Patent Publication Number: US-2005137606-A1

Title: Quick-release drill guide assembly for bone plate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a continuation of International Application No. PCT/US04/026399, filed Aug. 13, 2004, and is a continuation-in-part of U.S. Non-Provisional Patent Application No. 10/639,515, filed Aug. 13, 2003, the entirety of which applications are expressly incorporated herein by reference thereto. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to a surgical drill-guide assembly that can be releasably attached to a part of a bone-fixation system, for example, a bone plate. The surgical drill-guide assembly of the present invention is used for example, to guide a drill-bit, screw, bone fastener, or other instrument or fastener into bone or other tissue.  
     BACKGROUND OF THE INVENTION  
      The use of surgical fixation plates for a variety of orthopedic applications is widely accepted. The plates are used by surgeons or users to stabilize, mend, or align a patient&#39;s bone as well as alter compression of patient&#39;s bones. Plates are typically fastened to the bones with a plurality of fasteners such as screws that are installed through holes in the plate. Proper orientation and alignment of fasteners and secure surgical fixation of the plates can mitigate some of the potential future complications after implantation.  
      Bone plates used, for example, in spinal applications must be installed with special care, as the plates may be used for long-term, intervertebral fixation, bone-fragment fixation, and/or anterior decompression in the cervical region of the spine. The margin for error in spinal surgery is quite small, particularly because of the sensitivity of the spinal cord and the risk inherent with invasive procedures around the spinal cord. In particular, the dimensions of vertebral bone available for setting fasteners are fairly limiting.  
      Each fixation screw should properly align with its associated plate hole so that each screw is seated correctly with the plate and enters the bone at an appropriate angle. Any misalignment of the screw within the plate hole risks tissue damage and spinal cord injury. In addition, improperly seated screws may result in an unstable or insecure connection of the plate to the bony material, thus potentially defeating the usefulness of the plate. Locking plates, in particular, demand precise fastener alignment.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a drill-guide assembly, which in one embodiment comprises an alignment drill-barrel, a bushing, a dual-arm support, a ratchet-gear mechanism, a handle member, and a release knob.  
      The alignment drill-barrel has a proximal end and a forward-end also called the distal end. The proximal end of the alignment drill-barrel preferably has two ridges, and the distal end is generally tapered. The alignment drill-barrel is configured to receive and guide a drill-bit, bone tap, screw, bone fastener or other instrument into bone or other tissue. The alignment drill-barrel preferably allows for the passage of fixation pins or bone screws, drills, taps, or awls through it in a predetermined trajectory.  
      The bushing preferably has a radially expandable forward-end and a proximal end, wherein the forward-end is configured to engage a fastener hole in a bone-plate. The radially expandable forward end of the bushing preferably has a plurality of finger portions. The radially expandable forward end also preferably has a shoulder, neck, and an outwardly projecting rim disposed forward of the neck. The bushing is configured to slidably receive the alignment drill-barrel. Sliding the alignment drill-barrel toward the forward end of the bushing preferably expands the forward end of the bushing to secure the drill-guide assembly in a bone-plate.  
      The dual-arm support in one embodiment is generally “L-shaped” with the two ends of the “L” forming an obtuse angle. The dual-arm support preferably has a space provided in its center region. In one embodiment, the end portion, which is generally horizontally disposed, comprises a pivot-hole for inserting a pivot screw. At one end, the dual-arm support is immovably or fixedly connected to the proximal end of the bushing, while at its other end, the dual-arm support is immovably connected to the front end of the handle member.  
      The handle member in an exemplary embodiment has a front end and a back end. It is generally oval shaped with broad grooves on top to provide better grip for the surgeon or user using the drill-guide assembly. The handle may be hollow or solid depending upon design choice.  
      The ratchet-gear mechanism in one embodiment is generally “Y-shaped” and is housed within the space of the dual-arm support. At one end, the first leg of the ratchet-gear mechanism is pivotably connected to the dual-arm support at a pivot-point. That end of the first leg further extends beyond the pivot point forming a C-shaped vice-grip. The C-shaped vice-grip attaches to the alignment drill-barrel. The C-shaped vice-grip grasps the alignment drill-barrel in between the two ridges at the proximal end. In a preferred embodiment, the plane of the C-shaped vice-grip is generally perpendicular to the axial direction of the alignment drill-barrel, and the bushing. The second leg of the Y-shaped ratchet-gear mechanism comprises pawls on the outer side which permit incremental swiveling of the ratchet-gear mechanism in a plane perpendicular to the plane of C-shaped vice-grip. The tail-end of the Y-shaped ratchet-gear mechanism acts as a trigger and generally moves in a rotational motion relative to the pivot point in a direction toward or away from the handle member. Movement of the ratchet-gear mechanism, and particularly the C-shaped vice grip, slides the alignment drill-barrel relative to the bushing.  
      The release knob in an exemplary embodiment has a curved longitudinal member with a base. The base has serrations on one side of its circumferential border and a hole on the other side. The release knob is pivoted through the hole in the base about a dowel pin that is attached to the dual-arm support.  
      When the tail of the Y-shaped ratchet-gear mechanism is pressed by a finger of a user in a rotary motion in a direction toward the handle member, the distal end of the alignment drill-barrel is urged into the bushing which in turn, expands the forward-end of the bushing, thus locking the bushing within a hole or recess of the bone-plate. The bushing is configured and dimensioned to expand within a bone-plate hole or recess such that it is releasably locked to the bone-plate.  
      When the Y-shaped ratchet-gear mechanism engages the release knob, the pawls on the outer surface of the second leg of the Y-shaped ratchet-gear mechanism engage the serrations on the release knob to lock the drill-guide to the bone-plate. The alignment drill-barrel preferably self-aligns with the axis of the fastener hole in the plate.  
      When the release knob is further pressed, the pawls are disengaged from the serrations, and the Y-shaped ratchet-gear mechanism returns to an unactuated position, preferably by action of a biasing member such as a spring. The Y-shaped ratchet-gear mechanism, in turn, through its C-shaped vice-grip moves the alignment drill-barrel in a longitudinal direction along its axis, away from the fingers. As a result, the bushing assumes a retracted position thereby disengaging the hole or recess.  
      Another embodiment of a drill-guide assembly is described, comprising an alignment barrel having a proximal end and a distal end; a bushing configured to slidably receive the alignment barrel, the bushing having a radially expandable forward-end and a proximal end, the forward-end configured to be insertable within a hole or recess in a bone plate; a release knob having serrations; and a movable ratchet gear mechanism having a first leg, a second leg and a tail, the first leg of the ratchet-gear mechanism connected to the alignment barrel, the second leg of the ratchet-gear mechanism having pawls configured and adapted to engage the serrations to hold the alignment barrel in position, the tail of the ratchet gear mechanism operable by a user to selectively move the ratchet-gear mechanism, wherein, movement of the ratchet-gear mechanism slides the alignment barrel relative to the bushing to radially expand the forward end to releasably lock the bushing to the plate, and a first drill guide coupled to the bushing, wherein the first drill guide is configured to receive and guide a drill-bit.  
      The first drill guide may be coupled to the bushing by a first connecting element. The first connecting element may have at least two bores for respectively receiving at least a portion a bushing therethrough and at least a portion of a drill guide therethrough. The first drill guide may also be further coupled to the bushing by a second connecting element, and the second connecting element may have at least two bores for respectively receiving at least a portion of a bushing therethrough and at least a portion of a drill guide therethrough.  
      At least two bores of the first connecting element may be separated by a first distance, and the at least two bores of the second connecting element may be separated by a second distance, wherein the first distance may be greater than the second distance, and wherein the second connecting element may be closer to the distal end of the forward end of the bushing than the first connecting element. Alternatively, the first connecting element may be closer to the distal end of the forward end of the bushing than the second connecting element.  
      The first connecting element may further comprise a fin bore configured to receive at least a portion of fin therethrough, wherein at least a portion of the fin in configured to engage at least a portion of a hole or recess when the bushing engages a bone-plate.  
      The drill-guide assembly may further comprise a second guide coupled to the bushing, wherein the second drill guide is configured to receive and guide a drill-bit. The second drill guide may be coupled to the first drill guide. The first and second drill guide may be coupled to the bushing by a first connecting element. The first connecting element may have at least three bores for respectively receiving at least a portion of the first drill guide therethrough, at least a portion of the second drill guide therethrough, and a least a portion of the bushing therethrough.  
      The first connecting element may further include a fin bore configured to receive at least a portion of fin therethrough, wherein at least a portion of the fin in configured to engage at least a portion of a hole or recess when the bushing engages a bone-plate.  
      The first drill guide and second drill guide may further be coupled to the bushing by a second connecting element.  
      The second connecting element may also have at least three bores for respectively receiving at least a portion of the first drill guide therethrough, at least a portion of the second drill guide therethrough, and a least a portion of the bushing therethrough.  
      The bores of the first connecting element receiving first and second drill guides are separated by a first distance, and the bores of the second connecting element receiving first and second drill guides are separated by a second distance, wherein the first distance is greater than the second distance, and wherein the second connecting element may be closer to the distal end of the forward end of the bushing than the first connecting element. Alternatively, the first connecting element may be closer to the distal end of the forward end of the bushing than the second connecting element.  
      The first drill guide may have a longitudinal axis, and when the bushing is locked to a bone-plate, the longitudinal axis of the first drill guide may generally be aligned with a first bone-fastener hole of the bone-plate. The drill-guide assembly may further comprise a second drill guide configured to receive and guide a drill-bit and coupled to the bushing, the second drill guide having a longitudinal axis, and when the bushing is locked to a bone-plate, the longitudinal axis of the second drill guide may be generally aligned with a second bone-fastener hole of the bone-plate. The recess of the bone-plate includes at least one shaped area and a slot.  
      An alternative method for drilling holes in bone is also described, comprising the steps of: (a) providing a drill-guide assembly, comprising an alignment barrel having a proximal end and a distal end; a bushing configured to slidably receive the alignment barrel, the bushing having a radially expandable forward-end and a proximal end, the forward-end configured to be insertable within a hole or recess in a bone plate; a release knob having serrations; and a movable ratchet gear mechanism having a first leg, a second leg and a tail, the first leg of the ratchet-gear mechanism connected to the alignment barrel, the second leg of the ratchet-gear mechanism having pawls configured and adapted to engage the serrations to hold the alignment barrel in position, the tail of the ratchet gear mechanism operable by a user to selectively move the ratchet-gear mechanism, wherein, movement of the ratchet-gear mechanism slides the alignment barrel relative to the bushing to radially expand the forward end to releasably lock the bushing to the plate, and at least a first guide coupled to the bushing, wherein the first drill guide is configured to receive and guide a drill-bit; (b) inserting the bushing into a recess of a bone plate; (c) aligning at least the first drill guide with a first bone fastener hole in the bone-plate; (d) expanding the bushing in the recess; (e) locking the bushing to the plate; (f) inserting a drill-bit into the first drill guide; and (g) drilling a first hole.  
      At least a portion of the forward end of the bushing may be configured to fit in at least a portion of the recess. The bushing may be locked to the plate by locking the alignment barrel and bushing in fixed relation to each other. The drill guide assembly may further comprise a second drill guide coupled to the bushing, wherein the second drill guide is configured to receive and guide a drill-bit.  
