Patent Publication Number: US-2021186531-A1

Title: Surgical tool guide

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority on U.S. Patent Application No. 62/672,131 filed May 16, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to surgical devices and, more particularly, to a guide for use with a surgical tool. 
     BACKGROUND 
     Pedicle screws are a particular type of bone screw designed for implantation into a vertebral pedicle in the context of spine surgery. Such pedicle screws are used to correct deformities and/or to treat trauma. Similar to other bone screws, pedicle screws may be used in instrumentation procedures to affix rods and plates to the spine. Pedicle screw may also be used to immobilize part of the spine to assist fusion by holding bony structures together. 
     In order to position and insert pedicle screws in place, the surgeon typically uses fluoroscopy or x-ray imagery to determine the appropriate depth and angle for screw placement. The most commonly used technique for pedicle screw placement is a free-hand technique in which the surgeons uses their knowledge of anatomy, visual references, and feel to position and install a guide wire at the desired location and angle, and the guide wire is subsequently used to ensure that screws are correctly placed within vertebral pedicles. Alternative techniques include image guidance systems or computer-assisted surgery (CAS) system which, while often effective, are relative complex, have high associated costs, and require increased operation time. 
     The lack of adequate guidance for surgeons can in some situations cause screw misplacement. Misplacement of pedicle screws can cause a variety of problems, ranging from relatively minor issues such as weakness or sensory loss, to more major consequences such as paralysis. 
     SUMMARY OF THE INVENTION 
     There is accordingly provided a surgical tool guide comprising: an anchor body extending between a proximal end and a distal end along an anchor axis, the anchor body having a piercing element at the proximal end adapted to pierce bone tissue and to anchor the anchor body thereto; an angle adjustor including an arcuate body arcuately extending between two opposed ends, visual angle markings displayed on a surface of the arcuate body, the angle markings indicative of measured angles therebetween, the angle adjustor mounted to the anchor body between the proximal end and the distal end; a guide including a tubular body cannulated along a longitudinal length thereof to define a guide passage extending therethrough along a guide axis, the guide mounted to the angle adjustor such that the guide axis intersects the anchor axis at a target surgical point and an angle is defined between the anchor axis and the guide axis, the guide passage adapted to receive and guide a surgical tool therethrough; and at least one of the anchor body and the guide displaceable relative to the other along the angle adjustor to vary at least one of the angle and a depth of the target surgical point, the depth defined between the piercing element and the target surgical point along the anchor axis. 
     The surgical tool guide as defined herein may also include, in whole or in part, and in any combination, one or more of the following features. 
     At least one of the anchor body and the guide is displaceable relative to the angle adjustor in a corresponding direction along one of the anchor axis and the guide axis. 
     The anchor body includes length markings displayed on at least an outer surface portion of the anchor body, the outer surface portion intersecting the angle adjustor upon mounting the anchor body to the angle adjustor, the length markings indicative of measured lengths therebetween. 
     At least a portion of the anchor body is radiopaque such that said portion is impenetrable to X-rays. 
     The anchor body is made from a unitary corpus. 
     The anchor body includes at least one handle that is made from a radiolucent material. 
     The handle is disposed along the anchor axis at a distal end of the anchor body opposite the piercing element at the proximal end. 
     The at least one handle is disposed at a length perpendicular to the anchor axis. 
     The tubular body of the guide includes at least length markings displayed on an outer surface portion of the guide body, the outer surface portion intersecting the angle adjustor upon mounting the guide body to the angle adjustor, the length markings indicative of measured lengths therebetween. 
     The guide body includes a proximal outlet opening having a sharp edge adapted to engage and penetrate skin tissue. 
     The angle adjustor includes a base fixed to one end of the arcuate body, the defining a bore therethrough that receives a locating sleeve, the base being displaceable along the locating sleeve to vary a vertical position of the angle adjustor and thus the guide body mounted thereto. 
     The guide includes an adjustment block that is displaceable along the arcuate body of the adjustment mechanism, the adjustment block defining a bore therethrough receiving the tubular guide body. 
