US 20040228901 A1
A method of treating a synovial joint by injecting particles of collagen-based material into the joint. The particles may be dehydrated before implantation, and rehydrated after implantation, or they may be implanted in a “wet” state—such as a slurry or gel. Radiocontrast materials may be included to enhance imaging of the injected material. Other additives may include analgesics, antibiotics, proteoglycans, growth factors, and/or other cells effective to promote healing and/or proper joint function.
1. A method of treating a synovial joint, said method comprising surgically adding to a synovial joint a composition comprising particulate collagen-based material.
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20. A method according to any of claims 2 through 19 wherein said synovial joint is a facet joint.
21. A synovial joint with a collagen-based material injected in the joint capsule.
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40. A synovial joint according to any of claims 21 through 39 wherein said synovial joint is a facet joint.
 This application claims the benefit of U.S. Provisional Patent Application 60/426,613, filed Nov. 15, 2002.
 The present invention relates generally to materials and methods for treating synovial joints, and more particularly to materials and methods for augmenting synovial joints with collagen-based materials.
 Synovial joints are the most common joints of the mammalian appendicular skeleton, representing highly evolved, movable joints. A typical synovial joint comprises two bone ends covered by layer of articular cartilage. The cartilage is smooth and resilient, and facilitates low-friction movement of the bones in the joint.
 The bone ends and associated cartilage are surrounded by a joint capsule—a “sack” of membrane that produces synovial fluid. The capsule and fluid protect and support the cartilage and connective tissue, carrying nutrients to the articular cartilage and removing the metabolic wastes.
 The articular cartilage is a thin (2-3 mm) layer of hyaline cartilage on the epiphysis of the bone. It lacks a perichondrium, and thus has a limited capacity for repair when damaged. Additionally, the natural aging process can cause the articular cartilage to degenerate somewhat, reducing its capacity to protect and cushion the bone ends.
 Zygapophysial joints, better known as facet joints, are the mechanism by which each vertebra of the spine connects to the vertebra above and/or below it. Each joint comprises two facet bones—an inferior facet and a superior facet—with the inferior facet of one vertebra connecting to the superior facet of an adjacent vertebra. The joints facilitate movement of the vertebra relative to each other, and allow the spine to bend and twist.
 As in all synovial joints, where the facets contact each other there is a lining of cartilage lubricated by a thin layer of synovial fluid. The cartilage and synovial fluid decrease friction at the joint, extending joint life and preventing inflammation and associated pain.
 As the natural aging process progresses, the cartilage covering the joint may deteriorate and start to fray. The fraying process may cause pieces of cartilage to break free, and the previously smooth surfaces may become rough. The facet bones then begin to rub together, creating friction which leads to further deterioration of the joint. Moreover, the nerves associated with the joint become irritated and inflamed, causing severe pain and restricting movement of the spine.
 Techniques for addressing degeneration of synovial joints in general, and facet joints in particular, joint have heretofore relied primarily on injections to block pain and reduce inflammation. This treatment is only temporary though, and rarely leads to any significant improvement of the underlying condition.
 A need therefore exists for materials and methods effective for treating degenerating synovial joints, and particularly for materials and methods effective for supplementing or replacing the cartilage that lubricates and protects the joint. The present invention addresses that need.
 Briefly describing one aspect of the present invention, there is provided a method for treating synovial joints by injecting a collagen-based material into the joint. The material may be injected in a dehydrated form, and rehydrated after implantation, or it may be injected in a hydrated form, such as a slurry or gel. The material may be fresh or frozen. Cross-linking agents such as glutaraldehyde may be included in the injected material to promote collagen crosslinking. In addition, radio-contrast materials may be included to enhance imaging of the injected material. Similarly, performance-enhancing additives such as analgesics and/or antibiotics may be included to provide additional therapeutic benefits.
 Objects and advantages of the claimed invention will be apparent from the following description.
FIGS. 1A-1D show a procedure for injecting a collagen-based material into a facet joint, according to one preferred embodiment of the present invention.
FIGS. 2A-2F show a procedure for injecting a collagen-based material into a facet joint, according to another preferred embodiment of the present invention.
 For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain preferred embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the preferred embodiments being contemplated as would normally occur to one skilled in the art to which the invention relates.
 As indicated above, one aspect of the present invention relates to materials and methods for using collagen-based material to treat a degenerating synovial joint. In the most preferred embodiments the collagen-based material is injected into the joint capsule. In some preferred embodiments the inventive method includes surgically adding to a synovial joint a composition comprising particulate collagen-based material. In other embodiments the inventive method includes surgically adding to a synovial joint a composition consisting essentially of particulate collagen-based material.
