with a shape memory that corresponds to configurations different than planar, or to have no shape memory at all, as aspects of the disclosure are not limited in this regard.

If desired, the knit mesh may be heat set under tension, in a crochet hoop or tentering frame. The heat set may be applied while the mesh knit is being stretched in a particular direction to help set the mesh into a particular configuration. In one illustrative embodiment, the knit mesh is stretched in the cross machine knit direction and simultaneously allowed to partially relax or contract in the machine direction to a fixed point while heat is applied to set the mesh. It is to be understood, however, that other techniques apparent to one of skill in the art may be used to heat set the knit mesh, as aspects of the disclosure are not limited in this respect.

For some applications, it may be desirable to smooth the knitted mesh to reduce the texture or surface roughness of the mesh. In one illustrative embodiment, the knitted mesh is lightly pressed between a pair of plates which includes a heated plate that is pressed against the rough surface of the mesh to reduce high spots of the mesh and to heat set it to smooth its surface. It is to be appreciated, however, that the fabric may be smoothed using any suitable process apparent to one of skill in the art. For example, the fabric may be smoothed by passing the knitted mesh between a pair of heated rollers during the washing and drying process.

The filaments that are used to fabricate the repair fabric may contribute to the resulting mechanical properties of the fabric. In one illustrative embodiment, the repair fabric is knitted with first filaments <NUM> having a diameter of approximately <NUM> to <NUM> (<NUM> to <NUM> inches) (first bar pattern chain), and preferably a diameter of approximately <NUM> (<NUM> inches), and second filaments <NUM> having a diameter of approximately <NUM> to <NUM> (<NUM> to <NUM> inches) (second bar pattern chain), and preferably a diameter of approximately <NUM> (<NUM> inches). Filaments of these diameters may contribute to an enhanced handling and increased strength properties of the overall repair fabric.

In one illustrative embodiment, the fabric has a thickness of approximately <NUM> to <NUM> (<NUM> to <NUM> inches), and preferably a thickness of approximately <NUM> to <NUM> (<NUM> to <NUM> inches). In one illustrative embodiment, the fabric has a weight per unit area of approximately <NUM> to <NUM> grams/cm<NUM> (<NUM> to <NUM> grams per square inch). It is to be appreciated, however, that the fabric may be fabricated to have any thickness and/or weight per unit area apparent to one of skill in the art that is suitable for a desired application, as aspects of the disclosure are not limited in this respect.

In one illustrative embodiment, the filaments used to fabricate the mesh fabric comprise a polypropylene monofilament, which is inert in the presence of infection, is non-wettable and has a low foreign body reaction. In one illustrative embodiment, the monofilaments are formed of Aran Biomedical ProTex Med Polypropylene resin PPS50156 and PPS50157. In one embodiment, the first monofilament has a denier of approximately <NUM>±<NUM> (<NUM>±<NUM> tex) and the second monofilament has a denier of approximately <NUM>±<NUM> (<NUM>±<NUM> tex). In one embodiment, the first and second monofilaments have a tenacity of approximately <NUM> to <NUM> decitex (<NUM> to <NUM> grams/denier), with a nominal tenacity of approximately <NUM> decitex (<NUM> grams/denier). It is to be appreciated, however, that filaments of different configurations, properties and/or materials may be employed to fabricate the fabric. For example, the filaments may comprise multifilaments or monofilaments having different mechanical characteristics as would be apparent to one of skill in the art, within the scope of the claims.

The following examples are illustrative only and are not intended to limit the scope of the present disclosure.

Physical properties of a representative two bar warp knit mesh fabric produced from <NUM> (<NUM> inch) (first bar) and <NUM> (<NUM> inch) (second bar) polypropylene monofilament according to the illustrative embodiment shown in <FIG> and <FIG> (labeled Embodiment #<NUM> in Table <NUM>) were evaluated and compared to several known mesh fabrics (comparative mesh fabrics). Physical and performance characteristics were tested including mesh thickness, pore size, mesh weight per unit area, suture pull out strength, burst strength, tear resistance, tensile (break) strength and elongation at break, and stiffness. Testing methodology and results appear below in Table <NUM>, where mean results and ranges are reported from several test samples (ranges appear in parentheses).

Suture Pullout Strength: A sample of mesh measuring at least <NUM> x <NUM> (<NUM> inch x <NUM> inch) (Embodiment #<NUM>) or at least <NUM> x <NUM> (<NUM> inch x <NUM> inches) (comparative mesh fabrics) was prepared and clamped in the lower jaw of an MTS™ or equivalent tensile test machine. The long dimension of the sample should be parallel with its orientation designation (machine or cross-machine). At least <NUM> (<NUM> inch) (Embodiment #<NUM>) or at least <NUM> (<NUM> inch) (comparative mesh fabrics) of the mesh was exposed above the jaw. A spring steel wire with a diameter of approximately <NUM> (<NUM> inches) was placed through the mesh to simulate a suture. The wire was placed <NUM>±<NUM> from the edge of the mesh. The wire suture was looped back and both ends were attached to the upper jaw of the tensile machine. The suture was then pulled at a rate of <NUM> (<NUM> inches) per minute through the mesh. The peak force was recorded for <NUM> to <NUM> samples tested in both the machine and cross directions of the mesh and the average force was calculated for at least <NUM> total measurements in each direction.

