Patent Publication Number: US-2023135764-A1

Title: Multi-shield spinal access system

Description:
CONTINUING DATA 
     This application is a continuation-in-part of U.S. application Ser. No. 15/697,494 filed on Sep. 7, 2017, which is a continuation-in-part of U.S. application Ser. No. 15/437,792 filed on Feb. 21, 2017, which is a continuation-in-part of U.S. application Ser. No. 15/254,877 filed on Sep. 1, 2016, which claims priority to U.S. Provisional Application No. 62/214,297 filed on Sep. 4, 2015, each of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Today, microsurgical spinal bone resections and spinal decompressions which are performed under microscopic view through mini-open tubes and retractors are becoming the standard of spinal surgical care. These access tools normally have inner diameters between about 16 mm and 30 mm. Where, as here, the approach and decompression technique are familiar to spinal surgeons, and where standard equipment and instruments can be used, these known technologies should be considered as a base from which further innovation can be made. 
     However, the anatomic window of Kambin&#39;s triangle, through which safe disc access is possible, has very limited dimensions. This access window can be enlarged by resecting at least a part of the superior articular process. But either way, the length of a working shield needed to safely introduce the implant to the intervertebral space via this approach must be in the region of about 8-12 mm in diameter, reaching from the facet joint line to the disc entry point. 
     SUMMARY OF THE INVENTION 
     The present inventors envision introducing a second, inner shield through the above-mentioned first, outer shield. The second inner shield extends past the first outer shield to arrive next to nervous tissue, thereby shielding the nerves from instruments or devices passing through to the disc space. During this step, the outer shield allows the visual, safe placement of the inner shield. 
     In one embodiment, there is provided an outer shield (which can be, for example, a tube or a blade) comprising an access shield with a larger diameter (−12-30 mm) that reaches from the skin down to the bone line, with an inner shield having a second smaller diameter (−5-12 mm) extending past the access shield and reaches down to the disc level. This combines the benefits of the direct visual from microsurgical/mini open approaches and percutaneous techniques ( FIGS.  1   a - b    and  2 ). 
     The outer shield has a number of features and advantages. First, it enables separation and protection of surrounding of soft tissue and visualization during a standard microsurgical decompression/bone resection work under microscopic view—based on a standard procedure that a surgeon who is familiar with MIS techniques is able to perform. Second, it enables separation and protection of surrounding of soft tissue and visualization during detection and removal of the facet joint, or parts of the facet joint—based on a standard procedure that a surgeon who is familiar with MIS technique is able to perform. Third, it enables identification, preparation and protection of sensitive (e.g., neural) tissue (exiting nerve root, traversing nerve root, dura) under direct visual control underneath the border between retraction-sensitive and non-retraction sensitive tissues (e.g., the facet line)—based on a standard procedure that a surgeon who is familiar with MIS technique is able to perform. Fourth, it enables insertion of the inner shield and potential docking of the inner shield in the disc space or at the vertebrae under direct visual control. 
     Likewise, the inner shield has a number of features and advantages. First, it enables protection of nervous tissue (exiting nerve root, transverse nerve root, dura) against instruments that are introduced into the intervertebral disc. Second, it enables guidance of intradiscal instrumentation (discectomy instruments, visualization instruments, discectomy verification instruments, implant insertion instruments, bone graft filling instruments). Third, because of its small size, the shield can be inserted with minimal damage or trauma to bone and soft tissue in the area of the posterior column of the spine, comparable to percutaneous access instruments 
     Therefore, in accordance with the present invention, there is provided a method of accessing an intervertebral disc in a patient, comprising the steps of: 
     a) making an incision in a skin of the patient, 
     b) percutaneously inserting through the incision an outer shield having a substantially tubular shape (such as a tube or a multi-slotted retractor), the outer shield having a length adapted to extend from the incision to a border between sensitive and insensitive tissue (e.g., a superior articular process (SAP), or a lamina), in the spine of the patient, 
     c) stabilization of this outer shield to a pedicle anchor, 
     d) insertion of an outer shield integrated optical visualization instrument, resecting a 
     e) portion of the superior articular process, and/or performing a microsurgical decompression procedure 
     f) inserting or deploying an inner shield through or from the outer shield so that a distal end portion of the inner shield extends to the disc, the inner shield having an outer surface, 
     g) contacting the outer surface of the shield to a nerve root to shield the nerve root, 
     h) microsurgical decompression of any tissue deemed to be causing nerve impingement, 
     i) extraction of the intervertebral disc material including the removal of the cartilaginous material from the vertebral endplates, 
     j) insertion of the interbody device, and 
     k) deployment of a mechanism of stabilization to stabilize the intervertebral segment. 
     Also in accordance with the present invention, there is provided a method of accessing an intervertebral disc in a patient, comprising the steps of: 
     a) making an incision in a skin of the patient, 
     b) percutaneously inserting through the incision an outer shield having a substantially tubular shape, 
     c) stabilization of this outer shield to a pedicle anchor, 
     d) inserting an inner shield through the outer shield so that a distal end portion of the inner shield extends to the disc, the inner shield having an outer surface, 
     e) contacting the outer surface of the shield to a nerve root to shield the nerve root 
     f) microsurgical decompression of any tissue deemed to be causing nerve impingement, 
     g) extraction of the intervertebral disc material including the removal of the cartilaginous material from the vertebral endplates, 
     h) insertion of the interbody device, and 
     i) deployment of a mechanism of stabilization to stabilize the intervertebral segment 
     Also in accordance with the present invention, there is provided an access device for accessing an intervertebral disc, comprising: 
     a) an outer shield having a substantially tubular portion, a length adapted to extend from an incision to a border between sensitive and insensitive tissue (e.g., an articular process or a lamina), a proximal end portion, a distal end portion, an outer surface, and a longitudinal throughbore defining an inner surface, 
     b) an inner shield having i) a first substantially tubular portion having a proximal end portion, a distal end portion, a longitudinal through-bore defining an inner surface, and an outer surface defining a diameter, and ii) a longitudinal flange extending distally from the distal end portion of the substantially tubular portion, 
     wherein the outer surface of the inner shield substantially nests within the inner surface of the outer shield so that 
     i) the flange extends distally past the distal end portion of the outer shield. 
     In one aspect, a multi-tool is provided that includes a shaft component having an elongate body that defines a central longitudinal axis extending from a proximal handle to a distal tip. The multi-tool can further include a body having an opening for receiving the shaft component therethrough and one or more coupling features configured to receive one or more surgical devices therein such that the surgical devices interface with the shaft component while disposed within the body. There can also be an actuation feature formed on the body that is configured to engage the shaft component to toggle the shaft component between an unlocked configuration and a locked configuration relative to the body. 
     The multi-tool described above can have a variety of modifications and/or additional features that are within the scope of the present disclosure. For example, in some embodiments, the surgical devices of the multi-tool can be any of a nerve-mapping tool and a navigation array. In some embodiments, the shaft component can form an electrical connection at the interface with the surgical devices. This electrical connection can be formed by a bias element disposed between the shaft component and the surgical devices. In some embodiments, the shaft component can include a proximal handle having a conductor thereon for forming the electrical connection. 
     In some embodiments, the body can be configured to removably detach from any of the shaft component and the surgical devices. For example, the actuation feature can further include a button that is configured to be depressed by a user to detach the body from the shaft component. The body can include a slider that slides in a proximal-distal direction relative to the body to lock an axial position of the shaft component to the body. A longitudinal position of the shaft component can be stationary in the locked configuration. In some embodiments, one or more of the coupling features can include a modular attachment arm for coupling the surgical devices thereto. The modular attachment arm can include a pin received through the axis thereof, the one or more devices being configured to receive the pin therein for snapping the modular attachment arm to the modular attachment arm. The modular attachment arm, in some embodiments, can be keyed such that the surgical devices are prevented from coupling to the modular attachment arm in all but one orientation. 
     In another aspect, a surgical device is provided that includes a shaft component configured to be inserted into a target site within a patient, the shaft component having an elongate body that defines a central longitudinal axis extending from a proximal handle to a distal tip. The surgical device can further include a locking handle configured to engage the shaft component with the locking handle including a base clamp having an opening for receiving the proximal handle of the shaft component therethrough and one or more ports configured to receive one or more surgical devices therein; and a top clamp extending proximally from the base clamp. The base clamp and the top clamp of the surgical device can also be configured to rotate relative to one another to move the multi-tool between an open position in which the shaft component can translate or rotate relative to the locking handle and a closed position in which the shaft component is prevented from translating or rotating relative to the locking handle. 
     The surgical device described above can have a variety of modifications and/or additional features that are within the scope of the present disclosure. For example, in some embodiments, the locking handle can include a core therein for coupling to the shaft component and the one or more surgical devices. Further, in some embodiments, the shaft component can interface with the surgical devices disposed through the core to establish an electrical connection therebetween. Still further, in some embodiments, the core can be made of an overmolded material. 
     In some embodiments, the shaft component can include a locking groove configured to receive a retention feature of the locking handle therein for securing the shaft component to the locking handle. Further, in some embodiments, the shaft component can include a stopper configured to abut any of the top clamp and the base clamp to prevent proximal advancement of the shaft component relative to the locking handle. 
     In certain embodiments, the top clamp is disposed substantially perpendicular to the base clamp in the open position and the top clamp is aligned with the base clamp in the closed position. The top clamp can include an opening configured to receive the shaft component therethrough. Further, in some embodiments, the top clamp can be received in an indentation formed in the base clamp. Still further, in some embodiments the top clamp can further include a mating tab configured to engage abutment surfaces on the base clamp to couple the top clamp to the base clamp. 
     In another aspect, a surgical method is provided that includes making an incision in a target site of a patient. The method can include inserting a shaft component into the target site to dock the shaft component therein, the shaft component being coupled to a body with an opening for receiving the shaft component therethrough and one or more coupling features configured to receive one or more surgical devices therein such that the surgical devices are configured to interface with the shaft component while disposed within the body, wherein the surgical devices guide the shaft component into the target site; and advancing an access port over the shaft component into the target location. 
     In some embodiments, the method includes surgical devices that are any of a nerve-mapping tool and a navigation array. Further, the navigation array can be calibrated prior to inserting the shaft component into the target site. Still further, in some embodiments the method includes inserting a screw into the target location under guidance of the navigation array. 
     In some embodiments, the shaft component can be inserted under finger pressure. In other embodiments, the shaft component can be inserted under manual force. In some embodiments, the method includes sweeping the distal tip of the shaft component across the target site to dock the shaft component within the target site. 
     In certain embodiments, the method can further include removing the body from the shaft component. The method can further include depressing a button formed on the body to release the shaft component from the body. In some embodiments, the method can include advancing one or more dilators over the shaft component into the target site to increase a size of the target site. Further, the method can include removing one or more dilators from the target site. 
     In certain embodiments, the method can include advancing one or more tools through the access port into the target site. The one or more tools can include a plug that is received in the access port to extend proximally from the access port. Still further, in some embodiments, the method can include adjusting an orientation of the plug in multiple directions of freedom to manipulate a position of the access port within the target site. In other embodiments, the method can include inserting a second shaft component through the plug to adjust the orientation of the plug. 
     In certain embodiments, the method can include visualizing the trajectory of the shaft component within the target site. Visualizing the trajectory can further include advancing a camera through one or more channels of the access port into the target site. The method further include the camera and the shaft component being advanced through separate channels in the access port. 
    
    
     
       DESCRIPTION OF THE FIGURES 
         FIG.  1   a    shows an interbody device delivered through the access device. 
         FIG.  1 B  shows an end view of the access device. 
         FIGS.  2   a  and  2   b    are different views of a tube-in-tube embodiment of the access device. 
         FIGS.  3   a - 3   d    show different axial cross section of the inner shield. 
         FIG.  4    shows a necked, funnel-shaped embodiment of the inner shield. 
         FIGS.  5 - 6    show different longitudinal cross sections of concentric and nonconcentric inner shields. 
         FIG.  7    shows a jointed access device. 
         FIG.  8   a    shows a flanged embodiment of the inner shield. 
         FIG.  8   b    shows an inner shield with a proximal stop. 
         FIG.  9    shows an access device with two ports attached to the outer shield. One port is a connector to hold the outer tube, while the other is an interface for a light source. 
         FIG.  10    discloses a cross-section of an outer tube wherein the outer tube wall has a first channel adapted for containing a visualization unit (such as a camera) and a second channel adapted for containing a cleaning system (such as a lens cleaning device). 
         FIG.  11    discloses a cross-section of an outer tube wherein the outer tube wall contains a lens cleaning device and a camera. 
