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Compressed high density fibrous polymers suitable for implant

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Compressed high density fibrous polymers suitable for implant

An embodiment of the present invention may be made by the following steps: providing a mixture comprising a plurality of fibers, a lubricant, and a suspension fluid, with the suspension fluid filling a void space between said fibers and subjecting said mixture to at least one compressive force. The compressive force causes the migration and alignment of said fibers; and may remove substantially all of the suspension fluid from said mixture. The mixture may further comprise a biologically active agent, or a reinforcing agent.

Inventors: Timothy A. Ringeisen, W. Christian Wattengel
USPTO Applicaton #: #20120277152 - Class: 514 88 (USPTO) - 11/01/12 - Class 514 

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The Patent Description & Claims data below is from USPTO Patent Application 20120277152, Compressed high density fibrous polymers suitable for implant.

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This application is a Divisional of U.S. patent application Ser. No. 10/729,146, filed on Dec. 4, 2003, entitled COMPRESSED HIGH DENSITY FIBROUS POLYMERS SUITABLE FOR IMPLANT, which issued on Mar. 13, 2012 as U.S. Pat. No. 8,133,500, which is assigned to the same assignee as this invention, and whose disclosure is incorporated by reference herein.


Despite the growing sophistication of medical technology, repairing and replacing damaged tissues remains a costly, and serious problem in health care. Currently, implantable prostheses for repairing tissues are made from a wide number of synthetic and natural materials. Ideally, these prosthetic material should be chemically inert, biocompatible, noncarcinogenic, capable of being secured at the desired site, suitably strong to resist mechanical stress, capable of being fabricated in large quantities in the form required, sterilizable, and free of viruses or other contaminating agents. Examples of tissue that can be treated with implantable prostheses include dura mater, tendon (e.g., rotator cuff, anterior cruciate, etc.) and rectic abdominus muscle due to herniation.

A wide variety of prosthetic materials have been used, including tantalum, stainless steel, Dacron, nylon, polypropylene (e.g., Marlex), microporous expanded-polytetrafluoroethylene (e.g., Gore-Tex), dacron reinforced silicone rubber (e.g., Silastic), polyglactin 910 (e.g., Vicryl), polyester (e.g., Mersilene), polyglycolic add (e.g., Dexon), and cross-linked bovine pericardium (e.g., Peri-Guard). To date, no single prosthetic material has gained universal acceptance.

Metallic meshes, for example, are generally inert and resistant to infection, but they are permanent, do not generally adapt in shape as a skeletal structure grows, and they shield the healing tissues from the stresses that may be necessary to generate fully functioning tissue. Non-resorbable synthetic meshes have the advantage of being easily molded and, except for nylon, retain their tensile strength in the body. Their major disadvantages are their lack of inertness to infection, the occasional interference with wound healing, and that they are often long-term implants. Absorbable meshes have the advantage of facilitating tissue in-growth and remodeling at the site of implantation, but often do not have the short-term or long-term mechanical strength necessary for the application.

Both U.S. Pat. No. 4,948,540, granted to Nigam and U.S. Pat. No. 5,206,028 granted to Li, disclose a collagen membrane suitable for medical uses. In the case of Li, the membrane is constructed in a fashion to make it easier for implantation, by ensuring the membrane is not transparent, and not slippery. Both patents begin by providing a solution of collagen, which is freeze-dried, cross-linked, and then compressed. Li then utilizes a second cross-linking, freeze-drying and compression step. The initial cross-linking step locks the fibers into a specific orientation. The compression step merely reduces the porosity within the sheet without inducing fiber migration that would substantially improve the strength of the composition. A second cross-linking step is necessary to hold the sheet in its compressed conformation. What is needed is a sheet with improved strength, capable of maintaining its structural competence without the need of multiple freeze-drying and cross-linking steps.

