US20110153000A1 - Non-destructive tissue repair and regeneration - Google Patents

Abstract

A surgical stent made of biocompatible material for implantation in human tissue to enable blood and nutrients to flow from an area of vascular tissue to an area of tissue with little or no vasculature.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is a divisional of U.S. patent application Ser. No. 11/735,144, filed Apr. 13, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 10/558,926, filed Nov. 30, 2005, which is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/US05/013973, filed Apr. 25, 2005, which claims priority to U.S. Provisional Patent Application No. 60/565,428 filed Apr. 26, 2004, all of which are incorporated herein by reference.
FIELD OF INVENTION
• The present invention relates generally to surgical devices for repairing or regenerating body tissue and more specifically to surgical devices for repairing or regenerating soft tissues (i.e. articular cartilage, fibrocartilage, collagenous structures, ligaments, tendons, meniscus, spinal disc, TMJ disc etc . . . ) of the joints (knee, hip, shoulder, temporomandibular joint, spine, fingers, ankle, toes, etc . . . ), and to surgical methods using such devices.
BACKGROUND OF INVENTION
• Meniscus tissue is comprised of a type of tissue known as fibrocartilage. Fibrocartilage is present in the form of a disc (spine, temporo-mandibular joint), meniscus (knee), labrum (shoulder, hip), etc. In the knee, as shown inFIG. 1, the meniscus is a semi-lunar, wedge shaped tissue that sits on top of the tibia and articulates with the tibia and femur during gait activities. It acts as a shock absorber between the femur and tibia and distributes the compressive and shear loads from the curved condyles of the femur to the relatively flat plateau of the tibia. Similar to articular cartilage, much of the meniscus is avascular and aneural. However, as shown inFIG. 2, the meniscus has three zones of vascularity: red zone, red/white zone, and white zone. The red zone refers to approximately the outer peripheral third of the meniscus. This zone is rich in blood supply. The white zone can be found in the approximate inner peripheral third of the meniscus and is void of blood supply, and the red/white zone can be found in the approximate middle third and has a limited blood supply.
• Injuries and pathologies occur in the meniscus, labrum, and disc that manifest themselves in the forms of tears, as shown inFIG. 3, degeneration or other tissue defects. For the purposes of this document, “tissue defect” means any form of non-healthy tissue including, but not limited to, tissue tears, degenerative tissue, non-union bone fracture defects, or any other form of non-healthy tissue. Various types and degrees of tears and defects in the knee meniscus can and do occur often as a result of some twisting action in the knee or as a result of repetitive impact over time. Similar actions in the other joints can result in similar defects and tears in the similar structures present in those joints. Meniscus degeneration can also occur as a result of aging so that soft or hard areas develop in the tissue such that even common activities such as squatting can cause meniscal tears and defects.
• Common surgical procedures for treating meniscal damage include repairing the tears and complete or partial meniscectomies. Repairing a tear is commonly performed when the tear is a longitudinal vertical tear in the vascular (or red) zone of the meniscus. The tear walls can be rasped or trephined to induce bleeding, especially when the tear is just beyond the borders of the red zone (i.e. in the red/white zone). The tear is stabilized with suture or some other repair device such that the relative motion of the tear faces is minimized or eliminated during load bearing. Also, the knee capsule tissue (i.e. synovium) is sometimes rasped to induce bleeding of this highly vascularized tissue into the joint with the intent to provide a better healing environment for meniscal tears. Many devices and surgical procedures exist for repairing meniscal tears by approximating the faces of the meniscal tear. Examples of such devices and procedures are disclosed in the following U.S. Pat. Nos. 6,319,271; 6,306,159; 6,306,156; 6,293,961; 6,156,044; 6,152,935; 6,056,778; 5,993,475; 5,980,524; 5,702,462; 5,569,252; 5,374,268; 5,320,633; and 4,873,976. The other common meniscal procedure, meniscectomy, involves the surgical removal of part of or all of the meniscus. Such procedures have commonly been performed in the case of “un-repairable” or complex tears such as radial tears, horizontal tears, vertical longitudinal tears outside the vascular zone, defibrillation, and/or degeneration. Defects that occur in the avascular (white) or limited vascular (red/white) areas typically do not heal. Meniscectomies typically provide immediate pain relief and restoration of knee function to the patient; however, with the absence of the meniscus, the long term effect on the knee can be cartilage wear on the condylar or tibial plateau surfaces and the eventual development of an arthritic condition such as osteoarthritis. Osteoarthritis is a result of cartilage degradation that is associated with chronic knee pain and often leads to total joint reconstruction. It is for these reasons that meniscal scaffolds and implants have been developed to regenerate or replace the tissue that is removed during a partial or total meniscectomy (see, for instance, U.S. Pat. Nos. 6,042,610; 5,735,903; 5,681,353; 5,108,438; 5,007,934; and 4,880,429).
• Clinical experience indicates that white zone and red/white zone tears and defects typically do not heal even if they are stabilized with standard repair techniques. The option of not treating these types of defects is known to result in propagation of tears and defects and degeneration of the meniscus and subsequent degeneration of the articular cartilage and development of osteoarthritis. However, studies performed by Dr. Steven Arnoczky in animals [Arnoczky S P, Warren R F, Spivak J M; J Bone Joint Surg Am. 1988 September; 70(8):1209-17, “Meniscal repair using an exogenous fibrin clot. An experimental study in dogs.”] and human clinical experience has shown that if the white or red/white zone defect surfaces are in contact with a blood clot (i.e. fibrin clot) then such tears or defects have a greater propensity to heal. So, if a surgeon were to deliver and fix a blood or fibrin clot to tear or defect surfaces, then healing would likely occur. Most surgeons, however, do not attempt to deliver and fix blood/fibrin clots to facilitate the repair of these types of tears because of the technical challenges. These meniscal procedures are typically performed using arthroscopic techniques (i.e. through small portals using an arthroscope or camera to visualize the surgical site). In order to see clearly through the arthroscope, the surgeon is required to constantly infuse the knee with fluid (i.e. saline solution, Ringer's solution, etc . . . ); however, if he or she is trying to deliver a blood clot and fix it in the white or red/white zone defect, then the fluid would typically be turned off so that the clot does not disintegrate during the delivery and fixation stage. With the fluid turned off, the surgeon has the technical challenge of not being able to see the surgical site clearly; therefore, a technical dilemma exists: in order to see more clearly the fluid needs to be turned on, but in order to deliver and fix the clot the fluid needs to be turned off. Therefore, the technical challenges are too difficult to overcome in an arthroscopic environment; the surgeon therefore typically excises injured or degenerated white zone and red/white zone tissue (i.e. performs a partial or total meniscectomy). Performing these procedures in a non-arthroscopic setting (i.e. open condition) is not a viable option due to patient expectations, increased morbidity, and increased risks associated with larger incisions.
• Currently, tissue engineering scaffolds are being developed to replace the meniscal tissue that has been removed, such as for instance, (ReGen Biologics' Collagen Meniscal Implant or CMI and DePuy's (a Johnson & Johnson company) small intestine submucosa meniscal implant. These implants are being developed to regenerate meniscal tissue; however, they are effective only when the implant is placed in direct contact with the vascular (red) zone of the meniscus. Therefore, if the defect area is confined to the avascular zone only, then one of the meniscal implants referred to above will not regenerate that tissue. For the defects that are confined to the avascular zone only, the surgeon must then remove only that portion of the meniscus that is injured and/or diseased and would not expand the defect into the vascular zone, thus removing “good tissue.” So, for those patients with avascular zone defects, the only option today (and even in the future with the above mentioned tissue engineered scaffolds in their current configuration) is a partial meniscectomy with no tissue engineering replacement solution. Unfortunately for the patient who receives the partial meniscectomy, the long term prognosis includes chronic knee pain, break down of the articular cartilage, osteoarthritis, and even eventual total knee replacement.
