Abstract:
An instrument for filling cavities in a body, such as a cavity within a reamed out spinal disc, with beads includes a cyclical agitator that functions to prompt the introduction of one bead at a time through the fill tube to prevent clogging and to promote compaction within the cavity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not Applicable  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to a medical instrument for filling a cavity formed within bone, a spinal disk, or a fixation device inserted therein, with biocompatible beads. More specifically, the present invention is directed to a vibratory tool having a reservoir of biocompatible material in fluid communication with a proximal end of a tubular injection cylinder, the injection cylinder and reservoir are vibrated to cause the material to pass from the reservoir into the proximal end of the injection cylinder. The vibratory action of the device and gravity allow the material to pass through the injection cylinder to its distal end and be deposited into a delivery site. The vibratory action of the injection cylinder causes the distal end of the cylinder to gently tap the deposited material thereby compacting the material within the delivery site. The unique construction and vibratory action of the present device prevents fill material from plugging the device during use and provides for a consistent flow of fill material into the delivery site.  
           [0004]    2. Description of the Related Art  
           [0005]    Bioceramic compounds and other types of fill material such as bone may be used as a fill material in the treatment of certain orthopaedic conditions; including fractures, non-unions, tumors, and cysts and as an adjunct to certain fusion procedures. In general, these conditions involve filling a cavity that has been created by the pathology itself or by the action of the surgeon during removal of the pathology.  
           [0006]    The cavity may be filled by the placement of a block of fill material or by the gradual addition of granules of fill material such as bioceramic beads, crushed bone or a combination thereof. Alternatively, a variety of different types of support and/or joining devices may be inserted into the cavity. These devices may be filled with the fill or graft material, as opposed to directly filing the cavity therewith.  
           [0007]    Devices such as those used in spinal fixation are well known in the art. Such devices may include apparatuses which are inserted into hollowed out portions of a spinal disk or vertebrae. For example, U.S. Pat. No. 5,549,679 issued Aug. 20, 1996 and U.S. Pat. No. 5,571,189 which issued Nov. 5, 1996, both of which being incorporated in their entirety herein by reference, disclose an expandable fabric bag and method for stabilizing a spinal motion segment. In these patents, a damaged disc is reamed out and an expandable fabric bag is inserted into the cavity thus formed. Bone graft material is then inserted into the bag to fill and expand the bag such that the filled bag will take the place of the reamed out disc. Over time, the material within the bag will cause a fusion of the adjacent vertebrae. The bag filling is through an opening which is closed off after filling.  
           [0008]    Another device and method for stabilizing a spinal motion segment is described in co-pending U.S. Provisional App. No. 60/256,014 filed Dec. 15, 2000, the entire contents of which being incorporated herein by reference. In this Application a band of fabric or mesh is inserted into a reamed out cavity within a disk or other spinal body. The fabric of the band may be structured to allow a bone graft fill tool to penetrate the band, without causing it damage, and deposit fill material into the area defined by the band and surrounding tissue.  
           [0009]    These and other devices are intended to provide support to the spinal segment which they are being inserted into and to encourage fusion of the surrounding spinal bodies through the device. A key aspect to such devices is the proper placement and compaction of bone graft material into the site through which bone growth and eventual fusion is to take place.  
           [0010]    As indicated above the cavity or device may be filled with material in a variety of different manners. Manual filling such as by insertion by hand of one or more chunks of fill material may not provide for ideal filling and compaction characteristics which may be essential to encouraging proper bone growth and fusion. The use of granular material in gradually filling the cavity, or a device inserted therein has the advantage of allowing filling through a smaller entrance portal. In addition, by gradually filling the cavity or device with granular fill material allows the cavity to be filled in a more uniform and complete manner.  
           [0011]    In use however, granular material such as ceramic granules tend to jam within injection tubes and tend to break apart and pulverize when injection and/or impaction forces are vigorously applied. Broken or pulverized granules of bioceramic compounds contain fine dust particles that have been shown to inhibit bone growth.  
           [0012]    The granules may exist in a variety of shapes and sizes, such as, for example amorphous chunks or solid geometric shapes. Of the various available granule shapes, spherical shaped beads provide several potential advantages over other granular shapes. Notably, spherical beads may provide maximal and consistent inter-granule porosity and improved flowability. However, even spherical granules are known to jam and break apart during the injection procedure. Therefore, there is a need for a new method of granule injection that is easier, faster, and produces less jamming and granule breakage.  
