Patent Publication Number: US-2023157711-A1

Title: Vertebral endplate shaver with height adjustable blades

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims the benefit of and/or priority under 35 U.S.C. § 119(e) to U.S. provisional patent application Ser. No. 63/281,915 filed November 22, 2021 titled “Expandable Vertebral Disc Micro Shaver” and U.S. provisional patent application Ser. No. 63/315,638 filed Mar. 2, 2022 titled “MIS Vertebral Endplate Shaver With Height Adjustable Blades,” the entire contents of each of which are specifically incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to instruments for spine procedures and, more particularly, to medical instruments for removing vertebral endplate material from a vertebra in a vertebral disc space of a spine. 
     BACKGROUND OF THE INVENTION 
     Many people contend with spine issues due to age, disease, trauma, congenital, and acquired complications and conditions. While some spine issues can be alleviated without surgery, other spine issues necessitate surgery. Spine surgery may entail removing vertebral disc material from between adjacent vertebrae. This can be accomplished using minimally invasive surgery, micro surgery, or the like. Such surgery reduces trauma by using surgical instruments that are introduced into the body via one or more small incisions. Certain of these medical instruments are introduced into the body via an access tube, endoscope, cannula or the like (collectively, cannula) that has been inserted into the body through a small incision and positioned accordingly. Other medical instruments can then be inserted into the cannula and controlled accordingly. Some medical instruments include a “built-in” cannula wherein the medical instrument with the cannula is inserted into an incision, positioned accordingly, and manipulated. 
     Various surgical spine procedures may be performed via a cannula (separate from or as part of the medical instrument). When an intervertebral spine implant is to be installed between adjacent vertebrae (i.e. in the vertebral disc space) it is necessary to properly prepare endplate surfaces of the adjacent vertebrae. Proper vertebral endplate surface preparation typically includes using a medical instrument with a cannula such as a vertebral endplate preparation instrument/tool (vertebral endplate shaver) to decorticate or shave the vertebral endplate surfaces to ensure adequate seating of the intervertebral spine implant. Typical vertebral endplate preparation tools have static blades (i.e. their blade(s) are fixed in height) that are inserted into a vertebral disc space and rotated to decorticate vertebral endplate surfaces of adjacent vertebrae. Because the blades are fixed in height a series of static vertebral endplate preparation tools each one having blades of a different radial height is therefore used to decorticate or shave the vertebral endplate surfaces. Such a series may be deemed a set of static vertebral endplate preparation tools. 
     Using static vertebral endplate preparation tools to properly decorticate vertebral endplate surfaces can increase the likelihood of problems since multiple static vertebral endplate preparation tools must be inserted into and removed from the cannula during the spine procedure. However, with a vertebral endplate preparation tool having height adjustable (dynamic) blades, a single medical instrument can be used to decorticate vertebral endplate surfaces. It is therefore preferable to use a vertebral endplate preparation tool having blades that can be easily varied in height. 
     Various vertebral endplate preparation tools with height adjustable blades have heretofore been devised. However, prior art vertebral endplate preparation tools with height adjustable blades suffer from several shortcomings such as, but not limited to, overall ease of use, ease of varying blade height, and not being conducive to use with a cannula. 
     It would therefore be desirable to have a vertebral endplate preparation tool with height adjustable (dynamic) blades that overcomes the deficiencies of prior art vertebral endplate preparation tools with height adjustable blades. The present vertebral endplate preparation tool with height adjustable (dynamic) blades addresses the above and more. 
     SUMMARY OF THE INVENTION 
     A medical instrument in the form of a vertebral endplate preparation tool with height adjustable (dynamic) blades for decorticating/shaving vertebral endplates during a spine procedure particularly, but not necessarily, using a cannula, has a head with at least one height adjustable blade for decorticating/shaving vertebral endplate material from a vertebra of a spine. The height adjustable blade(s) is/are configured to controllably move outward radially from the head and controllably move inward radially into the head upon manipulation of a controller of the vertebral endplate preparation tool with height adjustable instrument that is coupled to the head. The amount of outward radial movement of the blade(s) is controllable to set a height of the blade(s). With the blade(s) radially moved outward, they extend radially beyond a diameter of the head and an associated cannula. Rotation of the head via a handle of the vertebral endplate preparation tool with height adjustable rotates the blade(s) to allow decorticating of the vertebral endplates. 
     In one form, the present vertebral endplate preparation tool with height adjustable blades has a handle, a controller operably connected to the handle, a control shaft defining a distal control shaft end and a proximal control shaft end that is operably connected to the controller for controlled manipulation of the control shaft, and a head on the distal control shaft end having first and second blades for decorticating or shaving vertebral endplates of vertebrae of a spine. The first and second blades controllably move outward radially (expand) from the head, and controllably move inward radially (collapse) into the head upon manipulation of the controller. The vertebral endplate preparation tool with height adjustable blades may include a cannula with the control shaft disposed within. Movement of the handle operates the controller to manipulate the control shaft to axially extend the head from a cannula, controllably expand the first and second blades radially outward to a desired height from the head beyond a diameter of the cannula after the head has been extended from the cannula, and contract the first and second blades into the head when vertebral endplate decorticating/shaving is finished. 