         FIG.  12    discloses a chip-on-tip embodiment including a cross-section of an outer tube wherein the outer tube wall has a channel containing an endoscope having a video chip near its distal end. 
         FIG.  13    discloses a distal end of an outer tube featuring a video chip near its distal end. 
         FIG.  14    discloses a scope holder for an endoscope. 
         FIGS.  15     a - b  show inner shield having proximal elbows. 
         FIG.  16    shows an access device with a distal sharpened tip on the inner shield within an outer shield. 
         FIG.  17    shows an access device with a positioning ring between the inner and outer shields. 
         FIG.  18    shows an access device with a depth adjustment means formed by the inner and outer shields. 
         FIG.  19    discloses an integrated retractor having a flat inner face housed within a cutout of an outer tube  245 . 
         FIG.  20    discloses a retractor having a flat inner face housed within an outer tube. 
         FIG.  21    discloses an outer tube having a retractor nesting with the outer face of the outer tube. 
         FIGS.  22 - 24     b  show a distraction embodiment. 
         FIGS.  25 - 30    show an access device with an extending shield. 
         FIG.  31    shows an access device with an inner and outer shield. 
         FIGS.  32 - 34    show in inner shield. 
         FIG.  35    discloses a radial soft tissue retractor. 
         FIG.  36    discloses an outer tube/inner retractor assembly wherein the first inner retractor and second inner retractor both tilt inwards to retract soft tissue. 
         FIGS.  37 - 46    disclose a preferred method of surgery involving the access device. 
         FIGS.  47   a - c    disclose a Navigation plug comprising a base having an array attached thereto, wherein the plug is adapted to fit within an outer tube. 
         FIG.  48    discloses the cookie cutter-type distal end of an ultrasonic cutter extending from the end of an outer tube, wherein the distal end has a plurality of cutting teeth. 
         FIGS.  49     a - b  disclose various cross-sections of the template for guiding a bone cutting device. 
         FIG.  50    discloses a cookie cutter-type distal end of an ultrasonic cutter having a semicircular cutting piece cutter bone. 
         FIG.  51    discloses a mini flex arm connecting an outer tube and a screw extension. 
         FIG.  52    discloses an outer tube/inner retractor assembly wherein the inner retractor is tilted inwards to retractor soft tissue. 
         FIG.  53    discloses an outer tube/inner retractor assembly wherein the inner retractor runs parallel with the outer tube. 
         FIG.  54    discloses an endoscope housed within an outer tube, and an inner tube extending from the outer tube. 
         FIGS.  55 - 63    disclose some of the instruments used in preferred procedures disclosed herein. 
         FIGS.  64 - 90    disclose some of the instruments in their contemplated in-spine use orientations in preferred procedures disclosed herein. 
         FIG.  91    is a perspective view of an embodiment of a multi-tool; 
         FIG.  92    is perspective view of a shaft component that is used with the multi-tool of  FIG.  91   ; 
         FIG.  93    is a schematic view of a distal end of the shaft component of  FIG.  92   ; 
         FIG.  94 A  is a cross-sectional view of the multi-tool of  FIG.  91   ; 
         FIG.  94 B  is another cross-sectional view of the multi-tool of  FIG.  91   ; 
         FIG.  94 C  is another cross-sectional view of the multi-tool of  FIG.  91   ; 
         FIG.  95    is a perspective view of another embodiment of a multi-tool; 
         FIG.  96    is a cross-sectional view of the multi-tool of  FIG.  95   ; 
         FIG.  97    is another cross-sectional view of the multi-tool of  FIG.  91    being coupled to a navigation array; 
         FIG.  98    is a perspective view of another embodiment of a multi-tool; 
         FIG.  99    is a perspective view of a cap of the multi-tool of  FIG.  98   ; 
         FIG.  100    is a perspective of the multi-tool of  FIG.  98    being coupled to a navigation array; 
         FIG.  101    is a cross-sectional view of the cap of the multi-tool of  FIG.  98   ; 
         FIG.  102    is a perspective view of another embodiment of a multi-tool; 
         FIG.  103    is a perspective view of another embodiment of a multi-tool; 
         FIG.  104    is perspective view of a shaft component that is used with the multi-tool of  FIG.  103   ; 
         FIG.  105    is a perspective view of a proximal handle of the shaft component of  FIG.  104   ; 
         FIG.  106 A  is a top view of a cap of the multi-tool of  FIG.  103    in an open position; 
         FIG.  106 B  is a top view of a cap of the multi-tool of  FIG.  103    in a closed position; 
         FIG.  107    is a perspective view of another embodiment of a multi-tool; 
         FIG.  108    is an exploded perspective view of the multi-tool of  FIG.  107   ; 
         FIG.  109    is an exploded perspective view of a cap of the multi-tool of  FIG.  107   ; 
         FIG.  110 A  is a perspective view of a knob of the multi-tool of  FIG.  107   ; 
         FIG.  110 B  is a cross-sectional view of the knob of  FIG.  110 A ; 
         FIG.  111 A  is a top view of a cap of the multi-tool of  FIG.  107    in an open position; 
         FIG.  111 B  is a top view of a cap of the multi-tool of  FIG.  107    in a closed position; 
         FIG.  112    is a perspective view of another embodiment of a multi-tool; 
         FIG.  113 A  is a perspective front view of a clamp of the multi-tool of  FIG.  112   ; 
         FIG.  113 B  is another perspective view of the clamp of  FIG.  113 A ; 
         FIG.  114    is a cross-sectional view of the multi-tool of  FIG.  112   ; 
         FIG.  115    is a perspective cross-sectional view of the multi-tool of  FIG.  112   ; 
         FIG.  116 A  is a perspective view of another embodiment of a multi-tool; 
         FIG.  116 B  is a perspective view of the multi-tool of  FIG.  116 A ; 
         FIG.  117    is a schematic view of inserting a shaft component into a target site of a patient; 
         FIG.  118    is a perspective view of the shaft component of  FIG.  117    having a series of dilators disposed thereon; 
         FIG.  119    is a perspective view of an access port inserted over the dilators in  FIG.  118   ; 
         FIG.  120    is a perspective view of a port adjuster configured to be received in the access port of  FIG.  119   ; 
         FIG.  121    is a perspective view of an assembly of the port adjuster of  FIG.  120    coupled to the access port of  FIG.  119   ; 
         FIG.  122    is a schematic view of the assembly of  FIG.  121   ; 
         FIG.  123    is a perspective view of a shaft component disposed in the assembly of  FIG.  121   ; 
         FIG.  124    is another perspective view of the shaft component disposed in the assembly of  FIG.  121   ; and 
         FIG.  125    is a cross-sectional view of the of the shaft component disposed in the assembly of  FIG.  121   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Fluoroscopic visualization is performed to define the incision site of the initial reference array placement, as well as the incision for access to the intervertebral disc. 
     Generally, the shields of the present invention can be applied to any of the conventional approaches commonly used in spine surgery. However, given the clinical benefit of the access device and its underlying rationale, it is preferably suitable to use these shields in either interlaminar, extraforaminal or transforaminal approaches to the intervertebral disc. 
     Now referring to  FIGS.  1 - 7   , there is provided an access device for accessing an intervertebral disc, comprising: 
     a) an outer shield  1  having a substantially tubular portion, a length adapted to extend from an incision to a border between sensitive and insensitive tissue (e.g., an articular process), a proximal end portion  3 , a distal end portion  5 , an outer surface  7 , and a longitudinal through-bore  9  defining an inner surface  10 , 
     b) an inner shield  11  having i) a first substantially tubular portion  13  having a proximal end portion  15 , a distal end portion  17 , a longitudinal through-bore  19  defining an inner surface  21 , and an outer surface  23  defining a diameter, and ii) a longitudinal flange  25  extending distally from the distal end portion of the substantially tubular portion, 
     wherein the outer surface of the inner shield substantially nests within the inner surface of the outer shield so that the flange extends distally past the distal end portion of the outer shield, and 
     the distal end portion of the substantially tubular portion of the inner shield extends distally past the distal end of the outer shield. 
     Outer Shield Embodiments: 
     In the design of the outer shield, traditional tube or split tube I retractor concepts can be used. Newer concepts such as a “flexible tube” could also be adopted. The outer shield can be a simple cylindrical tube. It may also be a split tube, in the manner that conventional retractors are considered to be split tubes. It can be a flexible tube. It can be a tube with a slot running from the proximal end to the distal end. Various shape embodiments could be: 
     a) a cylindrical tube with an inner diameter D ( FIG.  3   a   ); 
     b) an oval tube with a height a different than a length b ( FIG.  3   b   ); 
     c) a “half moon” tube having a substantially circular or oval cross section of diameter D, with a section cut (or chord) “a” ( FIG.  3   c   ); and 
     d) a rectangular tube with height a and width b ( FIG.  3   d   ). 
     In some embodiments, the shape of the distal end portion  5  includes an unsymmetrical shape for better tissue retraction lateral to the SAP. 
     The outer shield can be preferably used with a variety of access window sizes (i.e., widths) ranging from 6 mm to 25 mm and lengths ranging from 40 mm to 200 mm. Typically, the outer shield comprises a feature that allows for the attachment of a stabilization mechanism that allows for appropriate flexibility in attachment (e.g. a ball joint). In one embodiment, the outer shield has a customized feature adapted for the introduction of an endoscope or camera that allows the endoscope to be introduced to a predetermined depth where the working window at the distal portion of the outer shield can be visualized. 
     Inner Shield Embodiments: 
     Now referring to  FIGS.  3   a - d   , the inner shield  11  may encompass various designs as well. 
     In a first embodiment, the inner shield is a fully surrounding (i.e., extending for 360 degrees) stiff tube. It may possess various cross-sections, such as: 
     e) a cylindrical tube with an inner diameter D ( FIG.  3   a   ); 
     f) an oval tube with a height a different than a length b ( FIG.  3   b   ); 
     g) a “half moon” tube having a circular cross section of diameter D, with a section cut (or chord) “a” ( FIG.  3   c   ); and 
     h) a rectangular tube with height a and width b ( FIG.  3   d   ). 
     The inner shield may possess different longitudinal shapes. For example, in a second embodiment, and now referring to  FIGS.  4 - 7   , the inner shield  11  is a funnel-shaped (e.g. necked) tube (as in  FIG.  4   ). In this embodiment, it changes its cross sectional shape/area along the shield, with a bigger diameter/working zone at the proximal portion, and the length of this zone with a bigger diameter is adjusted to be the part of the inner shield that will be nested within the outer shield, and a smaller diameter I working zone where the inner shield is extending the outer shield. 
     This design increases the range of motion of intradiscal tools and enables better visualization. 
     In  FIG.  4   , the flange is a second substantially tubular portion  25  having a diameter less than the diameter of the first substantially tubular portion  13  of the inner shield. A necked region  27  is disposed between the first and second substantially tubular portions. 
     In some embodiments, the inner shield may be in the form of one of a plurality of retractor blades. 
     In tubular embodiments, the smaller tube can be a concentric with the larger tube, or not concentric therewith. In  FIG.  5   , the first and second substantially tubular portions of the inner shield are concentric (a=b). In  FIG.  6   , the first and second substantially tubular portions of the inner shield are not concentric (a&gt;b). 
     In some embodiments, there is provided a spherical joint between the larger and the smaller tubes, allowing the angle to change between the two tubes ( FIG.  7   ). In  FIG.  7   , the outer surface  23  of the inner shield substantially nests within the inner surface  10  of the outer shield so that the proximal end of the substantially tubular portion of the inner shield terminates within the outer shield. Also, the distal end portion of the inner shield narrows distally to define a first radius R  1 , and the proximal end portion of the inner shield narrows distally to define a second radius, and the proximal end portion of the inner shield nests within the distal end portion of the outer shield to allow polyaxial pivoting of the inner shield. 
     In some embodiments, the inner shield is a partially surrounding tube/shield, or “flange”, designed only to protect the nerves. For some applications, the only purpose of the inner tube might be to shield/protect the exiting nerve root. In this case, the inner shield might be simplified to a cylinder with a flange  25  extending distally therefrom, so that the flange is only a shield of about a quarter of a full circle. See  FIG.  8   a   , or  FIG.  9    if mounted on the outer shield). 
     Depth Adjustment of Nerve Protector 
     The aforementioned outer shield can be positioned and fixed in its depth through a mechanism which relies on interference between the outer shield and the inner shield at any location along either the outer shield or inner shield. 
     In  FIG.  8   b   , the proximal end portion of the first substantially tubular portion  13  of the inner shield comprises a stop  31  adapted to abut the proximal end portion of the outer shield, the stop being adapted to prevent excessive distal movement of the inner shield. Preferably, the stop extends substantially radially about the proximal end portion of the substantially tubular portion of the inner shield. The stop may also further comprise a textured radial surface  33  adapted for gripping. It acts as both a stop and as a handle to twist the shield. 
