Abstract:
A system for performing a laminoplasty procedure in a spinal vertebra includes an implant and an inserter tool. The implant is configured to be placed on a previously formed lamina opening of the spinal vertebra, and is shaped and dimensioned to be placed in the lamina opening after the opening has been distracted. The inserter tool is configured to insert the implant near the lamina opening and then to distract the lamina opening so that the lamina opening is dimensioned to receive the implant and then to place the implant into the distracted lamina opening while simultaneously holding the lamina opening in a distracted state.

Description:
CROSS REFERENCE TO RELATED CO-PENDING APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 61/955,892 filed Mar. 20, 2014 and entitled “SYSTEM AND METHOD FOR SPINAL DECOMPRESSION”, the contents of which are expressly incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a system and method for spinal decompression, and in particular to laminoplasty fixation devices, tools and methods. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cervical laminoplasty is a surgical technique that is used to remove pressure from the spinal cord in the neck area. Pressure on the spinal cord is usually due to spinal stenosis that may be caused by degenerative changes, arthritis, bone spurs, disc herniations, ossification of the posterior longitudinal ligament (OPLL), tumors, or fractures, among others. Frequently, spinal stenosis occurs simultaneously at multiple levels of the cervical spine. If the pressure is severe enough, myelopathy can develop. In this case, laminoplasty may be applied for removing the pressure, allowing the spinal cord to heal, and reversing the symptoms. 
         [0004]    Laminoplasty involves cutting the lamina on both sides of the vertebra and swinging one side of the cut bone away in order to hinge open the spinal canal. This is called the “open door” procedure, where in one side of the lamina a complete through-cut is performed and in the other side a groove or partial cut is formed and the lamina is then hinged opened about the groove in order to increase the diameter of the spinal canal and remove the applied pressure on the spinal cord. Part of the lamina and/or the spinous process may be removed during laminoplasty. The hinged lamina is supported in the open position via a plate that is inserted and fixed between the facet and the cut end of the lamina. 
         [0005]    Typically, the surgeon needs to determine the size of the opening and the size of the plate to use in order to increase the diameter of the spinal canal sufficiently so that the pressure on the spinal cord is removed. Flexibility in the size and the overall dimensions of the plate is desirable in order to accommodate various size vertebras. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention relates to a system and a method for spinal decompression, and in particular to laminoplasty fixation devices, tools and methods. 
         [0007]    In general, in one aspect, the invention features a system for performing a laminoplasty procedure in a spinal vertebra, including an implant and an inserter tool. The implant is configured to be placed on a previously formed lamina opening of the spinal vertebra, and is shaped and dimensioned to be placed in the lamina opening after the opening has been distracted. The inserter tool is configured to insert the implant near the lamina opening and then to distract the lamina opening so that the lamina opening is dimensioned to receive the implant and then to place the implant into the distracted lamina opening while simultaneously holding the lamina opening in a distracted state. 
         [0008]    Implementations of this aspect of the invention may include one or more of the following features. The implant comprises an elongated body having first second and third segments and the first and third segments extend in opposite directions from opposite ends of the second segment and form first and second angles with an axis extending along the second segment, respectively. The implant further includes a first elongated opening formed in the first segment and the first elongated opening extends along a first axis and comprises an oval shape and is dimensioned to hold a bone fastener in two different locations of the first elongated opening or two bone fasteners in the two different locations of the first elongated opening, respectively. The implant further includes a second elongated opening formed in the third segment and the second elongated opening extends perpendicular to the first axis and comprises an oval shape and is dimensioned to hold a bone fastener in two different locations of the second elongated opening or two bone fasteners in the two different locations of the second elongated opening, respectively. The implant further includes a ledge extending from the second segment and being shaped and dimensioned to surround the lamina. The implant further includes a trough formed in the second segment and designed to accommodate bonegraft. The inserter tool comprises an elongated shaft and a distal end and the distal end includes first and second spreadable shims. The first and second spreadable shims are shaped and dimensioned to pass through first and second openings formed in the implant and the implant is configured to slide down along the first and second shims by pushing the elongated shaft down and to spread the first and second shims apart. The first and second ends of the first and second shims are configured to engage first and second locations within or near the lamina opening, respectively, and to distract the lamina opening as they spread apart. At least one of the first and second ends of the first and second shims comprises a hook. The elongated shaft includes a distal end component configured to engage the implant. The inserter tool further includes a handle attached to a proximal end of the shaft and activation of the handle pushes the elongated shaft down or up. 