• Similar to the knee meniscus, other structures are found throughout the body that have avascular and vascular anatomies in close proximity where the avascular portion of these structures have very little propensity for healing. Some of these other structures are the labrum of the hip joint, the labrum of the shoulder joint, the meniscal-like structure of the wrist, the discs of the spine, the disc of the temporomandibular joint, diseased cardiac muscle (i.e. due to reduced blood flow from cardiovascular blockage) to name a few.
• Also, in a spinal application, when a patient presents to a surgeon with a bulging or herniated or ruptured spinal disc, the adjacent vertebral bone is often sclerotic (i.e. thickened or denser). Since much of the nutrients for the spinal disc are delivered via diffusion through the vertebral endplates, the sclerotic bone could tend to decrease the amount of nutrients delivered to the disc, thus contributing to the diseased state of the disc.
SUMMARY OF THE INVENTION
• The present invention is directed toward devices and surgical methods for repair and regeneration of diseased or damaged tissue such as the meniscus in the human knee joint. The devices and methods can also be applied toward the repair and regeneration of diseased or injured other fibrocartilage and tissues of the knee, hip, shoulder, temporo-mandibular joint (TMJ), spine, fingers, wrist, ankle, etc. While in many instances the current specification describes the repair and regeneration of tissue defects in a meniscus, the teachings of the present invention are applicable to tissue defects throughout the body.
• The invention comprises, in one form thereof, a channel for blood, blood components, and cells to travel from a vascular area of tissue to an avascular or partially vascular area of tissue to facilitate healing and/or regeneration in these areas that would otherwise have a lower healing and regeneration capacity.
• It is an objective of the present invention to provide a channel for blood, blood components and/or nutrients, and cells to travel from the vascular (red) zone such as in knee meniscus or synovium (i.e. knee capsule) to the avascular (white) or partially vascular (red/white) zone to facilitate healing and/or regeneration in these zones.
• It is also an objective of the present invention to provide a biocompatible tube. The tube can have a stopping brim to prevent it from being inserted completely through the tissue. The tube is intended to be located within meniscal tissue such that it provides a channel from the vascular zone of the tissue (meniscus or synovium) to the avascular (white) or partially vascular (red/white) region. The tube wall can have openings, perforations, holes, or porosity that allow for blood, nutrients, and cells to enter the tube through the walls of the tube or stent. The tube wall exterior can be roughened or have protrusions or threads that will facilitate its fixation to tissue. The “tube” could be a cylinder with a porous configuration such that blood, nutrients, and cells could travel within and through the device.
• It is also an objective of the present invention to provide a pathway through which blood, nutrients, and cells can pass to facilitate healing of an avascular (or partially vascular) tear/defect or to facilitate regeneration of avascular (or partially vascular) tissue when an implant is placed in addition to the tube(s) after performing a partial meniscectomy. In the case of a partial meniscectomy, the channel could function to deliver a blood or fibrin clot to the volume space of meniscus that was removed such that the clot acts as a scaffold in which cells can travel and propagate, thus, facilitating regeneration of that portion of the meniscus. In this case the open channel would also provide the access of the vascular area components to the in situ scaffold (i.e. blood or fibrin clot).
• It is also an objective of the present invention to be comprised of a network of biocompatible tubes that are either attached to, integral with, or in close proximity to a meniscus implant. The implant is also comprised of a biocompatible material and can have interconnected porosity. The tube can have a stopping brim to prevent it from being inserted completely through the tissue. The meniscus implant/tube(s) device is located adjacent to avascular (white or red/white) meniscal tissue such that the tubes protrude into the meniscal tissue to or through the vascular tissue (meniscus or synovium). The tube(s) provides a channel from the vascular zone of the tissue (meniscus or synovium) to the avascular or partially vascular region into or onto the meniscus implant. This meniscus implant/tube(s) device(i.e. tubes integrated or attached to a scaffold) provides a pathway through which blood, nutrients, and cells can pass to the meniscus implant so that healing and regeneration of an avascular (or partially vascular) defect or tear can be accomplished. The tube portion of the meniscus/tube(s) device can have any or all of the same features as described in the tube device alone.
• It is also an objective of the present invention to provide a method for repairing damaged or diseased fibrocartilage tissue (i.e. meniscus of the knee, labrum of the shoulder, acetabular labrum of the hip, articular disc of the wrist, spinal disc, temporomandibular disc, etc.). After locating the tear, degeneration or other defect in the avascular or partially vascular zone, one of two tasks can be performed. The tissue can be removed from the inner portion of the tear (i.e. perform a partial meniscectomy) or the tear can be repaired using a number of standard repair techniques (vertical or horizontal mattress suturing, Mitek's RapidLoc™ Meniscal Repair Device for the meniscus, Bionx Arrow™ for the meniscus, etc.). If a partial meniscectomy is to be performed followed by implantation of a meniscus regenerating or replacing device or implant, then the stent can be placed into the remnant native meniscal tissue such that it provides an open channel through which blood, nutrients, and cells can flow from the vascular region of the tissue to the implant, thus facilitating healing or regeneration. After a partial meniscectomy, a meniscus/tube(s) device (i.e. tubes integrated or attached to a scaffold) could be implanted and fixed to the remaining native meniscal tissue such that the tube portion of the device protrudes into and/or through the vascular zone of the meniscus and/or synovium. The delivery of the meniscus/tube(s) device could be accomplished arthroscopically with standard techniques. The fixation could be accomplished arthroscopically as well using standard devices and techniques (suture, meniscal repair devices such as DePuy Mitek's RapidLoc, Linvatec's Bionx Arrow, etc.). If the tear is to be repaired (instead of removing the tissue via a partial meniscectomy), then the stent can be arthroscopically placed either using an all inside or inside-out technique from the outer tear surface to or through the vascular region (providing a channel) or through both tear surfaces to the vascular region (providing a channel and a fixation for the tear), thus, facilitating repair of the avascular or partially vascular tear. Alternatively, the stent could be arthroscopically delivered using an outside-in technique.
• It is also an objective of the present invention to provide a method for delivering biological treatments [i.e. blood, blood components, platelet rich plasma, tissue, bone marrow, bone marrow components, stem cells, fibroblast cells, synoviocyte cells, other cells, angiogenic factors (new blood vessel formation growth factors such as VEGF, IGF, etc . . . ), other growth factors, hyaluronic acid, gene therapies, other biologic molecules etc.], drugs [analgesic, anti-clotting, clotting, anti-inflammatory, anti-infectives, etc . . . ], and other substances to the tear or defect area through the tube. After the tube device is positioned or during/before the insertion process, a substance could be delivered through the tube either to the tear/defect area or to the vascular area. The substance could enhance or initiate healing, increase blood flow, improve angiogenesis, induce clotting in the duct and tear/defect, deliver cells, deliver growth factors, deliver biologic elements, etc.