 The collagen-based material may be derived from natural, collagen-rich tissue, such as intervertebral disc, fascia, ligament, tendon, demineralized bone matrix, etc. The material may be autogenic, allogenic, or xenogenic, or it may be of human-recombinant origin. In alternative embodiments the collagen-based material may be a synthetic, collagen-based material. Examples of preferred collagen-rich tissues include disc annulus, fascia lata, planar fascia, anterior or posterior cruciate ligaments, patella tendon, hamstring tendons, quadriceps tendons, Achilles tendons, skins, and other connective tissues.
 The collagen-based material may be provided in any form appropriate for introduction into a synovial joint. For example, the material may be a solid, porous, woven, or non-woven material, and may be provided as particles, small pieces, gel, solution, suspension, paste, fibrous material, etc. The material may be used while it is still fresh and hydrated, or it may be used after having been processed, such as having been frozen and/or dehydrated.
 In some embodiments the material is provided in a dehydrated state, and is “rehydrated” after injection in the joint. In other embodiments the material is implanted in a hydrated state. When the material is implanted in a hydrated state, it may be that way because it has never been dehydrated, or it may have been dehydrated and reconstituted. When reconstituted, the material may be reconstituted with saline or another aqueous medium, or it may be reconstituted with a non-aqueous medium such as ethylene glycol or another alcohol. Moreover, when provided in a “hydrated” state, the material may be provided as a gel, solution, suspension, dispersion, emulsion, paste, etc.
 In the most preferred embodiments the material is a particulate and/or fibrous material suitable for injection through a hypodermic needle into a synovial joint.
 In the most preferred embodiments the collagen material is provided as particles ranging between 0.05 mm and 5 mm in size. When materials such as fascia lata or disc annulus particles are used the particles preferably range in size from 0.1 mm to 5 mm. When materials such as demineralized bone matrix or gelatin are used the particles preferably range in size from 0.05 mm to 3 mm. When small plugs of material are used the plugs preferably range in size from 0.5 mm to 5 mm. In some embodiments larger sized pieces, such as pieces up to 20 mm in size, may be used.
 The materials may be processed or fabricated using more than one type of tissue. For example, mixtures of fascia lata and demineralized bone matrix may be preferred in appropriate cases, as may mixtures of DBM and annulus fibrosis material.
 Cross-linking agents may be added to the formulation to promote cross-linking of the collagen material. For example, glutaraldehyde or other protein cross-linking agents may be included in the formulation. The cross-linking agents may promote covalent or non-covalent crosslinks between collagen molecules. Similarly, agents to inhibit protein denaturization may also be included. Crosslinking agents that would be appropriate for use in the claimed invention are known to persons skilled in the art, and may be selected without undue experimentation.
 When the material is to be used as a slurry or gel, additives to promote slurry or gel formation may also be included. These additives may promote protein folding, water binding, protein-protein interactions, and water immobilization.
 In addition, a radiographic contrast media, such as barium sulfate, or a radiocontrast dye, such as sodium diatrizoate (HYPAQUE®), may be included to aid the surgeon in tracking the movement and/or location of the injected material. Radiocontrast materials appropriate for use in discography are known to persons skilled in the art, and may be selected for use in the present invention without undue experimentation.
 Finally, other additives to provide benefits to the injected collagen-based material may also be included. Such additives include analgesics to reduce pain, antibiotics to minimize the potential for bacterial infection.
 Polysaccharides such as proteoglycans and/or hyaluronic acid may also be included to attract and/or bind water to keep the synovial joint hydrated. Additionally, growth factors and/or other cells (e.g., intervertebral disc cells, stem cells, etc.) to promote healing, repair, regeneration and/or restoration of the joint, and/or to facilitate proper joint function, may also be included. Additives appropriate for use in the claimed invention are known to persons skilled in the art, and may be selected without undue experimentation.
 In some embodiments the collagen material is dehydrated before injection into the joint, where it is rehydrated by absorbing fluid from the surrounding area. In other embodiments the collagen material is provided as a gel, slurry, or other hydrated formulation before implantation.
 The collagen-based material is “surgically added” to the synovial joint. That is, the material is added by the intervention of medical personnel, as distinguished from being “added” by the body's natural growth or regeneration processes. The surgical procedure preferably includes injection through a hypodermic needle, although other surgical methods of introducing the collagen-based material into the joint may be used. For example, the material may be introduced into a synovial joint by extrusion through a dilated opening, infusion through a catheter, insertion through an opening created by trauma or surgical incision, or by other means of invasive or minimally invasive deposition of the materials into the joint space.
