Abstract:
A spinal disc replacement surgical instrument includes a first contacting member positionable along an endplate of a first vertebra and a second contacting member positionable along an endplate of second vertebra. The second contacting member is moveable relative to the first contacting member. A handle assembly is coupled to the first contacting member and the second contacting member. At least one actuating member is positioned between the first contacting member and the second contacting member. The at least one actuating member is moveable by the hand assembly from a first position, wherein the first and second contacting members include an unexpanded configuration relative to one another for insertion in the spinal cavity, to a second position providing expanded configuration relative to one another. The actuating member is configured to displace at least one of the first contacting member and the second contacting member away from each other to move the first contacting member and the second contacting member between the first position and the second position. The first contacting member has a first distal end and the second contacting member has a second distal end. The first end has a first end shape configured to conform to a shape of the first vertebra and the second end has a second end shape configured to conform to a shape of the second vertebra. The first end shape and the second end shape are different shapes.

Description:
TECHNICAL FIELD 
   The present invention relates generally to the field of surgery and medical implants, and more particularly, to surgical tools and methods for use in positioning an intervertebral device between vertebral members of a patient. 
   BACKGROUND OF THE INVENTION 
   The human spine is a biomechanical structure with thirty-three vertebral members, and is responsible for protecting the spinal cord, nerve roots and internal organs of the thorax and abdomen. The spine also provides structure support for the body while permitting flexibility of motion. A significant portion of the population will experience back pain at some point in their lives resulting from a spinal condition. The pain may range from general discomfort to disabling pain that immobilizes the individual. Back pain may result from a trauma to the spine, be caused by the natural aging process, or may be the result of a degenerative disease or condition. 
   Procedures to remedy back problems sometimes require correcting the distance between vertebral members by inserting an intervertebral device (e.g., spacer) between the members. The spacer, which is carefully positioned within the disc space and aligned relative to the vertebral members, is sized to position the vertebral members in a manner to alleviate the patient&#39;s back pain. 
   Further, the intervertebral device is preferably designed to facilitate insertion into a patient. That is, the shape and size of the device are designed to provide for minimal intrusion to a patient during insertion, but still be effective post-insertion to alleviate the pain and provide maximum mobility to the patient. A spinal cavity for receiving the intervertebral device must be prepared prior to inserting the device therein. 
   Thus, a need exists for enhanced surgical instruments and methods for positioning an intervertebral device between vertebral members of a patient, and for enhanced surgical instruments and methods for preparing a spinal cavity to receive such an intervertebral device. 
   SUMMARY OF THE INVENTION 
   The present invention provides, in an aspect, a spinal disc replacement surgical instrument which includes a first contacting member positionable along an endplate of a first vertebra. A second contacting member is positionable along an endplate of a second vertebra. The first vertebra and the second vertebra define the spinal cavity. The second contacting member is moveable relative to the first contacting member. A handle assembly is coupled to the first contacting member and the second contacting member. At least one actuating member is positioned between the first and second contacting members. The at least one actuating member is moveable by the hand assembly from a first position, wherein the first and second members include an unexpanded configuration relative to one another for insertion in the spinal cavity, to a second position providing an expanded configuration. The actuating member is configured to displace at least one of the first contacting member and the second contacting member away from each other to move the first contacting member and the second contacting member between the first position and the second position. The first contacting member has a first distal end and the second contacting member has a second distal end. The first end has a first end shape configured to conform to a shape of the first vertebra and the second end has a second end shape configured to conform to a shape of the second vertebra. The first end shape and the second end shape are different shapes. 
   The present invention provides, in another aspect, a spinal disc replacement surgical instrument which includes a first contacting member positionable along an endplate of a first vertebra. A second contacting member is positionable along an endplate of a second vertebra. The first vertebra and the second vertebra define a spinal cavity. The second contacting member is moveable relative to the first contacting member. The first contacting member is connected to a handle assembly by a first extending arm and the second member is connected to the handle assembly by a second extending arm. An adjustable depth regulator extends from the handle assembly toward the first member and the second member. The adjustable depth regulator is located at least partially longitudinally offset relative to at least one of the first arm and the second arm. The adjustable depth regulator includes at least one stop member positionable in contact with one of the first vertebra and the second vertebra to limit an insertion depth of the first contacting member and the second contacting member in the spinal cavity. 