     In  FIG.  9   , the outer surface of the inner shield substantially nests within the inner surface of the outer shield so that the proximal end portion of the substantially tubular portion of the inner shield extends proximally past the proximal end of the outer shield. Also in  FIG.  9   , the outer surface of the outer shield further comprises a first port  41  adapted for connecting to a navigation instrument or a stabilization point, and a second port  43  adapted for connecting to a camera/light system. 
     Navigation of Outer Shield: 
     The first port allows the outer shield to be navigated to determine its position (depth and orientation) in relation to the treatment site. In one embodiment, the outer surface of the outer shield has a feature that allows for the direct or indirect attachment of a navigation instrument. In another embodiment, the inner surface of the outer shield has a feature that allows for the direct or indirect attachment of a navigation instrument. 
     Endoscope in the Outer Shield: 
     In some embodiments, the outer shield has an integrated endoscope that can be set in a fixed or variable (angle or circumferential) position relative to the anatomy. This endoscopic visualization can be utilized in subsequent surgical steps, including bone removal, inner shield deployment, discectomy and implant insertion. Preferably, the endoscope has an integrated lens cleaning mechanism for automated lens cleaning in situ. 
       FIG.  10    discloses a cross-section of an outer tube wherein the outer tube wall  138  has a first channel  238  adapted for containing a camera and a second channel  338  adapted for containing a lens cleaning device. 
       FIG.  11    discloses a cross-section of an outer tube wherein the outer tube wall contains a lens cleaning device  139  and a camera  239 . 
       FIG.  12    discloses a chip-on-tip embodiment including a cross-section of an outer tube wherein the outer tube wall has a channel  140  containing an endoscope  240  having a video chip  340  near its distal end. 
       FIG.  13    discloses a distal end of an outer tube featuring a video chip  141  near its distal end. 
     Fixed Endoscope: 
     The endoscope can be a chip-on-tip type of endoscope having an outer diameter less than 5 mm and having an incremental length substantially matching the length of the outer shield. The benefits of an integrated chip-on-tip endoscope/outer shield embodiment include the relatively free space within the bore of the outer shield, thereby enhancing visualization. 
     Preferably, the endoscope is angled within the port or has a built-in lens angle such that, at final positioning within the port, the circumference of the distal portion of the outer shield is visible and the area within the circumference is visible as well. 
     In some embodiments, the endoscope can be removed from the wall of the outer shield and inserted independently into the outer shield bore to inspect the treatment site (e.g. into the disc space for confirmation of adequate discectomy). 
       FIG.  14    discloses a scope holder  137  for an endoscope  237 . 
     Still referring to  FIG.  9   , in some embodiments, the flange  25  of the inner shield has an arcuate transverse cross-section. In some embodiments, the arcuate transverse cross-section of the flange defines an outer surface  47  of the flange having a curvature substantially similar to a curvature of the inner surface  10  of the outer shield. Preferably, the flange defines a second substantially tubular portion having a diameter less than or equal to the diameter of the first substantially tubular portion of the inner shield. 
     Now referring to  FIGS.  15   a - b    and  16 , the inner shield can be a single blade that can be mounted I hooked to the outer tube. In this case, elbow  51  functions as a stop and also as a connector to the outer tube. Also, the proximal end of the inner shield may form an anchoring spike  53 . 
     There are a number of ways to fix or locate the inner shield onto the disc and/or onto the outer shield. In one embodiment, which provides safety of the inner shield against slippage/dislocation, involves mounting it distally (onto or within the vertebral endplates or disc annulus) and/or proximally (onto the outer shield). 
     Distal fixation of the inner shield with the anatomy may include: a) fixation within disc annulus, b) fixation against vertebrae; c) fixation against other structures; d) K-Wires that are distally extending through the walls of the inner shield and anchored to the anatomy; and e) spikes extending the distal part ( FIG.  15   ) to be anchored to the anatomy. 
     Proximal fixation of inner shield upon the outer shield may involve a positioning ring or a depth adjustment. Now referring to  FIG.  17   , proximal fixation of inner shield upon the outer shield may involve a positioning ring  55 . Assuming the outer shield would be fixed relative to the anatomy, there would be the option of having positioning rings having the shape of the outer tube at the outside, and of the inner tube on the inside. When placed over the inner shield and into the outer shield, such a ring would stabilize the location or at least the orientation of the proximal inner shield against the outer shield, and—by considering the assumption above—also against the anatomy. 
     Now referring to  FIG.  18   , proximal fixation of inner shield upon the outer shield may involve a depth adjustment means  57 . This would additionally stabilize or anchor the tip location of inner shield against the anatomy—via anchoring or hooking the inner shield into the outer shield via ratchet system. The ratchet system can also be located between the inner surface of the outer shield, and the outer surface of the inner shield or within the wall of the outer shield. It may further include a spring system to increase friction between the inner and outer shields. 
     Inner Shield Deployment (Circumferential): 
     Embodiments having separate outer and inner shields allow for the independent positioning of the inner shield relative to the outer shield. Also, the use of a smaller inner shield (relative to the outer shield) allows for maximum visualization at the entrance where no retraction-sensitive tissues reside. This maximum visualization allows for accurate placement of the inner shield. Where retraction-sensitive tissues reside distal the outer shield, a relatively smaller inner shield allows for minimum retraction while providing an access through or past these tissues. Preferably, the inner diameter of the inner shield is no more than 40-100% of the inner diameter of the outer shield. 
     In some embodiments, the inner shield-outer shield configuration is replaced by a) a primary shield having a substantially tubular shape having a cutout, and b) a secondary shield having a shape that is substantially insertable into the cutout. Preferably, the primary shield has a substantially annular shape and the secondary shield has an arcuate cross-section that substantially matches the annular shape of the primary shield. This embodiment allows the secondary shield to be tilted with respect to the primary shield. 
     Inner Shield Deployment (Radial): 
     In another nerve protection embodiment, the motion of retraction of the shields is radial rather than rotational. In these embodiments, a straight or bayonetted inner shield may be used. The inner shield may be positioned over the area in which the protected tissue is to be located. The flange shield can then be angled into the center of the access window at the distal end of the outer shield e.g. towards the caudal pedicle. It can then be subsequently advanced longitudinally onto the medial side of the nerve root, into the “safe zone” as described by Kambin. It is subsequently angled such that the distal tip of the inner shield is angled laterally, wherein its outer distal surface gently pushes the exiting nerve root away and I or shields it against the tools that are further introduced medially to the shield for intradiscal work. This embodiment may be constructed such that the inner shield substantially nests either a) within wall of the outer shield ( FIG.  19 ( a ) ), b) inside the inner surface of the outer shield ( FIG.  20 ( b ) ) or c) outside the outer surface of the outer shield (( FIG.  21 ( c ) ). In some embodiments, the inner shield is built into the wall of the outer shield or even outside the outer shield. 
       FIG.  19    discloses an integrated retractor having a flat inner face  145  housed within a cutout of an outer tube  245 . 
       FIG.  20    discloses a retractor having a flat inner face  144  housed within an outer tube. 
       FIG.  21    discloses an outer tube  150  having a retractor  250  nesting with the outer face  350  of the outer tube. 
     Depth Control of Nerve Protector: 
     The aforementioned outer shield can be controlled in its depth through a mechanism that relies on interference between the outer shield and the inner shield at any location along either the outer shield or inner shield. 
     There are a number of avenues by which the present device can be used to distract the disc space and/or provide nerve protection upon mounting. 
     In one distraction embodiment, a revolution spreader is used. This is a conventional concept involves an ovoid or rectangular cross-sectional shaped rod that is inserted into the disc with its smaller dimension directed towards the vertebral endplates. After turning the spreader by 90° under force, the larger dimension is directed towards the vertebral endplates, which distracts the disc by the difference of the two cross sectional dimensions. 
     In a second distraction embodiment, as now referring to  FIGS.  22 - 24     b , the inner shield may comprise a spreader, which includes a frame  60 , a cranial blade  61  and a caudal blade  63 . 
     The spreader with respective cranial  61  and caudal  63  distraction blades in cranial and caudal locations is introduced into the disc in a collapsed/tapered configuration ( FIG.  22   ). The spreader blades are then distracted with an inner core  65  (the core matching a counter geometry on the blade to not slip away sideways), elevating the intervertebral height from d 1  to d 2  ( FIG.  2223   ). The side walls  67  matching to the inner core height are then introduced medially/laterally ( FIG.  24   a   ), to circumferentially close the four-wall shield. Once the inner core is removed, the stacked shield keeps the vertebral bodies separated in distracted condition ( FIG.  24   b   ). 
     Now referring to  FIGS.  25 - 26   , the inner shield may further comprise a rotating flange  71  that moves laterally/medially upon rotation to shield the nerve root. 
     In a nerve protection embodiment, and now referring to  FIGS.  27 - 30   , a rotation funnel  70  is used. Preferably, the flange shield  71  can be smartly introduced to protect the exiting nerve root while being inserted. This shield can be directed towards the caudal pedicle if introduced through the outer shield. This location is a “safe zone”. Once the distal tip reaches the disc level, the inner shield can be turned clockwise by about 90° (i.e., rotated), so that the flange gently pushes the exiting nerve root away, and I or shields it against the tools that are further introduced medially to the shield, for intradiscal work. 
     In a second nerve protection embodiment, and now referring to  FIGS.  31 - 34   , a concentrically-arrayed multi-shield is used to gently move and/or shield nerves. The rotation funnel principle can also be applied for more than one rotating shield. A single shield may be suitable if the protection only has to be provided against a structure that lies on one single side. In other situations, however, the shield entry towards the disc would be bounded both medially and laterally by the traversing and the exiting nerves, so the inner shield needs to shield against two opposing structures. In this case, the two concentrically-arranged outer  81  and inner  83  rotating flanges are turned by 90° in respective clockwise and counterclockwise directions to reach an end configuration wherein the opposed shields protect the nerves from the tools that are further introduced for intradiscal work. 
     In another nerve protection embodiment, a radially-retracting multi-shield is used to gently move and/or shield nerves. The radially-retracting principle can also be applied to more than one radially retracting shield. 
       FIG.  35    discloses a radial soft tissue retractor  136 . 
       FIG.  36    discloses an outer tube/inner retractor assembly wherein the first inner retractor  153  and second inner retractor  253  both tilt inwards to retract soft tissue. 
     A single shield may be suitable if the protection only has to be provided against a structure that lies on one single side. In other situations, however, the shield entry into the disc would be bounded both medially and laterally by the traversing and the exiting nerves, so that the inner shield needs to shield against two opposing structures. In this case, the two opposing inner flanges are initially positioned towards the center of the outer tube access window and subsequently retracted outwards to shield the opposing nerves from the tools that are further introduced for intradiscal work. 
       FIGS.  37 - 46    disclose a preferred method of surgery involving the tube-in-tube access device. 
     In one embodiment, and now referring to  FIG.  37   , the surgeon places a pedicle screw-based anchor, adds a navigation reference frame  101  to the anchor, and uses a commercial navigation system for navigation. In some embodiments, a navigation array is placed onto the anatomy with reference to an anatomical feature that is symmetrically substantially adjacent the treatment site (e.g. contralateral cranial or caudal pedicle). 
     In some embodiments, there is navigation of the probe to a facet capsule or disc space through Kambin&#39;s triangle. Preferably, subsequent to fascia and muscle dissection, a probe enabled with navigation visualization is introduced to achieve an initial anchoring point. In one embodiment, the probe is inserted into the disc space by being indexed off the lateral border of the superior articulating process and may be optionally enabled with I supported by a nerve detection and I or visualization function. In another embodiment, the probe is introduced into the facet capsule. 
     In some embodiments, there is dilation over a navigated probe. Subsequent to the initial anchoring point, dilation is performed to prepare the surgical site for the size of port required to perform the treatment. Sequential dilation up to the preferred size port window is then performed. The port is then introduced over the associated dilator. In one embodiment, the initial anchoring is in the disc space and concentric sequential dilation device(s) would be used in order to retract tissue concentrically around the initial anchoring point (exposing the lateral portion of the SAP on the lateral aspect and Kambin&#39;s triangle on the medial aspect). In another embodiment, the initial anchoring is in the facet capsule and eccentric sequential dilation device(s) could be used to focus tissue retraction laterally over the lateral portion of the SAP and Kambin&#39;s triangle. 
     In some embodiments, the outer shield is stabilized onto an anatomical reference. The outer sleeve has a substantially tubular portion having a point or feature designed for attachment to a stabilization mechanism, which in turn is fixed to an anatomical feature on the vertebral body either cranial or caudal to the treatment site. 
