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  Method and apparatus for filling a cavityUSPTO Application #: 20050278023Title: Method and apparatus for filling a cavity Abstract: An implant for filling and/or distracting a body region, particularly a non-soft tissue cavity, has a plurality of segments wherein at least two of the segments are flexibly connected. The segments have a crush-strength sufficient to create and/or maintain the distraction of two or more non-soft tissue body surfaces, and to maintain the stability of the body region. The implant may be inserted into a cavity by an applicator having a cannula with a distal opening, and a rotary driver for applying force to move the implant within the cannula. (end of abstract)
Agent: Morrison & Foerster LLP - Palo Alto, CA, US Inventor: Paul A. Zwirkoski USPTO Applicaton #: 20050278023 - Class: 623011110 (USPTO) Related Patent Categories: Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor, Implantable Prosthesis The Patent Description & Claims data below is from USPTO Patent Application 20050278023. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD [0001] Described here are non-soft tissue cavity implants, implant applicators, delivery devices, and methods for using them. In particular, the description relates to implants having a plurality of flexibly connected segments having a strength sufficient to support, to fill, to create, to maintain, or to distract a bone cavity such as might be found in a fractured vertebral body, and methods and devices for inserting implants into non-soft tissue cavities such as bone cavities. BACKGROUND [0002] Proper treatment of orthopedic conditions such as trauma, fractures, non-unions, tumors, cysts, and certain fusion procedures may involve filling a cavity that has been created by the pathology itself or by the action of a surgeon. Often the cavities are compressed, and require that the surfaces of the cavity be distracted from one another and then supported to return the bone structure to its anatomic position and form. Furthermore, because non-soft tissues such as bone have a structural and support role in the body, it is critical that such cavities be repaired to allow reliable strength and support. [0003] Compression fractures are one type of hard tissue injuries belonging to a class of conditions that may be treated using devices and methods for separating, distracting, and supporting a fractured bone. For example, vertebral compression fractures are crushing injuries to one or more vertebra. A vertebral compression injury may be the result of a trauma to the spine, an underlying medical condition, or a combination of a trauma and an underlying condition. Osteoporosis and metastatic cancers are common medical conditions that also contribute to vertebral compression fractures because they weaken spinal bone, predisposing it to compressive injury. [0004] Osteoporosis is a degenerative disease that reduces bone density, and makes bone more prone to fractures such as compression fractures. An osteoporosis-weakened bone can collapse during even normal activity. According to the National Institute of Health, vertebral compression fractures are the most common type of osteoporotic fractures. [0005] Vertebral fractures may be painful and may deform the shape of the spine, resulting in unhealthy pressure on other parts of the body, loss of height, and changes in the body's center of gravity. Untreated, such changes and the resulting discomfort can become permanent, since the bone heals without expanding the compression. [0006] Existing methods of treating bone injuries such as compression fractures and bone voids may involve highly invasive or inadequate treatments. For example, one method of treatment is percutaneous vertebroplasty. Vertebroplasty involves injecting bone filler (such as bone cement) into the collapsed vertebra to stabilize and strengthen the crushed bone. In vertebroplasty, physicians typically insert a small diameter guide wire or needle along the pedicle path intended for the bone filler delivery needle. The guide wire is advanced into the vertebral body under fluoroscopic guidance to the delivery point within the vertebrae. The access channel into the vertebra may be enlarged to accommodate the delivery tube. In some cases, the delivery tube is placed directly into a vertebral body and forms its own opening. In other cases, an access cannula is placed over the guide wire and advanced into the vertebral body. In both cases, a hollow needle or similar tube is placed into the vertebral body and used to deliver the bone filler into the vertebra. [0007] When filling a bone cavity with bone filler using traditional vertebroplasty, fillers with lower viscosities may leak. Further, even fillers having low viscosities may require the application of a high pressure to disperse the bone filler throughout the vertebral body. However, application of high pressure also increases the risk of bone filler extravasation from the vertebral body. Conversely, injecting a bone filler having a higher viscosity may provide an even greater risk