Patent Publication Number: US-2022218363-A1

Title: Methods and apparatus for performing discectomy

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/282,656, filed on Feb. 22, 2019, which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to methods and apparatus for performing a discectomy. 
     BACKGROUND OF THE INVENTION 
     Bones and bony structures are susceptible to a variety of weaknesses that can affect their ability to provide support and structure. Weaknesses in bony structures have numerous potential causes, including degenerative diseases, tumors, fractures, and dislocations. Advances in medicine and engineering have provided doctors with a plurality of devices and techniques for alleviating or curing these weaknesses. 
     In some cases, the spinal column requires additional support in order to address such weaknesses. One technique for providing support is to extend a structure between adjacent bones, the structure connected at each end to a polyaxial screw “tulip”, or yoke, connected to a bone screw inserted within the bone. 
     Preparation of the intervertebral disc space includes maneuvering a cutting tool within a small space. Access to the disc space may be limited, as well, for example when conducting a minimally invasive procedure. The foregoing and other diseases often require the removal or shaping of body tissue through a minimal incision, for example in a laparoscopic procedure, where the tool must be sufficiently small to pass through a small opening in the body. 
     It is desirable to separate the nucleus from the annulus within the intervertebral disc space while also bring able to fit the disc prep tool through a small diameter cannula extending through the incision. Removal of tissue from the endplates of the vertebrae adjacent the disc space can be accomplished with various instruments. However, it is difficult to cut vertically through the disc so as to separate the degenerated nucleus from the annular tissue. It is also necessary to ensure that the annulus furthest away from the incision (e.g., contralateral in a lateral procedure) is not cut. It is also necessary to address the varying levels of curvature that different patients have when removing cartilaginous tissue from the endplates. 
     SUMMARY OF THE INVENTION 
     Embodiments of methods and apparatus for performing a discectomy are disclosed herein. In some embodiments, a surgical tool for use in a therapeutic treatment of a patient includes a handle; an upper arm coupled to the handle; a lower arm coupled to the handle; a pivot arm coupled to one of the upper arm or the lower arm via a first pivot pin; and an end effector pivotably coupled to the pivot arm via a second pivot pin, wherein actuation of the handle causes movement of the pivot arm and articulation of the end effector. 
     In some embodiments, a surgical tool for use in a therapeutic treatment of a patient, includes a handle extending from a proximal end to a distal end. an upper arm coupled to the handle; a lower arm coupled to the handle; a pivot arm coupled to one of the upper arm or the lower arm via a first pivot pin; and an end effector pivotably coupled to the pivot arm via a second pivot pin, wherein actuation of the handle causes movement of the pivot arm and articulation of the end effector. The handle includes a body having a central channel extending from a distal end to a point between the proximal end and the distal end; a carrier disposed around the body and having external threads; a knob surrounding the body and carrier, the knob having internal threads corresponding to the external threads of the carrier, wherein rotation of the knob causes linear translation of the carrier along an axis of the handle; an attachment arm disposed within the central channel and coupled to the carrier via a pin, wherein the attachment arm configured to mate with a corresponding feature of the surgical tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  depicts a discectomy instrument in a retracted position in accordance with embodiments of the present disclosure; 
         FIG. 2  depicts the discectomy instrument of  FIG. 1  in an extended position; 
         FIGS. 3A-3C  depict an articulating end of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 4A-4B  depict cross-sectional views of the articulating end effector of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 5A-5E  depict an adjustable stop for use with a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 6A-6B  depict an articulating end of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 7A-7C  depict cross-sectional views of the articulating end effector of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 8A-8B  depict close-up views of an articulating end effector of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 9A-9B  depict an articulating end effector of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 10A-10C  depict cross-sectional views of the articulating end effector of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 11A-11C  depict close-up views of an articulating end effector of a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 12A-12D  depict a removable handle for use with a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 13A-13C  depict an indicator disposed on the removable handle of  FIGS. 12A-12D  in accordance with embodiments of the present disclosure; 