In U.S. Pat. No. 6,599,524 granted to Li, there is disclosed a membrane sheet having oriented biopolymeric fibers. The membrane is manufactured with oriented parallel fibers formed around a rotating mandrel. The rotations of the mandrel as the fibers are added results in the orientation of the fibers. The membrane is then compressed to drive out excess liquid, and cross-linked, resulting in a membrane with directionally oriented fibers. This material is only aligned in a single direction and must be laminated with binding agents in order to create a functional device. Additionally, such a device does not provide gradients such as those seen in natural tissues. What is needed is a method that allows for layering that occurs at the microscopic as well as the macroscopic level as part of a one step process and more closely represents the layered structure of natural connective tissues.

Prosthetic devices are used in the repair, augmentation, or replacement of articulating organs. For example, the rotator cuff (i.e., shoulder joint) is made up by a combination of the distal tendinous portion of four muscles: the supraspinatus, subspinatus, subscapularis and the teres minor. Proper functioning of this tendonous cuff, depends on the fundamental centering and stabilizing role of the humeral head with respect to sliding action during lifting and rotation movements of the arm. A tear in the rotator cuff tendons is a common injury that can be caused by constant friction from repetitive overhead motion, trauma, or age-related degeneration that can narrow the space between the clavicle and the top of the scapula.

To repair large tears of the rotator cuff, it is desirable to use a scaffold or graft material to help support the damaged tissue and guide its repair. Several types of materials have been used for such procedures. Wright Medical (Memphis, Tenn.) markets a product known as GraftJacket, which is manufactured by Lifecell Corporation (Branchburg, N.J.) from human cadaver skin. Human cadaverous tissue products can be difficult to obtain and have the potential for disease transmission. Tissue Sciences (Covington, Ga.) markets a product known as Permacol, which is comprised of cross-linked porcine dermis. DePuy (Warsaw, Ind.) markets the Restore Patch which is fabricated from porcine small intestine submucosa. Biomet (Warsaw, Ind.) markets a product known as CuffPatch another porcine small intestine product. The CuffPatch and the Restore Patch products provide biocompatible scaffolds for wound repair but they are complicated to manufacture, as they require the lamination of multiple layers of submucosal tissues to gain the strength needed for these applications. Fabrication of such patches from porcine small intestine submucosa are described in U.S. Pat. Nos. 4,902,508 Badylak et al. and 5,573,784 Badylak et al.

Additional applications for prosthetic devices exist in the form of membrane patches. The spinal cord and brain are covered with a protective membrane that is known as the dura mater. The integrity of the dura mater is critical to the normal operation of the central nervous system. When this integrity is intentionally or accidentally compromised (e.g., ruptured, severed, damaged, etc.), serious consequences may ensue, unless the membrane can be repaired. Typically, dura tissue is slow to heal. To enhance the healing process, graft materials can be utilized to guide the regeneration of the tissue. Repairing damaged membranes has largely focused on implantable materials known as dural substitutes, which are grafted over the damaged dura mater and are designed to replace and/or regenerate the damaged tissue.

Thus, there is a need for an effective dura substitute that would be biocompatible, sufficiently noninfectious (e.g., purified, etc.) to prevent the transmission of disease, conformable, available in a variety of sizes, high in tensile strength, inert, suturable, and optionally capable of forming a water-tight seal.

Researchers have experimented with a wide variety of substances to act as dura substitutes. Autologous grafts of tissue, such as pericardium, can be effective as a dura substitutes; however, autologous tissue is not always available and it posses additional costs and risks for the patient. Cadaverous dura mater has also been used but like autologous tissues, cadaverous tissues can be difficult to obtain. Tutogen Medical Inc. (West Paterson, N.J.) markets a product known as Tutoplast dura mater, which is obtained from human cadavers. Processed human cadaveric dura mater has been implicated in the transmission of cases of the fatal Creutzfeldt-Jakob disease. Other products overcome this shortcoming by using alternate materials. The Preclude Dura substitute, manufactured by W. L. Gore (Newark, Del.), is an inert elastomeric fluoropolymer material. The material is biocompatible but is a permanent implant and does not resorb over time. Dural substitutes comprising collagen have been also been explored as described in U.S. Pat. No. 5,997,895 (Narotam et al.). Integra Lifesciences Corporations (Plainsboro, N.J.) distributes a product known as DuraGen. The product is manufactured from bovine achilles tendon and is a pliable porous sheet. Although the material is resorbable and biocompatible, the integrity of the material is not sufficient enough to withstand suturing to the wound site.