   The present invention provides, in a further aspect, a spinal disc replacement surgical instrument which includes a first member positionable along an endplate of a first vertebra and a second member positionable along an endplate of a second vertebra. The first vertebra and the second vertebra define a spinal cavity. The second member is moveable relative to the first member. The first member and the second member are moveable between an unexpanded configuration relative to one another for insertion in the spinal cavity and an expanded configuration relative to one another. The handle assembly includes a distal end coupled to the first member and the second member. The handle assembly includes a proximal end connectable to a releaseable handle. The proximal end includes a handle assembly cavity for receiving an end of the handle and the handle assembly cavity includes an interior surface connectable to the handle. The handle assembly cavity includes an impactable head configured to receive an impact and to transfer the impact to the handle assembly and to at least one of the first contacting member and the second contacting member. 
   The present invention provides, in yet another aspect, a method for use in spinal disc replacement which includes positioning a first contact member of a surgical instrument along an endplate of first vertebra. A second contacting member of the surgical instrument is positioned along an endplate of a second vertebra. The first vertebra and the second vertebra define a spinal cavity. The first contacting member is coupled to the second contacting member by a handle assembly of the surgical instrument. At least one actuating member of the surgical instrument is positioned between the first contacting member and the second contacting member. The actuating member is moved from a first position, wherein the first contacting member and the second contacting member include an unexpanded configuration relative to one another for insertion in the spinal cavity, to a second position, wherein the first contacting member and the second contacting member include an expanded configuration relative to one another. The first contacting member has a first distal end and the second contacting member has a second distal end. The first distal end has a first shape configured to conform to a shape of the first vertebra and a second end has a second end shape configured to conform to a shape of the second vertebra. The first end shape and the second end shape are different shapes. 
   The present invention provides, in yet a further aspect, a method for use in spinal disc replacement which includes positioning a first contacting member of a surgical instrument along an endplate of a first vertebra of a spinal cavity. A second contacting member of the surgical instrument is positioned along an endplate of the second vertebra. The first vertebra and the second vertebra define a spinal cavity. The first contacting member is connected to a handle assembly of the surgical instrument by a first extending arm and the second contacting member is connected to the handle assembly by a second extending arm. An adjustable depth regulator is extended from the handle assembly toward the first contacting member and the second contacting member such that the adjustable depth regulator is located at least partially longitudinally offset relative to at least one of the first arm and the second arm. The adjustable depth regulator is contacted with one of the first vertebra and the second vertebra to limit an insertion depth of the first contacting member and the second contacting member into the spinal cavity. 
   The present invention provides, in another aspect, a method for use in replacing a spinal disc which includes providing a spinal disc replacement surgical tool having a handle assembly with a distal end coupled to a first contacting member positionable along a endplate of a first vertebra defining a spinal cavity and a second contacting member positionable along an endplate of a second vertebra defining the spinal cavity. The handle assembly includes a proximal end having a handle assembly cavity connectable to a releasable handle. An impactable head in the handle assembly is impacted to cause movement of the surgical tool toward the spinal cavity. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a perspective view of one embodiment of a spinal disc replacement surgical instrument with a keel cutter in a top slot of the instrument, according to an aspect of the present invention; 
       FIG. 2  is a side elevational view of a portion of the instrument of  FIG. 1  showing a first contacting member and a second contacting member in an unexpanded configuration in accordance with an aspect of the present invention; 
       FIG. 3  is a side elevational view of a portion of the instrument of  FIG. 1  showing a first contacting member and a second contacting member in an expanded configuration, in accordance with an aspect of the present invention; 
       FIG. 4  is a top perspective view of a portion of the instrument of  FIG. 1  showing a first extending arm, a handle assembly, and a controlling mechanism, in accordance with an aspect of the present invention; 
       FIG. 5  is a bottom perspective view of the instrument of  FIG. 1  further including a keel cutter in a bottom slot of the instrument, in accordance with an aspect of the present invention; 
       FIG. 6  is a perspective view of a proximal end of the handle assembly of the instrument of  FIG. 1 , in accordance with an aspect of the present invention; and 
       FIG. 7  is a perspective view of the proximal end of the handle assembly of  FIG. 6  further including a releasable handle attached thereto, in accordance with an aspect of the present invention. 