     In one form, each blade has a concave portion for allowing shaved vertebral endplate material to collect therein. In one form, cutouts or windows in a lower portion of the blade(s) aid in allowing vertebral endplate material to be collected, then removed. When rotated, the blades(s) provide an almost 180° collection sweep outside of a longitudinal plane (axis) of the associated cannula. 
     The head has a nose and a rear or base that each slidingly hold an end of each blade for radial expansion/contraction of each blade from the head. The moving connection between the nose and an end of the blades is preferably, but not necessarily, via angled dovetail configurations. The moving connection between the base and another end of the blades is also preferably, but not necessarily, via angled dovetail configurations. 
     Once the head is external of the cannula, axial movement in one direction of a component of the control shaft that is connected to a nose of the head, pulls the nose axially towards the base of the head to provide axial compression. Axial compression of the nose towards the base axially compresses against the movable blades to slide them radially outward from the nose and base to expand the blades from the head. Axial movement of the control shaft in an axially opposite direction allows retraction of the blades into the head, through release of axial pressure. 
     In another form, the dynamic vertebral endplate preparation tool has height adjustable blades at a distal end of a shaft assembly for decorticating/shaving vertebral endplate material from vertebrae of a spine, translates axial movement of a control rod of a shaft assembly into radial blade height change (radial blade height extension or retraction) through a controller of a handle assembly of the dynamic vertebral endplate preparation tool. The blades controllably move outward radially (extend) from the distal end of the shaft assembly and controllably move inward radially (retract) into the distal end of the shaft assembly upon manipulation of the controller in a head of the dynamic vertebral endplate preparation tool that is connected to the shaft assembly. 
     Once the blades are expanded, they extend radially beyond a diameter of an associated cannula. Rotation of the blades turn the blades to provide decorticating/shaving of vertebral endplate material. The blades may be configured to also collect and removal of shaven vertebral endplate material. 
     Radial extension and retraction of the blades from the distal end of the shaft assembly is accomplished in one form via mutual angled dovetail features of the blades and the distal end whereby axial force against the blades (compression) via the control rod effects radially outward movement (extension) of the blades via the mutual angled dovetail features between the blades and the distal end (a first axial direction). Reverse axial movement of the control rod releases axial pressure (force) against the blades to effect radially inward movement (retraction) of the blades. In one form, the distal end has angled dovetail slots or channels that receive angled dovetail ends or flanges of the blades (a second axial direction opposite the first axial direction). In a particular form, the distal end has front angled dovetail slots/channels and rear angled dovetail slots/channels that receive respectfully a front dovetail end or flange and a rear dovetail end or flange of each blade. 
     Radial extension and retraction of the blades from the distal end is accomplished in one form via pins of the distal end situated in angled slots of the blades whereby axial translation of the pins against the angled slots of the blades in one direction effects radially outward movement (extension) of the blades, while axial translation of the pins against the angled slots of the blades in the reverse direction effects radially inward movement (retraction) of the blades. In a particular form, each blade has two angled slots while the control rod has two pins, one pin for each of the two angled slots of the blades. The two angled slots of each blade are situated skewed relative to each other. 
     In use, manipulation of the controller of the handle provides extension of the blades radially outward from the distal end beyond a diameter of the cannula after the distal end is clear of the cannula, and retract the blades into the distal end when use of the dynamic vertebral endplate preparation tool is finished. 
     Each blade may include a trough for collecting, and then removing, the shaven vertebral endplate material. In a particular form, cutouts or windows in a lower portion of the blade(s) aid in collection of shaved vertebral endplate material during use. When rotated, the blades(s) provide an almost 180° collection sweep outside of a longitudinal plane (axis) of the associated cannula. 