         FIGS. 14A-14C  depicts cross-sectional views of the removable handle of  FIGS. 12A-12D  at different positions of the articulating portion; 
         FIG. 15  depicts an isometric view of an adjustable stop in accordance with embodiments of the present disclosure; 
         FIGS. 16A-16B  depict the adjustable stop of  FIG. 15  coupled to a discectomy tool in accordance with embodiments of the present disclosure; 
         FIGS. 17A-17B  depict cross-sectional views of the adjustable stop of  FIG. 15 ; 
         FIGS. 18A-18B  depict cross-sectional views of the adjustable stop of  FIG. 15 ; and 
         FIG. 19  depicts a k-wire in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , a surgical instrument, or tool  100  in accordance with some embodiments of the present disclosure will be described. In some embodiments, the tool  100  includes an articulating end effector  102 , in this embodiment a ring curette for cutting tissue. For example, tool  100  may be used to prepare vertebral endplates, or an intervertebral space, for insertion of a stabilizing implant. Tool  100  enables a large angle of articulation of end effector  102 , which can have various shapes, as will be discussed below. Moreover, tool  100  may be used to articulate one or more of any type of device, including but not limited to the examples of cutter, curette, pincher, grasper, light source, dilator, clamp, hose, retractor, sensor, other articulating tool, or optical device. Tool  100  further advantageously includes an extension  104 , a handle  106  connected to extension  104 , a moveable trigger  108 , and a trigger bias  110  operative to return trigger  108  to a starting position after actuation. 
     While a surgical instrument particularly benefits from the disclosure, it should be understood that any tool requiring a wide range of motion, insertable through a small opening, may be fabricated in accordance with the disclosure. This may include, for example, mechanical repair or assembly tools. 
     Extension  104  includes an upper arm  112  and a lower arm  114  which are mutually connected whereby lower arm  114  is affixed to handle  106 , and upper arm  112  is caused to slide relative to lower arm  114  as trigger  108  is actuated or operated. Lower arm  114  and upper arm  112  may be connected by any known means, including a dovetail or other mutually interlocking configuration, or lower arm  114  may form an enclosure or sleeve containing upper arm  112 . 
     In accordance with the disclosure, upper arm  112  and lower arm  114  are elongated and narrow, such that they may form a laparoscopic instrument passable into the body of a patient through a cannula extending through minimally invasive incision, for example though a stab type incision which may be less than 30 mm in length, for example about 15 mm in length, but may be larger as deemed therapeutically best by the medical practitioner. Typically, such instruments form a total width of less than 15 mm, and in most cases substantially less than 15 mm, for example about 6 mm or less. The upper arm  112  extends from a proximal end to a distal end. The distal end of the upper arm includes a channel  118 , through which a distal end of the lower arm  114  passes. 
       FIGS. 3A-3C  depict side views of the tool  100  in an initial position, intermediary position, and fully extended position of the end effector  102 , respectively.  FIGS. 4A and 4B  depict cross-sectional views of the tool  100  in the initial and fully extended positions, respectively. With reference to  FIGS. 3A-3C and 4A-4B , end effector  102  operates on an active pivoting mechanism which includes a first pivot pin  116 A, a second pivot pin  116 B, and a third pivot pin  116 C. The first pivot pin  116 A is fixed to the distal end of the lower arm  114  and a proximal end of a pivot arm  117 . The first pivot pin is configured to translate along the channel  118 . The second pivot pin  116 B is fixed to the end effector  102  and a distal end of the pivot arm  117 , thus allowing the second pivot pin  116 B to move about the third pivot pin  116 C, as discussed below. The third pivot pin  116 C is fixed to a distal tip  119  of the upper arm  112  and to the end effector  102 , thus allowing the end effector  102  to rotate about a pivot axis passing through the third pivot pin  116 C. As a result, when the trigger  108  is actuated, the lower arm  114  translates relative to the upper arm  112 , moving the lower arm  114  forward. This forward movement of the lower arm  114  pushes the second pivot pin  116 B beyond the first pivot pin  116 A (as shown in  FIGS. 3C and 4B ) because of the curvature of the pivot arm  117 . The movement of the second pivot pin  116 B beyond the first pivot pin  116 A advantageously provides a sweep angle of about 160°. Such a large sweep advantageously provides an improved ability to separate the nucleus of the disc from the annulus and allows for the insertion of the tool either in the initial position or in the fully extended position. The geometry of the end effector  102  (i.e., the opening in the ring curette) advantageously allows a portion of the pivot arm  117  to be disposed within the end effector  102  in the initial position, thus maintaining a low profile of the tool  100  during insertion. 