The present invention overcomes these suturing and other difficulties of the materials currently available and provides a structure capable of being adapted to a wide variety of surgical applications.

Other applications for the implantable prosthesis of this invention, in the form of a surgical mesh, include pelvic floor disorders such uterine and vaginal vault prolapse. These disorders typically result from weakness or damage to normal pelvic support systems. The most common etiologies include childbearing, removal of the uterus, connective tissue defects, prolonged heavy physical labor and postmenopausal atrophy. Many patients suffering from vaginal vault prolapse also require a surgical procedure to correct stress urinary incontinence that is either symptomatic or latent.

Another embodiment of the present invention is directed to devices useful as prosthetic menisci, and in vivo or ex vivo scaffolds for regeneration of meniscal tissue.

The medial and lateral menisci are a pair of cartilaginous structures in the knee joint which together act as a stabilizer, a force distributor, and a lubricant in the area of contact between the tibia and femur. Damaged or degraded menisci can cause stress concentrations in the knee thereby creating abnormal joint mechanics and leading to premature development of arthritic changes.

In the prior art, treatment of injured or diseased menisci has generally been both by surgical repair and by tissue removal (i.e., excision). With excision, regeneration of meniscal tissue may not always occur. Allografting or meniscal transplantation is another method of replacement, which has been previously tried.

This approach has been only partially successful over the long term due to the host\'s immunologic response to the graft and to failures in cryopreservation and other processes. Alternately, menisci have been replaced with permanent artificial prostheses such as Teflon and polyurethane. Such prostheses have been selected to be inert, biocompatible, and structurally sound to withstand the high loads which are encountered in the knee joint. Typically, these permanent implants do little to encourage the regeneration of the damaged host tissue. Therefore, what is needed is an improved prosthetic meniscus composed of biocompatible materials, which are biocompatible, compliant, durable, and suitable to acts as a temporary scaffold for meniscal fibrocartilage infiltration and regeneration of the host tissue.

In U.S. Pat. No. 5,184,574 granted to Stone and U.S. Pat. No. 6,042,610 granted to Li, there is disclosed a meniscus replacement material, manufactured by shape molding collagen fibers within a mold via application of low pressure by a piston prior to or after drying. Stone requires the step of applying freezing cycles to the material. The fibrous materials achieve densities of 0.07-0.5 g/cc. Hydrated fibers at these density range from a free flowing liquid slurry to a loose dough-like material unable to maintain a shape. Freezing and possibly lyophilizing of the material is necessary to remove it from the mold and cross-linking solutions are applied to it while still in the frozen or lyophilized state so that it does not warp. Fiber orientation may be obtained by applying a rotating force to the piston in order to form a circumferential orientation. However, this orientation occurs only in areas directly in contact with the rotating piston. What is necessary is a fibrous construct with sufficient integrity to be handled without the necessity of freezing and/or lyophilizing and that can be implanted without the requirement of cross-linking, if desired. Additionally, this construct lacks any consistency throughout the thickness of its structure, being able to create oriented fibers only at the periphery.

Another embodiment of the present invention is directed to devices useful as prosthetic ligament, and in vivo or ex vivo scaffold for regeneration of ligament tissue and to methods for their fabrication.