• It is also an objective of the present invention to provide devices as mentioned above that would be used in other joints of the body such as the hip, the wrist, the shoulder, the ankle, fingers, the toes, the spine, the temporomandibular joint, etc.
• It is also an objective of the present invention to provide devices as mentioned above that would be used in cardiac muscle. For instance, if the cardiac arteries are diseased and/or blocked to the point where the cardiac muscle is starved for blood and nutrients, a tube(s) could be implanted into the cardiac muscle such that blood is delivered to the compromised cardiac muscle from an area where vascularity is more abundant.
• It is also an objective of the present invention to be comprised of a channel for blood, blood components, and cells to travel from a vascular area of bone to an avascular or partially vascular area, such as articular cartilage, to facilitate healing and/or regeneration in these areas that would otherwise have a lower healing and regeneration capacity. For instance, when a surgeon encounters a patient with osteochondritis dessicans (OCD), the typical surgical treatment is to remove the cartilage defect or flap and then proceed to microfracture or microdrill the subchondral bone to induce bleeding and provide a pathway for bone marrow components to aid in the healing of the OCD lesion. The surgeon, in addition to or instead of microfracturing and microdrilling, could insert one or more stents that would retain the channel into the bone such that blood and marrow components and cells could have access to the OCD lesion, thus, improving the healing capacity of that tissue site. Also, in a spinal application, when a patient presents to a surgeon with a bulging or herniated or ruptured spinal disc, often the adjacent vertebral bone is sclerotic (i.e. thickened or more dense) and can impede the nutrient flow from the vertebral bone to the spinal disc. Therefore, the surgeon could insert one or more stents into the vertebral bone such that an open channel is created from the vertebral bone to the disc space. Alternatively, the surgeon could insert the stents into the periphery of the disc, through the outer capsule such that the capsular vascularity would have access to the spinal disc interior. This latter procedure could be performed using techniques similar to an epidural procedure.
BRIEF DESCRIPTION OF DRAWINGS
• The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
• FIG. 1 shows a normal meniscus;
• FIG. 2 shows a cross sectional view of a normal meniscus;
• FIG. 3 shows a cross sectional view of a meniscus showing a vertical tear in the red/white zone;
• FIG. 4 shows a cross sectional view of a meniscus showing a vertical tear in the red/white zone with a stent inserted;
• FIG. 5 shows a cross sectional view of a meniscus showing a vertical tear in the red/white zone with a stent inserted and the tear repaired;
• FIG. 6 shows a cross sectional view of a meniscus showing a vertical tear in the red/white zone with an inserted stent acting as a fixation device;
• FIG. 7 shows a meniscus with a vertical tear;
• FIG. 8 shows a meniscus with the tissue that is on the inner side of the avascular or partially vascular tear removed, i.e., with a partial meniscectomy;
• FIG. 9 shows a cross sectional view along line9-9 of the meniscus ofFIG. 8;
• FIG. 10 shows the meniscus ofFIG. 9 with a stent placed therein;
• FIG. 11 shows the meniscus ofFIG. 9 with a stent with a stopping brim placed therein;
• FIG. 12 shows a cross sectional view along line9-9 of the meniscus ofFIG. 8 with a stent and an implant or regeneration device;
• FIG. 13A shows a perspective view of a stent in the shape of a cylindrical tube;
• FIG. 13B shows a perspective view of a stent in the shape of a cylindrical porous rod;
• FIG. 14 shows a perspective view of a stent in the shape of a cylindrical tube with a stopping brim;
• FIG. 15 shows a perspective view of a stent in the shape of a cylindrical tube with external circumferential ribs;
• FIG. 16A shows a perspective view of a stent in the shape of a cylindrical tube withexternal threads37;
• FIG. 16B shows a perspective view of a stent in the shape of a cylindrical tube with external threads having a variable pitch;
• FIG. 17 shows an elevational view of another embodiment of a stent in the shape of a cylindrical tube with external circumferential fins;
• FIG. 18 shows a perspective view of a stent in the shape of a cylindrical tube with external longitudinal ribs;
• FIG. 19 shows an end view of the stent ofFIG. 16A;
• FIG. 20A shows a perspective view of a driver that is used to deliver a stent into tissue;
• FIG. 20B shows a perspective view of a driver with the stent ofFIG. 13A loaded onto it;
• FIG. 21 shows a perspective view of a driver with the stent ofFIG. 17 loaded onto it;
• FIG. 22 shows a perspective view of a driver with a stent being delivered into tissue;
• FIG. 23 shows a perspective view of a driver with a delivery needle after delivering a stent into tissue;
• FIG. 24 shows a view of the stent ofFIG. 16A having a lead in chamfer;
• FIG. 25 shows a perspective view of the stent ofFIG. 24 having a driver slot in the back end of the stent;
• FIG. 26 shows a perspective view of a driver with raised bosses;
• FIG. 27 shows a perspective view of the slotted stent ofFIG. 25 and the slot driver ofFIG. 26 in the loaded condition, ready for insertion into tissue;
• FIG. 28 shows a perspective view of a knee cross section showing some of the major structures;
• FIG. 29 shows a perspective view of a driver having a cannula; and
• FIG. 30 is a partial sectional view of a bone with a stent positioned therein.
• Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplifications set out herein illustrate embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
• FIG. 1 shows a view of a normal meniscus. The meniscus has a triangular cross section as shown inFIG. 2. The top of the articulating surface1 interfaces with the femoral condyle and the bottom of the articulatingsurface4 interfaces with the tibial plateau. Theinner edge8 and theouter rim2 are indicated in the figure. Theouter wall3 defines the outermost boundary of the meniscus tissue.
• FIG. 2 shows a cross sectional view of a normal meniscus showing approximate locations of the vascular (red) zone7, avascular (white) zone5, and partially vascular (red/white)zone6 in an adult human.
• FIG. 3 shows a cross sectional view of a meniscus with avertical tear11 in the red/white zone6. The inner and outer tear faces,9 and10, are indicated in this figure.
• FIG. 4 shows a cross sectional view of a meniscus with avertical tear11 in the red/white zone6 with astent12 inserted at the outer tear face10 through the vascular (red) zone7. Thetear11 has not yet been repaired in this figure. Theouter opening13 of thestent12 in this example is located at the meniscusouter wall3; therefore, the stent outer opening would be positioned at the interface of the meniscus and synovium (or capsule) of the knee (SeeFIG. 28:items47 &52).
• FIG. 5 shows a cross sectional view of a meniscus which has avertical tear11 in the red/white zone6 with astent12 inserted at the outer tear face10 through the vascular (red) zone7. Thetear11 has been repaired using avertical mattress suture14 technique.
• FIG. 6 shows a cross sectional view of a meniscus with avertical tear11 in the red/white zone6 with astent12 inserted through both tear surfaces (9 &10) from the avascular (white) zone5 through the vascular (red) zone7. In this example, thestent12 acts as a tube to provide a pathway for blood, nutrients, cells, etc . . . from the vascular area7 to the partially vascular area and also acts as a fixation device to approximate the inner9 and outer10 tear faces together. Therefore, in this example, the blood, nutrients, cells, etc . . . facilitate the biological healing. The fixation device also mechanically holds the inner9 and outer10 tear surfaces together so that healing can occur.
• FIG. 7 shows a view of a meniscus with avertical tear11 in the avascular (white)5 or partially vascular (red/white)zone6 of the meniscus. Theinner edge8 andouter rim2 of the meniscus are indicated in this figure for orientation purposes.
• FIG. 8 shows a view of a meniscus with the tissue, which is located on the inner side of the avascular or partially vascular tear, removed (i.e. partial meniscectomy performed). Theposterior15,anterior17 and outer16 walls define thedefect18 created by the partial meniscectomy procedure. This figure represents the standard of care given by an orthopaedic surgeon to a patient with a tear or defective tissue in the avascular5 or partially vascular6 zone of the knee meniscus.