     In some instances, however, great care must be exercised not to cut through the annulus of the disc on the side of the disc space opposite insertion of the tool. In such instances, the surgeon may wish to limit the amount of travel of the end effector of the tool to a predetermined amount of travel. Typically, instruments are marked with length indicators and it is up to the surgeon to determine how far into the disc space the tool has been inserted or how far beyond a distal end of a cannula the tool extends based on these markings. As such, the inventors have developed an adjustable stop  500  configured to limit the amount of travel of the end effector of a surgical tool. The travel allowance can be adjusted within a range defined by the surgeon at the beginning of the surgery. However, the surgeon may also change that travel allowance mid-surgery, if necessary. 
       FIGS. 5A-5E  depict an adjustable stop  500  for use with a surgical tool (e.g., tool  100  described above) to limit the amount of travel of the end effector of the tool into the disc space. The adjustable stop  500  is coupled to a cannula  502  through which the tool is inserted into the disc space. Each tool includes a hard stop  504  (e.g., a collar or shoulder) that typically limits the amount of travel of the tool through the cannula  502 . The adjustable stop  500  is moved to a desired position along the cannula  502  such that when the hard stop  504  contacts the adjustable stop  500 , the tool cannot be advanced further into the cannula  502 . As a result, the distance traveled by the end effector of the tool beyond a distal end  506  of the cannula  502  is limited to a desired distance.  FIG. 5A  depicts the adjustable stop  500  positioned at the lowest position along a proximal portion of the cannula  502 . The tool protrudes beyond the distal end  506  of the cannula  502  a distance A at this stop position.  FIG. 5B  depicts the adjustable stop  500  position at the highest setting along the proximal portion of the cannula  502 . The tool protrudes beyond the distal end  506  of the cannula a distance B, which is less than the distance A, at this position. 
     In some embodiments, the position of the adjustable stop  500  is adjustable using interacting features on the proximal portion of the cannula  502 . In such an embodiment, the adjustable stop  500  includes an internal body  508  that includes a first set of teeth  510  that mate with a second set of teeth  512  on the cannula  502 . When the first and second sets of teeth  510 ,  512  are engaged, the adjustable stop  500  is prevented from moving along the cannula  502 . When the teeth are disengaged, the position of the adjustable stop  500  may be adjusted. To engage and disengage the teeth, the internal body is rotated such that the first set of teeth  510  are rotated out of engagement with the second set of teeth  512 . In some embodiments, to rotate the first set of teeth  510  out of engagement, a collar  514  of the adjustable  500  may be pulled back (i.e., proximally). The collar  514  includes a radially inward extending pin  516  that extends through a linear slot  518  formed in an outer housing  520  and a helical slot  522  formed in the internal body  508 .  FIG. 5D  depicts the adjustable stop  500  with the outer housing  520 .  FIG. 5E  depicts the adjustable stop  500  without the outer housing  520 . As the collar  514  is pulled back, its motion is constrained by pin  516  in the linear slot  518  and the internal body  508  is caused to rotate due to the motion of the pin  516  along the helical slot  522 . As depicted in  FIG. 5C , an internal spring  524  is disposed between the outer housing  520  and the internal body  508  to bias the collar  514  distally (i.e., towards a position in which the first and second sets of teeth  510 ,  512  are in engagement). 
     Referring now to  FIGS. 6A-8B , an end effector  602  of surgical tool  600  in accordance with some embodiments of the present disclosure will be described. As depicted in these figures, the end effector of the tool  600  may be a cup curette. Because the tool  600  is substantially similar to the tool  100  described above, only a distal portion of the tool  600  is depicted in these figures and described below.  FIGS. 6A and 7A  depict the distal end of the tool  600  in an initial position (i.e., insertion position) and  FIGS. 6B and 7C  depict the distal end of the tool  600  in a final position (i.e., fully extended position).  FIG. 7B  depicts the distal end of the tool  600  in an intermediate position. 
     The tool  600  is configured to be inserted into the disc space in the initial position ( FIGS. 6A and 7A ), and then articulated once inside. The articulation is controlled using a handle similar to the handle  106  discussed above. The articulation of the end effector  602  functions as an active pivot based on a two pin mechanism. A first pivot pin  616 A is fixed to the end effector  602  and a lower arm  614  of the tool. A second pivot pin  616 B is fixed only to the end effector  602 , thus allowing the second pivot pin  616 B to translate within an upper arm  612  of the tool  600 . As the handle is actuated, the upper arm  612  translates forward (i.e., distally) relative to the lower arm  614 . Because the second pivot pin  616 B is not fixed to the upper arm  612 , but instead allowed to translate, the end effector  602  begins to rotate about the first pivot pin  616 A. The actuation continues until the upper arm  612  reaches a physical stop. The physical stop can either be accomplished by a slot  618  into which the second pivot pin  616 B extends, or by some limitation on the handle used to actuate the tool  600 . 
     In some embodiments, the end effector  602  also includes passive articulation (depicted in  FIGS. 8A and 8B ), which is realized when the end effector  602  (i.e., the cup curette head) contacts an endplate adjacent to the disc space. Once contact occurs, the end effector  602  will remain aligned with the endplate as long as pressure is maintained. The entire tool  600  can then be pulled back and forth, as a standard cup curette, to remove tissue from the endplates. To achieve such passive articulation, the end effector  602  includes a third pivot point  616 C coupling a head  620  of the end effector  602  to a pivot arm  617 . The end effector  602  is allowed to pivot about the third pivot point  616 C. 
     The inventor has discovered that the active pivot of the tool  600  is advantageous because it does not suffer from the drawbacks associated with a tool having two fixed pivot pins, one that is translated and the other that is rotated about. The translating pin in such a device is always at a constant distance from the rotation pin, thus creating a radius. The passive pivot of the tool  600  advantageously accommodates the different endplate shapes of different patients. In contrast, a standard cup curette suffers from point loading, which can result in over-stress at a specific area of bone, potentially breaking through the endplate. 
     Referring now to  FIGS. 9A-11C , an end effector  902  of surgical tool  900  in accordance with some embodiments of the present disclosure will be described. As depicted in these figures, the end effector of the tool  900  may be a rake. Because the tool  900  is substantially similar to the tool  100  described above, only a distal portion of the tool  900  is depicted in these figures and described below.  FIGS. 9A and 10A  depict the distal end of the tool  900  in an initial position (i.e., insertion position) and  FIGS. 9B and 10C  depict the distal end of the tool  900  in a final position (i.e., fully extended position).  FIG. 10B  depicts the distal end of the tool  900  in an intermediate position. 
     Similar to the tool  600 , the tool  900  is configured to be inserted into the disc space in the initial position ( FIGS. 9A and 10A ), and then articulated once inside. The articulation is controlled using a handle similar to the handle  106  discussed above. The articulation of the end effector  902  functions as an active pivot based on a two pin mechanism similar to the one discussed above with respect to the tool  600 . A first pivot pin  916 A is fixed to the end effector  902  and a lower arm  914  of the tool. A second pivot pin  916 B is fixed only to the end effector  902 , thus allowing the second pivot pin  916 B to translate within an upper arm  912  of the tool  900 . As the handle is actuated, the upper arm  912  translates forward (i.e., distally) relative to the lower arm  914 . Because the second pivot pin  916 B is not fixed to the upper arm  912 , but instead allowed to translate, the end effector  902  begins to rotate about the first pivot pin  916 A. The actuation continues until the upper arm  912  reaches a physical stop. The physical stop can either be accomplished by a slot  918  into which the second pivot pin  916 B extends, or by some limitation on the handle used to actuate the tool  900 . 
     In some embodiments, the end effector  902  also includes passive articulation (depicted in  FIGS. 11A and 11B ), which is realized when the end effector  902  (i.e., the rake head) contacts an endplate adjacent to the disc space. Once contact occurs, the end effector  902  will remain aligned with the endplate as long as pressure is maintained. The entire tool  900  can then be pulled back and forth, as a standard cup curette, to remove tissue from the endplates. To achieve such passive articulation, the end effector  902  includes a third pivot point  916 C coupling a head  920  of the end effector  902  to a pivot arm  917 . The end effector  902  is allowed to pivot about the third pivot pin  916 C. As shown in  FIGS. 11A and 11B , the head of the end effector  902  may include an opening  930  surrounding the third pivot pin  916 C to allow the head  920  to pivot about the third pivot pin  916 C. As shown in  FIG. 11B , the opening  930  may include walls  932  to limit such pivoting by abutting against the pivot arm  917 .  FIG. 11C  depicts a top view of the head  920  of the end effector  902  (i.e., the rake head). 
     Referring to  FIGS. 12A-14C , a handle  1200  for use with a surgical tool (e.g., tool  600 ) in accordance with embodiments of the present disclosure will be described. Although reference is made to the tool  600  in the following description of the handle  1200 , it should be noted that any surgical tool requiring actuation (e.g., tools  100 ,  900 ) may be utilized with the handle  1200 . The handle  1200  may be a modular handle that can be attached to multiple tools such as, for example, the tools described above. Such a handle replaces conventional handles such as handle  106  discussed above. In some embodiments, the handle  1200  extends from a proximal end  1202  to a distal end  1204  and includes a central channel  1206  extending from a distal end  1204  to a point between the proximal and distal ends  1202 ,  1204 . The handle  1200  further includes an attachment arm  1208  disposed within the central channel  1206  and configured to mate with a corresponding feature of a tool to which the handle  1200  is attached. In some embodiments, the attachment arm  1208  includes a feature  1210  configured to receive a corresponding feature  1212  of the tool to which the handle  1200  is attached. In some embodiments, the feature  1210  may be a t-shaped slot, as shown in  FIGS. 12A-12C . However, the feature  1210  may alternatively have any geometry capable of attaching the handle  1200  to the tool. The attachment arm  1208  is moveable along an axis  1214  of the handle  1200 . As such, whichever portion of the tool the attachment arm  1208  is coupled to is also moved back and forth with the movement of the attachment arm  1208 . In some embodiments, the attachment arm is coupled to a portion of the tool that needs to be moved in order for an end effector (e.g.,  602 ) of the tool to articulate (e.g., one of the upper or lower arms  612 ,  614 ). 
     In some embodiments, the handle  1200  includes a knob  1216  having internal threads (not shown) that correspond to external threads  1218  of a carrier  1220 . The carrier  1220  surrounds a body  1221  of the handle  1200  and is coupled to the attachment arm  1208  via a pin  1222 . As such, when the knob  1216  is rotated, the threads cause the carrier  1220  to move back and forth along the body  1221 , which in turn also causes the attachment arm  1208  to move back and forth, thus also moving the portion of the tool to which the attachment arm  1208  is attached. 
     As depicted in  FIGS. 13A-13C , in some embodiments, the handle  1200  may include an indicator  1224  configured to indicate the angular position of the end effector relative to the tool. In some embodiments, the indicator  1224  includes numerical values  1223  written on a proximal surface of the body  1221  and a pointer  1229  on a proximal surface of an indicator body  1225 . In such an embodiment, the pin  1222  passes through a linear slot  1226  ( FIG. 14A ) formed in the body  1221  and a helical slot  1227  formed in the indicator body  1225  (similar to the adjustable stop  500  discussed above). As a result, rotation of the knob  1216  causes the linear movement of the carrier  1220 , which causes the pin  1222  to move along the linear slot  1226  and the helical slot  1227  as shown in  FIGS. 14A-14C . The movement of the pin along the helical slot  1227  causes the indicator body  1225  to rotate, thus also rotating the pointer  1229  causing it to point to the correct numerical value  1223  corresponding to the angular position of the end effector  602 , as depicted in  FIGS. 13A-13C . 
     Referring to  FIGS. 15-18B , an adjustable stop  1500  for use with a surgical tool (e.g., tool  100 ) to limit the amount of travel of the end effector (e.g., end effector  102 ) of the tool into the disc space in accordance with embodiments of the present disclosure will be described. Although reference is made to the tool  100  in the following description of the adjustable stop  1500 , it should be noted that any surgical tool requiring an adjustable stop (e.g., tools  600 ,  900 ) may be utilized with the adjustable stop  1500 . The adjustable stop  1500  is coupled to a cannula  1502  through which the tool is inserted into the disc space. Each tool includes a hard stop  1504  (e.g., a collar or shoulder) that typically limits the amount of travel of the tool through the cannula  1502 . The adjustable stop  1500  is moved to a desired position along the cannula  1502  such that when the hard stop  1504  contacts the adjustable stop  1500 , the tool cannot be advanced further into the cannula  1502 . As a result, the distance traveled by the end effector of the tool beyond a distal end  1506  of the cannula  1502  is limited to a desired distance.  FIGS. 16A and 17B  depict the adjustable stop  1500  positioned at the highest position along a proximal portion of the cannula  1502 . The tool protrudes beyond the distal end  1506  of the cannula  1502  a distance A at this stop position.  FIGS. 16B and 17A  depict the adjustable stop  1500  position at the lowest position along the proximal portion of the cannula  1502 . The tool protrudes beyond the distal end  1506  of the cannula a distance B, which is greater than the distance A, at this stop position. 
     In some embodiments, the position of the adjustable stop  1500  is adjustable using interacting features on the proximal portion of the cannula  1502 . In such an embodiment, the adjustable stop  1500  includes a moveable body  1508  that includes a first set of teeth  1510  that mate with a second set of teeth  1512  on the cannula  1502 . When the first and second sets of teeth  1510 ,  1512  are engaged ( FIG. 18A ), the adjustable stop  1500  is prevented from moving along the cannula  1502 . When the teeth are disengaged ( FIG. 18B ), the position of the adjustable stop  1500  may be adjusted. To engage and disengage the teeth, the moveable body  1508  is pressed/moved such that the first set of teeth  1510  are moved out of engagement with the second set of teeth  1512 . The adjustable stop  1500  further includes a spring element  1529  configured to bias the moveable body  1508  towards the engaged position (i.e., the position in which the first and second sets of teeth  1510 ,  1512  are engaged). 
     In some embodiments, the adjustable stop  1500  further includes a table mount  1530  configured to mount the adjustable stop  1500  to a table. In some embodiments, the table mount  1530  extends outwardly from one side of the adjustable stop  1500  and may include one or more openings  1532  configured to receive fixation elements (not shown) to fix the position of the adjustable stop  1500  (and anything coupled to it) with respect to the table. 
     When performing an extraforaminal disc prep, surgeons need to navigate an initial trajectory through Kambin&#39;s triangle. This can be performing using any suitable instrument (e.g., a spinal needle, a JamShidi®, a k-wire, etc.). Kambin&#39;s triangle has one leg defined by the exiting nerve root of the surgical level. If care is not taken during the initial stab, damage to this nerve can occur. The inventor has developed a k-wire that can address this need. 
       FIG. 19  depicts a k-wire  1900  in accordance with embodiments of the present disclosure. At least a portion of the k-wire  1900  has a coating  1901  formed of a polymer such as Halar®. In some embodiments, about 2-3 mm of a first end  1902  of the k-wire  1900  is exposed and about 20-30 mm of a second end  1904  are exposed. The k-wire  1900  has a stainless steel core, which is conductive and can, therefore, be used with a neuro-monitoring system. A lead (not shown) can be attached to the second end and stimulated. The coating  1901  allows the k-wire to be insulated from the patient&#39;s anatomy surrounding the k-wire  1900 , thus focusing the stimulation around the nerve (i.e., at the first end  1902 ). As a result, an initial trajectory can be neuromonitored or stimulated in a manner in which only the area of interest (i.e., the exiting nerve root) is stimulated. 
     All references cited herein are expressly incorporated by reference in their entirety. There are many different features to the present invention and it is contemplated that these features may be used together or separately. Unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Thus, the invention should not be limited to any particular combination of features or to a particular application of the invention. Further, it should be understood that variations and modifications within the spirit and scope of the invention might occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention.