Abstract:
A percutaneous surgical tool comprises a cannula with an open slot at the distal end and a closed tip. A variety of articulated and solid tamps with different tip geometries are used to push bone aside to open up a void for filling. Bone pellets are rammed down the hollow interior, lumen, of the cannula by a tamper. A ramp inside the closed end causes the bone pellets to eject out to the side into a void to-be-filled. Variations in the shapes of the pellets and the ends of the tampers vary the orientations of the pellets as they are ejected through the end slot out from the cannula. One tamper with a sharp flat diagonal cut end can be twisted to push the rear end of the pellet harder sideways and out parallel to the cannula. Curved cannulas allow better access to all parts of the void to-be-filled.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to percutaneous surgical methods and devices to stabilize vertebra, and more particularly to surgical tools and bone pellets for packing voids inside damaged vertebrae. 
         [0003]    2. Description of Related Art 
         [0004]    Vertebral compression fractures (VCF&#39;s) secondary to osteoporosis can occur spontaneously or result from even minor trauma. When the thick block of bone at the front of the vertebra in the spine collapses, the spine can shorten and fall forward. The posterior muscles and ligaments try to counterbalance the bending, making the osteoporotic anterior spine subjected to even larger compressive stresses. Healing of untreated fractures in the deformed state can make the less than optimum biomechanics a permanent impediment in the sufferer&#39;s life. 
         [0005]    Bones and their surrounding structures will heal more rapidly and more normally if the damaged bone structures are reconstructively returned to their original shapes and positions and any voids in the bone filled with bone grafts or other suitable matrix materials. 
         [0006]    Conventional treatments for osteoporotic and pathologic vertebral fractures rely on the application of liquid acrylic glass (PMMA). Such treatments are minimally invasive, and introduce the reconstructive materials into fractured vertebra through small incisions using metal cannulated tools. But the liquid PMMA and other structural graft materials are hard to control with traditional methods. The liquid PMMA can leak into the surrounding areas before it hardens in the right places, and that invasion can cause problems later. Inserting solid materials seems preferable because solids are easier to control and do not flow or migrate on their own like liquids can. 
         [0007]    A great number of percutaneous tools and procedures have thus been developed to clean out damaged tissues, expand collapsed spaces with balloons and catheters, and to insert replacement materials like bone grafts, artificial disks, and medicines. One particular tool of interest inserts bone pellets into voids inside the vertebrae through a hollow tube or cannula. See, U.S. Pat. No. 7,238,209, issued Jul. 3, 2007, to Hiromi Matsuzaki, et al. 
         [0008]    Different shaped bone pellets can be used according to the nature and size of the bone voids to be filled and packed. Bone grafts provide a framework into which the host bone can regenerate and heal. Bone cells weave into and through the porous microstructure of the implant. The implants provide a framework to support new tissues and bone as they grow to reconnect the fractured segments. Bone cells and living cells inside the graft also stimulate growth of surrounding bone and tissue. 
         [0009]    Many bone graft extender materials are commercially available for other applications, and some could be put to good use if they could be appropriately and safely placed down within the vertebra. “PRO OSTEON IMPLANT-500” is one such artificial bone graft material, and it is made from marine coral exoskeletons. Its porous structure mimics the porosity of human cancellous bone. PRO OSTEON IMPLANT-500 facilitates the natural healing process without risking disease transmission, biological rejection, and the additional surgery necessary to collect donor bone for grafting. 
         [0010]    Such bone void fillers are clinically proven materials that have changed the way orthopedic surgeons do bone grafts. PRO OSTEON IMPLANT-500 is sterile, biocompatible, and can be easily molded to fill a defect in fractured bones. It is approved by the Food and Drug Administration (FDA) when used with rigid internal fixation for metaphyseal fracture defects, e.g., fractures at the ends of the long bones of the arms and legs. 