• FIG. 9 shows a cross sectional view of a meniscus that has the inner side of the avascular or partiallyvascular tear11 removed as indicated by lines9-9 ofFIG. 8.
• FIG. 10 shows a cross sectional view of the meniscus after a partial meniscectomy (similar toFIG. 9) except that astent12 has been inserted to reach from the avascular (white)5 or partially vascular (red/white)6 tear face(s) (9 &10) to or through the vascular (red) zone7 of the meniscus to or into the synovium of the knee. In this example, thestent12 would act to provide a channel through which blood could flow and eventually clot, creating a naturally derived scaffold with biological factors in which cells can travel, reside, and thrive. The channel which would also have blood clotted in it would provide a pathway through which cells from the outer region could find their way to the scaffold. This combination of blood clot, biological factors, and cells would provide the proper environment for that portion of the meniscus that was removed to be regenerated.
• FIG. 11 shows a cross sectional view of the meniscus after a partial meniscectomy with astent12 in place (similar toFIG. 10) except thestent12 has a stoppingbrim29 to impede or prevent it from advancing outwardly.
• FIG. 12 shows a cross sectional view of the meniscus that has the inner side of the avascular (white) or partially vascular (red/white) tear removed (partial meniscectomy). Astent12 that has been inserted to reach from the avascular (white)5 or partially vascular (red/white)6 tear face9 to the vascular (red) zone7. An implant orregeneration device20 is fixed against theface10 of the remaining meniscus such that the stent opening interfaces with the implant ordevice20.
• For orientation,FIG. 28 shows a perspective view of a knee cross section showing some of the major structures. Thefibula49 andtibia50 bones comprise the lower leg thigh bones; whereas, thefemur54 is the upper leg or thigh bone. Themedial meniscus51 andlateral meniscus55 are indicated in cross section beneath themedial condyle52 andlateral condyle46, respectively, and above thetibial plateau55. Theouter wall3 of the medial51 and lateral47 menisci are in contact with the medial synovium (or knee capsule)52 and lateral synovium (or knee capsule)47, respectively.
• A variety ofstents12 utilizing the principles of the present invention are illustrated in the following drawings. The illustratedstents12 are intended for implantation in a patient for channeling blood and/or nutrients from a vascularized area7 of the tissue to a non- (5) or less6 vascularized area of the tissue, thus, facilitating repair of that non-5 or less6 vascularized tissue of the body in the patient. The illustrated embodiments would most commonly be used in repairing meniscus tissue of the knee; however, the invention is not so limited. As used herein, the term stent refers to a device that is composed of a biocompatible (bioabsorbable or non-absorbable) material and has anopen channel28 that acts to route blood, nutrients, and/or cells from a vascular area7 to an area that is not as vascularized (5,6). The open channel is not required to be a through hole orunimpeded lumen28. The open channel could be accomplished via interconnective porosity present in a biocompatible material that is configured in the shape of a stent12 (FIG. 13B). Thestent12 acts to maintain the hole (or a channel or separation of tissue) in the tissue for a time so that blood or nutrients can be supplied to a limited vascular area to facilitate healing.
• As used herein, bioresorbable, resorbable, bioabsorbable, and absorbable are intended to be interchangeable. All four terms are intended to mean materials that are naturally degradable in vivo over time. All are intended to include both natural and man-made materials and to include new materials, as they are developed, unless a specific material or a type of material are identified. Bioabsorbable materials useful for creating stents of the present invention include polyesters; poly-L-lactic acid (PLLA); polyglycolic acid (PGA); polydioxinone (PDS or PDO); polycaprilactone (PCL); polyvinyl alcohol (PVA); polyethylene oxide (PEO); poly(trimethylene carbonate): polymers disclosed in U.S. Pat. Nos. 6,333,029 and 6,355,699, the disclosures of which are hereby expressly incorporated by reference herein; polymers derived from tyrosine; polymers derived from chitosan; small intestine submucosa (SIS), urinary bladder submucosa, materials derived from collagenous tissues.
• Referring now toFIG. 13A, thestent12 is shown composed of a tube with anouter surface25, aninner surface26, and a throughlumen28. Thestent12 is ideally 2 cm or less in length but could be longer, depending on the distance between the tear ordefect11 and the vascular area7 from which the blood, nutrients, and cells will come. The inner diameter or dimension of thelumen28 is ideally in the 0.5 to 3.0 mm range and can be either larger or smaller depending on the actual tissue in which it is implanted. The wall thickness of the stent is ideally in the 0.1-1.0 mm but could be thicker or thinner as required due to the loads induced by the surrounding tissue and biomechanics. Additionally holes27 through theouter surface25 andinner surface26 can be provided. The purpose of theholes27 is to provide access ports through which blood and nutrients can flow from a vascularized area7, as shown inFIGS. 2-6, into thestent12. Theseholes27 could be in the form of porosity or discrete holes. Ideally thehole27 diameter will be in the 0.05 to 1.0 mm range but could be larger or smaller depending on the tissue type, desired cell types, nutrients, etc . . . that one wishes to enter and/or exit throughholes27. Note that holes27 do not necessarily have to be round or square or elliptical or any consistent geometry in particular but rather could be in the form of various pores of various shapes and geometries. In the case of porosity, the ideal size is in the 10 to 5000 micron range and this porosity could be either through porosity or interconnective porosity. The exit/entrance ends13 of throughlumen28 also provides an access port through which blood, nutrients, and cells can travel to areas ofless vasculature6 or no vasculature5, as shown inFIGS. 2-6. Theseaccess ports27 and28 also provide entrance and exit pathways for cells to thrive. Note that thestents12 shown in FIGS.13A and14-18 could exist without a throughlumen28. Instead, thestent12 could be a solid appearing cylinder with porosity throughout the structure as shown inFIG. 13B. The porosity could be in the form of discrete holes that are interconnected or in the form of interconnective porosity. This same structure could be accomplished by inserting a porous cylinder into the throughlumen28 of thestent12 shown in FIGS.13A and14-18 either before or after insertion of thestent12 into tissue. Note that theouter surface25 of thestent12 can be smooth or can be roughened to aid in fixation ofstent12, and to increase surface area contact ofstent12 with native tissue. The roughenedouter surface25 can also act as a rasp during insertion to increase the amount of bleeding and, thus, expose more vasculature in the vascular area7 and/or the partiallyvascular area6 of the tissue.
• Thestent12 illustrated inFIG. 13B is similar to stent ofFIG. 13A but is a porous rod. Theporosity47 can be accomplished through mechanical means (i.e. drilling, stabbing, picking, etc . . . ) or through material means (i.e. interconnective porous material, lyophilization of slurry material, etc . . . ) or through other means (i.e. 3-D printing, etc . . . ). The ideal size of the pores is in the 10 to 5000 micron range. The porosity allows for blood, nutrients, and cells to travel through thestent12 from an area of vascularity to an area of limited or no vascularity, thus, facilitating healing of the limited or no vascular tissue.
• Thestent12 illustrated inFIG. 14 is similar tostent12 ofFIG. 13A but also has a stoppingbrim29 so that thestent12 can be inserted into tissue only a predetermined distance as illustrated inFIG. 11. Thus, thebrim29 would impede thestent12 from traversing further into the tissue. Thebrim29 could be circular, square, rectangular, trapezoidal, elliptical, scalloped, segmented, etc . . . and is required to be larger than the dimension of theouter surface25 of thestent12. Thebrim29 as indicated inFIG. 14 is ideally 0.5-2.0 mm larger than theouter surface25 dimension and is ideally 0.05-1.0 mm thick. This impedance function could be accomplished by a gradual transition from the smallerouter surface25 dimension to thebrim29 dimension (i.e. ramping up from theouter surface25 to the outer brim29). In this case, the ramp transition could happen over a length along the long axis of thestent12 of 1-10 mm ideally but could occur over a shorter or longer length.
