Abstract:
The improvement is a spinal instrument (preferably, a bone screw driver) having a flexible shaft comprising a plurality of interlocking segments carried on a malleable core rod. The flexible shaft allows a screwdriver handle to be perfectly in-line with the cage inserter if desired, while still taking advantage of the tactile feel and torque transmission of the flex segment in its bent position. Accordingly, a surgeon can limit the amount of retraction and keep the driver handle close to the inserter without having to overcome the forces of the flexible segments&#39; natural straight configuration.

Description:
CONTINUING DATA 
       [0001]    This application claims priority from co-pending application U.S. Ser. No. 62/017,596, filed Jun. 26, 2014, entitled “Flexible Spinal Driver or Drill with a Malleable Core, and or Fix Core Radius”, Martin, Docket No. DSP5074USPSP, the specification of which is incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    When performing a spinal procedure such as an anterior cervical discectomy and fusion (ACDF), the surgeon often has a number of implant options that may achieve the desired clinical outcomes of disc height maintenance and pain relief. Because of their clinical benefits, zero-profile fusion cages that accept bone anchors and are secured to the adjacent anatomy have experienced an increased usage and adoption in the ACDF procedure. These cages typically have angled bone anchors (such as screws) that pass through a portion of the cage&#39;s anterior wall and into the adjacent vertebral endplates. 
         [0003]    However, if a surgeon were to choose a low profile, stand-alone fusion device (such as a fixation cage comprising one or more bone screws), there remains a surgical technique challenge associated with the insertion of the screws. Traditionally, an instrument having a straight shaft is used to insert the screws through the cage at the steep angle to ensure bone penetration. However, screw insertion with a straight-shaft instrument at locations up near a patient&#39;s chin or sternum produces some challenging approach angles. Recently, there have been improvements to the insertion instrument that help facilitate screw placement at these difficult approach angles. Some of these improvements include the adoption of universal joints and flexible inserter instruments that allow for torque transmission while still positioning their handles off-axis from the trajectory of the screw. For example, some flexible inserter instruments achieve flexibility by possessing a plurality of interlocking segments just proximal of their distal working tip. Once the tip of such a flexible driver is inserted into the drill guide, the handle of the driver can be repositioned to the desired location and torque can be transmitted to advance the screw. 
         [0004]    However, one of the challenges associated with this flexible technology is that the flexible shaft is typically straight in its resting configuration. Accordingly, one of two procedures needs to be carried out. In a first procedure, the amount of soft tissue retraction has to temporarily be increased in order to engage the tip of the driver into the drill guide and once engaged, the soft tissue retraction can be minimized again and the handle can be held in a desirable position, such as near parallel to the implant inserter. In a second procedure, the tip can be inserted into the drill guide at a less steep angle than the screw trajectory (but not perfectly parallel to the inserter) and the spring force of the flex segment has to be overcome in order for the tip to find the drill guide trajectory. Upon this “turning the corner” step, as a downforce is provided, the self-retention of the screw may become disengaged. 
         [0005]    US Published Patent Application No. 2012-0150301 (Gamache) discloses a flexible bone screw driver comprising: a) a proximal handle, b) an intermediate shaft, c) a flexible distal end portion comprising a plurality of interlocking segments portion and a distal tip adapted to engage a screw head, and d) a pre-bent sleeve that is placed over and around the plurality of interlocking segments, wherein the plurality of interlocking segments portion is substantially straight in its unloaded configuration. 
       SUMMARY OF THE INVENTION 
       [0006]    In order to overcome the issues discussed above, in one aspect of the present invention, and now referring to  FIGS. 1-3 , there is provided an improvement on the flexible shaft technology that has benefits for the patient and the surgeon. The improvement is a bone screw driver having a flexible shaft comprising a plurality of interlocking segments carried on a flexible core rod. The flexible shaft allows a screwdriver handle to be perfectly in-line with the cage inserter if desired, while still taking advantage of the tactile feel and torque transmission of the flex segment in its bent position. Accordingly, a surgeon can limit the amount of retraction and keep the driver handle close to the inserter without having to overcome the forces of the flexible segments&#39; natural straight configuration. The flexible driver can have geometries that allow for flexing, attachment (snapping-on to a drill), and easy cleaning, if desired. 
         [0007]    Therefore, in accordance with the present invention, there is provided a flexible spinal instrument comprising:
   a) a proximal portion adapted for connection to a handle or a drill,   b) an intermediate shaft comprising:
       i) a plurality of interlocking segments, each segment having a throughhole, and   ii) a malleable rod extending through the throughhole of each segment, and   
       c) a distal portion having a working tip.   
 
         [0013]    Preferably, the instrument has a first substantially linear configuration and a second deformed configuration, wherein the second deformed configuration allows rotation of the shaft and an application of force along an axis of the working tip. 
         [0014]    Also in accordance with the present invention, there is provided an assembly comprising:
       a) a spinal implant comprising a at least one threaded throughhole,   b) a bone screw received in the threaded throughhole, the bone screw having a threaded shaft and a proximal head,   c) the spinal instrument of claim  1 ,   wherein the distal tip of the inserter is received in the proximal head of the bone screw,
 
wherein the first bone screw extends through the top surface of the cage.
       