     There is also provided a surgical tool kit comprising: a surgical tool; an anchor body extending between a proximal end and a distal end along an anchor axis, the anchor body having a piercing element at the proximal end adapted to pierce bone tissue and to anchor the anchor body thereto; an angle adjustor arcuately extending between two opposed ends, the angle adjustor having visual angle markings displayed on a surface of the angle adjustor between the two opposed ends, the angle markings indicative of measured angles therebetween, the angle adjustor mounted to the anchor body between the proximal end and the distal end; a guide body cannulated along a longitudinal length thereof to define a guide passage extending therethrough along a guide axis, the guide body mounted to the angle adjustor such that the guide axis intersects the anchor axis at a target surgical point and an angle is defined between the anchor axis and the guide axis, the guide passage adapted to receive and guide a surgical tool therethrough; and at least one of the anchor body and the guide body displaceable relative to the other along the angle adjustor to vary at least one of the angle and a depth of the target surgical point, the depth defined between the piercing element and the target surgical point along the anchor axis. 
     The surgical tool kit as defined herein may also include, in whole or in part, and in any combination, one or more of the following features. 
     The surgical tool includes length markings displayed on at least an outer surface portion of the surgical tool, the length markings indicative of measured lengths therebetween. 
     At least one of the anchor body and the guide body is displaceable relative to the angle adjustor in a corresponding direction along one of the anchor axis and the guide axis. 
     The anchor body includes length markings displayed on at least an outer surface portion of the anchor body, the outer surface portion intersecting the angle adjustor upon mounting the anchor body to the angle adjustor, the length markings indicative of measured lengths therebetween. 
     At least a portion of the anchor body is radiopaque such that said portion is impenetrable to X-rays. 
     The anchor body includes at least one handle that is made from a radiolucent material. 
     The at least one handle is disposed along the anchor axis at a distal end of the anchor body opposite the piercing element at the proximal end. 
     The handle is disposed at a length perpendicular to the anchor axis. 
     The guide body includes at least length markings displayed on an outer surface portion of the guide body, the outer surface portion intersecting the angle adjustor upon mounting the guide body to the angle adjustor, the length markings indicative of measured lengths therebetween. 
     The guide body includes a proximal outlet opening having a sharp edge adapted to engage and penetrate skin tissue. 
     In another aspect, there is alternately provided a surgical tool guide comprising an anchor body extending between a proximal end and a distal end along an anchor axis, the anchor body having a piercing element at the proximal end adapted to pierce bone tissue and to anchor the anchor body thereto; an angle adjustor arcuately extending between two opposed ends, the angle adjustor having visual angle markings displayed on a surface of the angle adjustor between the two opposed ends, the angle markings indicative of measured angles therebetween, the angle adjustor mounted to the anchor body between the proximal end and the distal end; a guide body cannulated along a longitudinal length thereof to define a guide passage extending therethrough along a guide axis, the guide body mounted to the angle adjustor such that the guide axis intersects the anchor axis at a target surgical point and an angle is defined between the anchor axis and the guide axis, the guide passage adapted to receive and guide a surgical tool therethrough; and at least one of the anchor body and the guide body displaceable relative to the other along the angle adjustor to vary at least one of the angle and a depth of the target surgical point, the depth defined between the piercing element and the target surgical point along the anchor axis. 
