The present disclosure generally relates to a surgical implant. More specifically, the present disclosure relates to a surgical implant for repairing a defect in a spinal dura mater.
The brain and spinal cord are bathed in fluid known as cerebrospinal fluid (CSF). This fluid is held inside layers of connective tissue called the meninges, which surround the brain and spinal cord. There are three meningeal layers: the pia mater; the arachnoid mater; and the dura mater. The dura mater, sometimes called the dura, is the outermost layer of the meninges. The dura is normally a tough connective tissue. The CSF is contained within the subarachnoid space, between the arachnoid mater and the pia mater layers. A spinal CSF leak happens when the spinal dura mater has a hole or tear, allowing CSF to leak out of this enclosed space. This results in intracranial hypotension, a low volume of CSF remaining around the brain and spinal cord. The loss of volume of CSF around the brain and spinal cord can result in a range of symptoms, with severe positional headache being the most common. Symptoms can be mild to very disabling. Often, a patient may have very limited ability to function while in the upright position. A wide range of neurologic signs and symptoms may occur, and rarely, dementia, stroke, coma, and even death have been reported.
During spine surgery, injury may occur due to instruments used to decompress nerves, misplaced implants or grafts, manipulation, and ischemia (compromised blood supply). The risk of having a spinal cord injury or a dural tear during spine surgery increases with age as the surgeon needs to cut through toughened spinal ligaments, and in the process, damage the dura. It may also occur in those with previous spine surgery or preexisting spinal cord compression. Surgery to the back of the spine has a higher risk of spinal cord injury or dural tears since it requires cutting through spinal ligaments, which may injure the dura or cord. Special precautions are taken before, during and after surgery to prevent a dural tear or spinal cord injury.
Dural tears are repaired using microsurgical techniques—using a microscope and a fine needle. Small dural tears are sutured or stapled close, while larger ones are reconstructed with a patch or graft. Fat or fibrin glue may be used as a sealant to reinforce the repair.
In some cases, surgical implants for repairing a defect in the dura mater are made of a collagen or collagen like materials. When the implants are applied, they conform to the complex surfaces of the brain or spinal cord. The patches are designed to interact with and often absorb the patient's blood and plasma exudate to promote healing in the tear of the dura. As the blood begins to clot adjacent to the dural patch, depending on the nature of the material the patch was made of, the dural patch is either slowly reabsorbed into the body and replaced by the patient's own dural tissue, or otherwise integrated in such a way that at least some dural tissue grows over the surface of the patch material to maintain a water-tight seal. So too are vascular patches, which are either made of biological tissue, vein material, bovine epicardium, or other man-made materials that have the ability to let vascular endothelial layers cover the inner side, creating a smooth conduit that prevents clot formation within the repaired blood vessel.
Dural patches may be attached with sutures or simply be laid on the dural tear. A disadvantage of the methods currently used in clinical practice is that they only allow for the dural patches either to be laid on top of the tear, or sewn into the defect as a single layer, thus creating either minimal seal, or an opportunity for an uneven seal, or an initial seal that becomes leaky when the contents develop higher pressure including leaking at the suture line or suture holes because there are no additional layers to block leakage from the repair site. A further disadvantage of such implants is they may lead to tissue damage below the dura mater occurring as a result of the suturing process.
Thus, there exists a need in the art for an improved surgical implant to improve a defect in the dura mater.
The needs set forth herein as well as further and other needs and advantages are addressed by the present teachings, which illustrate solutions and advantages described below.
Therefore, it is an object of the invention to create a surgical implant, such as a patch which can be laid into a dural, venous, arterial tear, or other biological hollow structure, covering the opening on both sides (inside and outside) with material that is larger than the defect itself. This objective of the invention helps to keep internal (for example, neural) elements in place during the dural repair (by sealing them in with no egress of fluid which can carry nerves out the opening while the surgeon is trying valiantly to close the defect, making the repair that much harder still) or minimize active blood leakage from a vascular structure during the repair, which would reduce the need for occlusion of the parent vessel to allow the repair to occur. This will also lead to better long-term healing of the defect. Further, the inner portion of the dural patch may protect the nerves, or the vascular patch could reduce platelet aggregation and clot/thrombus formation, and then subsequently promote endothelization inside once the outer layer is sewn closed.
