Abstract:
A drill guide apparatus for aligning a cervical drill bit and a target site in a vertebral body prior to drilling a hole in the vertebral body is disclosed. The apparatus includes a handle assembly, an extension member extending from the handle assembly, a mounting plate disposed on the distal end of the extension member, a guide member proximally extending from the mounting plate and a rotation mechanism operably connecting the handle assembly and the extension member. The rotation mechanism is configured to selectively position the handle assembly relative to the mounting plate. The guide member may include a single or double barrel configuration. The guide member is selectively positionable relative to the mounting plate. The mounting plate may include a protrusion for selectively engaging a second plate.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to, and the benefit of, U.S. Provisional patent application Ser. No. 60/847,593, filed on Sep. 26, 2006, the entire contents are hereby incorporated by reference in their entirety. 
     
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to orthopedic spinal surgery, and more particularly, to devices, systems, and methods for guiding a cervical drill, bone screw or other instrument during spinal surgery. 
         [0004]    2. Background of Related Art 
         [0005]    The spinal column is a complex system of bones and connective tissues that provide support for the human body and protection for the spinal cord and nerves. The adult spine is comprised of twenty-four vertebral bodies, which are subdivided into three areas, including seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae. Between each vertebral body is an intervertebral disc that cushions and dampens the various translational and rotational forces exerted upon the spinal column. 
         [0006]    There are various disorders, diseases and types of injury which the spinal column may experience in a lifetime. These problems may include, but are not limited to, scoliosis, kyphosis, excessive lordosis, spondylolisthesis, slipped or ruptured discs, degenerative disc disease, vertebral body fracture, and tumors. Persons suffering from any of the above conditions typically experience extreme or debilitating pain and often times diminished nerve function. 
         [0007]    One of the more common solutions to any of the above mentioned conditions involves a surgical procedure known as a spinal fusion. Spinal fusion involves fusing two or more vertebral bodies together to eliminate motion at the intervertebral disc or joint. To achieve spinal fusion, natural or artificial bone, along with a spacing device, replace part or all of the intervertebral disc to form a rigid column of bone. Mechanical hardware is connected to the adjacent vertebrae to stabilize the spine in that area while the bone grows and the fusion occurs. 
         [0008]    The mechanical hardware used to immobilize the spinal column typically involves a series of bone screws and metal rods or plates. When the spine surgery is performed posteriorly, it is common practice to place pedicle bone screws into the vertebral bodies and then connect a metal rod between the screws, thus creating a rigid structure between adjacent vertebral bodies. When the spinal surgery is performed anteriorly, it is common practice to attach a thin metal plate directly to the vertebral bodies and secure it to each vertebral level using one or more bone screws. For the remainder of this disclosure, references to spinal surgery will be referring to the anteriorly performed surgery in which a metal plate is secured directly to the vertebrae using bone screws. 
         [0009]    Because the spine is routinely subject to mechanical loads which cycle during movement, a primary concern of physicians performing metal plate implantation surgeries, as well as of the patients in whom the implants are placed, is the risk of screw pullout. This is of particular concern in the cervical region because of the critical vessels that abut the anterior surfaces of the cervical spine. Screw pullout occurs when the cylindrical portion of the bone that surrounds the inserted screw fails. A bone screw that is implanted into the vertebrae perpendicular to the plate is particularly weak because the region of the bone that must fail for pullout to occur is only as large as the outer diameter of the screw threads. Screws which are angled inward towards one another, also referred to as “toe-nailed”, or ones which diverge within the bone have been found to greatly reduce the likelihood of screw pull out because the region of bone that must fail is increased as compared to that of screws implanted perpendicular to the plate. 
         [0010]    The metal plates used to connect the vertebrae in spinal surgery are well known in the art. These plates may define any number of openings configured for receiving bone screws. The openings for receiving the screws may include a beveled or angled edge for more securely receiving the angled screws. The metal plates may also include openings or grooves for releasably receiving an elongated handle member for maintaining the metal plate during implantation. Because the metal plates used in spinal fusion are relatively small and awkward to handle, elongated handle members have been developed for releasably engaging the metal plates such that they may be held in position while the bone screws are being applied. The elongated handle members generally include a handle assembly for grasping the handle member and an extension member connected thereto. The distal end of the extension member may include any number of clips, protrusions, tabs or the like for releasably engaging the metal plate. 
         [0011]    As discussed above, positioning of the bone screws used to secure the metal plate to the vertebrae is important to preventing screw pullout, and thus a successful spinal fusion. The elongated handle members may further be configured to include a guide member for guiding the drill, screws or other instrument for assisting a surgeon in positioning the bone screws during implantation of the metal plate. Commonly owned U.S. Pat. No. 7,094,242 to Ralph et al., discloses such a device, and is incorporated herein by reference in its entirety. 
         [0012]    Conventional drill guides generally include a handle assembly fixedly attached to the proximal end of an extension member. The distal end of the extension member generally includes a mounting assembly configured for releasable engagement with a metal plate. The extension member may be configured to include one or more guide members. Alternative drill guides include a guide member that is independently attached to the mounting assembly. During procedures involving surgeons with different preferences, more than one surgeon or the use of multiple instruments within the surgical field, the handle assembly of the drill guide often is oriented in a less than convenient position. Because the handle assembly is fixedly attached to the extension member, the orientation of the handle assembly cannot be adjusted. Furthermore, because the handle is fixedly attached to the extension member it cannot be removed, and thus, cannot be replaced. In the event that the handle assembly becomes worn or damaged, the only option is to replace the entire drill guide. 
         [0013]    Therefore, it would be beneficial to have a drill guide apparatus including a handle assembly that can be selectively positioned about an extension member prior to or during implantation of a metal plate. It would further be beneficial to have a handle assembly that can be removed from the extension member. 
       SUMMARY 
       [0014]    A drill guide apparatus for aligning a cervical drill bit and a target site in a vertebral body prior to drilling a hole in the vertebral body is provided. According to a first embodiment, the apparatus includes a handle assembly, an extension member extending from the handle assembly, a mounting plate disposed on the distal end of the extension member, a guide member extending proximally from the mounting plate and a rotation mechanism operationally connecting the handle assembly and the extension member. 
         [0015]    The rotation mechanism is configured to permit the handle assembly to be selectively positioned relative to the mounting plate. The handle assembly and mounting plate remain generally parallel throughout the positioning of the handle assembly relative to the mounting plate. 
         [0016]    The guide member may be of a single barrel variety, or may instead include a double barrel configuration. The first and/or second barrels define longitudinal bores configured to receive the operational end of an instrument. The first and/or second barrels may be selectively positionable relative to the base and independent of one another. 
         [0017]    The mounting plate may include a protrusion extending distally therefrom. The protrusion may be configured for selective engagement with a second plate. The protrusions may be configured for friction fit with the second plate. 
         [0018]    According to another embodiment of the disclosure, a drill guide apparatus includes a handle assembly, an extension member extending from the handle, a mounting plate disposed on a distal end of the extension member and a guide member extending proximally of the mounting plate. The guide member includes a double barrel configuration. The barrels of the guide member are configured for selective positioning relative to the mounting plate and independent of on another. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Embodiments of the presently disclosed cervical drill guide apparatus are described herein with reference to the accompanying drawings, wherein: 
           [0020]      FIG. 1  is an isometric view of an embodiment of the drill guide apparatus of the present disclosure; 
           [0021]      FIG. 2  is a side view of the drill guide apparatus of  FIG. 1  including a drill bit assembly; 
           [0022]      FIG. 3  is an exploded side view of the drill guide assembly of  FIGS. 1 and 2 ; 
           [0023]      FIG. 4  is an enlarged side view of the guide member of  FIGS. 1 and 2 ; 
           [0024]      FIG. 5A  is a side cross-sectional view of the guide apparatus of  FIG. 1 ; 
           [0025]      FIG. 5B  is an enlarged view of the region of  5 B of  FIG. 5A ; 
           [0026]      FIG. 6A  is a perspective/isometric view of another embodiment of a drill guide according to the present disclosure; 
           [0027]      FIG. 6B  is a top view of the drill guide apparatus of  FIG. 6A ; 
           [0028]      FIG. 6C  is a side view of the drill guide apparatus of  FIG. 6A ; and 
           [0029]      FIG. 6D  is a rear view of the drill guide apparatus of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0030]    While the presently disclosed cervical drill guide apparatus will be described more fully hereinafter with reference to the accompanying drawings, in which particular embodiments are shown, it is to be understood at the outset that persons skilled in the art may modify the apparatus herein described while achieving the functions and results of this apparatus. Accordingly, the descriptions that follow are to be understood as illustrative and exemplary of specific structures, aspects and features within the broad scope of the present disclosure and not as limiting of such broad scope. Like numbers refer to similar features of like elements throughout. 
         [0031]    Referring now to  FIGS. 1-3 , an embodiment of the present disclosure is shown generally as drill guide  100 . Drill guide  100  includes a handle assembly  110 , a rotation mechanism  120 , an extension member  130 , a mounting plate  140  and a guide member  150 . 
         [0032]    Handle assembly  110  includes a handle  112  having a proximal end  112   a  and a distal end  112   b . Distal end  112   b  of handle  112  defines a longitudinal bore  114  therein. Longitudinal bore  114  is configured for operable engagement with rotation mechanism  120 . Distal end  112   b  of handle assembly  112  further includes an opening  114   a  perpendicularly disposed to longitudinal bore  114  for receiving a locking pin  116 . Handle assembly  110  may include any number of configurations to facilitate greater control of drill guide  100  by a surgeon. Handle  112  of handle assembly  110  may include ridges or knurls  118   a  and/or longitudinal grooves  118   b  for facilitating grasping of handle assembly  110 . The length and/or diameter of handle  112  may be modified to accommodate the preferences of the surgeon performing the procedure. Handle  112  may further include finger holes or guards, a slip free coating or the like for improving the user interface with drill guide  100 . 
         [0033]    Referring now to  FIG. 3 , rotation mechanism  120  operably connects handle assembly  110  with extension member  130 . Rotation mechanism  120  includes a connection member  122 , a spring means or spring  125 , a shaft member  126 , proximal and distal end caps  127 ,  128 , respectively, and a screw  121 . Connection member  122  includes a proximal end  122   a  and a distal end  122   b . Proximal end  122   a  of connection member  122  is configured to be received within longitudinal through bore  114  defined by distal end  112   b  of handle  112 . Proximal end  122   a  of connection member  122  defines an opening  123  configured for aligning with opening  114   a  formed in distal end  112   b  of handle  112  when proximal end  122   a  of connection member  122  is completely received within through bore  114  of handle  112 . Opening  123  is sized to receive locking pin  116 . 
         [0034]    When proximal end  122   a  of connection member  122  is received within through bore  114 , opening  114   a  formed in connection member  122  and opening  123  formed in handle  112  may be aligned and locking pin  116  may be received therethrough for securely affixing handle assembly  110  to adjustment mechanism  120 . Removal of locking pin  116  from within openings  114   a  and  123  permits handle assembly  110  to be removed from connection member  122 . In this manner, handle assembly  110  of drill guide  100  may be removed and, if warranted because of failure or user preference, may be replaced. In an alternate embodiment, handle assembly  110  may be frictional received or snap fit about connection member  122 . In yet another embodiment, handle assembly  110  may be rotatably mounted about connection member  122 . 
         [0035]    Distal end  122   b  of connection member  122  defines a through bore  124 . Through bore  124  is perpendicularly aligned with proximal end  122   a  of connection member  122 . Through bore  124  is generally cylindrical and is defined by an open distal end  124   b  and a partially closed proximal end  124   a  having a female hex shaped configuration. Through bore  124  is sized to receive spring  125  positioned about shaft member  126 . Shaft member  126  is a substantial cylindrical elongated member having a proximal end  126   a  and a distal end  126   b . Distal end  126   b  of shaft member  126  is configured to be received within spring  125 , yet is narrow enough to be slidably and rotatably disposed within through bore  124 . Proximal end  126   a  of shaft member  126  includes a collar  127  having a diameter larger than that of distal end  126   b . Collar  127  is of a sufficient size such that it will retain spring  125  about shaft member  126 . Proximal end  126   a  of shaft member  126  further includes geared portion  127   a  extending beyond collar  127 . Geared portion  127   a  may have a cross-section of a number of shapes, including but not limited to, square, diamond, pentagon, hexagon, and multi-pointed star. 
         [0036]    Partially closed proximal end  124   a  is configured for engagingly receiving geared portion  127   a . Partially closed proximal end  124   a  may have a cross-section defining an opening (not shown) of any number of shapes, including but not limited to, square, diamond, pentagon, hexagon, and multi-pointed star. The opening formed in partially closed proximal end  124   a  preferably corresponds in size and configuration with the cross section of geared portion  127  formed on proximal end  126   a  of shaft member  126 . When shaft member  126  is inserted into through bore  124 , geared portion  127   a  is received within partially closed proximal end  124   a . Collar  127  formed on distal end  126   b  retains shaft member  126  within through bore  124  formed in connection member  122 . 
         [0037]    In particular, shaft member  126  is disposed within through bore  124  such that proximal end  127   a  is substantially flush with proximal end  124   a . The male hex head of proximal end  127   a  includes a threaded opening for receiving screw  121 . The male hex head of proximal end  127   a  mates with the female hex opening of  124   a . Screw  121  threadably couples a proximal end cap  129  to shaft member  126 . 
         [0038]    Assembly of rotation mechanism  120  requires insertion of shaft member  126  into through bore  124  such that gear portion  127   a  is received in the opening formed in partially closed proximal end  124   a . Collar  127  abuts partially closed proximal end  124   a  and prevents passage of shaft member  126  therethrough. Spring  125  is disposed about distal end  126   b  of shaft member  126  and is also received within through bore  124 . Spring  125  includes a proximal end  125   a  and a distal end  125   b . Proximal end  125   a  of spring  125  abuts collar  127  of shaft member  126 . Spring  125 , and thus shaft member  126  by virtue of its position in relation to spring  125  is retained within through bore  124  formed in distal end  122   b  of connection member  122  by distal end cap  128 . 
         [0039]    Distal end cap  128  defines an opening  128   a  therethrough sized to permit the passage of distal end  126   b  of shaft member  126  therethrough. Distal end cap  128  is configured to be received about a portion of distal end  126   b  of shaft member  126  that extends beyond open distal end  124   b  of through bore  124 . Distal end cap  128  is frictionally received within open distal end  124   b  of through bore  124 . Distal end cap  128  is further configured to abut distal end  125   b  of spring  125 . Because spring  125  is secured within through bore  124  by collar  127  formed on shaft member  126  and distal end cap  128 , shaft member  126  is thereby springedly retained within through bore  124 . In an alternate embodiment distal end cap  128  may be secured within open distal end  124   b  of through bore  124  using any conventional means, including but not limited to adhesives, welds, crimping, mechanical fasteners and the like. In an alternate embodiment spring means  125  may instead comprise a hydraulic or pneumatic actuator for springedly biasing shaft member  126 . 
         [0040]    Still referring to  FIG. 3 , proximal end cap  129  is positioned adjacent geared portion  127   a  of shaft member  126  while shaft member  126  is retained within through bore  124 . Proximal end cap  129  is secured to shaft member  126  with screw  121 . In an alternate embodiment proximal end cap  129  may be secured to shaft member  126  using adhesive, welds, snap-fit fasteners or the like. Proximal end cap  129  includes a proximal end  129   a  and a distal end  129   b . Distal end  129   b  of proximal end cap  129  forms a button-like assembly that extends distally towards shaft member  126 . The button-like assembly of distal end  129   b  cooperates with shaft member  126  and biases proximal end cap  129  towards partially closed proximal end  124   a  of through bore  124 . Proximal end  129   a  of proximal end cap  129  is configured with a diameter sufficiently small to be rotatably received within partially closed proximal end  124   a  of through bore  124 . 
         [0041]    Proximal end  129   a  of proximal end cap  129  is further configured such that when button-like assembly formed in distal end  129   b  of proximal end cap  129  is depressed, geared portion  127  of shaft member  126  is displaced from within partially open proximal end  124   a  of through bore  124  and shaft member  126  is moved distally such that the male hex head of proximal end  127   a  and the female hex opening  124   a  are disengaged, thereby allowing handle  110  to rotate about a longitudinal axis of shaft member  126 . In this manner handle assembly  110  may be freely rotated about shaft member  126 . Handle assembly  110  and connection mechanism  120  may be configured such that depression of proximal end  129   a  of proximal end cap  129  can be completed with one hand. Depression of proximal end  129   a  of proximal end cap  129  causes the compression of spring  125  within through bore  124 . When the depression force is released, geared portion  127   a  of shaft member  126  is springedly returned to within the opening formed in partially open proximal end  124   a  of through bore  124 . In this manner, shaft member  126  is once again prevented from freely rotating within through bore  124 . The position of handle assembly  110  relative to shaft member  126  is limited by the configuration of geared portion  127   a  and partially closed proximal end  124   a  defining through bore  124 . Distal end  126   b  of shaft member  126  is further configured for secure attachment to extension member  130 . 
         [0042]    Extension member  130  is configured for connecting rotating mechanism  120 , including handle assembly  110 , with mounting plate  140 . Extension member  130  includes a first extension member  132 , a second extension member  134 , and a third extension member  136 . First, second and third extension members  132 ,  134 ,  136  each have a proximal end  132   a ,  134   a ,  136   a  and a distal end  132   b ,  134   b ,  136   b , respectively. Proximal end  132   a  of first extension member  132  is securely connected to distal end  134   b  of second extension member  134  at a first joint  133 . Proximal end  134   a  of second extension member  134  is securely connected to distal end  136   b  of the third extension member  136  at a second joint  135 . First and second joints  133 ,  135  are configured such that when cervical drill guide  100  is assembled first extension member  132  is aligned parallel with shaft member  126 . Fixedly attached to distal end  132   b  of first extension member  132  is mounting plate  140 . 
         [0043]    Mounting plate  140  is a substantially flat member configured to releasably connecting a metal plate (not shown) with drill guide  100 . Mounting plate  140  may be securely affixed to distal end  132   b  of first extension member  132  with any known means, including but not limited to, adhesive, mechanical fasteners, welding, crimping, friction fit or the like. Mounting plate  140  is affixed perpendicular to first extension member  132 . Mounting plate  140  includes one or more protrusions or tabs  144  configured for releasably engaging a metal plate. Protrusions  144  may vary in number, size and location depending on the configuration of the metal plate being implanted. Mounting plate  140  further includes an opening  145  ( FIG. 2 ) configured for receiving guide member  150  ( FIG. 4 ). 
         [0044]    Referring now to  FIG. 4 , guide member  150  includes a tubular member  152  forming a substantially cylindrical member having a proximal end  152   a  and a distal end  152   b . Tubular member  152  includes a longitudinal bore  153  extending therethrough and having a diameter sized to accommodate a drill bit, bone screw or other instrument used during the spinal fusion procedure. Distal end  152   b  of tubular member  152  forms a semi-spherical outer surface portion  154  configured for being rotatably mounted within in socket  145  of mounting plate  140 . In this manner, tubular member  152 , and consequently longitudinal bore  153 , may be positioned at a plurality of angles with respect to mounting plate  140 . 
         [0045]    With reference to  FIG. 2 , mounting plate  140  includes a curvate socket  145  for receiving semi-spherical outer surface portion  154  of distal end  152   b  of tubular member  152  includes. The walls of socket  145  of mounting plate  140  may have a curvature that matches the contour of the semi-spherical outer surface portion  154 . However, it has been contemplated that in other embodiments, walls of another type may be used, such as, for example, walls without a curvature and walls having a different curvature. 
         [0046]    Referring still to  FIGS. 5A and 5B , semi-spherical outer surface portion  154  may be placed into and removed from within socket  145 . Semi-spherical outer surface portion  154  is formed with a notch  155  ( FIG. 4 ) that permits distal end  152   b  to be radially compressed under pressure. This compression causes a reduction in the diameter of distal end  152   b  sufficient to permit semi-spherical outer surface portion  154  to be passed into curvate socket  145 . Once the pressure is released, semi-spherical outer surface portion  154  returns to its resting diameter, and thereby is secured within curvate socket  145 . The configuration of curvate socket  145  and semi-spherical outer surface portion  154  enables guide member  150  to be pivotably and/or rotatably adjusted relative to mounting plate  140 . Semi-spherical outer surface portion  154  of tubular member  152  may be removed from within curvate socket  145  of mounting plate  140  by applying a force to the face of distal end  152   b  of tubular member  152 . The top surface of mounting plate  140  may be cut on a radius or angle such that when tubular member  152  is connected therewith tubular member  152  includes a “stop” feature. End  152   b  defines a transition from cylindrical to spherical. This transition is configured to provide the stop. Modification of the transition may change the amount of angulation tubular member  152  may be permitted to move through. 
         [0047]    Alternately configured guide members may be interchangeably secured within curvate socket  145  depending on the procedure being performed and the instruments needed to complete the procedure. In an alternate embodiment, distal end  152   b  of tubular member  152  does not include notch  155 . In this manner guide member  150  is securely affixed to mounting plate  140  at a predetermined angle and, thus, cannot be adjusted, rotated or removed. 
         [0048]    With reference to  FIGS. 1 and 2 , when assembled connecting member  120  and extension member  130  are configured such that handle assembly  110  extends in a plane parallel to the horizontal plane defined by mounting plate  140 . Handle assembly  110  and connecting member  120  are further configured such that when button-like distal end  129   b  of proximal end cap  129  is depressed handle assembly  110  may be freely rotated about extension member  120  within the same parallel plane. 
         [0049]    Referring now to  FIGS. 6A-6D , an alternate embodiment of the drill guide apparatus of the present disclosure is shown generally as drill guide  200 . Drill guide  200  is substantially similar to above disclosed drill guide  100 . Drill guide  200  includes a handle assembly  210  having a handle  212 , an elongated shaft member  230 , a mounting plate  240  and a double-barrel guide member  250 . Guide member  250  includes a first tubular member  252  and a second tubular member  262 . First and second tubular members  252 ,  262  are substantially similar to tubular member  152  disclosed hereinabove. First and second tubular members  252 ,  262  each have a proximal end  252   a ,  262   a  and distal end  252   b ,  262   b , respectively. Distal ends  252   b ,  262   b  of bases  252 ,  262  are configured for independent attachment to mounting plate  240 . 
         [0050]    Mounting plate  240  defines two openings  245 ,  246  configured for receiving the distal ends  252   b ,  262   b  of tubular members  252 ,  262 . Like tubular member  152  of guide member  150 , tubular members  252 ,  262  may include distal ends  252   b ,  262   b  having semi-spherical outer surfaces, including a notch, for permitting rotation within openings  245 ,  246  formed within mounting plate  240 . In an alternate embodiment distal ends  252   b ,  262   b  of tubular members  252 , 262  do not include a notch and are, therefore securely affixed to mounting plate  240 . In this manner, tubular members  252 ,  262  may be securely affixed to mounting plate  240  at any predetermined angle. Drill guide  200  may further include a connecting member for selectively rotating handle assembly  210  about extension member  230 . 
         [0051]    While there has been described and illustrated specific embodiments of the drill guide apparatus, it will be apparent to those skilled in the art that variations and modifications are possible without deviating from the broad spirit and principle of the present disclosure. Therefore, this disclosure shall not be limited to the specific embodiments discussed herein.