     In yet another aspect, there is alternately provided a surgical tool kit comprising a surgical tool; an anchor body extending between a proximal end and a distal end along an anchor axis, the anchor body having a piercing element at the proximal end adapted to pierce bone tissue and to anchor the anchor body thereto; an angle adjustor arcuately extending between two opposed ends, the angle adjustor having visual angle markings displayed on a surface of the angle adjustor between the two opposed ends, the angle markings indicative of measured angles therebetween, the angle adjustor mounted to the anchor body between the proximal end and the distal end; a guide body cannulated along a longitudinal length thereof to define a guide passage extending therethrough along a guide axis, the guide body mounted to the angle adjustor such that the guide axis intersects the anchor axis at a target surgical point and an angle is defined between the anchor axis and the guide axis, the guide passage adapted to receive and guide a surgical tool therethrough; and at least one of the anchor body and the guide body displaceable relative to the other along the angle adjustor to vary at least one of the angle and a depth of the target surgical point, the depth defined between the piercing element and the target surgical point along the anchor axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying figures in which: 
         FIG. 1  is a side view of a surgical tool guide of the present disclosure; 
         FIG. 2A  is a schematic side view of the surgical tool guide of  FIG. 1  and a surgical tool used in connection therewith; 
         FIG. 2B  is a posterior elevational view of a vertebrae showing insertion and target points relevant to the surgical tool guide of  FIG. 1 ; 
         FIG. 2C  is a side elevational view of the vertebrae of  FIG. 2B ; 
         FIG. 3A  is a side elevational view of the surgical tool guide of  FIG. 1  having an additional handle; 
         FIG. 3B  is perspective view of an exit aperture of the surgical guide of  FIG. 1  according to an embodiment; 
         FIG. 3C  is perspective view of the exit aperture of the surgical guide of  FIG. 1  according to another embodiment; 
         FIG. 4  is a schematic side view of a surgical tool; 
         FIG. 5  is a side elevational view of a surgical tool guide, according to another embodiment; 
         FIG. 6A  is a side elevational view of the exit aperture of  FIG. 3B , according to some embodiments; 
         FIG. 6B  is a top elevational view of the exit aperture of  FIG. 6A ; 
         FIG. 7  is a perspective view of a surgical tool guide of the present disclosure; 
         FIG. 8  is a side elevational view of the surgical tool guide of  FIG. 7 ; and 
         FIG. 9  is a cross-sectional view taken through line  9 - 9  in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a surgical tool guide  10  for guiding a surgical tool  12  during surgery or other medical procedures. The tool guide  10  can allow a health professional, such as a surgeon, to improve the accuracy of placement and positioning of the surgical tool  12  relative to a tissue  11  of a patient. The tissue  11  of the patient may refer to a bone tissue of the patient. More particularly, the tool guide  10  may allow the surgeon to make incremental and quantifiable adjustments in the position of the surgical tool  12 , which allows the surgeon to fine tune a trajectory of the surgical tool  12  intra-operatively in order to obtain the correct placement of the surgical tool  12  relative to the patient&#39;s tissue  11 . This may contribute to reducing the amount of trial-and-error that a surgeon needs to perform in order to find the correct trajectory of the surgical tool  12 , which can help to improve safety and reduce the duration of surgical operations. The tool guide  10  may be particularly suited for those surgical operations during which the surgeon employs “free hand” techniques. 
     The tool guide  10  is described herein in the context of spinal surgery, and more particularly, in the context of implanting guide wires, pedicle screws, or both, into vertebral pedicles. Similarly, the surgical tool  12  is described as being one commonly used for such spinal surgeries, and can be any one of a guide wire, an awl, a feeler, a Jamshidi™ needle, and a pedicle screw. However, the tool guide  10  can also be used during surgery on other parts of the body, and the present disclosure does not limit it to being used only during spinal surgery. Similarly, the surgical tool  12  is not limited to being a spinal surgery tool. Various types of other surgical devices and tools are therefore within the scope of the present disclosure depending on the surgical operation being performed. For example, the tool guide  10  may be used in anesthetic procedures, nerve block and catheter placement pre-op or post-op using ultrasound, and the like. 
     As will be discussed in greater detail herein, the tool guide  10  can be used with intra-operative image, typically X-ray imaging or fluoroscopy, to further assist the surgeon in guiding the surgical tool  12 . Depending on the surgical procedure and the material from which the tool guide  10  is made, the tool guide  10  can be adapted for one-time use, or can be autoclaved for sterilisation, and therefore, repeated use. 
     The tool guide  10  has an anchor body  14  to support and/or stabilize the tool guide  10  relative to the tissue  11 , a guide body  16  to guide the surgical tool  12  toward the tissue  11  and an angle adjustor  18  to adjust an angle between the anchor body  14  and the guide body  16 . 
     The angle adjustor  18  is curved in the shape of an arch (i.e. it is arcuate) along its length between its opposed ends. As will be explained in more detail below, the angle adjustor  18  helps to determine and/or adjust an angle α between the anchor body  14  and the guide body  16 . For example, the angle adjustor  18  therefore has visually-observable angle markings  20  that are displayed on one of the exposed surfaces of the angle adjustor  18  so that the surgeon or the medical professional can adjust and/or determine the angle α. The angle markings  20  can indicate measured angles therebetween. Examples of angle markings  20  include numerical angle values, colour schemes, gradations, or other visual indicia that are indicative of the angle α. For example, the angle markings  20  can be displayed similar to markings on a protractor. In other words, the angle adjustor  18  can be used in a similar way as the protractor such that a first reference is specified, and a second reference can be determined at an angle relative to the first reference to adjust the angle between the first reference and the second reference. Each angle marking  20  may define a corresponding direction extending radially toward a center of the angle adjustor  18 . The corresponding direction is intended to indicate a ray, also known as a side of the angle, which can be used to form an angle defined by two rays lying in a plane. The corresponding direction may be illustrated as a line or otherwise on the angle adjustor  18  to indicate the side of the angle α. In an alternate embodiment, the tool guide  10  includes an electronic display to visually display the value for the angle α. This display may be integrated into the tool guide  10 , or may be removably attached thereto. In yet another alternate embodiment, an accelerometer is used to determine the angle α, which may also be in communication with the visual display for the purposes of displaying the angle as determined by the accelerometer. 