An object of the invention is to provide a patch having a top and bottom layer. The bottom layer can change between two states, a relaxed state, and a tensioned state. In the relaxed state the top and bottom layer are substantially parallel to each other. In the tensioned state, the bottom layer will have been cinched such that its longitudinal perimeter is shorter, albeit the layer would appear thicker from a horizontal view. The cinched, modified shorter longitudinal perimeter of the bottom layer is designed to allow the bottom layer to fit inside a defect in a fluid-containing structure, while the top layer rests outside the outer layer of the structure, keeping it from falling deeper into the structure as well as being the site of the subsequent repair.
The bottom layer may be cinched using a suture threaded through the outside of the bottom layer, or other mechanisms as may be devised. In the case of the suture, once it is released from the inner layer and removed, the bottom layer will uncinch or expand back into the relaxed state and conform to the dura or vessel or tissue opposite the top layer. This results in a more effective seal to the defect than just resting a single layer on top of the dura or tissue or sewing a single layer into or over the defect. The suture may be threaded through the bottom layer in premade holes, premade indentures that make puncturing the inner layer of the patch easier or sewn through without any formal guidance.
The patch may be made of collagen which allows for an organic seal to the dura, vessel, or tissue. A collagen matrix of the patch allows blood and plasma to adhere to it, and form fibrin glue support the repair temporarily. The collagen matrix can then be resorbed harmlessly into the body as the body repairs and overlays the tissue with normal dura or endothelium and vascular tissue.
The third layer, a possible variation in the design, would provide a specific gap between the two layers, designed to match the thickness of the fluid-filled structure (artery, vein, or dura, for example) being repaired, so as not to cause bunching of the original tissue as the space between the outer and inner layers are pulled taut.
The present invention resides in one aspect in a surgical implant for repairing a defect in a spinal dura mater. The implant includes a first layer having a top surface and a bottom surface. The first layer is flexible and planar. The first layer has an edge extending between the top surface of the first layer and the bottom surface of the first layer about a periphery of the first layer. The first layer has an inner portion remote from the periphery of the first layer. The first layer has an outer portion between the periphery of the first layer and the inner portion of the first layer. The surgical implant includes a second layer having a top surface and a bottom surface. The second layer is flexible and planar. The second layer has an edge extending between the top surface of the second layer and the bottom surface of the second layer about a periphery of the second layer. The second layer has an inner portion remote from the periphery of the second layer. The second layer has an outer portion between the periphery of the second layer and the inner portion of the second layer. The bottom surface of the first layer proximate to the inner portion thereof is connected to the top surface of the second layer proximate to the inner portion thereof so that the inner portion of the top layer is fixed relative to the inner portion of the second layer and the outer portion of the first layer is moveable relative to the outer portion of the second layer.
In yet a further embodiment of the present invention, the first layer comprises a collagen-based dura graft material, and the second layer comprises a collagen-based dura graft material.
In yet a further embodiment of the present invention, the spinal dura mater has a defect area and an area of the connection between the bottom surface of the first layer and the top surface of the second layer is less than or equal to the defect area.
In yet a further embodiment of the present invention, the bottom surface of the first layer proximate to the outer portion thereof is adjacent to an outer surface of the spinal dura mater proximate to the defect therein when the surgical implant is received in the defect. The top surface of the second layer proximate to the outer portion thereof is adjacent to an inner surface of the spinal dura mater proximate to the defect therein when the surgical implant is received in the defect.