       FIG.  38    discloses an outer tube into which a plug containing a template for guiding a bone cutting device. 
     In some embodiments, the outer sleeve is attached to a stabilization mechanism. In one embodiment, this stabilization device would be a device of sufficient length to reach an anatomical fixation point (e.g. pedicle screw) on the contralateral side of the treatment site. The mechanism (including its connection feature connecting to both the outer shield and the anatomical anchor) allows for sufficient flexibility of placement of the outer shield and sufficient stabilization to hold the outer shield in place until it is released by the user. The method of stabilization would be such that the user can dictate the degree of stiffness. 
     In another embodiment, this device has sufficient length to reach an anatomical fixation point (e.g. pedicle screw) on the ipsilateral side of the treatment site. Likewise, the mechanism (including its connection feature to both outer shield and anatomical anchor) would allow for sufficient flexibility of placement of the outer shield and sufficient stabilization to hold the outer shield in place until released by the user. The method of stabilization would be such that the user can dictate the degree of stiffness. 
     In another embodiment, this device would be a device of sufficient length to reach an anatomical fixation point (e.g. pedicle screw) on midline of the patient. Likewise, the mechanism (including its connection feature to both outer shield and anatomical anchor) would allow for sufficient flexibility of placement of the outer shield and sufficient stabilization to hold the outer shield in place unless released by the user. The method of stabilization would be such that the user can dictate the degree of stiffness. 
     Now referring to  FIGS.  39   a - b   , the surgeon then dilates the tissue superior to the pedicle-based anchor, and inserts an outer shield  1 , connected to the anchor, with its proximal end directed to the superior articular process. Blunt dissection up to the bone is carried out over the affected intervertebral disc, and muscle retraction over the affected intervertebral disc is then carried out. This retraction involves blunt dissection of the muscle and fascia to bone level under direct visualization. 
     Now referring to  FIG.  40   , the surgeon then turns the outer shield  1  to the interlaminar space, preforms a central, bilateral decompression as required by the pathology, and then turns the shield back to its original position. 
     In some embodiments, an alternative to angling the access channel medially from the incision site could be the use of an alternative access site that would be more medial. In some embodiments, the initial anchoring point in the disc space will be medial to the inferior articulating process. For the embodiment having an initial anchoring point in the facet capsule, the dilation of the eccentric dilators will be medial from the capsule. Also, portions of the lamina and the inferior articulating process will be removed through the bone removal segment. 
     Now referring to  FIG.  41   , the surgeon then inserts a bone removal tool (not shown) into the outer shield tube and resects the lateral portion of the superior articular process to medially extend the traditional Kambin&#39;s triangle. 
     Under either direct or endoscopic visualization, a bone removal device is introduced to the outer shield and utilized to remove at least the lateral portion of the SAP. Such a device is available in lengths and sizes allowing for its safe introduction and use through an access window from 40 mm to 200 mm and a window size from 10-25 mm. 
     In one embodiment, this bone removal device is an ultrasonic cutting device. In another embodiment, this bone removal device is a reciprocating cutting surface. In yet another embodiment, this bone removal device is a revolving cutting tool. In another embodiment, this bone removal device is a mechanical punch with a stroke length between 10-30 mm. Removal of the bone can be performed in such a manner that sizes smaller than the access size will be excised and removed. The bone removal can be performed with the use of a template independently inserted into the outer shield and used to guide the direction of bone cutting and removal. 
     A Negative Template is a plug-like device that is inserted in the outer Access Tube. It contains a longitudinal cut-out in different shapes, depending on the cross-sectional shape of the tissue that needs to be removed respective of the cross-sectional shape of the tissue that needs to be covered and therefore protected from any surgical interactions. By inserting a cutting device like e.g. a Milling Bit into the longitudinal cut-out the surgeon is able to remove the tissue without the risk of endangering the covered tissue/structures. In combination with a proximal stop-system (on proximal end of outer Access Tube and/or shaft of milling system) the surgeon can remove the tissue layer by layer. The layer thickness and therefore the progression of the cutting procedure can be controlled via the stop system supported by a scale. This system allows the surgeon to perform safe tissue removal with a controlled serial work flow: check anatomical situation adjust stop system to define cross-sectional thickness of tissue that needs to be removed insert milling system until the stop system is engaged mill/cut tissue (also blindly) in plane (2D) 
     remove milling system check anatomical situation adjust stop system. 
     A serial workflow can be considered to be safer than a parallel workflow, since the surgeon only needs to take care of one parameter at a time (here: planar position of milling bit followed by its depth followed by planar position of milling bit . . . ) whereas a parallel workflow requires the control of two or more parameters at a time (here: planar position of milling bit in parallel to its depth). 
     Navigation of SAP Removal can be carried out with the aforementioned bone removal device adapted to be navigated through its mechanical or visual connection with a navigation system. 
     Now referring to  FIGS.  42 - 43   , the surgeon then inserts the inner shield tube into the outer shield tube, which acts to extend the outer tube anteriorly from the facet line until the tip of the inner shield reaches the level of the disc. The nerve root is protected by the inner shield. 
     Now referring to  FIG.  44   , the surgeon then identifies the disc, spreads the disc with a wedged osteotome; checks the mobilization, and removes the posterior rim, osteophytes and annulus until a minimum annular window is opened. The surgeon then inserts a disc removal tool  201  into the access device, removes the disc and prepares the endplates. 
     An alternative embodiment to the prescribed disc clearing step in  FIG.  44   , would be to have the disc removal tool navigated through its mechanical or visual connection with a navigation system. 
     Now referring to  FIG.  45   , the surgeon then performs temporary disc space distraction, fills parts of the disc space with bone graft and inserts a fusion cage  203  into the remaining disc space. 
     Now referring to  FIG.  46   , the surgeon then adds posterior fixation  103 . 
     Viewing Element 
     In some embodiments, a visualization element based on the chip-on-tip technology and integrated into the wall of the port is used. This embodiment has a number of advantages over a standard rod-lens endoscope that is mounted at the tube wall:
         Manufacturing costs. The chip-on-tip technology allows a very cost efficient manufacturing, therefore can be marketed as a ‘single use’ instrument.   Rigid portion only at distal tip. Whereas a standard rod-lens endoscope system has a stiff, cylindrical shape throughout the whole tube, the chip-on-top endoscope may have a non-cylindric configuration at the proximal outer tube end. Preferably, this shape is a flat cable shape. In some novel embodiments, in relation to a standard rod-lens-endoscope, the chip-on-tip endoscope has a relatively short “stiff’ section (about 20 mm), where the proximal portion consists of a cable that can be flexible. In other embodiments, the stiff portion is shorter (producing a smaller chip-assembly) and actively articulating concepts are used to change the lens angle. Due to the cable&#39;s integration in the tube wall, the shape of the port window is maintained throughout the procedure. For example, a 5 mm chip on tip endoscope turns a 15 mm circular access window into a kidney shaped access window.   Size/weight of camera unit. A standard rod-lens endoscope has a standard eyepiece that is a universal interface with a certain size. The camera that is connected to such a system has to be built in a certain dimension to be compatible with the eyepiece. This requirement produces a relatively bulky camera attachment (approx. 3-6 cm in diameter, approx. 5-10 cm in length) having a number of drawbacks. First, this large camera construct can be a physical obstacle to work, especially if the trajectory of the working port changes or interferes with the camera. Secondly, the dimension and weight of this conventional construct becomes significant enough to produce certain undesirable forces upon the rod-lens-endoscope, especially in bending. Thirdly, the relatively fragile conventional rod-lens-endoscope has to be embedded in stabilizing structures such as metal tubes, thereby further reducing the active working window.       

     With the chip-on-tip embodiments disclosed herein having its chip cable embedded in the wall of the outer tube, the cable that exits at the proximal outer tube wall does not produce similar forces upon the working port. Also, respecting the attachment mechanisms that mount the chip-on-tip endoscope in the tube-wall, the lack of bending forces produced thereby raise the possibility of adopting relatively thin attachment options that mechanically do not need to be very stable.
         Working Environment. Conventionally, a constant fluid environment (permanent flow of saline solution) is used in spine endoscopy applications. However, in a mini-open and microsurgical environment, the fluid environment is not helpful, as the anatomical conditions are very different. Accordingly, in the preferred novel procedures described herein, the chip-on-tip endoscope works in a dry, open air environment. However, the open, dry air environment in which the chip-on-tip endoscope is used may produce an undesired condensation effect upon the lens component of the endoscope. For example, a colder lens in a humid body temperature environment may fog up. Moreover, drill debris, burr debris or smoke from monopolar scalpels or hemostatic tools can likewise affect the lens of the endoscope so as to reduce visibility. Accordingly, it may be desirable to periodically clean the lens of the chip-on-tip endoscope.       

     Nerve Deflection (Tube in Tube) 
     In minimally invasive spine surgery conducted through portals, a set of dilators is often used to prepare the site for reception of the portal. One such technology is shown in US Patent Publication US 2012-0232552 (Morgenstern). In this conventional technology (which has eccentric dilators), the outer diameter of any one of the dilators is identical to the inner diameter of the next successive (outer) dilator. This identity of diameters is necessary for fluoroscopy assisted, percutaneous muscle dilation. 
     Since some embodiments of the present application describe a procedure between the level of the facet joint and the disc, the surgical site is dissected under direct visualization. Accordingly, the diameters of successive dilators used in these novel procedures do not have to match. Relaxation of the “exact diameter” requirement in these novel procedures allows the surgeon freedom in many tube design areas. For example, it allows the use of tubes that are tapered. 
     It also allows the surgeon the freedom to use outer and inner ports that are not coaxial. It further allows the trajectories of the inner port relative to the outer port to vary in angulation within certain treatment steps. Lastly, it allows the trajectories of the inner port relative to the outer port to vary in distance within certain treatment steps. 
     Because fluoroscopy-assisted, percutaneous muscle dilation is carried out without direct visualization, it is a blind procedure whose use has limitations. These limitations include the inability to carry out surgical steps that require direct visualization out of safety considerations. One such treatment step requiring direct visualization is direct decompression of bony and ligamentous tissue that is directly adjacent to nerve structures. 
     Because some embodiments described herein allow for direct visualization of delicate anatomical structures, those embodiments further specifically allow direct decompression of bony and ligamentous tissue that is directly adjacent to nerve structures and more generally allow manipulation or removal of tissue adjacent the tubes through a very tissue-preserving “tube-in-tube” access port. 
     Morgenstern further describes a method in which a guide wire is directly introduced through the disc space to Kambin&#39;s triangle, under fluoroscopy guidance (i.e., no direct visualization). Morgenstern further describes the possibility of using electrically-based nerve monitoring probes. Moreover Morgenstern describes a method of enlarging the spinous process by subsequently rasping away bone from the SAP and the pedicle. 
     The novel procedures described herein only perform non-visualized procedures (e.g., dilation) in a safe zone above the facet line. In the anatomically more critical zone between the level of the facet joint and the disc, the novel procedures dissect the surgical site under direct visualization, thereby allowing the surgeon to spare as much of the bone as is possible and as is meaningful. 
     Navigation 
     Navigation enhances static x-ray, CT or MRI data by intra-operatively showing in real-time, where the instruments used actually are in relation to the anatomy of the patient. Therefore it increases the safety of those instruments by showing their shape, trajectory and positioning and even more importantly it supports the surgeon to keep instrument orientation during the performed manipulations. 
     Without wishing to be tied to a theory, it is believed that one reason why minimally invasive techniques are not often used is the significantly higher x-ray exposure needed to keep orientation in comparison to mini-open techniques, where the surgeon still has direct visualization and so can actually see the active site with a microscope or loupe. The x-ray exposure is an even greater for the surgeon who is exposed to the radiation on a frequent basis. This challenge is addressed by the implementation of navigation technology in the novel procedures described herein because they allow the reduction of x-ray exposure to an ideal minimal total of two x-rays for registration purposes. Once a single lateral shot and a single anterior—posterior shot have been registered, all used instruments (e.g. Jamshidi-Needle, Pointer, Dilatators, Access Tube, Osteotome, Expandable Cage itself, Disc Removal Device, . . . ) can be projected in these static fluoro-images in real time. Another positive effect is a significant savings of time. Having the navigation system in place also helps the surgeon to understand the orientation (trajectory and depth) of the endoscope and therefore to understand what he or she actually sees with the camera. This can either be achieved by navigating the camera directly or indirectly by setting the camera in a fixed position integrated into a navigated Access Tube. 