     The anchor body  14  may be mounted to the angle adjustor  18  at any selected point thereon. For example, the anchor body  14  may be mounted at a first angle marking  20 A of the angle markings  20 . The anchor body  14  is elongated between two opposed outer distal end  22  and inner proximal end  24  along an anchor axis  14 A. In use, when the anchor body  14  is mounted to the angle adjustor  18 , the anchor body  14  is elongated along the corresponding direction of the first angle marking  20 A. As such, the anchor body  14  forms the first side of the angle α. The anchor body  14  may be made from a unitary corpus. In the depicted embodiment of  FIG. 1 , the anchor body  14  is mounted to the angle adjustor  18  such that the opposed outer distal end  22  and the inner proximal end  24  of the anchor body  14  are on opposed sides of the angle adjustor  18 . 
     The inner proximal end  24  has a piercing element  26  that is used to pierce the tissue  11  of the patient. For example, the piercing element  26  may be used to pierce a cortical bone tissue of a vertebra to anchor the anchor body  14  to the vertebrae at an anchor point A. The piercing element  26  is radiopaque so that it at least partially obstructs the passage of radiant energy, such as X-rays, and thus remains visible during intraoperative imaging. Alternately, at least a portion of the anchor body  14 , in addition to the piercing element  26 , may be radiopaque. The term radiopaque may also refer to a state of being impenetrable to X-rays and other radiation. 
     The anchor body  14  is solid throughout at last a majority of its longitudinal extent, in that it is not cannulated and is not intended to receive a guide wire or a surgical tool therethrough. 
     In the embodiment shown in  FIG. 1 , the anchor body  14  may be manipulated by the medical professional to be anchored within cortical bone tissue of the vertebrae at the anchor point A. The anchor body  14  can therefore include any accessories that facilitate this functionality. In the depicted embodiment of  FIG. 1 , for example, the anchor body  14  has a handle  28  located at the outer distal end  22  of the anchor body  14  to facilitate manipulation of the anchor body  14  and the tool guide  10 , by the medical professional. The handle  28  may be made from a radiolucent material that is relatively penetrable by X-rays or other forms of radiation. The term radiolucent material is intended to refer a material that is at least more penetrable than a substantially radiopaque metal or metal alloy. The term radiolucent may also refer to a state of being transparent to X-rays. 
     The guide body  16  may be mounted to the angle adjustor  18  at any suitable point thereon. For example, the guide body  16  may be mounted at a second angle marking  20 B of the angle markings  20 . The guide body  16  is elongated between two opposed distal inlet aperture  30  and proximal exit aperture  32  along a guide axis  14 B. In use, when the guide body  16  is mounted to the angle adjustor  18 , the guide body  16  is elongated along the corresponding direction of the second angle marking  20 B. As such, the guide body  16  forms the second side of the angle α. 
     Unlike the solid anchor body  14 , the guide body  16  is cannulated and thus defines a hollow interior passage that extends along at least some of its length (and in one particular embodiment, its entire longitudinal extent) to guide the surgical tool  12  to a target surgical area or point B in the vertebrae. The point B may indicate the center of the angle adjustor  18 . The guide body  16  defines an internal and closed perimeter guide passage  34 , which extends through the guide body  16  between distal inlet aperture  30  and the proximal exit aperture  32 , which may be positioned within the tissue  11  of the patient during use of the tool guide  10 . In use, the guide passage  34  may extend along the corresponding direction of the second angle marking  20 B. As will be explained in greater detail below, the guide passage  34  is positioned and sized to receive the surgical tool  12  therein via the inlet aperture  30  and to guide the surgical tool  12  through the guide body  16  to exit therefrom at the exit aperture  32 . 
     In use, the angle adjustor  18  may divide the guide body  16  between a first length  16 A and a second length  16 B. The first and second lengths  16 A,  16 B are lengths of the guide body  16  above and below, respectively, the angle adjustor  18 . The first and second lengths  16 A,  16 B may be adjusted by displacing the guide body  16  relative to the angle adjustor  18  in the corresponding direction of the second angle marking  20 B. Stated differently, the guide body  16  is displaceable along its longitudinal axis so as to adjust the distance of the guide body  16  relative to the target surgical point B in the vertebrae. 
     In the depicted embodiment, the angle adjustor  18  and the guide body  16  mounted thereto are displaceable along direction L relative to the anchor body  14 . The anchor body  14  may have a locking mechanism  36  to allow and arrest displacement of the angle adjustor  18  along an axis of the anchor body  14 . More particularly, the angle adjustor  18  and the guide body  16  mounted thereto are displaceable in the direction L parallel to the axis of the anchor body  14  towards and away from the target surgical point B. In the embodiment shown, the direction L is the same as the corresponding direction of the first angle marking  20 A. By displacing the angle adjustor  18  and the guide body  16  in this manner, the medical professional is able to vary the distance D between the anchor point A and the target surgical point B. 
     One or both of the anchor body  14  and the guide body  16  are displaceable relative to the other along the angle adjustor  18  to adjust the angle α between the anchor body  14  and the guide body  16 . Stated differently, one or both of the anchor body  14  and the guide body  16  may be slidingly displaced along the angle adjustor  18  toward and away from one another to adjust the angle α measured between them. The angle α can have any suitable range. For example, the angle α can range between 0° and 45° degrees. The guide body  16  may also have a locking mechanism  38  to allow and arrest displacement of the guide body  16  along the angle adjustor  18 . For example, the anchor body  14  may be positioned at the first angle marking  20 A indicating 0 degrees. The guide body  16  may be positioned at the second angle marking  20 B indicating 20 degrees if the medical professional has determined that the angle α is 20 degrees. Stated differently, the anchor body  14  and the guide body  16  are positioned to adjust the angle α therebetween. 
     The use of two relatively thin devices, the anchor body  14  and the guide body  16 , may limit the size of the surgical incision needed to effect the surgical operation of the vertebrae. Indeed, the size of the surgical incision can be limited to the area defined by the circumference of the anchor body  14  and the guide body  16 . 
     Referring to  FIGS. 2A to 2C , the use of the tool guide  10  will be described. In operation, an appropriate incision in the skin of the patient is made, and the anchor body  14  is inserted through the incision until the piercing element penetrates into the cortical bone tissue of the vertebrae  40  to anchor the tool guide  10  at the anchor point A. In the depicted embodiment, the medical professional attempts to anchor the anchor body  14  at a center of the pedicle  42 , as viewed in an anterior-posterior radiographic image (i.e. in the coronal plane), as shown in  FIG. 2C . 
     A distance D from the anchor point A to the target surgical point B in the pedicle is then determined. This projection distance D is a measure of a depth into the vertebrae  40  to the target surgical point B. In the depicted embodiment, the distance D is determined from intraoperative radiographic images, such as the image of the vertebrae in the sagittal plane shown in  FIG. 2C . The distance D may also be determined pre-operatively using X-rays, CT scans, MRI scans, and the like. As can be seen, the anchor point A is spaced from the target surgical point B by the distance D. In an alternate embodiment, the medical professional supplies the distance D from the known geometry of the vertebrae  40 . For example, it is known that the size of the average pedicle is about 20 mm. 
     The guide body  16  is then positioned relative to the anchor body  14  as a function of the distance D to the target surgical point B in the pedicle. When the distance D is known, the appropriate angle α can be determined. For example, using trigonometry based on the known lengths of the guide body  16 , and the known length of the anchor body  14  plus distance D, the angle α is determinable. The angle α defines the orientation along which the surgical tool  12  will be inserted. 
     The surgical tool  12  is then inserted through the hollow guide body  16  to penetrate into the vertebrae  40  to the target surgical point B within the pedicle. In the depicted embodiment, the surgical tool  12  includes a guide wire  44  coupled to a handle  46 . The handle  46  is manipulated by the medical professional to insert the guide wire  44  through the guide passage  34  of the guide body  16  to perforate the cortex bone tissue in proximity to the target surgical point B. The surgical tool  12  can include other devices as well, such as a pedicle screw. 
     Referring to  FIG. 3A , another handle  48  is shown attached to the anchor body  14 . The handle  48  may be used by the medical professional to manipulate the anchor body  14 , the tool guide  10 , or both, while keeping the hand of the medical professional away from X-rays or other radiation. The handle  48  is removably attached to the anchor body  14  at a distance along a length perpendicular to the anchor body  14 . The distance may depend on the configuration of the tool guide  10  and location and strength of the X-rays. 
     The anchor body  14  includes length markings  50  on an outer surface thereof or on a portion of the outer surface. The length markings  50  are disposed on the outer surface that would intersect the angle adjustor  18  when the anchor body  14  is mounted to the angle adjustor  18 . The length markings  50  indicate measured lengths between them. The length markings  50  may be used to adjust the displacement of the anchor body  14  relative to the angle adjustor  18 . 
     The guide body  16  includes length markings  52  on an outer surface thereof or on a portion of the outer surface. The length markings  52  are disposed on the outer surface that would intersect the angle adjustor  18  when the guide body  16  is mounted to the angle adjustor  18 . The length markings  52  indicate measured lengths between them. The length markings  52  may be used to adjust the displacement of the guide body  16  relative to the angle adjustor  18 . 
     Referring to  FIGS. 3B-3C , examples of the exit aperture  32  or outlet opening are shown.  FIG. 3B  illustrates a blunt edge  32 A of the exit aperture  32  and  FIG. 3C  illustrates a sharp edge  32 B of the exit aperture  32 . The sharp edge  32 B may be adapted to engage and penetrate the skin tissue  11  of the patient. In some embodiments, the exit aperture  32  may have a retractable sharp edge  32 B which can retract and extend beyond the blunt edge  32 A. The guide body  16  may include a spring-loaded mechanism to retract and extend the sharp edge  32 B. 
     Referring to  FIG. 4 , the surgical tool  12  is shown. The surgical tool  12  may form part of a surgical tool kit that includes the tool guide  10  and the surgical tool  12 . The surgical tool  12  may include pins  54  extending perpendicularly relative to the surgical tool  12 . The pins  54  are adapted to engage the guide body  16  to provide stopping positions between the surgical tool  12  and the guide body  16 . The pins  54  may also determine a depth of the surgical tool  12  relative to the guide body  16 . For example, the pins  54  may be marked to reveal a length of the surgical tool  12 . In use, the surgical tool  12  may be positioned such that a pin  54  indicating the desired length or depth of the surgical tool  12  into the guide body  16  is engaged with a reference position of the guide body  16 . 
     The surgical tool  12  may also include length markings on an outer surface thereof or on a portion of the outer surface. The length markings are disposed on the outer surface that would intersect the reference position when the surgical tool is inserted into the guide body  16 . The length markings indicate measured lengths between them. The length markings may be used to adjust the displacement of the surgical tool relative to the guide body  16 . 
     Referring to  FIG. 5 , another embodiment of the surgical tool guide  100  is shown. The guide tool  100  is similar to the guide tool  10  described above. In the embodiment shown in  FIG. 5 , the guide body  16  is fixed to the angle adjustor  18  at one of the angle markings  20 . The surgical tool  100  may have multiple combined angle adjustor  18  and guide body  16  fixed at different angles. For example, a first guide body  16  may be mounted to a corresponding angle adjustor  18  at an angle marking of 30 degrees and a second guide body  16  may be mounted to a corresponding angle adjustor  18  at an angle marking of 45 degrees. In use, the anchor body  14  can be mounted to one of the combined guide body  16  and angle adjustor  18  to adjust the angle α between the anchor body  14  and the guide body  16 . 
     Referring to  FIGS. 6A and 6B , a bumper  60  is shown attached to the guide body  16  between the inlet aperture  30  and the exit aperture  32 ,  32 A,  32 B. The bumper  60  may have any suitable shape and made from any suitable material to arrest the guide body  16  on the tissue of the patient. As such, the bumper  60  may prevent plunging the sharp edge  32 B excessively into the tissue of the patient. The bumper  60  is shown as a circumferential protrusion extending radially outward from the guide body  16 . In some embodiments, the bumper  60  may be integrally formed with the guide body  16 . In other embodiments, the bumper  60  is securely mountable to the guide body  16 . The location of the bumper  60  on the guide body  16  may depend upon the anatomy of the patient. 
     In light of the preceding, the tool guide  10 ,  100  disclosed herein may improve the accuracy of surgical tool placement, such as pedicle screw placement in spine surgery. The tool guide  10 ,  100  can improve the “free hand” technique employed by surgeons for some procedures, and may contribute to reducing the number of X-ray images that need to be generated, thereby reducing exposure to radiation. The tool guide  10 ,  100  helps to obtain more precise movement modifications to the trajectory of the tool. 
     In comparison to CAS or image-guidance techniques, the tool guide  10 ,  100  can be cost effective, much less time consuming, and simpler to use. The tool guide  10 ,  100  provides, for example, guide wire for pedicle screw placement in a quick and safe manner. It is expected that increasing screw placement accuracy improves the outcomes of surgical procedures. The tool guide  10 ,  100  may be used in spinal surgery, and form part of a pedicle screw placement kit. 
     Referring now to  FIGS. 7-9 , a surgical tool guide  210  is depicted. The surgical tool guide  200  operates in a similar manner to the surgical tool guide  10  as described above, and therefore will only be described generally, with a focus on any elements thereof that may differ from the guides already described herein. 
     The surgical tool guide  210  includes generally an anchor body  214  used to locate, support and/or stabilize the tool guide  210  relative to the patient tissue  11 , a guide body  216  which is used to guide the surgical tool  12  towards the tissue  11 , and an angular adjustment mechanism  218  which is used to adjust the angle α (see  FIG. 1 ) between the anchor body  214  and the guide body  216 , as described above. 
     The angular adjustment mechanism  218  includes an arcuate body  219  that is fixed relative to a base  217  which secured to the anchor body  214 . A central bore  221  (see  FIG. 9 ) extends vertically through this base  217  and receives a locating sleeve  223  therein. The locating sleeve  223  and the base  217  are displaceable relative to each other, such that the base can be slide vertically along the locating sleeve  223  to vary the vertical position of the base  217  and thus the entire angular adjustment mechanism  18 . A locking nut  225  is used to secure the base  217  in the desired location on the locating sleeve  223 . As such, the vertical position of the entire angular adjustment mechanism  218  can be adjusted, and secured in a desired position. 
     Much as per the embodiment of  FIG. 1 , the anchor body  214  includes a handle  228  located at the outer distal end  222  of the anchor body  214  to facilitate manipulation of the anchor body  214  and the tool guide  210 . In this embodiment, a needle and/or guidewire may also be inserted through the anchor body  214 , and can be secured in place with an outer locking nut  230 . 
     As best seen in  FIG. 8 , the outer surfaces of both the adjustment sleeve  223  and the arcuate body  219  of the adjustment mechanism include visually-observable markings  20  thereon, so that the surgeon or medical professional can see, adjust and/or measure the relative position and orientation of the guide body  16  and thus the surgical tool  12  guided thereby. 
     The guide body  216  includes a tubular body  235 , that defines the closed perimeter bore therethrough for receiving the surgical tool  12 . The hollow tubular body  235  is received within a displaceable adjustment block  232  (hereinafter, simply “block”  232 ) that is mounted to the guide body  216  of the adjustment mechanism for relative sliding displacement therealong. The angular position of the guide body  216  relative to the anchor body  214  can therefore be adjusted by sliding the block  232  along the arcuate body  219  of the adjustment mechanism  218 , thereby changing the relative angular position of the tubular body  235  relative to the vertical reference defined by the anchor body  214  (i.e. thereby modify angle α (see  FIG. 1 ). Once the desired angle is reached, the block  232  is locked in position by tightening the locking nut  236 , which secures the block  232  in place on the arcuate body  219  and thus prevents any further relative movement therebetween. 
     If necessary, the vertical position of the tubular body  235  can also be adjusted, without changing the desired angle α between the tubular body  235  of the guide body  216  and the anchor body  214 . The tubular body  235  of the guide body  216  can be slid axially within the bore defined in the block  232 , and locked in place using the further adjustment nut  238 . 
     The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.