         [0011]    Balloon kyphoplasty inserts a balloon-like device, an inflatable bone tamp, into a channel drilled into a fractured vertebra. The tamp is positioned in the vertebral body and inflated to create a void for filling to restore the normal height of the vertebral body. The KyphX® Exact™ Inflatable Bone Tamp and the KyphX® Elevate™ Inflatable Bone Tamp are directional inflatable bone tamps (IBT&#39;s) marketed by Kyphon Inc. (Sunnyvale, Calif.) to provide targeted balloon inflation for fracture reduction and cavity creation during Balloon Kyphoplasty procedures. The KyphX Directional IBTs are compatible with the KyphX Osteo Introducer, KyphX Advanced Osteo Introducer and KyphX One-Step Osteo Introducer Systems. Directional balloons can be used for cavity creation and fracture reduction, depending on fracture morphologies, bone quality, and access channel trajectory. 
         [0012]    Closed-tip cannulas are well known. The Katena cannula K7-3016 (Katena Products, Inc, Denville, N.J.) is a 23-gauge cannula that features an end-opening slot for direct irrigation and a tapered tip for ease of entry into an undilated punctum. The 13-mm length makes it ideal to probe as well as irrigate the proximal lacrimal system. Katena cannula K7-3016 eliminates the need for punctal dilation and placement of Bowman probes to dilate the eye&#39;s punctum and measure canalicular obstruction, respectively. 
       SUMMARY OF THE INVENTION 
       [0013]    Briefly, a percutaneous surgical tool embodiment of the present invention comprises a cannula with an open slot at the distal end and a closed tip. A variety of articulated and solid tamps with different tip geometries are used to push bone aside to open up a void for filling. Bone pellets are rammed down the hollow interior, lumen, of the cannula by a tamper. A ramp inside the closed end causes the bone pellets to eject out to the side into a void to-be-filled. Sometimes the pellets are forcefully driven in by pounding on the tamps, much like a pile-driver operates. Variations in the shapes of the pellets and the ends of the tampers vary the orientations of the pellets as they are ejected through the end slot out from the cannula. One tamper with a sharp flat diagonal cut end can be twisted to push the rear end of the pellet harder sideways and out parallel to the cannula. Curved cannulas allow better access to all parts of the void to-be-filled. 
         [0014]    The above and still further objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, especially when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1A  is a perspective view diagram of a closed-tip cannula, a bone graft pellet, and a flat tipped tamp in an embodiment of the present invention in which the cannula is inserted into the interior of a vertebral body and many bone graft pellets are pushed in by pounding the tamp behind them; 
           [0016]      FIGS. 1B-1D  are perspective view diagrams of the closed-tip cannula of  FIG. 1A  and a wedge-tipped tamp that can be inserted, as in  FIG. 1C , and used to laterally push aside a bone graft pellet loaded in the slot at the end of the cannula by twisting the wedge tip, as in  FIG. 1C ; 
           [0017]      FIGS. 2A and 2B  are top and side, partial cross section views of a human vertebra showing how the cannula and tamps of  FIGS. 1A-1D  would be positioned for use during percutaneous surgery, and several bone graft pellets are shown having already been delivered to the interior of the vertebral body; 
           [0018]      FIG. 3  is a flowchart diagram of a method embodiment of the present invention that recites the typical steps involved in the percutaneous surgery of the vertebra shown in  FIGS. 2A and 2B , the guide needles and pins are used for open-tip cannulas and are not needed with the closed-tip cannulas of  FIGS. 1A-1D , and  2 A and  2 B; 
           [0019]      FIGS. 4A and 4B  are side cross section and top plan view diagrams of the tip of a closed-tip cannula embodiment of the present invention; 
           [0020]      FIGS. 5A and 5B  are side and top view diagrams of the distal end of a blunt nose flexible tamp embodiment of the present invention with leaf joints that can be used with the closed-tip cannula of  FIGS. 1A-1D ,  2 A- 2 B,  3 , and  4 A- 4 B, to pound bone graft pellets into the interior spaces of the vertebral body of  FIGS. 2A and 2B ; 