     Further aspects of the present invention will become apparent from consideration of the drawings and the following description of forms of the invention. A person skilled in the art will realize that other forms of the invention are possible and that the details of the invention can be modified in a number of respects without departing from the inventive concept. The following drawings and description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention and its features will be better understood by reference to the accompanying drawings, wherein: 
         FIG.  1    is a view of an exemplary vertebral endplate preparation tool with height adjustable blades for decorticating/shaving vertebra endplate material from vertebrae of a spine fashioned in accordance with the present principles; 
         FIG.  2    is an enlarged view of a middle to distal portion of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1   , depicting a bladed head thereof ready for extension and deployment from a cannula; 
         FIG.  3    is an enlarged view of a distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head shown in an extended but un-deployed position; 
         FIG.  4    is an enlarged view the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head shown in an extended and deployed position; 
         FIG.  5    is an enlarged view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head shown in an extended, deployed and rotated position; 
         FIG.  6    is an enlarged side view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head shown in an extended but un-deployed position; 
         FIG.  7    is an enlarged side view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head in an extended and deployed position; 
         FIG.  8    is an enlarged view of a controller of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1   ; 
         FIG.  9    is another enlarged view of the controller of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1   ; 
         FIG.  10    is an enlarged side view of the bladed head and distal end portion of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head in an un-deployed position; 
         FIG.  11    is an enlarged view of the bladed head and distal end portion of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head and distal end portion in an un-deployed position; 
         FIG.  12    is an enlarged side view of the bladed head and distal end portion of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head and distal end portion in a deployed position; 
         FIG.  13    is an enlarged side view of the bladed head and distal end portion of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head and distal end portion in an un-deployed position; 
         FIG.  14    is another enlarged side view of the bladed head and distal end portion of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  1    with the bladed head and distal end portion in an un-deployed position; 
         FIG.  15    is a view of another exemplary vertebral endplate preparation tool with height adjustable blades for decorticating/shaving vertebra endplate material from vertebrae of a spine fashioned in accordance with the present principles; 
         FIG.  16    is an enlarged view of a proximal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  15   , particularly showing the handle assembly; 
         FIG.  17    is an enlarged view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  15    with the blades shown retracted; 
         FIG.  18    is another enlarged view the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  15    with the blades shown retracted; 
         FIG.  19    is an enlarged generally side view of the distal end of the exemplary with height adjustable blades vertebral endplate preparation tool of  FIG.  15    with the blades shown extended; 
         FIG.  20    is an enlarged front side view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  15    with the blades shown extended; 
         FIG.  21    is a top view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  15    with the blades shown retracted; 
         FIG.  22    is an enlarged side sectional view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  15    with the blades shown retracted; 
         FIG.  23    is another enlarged side sectional view of the distal end of the exemplary vertebral endplate preparation tool of with height adjustable blades  FIG.  15    with the blades shown extended; 
         FIG.  24    is an enlarged view of a distal end of a further exemplary form of a vertebral endplate preparation tool with height adjustable blades for decorticating/shaving vertebral endplate material from vertebrae of a spine fashioned in accordance with the present principles with the blades thereof shown extended; 
         FIG.  25    is an enlarged view of a distal end of a still further exemplary form of a vertebral endplate preparation tool with height adjustable blades for decorticating/shaving vertebra endplate material from vertebrae of a spine fashioned in accordance with the present principles with blades of the distal end shown retracted; 
         FIG.  26    is an enlarged side view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  25    with the blades shown extended; and 
         FIG.  27    is an enlarged side sectional view of the distal end of the exemplary vertebral endplate preparation tool with height adjustable blades of  FIG.  25    with the blades shown extended. 
     
    
    
     For the purposes of promoting an understanding of the principles of the invention reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS.  1 - 14   , there is shown an exemplary medical instrument, generally designated  10  for decorticating or shaving vertebral endplate material from vertebrae of a spine, and optionally collecting and removing vertebral endplate material (not shown) from a vertebra (not shown) of a spine (not shown) during a surgical spine procedure, particularly, but not necessarily, using a cannula. The medical instrument  10  may be considered a vertebral endplate preparation tool with height adjustable (dynamic) blades and is made from one or more surgical grade materials. The vertebral endplate preparation tool with height adjustable blades  10  has a head  15  with blades  22 ,  24  designed to shave, collect, and remove vertebral disc material from a vertebral disc. The blades or shavers  22 ,  24  are movably retained in the head  15  such that each blade  22 ,  24  is able to extend or spread outward radially from the head, and retract or collapse inward radially from the head when actuated by the vertebral endplate preparation tool with height adjustable blades  10 . The radial spread of the blades  22 ,  24  is beyond the diameter of an associated cannula  80 , such as, but not necessarily, to the height of a vertebral disc space. Axial compression of the nose  20  to the base  46  of the head  15  that slidingly retain curved ends  50 ,  51  of the blade  22  and curved ends  48 ,  49  of the blade  24  provides radial expansion of the blades  22 ,  24 , while relieving axial compression provides radial contraction of the blades  22 ,  24 . 
       FIG.  1    depicts an overall view of the vertebral endplate preparation tool with height adjustable blades  10 . The vertebral endplate preparation tool with height adjustable blades  10  has a handle  12 , a controller  13  operably coupled to the handle  12 , a control shaft  14  operably coupled to the controller  14 , and a head  15  operably coupled to a distal end  18  of the control shaft  14 . The handle  12  is characterized by a gently curved body  16  sized to accommodate a hand (not shown) and includes several indentions  17   a,    17   b,    17   c,    17   d  each configured to accommodate a finger. Other configurations may be used. 
       FIG.  2    depicts a cannula construction  78  defined by a hollow longitudinal cannula  80  having a distal angled end  81 , an inner longitudinal bore  82 , and a proximal end  83  that is shown receiving a secondary cannula  85  having a receiving end  84 . The control shaft  14  is shown extended into the cannula construction  78  with the head  15  of the medical instrument  10  in a pre or post-deployment/expansion position at the distal angled end  81  of the cannula  80 . Through the use of telescoping cannula construction  78 , overall length of the cannula may be adjusted as desired. Other configurations may be used. 
       FIGS.  3 - 7    depict various views of the head  15  of the present vertebral endplate preparation tool with height adjustable blades  10  as it emerges from the end  81  of bore  82  of the cannula  80 . The overall shape of the head  15  is cylindrical which therefore defines arcs or arcuate portions about the circumference and/or the axial length of the overall cylindrical shape of the head. The head  15  has a nose  20  at a distal end of the head  15 , and a base  46  at a proximal end of the head  15 . The nose  20  is shaped generally as a flattened arch, but other shapes may be used. The base  46  is fixed to the control shaft  14 , which itself axially moves within the cannula  80 , as regulated by the controller  13  via the handle  12 . As seen in  FIGS.  3 ,  4 , and  6   , for example, the base  46  is situated at and fixed to the distal end of the control shaft  14 . A first blade or shaver  22  is situated axially between the nose  20  and the base  46  along an axial length of the outer diameter of the cylindrical shape of the head  15 , while a second blade or shaver  24  is situated axially between the nose  20  and the base  46  along another axial length of the outer diameter of the cylindrical shape of the head  15  and generally diametrically opposite the first blade  22 , the nomenclature first and second being arbitrary. The first blade  22  is held between the nose  20  and the base  46  such that the first blade  22  can move radially outward (expand) and radially inward (collapse) with respect to the head  15 . The first blade  22  further includes a concavity, groove, cutout, depression, scoop, or the like  26  that extends along the curved longitudinal edge of the first blade  22  which is configured to receive and/or collect shaved vertebral disc material. A window  23  is provided in the first blade  22  that aids in collection of shaved vertebral disc material. The second blade  24  is also held between the nose  20  and the base  46  such that the second blade  24  can move radially outward (expand) and radially inward (collapse) with respect to the head  15 . The second blade  24  further includes a concavity, groove, cutout, depression, scoop, or the like (not seen) that extends along the curved longitudinal edge of the second blade  24 , which is configured to receive and/or collect shaved vertebral disc material in like manner and form as scoop  26 . A window  25  is provided in the second blade  24  that aids in collection of shaved vertebral disc material. Axial motion is controlled through the control shaft  14  from the controller  13  through the handle  14 . 
     The nose  20  has a collar or skirt  35  (collectively, collar) that extends axially from the proximal end of the nose  20  a distance towards the base  46 . One side of the collar  35  has a first, preferably, but not necessarily, angled slot  40  that is configured to movably or slidingly receive a first angled side  50  of the blade  22 . The first slot  40  of the nose  20  and the first angled side  50  of the blade  22  are preferably, but not necessarily, formed between them as a dovetail joint. Another side of the collar  35  has a second, preferably, but not necessarily, angled slot  41  that is configured to movably or slidingly receive a first angled side  48  of the second blade  24 . The second slot  41  of the nose  20  and the first angled side  48  of the second blade  24  are preferably, but not necessarily, formed between them as a dovetail joint. 
     The base  46  has a first, preferably, but not necessarily, angled slot  44  that is configured to movably or slidingly receive a second angled side  51  of the blade  22 . The first slot  44  of the base  46  and the second angled side  51  of the blade  22  are preferably, but not necessarily, formed between them as a dual angled dovetail joint/channels. Another side of the base  46  has a second, preferably, but not necessarily, angled slot  45  that is configured to movably or slidingly receive a second angled side  49  of the second blade  24 . The second slot  44  of the base  46  and the second angled side  49  of the second blade  24  are preferably, but not necessarily, formed between them as a dual angled dovetail joint/channels. Through axial compression and relief of axial pressure of the nose  20  axially towards the base  46  and axially away from the base  46 , the first and second blades  22 ,  24  are caused to move relative to the nose  20  and the base  46  because of the slanted ends of the blades and the slots of the nose and the base. Axial pressure of the nose  20  towards the base  46  causes the first and second blades  22 ,  24  to slide up, out and along (spread out or expand from the head  15 ) the dovetail configurations between the ends of the blades and the slots of the nose and base, while relief of axial pressure of the nose  20  away from the base  46  causes the first and second blades  22 ,  24  to slide down, in and along (collapse or compress into the head  15 ) the dovetail configurations between the ends of the blade and the slots of the nose and the base. 
     The head  15  also has an actuator  30  that extends from the collar  35  of the nose  20  towards the base  46 . The actuator  30  provides a connection for controlling axial movement of the nose  20  relative to the base  46  for controlling blade expansion/contraction. While not seen in the figures, the head  15  may include a second actuator situated opposite to the actuator  30  that would mimic the actuator  30 . The actuator  30  includes a first arm  31  that extends axially from the end of the collar  35  and is connected to one side of a first plate  32 . A second arm  33  extends axially from a second side of the first plate  32  towards and through a channel  47  in the side of the base  46 . The second arm  33  further extends axially through and is retained in a groove  34  formed in an outside surface of the control shaft  14 . As signified by the double-headed arrow in  FIGS.  3 ,  4  and  6   , the actuator  30  is able to axially translate relative to the base  46  and control shaft  14 . This is accomplished by a translational shaft  64  of the control shaft  14  that is connected to the actuator  30  and which can axially move relative to the body of the control shaft  14  through the controller  13 . When the translational shaft  64  is axially translated in one direction, the actuator  30  axially pulls against the nose  20  to squeeze (axially translate) it towards the base  46  thereby pushing out (expanding) the first and second blades  22 ,  24 . Axial translation of the translational shaft  64  in the opposite axial direction pushes the nose  20  axially away from the base  64  to collapse the first and second blades  22 ,  24  into the head  15 . 
       FIGS.  3 - 5    depict expansion of the blades  22 ,  24  from the head  15  as the head  15  emerges (is axially translated from) the cannula  80 .  FIG.  6    depicts a side view of the head  15  with the blades  22 ,  24  un-expanded, while  FIG.  7    depicts a side view of the head  15  with the blades  22 ,  24  expanded.  FIGS.  10 - 14    depict various views of the head  15  with the blade  22 ,  24  expanded and un-expanded showing the control shaft  14  and the translational shaft  64  relative to the actuator  30  and blades  22 ,  24 . 
       FIGS.  8 - 9    depict two views of the controller  13 . The controller  13  has a body  56  connected to the handle  12  via a neck  58 . The handle  12  is operably coupled to a control knob  60  for axially moving the control shaft  14  within the cannula  80 . A toothed tab  59  is slidingly retained by the body  13  and when slid into a locked position ( FIG.  9   ) where the teeth thereof meet end  61  of the control knob  60 . Thus, control knob  60  is locked in orientation via sliding the lock tab  59  down from the open position (shown in  FIG.  8   ) to a locked position (shown in  FIG.  9   ) which will prevent (e.g., lock) the blades  22 ,  24  from collapsing into the head  15  when in use. 
     The cannula  80  extends from the neck  57  of the body  56  of the controller  13  and may include a head position indicator  52  for indicating status of the head  15 . The indicator  52  includes an opening or window  53  formed in the cannula  80  with demarcations  54  about the opening  53  to indicate axial position of the head  15  relative to the opening  81  of the cannula  80 . The control shaft  14  has a mark  55  that will move axially within the opening  53  with axial movement of the control shaft  14 , as signified by the double-headed arrow in  FIG.  8   . 
     Referring to  FIGS.  15 - 23   , there is shown another form of a vertebral endplate preparation tool with height adjustable blades generally designated  110  for decorticating/shaving vertebral endplate material from vertebrae (not shown) of a spine (not shown) during a surgical procedure. The medical instrument  110  may also be configured and used for collecting and removing the shaved vertebral endplate material. The medical instrument  110  is preferably, but not necessarily, used with a cannula or endoscope during a minimally invasive or micro invasive spine procedure. The vertebral endplate preparation tool with height adjustable blades  110  is made from one or more surgical grade materials. In general, the vertebral endplate preparation tool with height adjustable blades  110  has a proximal end/end assembly  111  with a handle  112  that is connected to a proximal end of a controller  113  via a neck  118 , a shaft assembly  114  connected at a proximal end thereof to a distal end of the controller  113  via a collar  115 , and a head  122  at a distal end  120  of the shaft assembly  114 , the head  122  having a nose  121  and a blade assemblage/assembly  133  having first and second blades  136 ,  137  designed to decorticate or shave vertebral endplate material from a vertebra (not shown), the nomenclature first and second being arbitrary here and throughout if not specifically indicated otherwise. The vertebral endplate preparation tool with height adjustable blades  1110  may also be configured to collect and remove the shaved vertebral endplate material and is so configured as shown. The first and second blades  136 ,  137  are movably retained in the head  122  such that each blade  136 ,  137  is able to extend or spread outward radially from the head  122 , and retract or collapse inward radially from the head  122  when actuated by the vertebral endplate preparation tool with height adjustable blades  1110 . The radial spread of the first and second blades  136 ,  137  is beyond the diameter of an associated cannula, access tube, endoscope or the like, such as, but not necessarily, to the height of a vertebral disc space (not shown), such that the medical instrument  1110  may decorticate or shave vertebral endplate material from adjacent vertebra within the disc space if desired, rather than each vertebral endplate of adjacent vertebrae separately. 
     Referring to  FIG.  16   , the handle  112  is characterized by a gently curved body  116  sized to accommodate a hand (not shown) and includes several indentions  117   a,    117   b,    117   c,    117   d  each configured to accommodate a finger. Other configurations may be used. The controller  113  has a frame defined by upper and lower frame members  128   a,    128   b  that project from the neck  118  of the handle  112 . The upper and lower frame members  128   a,    128   b  are connected to a front frame member  129  that connects to the collar  115 . The controller  113  has a rotatable control knob  130  that adjusts the extension and contraction of the first and second blades  136 ,  137  through the handle  112  that is operably coupled to the control knob  160  for axially moving the control shaft  114  within the cannula  180 . A toothed tab  175  is slidingly retained by the controller  113 . In  FIG.  16   , the toothed tab  175  is in an unlocked position axially away from the rotatable control knob  160  such that the toothed tab  175  is not engaged with the rotatable control knob  160 . When the toothed tab  175  is axially slid into a locked position (not shown) where the teeth thereof meet the toothed end  174  of the rotatable control knob  160 , rotation of the handle  112  rotates the toothed tab  175  which rotates the rotatable control knob  160  to effect blade extension and retraction through the shaft assembly  114 . 