Pore Size: A sample of mesh was placed on an optical coordinate measurement device such as a Tesa Vision (35x) or equivalent.

For embodiment#<NUM>, each primary pore has a generally hexagon shape which contains two generally triangular pores and a generally rectangular pore in the middle section. The length L of each leg of the primary pore was measured dimensionally between each pair of end points A-B, B-C, C-D, D-E, E-F and F-A, as illustrated by dashed lines in <FIG>. The pore area of the primary pore was calculated based on the area of a hexagon as follows, where Laverage is the average length of each leg: <MAT> Three randomly selected primary cells (not counting the pores formed by the loops or knots) of each of four mesh samples were measured and a combined average was calculated.

Tensile (Break) Strength and Elongation at Break: A mesh sample measuring approximately <NUM> x <NUM> (<NUM> inch x <NUM> inches) was placed into the pneumatic jaws of an MTS™ tensile tester or equivalent device. The sample was oriented so that the knit direction being tested was parallel to the <NUM> (<NUM> inch) length. The ends of the <NUM> (<NUM> inch) sample were gripped in the lower and upper jaws of the tester. Starting with a minimum separation of <NUM> (<NUM> inches), the sample was pulled at a constant rate of <NUM> (<NUM> inches) per minute until the sample broke. The peak load and elongation at break were recorded. The samples were tested in both the cross direction and the machine direction. The averages of at least <NUM> total measurements taken from <NUM> to <NUM> samples were then calculated for each direction.

Mesh Thickness: A sample of mesh was measured using a standard thickness snap gage with an approximate <NUM> (<NUM> inch) diameter pressure foot that is lightly spring loaded. The thickness was measured by lowering the foot onto the mesh. Measurements were taken to the nearest <NUM> (<NUM> inch). At least five sheets of mesh were measured in total and a combined average was calculated.

Mesh Weight/Unit Area: Using a sample size of at least four pieces of mesh that measured at least approximately <NUM> x <NUM> (<NUM> inches x <NUM> inches), the weight of each sample was measured in grams to the nearest <NUM> gram. The area was calculated by measuring the length and width dimensions taken to the nearest <NUM> (<NUM> inch), minus the area of any radiused corner. The weight per unit area was calculated for each sample using the weight and unit area. The average weight per unit area was calculated by combining and averaging the weight per unit area for each sample.

Burst Strength: This test method was derived from the ANSI/AAMI VP20-<NUM> Section <NUM>. <NUM> and ASTM Ball Burst method D3787-<NUM>. A mesh sample was placed on top of a circular O-ring measuring approximately <NUM> (<NUM> inch) in diameter. The O-ring was seated in a grooved plate in a fixture with a hole in the middle of plate containing the O-ring. The fixture was attached to the lower jaw in an MTS™ or equivalent test machine. The plate with the mesh was raised and clamped against an upper plate in the fixture, compressing the mesh sample. The upper plate also contained a hole with the same diameter as the lower plate. The holes in the fixture plates are dimensioned to be just slightly larger than and to accept a rounded ball tipped rod that has a <NUM> (<NUM> inch) diameter tip. The rod was connected to an upper jaw of the test machine that was moved down through the sample at a constant rate of <NUM> (<NUM> inches) per minute. The peak load was recorded for at least <NUM> samples. The average burst strength was then calculated based on the peak loads for the samples.

Tear Resistance: A mesh sample measuring approximately <NUM> x <NUM> (<NUM> inches x <NUM> inches) was prepared. A <NUM> (<NUM> inch) slit was cut in one side (the direction to be tested) at the midpoint to form two mesh sections. One section of mesh was clamped in the lower jaw of a pneumatic fixture and the other was clamped in the top jaw of the fixture. Starting with the jaws at a minimum spacing of <NUM> (<NUM> inch), the mesh was pulled at a rate of <NUM> (<NUM> inches) per minute until the tear was completed. The peak force was recorded. Samples were tested in the cross direction and the machine direction (Embodiment #<NUM>), and the cross direction, the machine direction, and the diagonal direction (comparative mesh fabrics). The averages of at least <NUM> total measurements taken from <NUM> to <NUM> samples were then calculated for each group direction.

Claim 1:
An implantable prosthetic repair fabric, comprising:
a knit mesh (<NUM>) that includes a plurality of generally polygonal shaped primary pores (<NUM>) defined by knitted strands of first filaments (<NUM>) having a first diameter; and
a pair of individual second filaments (<NUM>) that extend across each primary pore (<NUM>) to define a plurality of secondary pores (<NUM>) within each primary pore (<NUM>), each of the pair of individual second filaments (<NUM>) extending substantially parallel to one another, each of the second filaments (<NUM>) having a second diameter which is greater than the first diameter.