           [0021]      FIGS. 6A and 6B  are side and top view diagrams of the distal end of a blunt nose articulated tamp embodiment of the present invention with a single spring linked joint that can be used with the closed-tip cannula of  FIGS. 1A-1D ,  2 A- 2 B,  3 , and  4 A- 4 B, to pound bone graft pellets into the interior spaces of the vertebral body of  FIGS. 2A and 2B ; 
           [0022]      FIGS. 7A and 7B  are side and top view diagrams of the distal end of a blunt nose articulated tamp embodiment of the present invention with three linked joint that can be used with the closed-tip cannula of  FIGS. 1A-1D ,  2 A- 2 B,  3 , and  4 A- 4 B, to pound bone graft pellets into the interior spaces of the vertebral body of  FIGS. 2A and 2B ; 
           [0023]      FIG. 8  is a side view diagram of a variety of bone graft pellets useful in various embodiments of the present invention; 
           [0024]      FIG. 9  is an enlarged perspective view diagram of the distal end of a closed-tip cannula embodiment of the present invention as shown in  FIGS. 1A-1D ,  2 A- 2 B,  3 , and  4 A- 4 B; 
           [0025]      FIGS. 10A-10C  are cutaway side view diagrams of the distal end of a closed-tip cannula embodiment of the present invention showing how a tamp like that of  FIGS. 5A-5B  articulates on its leaf joints as it is pushed forward, and showing how it can be directed to push bone graft pellets and soft interior bone sideways while within a vertebral body; 
           [0026]      FIG. 11A  is a cutaway side view diagrams of the distal end of a closed-tip cannula embodiment of the present invention showing how a tamp like that of  FIGS. 7A-7B  articulates on its three link joints as it is pushed forward, and showing how it can be directed and pounded to push bone graft pellets and soft interior bone sideways while within a vertebral body; and 
           [0027]      FIG. 11B  is a cutaway side view diagrams of the distal end of an open-tip cannula with an oblique end, in another embodiment of the present invention; and 
           [0028]      FIGS. 12A-12D  are a sequence of diagrams showing how an orderly build up of bone graft sections inside the void of a vertebral body during percutaneous surgery can be assisted by the oblique faces of the grafts and tools used. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Percutaneous access to a vertebral body is an established and medically accepted procedure for treating a variety of conditions. Kyphon brand balloon tamps are probably the most widely used instruments. An alternative is vertebroplasty, in which simple injections of liquid or paste bone cements are pumped down a large caliber needle into the cancelous part of weakened or fractured vertebrae. The most common bone cement is probably polymethylmethacrylate (PMMA). 
         [0030]    In embodiments of the present invention, commercially available solid pellets of substitute bone are placed as grafts into to the cancelous parts of weakened or fractured vertebrae with cannulas impaction tools. A variety of lengths and shapes are selected that will best fill the voids using impaction grafting. Filling the voids this way can also re-expand and restore the vertebral body to a more normal configuration. 
         [0031]    The key to success is to use both the appropriate impaction tools and graft bone pellets with the optimum sizes, lengths, diameters, and mechanical properties. Simple autogenous or allograft bone would not suffice. Using containment meshes has also proven to be too costly and difficult for wide acceptance. 
         [0032]      FIGS. 1A-1D  represents closed-tip cannulas, bone graft pellets, and tamps included in a system embodiment of the present invention, and are referred to herein by the general reference numeral  100 . System  100  includes a cannula  102  with a side slot  104  and closed tip  106  on its distal end. A handle  108  provides some leverage to twist the cannula  102  to best position side slot  104 . Cannula  102  is typically inserted into the interior of a vertebral body during percutaneous surgery. A loading  110  of a bone graft pellet  112  is followed by a tamp  114  with an anvil  116  and a flat nose  117 . Many bone graft pellets  112  of various sizes and shapes can be pushed into the interior of a vertebral body by ramming the tamp  114  behind them. 
         [0033]      FIGS. 1B-1D  show how loading  118  a tamp  120  with a handle  122  and a wedge tip  124  can be used after bone graft pellet  112  is readied. Twisting handle  122  will laterally eject bone graft pellet  112  from slot  104 , as in  FIG. 1D . The action is similar to the ejecting of a spent cartridge from the slot of a rifle. 
         [0034]    Handles  108  and  122  also serve as stops to prevent over-penetration of the tools into the surgical site. 
         [0035]      FIGS. 2A and 2B  illustrate a method in which a cannula  202  from the left and a cannula  204  from the right are inserted through holes drilled through pedicles  206  and  208  into the vertebral body  210  of a vertebra  212  for use during percutaneous surgery. As an example, cannula  202  is shown as a curved type. A straight one could also be used. Several bone graft pellets  214 ,  216 , and  218  are shown already having already been delivered to the interior of the vertebral body through slots  220  and  222  in cannulas  202  and  204 . Here, a tamp  224  has been used to ram down the pellets through the cannulas. A wedge-tipped rod  226  could also be inserted and twisted to expel each pellet. 
         [0036]      FIG. 3  represents a percutaneous bone graft method embodiment of the present invention, and is referred to herein by the general reference numeral  300 . In a step  302 , the patient is positioned for access to a damaged vertebral body. In a step  304 , two access sites are identified with fluoroscopic guidance and anesthetized. If open-tipped cannulas are being used, guide needles and pins are inserted through incisions down to the vertebra in a step  306 . Fluoroscopic guidance is used in a step  308  to advance the guide pins through a pedicle or lateral portion of the vertebra to the center or anterior portion of a fractured vertebra. In a step  310 , a cannula is advanced over the guide pins to the posterior portion of the vertebra. Then the guide pins can be removed. 
         [0037]    In a step  312 , blunt tamps are pushed through the cannula into the vertebral body to force soft bone aside. In a step  314 , tamps with flexible joints are used to further push aside more bone inside the vertebral body. A step  316  fills the voids created by the tamps with pre-shaped grafts of bone substitute material having predetermined lengths and diameters. In a step  318 , blunt-tapered bone impaction tools are used to push solid bone grafts out sideways from a slot on the end of a closed-tip cannula. In a step  320 , beveled ended impactors or tamps are used to angle the bone grafts to better fill the voids. A step  322  uses progressive impaction. A step  324  includes progressively shifting the graft direction. A step  326  injects liquid or paste filler material if needed to complete the procedure. 
         [0038]    In another embodiment of the present invention, access is made to the vertebral body through standard percutaneous fluoroscopically guided techniques with needles and hollow cannulae. Bone grafts and augment devices are impacted with cannulated tools with a circular impactor. Various nose shapes on the impaction tools provide for lateral displacement. For example, oblique flat faces on the noses and tails of the bone grafts and tools help stack the pieces side by side inside the voids. 
         [0039]    Referring to  FIG. 3 , a similar method of percutaneous surgical repair of a damaged vertebral body comprises placing a cannula or dilating obturator and then a cylindrical cannula over a guide pin. The cannula may have an oblique side, as in  FIG. 11A , to allow translation of grafts in controlled directions. Each graft is placed by impaction with a tamp. A tapered oblique tool can be used to push or tap behind the graft using a mallet. The grafts can be directed to one side by virtue of the oblique end on the cannula. The tamp is rotated periodically to help fill grafts in all around, advancing a full cylinder tamp or spring tool to push each graft section in further. The progressive build up will combine to support a fractured vertebra with grafts to help expand and reshape a crushed structure. 
         [0040]      FIGS. 4A and 4B  represent a closed-tip cannula embodiment of the present invention, referred to herein by the general reference numeral  400 . Cannula  400  includes a hollow interior lumen  402  that terminates at the distal end with a side slot  404  in the shape of a slot. A ramp  406  helps materials pushing down inside lumen  402  to be redirected out to the side from side slot  404 . Cannula  400  can be straight or curved, e.g., to allow better access to portions of the interior of a vertebral body through a single incision. 
         [0041]      FIGS. 5A and 5B  represent the distal end of a blunt nose flexible tamp embodiment of the present invention, referred to herein by the general reference numeral  500 . Tamp  500  has one or more leaf joints  501 - 503  that can be used with a closed-tip cannula to pound bone graft pellets into the interior spaces of a vertebral body, such as in  FIGS. 2A and 2B . A nose  504  can have a variety of useful shapes.  FIGS. 5A and 5B  show a blunt nose, but pointed, rounded, concave, and wedge shaped noses all have important applications. Tamp  500  is made of metals or plastics that are strong enough to survive being pounded, and that are biocompatible. 
         [0042]      FIGS. 6A and 6B  represent the distal end of a blunt nose flexible tamp embodiment of the present invention, referred to herein by the general reference numeral  600 . Tamp  600  has one or more link joints  601  that can be used with a closed-tip cannula like cannula  400  in  FIGS. 4A and 4B  to pound bone graft pellets into the interior spaces of a vertebral body as in  FIGS. 2A and 2B . The distal end can thus flex in two opposite directions. A nose  602  can have a variety of useful shapes.  FIGS. 6A and 6B  show a blunt nose, but pointed, rounded, concave, and wedge shaped noses all have important applications. Tamp  600  is made of metals or plastics that are strong enough to survive being pounded, and that are biocompatible. 
         [0043]      FIGS. 7A and 7B  represent the distal end of a multi-link blunt nose flexible tamp embodiment of the present invention, referred to herein by the general reference numeral  700 . Tamp  700  has two or more link joints  701 - 703  that can be used with a closed-tip cannula like cannula  400  in  FIGS. 4A and 4B  to pound bone graft pellets into the interior spaces of a vertebral body as in  FIGS. 2A and 2B . Here, links  701  are orthogonal in action to links  702 , permitting flexing of the distal end in two orthogonal directions. A nose  704  can have a variety of useful shapes.  FIGS. 7A and 7B  show a blunt nose, but pointed, rounded, concave, and wedge shaped noses all have important applications. Tamp  700  is made of metals or plastics that are strong enough to survive being pounded, and that are biocompatible. 
         [0044]      FIG. 8  is a side view diagram of a variety of bone graft pellets useful in various embodiments of the present invention. For example, a pellet  801  is made of a solid material similar to “PRO OSTEON IMPLANT-500”, and has a simple cylindrical shape sized to slide down inside lumen  402  of cannula  400  and slot sideways out of  404  ( FIGS. 4A and 4B ). A pellet  802  is a flat faced round wedge, and a pellet  803  is a solid cylinder with oblique opposite faces  804  and  805 . A pellet  806  is similar but longer in length. A pellet  808  is bullet shaped with a convex nose  809  and a concave tail  810 . The various shapes and lengths can interlock and help self-assemble a mass of these pellets into a framework within a void in a vertebral body. 
         [0045]      FIG. 9  represents the distal end  900  of a closed-tip cannula embodiment of the present invention, such as in  FIGS. 1A-1D ,  2 A- 2 B,  3 , and  4 A- 4 B. A hollow cylinder  901  runs the full length and allows guide wires, tools, and bone grafts to be passed through. A bone graft pellet  902  is shown ready to be ejected from a slot  904  in the side. An inclined ramp  906  is situated to help with the sideways ejection of pellet  902 . A small concentric hole  907  through a closed tip  908  is provided for guide wires that help with the initial positioning of cannula  900 . A typical diameter for hole  907  is 0.7-1.0 millimeters in a tip  908  that is 4.5-5.0 millimeters in diameter. Closed tip  908  is shaped to make insertion into a small incision simple and easy by having a blunt tip that pushes tissues aside as it penetrates. Cannula  900  is made of metals or plastics that are strong enough to survive being pounded and twisted against bone, and that are biocompatible. For example, stainless steel. A material is biocompatible if it allows the body to function without allergic reactions, complications, or other adverse side effects. 
         [0046]      FIGS. 10A-10C  represent the distal end of a closed-tip cannula  1000  and a tamp  1002 , like those of  FIGS. 4A-4B  and  5 A- 5 B. Tamp  1002  articulates on its leaf joints  1004 - 1006  as it is pushed forward. Its nose  1008  slides up a ramp  1010  and out, as shown in  FIGS. 10B and 10C . The tamp  1002  can be directed to push bone graft pellets and soft interior bone sideways while within a vertebral body. How far the tamps can be pushed through the cannulas is limited. 
         [0047]      FIG. 11A  represents the distal end of another closed-tip cannula  1100  and a tamp  1102 , like that of  FIGS. 7A-7B , articulates on its three link joints  1104 - 1106  as it is pushed forward. It too can be directed and pounded to push bone graft pellets and soft interior bone sideways while within a vertebral body. Its nose  1108  slides up a ramp  1110  and out. 
         [0048]    Variety in the lengths, shapes, and diameters of the bone graft solids are important to the practical application of embodiments of the present invention. Extrusions of plasticized replacement bone matrix could also be forced down large diameter cannulas in sectional lengths using tamps as pistons. Bone tamps with articulated ends and noses with different shapes help make the job of creating a suitable void less difficult and produce better results. The materials used in these tamps are bio-safe metals and plastics, so as not to pose a danger if pieces are inadvertently or accidently left behind. 
         [0049]    If any injectable liquid or paste bone cements are used to finish up, the volume of solid bone pellet material impacted into the voids very much reduces or eliminates how much bone cement will really be needed to complete the procedure. Thus safety is inherently improved. 
         [0050]      FIG. 11B  represents the distal end of an open-tip cannula  1120  with an oblique end  1122 , in another embodiment of the present invention. Tamp  1102  articulates on its three link joints  1104 - 1106  as it is pushed forward. It can be directed and pounded to push bone graft pellets and soft interior bone while within a vertebral body. 
         [0051]      FIGS. 12A-12D  show an open-tip cannula  1200  in situ during use and how it can be used to deliver stacks of bone graft sections  1201 - 1207 . Each has an oblique, tilted face that will kick-off to one side when each bone graft section  1201 - 1207  exits the end of cannula  1200 . A tamp  120  like that illustrated in  FIG. 1B  could be used to control which radial direction the bone graft sections  1201 - 1207  build up. Differently faced bone graft sections  1201 - 1207  and tamps will produce other kinds of stacking actions. Tamps  400 ,  500 ,  600 , and  700  shown in  FIGS. 4A ,  4 B,  5 A,  5 B,  6 A,  6 B,  7 A, and  7 B, could be used effectively as well. 
         [0052]    In one tools technique sequence, a cannula or dilating obdurate and then a cylindrical cannula is placed over a guide pin. The cannula may have an oblique side to allow translation of grafts in controlled directions. Each graft is placed or impacted by pounding. A tapered oblique tool is pushed or tapped in behind with a mallet. After partially translating the graft, the tamp is rotated to translate the section further. A full cylinder translating tamp or spring tool is advanced to push the graft sections in further. For example, tools  500 ,  600 , and  700 , with wedge or conical point noses. A second device is placed and moved side to side and up and down to progressively build up and support the fractured vertebra. Such can also expand and reshape a crushed structure. 
         [0053]    The solid bone grafts of the present invention can further be round, hexagonal, or octagonal in lateral cross section. 
         [0054]    Although particular embodiments of the present invention have been described and illustrated related to vertebrae, such is not intended to limit the invention. The treatment of other fractured and weakened bones in the rest of the body is also included. Modifications and changes will no doubt become apparent to those skilled in the art, and it is intended that the invention only be limited by the scope of the appended claims.