• FIG. 15 shows astent12 with externalcircumferential ribs36 which help with fixation ofstent12 in tissue. The tissue has elasticity associated with its material properties so that the tissue will somewhat conform to the outer geometry of thestent12 after insertion; therefore, the externalcircumferential ribs36 will become imbedded into the tissue, thus, impeding thestent12 from moving once positioned. Tissue also has a material property commonly referred to as viscoelasticity. The tissue, therefore, will, with time, conform to the outer geometry of the stent even more. The plurality of externalcircumferential ribs36 could be one or more ribs.FIG. 15 indicates four externalcircumferential ribs36. The spacing betweenribs36 is ideally 2-10 mm; however, it could be more or less, depending on the tissue, the application, and the other dimensions of theribs36. Ideally the externalcircumferential ribs36 extend radially outwardly from theouter surface25 by 0.1-2.0 mm; however, they could extend to a greater or lesser amount as well. The axial width of theribs36 ideally will be in the 0.1-2.0 mm range but, again, could be wider or narrower, depending on the specific application. Also, the plurality of externalcircumferential ribs36 that are shown in this figure are not required to share common dimensions.Stent12 includes an outer diameter defined byouter surface25 and the radially outward extent ofribs36. The outer diameter defined atribs36 comprises the largest value of the outer diameter ofstent12, while the other diameter defined byouter surface25 defines the smallest value of the outer diameter ofstent12. In one exemplary embodiment of the present invention, the end of thestent12 utilized in accordance with the present invention that is positioned adjacent to a tissue defect will have an outer diameter value that is less than the largest outer diameter of the stent, e.g., the outer diameter defined byribs36. In certain exemplary embodiments, the stent will have its smallest outer diameter at the end position adjacent to the tissue defect.
• FIG. 16A shows astent12 withexternal threads37 which help with fixation ofstent12. UnlikeFIG. 15,stent12 indicated inFIG. 16A can be turned or screwed into the tissue as opposed to pushed into the tissue as with thestent12 ofFIG. 15 withcircumferential ribs36. The thread pitch or the number ofthreads37 per mm or per inch can vary, depending on tissue type, other dimensions, and application, to name a few. Either a “coarse” or “fine” thread spacing could be used effectively in the stent. Ideally theexternal threads37 extend from theouter surface25 by 0.1-2.0 mm; however, they could extend to a greater or lesser amount as well. The axial width of theribs13 ideally will be in the 0.1-2.0 mm range but, again, could be wider or narrower, depending on the specific application. A variable pitch could also be applied to thestent12 as shown inFIG. 16B, especially for the application indicated inFIG. 6 where thestent12 also acts as a fixation device to pull and retain thetear11 faces (9,10) together. Thevariable pitch thread37 could be used to ensure that the two faces (9,10) of thetear11 are pushed together after implantation of thestent12. The variable pitch would include smaller thread spacing at one end of thestent12 with larger thread spacing on the opposite end. This variable pitch would tend to pull the two surfaces (9,10) of thetear11 together.Threads37 may terminate before an end ofstent12 in certain embodiments. In these embodiments, the end ofstent12 that does not include threads can be positioned adjacent to the tissue defect as described above. In the case of a meniscal tear, configuringstent12 to have a smaller outer diameter at the location of a meniscal tear is useful because the meniscus will likely be thinner adjacent to the tear location and thicker in the vascular area in which the opposite end of the stent is positioned.
• FIG. 24 shows an isometric view of the type of stent indicated inFIG. 16A. Note that thestent12 inFIG. 24 has an added feature of a lead inchamfer43. Thischamfer43 provides less resistance into the tissue than a blunt end as shown inFIG. 16A or16B; therefore, with thestent12 ofFIG. 24 insertion will be easier to initiate into tissue.FIG. 19 shows across section40 of thestents12 ofFIGS. 16 and 24. Thenon-circular cross section40 could be used to drive thestent device12 into tissue with a driver that has a similar cross section.
• InFIG. 19, the internal cross section of thestent12 is shown as a square or rectangle. The internal cross section could be any non-circular geometry (i.e. square, rectangle, triangle, trapezoidal, elliptical, hexagonal, star, circular with a key slot, etc . . . ). The matching geometry of adriver45 would be used to torque thestent12 into the tissue.FIG. 25 shows a slotted41 version of a threaded stent. Theslot42 interfaces with the raisedboss44 of thedriver45 indicated inFIGS. 26 and 27.
• A surgeon could insert the sharpenedtip35 of thedriver45 shown inFIG. 20A, followed by the lead inchamfer43 of thestent12 ofFIG. 24. As the surgeon turned thedriver45, thethreads37 would interface with the tissue and screw thestent12 into the tissue. After delivery of the stent, thedriver45 could be pulled out of thestent12 and knee joint, thus, leaving thestent12 behind in the tissue. In this way, the stent can be inserted into the tissue by separating the tissue to provide an access for the stent without removing or ablating the tissue.
• FIG. 17 shows astent12 with externalcircumferential fins38 which help with fixation into the tissue. The difference between thefins38 and theribs36 is essentially the edge geometry. Where therib36 configuration impedes forward and backward motion equally, the configuration offin38 impedes motion opposite to the insertion direction. The insertion direction is indicated by thearrow46. In other words, thefin38 geometry is configured such that insertion of thestent12 into tissue requires less force than removal of thestent12 from tissue in the opposite direction from the insertion direction. The fin geometry is configured such that the forward side offin38 is ramped up from the outer surface and back such that as thestent12 is inserted into the tissue, thefin38 flexes back; however, if a force in the opposite direction of the insertion force is applied to thestent12, then thefin38 “digs” into the tissue to resist that force and, thus, resist motion of thestent12 in that direction. As explained in connection with thecircumferential rib36 embodiment ofFIG. 15, the tissue has elasticity associated with its material properties so that the tissue will somewhat conform to the outer geometry of thestent12 after insertion; therefore, thefins38 will become imbedded into the tissue, thus, impeding thestent12 from moving once positioned, especially in the direction opposite to the direction of insertion. The tissue also has a material property commonly referred to as viscoelasticity. The tissue, therefore, will conform to the outer geometry of the stent even more with time. The plurality of externalcircumferential fins38 could be one or more fins. This figure indicates three externalcircumferential fins38. The spacing betweenfins38 is ideally 2-10 mm; however, it could be more or less, depending on the tissue, the application, and the other dimensions of thefins38. Ideally the externalcircumferential fins38 extend from theouter surface25 by 0.1-2.0 mm; however, they could extend to a greater or lesser amount as well. The axial width of thefins38 ideally will be in the 0.1-2.0 mm range but, again, could be wider or narrow, depending on the specific application. Also, the plurality of externalcircumferential fins38 that are shown in this figure are not required to share common dimensions.
• FIG. 18 shows externallongitudinal ribs39 which help with fixation ofstent12. The purpose of theselongitudinal ribs39 is to resist rotation of thestent12 about the long axis ofstent12. Since the tissue is elastic, it will somewhat conform to the outer geometry of thestent12 after insertion; therefore, thelongitudinal ribs39 will become imbedded into the tissue, thus, impeding thestent12 from rotating. The tissue's viscoelasticity will cause the tissue to conform to the outer geometry of the stent even more with time. The plurality of externallongitudinal ribs39 could be one or more ribs. This figure indicates four externallongitudinal ribs39. The circumferential spacing between theribs39 is ideally equally spaced (in this case 90 degrees apart); however, it could be more or less, depending on the tissue, the application, and the other dimensions of theribs39. Ideally the externallongitudinal ribs39 extend from theouter surface25 by 0.1-2.0 mm; however, they could extend to a greater or lesser amount as well. The circumferential width of theribs39 ideally will be in the 0.1-2.0 mm range but, again, could be wider or narrow, depending on the specific application. The profile of theribs39 does not necessarily need to be consistent from end to end. In fact, the leading edge of therib39 may be ramped as shown inFIG. 18 so that insertion of thestent12 may be made easier. Also, the plurality of external longitudinal ribs that are shown in this figure are not required to share common dimensions.