           [0013]    Experiments have been conducted with various means to more efficiently and effectively introduce granular material into cavities. The goal of these experiments was to develop a novel means for improving spherical granule flow while minimizing the breakage of granules. As a result of these experiments the device of the present invention was constructed. The present device was determined to provide the best combination of flow efficiency and the least tendency toward granule breakage during the fill process. By utilizing the present invention for inserting bioceramic beads or other fill material into a body cavity, the invention may improve the care of patients with certain orthopaedic conditions.  
           [0014]    The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists.  
           [0015]    The entire content of all of the patents listed within the present patent application are incorporated herein by reference.  
         BRIEF SUMMARY OF THE INVENTION  
         [0016]    In light of the above, the present invention is directed to a method and apparatus which provides for improved filling and compaction of bone graft material within a hollowed portion of a bone, spinal segment or a fixation device positioned therein.  
           [0017]    In at least one embodiment, the present invention is directed to a filling instrument that directs one granule or bead to drop into a tube from a bead reservoir, upon dropping a bead into the tube, the tube and reservoir are pneumatically actuated to pop back up to unblock the granules therein, which in turn allows another bead or granule to drop into the tube in repeating cycles. The present device agitates the granules at each stroke so they fill up the tube. The up and down motion of the tube and reservoir also provides for compaction of the beads at the distal end of the tube which may compact the beads into the chamber or spinal fixation device being filled.  
           [0018]    The present invention allows the surgeon to fill body cavities more easily and completely, with less damage to granules, and through a very small entrance portal. The invention also provides a means to compact the granular mass, thereby improving the fill density and the stability of the granular pack.  
           [0019]    The invention provides for a bead reservoir that is submitted to vibratory energy that encourages the bead pack to flow into a hollow, tubular injection cylinder. Pneumatic, hydraulic, or other mechanical forces then cause the injection cylinder to oscillate along its longitudinal axis, while the beads are gently pushed into the cavity by a combination of frictional forces against the cylinder walls and the pull of gravity.  
           [0020]    Once the cavity is filled or nearly filled, the distal tip of the oscillating cavity gently taps the top of the bead pack, thereby forcing the beads into a more densely packed construct.  
           [0021]    As indicated above, one application of the invention is in the field of spinal surgery. Surgeons often attempt to fill certain spaces within the spine with bone or bone substitute materials, such as bioceramic material. The filled spaces then provide mechanical support and the proper milieu for bone ingrowth. The local spinal anatomy restricts safe access to certain internal spinal areas. Therefore, surgeons are often required to operate through very small entry portals. The present invention provides the surgeon with a reliable and effective device suitable for filling cavities deep within the spine, e.g. the interbody or intra-vertebral spaces.  
           [0022]    One particularly common spinal procedure is known as an interbody fusion. In the interbody fusion procedure, the surgeon attempts to fill the gap between two opposing vertebrae with a material and/or device that supports load and encourages bony ingrowth. Such devices include, but are not limited to, those described in U.S. Pat. Nos. 5,489,308; 5,549,679; 5,571,189 and others.  
           [0023]    As shall be made clear from the description below, in at least one embodiment of the invention, the present device may be inserted through very small diameter tubes. As a result, it is possible to fill the intervertebral space with little or no retraction of sensitive local nerves and vessels. For example, this invention allows the surgeon to fill the interbody space through a portal substantially smaller than currently required for many procedures.  
           [0024]    Another area where the present invention may be of use would be in procedures known as vertebra-plasties or kypho-plasties, wherein the surgeon attempts to fill the area occupied by a so-called “compression fracture” of the vertebral body. The present invention could be used to fill this area through the narrow confines of the vertebral pedicle or through a small (about 3-10 mm) hole in the side or front of the vertebral body. As a result, use of the invention would reasonably reduce risk and complications compared to other procedures that require a larger exposure, as in the case of the placement of large bioceramic blocks. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0025]    A detailed description of the invention is hereafter described with specific reference being made to the drawings in which:  
         [0026]    [0026]FIG. 1 is a perspective view of an embodiment of the invention;  
         [0027]    [0027]FIG. 2 is a longitudinal sectional view of the embodiment of the invention shown in FIG. 1;  
         [0028]    [0028]FIG. 3 is an enlarged view of the angled opening slot joining the reservoir and the injection cylinder of the embodiment of the invention shown in FIG. 1;  
         [0029]    [0029]FIG. 4 is a perspective view of an embodiment of the invention as shown in its intended environment of use;  
         [0030]    [0030]FIG. 5 is a perspective view of an embodiment of the invention as shown in its intended environment of use;  
         [0031]    [0031]FIG. 6 is an exploded view of an embodiment of the invention;  
         [0032]    [0032]FIG. 7 is a detailed sectional view of portions of the housing of an embodiment of the invention; and  
         [0033]    [0033]FIG. 8 is a block diagram illustrating the use of an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    With reference to the FIGS.  1 - 8  wherein identical elements are numbered identically throughout, an embodiment of the inventive filler instrument, indicated generally at  10 , is shown. In the embodiment shown, the filler instrument  10 , has three primary portions: a central housing  12 , a tubular injection cylinder or needle  14  and a reservoir  16 .  
         [0035]    As is shown in FIG. 2, the needle  14  defines a hollow needle chamber or passage  20  which includes a proximal opening  22  at proximal end  26  and a distal opening  24  at distal end  28 . The needle chamber  20  has a diameter sufficient to allow passage of a bioceramic bead or other particle of material  40  to pass therethrough in a single-file line or individually.  
         [0036]    Typically, the needle passage  20  and openings  22  and  24  will be approximately 0.5 mm to 5 mm in diameter The proximal opening  22  of needle  14  is in fluid communication with the reservoir  16 . The reservoir may contain the fill material  40  such as bioceramic beads or other materials. The individual particles of material  40  are sized to be able to enter the proximal opening on a one-at-a-time basis and pass through the passage  20  in a single file line when the device  10  is activated.  
         [0037]    The central housing  12 , defines a central passage or chamber  18  (as may best be seen in FIG. 6) through which the needle  14  may travel longitudinally therein. The proximal end  26  extends proximally beyond the housing  12  and passage  18  and is engaged to the reservoir  16 . The reservoir  16  is defined by a reservoir housing  32 , The reservoir housing  32  is engaged to the proximal end  26  of the needle  14  by a mounting collar  30 . The mounting collar  30  employs one or more fastening members  34  to retain the proximal end  26  of the needle  14  therein. The fastening members  34  may be any type of fastener such as a screw, bolt, clip, etc. The mounting collar  30  may be engaged to the reservoir housing  32  by any of a variety of mechanisms. For example: the collar  30  and reservoir housing  32  may be opposingly threaded to allow the collar to be screwed into the reservoir housing  32 , the collar  30  may be sized to fittingly engage the reservoir housing  32 , the collar  30  may snap-fit into the reservoir housing, etc.  
         [0038]    As may best be seen in FIG. 3, the collar  30  includes an angled opening slot  42 . The slot  42  is designed to allow beads to pass into the proximal opening  22  of the needle chamber  20  on a one-at-a-time basis such as is depicted in FIGS. 2 and 4. The unique configuration of the opening slot  42  helps to prevent beads or other fill material from blocking the proximal opening  22  as well as prevent multiple beads or particles from plugging the needle chamber  20 . In addition, by providing a slot  42  which regulates bead flow into the needle chamber  20 , the present device provides a user with a significant degree of control for placement of the beads in a delivery site, such as is illustrated in FIGS.  4 - 5 .  
         [0039]    Returning to FIG. 2, the reservoir housing  32  defines a reservoir chamber  36  which may be filled in-whole or in-part by a predetermined number or volume of fill material  40 . The reservoir housing  32  may be at least partially transparent to allow a user to see the material  40  within the reservoir chamber  36 . The reservoir housing  32  may also include volume indicators or markings so that the volume of material  40  remaining within the chamber  36  may be readily determined at any time.  
         [0040]    As indicated above, the fill material  40  may be comprised of bone graft material, bioceramic beads, crushed bone, and/or other types of biocompatible fill material. The reservoir housing also includes a reservoir plug or seal  38  which may be readily removed from the reservoir housing  32  to allow the fill material  40  to be inserted therein, and may be engaged to the reservoir housing  32  to prevent spillage of the fill material  40  therefrom. When secured to the reservoir housing  32 , the seal  38  also acts to prevent the introduction of contaminants into the reservoir housing  32 .  
         [0041]    The needle  14  extends from the reservoir  16  into the passage  18  of the central housing  12 . Prior to entering the passage  18 , the needle  14  passes through a proximal valve assembly  50 , which provides a sliding valve seal  55  between the needle  14  and central housing  12 . The proximal valve assembly may comprise a nut, ring or other type of retaining member  52  which is secured to a proximal valve receiving member  54  of the housing  12 . The retaining member  52  and receiving member  54  may be reversibly threaded to allow the retaining member  52  to be threaded onto the receiving member  54 , or they may be otherwise constructed to provide removable engagement therebetween.  
         [0042]    The retaining member  52  includes an inner radial lip  58  which defines an opening through which needle  14  is passed. The radial lip  58  provides a surface upon which an o-ring  56  may be positioned. When the retaining member  52  is screwed or otherwise fastened on to the receiving member  54 , the o-ring  56  is sandwiched between the radial lip  58  and the receiving member  54 , there by providing a first or proximal sliding valve seal  55  between the housing  12  and the needle  14 .  
         [0043]    As is best shown in FIG. 2, the proximal seal assembly  50  defines the proximal end of a piston chamber  60 . The piston chamber includes a fluid entrance port  62  which is connected to a fluid line  64  and source  44  shown in FIG. 8. The fluid source may be hydraulic, pneumatic, or any other means for providing liquid or air based pressure into the chamber  60 . Turning to the close-up view shown in FIG. 7, the piston chamber  60  includes a piston member  66  which extends outward from the needle  14  to the inner wall  68  of the chamber  60 . The piston member  66  may be integral with the needle  14  or may be a separate apparatus through which the needle  14  is passed through and sealed therein.  
         [0044]    The piston member  66  includes a groove or notch  70  about its circumference  72 . The notch  70  provides a space in which a piston o-ring  74  is placed. The piston o-ring  74  extends beyond the piston member  66  to contact the wall  68 . The presence of the piston o-ring  74  between the piston member  66  and the wall  68 , effectively provides a second or distal sliding valve seal  75  between the needle  14  and the housing  12 .  
         [0045]    Referring to FIG. 7, when a fluid is injected into the piston chamber  60  from fluid line  64 , fluid pressure will build within the chamber and press against the piston member  66 . The arrangement of the first and second sliding seals  55  and  75  respectively allow the building pressure to move the piston member  66 , and thus the needle  14 , longitudinally in the distal direction. The distal movement of the piston member  66  and needle  14  is limited by the presence of a break or stop  78 . The stop  78  shall be discussed in greater detail below.  
         [0046]    Below the piston chamber  60 , the housing  12  defines a biasing chamber  80 . The biasing chamber  80  contains a biasing member or return spring  82  which is biased against the piston member  66  and a distal retaining collar  84 . As may best be seen in FIG. 6, the distal retaining collar  84  may include one or more retaining projections  88  which project outwardly therefrom. The retaining projections  88  are received into a corresponding number of receiving channels  86  positioned in the housing  12 , as is shown in FIG. 1. The arrangement of retaining projections  88  and receiving channels  86  provides the device  10  with the capacity to readily remove the retaining collar  84  thereby providing access to the various components discussed above contained within the housing  12 . Alternatively, any variety of affixing means may be used to removably engage the distal retaining collar  84  to the housing  12 . Such means may include, but are not limited to, screws and appropriately positioned holes, snap fit engagement of the collar  84  and housing  12 , respectively reversed threads to allow the collar  84  to be threadingly received into the housing  12 , etc.  
         [0047]    As indicated above, the distal retaining collar  84  includes a proximally extending stop  78 , shown in FIG. 6. The stop  78  is constructed and arranged to limit the distance the piston member  66  can move when subjected to fluid pressure as discussed.  
         [0048]    The area between the distal retaining collar  84  and the piston member  66  defines the biasing chamber  80 . When the piston member  66  is moved distally as a result of fluid pressure in the piston chamber  60 , the biasing member  82  is compressed. After the biasing member  82  has moved to its full extent and is stopped by stop  78 , the fluid pressure will continue to build until it is sufficient to break the seal of valve seals  55  and/or  75 , thereby momentarily releasing the built up fluid pressure within the piston chamber  60 . When the pressure is released in this manner, the biasing member  82  has sufficient force to push the piston member  66  proximally to its original at rest position or until fluid pressure is sufficient to once again overcome the biasing force supplied to the piston member  66  from the biasing member  82 , subsequent to which the piston will again begin moving distally to repeat the cycle.  
         [0049]    In order to allow for any compression of the biasing member  82 , the wall  68  of the housing  12  includes a vent hole  90  which allows air to travel out of the biasing chamber  80  during compression of the biasing member  82  and back therein during its expansion.  
         [0050]    The injection of fluid into the piston chamber  60  coupled with the resistance provided by biasing member  82 , provides the device  10  with a needle  14  and reservoir  16  which moves in a longitudinally reciprocating motion relative to the housing  12 . Such reciprocating motion is indicated by arrows  46  in FIG. 4  
         [0051]    The movement of the needle and reservoir may be varied depending on the rate which fluid is injected into the chamber  60 . The rate may be selectively controlled by a pressure switch, toggle, button, knob, lever, or other controller device  48  connected to the device  10  and/or fluid source  44 , such as is illustrated in FIG. 8. Preferably, the controller  48  is a foot pedal which is operatively engaged to the fluid source  44  or line  64 .  
         [0052]    As may be seen in FIG. 2, reciprocation of the needle  14  and reservoir  16  functions, in-part, to vibrate or agitate the reservoir  16  and the fill material  40  located therein. The vibration of the reservoir  16  ensures that only individual particles of fill material  40  are accepted into the slot  42  and eventually the needle chamber  20 . If multiple particles somehow manage to enter the slot  42  simultaneously, or the slot  42 , and/or needle chamber  20  become jammed with particles of fill material  40 , the vibration of the reservoir  16  and needle  14  is sufficient to dislodge the particles and/or blockage.  
         [0053]    The vibratory action of needle  14  and reservoir  16 , when coupled with gravity ensures that the individual fill particles  40  which enter the needle chamber  20  will travel through its length to be deposited at the deposit site  96  as shown in FIGS. 4 and 5.  
         [0054]    In addition to providing a vibratory action to the reservoir  16  and needle  14 , the cyclic movement of the device  10  also provides the distal end of the needle  14  with a controlled tapping action which when applied to deposited fill material  40  compacts the fill material  40  without breaking or otherwise degrading the particles. As a result the fill material can be deposited loosely or extremely tight within the deposit site as desired.  
         [0055]    In order to ensure that the hollow needle  14  does not enter into the operation site to an undesired depth, an adjustable depth guide  92  may be disposed about the needle  14 , such as is shown in FIG. 5. The depth guide  92  is effectively a hollow tube or sheath through which the needle  14  passes. In the embodiment shown, the needle  14  does not contact the depth guide  92 . However, the depth guide  92  may be in intermittent or constant contact with the needle  14 . If the device is constructed in such a manner that the depth guide  92  and needle  14  may be in contact with one another, or are in contact with one another, a biocompatible lubricant may be applied to the internal surface of the depth guide  92  to ensure minimalization of friction created by the contact between the moving needle  14  and depth guide  92 .  
         [0056]    As may be seen in FIG. 5, depth guide  92  may be adjustable to provide the operating surgeon or technician with the ability to set the length of the needle  14  which may enter into the operating site  96  during reciprocation of the needle  14 . In the embodiment shown, the proximal end  98  of the depth guide  92  is threadingly engaged to the distal retaining collar  84  or other portion of the housing  12 . By rotating the depth guide  92  about the threads  94 , the depth guide  92  may be extended or retracted relative to the needle  14 . Alternatively, the depth guide  92  may be slidingly or otherwise adjustably engaged to the housing  12  or a portion thereof.  
         [0057]    At the distal end  102  of depth guide  92  there may be a contact member  100  which is sized to engage the opening or area of tissue adjacent to the opening of the operation site  96 . The contact member may be integral with the depth guide  92  or may be permanently or removably attached thereto by a snap-fit, threading, sliding, or any other suitable attachment means or methods. Contact member  100  may be constructed from any material suitable for use in a surgical device. It is preferable however, that contact member  100  be constructed from one or more material which may have vibration absorbing properties such as rubber, silicon or other vibration dampening materials. In addition to contact member  100 , sheath  92  as well as other portions of device  10  may include, or be constructed at least partially from vibration absorbing materials.  
         [0058]    The shape and size of the contact member  100  are such that the contact member may be placed against and supported by the tissue surrounding the opening of the operation site  96 . When placed about the operation site  96  in such a manner, the contact member  100  provides a stable point of reference which the operating surgeon may use to determine, adjust and set the depth, or potential depth, of the needle  14  into the operating site  96 .  
         [0059]    By providing the device  10  with a depth gauge  92  and contact member  100 , the depth of the needle  14  into the operation site  96  may be established with accuracy. As a result, the tapping and compacting action of the reciprocating needle  14  against the fill material  40  may be precisely controlled. Such control will allow an operator to control or avoid inadvertent fracture or other potential damage to the particles of fill material  40 . In addition, inadvertent contact with the tissue of the operating site  96  may also be reduced.  
         [0060]    In addition to being directed to the specific combinations of features claimed below, the invention is also directed to embodiments having other combinations of the dependent features claimed below and other combinations of the features described above. The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.  
         [0061]    Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below (e.g. claim 3 may be taken as alternatively dependent from claim 2; claim 5 may be taken as alternatively dependent on claim 3; etc.).