     The Jamshidi-Needle, Pointer, Dilatators, and Access Tube Instruments can all be navigated with only one Instrument, the FOX-Navigation-Multi-Tool or “multi-tool.” The multi-tool can include integrated or built-in neuromonitoring, e.g., for detecting the presence, proximity, health, or other attributes of nerve tissue. The multi-tool can include an electrode, transducer, or other energy delivery element for applying energy to tissue, e.g., to ablate or cauterize the tissue. The multi-tool can include an energy delivery element in the form of a microwave ablation element. The multi-tool can include an energy delivery element of the type used in the NEUW AVE system available from ETHICON, INC. of Cincinnati, Ohio. The energy delivery element can be built-into the multi-tool, or can be supported or guided to a target location using the multi-tool. The energy delivery element can be mounted on a shaft or needle coaxially received within or around another shaft component of the multi-tool. The multi-tool can be used to position the energy delivery element in proximity to a target location, such as an osseous bone tumor. Energy can be delivered from the energy delivery element to the tumor or other target location. 
       FIGS.  47   a - c    disclose a Navigation plug comprising a base  147  having an array  247  attached thereto, wherein the plug is adapted to fit within an outer tube  347 . 
     Bone Cutter 
     In some embodiments, the novel procedures use an Ultrasonic Bone Cutting device for SAP removal, which specifically cuts bone only and will not cut soft tissue. Embodiments based on a conventional Expandable Cage Device for interbody fusion may require an access window at least as large as 12 mm. Such a large window can only be achieved by (partly) removing the Superior Articulation Process (SAP) to extend the Kambin&#39;s Triangle. The Ultrasonic Bone Cutting Device adds significantly to the safety of this procedure since it does not cut nerves if accidently hit. If the cutting device blade is designed to be in the shape and diameter of the Inner Tube/Blade (i.e., a Cookie Cutter design) that approaches distally down to the level of the disc space, the SAP removal can be minimized (less trauma, less stress for patient, quicker recovery) and performed in a single step (faster than multiple step procedure). 
       FIG.  48    discloses the cookie cutter-type distal end  143  of an ultrasonic cutter extending from the end of an outer tube  243 , wherein the distal end  143  has a plurality of cutting teeth  343 . 
     Another option to increase the safety of bone cutting is a depth-controlled manual milling of the bone with a negative guide. The negative guide covers those areas that will not be removed (negative template). The depth control allows the milling of the bone layer by level, under serial control of the surgeon. The reference for the depth control as well as the trajectory can be the outer Access Tube (also see paragraph navigation). 
       FIGS.  49   a - b    disclose various cross-sections of the template for guiding a bone cutting device. 
     Bone Cutter 
     In some embodiments, the bone removal device is a harmonic scalpel having a cookie cutter design. The scalpel has a crescent-shaped cutting surface that interfaces with the outer tube. The scalpel is used as a single pass instrument, removing a predetermined amount of bone in a single pass. In some embodiments, the scalpel also has a tube that sprays water for irrigation, while the outer tube has a suction line for clearing the slurry of removed bone. 
     In some embodiments, the scalpel can be navigated and ride down a slot provided in the inside wall of the outer tube. The slot depth can be predetermined to provide depth-controlled milling, and to control where cutter goes. This is advantageous because it is believed that freehand cutting hits the nerves too easily. The shape and size of the cutting surface can define the specific area of bone to be removed. The specificity of cut is advantageous because it minimizes the amount of bone removal, which is beneficial in the highly enervated facet. Thus, a quicker procedure, less trauma (less pain), and more stable construct is realized. 
     Viewing Element (Olive) 
     In some embodiments, the chip viewing element can be angulated so it can see around a corner of the tube, 
     In conventional-endoscope, visualization is 2D (i.e., no depth perception), and so two nerves may look close together when they are actually 2 cm apart. Thus, in some embodiments, the endoscope is modified so that the chip acts like a range finder. In particular, the chip identifies and assesses a reference feature that is a known distance from chip, and then measures how far away a nerve is from chip (which is the tube end) based on that assessment. 
     Nerve Deflection (Tube in Tube) 
     In some embodiments, the outer shield has a pressure sensor thereon to measure the stress on the nerve. Using ultrasound techniques that can measure distance, the system can measure the elongation of nerve under retraction and define a maximum elongation limit (e.g., 20%), and then warn the surgeon if the elongation limit is exceeded. In some embodiments, the system integrates ultrasound into the port and thereby navigates the port. 
     In some embodiments, the surgeon navigates the camera. This allows the surgeon to understand orientation of the camera. 
     In some embodiments, visualization provides an axial view of the disc, so the surgeon can understand the location of the disc removal tool. 
     Neuromonitoring Analytics 
     Currently, neuromonitoring devices can be used to obtain an indication of potential nerve health or nerve damage, which may be induced in a surgical setting. This indication of nerve health is achieved by measuring electrical impulses between a nerve near a surgical site and a far end of the nerve. For example, impulses may be measured between a nerve root at the spine and some point found on the legs. 
     Nerve damage can be caused through direct manual contact with a nerve. Apart from gross damage such as severing or crushing the nerve, other lesser forces imparted on the nerve can also cause damage. For example, displacing the nerve, stretching it, or compressing it can cause significant damage. In some cases, extended application of such forces to the nerve can reduce blood flow through the nerve, again causing nerve damage. Often times, this exposure time is dependent on the amount of force applied. Accordingly, there appears to be no known steadfast rule as to how long the surgeon may be able to load a nerve. 
     Alternate forms of evaluating potential nerve damage besides neuromonitoring may bring new insights into nerve protection during a procedure. In this regard, nerve manipulation measurement could yield an indication of risk to the nerve. If a nerve is displaced for the procedure, it may be elongated or it may be displaced laterally. These alterations in the nerve&#39;s physical features could be measured and use to predict potential nerve damage. Accordingly, other potential features could be measured and used to predict potential nerve damage include arc length and the diameter of the nerve itself etc. These features may be measured in quantifiable terms via techniques such as ultrasound. The resulting measurements are and then analyzed (via software or manually) in terms of absolute value, percent change or some other metric indicative of potential nerve risk/damage that can be obtained from a database or library. In some embodiments, these metrics can be used as predictors of the safe length of time that a nerve can have a given displacement or deformation without causing long term damage. Calculation or algorithms can also be used to determine a maximum safe deformation, or a maximum allowable time during which a nerve can have a given deformed feature. 
     This measurement could be obtained in many ways. It can be measured manually, optically or through some other form of imaging. This could occur in an open procedure, subcutaneously in an MIS or other type of procedure. Direct visualization could be completed with the use of a camera. Before and after images could be interpreted to calculate the amount of absolute deformation or percent change. The measurements can be obtained through modalities such as ultrasound, or other forms of imaging that can “see” soft tissue or identify nerve tissue relative to the surrounding tissue (X-ray, CAT/PET scan, MRI, etc.). 
     Other measurement methods that can be used in accordance with this embodiment may include a) measurement of density change within the nerve due to loading, or b) change in blood flow. Such measurements can be obtained through radar, ultrasound and other imaging methods. 
     In some neuromonitoring embodiments, it may be possible to measure impedance within the nerve or impulses, wherein this may be done locally relative to the specific deformation area of the nerve. In particular, in some embodiments discussed herein, the nerve shield could have a sensor on opposite edges of the shield that would contact the same nerve in two different nerve locations. These sensors would allow the surgeon to read electrical values such as impulses or resistance, before nerve distention and then measure it again as distention occurs or is achieved. The difference in these measured values could be an indicator as to the level of deformation. Any of the neuromonitoring features described above or elsewhere herein can be incorporated into or included in the multi-tool. For example, the above-described sensors can be mounted to a shaft component of the multi-tool, which can be used to position the sensors in proximity to nerve tissue. 
       FIG.  50    discloses a cookie cutter-type distal end  142  of an ultrasonic cutter having a semicircular cutting piece cutter bone. 
       FIG.  51    discloses a mini flex arm  146  connecting an outer tube  246  and a screw extension  346 . 
       FIG.  52    discloses an outer tube/inner retractor assembly wherein the inner retractor  151  is tilted inwards to retractor soft tissue. 
       FIG.  53    discloses an outer tube/inner retractor assembly wherein the inner retractor  152  runs parallel with the outer tube  252 . 
       FIG.  54    discloses an endoscope  154  housed within an outer tube, and an inner tube  254  extending from the outer tube. 
     In many embodiments disclosed above, an inner shield nests within an outer shield. In an alternative embodiment to all such embodiments, however, the inner shield is replaced with a removable blade that is integrated into a cutout formed within the wall of the outer shield. In such cases, the outer surface of the inner shield substantially nests within the outer surface of the outer shield so that the flange extends distally past the distal end portion of the outer shield. 
     In many embodiments disclosed above, the proximal end portion of the substantially tubular portion of the inner shield comprises a stop adapted to abut the proximal end portion of the outer shield, the stop being adapted to prevent excessive distal movement of the inner shield. In other embodiments, the abutment occurs anywhere along the outer shield. 
       FIGS.  55 - 63    disclose some of the instruments used in preferred procedures disclosed herein. 
     Pedicle Post w/ Reference Array 
     Now referring to  FIG.  55   , a first step of a navigated procedure is the placement of a Pedicle Screw (such as Viper 2 or Viper Prime, available from DePuy Synthes Spine, Raynham, Mass.)) in the contralateral caudal vertebral body followed by the insertion of a center core  501  including a polyaxial blocking post  503 , which engages with the thread for a locking cap of the Pedicle Screw. When tightened, the polyaxiality of the screw is fully blocked. A screw  505  locks the Center Core with the Polyaxial Blocking Post. A clamp  507  with an eccentric lever securely connects the Reference Array  509  on the Pedicle Post. Two addition screw connections  511 ,  513  allows the surgeon to align the Reference Array set up with the cameras to the navigation system, which are most commonly places at the caudal side of the patient. 
     The Reference Array should directly be mounted on Blocking Core (see Pedicle Anchor). In some embodiments, there is an adjustable orientation of the array on the post. In some embodiments, care is taken to make sure that the distance between the handle and the top of the counter-torque insert is greater than the length of the screws. In some embodiments, the navigation array is strong enough to act as counter-torque for polyaxial blocking (which would be done before registration. 
     Multi-Tool 
     Now referring to  FIG.  56   , there is a provided a Multi-Tool probe comprising a main body  515  including a Navigation Array (single piece), a Blunt Mandrin  517 , a Sharp Mandrin  519  and a Detachable Handle  521 . This set of features allows the surgeon to use the device as a Navigation Pointer (with Blunt Mandrin), a navigated Jamshidi-Needle (Sharp Tip), and a device to navigate the insertion of Dilatation Tubes as well as the Access Tube (see below). This tool uses a single array and the resulting single registration procedure covers four functions. In some embodiments, the array is part of a detachable handle. 
     As noted above, the multi-tool can include integrated or built-in neuromonitoring, e.g., for detecting the presence, proximity, health, or other attributes of nerve tissue. For example, as shown in  FIG.  56 A , one or more shaft components of the multi-tool can include a neuromonitoring sensor  522 . The sensor can include one or a plurality of sensors. The sensor can be configured to detect the presence, proximity, health, or other attributes of nerve tissue. For example, the sensor can be configured to assess nerve heath using functional near-infrared (fNIR) spectroscopy, e.g., as described in U.S. Application No. 62/507,930 filed on May 18, 2017, which is hereby incorporated herein by reference. As another example, the sensor can be configured to measure electrical nerve impulses, EEG, EMG, evoked potentials, or the like. Nerve assessment data can be communicated to the surgeon to inform subsequent surgical steps. 
     As also noted above, and as shown in  FIG.  56 A , the multi-tool can include an electrode, transducer, or other energy delivery element  526  for applying energy to tissue, e.g., to ablate or cauterize the tissue. The multi-tool can include an energy delivery element in the form of a microwave ablation element. The multi-tool can include an energy delivery element of the type used in the NEUWAVE system available from ETHICON, INC. of Cincinnati, Ohio. The energy delivery element can be built-into the multi-tool, or can be supported or guided to a target location using the multi-tool. The energy delivery element can be mounted on a shaft or needle  524 . The needle can be coaxially received within or around another shaft component of the multi-tool. The multi-tool can be used to position the energy delivery element in proximity to a target location, such as an osseous bone tumor. Energy can be delivered from the energy delivery element to the tumor or other target location. 
     Pedicle Anchor 
     Now referring to  FIG.  57   , there is provided a Pedicle Anchor based on conventional screws that comprises a Center Core  523  including a Polyaxial Blocking Post  525 , which engages with the thread for the Locking Cap of the Screw. When tightened, the polyaxiality of the screw is fully blocked. A screw  527  locks the Center Core with the Polyaxial Blocking Post. In other embodiments not including the above Pedicle Post with Reference Array, the interface to attached devices (Mini-Flex-Arm) is not realized by using a Clamp but by a non-detachable feature (sphere,  529 . This provides sufficient stability and is a simple add-on to existing screw systems. 
     Dilatation Tubes 
     Now referring to  FIG.  58   , there is provided a dilatation System comprising a set of Tubes  531  having outer diameters that match the current Access Tube (outer shield) inner diameters of 12 mm, 15 mm and 18 mm. They are all circular shaped in the cross sectional plane and slotted in the longitudinal axis in order to be placed over the Multi-Tool probe (see above) and pass the connection of the Navigation Array with the cannulated cylindrical body of the Multi-Tool. In some embodiments, the set of Tubes have outer diameters (ODs) of OD1=12 mm, OD2=15 mm, and OD3=18 mm. 
     Mini-Flex Arm 
     Now referring to  FIG.  59   , there is provided a Mini-Flex-Arm comprising of two clamps  533 , 535  that are attached to spherical connectors on the Pedicle Anchor and Access Tube (outer shield) and therefore allows for a polyaxial adjustment to the attached devices. In an unlocked position, the segmented arms with ball and socket elements  537  in combination with the polyaxial clamps allow for a non-restricted 3-dimensional placement of the Access Tube (outer shield). The System can be locked with a single point handle  539  that tightens a multi-core wire  541 . A potential elongation of the wire over time which would have a negative effect on the fixation properties of the device can be compensated on a screw  543  by adjusting the effective length of the wire. 
     Access Tube (Outer Shield) with Soft Tissue Retractor 
     Now referring to  FIG.  60   , there is provided an Access Tube (outer shield)  545 , which is a simple cylindrical tube with a distal flange, with a non-detachable feature (sphere,  547 ) that connects it with the Mini-Flex-Arm. The Soft-Tissue-Retraction-Blade (inner shield)  549  is placed within the Access Tube. An attached spring  551  allows for a central insertion. As soon as the blades get released (handle,  553 ), the spring pushes the Blade (inner shield) against the inner wall of the Access Tube (outer shield) and therefore retracts the soft tissue on its distal end. The Blade (inner shield) remains free rotation and is held with the Access Tube (outer shield) by a pure fictional force. In some embodiments, there is the option to use two Soft-Tissue-Retraction Blades (inner shields) at the same time which would meet the requirements to use this embodiment for TLIF Procedures since it allows for the retraction of the transverse as well as the exiting nerve. In some embodiments, the Detachable Handle is replaced by a simple permanent handle with a length of about 25 mm. 
     Access Tube (Outer Shield) with Integrated Endoscopy 
     Now referring to  FIG.  61   , there is provided an Access Tube (outer shield) with an integrated endoscope and a non-detachable feature (sphere,  555 ) that connects it with the Mini-Flex-Arm. The depth adjustable Endoscope System is held in a channel  557  that has a spring feature  559  to increase the friction and therefore hold the endoscope in place. The Endoscope system  561  consists of the endoscope itself (OD=4 mm) and  2  tubes, one for irrigation  563  and the other one for suction  565 . In some embodiments, the Endoscope is depth adjustable. In some embodiments, the endoscope&#39;s channel will be parallel to the Access Tube (outer shield) Lumen. 
     Navigation Plug 
     Now referring to  FIG.  62   , in some embodiments, there is a Navigation Plug  567  that is placed in the Access Tube (outer shield)  569  and allows the placement of the Multi-tool (see above) in the Center of the Access Tube (outer shield) flush with its distal end. This embodiment allows the visualization of the central longitudinal axis of the Access Tube (outer shield) as well as its distal end in the Navigation System. Because, in some embodiments, access trajectory is considered to be of higher importance than depth, the trajectory line could be graduated to offer information of depth in combination with known port length. 
     Discectomy Tool with Handle 
     Now referring to  FIG.  63   , there is provided an attachable handle  571  is directly attached to a standard suction-based discectomy tool  573  via an Adapter Plate  575  that clamps to the discectomy tool containment with  3  screws. In a first embodiment of this Adapter Plate, it only holds the attachable Handle, while in a second version it holds an additional Navigation Array. The Navigation Array is pre-calibrated: After letting the Navigation System know what specific discectomy tool is currently used, it shows the correct dimension and tip of the device in the pre-registered x-ray views in real time. 
       FIGS.  64 - 90    disclose some of the instruments in their contemplated in-spine use orientations in preferred procedures disclosed herein. 
     Step 1 Placement of Ref. Array 
     Step 2 Placement of Pedicle Anchor 
     Step 3 Placement of Access Tube 
     Step 4 SAP removal 
     Step 5 Soft Tissue Retraction 
     Step 6 Disc Removal 
     Step 7 Insertion of Expandable Cage and Bone Substitute 
     Step 8 Posterior Stabilization 
     Now referring to  FIGS.  64 - 65   , in one embodiment, a polyaxial screw is inserted contra-laterally into the spine via post  576 . A navigation reference array  577  is then fixed mounted on a Polyaxial Blocking Post  579 , and engaged in the distal thread (not visible, inside screw/tab) for the Locking Cap of the Pedicle Screw. 
     Step 1 Placement of Reference Array. 
     Step 2 Placement of Pedicle Anchor 
     Now referring to  FIG.  66    a pedicle Anchor  581  with Connector Interface  583  is placed on the contralateral side 
     Now referring to  FIG.  67   , a pedicle anchor  585  is placed on the ipsilateral side. 
     Step 3 Placement of Access Tube 
     Now referring to  FIG.  68   , a Multitool  587  is inserted into the spine for determination of Target Area  589  and trajectory of Dilators/Access Tube. Neuromonitoring features of the multi-tool can be used during insertion or at any other desired time to avoid or navigate around nerve tissue, to safely retract nerve tissue, and/or to assess the health of nerve tissue. The multi-tool can integrate multiple components into a single navigated tool to reduce the number of instruments tracked separately during surgery, e.g., as part of a procedure to insert an access port into a patient during a surgical procedure. Additional embodiments of a multi-tool are described in connection with  FIGS.  91 - 125    below. 
     Now referring to  FIG.  69   , the K-Wire and Handle are removed from the multi-tool for next step. After placing the Multitool  591 , the K-Wire  593  needs to be removed in order to allow the removal of the Handle  595 . 
     Now referring to  FIG.  70   , Multi-step dilatation is carried out to prepare for Access Tube (outer shield) insertion. The removal of the handle (see previous step) allows the placement of the first, second and third dilators  597  to prepare for Access Tube insertion. 
     Now referring to  FIG.  71   , the navigation array is removed from the Multi-tool base. Since it is clinically important to keep the target point of the Access Tube (outer shield) positioning, the Access Port can be placed over the main Body  599  of the Multi-Tool by removing the Navigation Array, leaving behind the Navigation Array Interface  601 , which allows a play free, load bearing and bi-unique fixation of the Reference Array. 
     Now referring to  FIG.  72   , the Access Tube (outer shield) is inserted over the dilatators  602  (wherein the viewing element Chip-on-tip scope is pre-mounted). The Access Tube (outer shield) is telescopic and can be adjusted in length, stabilized with a ratchet mechanism  603 . It comprises a distal segment  605  that holds a depth adjustable Chip-on-Tip Camera  607  housed in a channel  609  which is integrated into the wall of the distal segment. A proximal portion of the access tube (outer shield)  611  slides over the distal segment and holds a connector interface  613 . 
     Now referring to  FIG.  73   , once the Dilators as well as the Body of the Multi-Tool have been removed, the Access Tube (outer shield)  615  offers free access to the SAP. 
       FIG.  74    discloses connectors to the Visualisation Box and the Cleaning Box (water and suction). The Chip-on-Tip Camera comprises the actual Camera  617  disposed in the access tube (outer shield) and a main connector plug  619  that provides power supply, data cables and light to the Camera. There are also two tubes for irrigation and suction  621 , 623  to provide a cleaning feature for the Camera Lens, which merge into a single cable  625  connected to the Camera and extending from the access tube (outer shield). 
     Now referring to  FIG.  75   , the Access Tube (outer shield) is Fixed to the ipsilateral or contralateral pedicle anchor. The Access Tube  627  is rigidly attached to the contralateral  629  or ipsilateral (not shown) Pedicle Anchor via a Connector  631 . This Connector allows the locking of the Access Tube in any 3D position. It comprises ball and socket segments  635 , two Interface Clamps  637   a ,  637   b  and an inner wire (not visible) that is put under tension by an adjustable  639  single point fixation handle  641  and thereby blocks the single joints of the two Interface Clamps and segments by increasing their absolute friction. The single point fixation Connector is designed to minimize the accruing forces on the Access Tube, as well as the pedicle Anchor, during tightening of the construct. Another Connector Design (not shown) is reverse in function, in that it is permanently stable unless the inner wire is released via the single point fixation Handle. 
     Step 4 SAP Removal 
     Now referring to  FIG.  76   , there is provided an axial view of the Access Tube, wherein the surgeon is ready to start cutting the SAP. Disclosed in the FIG are Single segment  643  and Connector Interface  645  of the Mini-Flex arm, outer proximal portion  647  of a Telescopic Access Tube; Inner distal portion  649  of Telescopic Access Tube; Cable of integrated Chip-on-Tip Camera  651 ; and unretracted Nerve UN. 
     Now referring to  FIG.  77   , there is provided disposition of an Integrated Scope, which includes Outer proximal Tube  653  of Telescopic Access Tube; Inner distal Tube  655  of Telescopic Access Tube; Exiting Cable of integrated Chip-on-Tip Camera  657 ; Chip-on-Tip Camera in housing  659 ; and Projected field of view of Chip-on-Tip Camera PF 
     Now referring to  FIG.  78   , in some embodiments, there is optional Navigation of the Access Tube through use of the Multi-Tool with a Navigation Plug. In conjunction with a Navigation Plug  661 , the Multi Tool  663  can also be used to visualize the trajectory as well as the distal end of the Access Tube  665  using navigation. The Navigation Plug sits on the proximal rim of the inner distal tube of the telescopic Access Tube, which leads to an accurate visualization of the depth perception independently from the position of the outer proximal tube and therefore total length of the Access Tube. 
     Now referring to  FIG.  79   , there is provided carrying out SAP removal via the use MIS high-speed drills or manual tools. The SAP will be (partly) removed using a high speed Power Tool such as an Anspach System  667 . The Burr  669  will be partly shielded to increase safety. 
     Now referring to  FIG.  80   , further SAP removal by MIS high-speed drills or manual tools is demonstrated with respect to the different anatomical planes. The removal of the SAP with a Burr  671  takes place about 10 mm-20 mm above the nerve (2) level NL. 
     Step 5 Soft Tissue retraction 
       FIG.  81 - 82    disclose Soft tissue retraction, showing a clip directly on access tube, medial to lateral retraction.  FIG.  81    shows the Soft Tissue Retractor  673  before radial retraction of the nerve. At this state, the Soft Tissue Retractor is already engaged with the Access Tube  675 .  FIG.  82    discloses the Soft Tissue Retractor  673  after radial retraction of the nerve. 
       FIG.  83    discloses nerve Shielding and Positioning according patient anatomy.  FIG.  83    shows the fully engaged Soft Tissue Retractor  675  with a Clip  677  holding it on the proximal outer Tube  679  of the Telescopic Access Tube. The nerve N is fully retracted and protected by the Soft Tissue Retractor. 
     Step 6 Disc removal: 
     Now referring to  FIGS.  84 - 85   , disc clearing is performed with a suction-based discectomy tool  681  that holds the option to be navigated. Therefore there is a ring (not visible) mounted (welded/glued) on the shaft  683  of the discectomy tool that allows a play free mounting of a Navigation Array  685 . 
     Step 7 cage Insertion 
     In  FIG.  86    an expandable cage  687  is inserted into the disc space. In  FIG.  87   , the cage  687  is expanded to full expansion. 
     Now referring to  FIG.  88   , Bone graft  689  is inserted around the cage via a delivery system. The Expandable cage  687  is in its final position before detaching the Inserter. Bone Substitute  689  has been placed around the device (before and after inserting the cage) to ensure a proper fusion process. 
     Step 8 Posterior Fixation: 
       FIG.  89    discloses inserting the remaining screws  691 , while  FIG.  90    discloses placing rods  693  and fixing the construct. 
       FIG.  91    illustrates another embodiment of a multi-tool  700  that can be used for surgery, e.g., posterior lumbar surgery. For example, the multi-tool  700  can include a cap  702  having one or more coupling features  704  thereon. The coupling features  704  can couple or integrate one or more surgical devices, instruments, implants, and/or other objects into a single tool, e.g., the multi-tool  700 . The instruments coupled to the multi-tool  700  can then be tracked using surgical navigation, thereby eliminating the need to track the individual instruments separately. 