In yet a further embodiment of the present invention, the edge of the second layer extends at least to the edge of the first layer when the surgical implant is received in the defect in the spinal dura mater so that the outer portion of the second layer inhibits a damage to arachnoid mater below the dura mater resulting from a suturing of the outer portion of the first layer and the dura mater.
In yet a further embodiment of the present invention, the outer portion of the first layer of the implant is fixed relative to the spinal dura mater with a suture between the outer portion of the first layer and the spinal dura mater proximate to the defect.
In yet a further embodiment of the present invention, the second layer is biasable between a retracted position and an extended position. In the retracted position the edge of the second layer about the periphery thereof is drawn together under the inner portion of the second layer thereby facilitating receipt of the second layer through the defect in the spinal dura mater. In the extended position the second layer extends in a plane that is generally parallel to the surface of the dura mater.
In yet a further embodiment of the present invention, a surgical thread is received in the outer portion of the second layer about the periphery thereof. When the second layer is in the retracted position, the surgical thread is tensioned to maintain the second layer in the retracted state. The second layer is biasable to the extended position when the tension is released from the surgical thread.
In yet a further embodiment of the present invention the surgical thread is dissolvable in the body after implantation thereof.
In yet a further embodiment of the present invention, the surgical implant comprises a third layer having a top surface and a bottom surface, the third layer being flexible and planar, the third layer being disposed between the first layer and the second layer, the third layer forming at least in part the connection between the first layer and the second layer.
The present invention resides in yet another aspect in a method for repairing a defect in a spinal dura mater of a patient. The method includes the step of applying a surgical implant to the defect in the spinal dura matter. The implant includes a first layer having a top surface and a bottom surface. The first layer is flexible and planar. The first layer has an edge extending between the top surface of the first layer and the bottom surface of the first layer about a periphery of the first layer. The first layer has an inner portion remote from the periphery of the first layer. The first layer has an outer portion between the periphery of the first layer and the inner portion of the first layer. The surgical implant includes a second layer having a top surface and a bottom surface. The second layer is flexible and planar. The second layer has an edge extending between the top surface of the second layer and the bottom surface of the second layer about a periphery of the second layer. The second layer has an inner portion remote from the periphery of the second layer. The second layer has an outer portion between the periphery of the second layer and the inner portion of the second layer. The bottom surface of the first layer proximate to the inner portion thereof is connected to the top surface of the second layer proximate to the inner portion thereof so that the inner portion of the top layer is fixed relative to the inner portion of the second layer and the outer portion of the first layer is moveable relative to the outer portion of the second layer.
In yet a further embodiment of disclosed method, the first layer comprises a collagen-based dura graft material, and the second layer comprises a collagen-based dura graft material.
In yet a further embodiment of disclosed method, the defect in the spinal dura mater has a defect area, and an area of the connection between the bottom surface of the first layer and the top surface of the second layer is less than or equal to the defect area.
In yet a further embodiment of disclosed method, the bottom surface of the first layer proximate to the outer portion thereof is adjacent to an outer surface of the spinal dura mater proximate to the defect therein when the implant is received in the defect. The top surface of the second layer proximate to the outer portion thereof is adjacent to an inner surface of the spinal dura mater proximate to the defect therein when the implant is received in the defect.
In yet a further embodiment of disclosed method, the method includes the step of suturing the outer portion of the first layer of the implant to the spinal dura mater proximate to the defect.
In yet a further embodiment of disclosed method, the edge of the second layer extends at least to the edge of the first layer when the surgical implant is received in the defect in the spinal dura mater so that the outer portion of the second layer inhibits a damage to an arachnoid mater below the dura mater resulting from a suturing of the outer portion of the first layer and the dura mater.
In yet a further embodiment of disclosed method, the second layer is biasable between a retracted position and an extended position. In the retracted position the edge of the second layer about the periphery thereof is drawn together under the inner portion of the second layer thereby facilitating receipt of the second layer through the defect in the spinal dura mater. In the extended position the second layer extends in a plane that is generally parallel to the surface of the dura mater.
In yet a further embodiment of disclosed method, the method includes the step of releasing a surgical thread received in the outer portion of the second layer about the periphery thereof. The releasing of the surgical thread causes the second layer to bias from the retracted position to the extended position.
In yet a further embodiment of disclosed method, the surgical thread is dissolvable in the body after implantation thereof.
In yet a further embodiment of disclosed method, the implant further comprises a third layer having a top surface and a bottom surface. The third layer is flexible and planar, the third layer is disposed between the first layer and the second layer. The third layer forms, at least in part, the connection between the first layer and the second layer.
These and other aspects of the present invention will become apparent in light of the drawings and detailed description provided below.
The present teachings are described more fully hereinafter with reference to the accompanying drawings. The following description is presented for illustrative purposes only and the present teachings should not be limited to these embodiments.
In compliance with the statute, the present teachings have been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the present teachings are not limited to the specific features shown and described, since the systems and methods herein disclosed comprise preferred forms of putting the present teachings into effect.
For purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description with unnecessary detail.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. The use of “first”, ‘second,’ etc. for different features/components of the present disclosure are only intended to distinguish the features/components from other similar features/components and not to impart any order or hierarchy to the features/components.
The first layer 220 has a top surface 222 and a bottom surface 224. The first layer 220 is flexible. The first layer 220 extends in a plane. The first layer 220 has an edge 226 between the top surface 222 and the bottom surface 224. The edge 226 extends along a periphery 230 of the first layer 220. In reference to
The first layer 220 has an inner portion remote from the periphery 230 of the first layer. The inner portion and area thereof may vary in different embodiments of the present invention. In reference to the embodiment shown in
The second layer 240 has a top surface 242 and a bottom surface 244. The second layer 240 is flexible. The second layer 240 extends in a plane. The second layer 240 has an edge 246 between the top surface 242 and the bottom surface 244. The edge 246 extends along a periphery 250 of the second layer 240. In reference to
The second layer 240 has an inner portion remote from the periphery 250 of the second layer. The inner portion and area thereof may vary in different embodiments of the present invention. The second layer 240 has an outer portion between the periphery 250 of the second layer 240 and the inner portion of the second layer. In some embodiments, the outer portion defines an elliptical annulus in the plane of the second layer 220, wherein the outer extent of the annulus is the periphery 250. The inner area of the annulus is the inner portion of the second layer 220.
The bottom surface 224 of the first layer 220 proximate to the inner portion thereof is connected to the top surface 242 of the second layer 240 proximate to the inner portion thereof so that the inner portion of the first layer is fixed relative to the inner portion of the second layer and the outer portion of the first layer is moveable relative to the outer portion of the second layer. In the embodiment disclosed in
In reference to
Each layer may be made of a different material, each with different tissue or material properties (such as density, flexibility, or porosity), or each layer may be imbued or impregnated with different substances to perform the different tasks of healing innate to the different environments on the inside and outside of the target repaired tissue. In addition, the inner and outer layers may or may not be identical in size, shape, or thickness.
Numerous materials are known for forming the layers. A selected material should restore the continuity of the dura mater, prevents CSF leaks while minimizing infection, facilitates suturing, mimics the compliance of natural dura, and minimizes local tissue inflammation and encourages the infiltration of cells and vasculature to reconstruct native dura without inducing fibrosis or adhesions. Examples include, but are not limited to, autograft, allograft, xenograft, and non-biologic synthetic materials. Although dural substitutes such as autologous pericranium, bovine pericardium, cadaveric dura, autologous fascia lata, muscle have been widely used in cranial surgery, spine surgery generally has relied on using animal-derived or synthetic substitutes. Some examples include, but are not limited to, the following: Durasis, DuraGen or DuraMatrix, Durepair, DuraGuard, Alloderm, Preclude, and Neuro-Patch. Furthermore, Surgicel is sometimes used to augment some dural repairs.
The layer material comprises collagen-based xenografts, namely DuraGen, DuraMatrix, and Durepair. DuraGen (Integra Neuroscience, Plainsboro, N.J.) and DuraMatrix (Stryker, Kalamazoo, Mich.) are synthetic substitutes consisting of type I collagen matrix made from bovine achilles tendon. DuraGen has 20% more conformability than DuraMatrix while DuraMatrix has a 50 times lower liquid permeability rate than DuraGen. DuraGen is perhaps now the most widely used dural substitute for spinal surgeries. DuraGen's porosity allows platelets to infiltrate the matrix and promote fibrin clot formation as well as fibroblasts to enter and lay down natural collagen fibers thus preventing CSF leakage and initiate the dural repair process. In humans, implanted DuraGen was completely resorbed within 1 year (often much earlier) and replaced by the host's collagen derived from infiltrating fibroblasts. It should be understood to a person of ordinary skill in the art the present invention is not limited in this regard and that other biocompatible materials used in accordance with the present invention. It should also be understood that additional materials or layers may be added to the surgical implant to increase the durability or stiffness of the product, as may be required.
Examples of techniques for physically joining the layer 220, 240, 260 include pressing, heating, such as in an oven, with or without a vacuum, exposing the material to heating elements or heated air, or ultrasonically spot welding. The layers may be joined during processing of the collagen material. In some embodiments of the present invention, the layers may be joined using suture. In this manner, the layered implant may be prepared by a surgeon. In some embodiments of the present invention, the surgical implant is formed from a uniform layer of product, such as collagen, which is then subjected to an incision along the periphery, thereby defining the respective sections, namely the layers, of the surgical implant. In some embodiments of the present invention, the inner portions of the layers are connected with an adhesive or sealant. It should be understood that any known method of adhering the layers in accordance with the disclosure may be used and that the present invention is not limited in this regard.
In reference to
The first layer 320 has an inner portion 323 remote from the periphery 330 of the first layer. The inner portion and area thereof may vary in different embodiments of the present invention. The first layer 320 has an outer portion 325 between the periphery 330 of the first layer 320 and the inner portion 323 of the first layer. In some embodiments, the outer portion 325 defines an elliptical annulus in the plane of the first layer 320, wherein the outer extent of the annulus is the periphery 330. The inner area of the annulus is the inner portion 323 of the first layer 320.
The second layer 340 has a top surface 342 and a bottom surface 344. The second layer 340 is flexible. The second layer 340 extends in a plane. The second layer 340 has an edge 346 between the top surface 342 and the bottom surface 344. The edge 346 extends along a periphery 350 of the second layer 340. In reference to
The second layer 340 has an inner portion remote from the periphery 350 of the second layer. The inner portion and area thereof may vary in different embodiments of the present invention. The second layer 340 has an outer portion between the periphery 350 of the second layer 340 and the inner portion of the second layer. In some embodiments, the outer portion defines an elliptical annulus in the plane of the second layer 320, wherein the outer extent of the annulus is the periphery 350. The inner area of the annulus is the inner portion of the second layer 320.
The bottom surface 324 of the first layer 320 proximate to the inner portion thereof is connected to the top surface 342 of the second layer 340 proximate to the inner portion thereof so that the inner portion of the first layer is fixed relative to the inner portion of the second layer and the outer portion of the first layer is moveable relative to the outer portion of the second layer. In the embodiment disclosed in
In reference to
In one embodiment of the present invention, the second layer 220 includes a plurality of holes 261 in the outer portion thereof. The holes 261 extend along the periphery of the second layer 240. A surgical thread 260 is received through the holes 261 so that the length of surgical thread 260 extends along the periphery of the surgical implant. In some embodiments of the present invention, the surgical thread is dissolvable. In this manner, the second layer 240 is biasable between a retracted position and an extended position. In the retracted position, shown partially in
Holes 161 may be through the entire layer 3 or only a starter hole to guide a suture or other device through the holes. In some objects of the invention the holes may not be in place until after a suture, needle, or other object has passed through the second layer. The holes 161 may be scattered along the perimeter of the second layer 240. In one object of the invention, each hole may be the same length away from the edge of second layer 240. In another object, the holes may be scattered more at random through the second layer. In one object of the invention the holes 161 are used to cinch the second layer 240 as described above.
In the embodiment disclosed, the area of the connection between the top layer and the bottom layer, is less than the area of the defect in the tissue. By retracting the second layer 240 in this manner, the present invention enables the second layer, having a great area in the defect, to be received through the aperture defined by the defect. After the second layer 240 is received below the defect 30, the second layer is biased to the extended state by releasing tension on the surgical thread. In reference to
As would be understood by one skilled in the art, the amount the perimeter that is able to be cinched will depend on the structural integrity of the material is made of as well as the distance the holes are from the edge of bottom layer, as well as the tension applied.
In reference to
In reference to
The suture keeps the surgical implant 200 in place so the dura or vessel can heal over the patch. In one object of the invention, the implant may be made of collagen such that blood and plasma can adhere to the collagen matrix. In some embodiments of the present invention, in about 6-8 weeks the collagen matrix will be resorbed and integrated to the tissue. This forms a successful graft repairing the defect.
The sutures are looped through the first layer 220 and through the dura. In one embodiment of the invention a sticky, glue or sealant may be applied, or some texture that promotes otherwise adherence to the dura or hearing. In such an embodiment, the bottom layer 3 may cause resistance to the removal of the dural patch, as it has expanded to a perimeter beyond the perimeter of the wound.
The present invention may use any suture material known in the art. Four examples that are used by spine surgeons to repair dura are Nurolon° (Ethicon, Inc., Sommerville, N.J.), Prolene° (Ethicon, Inc., Sommerville, N.J.), Gore-Tex® (W. L. Gore & Associates, Inc., Flagstaff, Ariz.) and Silk. Nurolon is a non-absorbable, braided suture composed of the long-chain aliphatic polymer of Nylon 6 or Nylon 6,6. It is noted to have 81% tensile strength at 1 year, 72% at 2 years, and 66% at 11 years and elicits minimal acute inflammatory reaction. Prolene is a non-absorbable monofilament suture composed of an isotactic crystalline stereoisomer of polypropylene, a synthetic linear polyolefin. This material does not adhere to tissues, is biologically inert, and elicits minimal tissue reaction and maintains tensile strength for up to 2 years. Gore-Tex suture is a microporous, non-absorbable monofilament made of expanded polytetrafluoroethylene (ePTFE) and its unique structure allows the attachment of needles that approximate the diameter of the thread and is therefore thought to fill the entire needle hole, thus reducing CSF leak at the suture site. Finally, silk suture is made of raw silk spun by silkworms and, although classified as non-absorbable, silk suture becomes absorbed by proteolysis and is often undetectable in the wound site by 2 years. Although several examples are provided here, the present disclosure is not limited in this regard. The described examples may also be used to bias the second layer of the surgical implant.
The present disclosure describes aspects of the invention with reference to the exemplary embodiments illustrated in the drawings; however, aspects of the invention are not limited to the exemplary embodiments illustrated in the drawings. It will be apparent to those of ordinary skill in the art that aspects of the invention include many more embodiments. Accordingly, aspects of the invention are not to be restricted in light of the exemplary embodiments illustrated in the drawings. It will also be apparent to those of ordinary skill in the art that variations and modifications can be made without departing from the true scope of the present disclosure. For example, in some instances, one or more features disclosed in connection with one embodiment can be used alone or in combination with one or more features of one or more other embodiments.
Number | Date | Country | |
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63198368 | Oct 2020 | US |