         [0009]    In general in another aspect the invention features a method for performing a laminoplasty procedure in a spinal vertebra, including the following. Providing an implant configured to be placed on a previously formed lamina opening of the spinal vertebra. The implant is shaped and dimensioned to be placed in the lamina opening after the opening has been distracted. Providing an inserter tool configured to insert the implant near the lamina opening and then to distract the lamina opening so that the lamina opening is dimensioned to receive the implant and then to place the implant into the distracted lamina opening while simultaneously holding the lamina opening in a distracted state. The inserter tool comprises an elongated shaft and a distal end and the distal end has first and second spreadable shims. The first and second spreadable shims are shaped and dimensioned to pass through first and second openings formed in the implant and the implant is configured to slide down along the first and second shims by pushing the elongated shaft down and to spread the first and second shims apart. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Referring to the figures, wherein like numerals represent like parts throughout the several views: 
           [0011]      FIG. 1A  depicts one embodiment of the graft plate, according to this invention; 
           [0012]      FIG. 1B  is a perspective view of the embodiment of  FIG. 1A ; 
           [0013]      FIG. 1C  is a side view of the embodiment of  FIG. 1A ; 
           [0014]      FIG. 1D  is a top view of the embodiment of  FIG. 1A ; 
           [0015]      FIG. 2A  depicts another embodiment of the graft plate, according to this invention; 
           [0016]      FIG. 2B  is a perspective view of the embodiment of  FIG. 2A ; 
           [0017]      FIG. 2C  is a side view of the embodiment of  FIG. 2A ; 
           [0018]      FIG. 2D  is a top view of the embodiment of  FIG. 2A ; 
           [0019]      FIG. 3A  depicts an embodiment of a hinge plate, according to this invention; 
           [0020]      FIG. 3B  is a perspective view of the embodiment of  FIG. 3A ; 
           [0021]      FIG. 3C  is a side view of the embodiment of  FIG. 3A ; 
           [0022]      FIG. 3D  is a top view of the embodiment of  FIG. 3A ; 
           [0023]      FIG. 4A  and  FIG. 4B  depict an embodiment where bilateral graft plates are used to stabilize the lamina, according to this invention; 
           [0024]      FIG. 5  depicts an embodiment of a distractor sizer in the closed and open positions, according to this invention; 
           [0025]      FIG. 5A  and  FIG. 5B  depict the use of the distractor sizer of  FIG. 5  in the process of distracting the cut lamina; 
           [0026]      FIG. 6A-FIG .  6 C depicts the shimmed inserter method for spinal decompression according to this invention; 
           [0027]      FIG. 7A  depicts a shimmed implant inserter, according to this invention; 
           [0028]      FIG. 7B  depicts the proximal end of the shimmed implant inserter of  FIG. 7A ; 
           [0029]      FIG. 7C  depicts the distal end of the shimmed implant inserter of  FIG. 7A ; 
           [0030]      FIG. 8A-FIG .  8 C depict the shimmed implant inserter of  FIG. 7A , as used in a spinal decompression method, according to this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    The present invention relates to a system and method for spinal decompression, and in particular to laminoplasty fixation devices, tools and methods. 
         [0032]    Laminoplasty is usually performed via a posterior approach. During surgery, the patient lies face down on the operating table and an incision is made in the back of the neck. In the “open door” laminoplasty procedure, instead of removing the lamina and other compressive structures, the lamina is completely through-cut on one side between the lamina and the lateral mass and partially cut on the opposite lateral side. This creates a hinge on the partial cut side of the lamina and a small opening on the opposite lateral side. The lamina is then moved into the “open” position by elevating the lamina on the open side. This increases the diameter of the spinal canal and makes space available for the spinal cord. The spinal cord is decompressed and the spinal fluid can flow around the spinal cord. A plate or a wedge made out of bone, metal, or plastic, is usually inserted in the open side to hold the spinal canal open. The final position resembles an open door being held open with a door stop, and therefore the procedure is referred to as an “open-door” laminoplasty. 
         [0033]    Referring to  FIG. 1A-FIG .  1 D, graft plate  100  creates a brace between the lamina  92  and the lateral mass  94  of the posterior of vertebra  90 . In doing so, the diameter of the inner canal space  91  for that particular segment is opened up and this relieves congestion and compression in the spinal canal. Graft plate  100  includes an elongated body having a first segment  101 , a second segment  103  and a third segment  105 . First and third segments  101 ,  105 , extend in opposite directions from the second segment  103  and form angles  110  and  111 , with the second segment, respectively. First segment  101  includes an elongated opening  102  extending along axis x and being designed to hold two bone fasteners in two separate positions or one bone fastener in two different positions. As shown in  FIG. 1D , opening  102  includes an oval-shaped outer perimeter  102   a  and an inner perimeter  102   b  having an oval shape with a constricted center  102   c . Through the circular ends  102   d ,  102   e  of the inner perimeter  102   b , two separate bone fasteners can pass through in order to attach the graft plate  100  to the lamina. Alternatively, one bone fastener passes either through end  102   d  or through end  102   e  in order to attach the graft plate to two different positions of the lamina, thereby increasing or decreasing the diameter of the canal space  91 . First segment  101  also includes a rectangular opening  107  dimensioned to engage a shimmed inserter tool, as will be described below. The second segment  103  includes a ledge  104  to surround the lamina and lodge it into the optimal plate position, and a trough  106  designed to accommodate different forms of bonegraft, such as cancellous sponge, chips, demineralized bone matrix (dbm), or synthetic bonegraft. Bonegraft facilitates blood flow and promotes bone ingrowth for healing. Third segment  105  includes an elongated opening  108  extending along axis y perpendicular to axis x of opening  102  and being designed to hold two bone fasteners in two separate positions or one bone fastener in two different positions. As shown in  FIG. 1D , opening  108  includes oval-shaped outer and inner perimeters  108   a ,  108   b  having a constricted center  108   c . Through the circular ends  108   d ,  108   e  of the inner perimeter  108   b , two separate hone fasteners can pass through in order to attach the graft plate  100  to the lateral mass  94 . Alternatively, one bone fastener passes either through end  108   d  or through end  108   e  in order to attach the graft plate to two different positions of the lateral mass  94 . First and third segments  101 ,  105  also include spikes or serrations  109  used for engaging the graft plate  100  to the lamina  92  and the lateral mass  94 , respectively. 
         [0034]    Referring to  FIG. 2A-FIG .  2 D, in another embodiment, plate  200  creates a brace between the lamina  92  and the lateral mass  94  of the posterior of vertebra  90 . In doing so, the diameter of the inner canal space  91  for that particular segment is opened up and this relieves congestion and compression in the spinal canal. Plate  200  includes an elongated body having a first segment  201 , a second segment  203  and a third segment  205 . First and third segments  201 ,  205 , extend in opposite directions from the second segment  203  and form angles  210  and  211 , with the second segment, respectively. First segment  201  includes an elongated opening  202  extending along axis x and being designed to hold two bone fasteners in two separate positions or one bone fastener in two different positions. As shown in  FIG. 2D , opening  202  includes an oval-shaped outer perimeter  202   a  and an inner perimeter  202   b  having an oval shape with a constricted center  202   c . Through the circular ends  202   d ,  202   e  of the inner perimeter  202   b , two separate bone fasteners can pass through in order to attach the plate  200  to the lamina. Alternatively, one bone fastener passes either through end  202   d  or through end  202   e  in order to attach the plate  200  to two different positions of the lamina, thereby increasing or decreasing the diameter of the canal space  91 . Second segment  203  includes a ledge  204  designed to surround the lamina and lodge it into the optimal plate position. Third segment  205  includes an elongated opening  208  extending along axis y perpendicular to axis x of opening  202  and being designed to hold two bone fasteners in two separate positions or one bone fastener in two different positions. As shown in  FIG. 2D , opening  208  includes oval-shaped outer and inner perimeters  208   a ,  208   b  having a constricted center  208   c . Through the circular ends  208   d ,  208   e  of the inner perimeter  208   b , two separate bone fasteners can pass through in order to attach the plate  200  to the lateral mass  94 . Alternatively, one bone fastener passes either through end  208   d  or through end  208   e  in order to attach the plate to two different positions of the lateral mass  94 . 
         [0035]    In some cases, a plate is also used to support the hinged side of the lamina. Referring to  FIG. 3A-FIG .  3 D, in another embodiment, plate  200  creates a brace between the lamina  92  and the lateral mass  94  of the posterior of vertebra  90  and a hinge plate  300  is fixed to the opposite side of plate  200  or graft plate  100  and is used to secure the contra-lateral lamina. This lamina  92  in this case is burred to help create the pivot. The burring process may weaken the lamina and the hinge plate  300  strengthens the pivot. Hinge plate  300  is placed between the lamina  92  and lateral mass  95  at the treated area that creates the pivot point  96 . Hinge plate  300  includes an elongated body having a first segment  301  and a second segment  305 . Second segment  305  forms an angle  311 , with the first segment  301 . First segment  301  includes two adjacent through-openings  302   a ,  302   b . Openings  302   a ,  302   b  have round shaped outer diameters and oval-shaped inner diameters extending along axis x. Two separate bone fasteners pass through the circular openings  302   a ,  302   b  in order to attach the hinge plate  300  to the lamina  92 . Second segment  305  includes two adjacent openings  308   a ,  308   b  arranged along axis y perpendicular to axis x, and a constricted center  308   c . Openings  308   a ,  308   b  have round shaped outer diameters and oval-shaped inner diameters extending along axis y. Two separate bone fasteners pass through the circular openings  308   a ,  308   b  in order to attach the hinge plate  300  to the lateral mass  95 . 
         [0036]    In another embodiment, bilateral graft plates are used to support the lamina. Referring to  FIG. 4A  and  FIG. 4B , graft plates  100   a ,  100   b  are used to support the lamina to the lateral masses  94 ,  95 , respectively. In this configuration the height of the spinal canal  91  is increased and there is no pivoting of the lamina. 
         [0037]    In operation, the lamina  92  is completely cut-through on one side  93  between the lamina  92  and the lateral mass  94  and partially cut  96  on the opposite lateral side  95 , as shown in  FIG. 5A  and  FIG. 5B . This creates a hinge on the partial cut side  96  of the lamina  92  and a small opening  93  on the opposite lateral side  94 . The lamina  92  is then moved into the “open” position by elevating the lamina on the open side  93 , as shown in  FIG. 5B . In one embodiment, the lamina  92  is distracted posteriorly into the “open” position  165   a  by inserting a distractor sizer tool  165  between the lamina  92  and the lateral mass  94 , shown in  FIG. 5 . Referring to  FIG. 5 , distractor sizer  165  is a surgical instrument used to distract the height between the burred lamina  92  and the lateral mass  94 . Distractor sizer  165  is also used to read the correct height of expansion and to determine the correct measurement of graft plate or standard plate to use in this procedure. This distractor sizer  165  includes an outer shaft  168  surrounding an inner shaft  169  from proximal to distal ends, a top spreader  171  and a bottom spreader  170  at the distal end, a handle  166  and an actuating lever  167  at the proximal end. The distractor sizer spreaders  170 ,  171  are inserted between the lamina and the lateral mass to distract the lamina posteriorly, and then the actuating lever  172  is pulled back along arrow  172  to advance the inner shaft  169  distally and thereby to activate the top spreader  171  and distract the lamina posteriorly. Next, the graft plate  100  is inserted in the opening between the distracted lamina and the lateral mass. 
         [0038]    Referring to  FIG. 6A-FIG .  6 C, the shimmed inserter method describes a technique for inserting a graft plate  100  or a standard plate  200  or bilateral graft plate  100   a  onto the surgical site while keeping the lamina distraction intact. The method utilizes a shimmed inserter  180  to insert one of either the standard plate  100 , graft plate  200 , or a bilateral graft plate  100   a ,  100   b . The shimmed inserter tool  180  includes a U-shaped body  181  having an open lateral mass end  184  and a hook end  182 . The legs  181   a ,  181   b  of the U-shaped body  181  have cross-section matching the cross-sections of openings  107  and  108  of the graft plate. Legs  181   a ,  181   b  are inserted into openings  107  and  108  of the graft plate and  100  the graft plate  100  is moved toward the proximal closed end of the U-shaped body  181  of the shimmed inserter  180 , as shown in  FIG. 6A . After drilling screw holes  186   a  in the lamina and after burring the lamina, the shimmed inserter lateral mass end  184  is placed in a pre-drilled hole  183  on the lateral mass  94  and the hook end  182  is placed under the cut lamina end  93   a , as shown in  FIG. 6A . Next, leg  181   b  is pulled laterally along direction  180  to pry open and distract the lamina  92  and then the graft plate  100  is pressed down along direction  188  and is placed in the opening  93  between the cut end  93   a  of the lamina and the lateral mass  94 . Next, the graft plate  100  is secured onto the lamina  92  and the lateral mass  94  distally with setscrews  186 ,  187 , respectively, after the shimmed inserter is removed. 
         [0039]    Referring to  FIG. 7A-FIG .  8 C, in another embodiment a shimmed inserter  190  is used to distract the distance in the burred void  93  between the lateral mass  94  and lamina  92 . Shimmed inserter  190  includes a t-handle  192 , an shaft  191  which drives down the implant  100  distally, and a distal end  196  including two shims  197 ,  198  which spread out as the plate  100  is advanced down along axis  250 . The shims  197 ,  198  have cross-sections matching the cross-sections of openings  107  and  108  of the graft plate  100 . Shims  197 ,  198  are inserted into openings  107  and  108  of the graft plate and  100  the graft plate  100  is moved down along axis  120  by rotating the handle  192  and thereby advancing the shaft  191  down, as shown in  FIG. 8A . The distal end of shaft  191  includes an end component  199  that is designed to engage the body of the graft plate  100 . Shimmed inserter  190  also includes a spring lock  193  that in locked position allows shaft  191  to travel proximally without rotating. Initially, the implant  100  is at the top position and the shims  197 ,  198  are at rest and face inward, as shown in  FIG. 8A . Next, the implant  100  is advanced distally, and the shims spread outward forcing the laminal void open, as shown in  FIG. 8B . With the implant  100  fully in place, the shims  197 ,  198 , have pried the lamina fully open and the implant  100  is anchored to the bone. In all these embodiments, the inserters both size the lamina opening  93  to match the length of the implant  100  and insert the implant in place. 
         [0040]    Several embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.