     The coupling features  704  can include one or more arms or connectors  706  that extend or protrude from the cap  702 . Each arm  706  can integrate with one or more instruments to form the multi-tool  700 . The arms  706  can be spaced apart along the surface of the cap  702  to prevent the instruments from cluttering a single location and providing access to the surgical area. The instruments that can couple to the cap  702  can assist with navigation and insertion of the shaft component into a surgical site to dilate the site. For example, as shown, a shaft component  707 , a navigation marker or array  708 , and a nerve mapping tool  710  can mate to the arms  706  to form the multi-tool  700 , though, in some embodiments, one or more of these instruments can be omitted or replaced by other instruments. Some non-limiting examples of instruments that can be coupled to the multi-tool  700  can include dilation instruments, e.g., serial dilators or tube inserters, cutting instruments, e.g. scalpels, scissors, and so forth, and/or mapping instruments, e.g., ultrasound, can be added to the multi-tool. 
     The instruments can be shaped so as to be received in openings in the arms  706 , though in some embodiments, the instruments can be integrally formed with, or fixedly attached to, the arms  706 , or snap-fit, glued, stapled, or received in recesses, openings, and/or other surfaces of the cap  702 . In some embodiments, the arms  706  of the cap  702  can include one or more securement features adapted to retain one or more of the instruments therein. For example, the arms  706  can include a throughhole  711  formed therein. The throughhole  711  can be formed in one or more surfaces of the cap  702  to form a channel that extends through the cap  702 . The throughhole  711  can extend through a portion of the cap  702 , as shown, in  FIG.  94 A , or extend entirely through the cap. The throughholes  722  can retain one or more of the instruments therein. 
     The cap  702  of the multi-tool  700  can couple to a shaft component  707 . For example, the shaft component  707  can be received in one or more of the coupling features  704  in the cap to couple thereto. The shaft component  707  can be introduced into an incision in a target site of the patient to increase or dilate the target site. As shown, the shaft component  707  can be advanced proximally through the cap  702  until one or more grasping features (not shown) within the cap  702  secure the cap to the shaft component  707 . In some embodiments, the grasping features can include a releasable member  712  or another feature that regulates the distance which the shaft component  707  can travel through the cap  702 . The releasable member  712  can be actuated by the user to toggle the cap  702  between a plurality of shaft components, or between other instruments, as described further below. 
     The navigation marker  708  can be attached to the multi-tool  700  such that a position and orientation of the multi-tool  700  with respect to the marker  708  is known. The marker  708  can be embedded in a surface of the multi-tool or can extend outward from the multi-tool. In some embodiments, the marker  708  can be rigid or formed integrally with the cap  702 , as described further below, to ensure navigational accuracy and/or precision. 
     For example, as shown, the navigation marker  708  can connect to one of the arms  706  that protrude from the cap  702 . The navigation marker  708  can be a symbol or image having a known size, shape, or other characteristics to facilitate recognition of the position marker in captured images of the multi-tool  700 . While a single navigation marker  708  is shown, the multi-tool  700  can include multiple markers, e.g., one at each end. Use of multiple markers  708  can improve tracking accuracy, field of view, or redundancy. The marker  708  can be detected by a navigation system  101 , can communicate with the navigation system  101 , or can be otherwise operably coupled to the navigation system  101  to allow the position and/or orientation of the multi-tool  700  and the underlying anatomy to be registered with and tracked by the navigation system  101 . Having the multi-tool  700  connect the instruments as a single functional unit allows for tracking of the unit as a whole relative to one another and the target site when the shaft component is docked in the target site, which can prevent the need to place a separate marker on each instrument and conduct a cumbersome and time-consuming registration process for a large number of markers. The cost and complexity of the navigation system  101  can be reduced by reducing the number of markers that the system must track. Use of a single marker  708  can also provide greater access to the vertebral column and a less cluttered surgical site. 
     It will be appreciated that the structure and operation of the marker  708  can vary depending on the type of navigation system  101  used. In the illustrated embodiment, the marker  708  includes four sphere-shaped fiducials for use with an optical navigation system. The fiducials can be arranged in predetermined positions and orientations with respect to one another. The fiducials can be positioned within a field of view of the navigation system  101  and can be identified in images captured by the navigation system. Exemplary fiducials include infrared reflectors, LEDs, and so forth. The marker  708  can be or can include an inertial measurement unit (IMU), an accelerometer, a gyroscope, a magnetometer, other sensors, or combinations thereof. The sensors can transmit position and/or orientation information to the navigation system  101 , e.g., to a processing unit of the navigation system. 
     The marker  708  can be configured to be visible or detectable in patient imaging performed preoperatively, intraoperatively, or postoperatively. For example, the marker  708  can include radiopaque portions to facilitate visualization of the marker in X-ray, CT, or fluoroscopy. By way of further example, the marker  708  can include metallic, magnetic, or other materials visible under MRI. 
     Any of a variety of surgical navigation systems  101  can be used, including commercially available systems such as those offered by BRAINLAB AG of Germany. The navigation system  101  can include an imaging system with a camera or image sensor that captures images of a surgical site and objects within the surgical site, such as the marker  708  and a similar marker attached to an instrument. The captured images can be registered to one or more patient images. The captured images and/or the patient images can be processed using a processor to determine a position and/or orientation of the instrument relative to an anatomy of the patient. This information can be communicated to a user, e.g., using an electronic display or a tactile, audible, or visual feedback mechanism. 
     The nerve mapping tool  710  can be attached to the multi-tool  700  to provide feedback and plans of nerve location. For example, the nerve mapping tool  710  can include a plug that is configured to be received in one or more of the arms  704  of the multi-tool  700  to track the distances of one or more of the instruments, e.g., the shaft component  707 , from nerves. Any of a variety of nerve mapping tools can be used, including those using various technologies, such as electromyography (EMG) and mechanomyography (MMG), as in commercially available systems offered by Sentio. The nerve mapping tool  710  can detect nerve location so as to prevent damage during insertion of the shaft component or use of the other instruments of the multi-tool. 
     For example, the nerve mapping tool  710  can include an invasive stimulator capable of providing an electrical stimulus, mechanical sensors to monitor muscle movement, and a processor that can determine if a sensed movement was caused by the provided electrical stimulus. The nerve mapping tool  710  can identify the presence of nerves during a lateral approach to the spine, though it can be modified to detect nerves in a variety of target sites. Some non-limiting examples of the nerve mapping tool  710  can include the use of MMG in robotic surgical procedures, avoiding nerve damage in pelvic floor procedures such as prostate surgery, using MMG system in a diagnostic capacity to evaluate changes nerve health, and so forth. 
       FIG.  92    illustrates one embodiment of the shaft component  707  used with the multi-tool  700 . The shaft component  707  can be inserted into an incision in the patient to dilate the surgical site. The shaft component  707  can include a solid shaft, though, in some embodiments, the shaft component can be hollow to allow one or more surgical devices to pass therethrough. The shaft component can be made from metal, plastic, polymer, or any other material that can be used during dilation as appreciated by one skilled in the art. The shaft component  707  can have a generally cylindrical shape as shown, though the shaft component can be circular, triangular, pyramidal, and so forth. 
     As shown, the shaft component  707  can include a proximal handle  714  that tapers to a distal tip  716 . The handle  714  can be adapted to be received in the cap  702  as mentioned above, and described in further detail below. In some embodiments, the proximal handle  714  can include grooves or annular rings  715  that extend along a portion thereof to allow for enhanced gripping of the shaft component. The shaft component  707  can have a diameter D that ranges from about 1 mm to about 10 mm, about 2 mm to about 9 mm, about 3 mm to about 8 mm, about 4 mm to about 7 mm, or about 5 mm to about 6 mm. 
     An embodiment of the distal tip  716  is shown in greater detail in  FIG.  93   . The distal tip  716  can be adapted to be docked into target tissue to secure shaft component  707  within the surgical site. The distal tip can include a hemispherical shape, as shown, though, in some embodiments, the tip can be pointed, sharp, blunt, and so forth. In the embodiment shown, the hemispherical geometry of the distal tip can allow the tip to be swept over the target site and gently pushed into the target tissue, e.g., disc or bony surface. The distal tip  216  can have a length L that ranges from about 1 mm to about 10 mm, about 1.5 mm to about 9 mm, about 2 mm to about 8 mm, about 2.5 mm to about 6 mm, or about 3 mm to about 4 mm and a diameter that ranges from about 0.25 mm to about 3 mm, about 0.5 mm to about 2.5 mm, about 1 mm to about 2 mm, or about 1.5 mm. 
     In some embodiments, the shaft component  707  can include a dielectric coating along a length thereof to insulate the shaft component, though one or more portions thereof can be free of electrical insulation so as to conduct electrical current. For example, the shaft component  707  can include one or more conducting regions that are adapted to electrically communicate with, and/or conduct electric current to, instruments of the multi-tool and/or the target site. As shown, the proximal handle  714  can include a first conducting region  718  on a proximal-most end thereof and the distal tip  716  can include a second conducting region  720  on a distal-most end thereof. Each of the first and second conducting regions  718 ,  720  can form an electrode surface or serve as an interface which can form an electrical connection to one or more instruments of the multi-tool  700 . For example, the first conducting region  718  can form an electrical connection with the nerve mapping tool  710 , as described further below, while the second conducting region  720  can form an electrode surface by which the shaft component  707  can conduct electric current from a source, e.g., the nerve mapping tool  710 , to tissue. While two conducting regions are shown, it will be appreciated that one or three or more conducting regions can be formed on the shaft component  707  to form electrical connections therewith. 
       FIGS.  94 A- 94 C  illustrate the components of the cap  702  in greater detail. In some embodiments, the cap  702  can include a throughbore  724  formed therein. The throughbore  724  can be positioned in an intermediate portion of the cap  702 , as shown in  FIG.  94 B , to couple one or more features of the multi-tool thereto. For example, as shown, the throughbore  724  can be adapted to receive the releasable member or button  712  therein. The button  712  can be positioned within the throughbore, as shown in  FIG.  94 A , or can be fixedly attached to the cap  702 . In some embodiments, the button can be a single, monolithic component, or formed from two or more separate pieces that are configured to move relative to one another to toggle the button between one or more configurations. 
     The button  712  can be adapted to retain surgical devices within the cap. For example, the button  712  include one or more features for coupling to surgical devices. In some embodiments, the button  712  can include a hollow interior to allow surgical devices to pass therethrough. For example, as shown in  FIG.  94 A , the shaft component  707  can pass through an interior bore  725  of the button  712  to attach the shaft component  707  to the cap  702 . The bore  725  can extend through a diameter of the button to pass the shaft component  707  therethrough. The bore  725  can be shaped in the manner of the shaft component, e.g., D-shaped as shown in  FIG.  94 C , to prevent rotation of the shaft component  707  relative to the cap  702 . 
     The button  712  can include one or more biasing features configured to toggle the button  712  between the locked and unlocked configurations. For example, the button  712  can include one or more bias elements or springs  726  that extend through the button. The bias elements  726  can abut an inner surface of the button and a wall of the throughbore  724  to exert a biasing force on the button. The button  712  can include two bias elements  726 , as shown, though it will be appreciated that one, or three or more bias elements can be used. 
     The button  712  can be adapted to be toggled between a locked configuration and an unlocked configuration. For example, the button  712  can be depressed or pushed into the throughbore  724  to move the button from the locked configuration to the unlocked configuration. In the locked configuration, the button  712  can prevent the shaft component  707  from moving relative to the cap  702 , while in the unlocked configuration, the button  712  can allow the shaft component  707  to move relative to the cap  702  within the bore  725 . In the locked configuration, the bias element  726  can be fully extended to apply an outward force on the button  712  relative to the throughbore  724 . The outward force can bias the button  712  to protrude from the throughbore  724  which can prevent the shaft component  707  from traveling freely through the throughbore. 