 Referring now to the drawings, FIGS. 1A-1D show one method of injecting a collagen-based material into a joint. In FIG. 1A, dehydrated particulate fascia lata or annulus fibrosis material 11 is provided in a syringe 12 (in a sterile package). The material is rehydrated and/or dispersed in a suspension medium as shown in FIG. 1B, to provide a wet dispersion 13 of collagen-based material. A hypodermic needle 14 is attached to syringe 12, and the syringe is inserted into the joint capsule 16 (FIG. 1C). The needle/syringe may be moved around within the joint capsule, sweeping from side to side and back and forth, to ensure uniform distribution of the collagen-based material 13 within the space, as shown in FIG. 1D. It is preferred, however, that the tip of the needle be maintained near the center of the joint capsule to ensure deposition of the material within the space, and to minimize potential leakage.
 Alternatively, small diameter collagen plugs 21 may be inserted into the joint as shown in FIGS. 2A-2F. The collagen plugs 21 may be compressed before or by insertion into a small diameter tube 22, and are provided in a delivery cannula 23 (FIGS. 2A-2C). The delivery cannula 23 is attached to a dilator 24.
 The compressed plugs are inserted into a joint 25 by penetrating the joint with a guide needle 27 (FIG. 2D). Dilator 24, preferably with delivery cannula 23 already attached, is inserted over guide needle 27 (FIG. 2E). The collagen plugs 21 are then ready for injection (or extrusion) into the joint. A plunger 28 may be used to push the plugs from the cannula. The plugs expand upon exiting the dilator, and may further expand as they rehydrate in the joint.
 Benefits and advantages arising from use of the materials and methods of the present invention include the following:
 (1) the invention provides lubrication and/or cushioning to degenerated synovial joints, improving or restoring proper joint function;
 (2) the rehydration provided by the invention is expected to slow the degenerative process;
 (3) the invention relieves pain due to improved lubrication of the joint;
 (4) the procedure is percutaneous or a minimally invasive outpatient procedure;
 (5) the risks are minimal, as similar techniques and materials are used in cosmetic procedures;
 (6) the materials are biocompatible since natural or human-recombinant collagen-based materials are used;
 In one preferred embodiment the materials and methods of the present invention may be used to treat synovial joints in the spine, particularly facet joints. In other preferred embodiments hip, knee, ankle, finger, toe, elbow, shoulder, wrist, sacroiliac, temporomandibular, carpometacarpal, etc., joints may all be treated by injecting a collagen-source material into the joint space to supplement/augment the cartilage that lubricates the joint.
 Reference will now be made to specific examples using the processes described above. It is to be understood that the examples are provided to more completely describe preferred embodiments, and that no limitation to the scope of the invention is intended thereby.
 A gel or suspension of hydrated particulate or fibrous (autologous or allogenic) fascia lata in a biocompatible medium such as water, saline, or ethylene glycol is used to supplement the cartilage of a facet joint. The particle size can be in the range from 0.01 mm to 5 mm, preferably between 0.05 and 0.25 mm. The suspension is injected directly into the articular facet joint space through an intact joint capsule using a hypodermic needle. The suspension is contained within the joint capsule following injection. The medium subsequently diffuses out of the disc space and leaves the hydrated fascia lata material behind. A single injection is effective for improving the facet joint structure, although additional injections may be necessary to achieve appropriate level of treatment.
 A gel or suspension of hydrated particulate or fibrous allogenic annulus fibrosis in a biocompatible medium such as water, saline or ethylene glycol is used to supplement the cartilage of a facet joint. The particle size can be in the range from 0.01 mm to 5 mm, preferably between 0.05 and 0.25 mm. The suspension is injected directly into the articular facet joint space through an intact joint capsule using a hypodermic needle. The suspension is contained within the joint capsule following injection. The medium subsequently diffuses out of the disc space and leaves the hydrated annulus fibrosis material behind. Single injection is desirable; however, additional injections may be necessary to achieve the appropriate level of treatment.
 Dehydrated annulus fibrosis material in granule, particulate or power form is used to supplement the cartilage of a facet joint. The particle size can range between 0.01 mm and 5 mm, preferably between 0.05 to 0.25 mm. The material is loaded in its dehydrated state into a specially designed syringe for delivery of particulate matter. The material is extruded into the articular facet joint space through a small, dilated capsule opening. The material remains inside the articulating facet joint space after the needle is removed. It subsequently absorbs moisture or body fluids and swells up in vivo.
 While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.