of "leaking" bone filler into sensitive adjacent body areas. Leaks or extrusion of the bone filler may be dangerous to a patient's health. For example, posterior extravasation from a vertebral body may cause spinal cord trauma, perhaps resulting in paralysis. Risk of leakage is even more acute when a bone filler is applied under pressure to expand a compression fracture, especially if the fracture has begun healing and requires substantial force to distract the cavity surfaces. [0008] Furthermore, most bone cements and bone fillers are difficult to remove or to adjust. Removal and adjustment may be important when distracting a bone cavity. For example, removing a precise amount of bone filler may allow a surgeon to adjust the level of distraction of a vertebral compression fracture and correct the shape of the compressed bone. Many bone cements, once set, are difficult or impossible to remove without further, highly invasive, surgery. Even if the removal is attempted prior to the expiration of the setting time, the materials may have non-Newtonian flow characteristics requiring a substantial removal vacuum to achieve an initial and sudden movement. [0009] The implant could be utilized in any area of non-soft tissue where the filling of a cavity with stability and control is desired, for example, intervetebral disc repair, hip, tibia, and other areas of bone displacement. [0010] In addition to traditional bone cements, a handful of other bone cavity filling materials have been suggested. In particular, biodegradable and/or bioabsorbable bone-filling devices have been suggested. For example, U.S. Pat. No. 5,756,127 to Grisoni et al. describes a bioresorbable string of calcium sulfate hemihydrate (Plaster of Paris) beads and a means for producing these beads. However, the Grisoni device is not intended for distracting a non-soft tissue cavity, and has many disadvantages. Calcium sulfate hemihydrate (Plaster of Paris) and similar materials have low crush strength, making them unreliable as materials to distract and later support a bone cavity, particularly during the early stages of the healing process. Filling materials that are readily compressed or crushed, may shift within, or exit the bone cavity altogether, leading to detrimental changes in the shape of the corrected bone. Materials with low crush strength (particularly those materials having crush strengths less than that of normal bone) are poor choices in withstanding the stress of distracting the bone surfaces, and may be unable to maintain the distracted shape of the bone after filling a bone cavity. Similar materials are the subjects of U.S. Pat. No. 6,579,533 to Tormala et al. [0011] U.S. Pat. No. 5,702,454 to Baumgartner describes an implant made of an elastic plastic for implanting into an intervertebral disk. Because the Baumgartner implant is elastic, it may be less effective for filling and distracting body cavities benefiting from implants having some stiffness, such as non-soft tissue cavities. This is particularly true where sustained distraction is desired. [0012] U.S. Pat. No. 6,595,998 to Johnson et al. describes a tissue distraction device in which wafers are inserted to distract a tissue cavity by forming a wafer stack within the cavity. However, Johnson's column of wafers is not amenable to providing uniform support to all surfaces of a bone cavity, when such support is needed. For example, a tissue cavity supported or distracted on all sides of the cavity may be more stable. [0013] U.S. Pat. No. 5,958,465 to Klemm et al. describes a method and apparatus for making a drug containing implants in the form of a string of beads comprising chains of small drug-containing plastic bodies arranged in series on a surgical wire or thread. Similar drug implanted beads-on-a-string are described in U.S. Pat. No. 6,183,768 to Harle and German Patents 2320373 to Klemm and 2651441 to Heusser. The Klemm, Harle, and Heusser implants are designed for drug delivery, and are embedded with one or more drugs which are released from the plastic (e.g. PMMA) beads (also called "corpuscles"). Thus, these implants may be limited in strength and durability because of the inclusion of a releasable drug, as well as the properties and shape of the implant beads. [0014] In any event, none of the cited documents show the device and methods disclosed below. BRIEF SUMMARY [0015] Broadly, described here are segmented implants for filling a non-soft tissue cavity, applicators for inserting implants, and methods of using the segmented implants and applicators to fill and/or distract tissue cavities. In particular, the implants described here may be used for filling and/or distracting non-soft tissue cavities such as a bone cavity. Generally, the segmented implants described here comprise a plurality of segments, where at least two of the segments are flexibly connected, and configured for insertion into a body region. The segments provide implant segment distractibility to the body region, and stability to the body region into which they are introduced. In some variations of the implant described herein, the segments have sufficient material strength to distract two or more non-soft tissue surfaces. In some versions, the material strength is crush strength, so that the segments of an implant have sufficient crush strength to allow and sustain the distraction of non-soft tissue surfaces. Thus, the implant is inserted into a cavity to distract, to expand, to reduce, or to support the cavity, typically filling the cavity and maintaining a desired shape. [0016] At least a portion of the segments of the implant may be configured so that the implant may be introduced into a body region by engaging a rotating introducer member. For example, a rotatable driver may be used to introduce the segments of the implant into a body region using an applicator as described herein. In some versions, the segments are configured as pellets. [0017] The implant may also include a fluent material (such as bone cement). Thus, for example, the fluent material may be added to a bone cavity that has been distracted by the flexibly connected segments of the implant. The segments may also include a channel or channels to facilitate the passage of a fluent material, for example a bone cement that may eventually harden. [0018] Two or more of the implant segments may be connected in any way allowing sufficient flexibility so that the implant may be introduced into body region such as a bone hollow. The implant segments may include a connection material for connecting segments of the implant. Connection material may comprise, for instance, a string, fiber or wire, variously of single or multiple strands. The connecting string, fiber or wire may be flexible to allow the segments to be inserted into the chosen treatment site. Suitable examples of fibers include those used as suture materials, biodegradable or not, e.g., polylactic acids, polyglycolic acids, mixtures and copolymers of polylactic and polyglycolic acids (PGLA such as "Vicryl" from Ethicon and "Dexon" from Davis & Geck), polydioxanone, various Nylons, polypropylene, silk, etc.). In this variation, the segments may comprise pellets with openings for stringing or be made adherent to a string, fiber or wire by means of manufacturing, glue, adhesive, or the like, or by simply placing the glue between the pellets. The wires may comprise one or more filaments comprising suitably biocompatible metals or alloys, e.g., stainless steels or superelastic alloys. [0019] The segments may be connected by placement within a flexible tube, variously a solid or continuous walled tube, a solid or continuous walled tube having openings in the wall, or a netting woven from string or fiber. The flexible tube may comprise one or more membranes, optionally an expandable or a stretchable material. Suitable materials include polymers, (e.g., polyfluorocarbons such as the various Teflons (including PTFE and expanded PTFE--ePTFE such as is sold as GORETEX), polypropylene, polyethylene, polyoxymethylene, polycarbonate, polyesters (including polyamides such as the Nylons), polyphenylene oxide, and polyurethane) or elastomeric polymers (e.g. various Silicones, natural rubber, butadiene-styrene rubber, carboxylic butadiene-styrene, butadiene-acrylonitrile rubber, carboxylic butadiene-acrylonitrile rubber, chlorobutadiene rubber, polybutadiene rubber, silicone rubbers, and acrylate rubbers, perhaps vulcanized, and other elastomeric materials) or a composite material. The expandable membrane may optionally be filled, for example with a fluent material or a bone cement, before or after the implant has been inserted into the bone cavity. The flexible tube may comprise a woven or non-woven material of non-synthetic materials (e.g. cotton, silk, and the like), polymers such as those listed above, and blends or mixtures of the previously mentioned materials. The segments may also be connected by a string, fiber, or wire in addition to the flexible tube. [0020] The segments may be connected by adhesives or glues, such as solvent- or catalyst-curable materials including silicone glues, rubbery epoxies, and adhesives suitable for the materials forming the segments. [0021] The segments of the implant may be severable, singly or in groups, such as by severing the connection between the segments. The implant may be severed remotely by a user. The implant may be severed mechanically, chemically, thermally, or electrically. The implant may be severed while inserting it into a non-soft tissue cavity or after the implant has been inserted into a cavity. In one version, the connection material connecting flexibly connected segments may be removed from one or more segments without severing the material. For example, when a flexible joining material connecting the segments is a fiber, the fiber may be removed from the flexibly connected segments (e.g. pellets) after they have been inserted. Continue reading... Full patent description for Method and apparatus for filling a cavity Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and apparatus for filling a cavity patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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