Abstract:
A shaper for reaming tissue includes an articulating head operably connected to a shaft. Incremental deployment allows for a unique utility in shaping a cavity suited to the particular morphology, that is, a more customizable cavity shape may be achieved.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/919,983 filed Mar. 26, 2007, which is hereby fully incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to an apparatus and method for removing, reaming, debriding and/or resecting tissue and/or bone. In particular, the present invention is directed to a shaper that may be incrementally deployed to create a variety of cavity shapes. The apparatus and method of the present invention may be especially useful in medical procedures such as orthopedic surgery. 
       BACKGROUND 
       [0003]    Medical procedures involving the removal of tissue from a region of a body are well known in the art. The present invention may be particularly useful in spine surgery. A variety of tools are available for surgeons to remove spinal disc tissue and/or bony tissue during surgery in the spinal region. 
         [0004]    Pituitary rongeurs and curettes are the most frequently used instruments to remove tissue. Some examples of these instruments are described in the following U.S. Patents: U.S. Pat. Nos.: 6,200,320 to Michelson; 6,142,997 to Michelson; 5,961,531 to Weber et al.; 5,766,177 to Lucas-Dean et al.; 5,653,713 to Michelson; 5,484,441 to Koros et al.; 5,451,227 to Michelson; 5,312,407 to Carter; 5,026,375 to Linovitz et al. 5,061,269 to Muller; 4,990,148 to Worrick, III et al.; 4,777,948 to Wright; 4,733,663 to Farely; 4,722,338 to Wright et al.; 3,902,498 to Niederer; 3,628,524 to Jamshidi and 2,984,241 to Carlson. 
         [0005]    The use of rongeurs and curettes tends to leave behind fragments of tissue. Further, because these rongeurs and curettes require multiple passes, the operation may be prolonged, possibly leading to increased bleeding and higher infection rates. Many pituitary rongeurs utilize a single cutting blade at the end of a single, unopposed beam. Actuation of the beam, by means of a drive rod, tends to force the distal shaft to move away from the tissue being cut. An open section in the middle of the beam helps reduce this movement, but does not effectively eliminate the unwanted movement. 
         [0006]    U.S. Pat. No. 5,445,639 to Kuslich et al., describes an intervertebral reamer used to ream out the interior of a degenerated disc to clean the interbody space. U.S. Pat. No. 6,383,188 to Kuslich et al., discloses an expandable reamer including a pair of opposing blades which have a expanded state and a retracted state. The blades are pivotally positioned at the distal end of a shaft assembly. 
         [0007]    U.S. Pat. No. 6,575,978 to Peterson et al., discloses a circumferential resecting reamer tool. The reamer disclosed in the &#39;978 Patent is a multibladed cutting tool that circumferentially reams tissue. The cutting blades sweep through an arc creating a transverse cavity. 
         [0008]    U.S. Pat. No. 5,928,239 to Mirza discloses a reamer which has a shaft and a cutting tip attached through a free rotating hinge such that high speed rotation allows the tip to be deflected outwardly to form a cavity. U.S. Pat. No. 5,591,170 to Spievack et al discloses a powered bone saw which inserts its cutting blade through a bored intramedullary canal. 
         [0009]    U.S. Pat. Nos. 6,440,138 and 6,863,672 to Reiley et al., describe tools for creating cavities in bone wherein the tool includes various cutting tips carried on a shaft. The cutting tips disclosed include a rotatable loop, brush, or blade, a linear cutting blade and an energy transmitter. U.S. Pat. No. 6,923,813 to Phillips et al., discloses tools for creating voids in interior body regions. The tools include several different cutting tips which provide for rotational and translational cutting. 
         [0010]    While these various surgical tools are effective in creating cavities within a patient&#39;s body, it would be desirable to provide a tool for removal of tissue that is capable of more refined control, particularly of cavity shape, yet is simple to operate. 
       SUMMARY OF THE INVENTION 
       [0011]    In an embodiment, the present invention comprises a shaper for reaming tissue having a single articulating head operably connected to a shaft. According to one aspect, incremental deployment allows for a unique utility in shaping a cavity suited to the particular morphology, that is, a more customizable cavity shape may be achieved. 