     The shaft assembly  114  includes a generally hollow, longitudinal tube  119  having upper and lower flats along its longitudinal length and an internal control rod (not seen) that extends at a proximal end thereof from the rotatable control knob  160  to and operably connected with the blade assemblage  133  of the head  122  at a distal. The proximal end of the internal control rod is externally threaded. The rotatable control knob  160  has an internally threaded bore (not seen) that receives the externally threaded proximal end of the internal control rod of the shaft assembly  114 . Rotation of the rotatable control knob  160  axially moves the internal control rod of the shaft assembly  114 , the direction of axial movement of the internal control rod depending on the rotational direction of the rotatable control knob  160  through threaded engagement. As explained further below, axial movement of the internal control rod effects extension and retraction of the first and second blades  136 ,  137  from the head  122 . The longitudinal tube  119  includes a blade height indicator  124  that provides a visual indication of blade height from the head  122 . The height indicator  124  has an opening or window  125  formed in the longitudinal tube  119  with demarcations  126  about the opening  125  to indicate height position of the first and second blades  136 ,  137  from the head  122 . The internal control rod  114  has a marker  126  that will move axially within the opening  125  with axial movement of the internal control rod. 
       FIGS.  17 - 21    depict various views of the head  122  and blade assemblage  133  of the present vertebral endplate preparation tool with height adjustable blades  110 . The overall shape of the head  122  is generally cylindrical. The head  122  has a nose  121  at a distal end thereof, with a first surface  159  on a first lateral side, and a second surface  171  on a second lateral side. The first lateral surface  159  has a first arm  158  extending axially to the distal end of the longitudinal tube  119  with a first rear tail  160  received in a first axial slot  156  of the distal end of the longitudinal tube  119 . The second lateral surface  171  has a second arm  170  extending axially to the distal end of the longitudinal tube  119  with a second rear tail  172  received in a second axial slot  168  of the distal end of the longitudinal tube  119 , the first and second arms  158 ,  170  and the first and second rear tails  160 ,  172  being preferably, but not necessarily, opposite one another. The first and second arms  158 ,  170  and thus the nose  121  of the head  122  is longitudinally axially movable relative to the longitudinal tube  119 , since the internal control rod of the shaft assembly  114  is attached thereto. Axial movement of the internal control rod towards the controller  113  pulls the nose  121  and arms  158 ,  170  to compress against the first and second blades  136 ,  137  thereby effecting blade extension through mutual dovetail features of the first and second blades  136 ,  137  and the distal end  122  along with slanted first and second channels  143 ,  152  of the first and second blades  136 ,  137  respectively, wherein the amount of axial movement determines radial height (extension) of the first and second blades  136 ,  137 . Axial movement of the internal control rod of the shaft assembly  114  away from the controller  113  pushes the nose  121  and arms  158 ,  170  releases compression against the first and second blades  136 ,  137  to effect retraction of the first and second blades  136 ,  137 . 
     The first blade  136  is situated axially between the nose  121  and the distal end of the longitudinal tube  119  of the shaft assembly  114 . The first blade  136  is generally trapezoidal in overall shape with a gently curved outer longitudinal edge. As best discerned in  FIGS.  19  and  20   , the first blade  136  has a first slanted front  138  with at least a generally dovetail configuration and a first slanted rear  139  with at least a generally dovetail configuration. The gently curved outer longitudinal edge of the first blade  136  has a groove or channel  141  that extends between a first front end  140  and a first rear end  142  that is configured to receive and/or collect shaved vertebral endplate material. The groove  141  is on one side of the gently curved outer longitudinal edge of the first blade  136 , while the opposite side of the gently curved outer longitudinal edge does not have a groove. As such, the first blade  136  is configured to be rotated in one direction (here, a clockwise direction) in order to shave vertebral endplate material from a vertebra (not shown). A first front cutout  144  and a first rear cutout  145  is provided in the first blade  136  that aid in collection of shaved vertebral endplate material. Situated between the first front cutout  144  and the first rear cutout  145  is a first angled slot  143 . As best discerned in  FIGS.  22  and  23   , the first angled slot  143  is slanted from a distal position to the proximal direction. The first angled slot  143  is sized to receive a pin  162  that is held between and extends from the first arm  158  to the second arm  170 . A first spacer  161  is provided between the first arm  158  and the first blade  136 . 
     The second blade  137  is situated axially between the nose  121  and the distal end of the longitudinal tube of the shaft assembly  114 . The second blade  137  is generally trapezoidal in overall shape with a gently curved outer longitudinal edge. As best discerned in  FIGS.  19  and  20   , the second blade  137  has a second slanted front  148  with at least a generally dovetail configuration and a second slanted rear  149  with at least a generally dovetail configuration. The gently curved outer longitudinal edge of the second blade  137  has a groove or channel (not seen) that extends between a second front end (not seen) similar to the first front end  140  of the first blade  136 , and a second rear end (not seen) similar to the first rear end  142  of the first blade  136 , that is configured to receive and/or collect shaved vertebral endplate material. The groove (not seen) is on one side of the gently curved outer longitudinal edge of the second blade  137 , while the opposite side of the gently curved outer longitudinal edge does not have a groove. The groove (not seen) of the second blade  137  is on the side of the second blade  137  such that rotation in the same direction as the first blade  136  (here, a clockwise direction) provides shaving of vertebral endplate material from a vertebra (not shown). A second front cutout  153  and a second rear cutout  154  is provided in the second blade  137  that aid in collection of shaved vertebral endplate material. Situated between the second front cutout  153  and the second rear cutout  154  is a second angled slot  152 . The second angled slot  152  is slanted from a distal position to the proximal direction in like manner to the first angled slot  143 . The second angled slot  152  is sized to receive the pin  162  that is held between and extends from the first arm  158  to the second arm  170 . A second spacer  173  is provided between the first arm  158  and the second blade  137 . 
     The proximal end of the nose  121  has a first angled lower slot  166  that is configured as a dovetail slot to movably or slidingly receive the first angled front  138  of the first blade  136 , whereby the first lower angled slot  166  and the first angled front  138  together define a dovetail joint. Other manners of connection may be used and are contemplated. The distal end of the longitudinal tube  119  has a second angled lower slot  167  that is configured as dovetail slot to movably or slidingly receive the first angled rear  139  of the first blade  136 , whereby the second angled lower slot  167  and the first angled rear  139  together define a dovetail joint. Other manners of connection may be used and are contemplated. The slant of the first angled lower slot  166 /first angled front  138  of the first blade  136  pair dovetail joint, and the slant of the second angled lower slot  167 /first angled rear  139  of the first blade  36  pair dovetail joint are opposite one another, whereby axial compression against the first angled front  138  and the first angled rear  139  of the first blade  136  causes, at least in part, the first blade  136  to extend radially outward from the distal end  122 . The pin  162  is connected to the distal end of the internal control rod. As the pin  162  is pulled axially towards the proximal end/end assembly  111 , the first angled slot  143  of the first blade  136  rides against the pin  162  during extension. Reverse axial movement of the internal control rod pushes the pin  162  against the first angled slot  143  such that the first blade  136  is retracted. The amount of axial movement in the proximal direction determines the amount of blade extension. 
     The proximal end of the nose  121  further has a first angled upper slot  164  that is configured as a dovetail slot to movably or slidingly receive the second angled front  148  of the second blade  137 , whereby the first angled upper slot  164  and the second angled front  148  together define a dovetail joint. Other manners of connection may be used and are contemplated. The distal end of the longitudinal tube  119  has a second angled upper slot  165  that is configured as dovetail slot to movably or slidingly receive the second angled rear  149  of the second blade  137 , whereby the second angled upper slot  165  and the second angled rear  149  together define a dovetail joint. Other manners of connection may be used and are contemplated. The slant of the first angled upper slot  164 /second angled front  148  of the second blade  137  pair dovetail joint, and the slant of the second angled upper slot  165 /second angled rear  149  of the second blade  137  pair dovetail joint are opposite one another, whereby axial compression against the angled ends  148 / 149  of the second blade  137  causes, at least in part, the second blade  137  to extend radially outward from the distal end  122 . The pin  162  is connected to the distal end of the internal control rod. As the pin  162  is pulled axially towards the proximal end/end assembly  111 , the second angled slot  152  of the second blade  137  rides against the pin  162  during extension. Reverse axial movement of the internal control rod pushes the pin  162  against the second angled slot  152  such that the second blade  137  is retracted. The amount of axial movement in the proximal direction determines the amount of blade extension. 
       FIGS.  22  and  23    show the extension of the first and second blades  136 ,  137  from the distal end  122 , with one lateral side removed for clarity. In  FIG.  22   , the first and second blades  136 ,  137  are fully retracted. This is the position of the blades when the distal end  122  is inserted through an access tube (not shown). In  FIG.  23   , the first and second blades  136 ,  137  are fully extended. As the internal control rod is caused to axially move into the controller  113 , the pin  162 , being connected to the internal control rod, pulls the pin  162  and the nose  121  axially towards the controller  113 . This causes the first and second blades  136 ,  137  to extend. The amount of extension is controlled by the controller  113 , and visually indicated by the indicator  124  on the longitudinal tube  119  of the shaft assembly  114 . Axial motion is signified by the double-headed arrow. 
     In operation, the distal end or shaving head  122  of the vertebral endplate preparation tool with height adjustable (dynamic) blades  110  is inserted down an access tube. Once clear of the distal end of the access tube, the decorticating/shaving head  122  is inserted into the vertebral disc space. The blades are extended by rotation of the rotatable control knob  130  via the handle  112  to a particular radial height necessary for the particular disc space. Rotation of the blades then effects shaving of vertebral endplate material. 
     Referring to  FIG.  24   , there is depicted another form of a distal end/decorticating head  122  for the vertebral endplate preparation tool with height adjustable (dynamic) blades  110  dynamic shaver  110  of  FIG.  15    designated  122   a.  The addition of the designation “a” after a callout number indicates an element or component that is different in some manner than the element or component of the vertebral endplate preparation tool with height adjustable blades  110  of  FIGS.  15 - 23   . All other elements or components without the additional designation of “a”, or are not shown in  FIG.  24   , are the same in form and function as the vertebral endplate preparation tool with height adjustable (dynamic) blades  110  of  FIGS.  15 - 23   . Essentially, the shaving or decorticating head  122   a  has dovetail joints between the nose  121 , the distal end of the internal control rod of the shaft assembly  114 , and the first and second blades  136   a ,  137   a  of the shaving/decorticating head  122   a  with a different profile than the dovetail joints between the nose  121 , the distal end of the internal control rod of the shaft assembly  114 , and the first and second blades  136 ,  137  of the vertebral endplate preparation tool with height adjustable blades  110 . Thus, the first angled lower slot  166   a,  the second angled lower slot  167   a,  the first angled front  138   a,  and the first angled rear  139   a  form a dovetail joint that allows the ramped surfaces between them (which force extension) includes a side profile that allows the height of the first blade  136   a  to be controllably decreased when operated in the opposite direction (blade retraction direction). As well, the first angled upper slot  148   a,  the second angled upper slot  149   a,  the second angled front  148   a,  and the second angled rear  149   a  form a dovetail joint that allows the ramped surfaces between them (which force extension) includes a side profile that allows the height of the second blade  137   a  to be controllably decreased when operated in the opposite direction (blade retraction direction). 
     Additionally, the first blade  136   a  has a pin slot  152   a  situated distally, and the second blade  137   a  has a pin slot (not seen in  FIG.  24   ) also situated distally. The pin  162   a  of the first and second lateral arms  158 ,  170  is further situated distally. The first blade  136   a  has a middle opening  144   a.  The second blade  137   a  also has a middle opening  153   a.  Extension and retraction of the first and second blades  136   a,    137   a  operates in the same manner as the vertebral endplate preparation tool with height adjustable blades  110 . 
     Referring to  FIGS.  25 - 27   , there is depicted a further form of a vertebral endplate preparation tool with height adjustable (dynamic) blades  110  having a different distal end/shaving/decorticating head designated  180 . The vertebral endplate preparation tool with height adjustable (dynamic) blades  110  of  FIGS.  25 - 27    is different from the vertebral endplate preparation tool with height adjustable (dynamic) blades  110  of  FIGS.  15 - 24    and the variation of the shaving head  22   a  of  FIG.  24    because of the manner of how the shaving/decorticating head  80  operates, and thus configured. The shaving head  80  uses pins and slanted slots to effect extension and retraction rather than, or in addition to, dovetail joints. Other than the shaving head  80 , the vertebral endplate preparation tool with height adjustable blades  110  of  FIGS.  25 - 27    has, at least generally, the same elements, components, and functionality as the vertebral endplate preparation tool with height adjustable blades  110  of  FIGS.  15 - 24   , including the nose  121 , the first and second lateral arms  158 ,  170  that extend from the nose  121  to the slots  156  and  168 , respectively of the longitudinal tube  119 , and connection pin  163 . 
     The first blade  182  of the shaving head  180  has a first slanted rear  189  and a first slanted front  190 , a central opening  186 , a first angled rear slot  187 , and a first angled front slot  188 . The distal end of the longitudinal tube  119  has a first upper slanted channel  184  that receives the first slanted rear  189  of the first blade  182 , while the proximal end of the nose  121  has a second upper slanted channel  185  that receives the first slanted front  190  of the first blade  182 . A proximal guide pin  1100  extends from and through the first and second arms  158 ,  170  and the first angled rear slot  187  of the first blade  182 . A distal guide pin  1101  extends from and through the first and second arms  158 ,  170  and the first angled front slot  188  of the first blade  182 . The slant of the first angled front slot  188  and the slant of the first angled rear slot  187  are opposite. 
     The second blade  183  of the shaving head  180  has a second slanted rear  197  and a second slanted front  198 , a central opening  194 , a second angled rear slot  195 , and a second angled front slot  196 . The distal end of the longitudinal tube  119  has a first lower slanted channel  191  that receives the second slanted rear  197  of the second blade  183 , while the proximal end of the nose  121  has a second lower slanted channel  192  that receives the second slanted front  198  of the second blade  183 . The proximal guide pin  1100  extends from and through the first and second arms  158 ,  170  and the second angled rear slot  195  of the second blade  183 . The distal guide pin  1101  extends from and through the first and second arms  158 ,  170  and the second angled front slot  196  of the second blade  183 . The second blade  183  also has a groove  199  for shaving and/or receiving vertebral endplate material. While not shown, the first blade  182  has a like groove. The slant of the second angled front slot  196  and the slant of the second angled rear slot  195  are opposite. 
       FIG.  25    depicts the first and second blades  182 ,  183  in a retracted position wherein the first and second arms  158 ,  170  are axially forward of the longitudinal tube  119 .  FIGS.  26  and  27    depict the first and second blades  182 ,  183  in an extended position wherein the first and second arms  158 ,  170  are axially rearward. In this embodiment, when the proximal and distal guide pins  1100 ,  1101  are caused to axially move through axial translation of the internal control rod (not seen) of the shaft assembly  114 , they pull (axial translation towards the proximal end/controller  113 ) or push (axial translation towards the distal end/shaving head  122 ) against the angled slots  187 ,  188 ,  195 ,  196  causing the first and second blades to translate up (blade extension) or down (blade retraction). Axial movement is represented by the double-headed arrows. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only a preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention.