Abstract:
The present invention is directed to a surgical drill guide. The drill guide may include a first drill guide body having a distal end for placement substantially adjacent a bone, a second drill guide body slidable with respect to the first drill guide body and having a proximal end for contacting a portion of a drill bit, a handle associated with at least one of the first drill guide body and the second drill guide body, and a detent mechanism for releasably retaining the position of the first drill guide body with respect to the second drill guide body in predefined increments. Additionally or alternatively, the drill guide may include a locking member movable between a first position where it substantially prevents sliding of the second drill guide body with respect to the first drill guide body, and a second position where it permits sliding of the second drill guide body with respect to the first drill guide body. The locking member may be resiliently biased to the first position. Other features for improving the drill guide are disclosed and claimed as well.

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to surgical drill guides. More specifically, the present invention relates to surgical drill guides for positioning, orienting and measuring the depth of holes to be drilled in bone tissue.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is well known to drill holes in bones in order to accommodate fastening devices used to anchor implants within a patient&#39;s body. For instance, pedicle screws have been used to anchor instrumentation systems to the spinal column of patients for correcting a variety of spinal disorders. One commonly used technique for inserting a pedicle screw into the bone includes the preparation of a pilot hole through the pedicle before inserting the screw therein. Typically, the selection of the insertion point is made based on the anatomy of the vertebra. Once the insertion point has been selected, a drill guide may be used to guide the drill bit along the proper axis, and/or to set the depth to which the drill bit penetrates the bone. Conventional drill guides generally include a handle having an adjustable length sleeve attached thereto. When used in conjunction with a drill bit having a fixed stop, the length of the sleeve may control the depth to which the drill penetrates the bone (and the depth of the consequent hole). Known drill guides, however, may include one or more drawbacks. For example, it may be necessary to rotate or screw an inner sleeve within an outer sleeve (or other member) to adjust the hole depth. This process can be timely, and may require removing the drill guide from the incision in order to make subsequent adjustments. Known drill guides may also lack any type of incremental adjustment of the hole depth, which may also add to the time required for the adjustment process. In addition, with known drill guides, one or more parts necessary to adjust the hole depth may be located in the patient, thus requiring the drill guide to be removed from the incision in order to adjust the hole depth. Further, known drill guides are often complicated to adjust. Thus, there remains a need in the art for surgical drill guides that provide quick and easy adjustment of the hole depth, allow for such adjustment from outside of the patient, can be left in place during adjustment of the hole depth, and are ergonomic, aesthetically pleasing, and easy to use.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention is directed to a surgical drill guide. The drill guide may include a first drill guide body having a distal end for placement substantially adjacent a bone, a second drill guide body slidable with respect to the first drill guide body and having a proximal end for contacting a portion of a drill bit, a handle associated with at least one of the first drill guide body and the second drill guide body, and a detent mechanism for releasably retaining the position of the first drill guide body with respect to the second drill guide body in predefined increments. The proximal end may be spaced a first distance from the distal end, and the detent mechanism may provide incremental adjustment of the first distance. The first distance may determine the maximum penetration depth of a drill bit inserted through the first drill guide body and the second drill guide body.  
         [0004]     The detent mechanism may comprise a detent body that engages the first drill guide body or the second drill guide body. For example, the detent body may be resiliently biased toward the first drill guide body or the second drill guide body, such as by a spring. The detent body may engage a plurality of detents defined on the second drill guide body. For example, the detent body may include an angular tip that engages the detents. Additionally or alternatively, the detents may be angular indentations defined on the second drill guide body.  
         [0005]     The surgical drill guide may further include a locking member movable between a first position where it substantially prevents adjustment of the second drill guide body with respect to the first drill guide body, and a second position where it permits adjustment of the second drill guide body with respect to the first drill guide body. For example, the locking member may be slidable or pivotable between the first position and the second position. The locking member may be resiliently biased toward the first position. The locking member may engage a portion of the detent mechanism when the locking member is in the first position. Alternatively, the locking member may engage the plurality of detents when in the first position.  
         [0006]     The first drill guide body and the second drill guide may body define a common longitudinal axis. The second drill guide body may be slidable within the first drill guide body, or vice versa. The first drill guide body and/or the second drill guide body may comprise a substantially tubular shaft. The distal end of the first drill guide body may include at least two projections for engaging the bone. The proximal end of the second drill guide body may in operation engage a fixed stop on a drill bit. The proximal end of the second drill guide body may include an enlarged diameter head which may facilitate engagement with the fixed stop.  
         [0007]     The handle may be connected to at least one of the first drill guide body and the second drill guide body. For example, the handle may be connected to the first drill guide body by a stem portion. The handle may be configured and dimensioned for grasping by a user&#39;s hand.  
         [0008]     According to another embodiment of the invention, the surgical drill guide may include a first drill guide body having a distal end for placement substantially adjacent a bone, a second drill guide body slidable with respect to the first drill guide body and having a proximal end for contacting a portion of a drill bit, a handle associated with at least one of the first drill guide body and the second drill guide body, and a locking member movable between a first position where it substantially prevents sliding of the second drill guide body with respect to the first drill guide body, and a second position where it permits sliding of the second drill guide body with respect to the first drill guide body, wherein the locking member is resiliently biased to the first position. The locking member may engage a plurality of detents defined on the second drill guide body.  
         [0009]     The drill guide may further include a detent mechanism for releasably retaining the position of the first drill guide body with respect to the second drill guide body in predefined increments, and the locking member may engage a portion of the detent mechanism when the locking member is in the first position. For example, the locking member may engage a detent body.  
         [0010]     The locking member may be located between the handle and the first drill guide body and the second drill guide body. For example, the drill guide may include a stem portion extending between the handle and the first drill guide body, wherein the locking member is located on the stem portion, in which case the locking member may be slidable on the stem portion.  
         [0011]     According to yet another embodiment of the invention, the drill guide may include a first drill guide body having a distal end for placement substantially adjacent a bone, a second drill guide body slidably disposed within the first drill guide body, the second drill guide body having a proximal end for contacting a portion of a drill bit, a handle associated with at least one of the first drill guide body and the second drill guide body, and a detent body slidable with respect to at least one of the first drill guide body and the second drill guide body, wherein at least one of the first drill guide body and the second drill guide body includes a plurality of detents and the detent body is resiliently biased into engagement with one or more of the plurality of detents. The detent body may be resiliently biased into engagement with one or more of the plurality of detents by a spring. The drill guide may include a stem portion extending between the handle and at least one of the first drill guide body and the second drill guide body, and the detent body may be slidable on the stem portion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The detailed description will be better understood in conjunction with the accompanying drawings, wherein like reference characters represent like elements, as follows:  
         [0013]      FIG. 1  is a side view of a first illustrative embodiment of a drill guide according to the present invention;  
         [0014]      FIG. 2  is a front view of the drill guide of  FIG. 1 ;  
         [0015]      FIG. 3  is side view of a first drill guide body of the drill guide of  FIG. 1 ;  
         [0016]      FIG. 4  is a side view of a second drill guide body of the drill guide of  FIG. 1 , with portions shown in cross-section;  
         [0017]      FIG. 5  is a top view of the second drill guide body of  FIG. 4 ;  
         [0018]      FIG. 6  is a cross-sectional view of a portion of the drill guide of  FIG. 1 , taken along line VI-VI of  FIG. 2 ;  
         [0019]      FIG. 7  is a side view of a detent body of the drill guide of  FIG. 1 ;  
         [0020]      FIG. 8  is side view of a locking member of the drill guide of  FIG. 1 ;  
         [0021]      FIG. 9  is a back view of the locking member of  FIG. 8 ;  
         [0022]      FIG. 10  is a side view of a plunger member of the drill guide of  FIG. 1 ;  
         [0023]      FIG. 11  is a side view of an alternative embodiment of the drill guide of  FIG. 1 ;  
         [0024]      FIG. 12  is a side view of another alternative embodiment of the drill guide of  FIG. 1 ; and  
         [0025]      FIG. 13  is a side view of an illustrative embodiment of a drill bit having a fixed stop. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     Referring to  FIGS. 1 and 2 , an illustrative embodiment of a surgical drill guide according to the present invention is shown. Drill guide  10  may generally include a handle  12 , a first drill guide body  14 , and a second drill guide body  16 . Drill guide  10  may also include a detent mechanism  18  (such as shown in detail in  FIG. 6 ) and/or a locking member  20 . First drill guide body  14  and second drill guide body  16  may be substantially tubular shafts that slide or telescope with respect to one another. According to one preferred embodiment, second drill guide body  16  may slide within first drill guide body  14  along a common longitudinal axis A 1 , however other configurations are possible. When second drill guide body  16  is received within first drill guide body  14 , the first and second drill guide bodies  14 ,  16  preferably define a common cannula for receiving a drill bit. By holding the drill guide  10  by its handle  12  and inserting a drill bit through the cannula, the user may control the insertion point and/or the orientation of the drill bit.  
         [0027]     First drill guide body  14  may include a distal end  22  and second drill guide body  16  may include a proximal end  24 . By sliding second drill guide body  16  with respect to first drill guide body  14 , or vice versa, the distance X between distal end  22  and proximal end  24  may be adjusted. When used in conjunction with a drill bit having a known length (for example, the drill bit  100  shown in  FIG. 13 ), the distance X between the distal end  22  and the proximal end  24  may be adjusted to set the maximum depth to which the drill bit penetrates the bone. For example, the distal end  22  of the first drill guide body  14  may be placed substantially adjacent the bone, and drill bit  100  may be inserted into the cannula in the first and second drill guide bodies  14 ,  16  and drilled into the bone until a fixed stop  102  (or other enlarged diameter portion) located a predetermined distance from the tip  104  of the drill bit contacts the proximal end  24  of the second drill guide body  16 , at which point the first and second drill guide bodies  14 ,  16  prevent further penetration of the drill bit  100  into the bone. One of ordinary skill in the art will appreciate that drill bit  100  is shown for illustrative purposed only, and that drill guide  10  may be used with any drill bit known in the art, with or without a fixed stop.  
         [0028]     Handle  12  may be shaped and dimensioned to fit comfortably in the user&#39;s hand and may be provided with knurling, grooves, ridges, bumps, serrations, or other known surface treatments to increase a user&#39;s grip thereon. Additionally or alternatively, handle  12  may have a rubber, silicone or other coating.  
         [0029]     As shown in  FIG. 3 , one illustrative embodiment of first drill guide body  14  may comprise a substantially tubular shaft, and may have an upper portion  26  and a lower portion  28 . Upper portion  26  may have an inner diameter D 1  that is configured and dimensioned to receive, and preferably slidably receive, second drill guide body  16 . Lower portion  28  may have an inner diameter D 2  that is smaller than inner diameter D 1 , but is sufficient to allow the drill bit to extend therethrough. Alternatively, the inner diameter D 2  of lower portion  28  may also be configured and dimensioned to receive second drill guide body  16  (e.g., inner diameter D 2  may be equal to or larger than D 1 ). Lower portion  28  may also have a reduced outer diameter D 3  in comparison to upper portion  26 . The reduced outer diameter D 3  may facilitate minimally invasive insertion of first drill guide body  14  into the patient; and may also aid in accessing difficult to reach areas. According to an alternative embodiment contemplated by the present invention, the first drill guide body  14  may be received within the second drill guide body  16 .  
         [0030]     Still referring to  FIG. 3 , a graduated scale  30  may be provided on first drill guide body  14 , which may assist in determining the penetration depth of the drill bit, as will be discussed in more detail below. Alternatively, the graduated scale  30  may be provided on second drill guide body  16 . Distal end  22  may have two or more projections  32  formed thereon that may engage the bone and stabilize the position of distal end  22 . Projections  32  may have sharply pointed tips to ease penetration into the bone surface. A stem portion  34  may extend between first drill guide body  14  and handle  12 , however first drill guide body  14  may alternatively be connected directly to handle  12 . Handle  12  and stem portion  34  may be formed integrally, or as two separate points that are joined together. Preferably, stem portion  34  and first drill guide body  14  are formed integrally, however other configurations are possible. It is also contemplated that second drill guide body  16  may be connected to handle  12  in addition to, or instead of, first drill guide body  14 , as will be understood by one of ordinary skill in the art from this disclosure.  
         [0031]     Referring to  FIGS. 4 and 5 , an illustrative embodiment of second drill guide body  16  is shown in detail. Second drill guide body  16  may comprise a substantially tubular shaft having an outer diameter D 4  (shown in  FIG. 4 ) that is dimensioned and configured for second drill guide body  16  to fit within first drill guide body  14 . For example, outer diameter D 4  may be slightly smaller than the inner diameter D 1  of first drill guide body  14 , allowing second drill guide body  16  to slide or telescope within first drill guide body  14 . Second drill guide body  16  may also have an inner diameter D 5  (shown in  FIG. 4 ) that is configured and dimensioned to receive the drill bit. Preferably, inner diameter D 5  is substantially equal to the inner diameter D 2  of the lower portion  28  of first drill guide body  14 , however other configurations and dimensions are possible. Second drill guide body  16  may have an enlarged diameter head  36  at proximal end  24 , which may serve to engage a fixed stop or other feature on the drill bit or drill.  
         [0032]     Head  36  may also facilitate gripping by the user in order to, for example, slide or telescope second drill guide body  16  with respect to first drill guide body  14 , or vice versa. Thus, head  36  may be provided with knurling, grooves, ridges, bumps, serrations, or other known surface treatments to increase a user&#39;s grip thereon. Alternatively, head  36  may have a rubber, silicone, or other coating. While not shown, it is contemplated that a lever or other mechanism may optionally be provided to cause second drill guide body  16  to slide or telescope with respect to first drill guide body  14 . For example, drill guide  10  may include a lever or other mechanism that a user may operate with the hand holding handle  12  to adjust the distance between distal end  22  and proximal end  24 , as will be appreciated by one of ordinary skill in the art.  
         [0033]     Still referring to  FIGS. 4 and 5 , second drill guide body  16  may include a peg  38  configured and dimensioned to prevent rotation of second drill guide body  16  within first drill guide body  14 . For example, peg  38  may fit within a track  40  defined in first drill guide body  14 , such as shown in  FIG. 2 . Peg  38 , or alternatively another part of second drill guide body  16 , may include a marker  42  (such shown in  FIG. 5 ) that works in conjunction with the graduated scale  30  on first drill guide body  14  to indicate the penetration depth of the drill bit (based, in part, on the distance X between proximal end  22  and distal end  24  and the length of the drill bit). Second drill guide body  16  may also include a plurality of detents  44 , such as shown in  FIG. 4 . As shown, the detents  44  may comprise one or more angular or V-shaped indentations defined on second drill guide body  16 , however other shapes and configurations are contemplated. For example, detents  44  may alternatively comprise one or more protrusions defined on second drill guide body  16 . Also, other embodiments are contemplated where the detents  44  are associated with or defined on the first drill guide body  14 . As will be explained in more detail below, detents  44  may form part of a detent mechanism for releasably retaining the position of the first drill guide body  14  with respect to the second drill guide body  16  in predetermined increments. Peg  38  may be oriented with respect to detents  44  in order to maintain detents  44  in proper alignment with other parts of the detent mechanism. As shown, detents  44  are diametrically opposite peg  38 , however other orientations are contemplated.  
         [0034]     Referring to  FIG. 6 , one illustrative embodiment of a detent mechanism  18  is shown in cross-section. Detent mechanism  18  may operate to releasably retain the position of the first drill guide body  14  with respect to the second drill guide body  16  in predefined increments. Thus, a user may adjust the first distance X (shown in  FIG. 1 ; defined between the distal end  22  of first drill guide body  14  and the proximal end  24  of second drill guide body  16 ) in predefined, known increments. When used in conjunction with a drill bit of a known length, this may permit incremental adjustment of the maximum penetration depth of the drill bit without the use of an external measuring device. This may also permit the user to adjust the maximum penetration depth of the drill bit without having to remove the drill guide  10  from the incision in the patient.  
         [0035]     Graduated scale  30  may be calibrated for use with a drill bit having a predetermined length. For example, by subtracting the first distance X (between proximal end  24  and distal end  22 ) from the length of the drill bit, the exposed length of the drill bit may be determined. Using this convention, graduated scale  30  may be provided with markings indicating predefined maximum drill penetration depths (e.g., between 10 mm and 50 mm in 2 mm increments, or between 10 mm and 60 mm in 2 mm increments). Accordingly, graduated scale  30  and marker  42  (located on peg  38 ) may be read by the user to determine the maximum drill penetration depth. This may, among other things, allow the user to measure the maximum penetration depth without the use of extra measuring devices, and/or may allow the user to change the maximum penetration depth while the drill guide is still positioned inside the incision.  
         [0036]     The detent mechanism  18  may comprise a detent body  46  (shown in detail in  FIG. 7 ) capable of engagement with one or more detents  44  formed on the first drill guide body  14  or the second drill guide body  16 . According to the illustrative embodiment shown, detent body  46  may be slidably mounted in a bore in stem  34 , however other configurations are possible. For example, detent body  46  may alternatively be mounted in or on the handle  12 , the first drill guide body  14 , the second drill guide body  16 , or any combination of these items. Detent body  46  may be resiliently biased into engagement with detents  44 , such as by a first coil spring  48  or other known resilient member.  
         [0037]     Interaction between detent body  46  and detents  44  preferably releasably retains the position of the first drill guide body  14  with respect to the second drill guide body  16  unless a sufficient force is applied to the drill guide bodies  14 ,  16  to change their relative positions. For example, in order to slide or telescope the second drill guide body  16  with respect to first drill guide body  14 , a user may be required to impart sufficient force to the second drill guide body  16  (substantially along the first axis Al) in order to cause detent body  46  to move backwards against the first spring  48  sufficiently to disengage from the detent  44  and move into engagement with the adjacent detent  44 . As shown in  FIG. 6 , detent body  46  may include an angular tip  50  and/or detents  44  may have corresponding angular shapes that act as ramps to cause detent body  46  to move away from second drill guide body  16  upon sliding of the second drill guide body  16  with respect to the first drill guide body  14  along first axis A 1 . Adjacent detents  44  may be spaced apart to provide the appropriate sized increments of the maximum drill bit penetration depth. Detents  44  may also extend over a sufficient distance to provide an appropriate range of adjustment of the maximum penetration depth. For example, according to one illustrative embodiment, adjacent detents  44  may be dimensioned and configured to provide depth adjustment from 10 mm to 50 mm in 2 mm increments.  
         [0038]     Referring to  FIGS. 6 and 7 , detent body  46  may also include a first pin  52  or other member extending transversely therethrough. First pin  52  may slide in a first elongated slot  54  (shown in  FIG. 3 ) provided in stem  34  or other part of drill guide  10 . Interaction between first pin  52  and first slot  54  may captivate detent body  46  on drill guide  10 , even if second drill guide body  16  is completely removed from the first drill guide body  14 . This may be beneficial, for example, to permit ultrasonic, steam or autoclave cleaning of the second drill guide body  16 . Other configurations and structures for captivating detent body  46  on drill guide  10  are contemplated by the present invention, as will be readily understood by one of ordinary skill in the art from this disclosure.  
         [0039]     Referring now to  FIGS. 1 and 6 , drill guide  10  may additionally or alternatively include a locking member capable of substantially preventing sliding of second drill guide body  16  with respect to first drill guide body  14 . For example, locking member  20  (shown in detail in  FIGS. 8 and 9 ) may be normally located in a first position (shown in  FIGS. 1 and 6 ) in which second drill guide body  16  is substantially prevented from sliding with respect to first drill guide body  14  (or vice versa) unless a user actively moves locking member  20  to a second position (not shown), for example, toward handle  12  in  FIGS. 1 and 6 . This feature may, among other things, help prevent the first and second drill guide bodies  14 ,  16  from inadvertently moving or sliding with respect to one another during the drilling process.  
         [0040]     As shown in  FIGS. 1 and 6 , locking member  20  may be located on stem portion  34 . According to the illustrative embodiment shown, locking member may have a substantially U-shaped cross-section (as shown in  FIG. 9 ) that fits over stem portion  34 , however other shapes and configurations are possible. A second pin  56  (shown in  FIGS. 8 and 9 ) may extend between the sides  58 ,  60  of locking member  20  and through a second elongated slot  62  in stem portion  34 . Additionally or alternatively, a third pin  64  (shown in  FIGS. 8 and 9 ) may extend between the sides  58 ,  60  of locking member  20  and through a third elongated slot  66  in stem portion  34 . The second and/or third pins  56 ,  64  may serve to secure locking member  20  on stem portion  34  so that locking member  20  can slide along stem portion  34  generally toward or away from the first and second body members  14 ,  16  (e.g., between the first and second positions). Locking member  20  may be biased towards the first position by, for example, a second coil spring  68  or other resilient member. In the illustrative embodiment shown, coil spring  68  may be located in second elongated slot  62  and press a plunger member  70  (also located in second elongated slot  62 ; shown in detail in  FIG. 10 ) against second pin  56  to bias locking member  20  toward the first position, however, other configurations are contemplated.  
         [0041]     When locking member  20  is in the first position, such as shown in  FIGS. 1 and 6 , a portion of locking member  20  may engage detent body  46  and prevent detent body  46  from moving sufficiently to disengage the detents  44  and allow the second drill guide body  16  to move or slide with respect to the first drill guide body  14 . For example, locking member  20  may have one or more blocking surfaces  71  that contact or engage first pin  52  (or other part of the detent mechanism  18  or detent body  46 ) when locking member  20  is in the first position. Blocking surfaces  71  are preferably angled with respect to detent body  46  such that the forces applied by detent body  46  on blocking surfaces  71  (when detent body  46  is moved or attempted to be moved out of engagement with detents  44 ) results in little or no forces tending to move locking member  20  from the first position toward the second position (i.e., a low pressure angle). When locking member  20  is moved to the second position by the user (e.g., sufficiently towards handle  12  in  FIGS. 1 and 6 ), the blocking surfaces  71  move sufficiently far out of contact with first pin  52  to allow detent body  46  to move far enough out of engagement with the detents  44  such that the first and second drill guide bodies  14 ,  16  can incrementally slide or telescope with respect to one another.  
         [0042]     As shown in  FIG. 11 , locking member  20  may alternatively pivot between the first position and the second position. For example, locking member  20  may pivot about a pivot pin  21  that extends through stem portion  34 . A spring biased plunger  23  or other member may bias locking member  20  into the first position (shown), in which blocking surfaces  71  engage first pin  52 , to prevent detent body  46  from moving sufficiently to allow the second drill guide body  16  to move or slide with respect to the first drill guide body  14 . The locking member  20  may be pivoted about pivot pin  21  to the second position (against the force of the spring biased plunger  23 ) in which position the blocking surfaces  71  are a sufficient distance from first pin  52  to allow detent body  46  to move far enough out of engagement with the detents  44  such that the first and second drill guide bodies  14 ,  16  can incrementally slide or telescope with respect to one another.  
         [0043]     As shown in  FIG. 12 , locking member  20  may alternatively engage the detents  44  themselves when locking member  20  is in the first position, thereby substantially preventing movement or sliding of the first drill guide body  14  with respect to the second drill guide body  16 , or vice versa.  
         [0044]     The locking member  20  is preferably configured and positioned so that it can be moved between the first and second positions by the thumb or finger of a hand holding the handle  12 , however other configurations and positions are contemplated. As shown in  FIG. 8 , locking member  20  may be provided with ridges  72  or other known surface treatments to increase a user&#39;s grip thereon, such as knurling, grooves, bumps, or serrations. Additionally or alternatively, locking member  20  may have a rubber, silicone, or other coating. Although locking member  20  is shown and described as slidably mounted to stem portion  34 , other configurations and locations are contemplated. For example, locking member  20  may alternatively or additionally be mounted in, on, or associated with handle  12 , first drill guide body  14 , second drill guide body  16 , and/or some other part of drill guide  10 .  
         [0045]     Drill guide  10  may be used to position, orient and/or measure the depth of holes to be drilled in bone tissue, such as, for example, a vertebra. By positioning distal end  22  against the vertebra and inserting a drill bit through the first and second drill guide bodies  14 ,  16 , drill guide  10  may be used to control the starting point of the hole to be drilled, and/or the angular orientation of the hole. Alternatively or additionally, drill guide  10  may be used to measure the depth of the hole. For example, when used in conjunction with a drill bit having a fixed stop or similar feature, the distance between the distal end  22  and the proximal end  24  may be adjusted to determine the maximum penetration depth of the drill bit (assuming, for example, that the drill bit is inserted into the first and second drill guide bodies  14 ,  16  until the fixed stop or other feature engages or contacts proximal end  24 ). Detent mechanism  18  may provide incremental adjustment of the maximum penetration depth, as explained above. Also, locking member  20  may prevent accidental or inadvertent adjustment of the distance between the distal end  22  and proximal end  24  during drilling or other operations. Also, due to the configuration drill guide  10 , a user may incrementally adjust the maximum penetration depth to a known value without the necessity of moving drill guide  10  away from the drilling site. One of ordinary skill in the art will appreciate that drill guide  10  may be used with other bone tissue besides the vertebrae, such as, for example, long bones.  
         [0046]     While it is apparent that the illustrative embodiments of the invention herein disclosed fulfill the objectives stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. For example, the first drill guide body may alternatively slide or telescope within the second drill guide body; or the detent body may alternatively engage or contact the first drill guide body  14  or other portion of the drill guide. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.