   

   DETAILED DESCRIPTION 
   In accordance with the principles of the present invention, a spinal disc replacement surgical instrument, and methods for use in implanting a prosthetic disc in a spinal cavity, are provided. 
   As depicted in  FIG. 1 , a surgical tool  10  includes a first arm  100 , a second arm  200 , and a handle assembly  300  connected to first arm  100  and second arm  200 . First arm  100  and second arm  200  are hingedly and/or pivotally connected to handle assembly  300  to allow the arms to be separated from one another and moved toward one another. More specifically, first arm and second arm  200  are movable to a collapsed position ( FIG. 2 ) such that a front end (i.e., distal end)  20  of tool  10  may be positionable in a space between adjacent vertebra (not shown) defining a spinal cavity (not shown). The arms may be remotely manipulated by a user (e.g., a surgeon) to increase a separation distance and/or angulation between endplates of adjacent vertebra defining such a spinal cavity, as depicted for example in  FIG. 3 . The distance between the arms may be increased (or decreased) by the manipulation of handle assembly  300  thereby adjusting a distance between the vertebra, as further described below. 
   First arm  100  is connected to a first contacting member  110  and second arm  200  is connected a second contacting member  210 . Alternatively, each arm and respective contacting member may be formed integral to one another. The members may be formed of plates having opposite faces positionable against endplates of adjacent vertebra (not shown) defining a spinal cavity (not shown) to provide a separation force to the endplates when manipulated with handle assembly  300 . Other forms for contacting members  110 ,  210  are also contemplated, including single blades, U-shaped blades, or other suitable structure for contacting the adjacent vertebral endplate. As depicted in  FIGS. 1-3  and  5 , a distal end of first contacting member  110  and a distal end of second contacting member  210  may have different shapes and may extend distally (i.e., in a direction away from handle assembly  300 ) a different distance relative to one another. The contacting members may be tapered toward the arms at an intersection point between each arm and each contacting member. Opposite sides of the contacting members may be substantially parallel to a longitudinal axis of the contacting members and/or the arms. For example, first contacting member  110  may have a square front end  117  and second contacting member  210  may have a rounded front end  217  as best depicted in  FIG. 5 . 
   Also, the different shapes of the front ends (e.g., front ends  117  and  217 ) allow a user to more readily determine the correct orientation of the tool, i.e., which side (e.g., first contacting member  110 ) is to be used adjacent an upper vertebra and which slide (e.g., second contacting member  210 ) is to be used adjacent a lower vertebra. In the example depicted in the figures, a user would know from the square shape of first contacting member  110  that tool  10  is configured to be inserted such that first contacting member  110  is on a top (i.e., superior) side of the tool and is configured to abut an upper vertebra of a spinal cavity. Similarly, the user would know from the rounded or curved shape of second contacting member  210  that tool  10  is configured to be inserted such that second contacting member  210  is on a bottom (i.e., inferior) side of the tool and is configured to abut a lower vertebra of the spinal cavity. Also, the distal ends of the contacting members could be formed of any shape which conforms to the shape of a vertebra which it will abut, or come in close proximity to. For example, it may be necessary to use particular surgical instruments (e.g., tool  10 ) having contacting members with different shaped ends according to which vertebra in a spinal column needs to be replaced. Further, the contacting members and/or arms may be releasably connectable to each other and/or the remainder of tool  10  to allow such varying shapes and/or thicknesses of the contacting members and/or arms to be utilized. 
   A depth adjustment system  400  is connected to handle assembly  300  and second contacting member  210  as depicted in  FIGS. 1 ,  4  and  5 . Adjustment system  400  includes a depth regulator or stopper  410  protruding from a bottom side of a connecting member  420  movably attached to an underside  215  of second contacting member  210 . Depth stopper  410  may be connected, or integral, to a connecting member  420 . Depth stopper  410  is configured (e.g., shaped and dimensioned) to inhibit front end  20  of tool  10  from proceeding past a desired point into a spinal cavity. More specifically, depth stopper  410  may abut an exterior surface (i.e., a surface of a vertebra outside the spinal cavity, (not shown) of a bottom vertebra (not shown) defining a spinal cavity (not shown)) such that depth stopper  410  remains outside the spinal cavity abutting the exterior surface of the bottom vertebra defining the cavity. 
   Upwardly extending portions  412  of connecting member  420  may extend through apertures  212  in second contacting member  210  as depicted in  FIGS. 1 ,  2  and  5 . Apertures  212  are elongated in a longitudinal direction relative to second contacting member  210  and tool  10  such that upwardly extending portions  412  may move in a longitudinal direction within aperture  212 . Connecting member  420  connects second contacting member  210  to a controlling mechanism configured to cause the movement of connecting member  420  and depth stopper  410 . Such movement allows the adjustment of the depth to which front end  20  of tool  10  may extend into a spinal cavity. 
   For example, such a controlling mechanism may include a rotatable knob or thumbwheel  450  having an internal thread (not shown) configured to mate with threads (not shown) on an outer surface of connecting member  420 , as depicted in  FIGS. 1 and 4 . The rotation of thumbwheel  450  may cause connecting member  420  to move toward, or away from, rounded front end  217  of second contacting member  210 . For example, the rotation of thumbwheel  450  in a clockwise direction may cause connecting member  420  to move toward rounded front end  217  until rotation is stopped at a position which corresponds to a minimum depth of the tool in a spinal cavity. Rotation of thumbwheel  450  in a counterclockwise direction may cause movement of the connecting member and the depth stopper away from rounded front end  217  to a maximum depth of tool  10  in the spinal cavity. As noted above, the movement of connecting member  420 , along with depth stopper  410 , controls the extent to which tool  10  (i.e., front end  20 ) may extend into a spinal cavity. 
   Thumbwheel  450  and, some or all of, the remainder of depth adjustment system  400  may be offset relative to the remainder of tool  10 . For example, thumbwheel  450  may be located laterally relative to a longitudinal axis of handle assembly  300  and/or arms  100  and  200  as depicted in  FIGS. 1 and 4 . Connecting member  420  may also be located at least partially laterally relative to the arms (e.g., first arm  100  and second arm  200 ), and may be separated therefrom by a space along some or all of its length as depicted in  FIGS. 1 ,  4 , and  5 . For example, connecting member  420  may be spaced from first arm  100  and second arm  200 , along a length of connecting member  420  in a direction toward first contacting member  110  and second contacting member  210  from handle assembly  300  until a point of contact of connecting member  420  with one of the contacting members (e.g., second contacting member  210 ). As noted above, depth stopper  410  may be located on underside  215  of second contacting member  210  and located aligned with the longitudinal axis of second contacting member  210 , handle assembly  300  and/or tool  10 . 
   In the example depicted (see e.g.,  FIG. 5 ), connecting member  420  extends (i.e., curves) from a thumbwheel  450  toward arms  100 ,  200  to a lateral position  421  spaced from (and parallel to, along at least a portion of the length of) the arms and to a position  422  further away from the longitudinal axis of tool  10  to connect connecting member  420  to second contacting member  210  at an outer edge of second contacting member  210 . The curves of connecting member  420  toward such longitudinal axis and away therefrom allows connecting member  420  to follow a contour of second arm  200  between thumbwheel  450  and second contacting member  210 . Also, connecting member  420  may include a transverse portion  423  extending transversely relative to a longitudinal axis of tool  10 , first contacting member  110  and second contacting member  210 , first arm  100  and/or second arm  200  as depicted in  FIG. 5 . In an undepicted example, connecting member  420  may be connected to second contacting member  210  at one location instead of the two locations opposite depth stopper  410  depicted in  FIG. 5 . It will be understood by one skilled in the art that connecting member  420  may be formed of any shape such that it connects thumbwheel  450  and depth stopper  410  such that thumbwheel  450  and connecting member  420  are at least partially offset from a longitudinal axis of first arm  100  and/or second arm  200  and such that depth stopper  410  is connected to first contacting member  110  or second contacting member  210  and is located at about a longitudinal axis of tool  10 , arms  100 ,  200 , and/or first member  110  and second member  210 . 
   The offset (e.g., lateral) location of adjustment system  400  relative to the arms and the remainder of tool  10  allows ready access to the user. For example, the location of thumbwheel  450  offset from the longitudinal axis of handle assembly  300  and/or arms  100  and  200  allows the user to easily locate thumbwheel  450  and therefore move depth stopper  410  during use. Also, the location of thumbwheel  450  and the remainder of depth adjustment system  400  at least partially offset from a longitudinal axis of tool  10  and arms  100 ,  200  allow the depth adjustment system  400  to avoid interfering with hinges  302  located at the intersection of the arms and handle assembly  300 . The offset nature of depth adjustment system  300  therefore allows the arms to be readily moved relative to handle assembly  300  at the hinges. 
   A top side  120  of first contacting member  110  and first arm  100  may include a slot  122  configured to receive a keel cutter  500 , as depicted in  FIGS. 1 and 4 . A bottom side  220  of second contacting member  210  and second arm  200  may also include a bottom slot  222  configured (e.g., shaped and dimensioned) to receive keel cutter  500  as depicted in  FIG. 5 . Keel cutter  500  is utilized to cut or form a keel or channel in a top and/or bottom vertebra defining a spinal cavity in which a spinal implant is to be inserted. Also, the slots on arms  100  and  200  (e.g., slot  122  and slot  222 ) guide the cutting of the keel by maintaining the keel aligned with a longitudinal axis of arms  100 ,  200  and first and second contacting members  110 ,  210 . Depth stopper  410  located on bottom side  220  may be a closed loop with the interior of the loop configured to receive keel cutter  500  as depicted in  FIG. 5 . The closed nature of depth stopper  410  inhibits movement of keel cutter  500  out of bottom slot  222  away from bottom side  220 . More specifically, the interior surface of the loop would retain the keel cutter in the interior of the loop if the keel cutter was to be displaced away from slot  22 . Similarly, a keel holder  130  on upper side  120  is a closed loop which inhibits movement of keel cutter  500  away from slot  122  and upper surface  120 . By inhibiting movement of keel cutter  500  away from tool  10 , inadvertent damage to the patient, which could be caused by keel cutter  500  contacting unintended portions of the patient&#39;s anatomy, is minimized. 
   A proximal end  311  of handle assembly  300  includes a receiving flange  310  having a cavity  315  partially defined by a threaded interior radial surface  320  and having an impactable surface  330 , as depicted in  FIGS. 6-7 . Receiving flange  310  is connectable to a suitable handle, such as a T-handle  340 , which may be manipulated (e.g., rotated) by a user when connected to flange  310  to move arms  100  and  200 , along with first and second contacting member  110  and  210 , away from, and toward, one another. More specifically, an outer surface  345  of an end  347  of T-handle  340  may have threads configured to engage threaded interior radial surface  320  of the flange, which may include threads. Also, flange  310  may include a Hudson type connector or any other suitable structure for engagement with the T-handle. 
   For example, flange  310  may include one or more notches  312  at proximal end  311  of flange  310  configured (e.g., shaped and dimensioned) to receive finger tip(s) of the user. The notches allow the user to avoid having his finger(s) caught between proximal end  311  and another portion of T-handle  340  (e.g., a sleeve connecting portion  314 ) when an outer sleeve  313  moves toward flange  310  to attach T-handle  340  to flange  310  in the case of a Hudson type connection for example, as will be understood by those skilled in the art. Sleeve connecting portion  314  may connect outer sleeve  313  of T-handle  340  to an inner shaft (not shown) of T-handle  340 . Outer sleeve  313  may be spring-loaded such that, when previously retracted relative to the shaft, outer sleeve  313  moves toward flange  310  when released by the user. 