• FIG. 20A shows adriver45 that could be used to insert astent12. A surgeon could insert the sharpenedtip35 ofdelivery needle33 ofdriver45, followed by thestent12 as shown inFIG. 20B orFIG. 21. As the surgeon pushed on thedriver45, thestent12 would travel into the tissue as shown inFIG. 22. As shown inFIG. 22, in certain embodiments of the present invention, the step of inserting the stent into the meniscus comprises insertingstent12 into the meniscus throughtissue defect16. After delivery of the stent, thedriver45 could be pulled out of thestent12 and knee joint, thus, leaving thestent12 behind in the tissue as shown inFIG. 23.
• FIG. 30 illustratesstent12 positioned inbone103, with one end ofstent12 terminating attissue defect101 formed incartilage100. In this position, the opposite end ofstent12 reaches below subchondral bone to access bone marrow to facilitate healing ofbone defect101. In the event thatstent12 extends fromdefect wall16 after it has been positioned to access vascular zone7, the remaining portion ofstent12 can be trimmed off (e.g., by a scalpel) to define a stent end terminating adjacent totissue defect16. In one exemplary embodiment,stent12 is positioned such that one end thereof terminates adjacent to the tissue defect. In certain embodiments, positioning an end ofstent12 adjacent to a tissue defect means positioning an end of stent12 a distance of not more than ¼ of the length ofstent12 from the tissue defect. In other embodiments, the end ofstent12 positioned adjacent a tissue defect will be positioned not more than 3 mm from the tissue defect. In certain embodiments,stent12 will span a tissue defect in the meniscus and the meniscal rim.
• FIG. 21 shows a perspective view of astent12 that is loaded onto adelivery needle33 placed in contact withsurface40. In this position, thestent12 is ready to be inserted into tissue. The stent indicated in this figure is thestent12 ofFIG. 17 except that it has the additional feature of a lead inchamfer43 to facilitate ease of insertion initiation. Any of thestents12 in the preceding figures could be shown in this figure, especially thestents12 found inFIGS. 13,14,15, &18;
• A variety of materials may be used to manufacturestent12. For example, stents could be manufactured from biocompatible polymers, biocompatible collagenous matrices, and/or any combination thereof. Other materials such as bioactive agents, biologically derived agents, inorganic materials that are biocompatible, cells, and biological lubricants can also be included as part of these components. Note that the term biocompatible polymers is intended to include both synthetic polymers and biologically derived polymers (i.e. collagen). Some examples of biocompatible polymers include: polyesters; poly-L-lactic acid (PLLA); polyglycolic acid (PGA); polydioxinone (PDS or PDO); polycaprilactone (PCL); polyvinyl alcohol (PVA); polyethylene oxide (PEO); poly(trimethylene carbonate); polymers disclosed in U.S. Pat. Nos. 6,333,029 and 6,355,699; polymers derived from tyrosine; polymers derived from chitosan; small intestine submucosa (SIS), urinary bladder submucosa, polymers derived from collagenous tissues; any other biocompatible polymer that is or is not bioabsorbable, or co-polymer, or mixture of polymers or co-polymers that are used in the construction of implants. In addition, as new biocompatible materials that may be or may not be bioabsorbable are developed, it is expected that at least some of them will be useful materials from which at least some of these components could be made. Also, the inner surface ofstent12 as well as the inner surface of theholes27 could be configured such that an anti-coagulant material could be coated or chemically or otherwise bonded to the surface such that coagulation of the blood is impeded so as to facilitate blood flow. Note that the above materials are identified by way of example only, and the present invention is not limited to any particular material unless expressly called for in the claims.
• A variety of materials may be used to manufacture thescaffold20 ofFIG. 12. For example,scaffold20 could be manufactured from biocompatible polymers, biocompatible collagenous matrices, and/or any combination thereof. Other materials such as bioactive agents, biologically derived agents, inorganic materials that are biocompatible, cells, and biological lubricants can also be included as part of these components. Similar to the preceding paragraph the term biocompatible polymers is intended to include both synthetic polymers and biologically derived polymers (i.e. collagen), and the material listed above also apply to scaffold20. The configuration of the scaffold material could be such that interconnective porosity is accomplished. This could via a variety of methods, including use of nonwoven or woven or knitted fibers, foam, sponge, etc . . . material configurations. Again, note that the above materials are identified by way of example only, and the present invention is not limited to any particular material unless expressly called for in the claims. In one exemplary embodiment,stent12 is at least as stiff as meniscal tissue.
• When referring to ribs (36,39),fins38, orthreads37, the number of such could be one or more. Also, any combination of such features could be included in astent12.
• The stents illustrated inFIGS. 13-18 and24-25 are intended to be surgically implanted into tissue for use in helping with the repair of avascular5 or limited vascular6 tissue.FIG. 2 is a schematic of a human knee meniscus tissue that contains a range of vasculature. In the outer third of theperiphery3, the vasculature is abundant (red zone-7); whereas, the inner third of the meniscus has no vasculature (white zone-5), and the middle third of the meniscus has limited vasculature (red/white zone-6). When a tear ordefect11 occurs in the white5 or red/white6 zone as shown inFIG. 3, the probability of a successful repair occurring when standard repair techniques are employed is much lower than tears ordefects11 that occur in the red zone7 because of the lack of blood or nutrients in the white5 or red/white6 zones. Therefore, astent12, if inserted through the outer tear surface wall10 (FIG. 4) or through both the outertear surface wall10 and inner tear surface wall9 as shown inFIG. 6 and continues through the meniscal tissue to or through the red zone7, would provide achannel28 through which blood, nutrients, and cells could travel to the tear surfaces9,10 and, thus, facilitate healing of the compromised tissue. Blood can enter into thestent12 through theend13 ofstent12 that is inserted in the red zone7 and/or through the holes27 (or porosity) in thestent12 wall (25,26). If the stentouter surface25 were configured and thestent12 positioned such that it could adequately approximate the tear surfaces9 &10 as shown inFIG. 3 (i.e.external threads37 either consistent or variable pitch orcircumferential ribs36 orfins38, etc . . . ) and secure those surfaces as illustrated inFIG. 6, thestent12 could also function as a fixation device for thetear11.
• In addition to facilitating the healing of avascular or partially vascular meniscal tears, the stents illustrated inFIGS. 13-18 and24-25 could also be implanted surgically to facilitate healing after a partial meniscectomy (FIG. 8) of the white5 or red/white6 zone is performed with or without an implant orregeneration scaffold20 in place. After a partial meniscectomy is performed (FIG. 8), thestent12 would be inserted through theouter defect wall16 as illustrated inFIG. 10 and continue to or through the red zone7 of the meniscus. After thestent12 is positioned, the meniscal implant orregeneration device20 could be implanted into the defect created by the partial meniscectomy with whatever surgical technique is appropriate as shown inFIG. 12. Thestent12 will then function to maintain achannel28 to allow blood, nutrients, and cells to travel to the meniscal implant orregeneration device20 such that regeneration is facilitated. Note that thestent12 could also be used, not only to provide achannel28 to the vascular7 portion, but as a fixation device to attach the meniscal implant orregeneration device20 to theouter defect wall16 of the meniscus. Note also that the stent could be used without the meniscal implant orregeneration device20. In this case, the stent would provide a pathway for blood to find its way to the defect and eventually clot such that a blood clot would be delivered in situ to the defect site. The clot would then become the scaffold (or meniscal implant or regeneration device20). Alternatively or in addition to, a substance could be injected through thestent12outer opening13 that could then become the meniscal implant orregeneration device20.
• Stents12 illustrated inFIGS. 13-18 and24-25 could be implanted surgically using thedriver45 ofFIG. 20A. Thestent12 could be sized to fit over thesmaller diameter shaft33 of the driver as indicated inFIGS. 20B,21,22,27 Thelarger diameter shaft34 of the driver acts as ashoulder40 to push thestent12 into the tissue. Thesharp tip35 of thesmaller diameter shaft33 would pierce or cut the meniscal tissue to allow thestent12 to be inserted into thehole13 that is created in the meniscus (FIGS. 22 and 23). Upon retraction of the driver, thestent12 would remain in the tissue, being held in the tissue by friction between thestent12 and the tissue. This frictional resistance force could be increased, depending on the design of theribs36,fins38, or roughness of theouter surface25. Thestent12 would, thus, provide achannel28 through which blood, nutrients, and cells could travel and reside. The driver (FIG. 20A) could have an axial actuation feature between thesmaller diameter shaft33 and thelarge diameter shaft34 such that after thestent device12 is inserted in the tissue, thesmaller diameter shaft33 is retracted while maintaining the position of thelarger diameter shaft34 against thestent device12, thus, effectively preventing thestent device12 from retracting during the removal of thesmaller diameter shaft33. Note that the driver ofFIGS. 20A & 21, could also be cannulated (i.e. have a throughhole48 along its long axis as shown inFIG. 29) such that it can be inserted over a needle (i.e. guide needle). The guide needle could be inserted first using an “all inside” or “inside-out” arthroscopic surgical technique for instance, with Linvatec's (a Conmed co.) Zone Specific® cannulae or Sharpshooter® tissue repair system. These systems allow for delivery of flexible needles to specific areas of the meniscus or knee. After the guide needle is in position, the driver (with cannulation) andstent12 ofFIG. 21 could be fed over the guide needle and into the tissue until it is in position using an “all inside” or “outside-in” arthroscopic surgical technique. Also note that the above “all inside” or “outside-in” arthroscopic surgical technique for delivery of thestent12 could be accomplished without the use of a guide needle. Note these arthroscopic surgical techniques are commonly used by orthopaedic surgeons throughout the world.
• In addition to the aforementioned push in delivery technique that has just been described above, the threaded36stent12 ofFIG. 16A or16B could be delivered withdriver45 with adelivery needle33 that matches thenon-circular cross section40 of the internal dimension of thestent12. Using the identical “all inside” or “inside-out” arthroscopic surgical technique described above to delivery a guide needle and the “all inside” or “outside-in” arthroscopic surgical technique described above to deliver thestent12. The only difference is that the threaded36stent12 would be turned or screwed into position as opposed to pushed into position. Therefore, the threaded36stent12 position could be more easily adjusted after initial fixation has occurred.
• In addition to being used in the knee for blood, nutrient, and cells to travel to defects that occur in the avascular7 or partially vascular6 areas of the meniscus such that repair or regeneration can occur, thestent12 described and illustrated in the figures could also be used in many other tissues throughout the body that have similar vascular/avascular anatomies. For instance, it could be used in the labrum of the hip joint, the labrum of the shoulder joint, the meniscal-like structure of the wrist, the discs of the spine, the disc of the temporomandibular joint, diseased cardiac muscle (i.e. due to reduced blood flow from cardiovascular blockage) to name a few.
• It not only could be used in “soft tissue” such as meniscus, discs, labrum, cartilage, etc . . . , but it could also be used in bone. For instance, in spinal applications when a patient presents to a surgeon with a bulging or herniated or ruptured spinal disc, the adjacent vertebral bone is often sclerotic (i.e. thickened or denser). Since much of the nutrients for the spinal disc are delivered via diffusion through the vertebral endplates, the sclerotic bone could tend to decrease the amount of nutrients delivered to the disc, thus contributing to the diseased state of the disc; therefore, if one ormore stents12 were placed through the sclerotic bone of the adjacent vertebra, then blood, nutrients, and cells could be delivered to the damaged or diseased disc and, thus, facilitate repair of the tissue. Also, for cartilage or cartilage/bone defects caused by the disease called osteochondritis dessicans (OCD), the typical surgical treatment is to remove the cartilage defect and then proceed to microfracture or microdrill the subchondral bone (i.e. the bone beneath the articular cartilage defect) to induce bleeding and provide a pathway for bone marrow components to aid in the healing of the OCD lesion. Therefore, the surgeon, in addition to or instead of microfracturing and microdrilling, could insert one ormore stents12 into the subchondral bone so that a channel would be retained in the bone such that blood, marrow components, nutrients, and cells could have access to the OCD lesion, thus, improving the healing capacity of that tissue site. Also, thestent12 could be used in bone applications where non-union fractures occur. For instance, it could be inserted into the bone on either side of the fracture point(s) such that a fresh hematoma (mass of blood) may be created at or near the fracture site and thus facilitate repair or union of the fracture.
• While most of the descriptions here have referred to asingle stent12 in these applications, it is likely thatmultiple stents12 will be used to facilitate the repair of tissue. The spacing betweenstents12 will depend on the tissue to be healed, the extent of damage, the type of defect, the native tissue, etc . . . ; however, for a typical vertical tear that may occur in the knee meniscus avascular7 or partially vascular6 area, the spacing will likely be in the 5-10 mm range with larger or smaller spacing potentially.
• After thestent12 is implanted in tissue, it could also function as a portal through which biological treatments [i.e. blood, blood components, platelet rich plasma, tissue, bone marrow, bone marrow components, stem cells, fibroblast cells, synoviocyte cells, other cells, angiogenic factors (new blood vessel formation growth factors such as VEGF, IGF, etc . . . ), other growth factors, hyaluronic acid, gene therapies, other biologic molecules etc.], drugs [analgesic, anti-clotting, clotting, anti-inflammatory, anti-infectives, etc . . . ], and other substances could be delivered to area of interest. In addition to acting as a portal,stent12 could also be coated with the biological treatments, drugs and other substances referred to in the preceding sentence. The treatment could enhance or initiate healing, increase blood flow, improve angiogenesis, induce or prevent clotting in the duct and tear/defect, deliver cells, deliver growth factors, deliver biologic elements, etc.
• As used herein, passage of fluid refers to passage of blood, cells, growth factors, biological components, blood vessels, and the like. In regard to blood, passage or flow throughstent12 will occur for some time after which the blood will clot through a series of biological processes, thus forming a fibrin clot within the stent. The clot is rich in growth factors and biological material that has chemo-attractant capabilities and, thus, can send out biochemical signals to attract cells. Thus, the biochemical environment of the clot along with its physical structure allow for cells to infiltrate, travel through, and thrive within the stent as they proceed to the defect at the opposite end of the stent. As the cells travel through the stent via the clot, they lay down new tissue and new blood vessels such that healing can occur within the tissue and at or near the defect. Passage of cells through the clot is also encompassed by the phase “passage of fluid”, as that phrase is used in this document.
• While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims (24)

1. A stent, comprising:

an elongate body formed of a bioabsorbable material, said elongate body having a first end, a second end, an exterior surface and a length, said elongate body configured to allow passage of fluid therethrough, said elongate body formed of a material of sufficient rigidity so that the elongate body is at least as stiff as meniscal tissue.

2. The stent ofclaim 1, wherein said elongate body comprises a hollow tube which is open at both the first end and the second end of the elongate body to define end apertures.

3. The stent ofclaim 2, wherein a wall forming the hollow tube includes a plurality of apertures sized to enable blood, nutrients and cells to enter the elongate body from a vascular area of tissue.

4. The stent ofclaim 1, wherein said exterior surface of the elongate body includes a rib.

5. The stent ofclaim 4, wherein said exterior surface of the elongate body includes a plurality of ribs that encircle the outer surface.

6. The stent ofclaim 4, wherein the rib comprises a thread.

7. The stent ofclaim 6, wherein the thread has a consistent pitch.

8. The stent ofclaim 1, wherein the elongate body includes a collar for limiting the travel of the stent into tissue.

9. The stent ofclaim 1, wherein said elongate body has an outer diameter over the length of the elongate body from a larger value at the first end of the elongate body to a smaller value at the second end of the elongate body.

10. The stent ofclaim 9, further comprising a thread extending from an outer surface of said elongate body, said thread defining the larger value of said outer diameter.

11. A stent, comprising:

an elongate body formed of a bioabsorbable material, said elongate body having a first end, a second end, an exterior surface and a length, said elongate body configured to allow passage of fluid therethrough; and

securing means for securing said elongate body in an area of tissue.

12. The stent ofclaim 11, wherein said elongate body comprises a hollow tube which is open at both the first end and the second end of the elongate body to define end apertures.

13. The stent ofclaim 12, wherein a wall forming the hollow tube includes a plurality of apertures sized to enable blood, nutrients and cells to enter the elongate body from a vascular area of tissue.

14. The stent ofclaim 11, wherein said securing means comprises a rib extending from said exterior surface of the elongate body.

15. The stent ofclaim 14, wherein said securing means comprises a plurality of ribs extending from said exterior surface of the elongate body that encircle the outer surface.

16. The stent ofclaim 14, wherein the rib comprises a thread.

17. The stent ofclaim 16, wherein the thread has a consistent pitch.

18. The stent ofclaim 11, wherein the elongate body includes a collar for limiting the travel of the stent into tissue.

19. The stent ofclaim 11, wherein said securing means comprises a fastener operable to secure said elongate body in an area of tissue.

20. The stent ofclaim 11, wherein said elongate body has an outer diameter varying over the length of the elongate body from a larger value at the first end of the elongate body to a smaller value at the second end of the elongate body, said elongate body configured to allow passage of fluid therethrough.

21. The stent ofclaim 20, further comprising a thread extending from an outer surface of said elongate body, said thread defining the larger value of said outer diameter.

22. A stent, comprising:

an elongate body formed of a bioabsorbable material, said elongate body comprising:

a first end;

a second end;

an exterior surface, said elongate body having an outer diameter and a length, said elongate body comprising a hollow tube which is open at both the first end and the second end of the elongate body to define end apertures, whereby said elongate body allows passage of fluid therethrough, said elongate body formed of a material of sufficient rigidity so that the elongate body is at least as stiff as meniscal tissue, a wall forming the hollow tube;

securing means for securing said elongate body in an area of tissue; and

an interior surface defining said hollow tube, said interior surface defining a non-circular cross-section.

23. The stent ofclaim 22, wherein said outer diameter of said elongate body varies over the length of the elongate body from a larger value at the first end of the elongate body to a smaller value at the second end of the elongate body.

24. The stent ofclaim 22, further comprising a rib extending from said exterior surface of said elongate body, said rib forming a consistently-pitched thread about said exterior surface of said elongate body.

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