         [0012]    In one embodiment of the present invention, an articulating shaper for reaming tissue includes as least one cutting element that is operably connected to the distal end of the shaper. An actuator may be operably engaged to the proximal end of the shaper to incrementally deploy the cutting element to create a desired cavity shape. In an embodiment the shaper may include a handle that deploys the cutting element in a sweeping motion. Thus, the shaper may be used to create virtually any cavity shape by deploying the cutting element incrementally and/or in a sweeping motion. 
         [0013]    In one embodiment, an internal rod may be threadably connected to an actuator. The actuator may be turned to deploy the cutting end to an intermediate fixed position without activating the handle. 
         [0014]    In another embodiment, the shaper may limit input force to prevent shear force failure of distal mechanisms through the use of clutches. One such clutch may be a ball detent clutch that may employ a spring force multiplier fulcrum arm. The ball detent clutch may include an internal rod connected to a female ball detent groove. The ball detent may act as a slip clutch using a fulcrum to decrease the height and multiply the spring force. The clutch may utilize materials with low yield point and fracture loads to limit input forces. According to one aspect the clutch may use spring force and cam angles to limit input forces. In yet another embodiment, the clutching device may include a spring that determines the break away force. 
         [0015]    According to one embodiment of the present invention, the shaper may include a handle that may drive a rod carrier forward such that a pin bears on a pressure limiting clip. In an embodiment, a pressure limiting clip may crack when the pressure at the distal end of the shaper reaches a maximum pressure. When the clip cracks, the pin may rebear against the rod carrier enabling the shaper to be closed and removed. In an embodiment, the pressure limiting clip may be unclipped and flipped around for use on the other side. 
         [0016]    In another embodiment, the shaper includes a blade at its distal end. The blade may be pivotally actuated by an offset lever arm. The offset lever arm may be connected to and activated by a spring bar through linear, forward, coaxial movement. The spring bar allows the offset lever arm to pivot away from the axis of movement without the requirement of another hinge point and separate link arm. The blade may be pressure sensitive such that a user may be able to feel feedback on the handle as to what tissue the blade is cutting, such as for example, bone, cartilage, annulus or nucleus. 
         [0017]    In an embodiment, the shaper may be activated using a squeezing hand motion to generate articulating angular sweeping cutting blade motion. According to one aspect, an articulating cutting blade may include one pivoting connection point to the instrument shaft and one pivoting activation point. 
         [0018]    In an embodiment, a spring bar allows coaxial linear force to transition to non-coaxial angular force without a pivoting connection. According to one aspect, the shaper may include multiple links to increase perpendicular cutting offset. According to another aspect, the shaper may include multiple link controls to pivot a cutting head 90 degrees, and to maintain the 90 degree position with additional perpendicular offsets to instrument access. 
         [0019]    In an embodiment where the shaper is used to create a cavity in a disc space, the shaper may generally create a cavity parallel to the endplates. In an embodiment where the shaper is used to create a cavity within a collapsed or wedged vertebral body, the shaper may create a cavity generally parallel to the unfractured, caudal vertebral endplate. In another embodiment the shaper may be rotated or moved longitudinally to create virtually any desired cavity shape. In yet another embodiment, the shaper may be used as a curette with the cutting end in a fixed position. 
         [0020]    In another embodiment, the shaper may include a two-stage articulated shaper that may be passed through an entrance hole in a collapsed state and deployed to an expanded state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0021]      FIG. 1  is a perspective view of an embodiment of a shaper according to the present disclosure. 
           [0022]      FIG. 2  is a perspective view of the various components of an embodiment of a shaper according to the present disclosure. 
           [0023]      FIG. 3  is a perspective view of a clutch/force multiplier according to one embodiment. 
           [0024]      FIG. 4  is an exploded view of a clutch according to one embodiment. 
           [0025]      FIG. 5  is an exploded view of a clutch according to another embodiment. 
           [0026]      FIG. 6  is a perspective view of an alternate embodiment of a shaper. 
       
    
    
     DETAILED DESCRIPTION  
       [0027]    Referring to  FIG. 1  there can be seen a shaper  10  according to one aspect of the present invention. Shaper  10  may include a proximal end  20  and a distal end  30 . Shaper  10  may further include a handle  40  and a shaft  50 . Referring now to  FIG. 2 , it can be seen that a cutting head  60  may be operably engaged to distal end  30 . Cutting head  60  may be a single articulating head. In an embodiment cutting head  60  may be a blade. In one preferred embodiment, cutting head  60  may be operably connected to spring bar  70  and shaft  50 . In an embodiment, cutting head  60  may be pivotally connected to spring bar  70  and shaft  50 . Spring bar  70  may be operably connected to a driving rod  80  that is operably connected to a clutch box  90 . Clutch box  90  may be actuated by a handle lever  100 . Spring bar  70  may be adjacent to cutting head  60  such that driving rod  80  may remain concentric to shaft  50 . Spring bar  70  may be operably connected to an offset lever arm  72 . Offset lever arm  72  may be activated by spring bar  70  in linear, forward coaxial motion. Spring bar  70  allows offset lever arm  72  to pivot away from the axis of movement without requiring another hinge point and separate link arm. 
         [0028]    In one embodiment, lever  100  may activate clutch box  90 , which in turn moves driving rod  80  forward. Driving rod  80  pushes spring bar  70  forward which articulates cutting head  60 . Cutting head  60  may be articulated from a neutral position in line with shaft  50  to a position in the range of about 130 degrees from the center line of shaft  50  and may be fixed in any position there between. In an embodiment, the shaper includes a blade at its distal end. The blade may be pivotally actuated by offset lever arm  72 . The blade may be pressure sensitive such that a user may be able to feel feedback on the handle as to what tissue the blade is cutting, such as for example, bone, cartilage, annulus or nucleus. 
         [0029]    In an embodiment, the shaper may be activated by squeezing lever  100  to generate articulating angular sweeping cutting blade motion. According to one aspect, an articulating cutting blade may include one pivoting connection point to the instrument shaft and one pivoting activation point. 
         [0030]    The articulation of cutting head  60  allows shaper  10  to remove tissue such that a void that is at least twice the width of the blade length may be created. Shaper  10  may be rotated, moved longitudinally or a combination of the two. 
         [0031]    In another embodiment, shaper  10  may include an actuator at its proximal end  20 . According to one aspect, an actuator may be threadably connected to driving rod  80  such that when the actuator is activated, driving rod  80  may deploy cutting head  60  into incremental fixed positions. An actuator may be used without activating handle lever  100 . When cutting head  60  is in a fixed position, shaper  10  may be used as a curette, or scraping tool. Thus, the actuator may be used to limit articulation to a partial stroke. 
         [0032]    In one embodiment, shaper  10  may be in the range of about 3 mm to about 7 mm in diameter. When shaper  10  is inserted into a body cavity, cutting head  60  may be in line with shaft  50 , allowing shaper  10  to be inserted through a minimally invasive opening such as a small surgical cannula. Because cutting head  60  may be incrementally articulated from a position in line with shaft  50  to a position in the range of about 130 degrees from the center line of shaft  50 , virtually any shape cavity may be created. 
         [0033]    As can be seen in  FIG. 3 , in an embodiment, a pressure limiting clip  92  may be placed over clutch box  90 . Clutch box  90  may further include pin  94 . Handle lever  100  may activate clutch box  90  driving clutch box  90  forward such that pin  94  bears on pressure limiting clip  92 . In one embodiment, pressure limiting clip  92  may include intentional fracture points such that clip  92  cracks when distal end  30  reaches a maximum pressure in the range of about 30 to 80 psi. A user may be able to hear and feel the crack. Pin  94  may rebear against clutch box  90 . A user may then close and remove the instrument. In one embodiment, clip  92  may be unclipped and flipped over for reuse on the uncracked/intact side. 
         [0034]    In yet another embodiment, the shaper may limit input force to prevent shear force failure of distal mechanisms through the use of clutches. One such clutch may be a ball detent clutch that may employ a spring force multiplier fulcrum arm. In an embodiment as depicted in  FIG. 4 , the force multiplier may be a space saving ball detent clutch  120  that may use a pivoting force multiplier  122  to prevent overloading driving rod  80 . Clutch  120  may include a ball detent  124  and a fulcrum  126 . Ball detent  124  may act as a slip clutch using a fulcrum  126  to decrease the height and multiply the spring force. Driving rod  80  may include a male surface  82  that operably connects to a female surface  112  of the ball detent  124 . Fulcrum  126  creates a force multiplier such that smaller diameter springs with restricted force capacity can be used to increase force against the ball for higher disengagement forces while reducing the overall height of the instrument. The clutch may utilize materials with low yield point and fracture loads to limit input forces. According to one aspect the clutch may use spring force and cam angles to limit input forces. 
         [0035]    In another embodiment, as depicted in  FIG. 5 , clutch  300  may include a spring  310  a cam  320  and a clutch body  340 . If driving rod  80  is over driven, pin  94  may push cam  320  against spring  310 . The amount of force on spring  310  and the angle of cam  320  determine the break away force required. 
         [0036]    In use, shaper  10  may be placed generally in the center of a location in a patient&#39;s body where a cavity to be created. Cutting head  60  may be articulated to the desired position and used as a scraping tool, and/or cutting head  60  may be used to cyclically sweep out a cavity. A combination of scraping and sweeping may be used to create the desired cavity shape. Further, the articulating cutting head  60  permits shaper  10  to be rotated or moved longitudinally. Shaper  10  may also be placed deeper or shallower in the cavity, to create the desired cavity shape. Because a combination of incremental deployment, sweeping rotating and longitudinal movement may be accomplished with the shaper  10 , a customized cavity may be created to comport to the particular morphology being treated. 
         [0037]    In an alternate embodiment as depicted in  FIG. 6  shaper  200  may be a two-stage articulated shaper that may be passed through an entrance hole in a collapsed state and deployed to an expanded state. In this embodiment, multiple, individually controlled, toggle links in conjunction with flexible control link drivers create a ridged angled shaper. In a collapsed state, the shaper may be inserted through a very small diameter working cannula. In one embodiment, the shaper may be sequentially deployed in two stages. The first stage of deployment may set a desired cutting position of a distal cutting head. The second stage of deployment may drive a cutting head perpendicularly away from the center of the shaper maintaining a predetermined, first stage deployment, cutting head position. 
         [0038]    According to one aspect, each stage of deployment may be achieved by individual links including a pivot fulcrum point  220 , arm  240 , and a flexible driving member  260  operably connected to individual linear drivers. Flexible driving members  260  may be comprised of flexible spring materials including, but not limited to: nitinol, 303 Full Hard stainless steel, 420 stainless steel, and/or 17-4 H900 stainless steel. 
         [0039]    Shaper  200  may include a distal cutting head  280  that may be configured to work in a linear scraping action consistent with curettes, or may be configured to work in a sweeping motion. Cutting head  280  may be positioned in a neutral position in line with the center line of the instrument. Cutting head  280  may be deployed to about 90 degrees with about a 20 mm offset of perpendicular from the centerline of the instrument or may be maintained in any position in between. The deployment range is dependent on the number and the length of links. 
         [0040]    Shaper  200  may include an anchor link  212  and a deployment link  214 . During the second stage of deployment, deployment link  214  may be operably connected to anchor link  212  at the fulcrum position of deployment link  214 . Shaper  200  may further include a deployment link activation arm  216  that may be operably connected by a pivot point  218  to a flexible band  260  which may also be operably connected to a proximal instrument linear deployment mechanism. The deployment mechanism may be a screw or cam device or any other suitable deployment mechanism. 
         [0041]    The first stage band  222  may deploy cutting head  280  incrementally from a neutral position inline with the shaper to a position in the range of about  90  degrees from neutral. Cutting head  280  may be locked in any position. Cutting head  280  may be deployed by linear band movement to the arm  240 . Second stage deployment may be activated by linear motion of the intermediate control band. Deployment may be incremental, and cutting may be done at any stage of deployment. A cavity that is unilateral to the axis of shaper insertion may be created. 
         [0042]    This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.