   Expansion bar  350  may have threads  305  located at a proximal end thereof opposite front end  20  of tool  10 . Threads  305  may engage with an inner threaded surface (not shown) of flange  310 . Rotation of flange  310  itself or by T-handle  340  thus causes such movement of arms  100  and  200 , along with first and second contacting members  110  and  210  via expansion bar  350 . For example, flange  310  may be connected to an expansion bar  350 , which may be driven forward by rotation of flange  310  by itself or flange  310  and T-handle  340 . The movement of bar  350  forward may cause the arms and members to separate from one another as bar  350  contacts arms  100 ,  200  and/or first and second contacting members  110 ,  210  to distract the upper and lower vertebras to approximate heights or positions as described above. Movement of bar  350  away from front end  20  by flange  310  may cause or allow the arms and members to move from an expanded position to a collapsed position, for example. 
   Also, a distraction indicator is coupled to an actuating member such as expansion bar  350 , which moves longitudinally therewith to provide an indication of the position of expansion bar  350  relative to first and second contacting members  110 ,  210  thereby providing an indication of a distance between the inner surfaces or outer surfaces of the members. For example, a distraction indicator, such as distraction height indicia  433  on expansion bar  350  viewable through a window  435  correspond to the distraction height of first and second contacting members  110  and  210  in the posterior end (i.e., front ends  117  and  217 ) thereof provided by the longitudinal positioning of expansion bar  350  therebetween. The measuring of the distance between the contacting members and thus the vertebra allow the user (e.g., the surgeon) to determine whether the space defined by the vertebra is of an appropriate size to begin the procedure for implanting a prosthetic in the spinal cavity. For example, if a measurement is taken revealing that the spinal cavity is not large enough, the contacting members may be further distracted via the T-handle and expansion bar until an appropriate space between the vertebra is created. 
   Further, when the T-handle is not attached to the flange, impactable surface  330  (e.g., a rigid head) may be accessed such that the user may impact the impactable surface  330  (e.g., with a hammer) to cause movement of tool  10  into the spinal cavity. More specifically, impactable surface  330  is coupled to first contacting member  110  and second contacting member  210 . For example, impactable surface  330  may be connected to expansion bar  350  thereby connecting impactable surface  330 , handle assembly,  300 , arms  100  and  200 , and first and second contacting members  110  and  210 . Also, impactable surface  330  may be located entirely within receiving cavity  315 . Further, impactable surface  330  may be located within a portion of T-handle  340  when T-handle  340  is received in cavity  315  and/or connected to flange  310 . The location of impactable surface  330  within flange  310  allows a user to impact impactable surface  330  itself without the need for a cap to cover flange  310  to avoid damaging the flange. More particularly, instead of placing a cap over flange  310  to drive tool  10  into a spinal cavity, a user may directly impact impactable surface  330  which is located within cavity  315 . The integral nature of impactable surface  330  avoids the necessity for a separate cap to protect flange  310  from damage to its internal threads or other portions thereof which may otherwise occur. Further, such integral nature prevents misplacement or loss of such a protective cap. Moreover, the location of impactable surface  330  within cavity  315  allows any impact to the remainder of flange  310  to be avoided due to its central interior location, i.e., away from other surfaces which could potentially by impacted and damaged. 
   The contacting members (e.g., first contacting member  110  and second contacting member  210 ) have radial interior surfaces (e.g., first radial interior surface  111 ) opposite each other, which may include aligning elements such as guide pins  112  located on such interior surface (e.g., interior surface  111 ) as depicted in  FIGS. 2-3 . Guide pins  112  may be radio opaque and may be aligned such that an imaginary line connecting them is substantially orthogonal to a longitudinal axis of the contacting members, arms (e.g., arms  100 ,  200 ) and/or tool  10 . Also, guide pins  112  may be spaced equidistant from such a longitudinal axis of the arms, members and/or tool  10  as a whole. The guide pins may allow the alignment of tool  10  on a mid-line of a spine. More particularly, the guide pins may be aligned with one another (i.e., one behind the other) when viewed via a lateral x-ray image of the spinal cavity with tool  10  inserted therein. Such alignment may thereby locate a longitudinal axis of tool  10  or portions thereof (e.g., arms  100 ,  200  or first and second contacting members  110 ,  210 ) on a mid-line (not shown) of the spine (not shown). The guide pins may also be utilized to align tool  10  other than on the mid-line. For example, the tool may be aligned based on the position of the pins in a lateral x-ray, or the x-ray itself may be taken from a different direction. 
   Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.