      The method may further comprise the steps of inserting a drill-bit guide into the second drill guide, and drilling a second hole.  
      A kit for use with drilling bones is also described, comprising: (a) a drill-guide assembly, comprising an alignment barrel having a proximal end and a distal end; a bushing configured to slidably receive the alignment barrel, the bushing having a radially expandable forward-end and a proximal end, the forward-end configured to be insertable within a hole or recess in a bone plate; a release knob having serrations; and a movable ratchet gear mechanism having a first leg, a second leg and a tail, the first leg of the ratchet-gear mechanism connected to the alignment barrel, the second leg of the ratchet-gear mechanism having pawls configured and adapted to engage the serrations to hold the alignment barrel in position, the tail of the ratchet gear mechanism operable by a user to selectively move the ratchet-gear mechanism, wherein, movement of the ratchet-gear mechanism slides the alignment barrel relative to the bushing to radially expand the forward end to releasably lock the bushing to the plate; (b) at least first and second drill guides able to be coupled to the bushing; and (c) at least first and second connecting elements for coupling at least one drill guide to the bushing.  
      At least the first and second drill guides may have different lengths, and at least the first and second drill guides may have different diameters. At least the first and second connecting elements may each have a bore for receiving at least one drill guide therethrough and a bore for receiving a bushing therethrough, wherein the bores of the first connecting element have a first arrangement, and the bores of the second connecting element have a second arrangement, and wherein the first arrangement may be substantially different than the second arrangement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred features of the present invention are disclosed in the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views. While the presentation is desired and its features presented according to certain illustrated embodiments it is to be understood that the invention is not so limited to the particular embodiments shown and described, wherein:  
       FIG. 1  is a perspective view of a first embodiment of a drill-guide assembly;  
       FIG. 2  is a cross-sectional view of an embodiment of an alignment drill-barrel that may be used with the assembly of  FIG. 1 ;  
       FIG. 3  is a partial cross-sectional view of another embodiment of an alignment drill-barrel that may be used with the assembly of  FIG. 1 ;  
       FIG. 4  is a cross-sectional view of an embodiment of the bushing;  
       FIG. 5  is a side view of the dual-arm support attached to the bushing and handle member;  
       FIG. 6  is a perspective view of the Y-shaped ratchet-gear mechanism;  
       FIG. 6A  is a side view of the Y-shaped ratchet-gear mechanism;  
       FIG. 6B  is a perspective view of the drill-guide assembly showing the ratchet-gear mechanism connected to the dual-arm support;  
       FIG. 7  is a side view of the release knob;  
       FIG. 7A  is a perspective view of the ratchet-gear mechanism engaging the release knob;  
       FIG. 8  is a side view of the handle member of the drill-guide assembly;  
       FIG. 9  is a side view of the bushing with fingers in retracted position;  
       FIG. 10  is a side view of the bushing with fingers in expanded position; and  
       FIG. 11  is a perspective view of the drill-guide assembly of  FIG. 1  engaged to a bone-plate.  
       FIG. 12A  is a perspective view of another embodiment of a drill-guide assembly with drill guides;  
       FIG. 12B  is another perspective view of the assembly of  FIG. 12A ;  
       FIG. 12C  is a partial top view of an exemplary bone plate that can be used with the assemblies of  FIGS. 1 and 12 A;  
       FIG. 13A  is a top view of a proximal connecting element for use with the assembly of  FIG. 12A ; and  
       FIG. 13B  is a top view of a distal connecting element for use with the assembly of  FIG. 12A . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIG. 1 , there is shown an exemplary surgical drill-guide assembly  5 , which is adapted for use with a cervical spine-locking bone plate having a plurality of fastener holes. While the surgical drill-guide assembly is described in conjunction with a cervical locking plate it will be appreciated that the reference to a cervical locking plate is only exemplary, and that the surgical drill-guide assembly can be used with a variety of bone plates, including a locking and a nonlocking bone-plate as well as for example, bone plates for long bones, maxillofacial applications, etc.  
      This embodiment of a drill-guide assembly  5  can be secured or locked into a fastener hole in a bone plate. A related embodiment of a drill-guide assembly  500  that can be secured or locked into a drill recess  354  is shown infra in  FIGS. 12A-13B . Locking or securing may facilitate precision in the surgical procedure, for example, drilling or fastening screws or other similar fasteners. Moreover, the drill-guide can be quickly detached and released from the bone-plate improving the speed of surgical procedures involving drilling or similar procedures.  
      Drill-guide assembly  5  may include an alignment assembly  15 , a release knob  100 , a handle member  250 , a ratchet-gear mechanism  50 , and a dual-arm support  10 .  
      The alignment assembly  15  may comprise an alignment drill-barrel  150  and a bushing  200 . A surgeon or a user can releasably attach the alignment assembly  15  in the fastener hole  352  of a bone-plate  350 . Other attachment options are discussed infra, particularly in relation to  FIGS. 12A-13B . A drill-bit or other such instrument can be inserted into and through the alignment assembly  15 .  
      Referring to  FIG. 2 , an embodiment of the alignment drill-barrel  150  is shown. The alignment drill-barrel  150  may have a through bore  185  from its proximal end  174  to its distal end  172 . A drill-bit or other instrument may be inserted through the bore  185 . In the embodiment of  FIG. 2 , the drill-barrel comprises a first hollow cylindrical section  156  with an annular diameter of x 12 , a second hollow cylindrical section  158  with an inside annular diameter of x 18 , and a third hollow cylindrical section  160  with an inside annular diameter of x 24 , wherein x 24  is smaller than x 18 , and x 18  is smaller than x 2 . The outside surface of the alignment drill-barrel  150  comprises a shoulder  162  and a shoulder  164  wherein the outside diameter of the first section  166  is x 14  which is greater than the outside diameter x 20  of the second section  168 . x 14 has an exemplary diameter of 3 mm to 10 mm, preferably about 8 mm. The third section  170  is a conical section that tapers from an outside diameter x 22  at shoulder  164  to a diameter x 26  at the distal end  172 . The proximal end  174  of the alignment drill-barrel  150  preferably has first circular ridge  152  and second circular ridge  154 . The first and the second circular ridges  152  and  154  respectively, have an outside diameter x 16 .  
      In this embodiment, the first circular ridge  152  is flush with the proximal end  174  of the alignment drill-barrel  150 . The conical section  170  tapers from an outside diameter x 22  at the transition  164  to an outside diameter x 26  at end  172 . Preferably, inner diameter x 24  is constant along the length of conical section  170  of alignment drill-barrel  150  as defined along center line  180 .  
      Referring to  FIG. 3 , an alignment drill-barrel  150  according to another embodiment is shown. In  FIG. 3 , alignment drill-barrel  150  is hollow with a cylindrical section  182  and a tapered, conical section  184  to facilitate movement of alignment drill-barrel  150  within bushing  200 . Cylindrical section  182  has outside diameter x 5 , while conical section  184  tapers from an outside diameter x 5  at the transition  186  to an outside diameter x 6  at the distal end  188 . Preferably, inner diameter x 7  may be constant along the length of alignment drill-barrel  150  as defined along center line  190 .  
      Referring to  FIG. 4 , a bushing is shown. Bushing  200  may coaxially receive alignment drill-barrel  150  about a central line  240 . Bushing  200  may be substantially symmetrical about line  240 . The forward end  222  of bushing  200  may preferably be comprised of longitudinally extending fingers  210 . Individual fingers  210  may be separated by slits  204  extending longitudinally between adjacent fingers  210 . Slits  204  as shown, for example, in  FIG. 4 , may include a circular portion  206  that serves to minimize stress concentration when fingers  210  are flexed. Fingers  210  may be resiliently biased inwardly and naturally assume an inward disposition when in a relaxed state. At a front portion of the expandable forward end  202  of bushing  200 , the fingers  210  may form a radially expandable circumferential neck  208 . At the back end of and adjacent to neck  208  may preferably be a shoulder  212 .  
      Neck  208  may span a length that is slightly longer than the thickness of the fastener hole wall from the bone-side surface to the top surface of a bone-plate. Thus, neck  208  can be inserted into the bone-plate fastener hole  352  and the fingers  210  expanded to secure the bushing  200  to the plate. More particularly, movement of alignment drill-barrel  150  within bushing  200  may expand fingers  210  to secure the bushing  200  to the bone plate. In this manner, the drill-guide assembly can be secured to the plate, restricting relative movement. In a preferred embodiment, fingers  210  forming a radially expandable rim  214  may be provided at the front end of and adjacent to neck  208 .  
      In another embodiment, the distal end  222  of the bushing  200  may not contain the rim  214 , the neck  208  or the shoulder  212 , but instead has a tapered end with the inner and the outer diameter of the tapered end decreasing from point  220  shown in  FIG. 4 . In such an embodiment, the taper is such that it may fit freely through a fastener hole in a bone plate.  
      In alternate embodiments, no rim may be used. The several portions of bushing  200 , i.e., the neck  208 , the shoulder  212 , and the rim  214 , may preferably be a single piece of material of unitary construction.  
      In other alternate embodiments, fingers  210  need not include a shoulder, neck, and/or a rim. Instead, for example, a small pin may be used to secure the bushing to the plate. In an alternatively preferred embodiment, the inward bias of fingers  210  is selected to produce the desired friction with the bone-plate  350  so that the fingers  210  fit snugly within the bone-plate fastener hole  352  (or drill recess  354 , as discussed infra in relation to  FIGS. 12A-13B ), preferably allowing operation of handle member  250  with only one hand. Alternative resiliency for fingers  210  may be varied to suit the purpose of the design.  
      In a preferred embodiment bushing  200  has one or more longitudinal slots on its side  224  in axial direction  240  just above the circular portion  206 . These slots provide better cleaning during autoclave or other disinfection and/or cleaning procedures.  
      Referring to  FIG. 4 , bushing  200  has a circumferential ridge  218  with an outer diameter x 3 , and a region  216  has an outer diameter x 4 . x 4  has an exemplary dimension of 4 mm to 20 mm, preferably about 8 mm.  
      As shown in  FIG. 5 , in one embodiment, dual-arm support  10  connects the handle member  250  to the alignment assembly  15 . More specifically, in the exemplary embodiments of  FIGS. 1 and 2 , the dual-arm support  10  is fixedly connected at its end to the proximal end  174  of the alignment assembly  15 . Dual-arm support  10  preferably is generally “L-shaped” with first part  14  connected to bushing  200 . More specifically, end  12  of dual-arm support  10  is attached to ridge  218  at the proximal end  242  of the bushing  200 .  
      The dual-arm support  10  is preferably fixed with the bushing  200  by welding. In an alternative embodiment, friction fitting, press fitting, and such can be used. Outer diameter x 3  of ridge  218  is about the same size as inner diameter x 1  of the clamp  12  of the dual-arm support  10 . Bushing  200  may also be fixed to dual-arm support  10  by releasable fastener means. First part  14  is generally perpendicular to the axial direction of the alignment assembly  15  or the bushing  200 . The second part  16  of the dual-arm support  10  preferably forms an obtuse angle θ d1  with the first part  14  of the dual-arm support  10 . θ d1  may range from about 90  to about 180 , and more preferably from about 105  to about 135 . Dual-arm support  10  and handle member  250  are fixedly connected by a dowel pin  20  at the front end of the handle member  250 , so that they are immovable with respect to each other. In the preferred embodiment, handle member  250  is located remotely from the drilling site, thereby increasing visibility near the locking bone plate  350 .  
      As shown in  FIG. 5 , the second part  16  of the dual-arm support  10  may be attached to the first part  14  by a dowel pin  18 , or the dual-arm support  10  may be an integral, monolithic construction. The second part  16  of the dual-arm support  10  also forms an obtuse angle θ d2  with the handle member  250 . θ d2  may range from about 90  to about 180 , and more preferably from about 105  to about 135 . The handle member  250  and the dual-arm support  10  generally form an “S” shape or a zigzag shape, and in a preferred embodiment, the longitudinal axis  24  of the first part  14  and the longitudinal axis  26  of the second part  16  lie in the same plane. The longitudinal axis  280  of the handle member  250  also preferably lies in the same plane as the longitudinal axis  24  of the first part  14  and the longitudinal axis  26  of the second part  16  of the dual-arm support  10 . Preferably the longitudinal axis  24  of the first-part  14  of the dual-arm support  10  is generally parallel with the longitudinal axis  280  of the handle member  250 .  
      Referring to  FIG. 6 , there is shown an exemplary embodiment of the ratchet-gear mechanism  50 . The ratchet-gear mechanism  50  allows the user to manipulate the locking and release of the drill-guide assembly  5  with the bone-plate  350  by engagement and disengagement, respectively, of the pawls  58  with the serrations  102 . The ratchet-gear mechanism  50 , in a preferred embodiment is generally “Y-shaped” with a first leg  52 , a second leg  54 , and a tail  56 .  
      The first leg  52  of the ratchet-gear mechanism comprises a generally C-shaped vice-grip  60  at its end, and a pivot hole  62  for insertion of a pivot screw  64 . The C-shaped vice-grip  60  grips the alignment drill-barrel  150  in between the first ridge  152  and second ridge  154  (see also  FIG. 2 ) located at the end  174  of the drill-barrel  150 . As shown in  FIG. 6A , in a preferred embodiment, the plane of the C-shaped vice-grip  60  that forms an anterior portion of the first leg  52  of the Y-shaped ratchet-gear mechanism  50  makes an acute angle θ d  with the longitudinal axis  64  of the first leg  52  of the Y-shaped ratchet-gear mechanism  50 . At the point of inflexion between the longitudinal first leg  52  and the C-shaped vice grip  60 , pivot screw  64  and hole  62  are located. This pivot mechanism  62  helps the movement of the alignment drill-barrel  150 . In a preferred embodiment, the acute angle is from about 25  to about 45 . In a further preferred embodiment the acute angle θ d  is such that when the ratchet-gear mechanism  50  is completely disengaged from the serrations  102  of the release knob  100 , the alignment drill-barrel  150  can be removed from the bushing  200  in a longitudinal direction away from the fingers  210  by moving the ratchet-gear mechanism  50  in a direction away from the handle member  250 , about the pivot screw  64 . θ d  may be 0  to 90 , with an exemplary dimension of 60 .  
      The second leg  54  of the Y-shaped ratchet-gear mechanism  50  comprises horizontal pawls  58  which engage serrations  102  at the end of the release knob  100 . The tail  56  of the Y-shaped ratchet-gear mechanism  50  acts as a trigger for a user to apply a force to actuate movement of the alignment drill-barrel  150 .  
      Referring to  FIG. 7 , the release knob  100  is pivoted about a dowel pin  106  which is inserted through the dowel pin hole  104  in the release knob  100 , and the release knob hole  142  in the second part  16  of the dual-arm support  10 . With pivotal support from the dowel pin  106 , the serrations  102  on the surface of the release knob  100  can engage with the pawls  58  on the second leg  54  of the Y-shaped ratchet-gear mechanism, when the tail  56  (trigger) of the Y-shaped ratchet-mechanism is pressed or moved in a direction toward the handle member  250 . In a preferred embodiment, the release knob  100  has a rubber sleeve  106  or a sleeve made from a material which provides a firm traction when the surgeon or the user presses the release knob  100 . Alternatively, or additionally the surface of the release knob may have surface texturing to increase the traction when a surgeon or a user manipulates the release knob  100 .  
      Referring to  FIG. 8 , handle member  250  is shown. Handle member  250  is generally oval shaped with broad grooves  252  on top to provide better grip to the surgeon or user when using the drill-guide assembly  5 . At the front end  254  of the handle member  250 , there are two cavities, the first cavity  256  and the second cavity  258 . The first cavity  256  has an axis along line  260  and the second cavity  258  has an axis along line  270 . The first cavity  256  houses compression spring  272  and the second cavity  258  houses the dual-arm support  10 , or more specifically the second part  16  of the dual-arm support  10 . The second part  16  of the dual-arm support  10  is fixed to the handle member  250  by a dowel pin  20 . The dowel pin  20 , in a preferred embodiment, is generally perpendicular to the axis  280  of the handle member  250 . Exemplary dimensions of the handle are 100 to 150 mm long with a width at the widest point of 15 mm to 40 mm.  
      When a surgeon or a user presses the trigger  56 , toward handle member  250 , the ratchet-gear mechanism  50  swivels. Due to the movement of the Y-shaped ratchet-gear mechanism  50  in the direction of the handle member  250 , the alignment drill-barrel  150  moves the bushing  200  in the downward direction toward the bone-plate  350 . Due to the conical shape  170  of the alignment drill-barrel  150  ( FIG. 2 ), the fingers  210  on the bushing  200  expand in an outward direction as the front end  172  of alignment drill-barrel  150  approaches the front edge  214  of bushing  200 . When the outward diameter of the fingers  210  matches that of the fastener hole  352 , the drill-guide assembly  5  locks to the bone-plate  350 . A surgical drill-bit  400  or any other appropriate bit, screw, tap, awl, or such device, can be inserted through the alignment drill-barrel  150 .  
      Alignment drill-barrel  150  may be configured and dimensioned to be slidably received within bushing  200 . The alignment drill-barrel  150  and bushing  200  may cooperate to permit drill-guide assembly  5  to lock to a bone plate  350 . The conical section  184  of the alignment drill-barrel  150  may cooperate with fingers  210  of bushing  200  to expand fingers  210  when the alignment drill-barrel  150  is moved into a locked position. The conical section  184  of alignment drill-barrel  150  may push outwardly against the inner surface of the bushing  200  as alignment drill-barrel  150  is moved forward to expand the forward end  214  of the bushing  200 . In this embodiment, the conical section mates with and pushes against the inner surface of the bushing  200  forward of circular portion  206  of slits  204  in fingers  210 , to push the fingers  210  radially outward (see  FIG. 4 ).  
      Alignment drill-barrel  150  may be aligned within bushing  200 , such that center line  240  or  190  may be collinear with line  180 . When bushing  200  is placed in a fastener hole of a bone plate, and ratchet-gear mechanism  50  is actuated such that the almost fully actuated position is reached (i.e. when trigger  56  is substantially parallel to handle member  250 ), end  172  of alignment drill-barrel  150  may be substantially coplanar with rim  214  of bushing  200 . It should be noted that alignment drill-barrel  150  may be coaxially received in bushing  200  which may also be the path of surgical drill-bit  400  inserted in cannula  182  of the alignment drill-barrel  150 .  
      Generally, a surgeon or user should continue to depress the trigger  56  and handle member  250  toward each other to maintain an actuated position of Y-shaped ratchet-gear mechanism. Depending on the size of the fastener hole  352  (or drill recess  354 , see  FIGS. 12A-13B ) and the firmness of the locking desired, the pawls  58  located on the second leg  54  of the Y-shaped ratchet-gear mechanism  50  may engage with the serrations  102  on the release knob  100  holding the ratchet-gear mechanism  50  in place. The release knob  100  preferably may be held firm in its position by the compression force of the spring mechanism  272 , which may be located at the front end  254  inside the cavity  256  of the handle member  250 . With the ratchet-gear mechanism  50  provided in this drill-guide assembly  5 , the serrations  102  on the release knob  100  can be used to releasably lock Y-shaped ratchet-gear mechanism  50  at the desired level of actuation. This may obviate the need for a surgeon or user to continue to depress the trigger  56  relative to handle member  250  after desired actuation has occurred. The pawls  58  on the second leg  54  of the Y-shaped ratchet-gear mechanism  50  may engage the serrations  102  on the release knob  100  when the trigger  56  is pressed sufficiently. The release knob  100  may be held in a fixed position as a result of the compression force exerted by the compressed spring  272 .  
      When the release knob  100  is pressed in the direction of the front end  254  of the handle member  250 , the spring member  272  may be compressed, the pawls  58  may be disengaged from the serrations  102 , and the Y-shaped ratchet-gear mechanism  50  may become unactuated. When the Y-shaped ratchet-gear mechanism  50  is unactuated, the force that is keeping the alignment drill-barrel  150  in a position toward fingers  210  may be released. As a result, the alignment drill-barrel  100  may no longer be pushing the fingers  210  on the bushing  200  in an outward direction toward the bone-plate  350 . The alignment drill-barrel  150  can be then moved in a longitudinal direction away from the fingers  210  on the bushing  200 . As a result, the bushing  200  may assume a retracted position as demonstrated in  FIG. 9 . Once the fingers  210  retract, the drill-assembly  5  may unlock from the fastener hole  352  or drill recess  354  of the bone-plate  350  and the user or surgeon can withdraw it.  
      When the release knob  100  is pressed to further compress the spring, the pawls  58  may disengage from serrations  102 , thereby de-actuating the Y-shaped ratchet-gear mechanism  50 , which in turn, through the pivot action at the pivot screw  64  may result in the movement of the alignment drill-barrel  150  in a direction away from the bone-plate  350 .  
      Advantageously, a surgeon or user can operate drill-guide  5  with only one hand, due to the ergonomic positioning of trigger  56  and handle member  250 . With the embodiment illustrated in  FIG. 1 , a user can attach the drill-guide by using a finger, such as an index finger, to engage and manipulate the tail  56  of the ratchet-gear mechanism  50 , and while a second different finger, such as a thumb, to engage and manipulate the release knob  100 .  
      When the alignment drill-barrel  150  is in the unlocked position as shown in  FIG. 9 , the conical section  184  allows fingers  210  to return to a relaxed, contracted position. This allows bushing  200  to be inserted and retracted from plate fastener hole. The inner surface of the bushing  200  forward of steps  220  in bushing  200  is preferably tapered at an angle θ B  to line  240  that is about 1 degree more than taper angle θ T  of conical sections  184 , and preferably angle θ B  is about 4 degrees. A desirable amount of movement of alignment drill-barrel  150  within bushing  200  is thus provided to bias fingers  210  of bushing  200  from a contracted position to an expanded position. Alternative taper angles of conical section  184  and inner surface of bushing  200  may be chosen according to varying design criteria. In addition, a preferred, short movement of trigger  56  (ratchet-gear mechanism  50 ) is required to expand and contract fingers  210  of bushing  200 .  
      Before and during bone plate implantation, the surgeon or user may insert the expandable distal end  222  of bushing  200  in particular neck  208  and rim  214 , into fastener hole  352  or drill recess  354  in a bone plate  350 . By pressing trigger  56  of the Y-shaped ratchet-gear mechanism  50  relative to the handle member  250 , the surgeon or user may grasp and manipulate the plate  350  without an additional plate holder if so desired. Friction between the forward conical section  184  of the alignment drill-barrel  150  and the inner surface of fingers  210  especially at neck  208  and rim  214  may retain the expandable distal end  222  of bushing  200  in an expanded, locked position. Thus, when bushing  200  is in the expanded, locked position in a fastener hole of a plate placed in position for implantation, movement of the plate during the drilling operation can be minimized.  
      Drill-barrel  150  may preferably be sized so that once the bone plate  350  is properly positioned over the implantation site and bushing  206  is locked to the plate, the insertion point of a surgical drill-bit  400  at the proximal end of drill-barrel  150 , is located at a distance beyond the patient&#39;s body such that a spinning surgical drill-bit  400  will not laterally reach or harm surrounding tissues that the surgeon or user does not intend to drill.  
      Preferably, the surgical drill-bits used with surgical drill-guide assembly  5  are configured and dimensioned to drill holes of about 12, 14, or 16 mm in depth. Suitable drill-bits typically have integral stops so that when the drill-bits are used with alignment drill-barrel of an established length, the holes produced by the drill-bit will not be deeper than the intended depth using a given bit. The stops may be positioned to abut the upper surfaces at the proximal end of drill-barrel  150 , when a drill-bit has been inserted in the barrel to a particular depth.  
      Another embodiment of a drill-guide assembly  500  is shown in  FIGS. 12A-13B . As with drill-guide assembly  5  (see  FIG. 1 , supra), assembly  500  may include an alignment assembly  515 , release knob  600 , handle member  650 , ratchet-gear mechanism  550 , bushing  450  with fingers  570  and slits  572 , and a dual-arm support  610 , the components of which may exhibit some or all of the characteristics of the corresponding components described above in relation to assembly  5 .  
      Drill-guide assembly  500  may also include first and second drill guides  502 ,  504  for use with surgical drill (e.g.,  400 ). Drill guides  502 ,  504  may be connected to bushing  450  by proximal and distal connecting elements  510 ,  512 , which are discussed in more detail below in relation to  FIGS. 13A-13B . Drill guides  502 ,  504  may also have proximal ends  506 ,  508  and distal ends  516 ,  518 , with a bores  507 ,  509  extending therebetween. The bores  507 ,  509  should be sized to receive at least a portion of a surgical drill, and should preferably align with a bone fastener hole  352  during use. Drill guides  502 ,  504  may have a length L 1 , L 2  (see  FIGS. 12A-12B ) from about 150 mm to about 350 mm, and more preferably, a length of about 260 mm. Generally, drill guides  502 ,  504  have a greater length than bushing  450 . Drill guide lengths L 1 , L 2  may or may not be approximately equal.  
      Bores  507 ,  509  may have a variable diameter B 1 , B 2  along the length L 1 , L 2  of drill guides  502 ,  504 . Bore diameter B 1 , B 2  may have a diameter of about 5 mm to about 15 mm at proximal ends  506 ,  508  and/or distal ends  516 ,  518 .  
      Drill-guide assembly  500  may be used with the plate shown in  FIG. 12C . Plate  350  may have a plurality of fastener holes  352  and at least one drill recess  354  in body  351 . Recess  354  may have shaped areas  356   a,    356   b  with midpoint  358   a,    358   b,  with a distance MPD between midpoints. Recess  354  may also have a slot area  360  extending between shaped areas  356   a,    356   b.    
      Alternatively, recess  354  may at least partially comprise a polygonal shape, such as a hexagon, rectangle, or square. The recess  354  may also take the shape of a plurality of polygonal shapes, for example, two overlapping hexagons may comprise the shape of the recess  354  to form a combination-polygonal recess. These embodiments may be particularly useful in bone-plates with a reduced area in which to place a recess  354  for purposes of aligning assembly  500 .  
      In use, the fingers  570  of bushing  450  of assembly  500  may be inserted into drill recess  354 , instead of fastener hole  352 . The engagement and/or locking of the bushing  450  within a drill recess  354  may take some or all of the characteristics of the engagement and/or locking of bushing  200  with a fastener hole  352 , as described above. Generally, it may be preferable for the bushing  450  to engage the drill recess  354  at shaped area  356   a,    356   b.  The placement and locking of bushing  450  at shaped area  356   a  may align drill guides  502 ,  504  with fastener holes  352   a,    352   b,  respectively. Similarly, the placement and locking of bushing  450  at shaped area  356   b  may align drill guides  502 ,  504  with fastener holes  352   c,    352   d,  respectively.  
      Assembly  500  may also have a fin  514  to assist the insertion, locking, and/or alignment of the assembly in a drill recess  354 . Fin  514  may generally be an elongated component, with at least a portion of the fin  514  secured in the distal connecting element  512  at fin bore  536  (see  FIG. 13B ). In use, when the bushing engages a shaped area  356   a,    356   b,  the fin concurrently engages slot  360 . The fin  514  may or may not touch the sides of the slot  360  when the bushing  450  is fully inserted into a shaped area  356   a,    356   b.    
       FIG. 13A  is a top view of a proximal connecting element  510 , and  FIG. 13B  is a top view of a distal connecting element  512 . Proximal connecting element  510  may have a bushing bore  530   a,  and first and second drill guide bores  532   a,    534   a.  First and second drill guide bores  532   a,    534   a  may have respective midpoints  537   a,    539   a,  wherein a distance D, extends between midpoints  537   a,    539   a.  Distal connecting element  512  similarly may have a bushing bore  530   b,  and first and second drill guide bores  532   b,    534   b  with respective midpoints  537   b,    539   b.  Midpoints  537   b,    539   b  may have a distance D 2  between them. Distal connecting element  512  may also have a fin bore  536  located near the bushing bore  530   b.  Fin bore  536  may receive at least a portion of a fin  514 , as discussed above.  
      Bushing bores  530   a,    530   b  may receive at least a portion of a bushing  450 . Likewise, first and second drill guide bores  532   a,    534   a,    532   b,    534   b  may receive at least a portion of a first and second drill guide  502 ,  504 , respectively. Generally, the proximal connecting element  510  may be situated near the proximal ends  506 ,  508  of first and second drill guide  502 ,  504 , and the distal connecting element  512  may be situated near the distal ends  516 ,  518  of the first and second drill guides  502 ,  504 . While the embodiment in  FIGS. 12A-12B  show two connecting elements,  502 ,  504 , it contemplated that only one connecting element could be used, or that more than two connecting elements could be utilized with a single assembly  500 .  
      The placement of the bores in the connecting elements  510 ,  512  may determine the angles and arrangements of which the bushing  450  and first and second drill guides  502 ,  504  are situated in relation to one another. For instance, the embodiment shown in  FIGS. 12A-13B  utilizes proximal connecting element  510  with distance D 1  larger than the distance D 2  of the distal connecting element  512 . The result of this arrangement is, as bushing  450  and first and second drill guides  502 ,  504  are generally linear, that the bushing and drill guides are generally convergent from the proximal end of the assembly to the distal end of the assembly  500 . However, it is contemplated that D 1  and D 2  could be substantially equal, thereby creating an arrangement where the bushing and drill guides would be substantially parallel. Moreover, D 2  may be greater than D 1 , thereby creating a divergent relationship between the bushing and/or drill guides from the proximal to the distal end of the assembly  500 . Generally, both D 1  and D 2  may be from about 5 mm to about 35 mm. The sizes of the bores of each connecting element  510 ,  512  may generally fit a desired engagement portion of a bushing and/or drill guide.  
      Those skilled in the art will recognize that bushing  200 ,  450  may be configured and dimensioned to fit bone plate fastener holes and/or drill recesses with shapes other than circular. For example, bushing  200 ,  450  may be adapted to fit elliptical, hexagonal, star-shaped, or square fastener holes and/or drill recesses.  
      Preferably, the components of surgical drill-guide assembly  5 ,  500  are metallic, passivated, and electropolished. Most preferably, the components are formed of stainless steel, except for the springs which are formed of spring steel, although other materials may be used. Preferably, at least the handle member is forged, while the other components may be machined, and the surgical drill-guide assembly preferably has a matte finish so that the surfaces of the components do not reflect operating room light in such a manner as to distract the surgeon or user. Some components may be subjected to heat treatments so that the surfaces are work hardened. The surfaces are preferably burr-free. Preferably, the surface finish allows individual components to move with respect to each other in a smooth and non-binding fashion through each component&#39;s entire range of motion. Additionally, all pins and fasteners are preferably flush with the surfaces into which they are fixed.  
      The present invention also involves several methods of drilling holes. In one embodiment, a surgeon or user may insert the bushing of a surgical drill-guide assembly into a fastener hole of a bone-plate and may depress the ratchet-gear mechanism to slide the alignment drill-barrel forward, expanding the bushing preferably by the conical portions of the alignment drill-barrel radially spreading the fingers in the bushing. The surgeon or user may then lock the bushing to the plate by locking the alignment drill-barrel and the bushing in fixed relation to each other, which thereby may relieve the surgeon or user of the need to squeeze the ratchet-gear mechanism toward the handle (see  FIG. 11 ). The surgeon or user may align the surgical drill-bit along the drilling axis defined through the center of the bore in the alignment drill-barrel and inserts the drill-bit in the barrel. The surgeon or user then may drill a first hole coaxial with the central axis of a first fastener hole in the plate. The drill-bit may be stopped at a predetermined distance to provide a hole of predetermined depth. The drill-bit may be removed from the alignment drill-barrel. The bushing may thereafter be unlocked from the plate by pressing the release knob, which may release the bushing from the fastener hole so that the user can then freely and unfetteredly remove the drill-guide assembly from the plate.  
      In another embodiment of use, a surgeon or user may insert the bushing of a surgical drill-guide assembly into a shaped area drill recess of a bone-plate and may depress the ratchet-gear mechanism to slide the alignment drill-barrel forward, expanding the bushing preferably by the conical portions of the alignment drill-barrel radially spreading the fingers in the bushing. The fin of the assembly may concurrently engage the slot of the recess. The surgeon or user may then lock the bushing to the plate by locking the alignment drill-barrel and the bushing in fixed relation to each other, which thereby may relieve the surgeon or user of the need to squeeze the ratchet-gear mechanism toward the handle (see  FIG. 11 ). The surgeon or user may align the surgical drill-bit along the drilling axis defined through the centers of the bores of the first and/or second drill guides and may insert the drill-bit into the bores as desired.  
      While the invention has been shown and described herein with reference to particular embodiments, it is to be understood that the various additions, substitutions, or modifications of form, structure, arrangement, proportions, materials, and components and otherwise, used in the practice of the invention and which are particularly adapted to specific environments and operative requirements, may be made to the described embodiments without departing from the spirit and scope of the present invention. For example, the surgical drill-guide assembly may have alignment drill-barrel that can be angulated in the cephalad/caudal or sagittal planes, thereby permitting a range of angles to be chosen for the holes to be drilled and further permitting a range of spacings of plate holes to be accommodated. Moreover, alignment drill-barrel that is removeably attachable to the base may be provided so that a surgeon or user may select alignment drill-barrel with holes that precisely accommodate a desired drill-bit size. In addition, the drill-guide assembly handle may include a grip that generally follows the contours of fingers that hold the grip. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.