 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0019]      FIG. 1  discloses a perspective view of a portion of the driver of the present invention. 
           [0020]      FIG. 2  discloses a cross-sectional view of a portion of the driver of the present invention. 
           [0021]      FIG. 3  discloses the driver of the present invention driving a screw into a fusion cage implanted between vertebral bodies. 
           [0022]      FIGS. 4-6  disclose embodiments involving a preferred instrument for holding the driver of the present invention. 
           [0023]      FIGS. 7-9  disclose alternate embodiment of the driver of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Now referring to  FIGS. 1-3 , there is provided a flexible bone screw driver comprising:
       a) a rigid proximal portion  1  adapted for connection to a handle  99  or a drill,   b) an intermediate shaft  2  comprising:
           i) a plurality of interlocking segments  7 , each segment having a throughhole  8 , and   ii) a malleable rod  9  extending through the throughhole of each segment, and   
           c) a distal portion  11  having a working tip  13 ,
 
wherein the proximal portion is connected to the intermediate shaft, and
 
wherein the distal portion of the driver is connected to the intermediate shaft.
       
 
         [0030]    The distal portion of the driver has a distal working tip and a proximal connection portion  15 . In general, the working tip is adapted to perform a function on a workpiece via rotation. In some embodiments, the working tip of the driver is adapted to insert bone screws. In others, the working tip of the driver is adapted to drill pilot holes. Preferably, the proximal connection portion is adapted for secure attachment to the distal-most  17  of the interlocking segments. The distal portion of the driver is generally made of a rigid material such as metals or certain plastics. 
         [0031]    The malleable rod can be made of any biocompatible material that will maintain the desired flexible shape. In some embodiments, the flexible rod can be made from a malleable material selected from the group consisting of a polymer or a memory metal (such as nitinol). The selection of the material and rod diameter should be such that the rod can be flexed to any angle between about 0 degrees and 180 degrees. The malleable rod can be fixed to the proximal and distal portions of the driver, or can float therebetween. When the malleable rod floats within the plurality of interlocking segments, this allows for its easy removal for cleaning. In some embodiments, the malleable rod is substantially straight in its unloaded condition. In others, the malleable rod carries has a pre-bent angle in its unloaded condition, thereby pre-determining the trajectory of the tip and facilitating the appropriate and desired insertion angle of the screw into the drill guide without increasing the amount of tissue retraction. In some embodiments, the malleable rod has a distal bearing surface for rotating the outer section of the driver or drill. 
         [0032]    The interlocking segments can be made of any biocompatible material that will maintain the desired shape. This can include metals or certain plastics. In some embodiments, there are between about five and fifteen interlocking segments in the intermediate shaft. In this range, these segments together allow for the desired smooth bending while retaining simplicity. Each interlocking segments has a throughhole adapted for reception of the malleable rod, so that when the interlocking segments are joined, the malleable rod can slide within the series of interlocking segments. The distal-most  17  of the interlocking segments should be adapted for secure attachment to the distal portion of the driver. In some embodiments thereof, the distal-most of the interlocking segments has a tubular distal end  21  that friction_fits over the proximal connection portion of the distal portion of the driver. 
         [0033]    In some embodiments, the driver has a rigid proximal portion  1  that is adapted for connection to a handle. This connection may be permanent or releasable. This allows the surgeon to use the driver manually as a screwdriver. In some embodiments, the driver has a proximal portion that is adapted for connection to a port on a power drill. This allows the surgeon to power the driver via the rotary power supplied by the drill. 
         [0034]    Now referring to  FIG. 3 , there is provided an assembly comprising:
       a) a spinal implant comprising at least one threaded throughhole (preferably a fusion cage  101  comprising a front wall  103 , a pair of opposing side walls  105 , a back wall  107 , and top  109  and bottom  111  surfaces adapted for gripping opposed vertebral endplates, wherein the front wall comprises at least one threaded throughhole),   b) a bone screw received in the threaded throughhole, the bone screw having a threaded shaft  115  and a proximal head  117 ,   c) the driver of the present invention,   wherein the distal tip of the inserter is received in the proximal head of the bone screw,
 
wherein the first bone screw extends through the top surface of the cage.
       
 
         [0039]    Now referring to  FIGS. 4-6 , there is provided an insertion instrument  301  for holding the driver of the present invention. The distal portion of jaw  305  of this instrument includes a receiver  303  that receives the working tip of the driver of the present invention, and holds that working tip at an angle to the longitudinal axis of jaw  305  of the instrument. Squeezing handles  307  acts to open the jaws  309  of the instrument. 
         [0000]    In another aspect of the present invention, the driver may be modified so that there is a flexible outer collar wrapping around a flexible tube to allow the flexible tube to bend in any radius. Preferably, the flexible outer collar has a longitudinal slot running end-to-end that allows the collar to snap onto the flexible tube. This allows the flexible tube to bend in any radius. 
         [0040]    Therefore, in accordance with the present invention, and now referring to  FIGS. 7-8 , there is provided a flexible bone screw driver comprising:
       a) a rigid proximal portion  101  adapted for connection to a handle or a drill,   b) an intermediate shaft  102  comprising:
           i) a flexible tube  107  having a bore  108 , and   ii) an inner flexible rod  109  extending through the bore of the flexible tube, and   ii) an outer malleable collar  110  wrapping around at least a portion of the flexible tube, the collar extending at an angle in an unloaded condition and having a longitudinal slot therein, and   
           c) a distal portion  111  having a working tip  113 ,
 
wherein the proximal portion is connected to the intermediate shaft, and
 
wherein the distal portion of the driver is connected to the intermediate shaft.
       
 
         [0047]    In some embodiments, flexible tube  107  comprises a plurality of rigid interlocking segments  112 , with each segment having a throughbore running therethrough. 
         [0048]      FIG. 9  presents substantially the same driver as  FIG. 8 , except that the inner flexible rod  109  is missing in  FIG. 9 . 
         [0049]    Although the flexible instrument of the present invention has been presented in a driver application, it is understood that the concepts of the present invention can be applied to other spinal instruments challenged by off-angle orientations, including drills, shavers and rasps. 
         [0050]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.