The anterior cruciate ligament (ACL) of the knee functions to resist anterior displacement of the tibia from the femur during flexure. The ACL also resists hyperextension and serves to stabilize the fully extended knee during internal and external tibial rotation. Partial or complete tears of the ACL are common. The preferred treatment of the torn ACL is ligament reconstruction, using a bone-ligament-bone autograft (e.g., from the patient\'s patellar tendon or hamstring tendon). Cruciate ligament reconstruction generally provides immediate stability and a potential for immediate vigorous rehabilitation. However, ACL reconstruction is not ideal; the placement of intraarticular hardware is required for ligament fixation; anterior knee pain frequently occurs, and there is an increased risk of degenerative arthritis with intraarticular ACL reconstruction. Another method of treating ACL injuries involves suturing the torn structure back into place. This repair method has the potential advantages of a limited arthroscopic approach and minimal disruption of normal anatomy. A disadvantage of this type of repair is that there is generally not a high success rate for regeneration of the damaged tissues due to the lack of a scaffold or other cellular inductive implant.

Another embodiment of the present invention relates to devices useful as a prosthetic intervertebral disc. The intervertebral disc plays an important role in stabilizing the spine and distributing the forces between the vertebral bodies. In the case of a damaged, degenerated, or removed disc, the intervertebral space collapses over time and leads to abnormal joint mechanics and premature development of arthritis.

In the prior art, discs have been replaced with prostheses composed of artificial materials. The use of purely artificial materials in the spine minimizes the possibility of an immunological response. Such materials must withstand high and repeated loads seen by the spinal vertebral joints, early attempts focused upon metallic disc implants. These efforts met with failure due to continued collapse of the disc space and or erosion of the metal prosthesis into the adjacent bone.



The current invention is directed to a general prosthesis, which, when implanted into a mammalian host, undergoes controlled biodegradation accompanied by adequate living cell replacement, such that the original implanted prosthesis is remodeled by the host\'s cells before it is degraded by the host\'s enzymes and/or by hydrolosis. The device of the subject invention is structurally stable, pliable, semi-permeable, and suturable.

Embodiments of this invention can be utilized to repair, augment, or replace diseased or damaged organs, such as rotator cuff injuries, dura defects, abdominal wall defects, pericardium, hernias, and various other organs and structures including, but not limited to, bone, periosteum, perichondrium, intervertebral disc, articular cartilage, dermis, epidermis, bowel, ligaments, tendon, vascular or intra-cardiac patch, or as a replacement heart valve.

The device if this invention could be used for sling procedures (e.g., surgical methods that place a sling to stabilize or support the bladder neck or urethra). Slings are typically used to treat incontinence. Additionally, in the form of a surgical mesh, the device can be used for such applications as hernia and dura repair.

In another embodiment, this invention provides a ligament repair or replacement prosthesis that is biocompatible, is able to withstand ACL forces, and promotes healing of the injured tissues by acting as a scaffold for cellular infiltration. Another embodiment of this invention is to provide an improved disc replacement or prosthesis that is biocompatible, does not interfere with normal vertebral segment motion, is able to withstand normal spinal column forces, does not wear into the surrounding bone, promotes regrowth of intervertebral disc material and acts as a scaffold for fibrocartilage infiltration.

The tissue repair implant of this invention, functioning as a substitute body part, may be flat, tubular, hollow, solid, or of complex geometry depending upon the intended use. Thus, when forming the structure of the prosthesis of this invention, a mold or plate can be fashioned to accommodate the desired shape.

Flat sheets may be used, for example, to support prolapsed or hypermobile organs by using the sheet as a sling for those organs or tissues (e.g., bladder or uterus). Tubular grafts may be used, for example, to replace cross sections of tubular organs such as esophagus, trachea, intestine, and fallopian tubes. These organs have a basic tubular shape with an outer surface and a luminal surface. In addition, flat sheets and tubular structures can be formed together to form a complex structure to replace or augment cardiac or venous valves and other biological tissue structures.

The tissue repair implant of the present invention may be rendered porous to permit the in-growth of host cells for remodeling or for deposition of the collagenous layer. The device can be rendered “non-porous” to prevent the passage of fluids if necessary or the porosity can be adjusted to create a membrane capable of selective permeability. The degree of porosity will affect mechanical properties of the implant, and these properties are also affected by processing (as will be discussed).

The mechanical properties include mechanical integrity such that the tissue repair implant resists creep for the necessary period of time, and additionally is pliable (e.g., has good handling properties) and suturable. The term “suturable” means that the mechanical properties of the layer include suture retention, which permits needles and suture materials to pass through the prosthesis material at the time of suturing of the prosthesis to sections of native tissue. During suturing, such prostheses must not tear as a result of the tensile forces applied to them by the suture, nor should they tear when the suture is knotted. Suturability of tissue repair implant, i.e., the ability of prostheses to resist tearing while being sutured, is related to the intrinsic mechanical strength of the prosthesis material, the thickness of the prosthesis, and the tension applied to the suture. The mechanical integrity of the prosthesis of this invention is also in its ability to be draped or folded, as well as the ability to cut or trim or otherwise shape the prosthesis.

In another embodiment of the invention, reinforcing elements (e.g., threads, fibers, whiskers, textiles, etc.) are incorporated into the tissue repair implant for reinforcement or for different rates of remodeling. Thus, the properties of the tissue repair device can be varied by the geometry of the thread used for the reinforcement. Additionally thread constructs such as a felt, a flat knitted or woven fabric, or a three-dimensional knitted, woven or braided fabric may be incorporated between layers or on the surface of the construct. Porous, non-fibrous sheets of polymer foam may also be incorporated between layers or on the surface of the construct. Such polymer foams can be made by methods known in the art such as particulate leaching or solvent freeze-drying methods.

An embodiment of the present invention may be made by the following steps: providing a mixture comprising a plurality of fibers, a lubricant, and a suspension fluid, with the suspension fluid filling a void space between said fibers and subjecting said mixture to at least one compressive force. The compressive force causes the migration and alignment of said fibers; and may remove substantially all of the suspension fluid from said mixture. The mixture may further comprise a biologically active agent, or a reinforcing agent.

Additionally, the compressive forces may reduce the void space between the fibers, and the lubricant may assist fiber movement during compression, and be in the form of a liquid or a solid, and may be provided in a carrier fluid. The suspension fluid flow may also cause plates of oriented fibers to be formed.

The compressive force may be applied by a molding surface, thereby creating a shaped fibrous member in said mold. Additionally, or alternatively, the material may be machined, allowing the fabrication of complicated shapes.

In a preferred embodiment, at least a portion of said compressed mixture may be cross-linked by exposure to a cross-linking agent. This process will affect the strength and resorption rate of the implant. Additionally, the strength may be tailored by a reinforcing element, such as particulates, threads, fibers, whiskers, textiles, rods, meshes, or combinations thereof. The function or properties of the implant may also be affected by additives, such as ceramics, polymers, cells, biologically active agents, liquids, surfactants, plasticizers, and combinations thereof.


FIG. 1 depicts fibrous dough prior to and after compression.

FIG. 2 depicts a change in fiber orientation and inter-fiber void space as the fibrous dough is compressed.

FIG. 3 depicts fibrous dough prior to and after compression.

FIG. 4 depicts compression of fibrous dough as it passes through rollers.

FIG. 5 depicts three-dimensional compression of fibrous dough.

FIG. 6 depicts compression of a cylindrical mass of fibrous dough.

FIG. 7 depicts incorporation if reinforcing materials within compressed fibers.

FIG. 8 depicts incorporation of particulates, biologics within the compressed fibrous matrix.

FIG. 9 depicts incorporation of microstructures within the compressed fibrous matrix.

FIG. 10 depicts a hemostatic tract plug of compressed fibrous matrix.

FIG. 11 depicts hemispherical cups of compressed fibrous matrix.

FIG. 12 depicts a selectively compressed ring of fibrous matrix surrounding a non-compressed fibrous matrix.

FIG. 13 depicts selective compression of a fibrous matrix.

FIG. 14 depicts compressed fibrous constructs useful surgical applications.

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US 20120277152 A1
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Other USPTO Classes
162151, 162116, 514772, 514773, 514/76
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