     In some embodiments, one or more features of the button  712  can be configured to engage the shaft component  707  to lock the shaft component  707  within the cap  702 . For example, the button  712  can include a grasper (not shown) to secure a longitudinal position of the shaft component  707  within the bore  725 . The grasper can be located in an interior portion of the button  712  to mate with the handle  714  of the shaft component  707 . For example, as the shaft component  707  advances proximally through the bore  725 , the shaft component  707  can contact the grasper to prevent further proximal translation of the shaft component. In some embodiments, the shaft component  707  can include an indentation configured to form a male-female interlock with the grasper. In such embodiments, the grasper can be configured to travel along a surface of the shaft component  707  until contacting the indentation. At the indentation, the grasper can extend into the indentation to lock the longitudinal position of the shaft component  707  relative to the button  712 . In some embodiments, the button  712  can provide tactile feedback to a user when the button  712  locks to the shaft component  707 . Imparting a force in an opposite direction of the outward force can detach the grasper from the shaft component  707  to toggle the button  712  from the locked configuration to the unlocked configuration to allow the shaft component  707  to longitudinally translate relative to the cap  702  and to detach the cap from the shaft component, e.g., once the shaft component is implanted and/or docked in target tissue. The ability to detach the cap  702  from the shaft component  707  can allow the cap  702  to be attached to other instruments, such as other shaft components, as well as allow for serial dilation or other instruments to be inserted over the shaft component  707  to increase a size of the target site, as described further below. 
     The button  712  can include one or more channels  728  therein. For example, the bias elements  726  can be disposed in channels  728  that run through the button  712 . As shown, the channels  728  can run perpendicular to the shaft component  707  through the interior of the button  712  to move the button in a direction perpendicular to the shaft component. The channels  728  can run through a width of the button  712 , or terminate in an intermediate portion thereof, as shown. 
     The cap  702  can allow for communication between system components disposed therein. For example, the throughholes  711  in each of the arms  706  can lead into a hollow portion of the cap to allow communication between the components disposed therein. In some embodiments, the cap  702  can facilitate an electrical connection between multiple components of the multi-tool  700 . For example, the nerve mapping tool  710  can interface with the shaft component  707  to establish an electrical connection therebetween. For example, the nerve mapping tool  710  can include a conductive member  730  thereon to conduct the electrical connection. As shown, the conductive member  730  can be a spring member that can vary a distance between the nerve mapping tool  710  and the shaft component  707 . The conductive member  730  can contact an exposed core of the shaft component  707  to complete a circuit between the shaft component  707  and a distal electrode coupled to the nerve mapping tool  710 . In some embodiments, the electrical connection with the nerve mapping tool  710  can be used as a stimulation electrode having muscle activity sensors thereon to detect movement of muscles in response to a stimulus applied to the spine by the shaft component. As shown, the conductive member  730  can be a spring member that can vary a distance between the nerve mapping tool  710  and the shaft component  707 . In some embodiments, the conductive member  730  can be made of a metal, or another material that is adapted to conduct electricity. 
       FIGS.  95 - 97    illustrate an alternate embodiment of a cap  802  of a multi-tool  800 . Except as indicated below and as will be readily appreciated by one having ordinary skill in the art, the structure and function of the multi-tool  800  is substantially the same as that of the embodiment of the multi-tool  700  described above, and therefore a detailed description is omitted here for the sake of brevity. 
     The cap  802  can include one or more coupling features  804  thereon in lieu of, or in addition to, the coupling features  704 , e.g., arms  706 , discussed above with regards to  FIGS.  94 A- 94 C . For example, as shown, the coupling features  804  can include one or more modular attachment arms  806  that can be adapted to support a modular coupling of one or more components thereto. The modular attachment arms  806  can be formed in lieu of, or in addition to, the arms  706  discussed above with regards to  FIGS.  94 A- 94 C . 
     Use of a modular attachment arm  806  can allow the multi-tool  800  to be used in procedures that do not require navigation and/or to couple to other surgical devices, e.g., a second shaft component, a nerve mapping tool  710 , and so forth. The cap  802  can include a single modular attachment arm  806  for modular coupling, though, in some embodiments, the cap  802  can include two or more such arms. Further, although the navigation array  708  is described herein as being modularly coupled to the cap, as shown and described in  FIG.  97   , in some embodiments, one or more of the nerve mapping tool  710  and/or the shaft component  707  can also be modularly coupled to the cap  802 . 
     The modular attachment of the navigation array  708  to the cap  802  can be made in a variety of ways. For example, the modular attachment arm  806  can include a collet  808  configured to expand when the navigation array  708  is inserted therein. The collet  808  can be sized such that the collet can be received within, or otherwise interface with, a component of the multi-tool  800 , e.g., the navigation array  708 . The design of the collet  808  can allow the navigation array  708  to move relative to the modular attachment arm  806  to rigidly lock the array  708  to the multi-tool  800 . A rigid connection between the array  708  and the multi-tool can increase and maintain navigational accuracy. In some embodiments, the navigation array  708  can couple to the cap  802  in a single orientation. 
     The modular attachment arm  806  can include a bore  810  extending therethrough. The bore  810  can extend through an entire length of the modular attachment arm  806 , as shown, though, in some embodiments, the bore  810  can terminate along an intermediate portion of the arm  806 . The bore  810  can define a central longitudinal axis A therethrough for receiving coupling features and/or surgical devices therethrough to facilitate the modular coupling. 
     For example, the bore  810  can include a pin  812  extending therethrough. As shown, the pin  812  can extend along the central longitudinal axis A of the bore into the cap  802  to secure the pin within the bore  810 . The pin  812  can be configured to travel through the bore  810  to adjust the modular coupling to attach the surgical devices to the multi-tool  800 . 
     The pin  812  can include a pin head  814  formed thereon. As shown, the pin head  814  can protrude from the bore  810  in the modular attachment arm  806 . The pin head  814  can be formed of a square or rectangular element configured to be received in a coupling feature  709  of a surgical device, e.g., an opening in the navigation array  708 , though the pin head  814  can be circular, triangular, or another shape that corresponds to the coupling feature  816 , as shown in  FIG.  97   . In some embodiments, the pin head  814  can be keyed such that the opening  709  can be prevented from coupling to the pin head  814  in all but one orientation, thereby ensuring a rigid connection is formed for enhanced navigational accuracy. 
     In some embodiments, the modular attachment arm  806  can include one or more slots  815  therein. As shown, the slots  809  can extend through a portion of the arm  806 , though, in some embodiments, the slots  809  can extend along an entire length of the arm  806 . The slots  815  in the arm can separate the modular attachment arm into a pair of fingers  816   a ,  816   b . The slots  815  allow the fingers  816   a ,  816   b  to move flex and/or bend with respect to one another, which limits the rigidity of the modular attachment arm  806 . 
     In some embodiments, the pin  812  can be preloaded between the fingers  816   a ,  816   b  such that pin head  814  protrudes from the modular attachment arm  806  as shown in  FIGS.  96 - 97   . The pin  812  can travel along the axis A through the bore. For example, a force applied onto the pin head  814 , e.g., by mounting a surgical device thereto, can cause the pin  812  to retract longitudinally into the modular attachment arm  806 . Retraction of the pin head  814  into the bore  810  as the surgical device, e.g., the navigation array  708 , is mounted onto the arm  806  can flex the fingers  816   a ,  816   b  outward as the pin head  814  advances through the bore  810 . As shown, the pin head  814  can be larger than the pin  812  to abut one or more surfaces of an interior surface of the modular attachment arm  806  to resist and/or movement of the pin  812 . During retraction of the pin head  814 , the size of the bore expands, separating the distance between the fingers. Retraction of the pin head  814  can continue until the fingers  816   a ,  816   b  abut the walls of an opening  709  in the array to secure the array to the modular attachment arm  806 . The fingers  816   a ,  816   b  can grip one or more interior surfaces of the opening  709  to maintain a rigid connection of the array  708  for accurate navigation. In some embodiments, the fingers  816   a ,  816   b  can include graspers  818  thereon to increase the surface area of the contact between the modular attachment arm  806  and the opening  709  of the navigation array  708  to increase rigidity of the coupling. 
       FIGS.  98 - 101    illustrate an alternate embodiment of a multi-tool  900 . Except as indicated below and as will be readily appreciated by one having ordinary skill in the art, the structure and function of the multi-tool  900  is substantially the same as that of the embodiments of the multi-tool  700 , 800  described above, and therefore a detailed description is omitted here for the sake of brevity. 
     The multi-tool  900  can include a cap  902  thereon. As shown, the cap  902  can include one or more coupling features  904  thereon in lieu of, or in addition to, the coupling features  704 , e.g., arms  706 , discussed above with regards to  FIGS.  94 A- 94 C . For example, as shown, the coupling features  904  can include one or more arms  906  that can be adapted to support coupling of one or more surgical devices thereto. The arms  906  can be formed in lieu of, or in addition to, the arms  706  discussed above with regards to  FIGS.  95 - 97   . It will be appreciated that a combination of arms and modular attachment arms can be formed on the cap  902  to vary the manner in which surgical devices are coupled to the multi-tool  900 . 
     For example, as shown, an arm  906  of the cap  902  can include a protrusion  907  that extends proximal to a body of the cap  902 . The protrusion  907  can be used in lieu of, or in addition to, the arms  706  or the modular attachment arm  806  described above. The shape of the protrusion  907  can correspond to that of a surgical device coupled thereto, or protruding therefrom, or the protrusion  907  can have a different shape than the surgical devices, such as oval, oblong, square, rectangular, triangular, and so forth. As shown in  FIG.  100   , the protrusion  907  can be received in an opening of a coupling  950  that is attached to the navigation array  708 , though, in some embodiments, the navigation array  708  can be inserted into an opening of the protrusion  907 . 
     The protrusion  907  can include an exterior sidewall  908  that defines a lumen  911  that extends through the protrusion  907  into the cap  902 . The lumen  911  can extend through the protrusion into a hollow portion of the cap  902 , as described with respect to the embodiments above. The lumen can extend along an axis A 1  that is parallel to the axis of the shaft component  707  inserted through the cap  902  from a proximal end  902   p  of the cap to a distal end  902   d  of the cap. The lumen  911  can receive instruments or tools therethrough for performing rod reduction, derotation, drilling, set screw insertion, and so forth. The instruments can be inserted proximally or distally through the lumen  911 . 
     In this embodiment, the cap  902  can facilitate electrical connections between several surgical devices. For example, any surgical device, e.g., the shaft component  707 , that is advanced into the cap  902  can become disposed within the lumen  911 . In some embodiments, the proximal handle  714  of the shaft component  707  can extend through the lumen  911  and the protrusion  907  to abut the proximal end  902  of the cap  902 . In some embodiments, and as shown in  FIGS.  99  and  100   , the proximal handle  714  of the shaft component  707  can extend through the hollow portion of the cap  902  such that the proximal handle  714  protrudes from the proximal end  902   p  of the cap  902 . When the proximal handle  714  protrudes from the proximal end  902   p , the proximal handle  714  creates a contact point to which an electrical connection can be coupled, as described further below. 
     One or more of the arms  906  that extend from the cap  902  can include an electrical component  909  therein to establish an electrical connection of the cap  902  to other surgical devices. The electrical component  909  can be in the form of a pin, bolt, spring, or another feature known to one skilled in the art that is configured to interface between two components. The electrical component  909  can be made from a metal, or another conductive material, to enable two or more devices to send an electrical signal to one another. In some embodiments, and as shown in  FIGS.  100 - 101   , the nerve mapping tool  710  can be inserted into the arm  906  to interface the nerve mapping tool  710  with the electrical component  909  and to connect the nerve mapping tool  710  to the other devices coupled to the multi-tool. 
       FIG.  101    illustrates the electrical connection that is established between the shaft component  707  and the nerve mapping tool  710  within the cap  902  in greater detail. The nerve mapping tool  710  can be inserted into the arm  906  over the electrical component  909  to receive the electrical component  909  therein. Insertion of the nerve mapping tool  710  over the electrical component  909  can advance the electrical component  909  further into the hollow portion of the cap  902  to abut the shaft component. The connection between the shaft component  707  and the nerve mapping tool  710  at the electrical connection can allow current to travel from the nerve mapping tool  710 , through the pin, through the shaft component  707  to the distal tip  716  into tissue in which the shaft component  707  is disposed. In some embodiments, the shaft component  707  can include a throughhole therein configured to receive the electrical component  909 . The throughhole can be configured to receive a portion of the electrical component  909  therethrough, as shown, to establish an electrical connection between both devices. 
     In some embodiments, the multi-tool  900  can allow for more than two devices to be electrically connected. For example, one or more devices can attach to the protrusion  907 , and to the handle of the shaft component  707  protruding proximally therefrom, to establish an electrical connection therebetween. The first conducting region  718  of the shaft component  707  can provide another surface that couples to surgical devices that is configured to establish an electrical connection therebetween. Electrical signals can travel from the electrical component  909  through the shaft component  707  and into the first conducting region  718 , and travel to surgical devices coupled thereto. 
       FIG.  102    illustrates an alternate embodiment of a multi-tool  1000 . The multi-tool  1000  can include a cap  1002  having a single arm  1006  extending therefrom. The arm  1006  can be fixedly coupled to, or integrally formed with, the cap. As shown, the cap  1002  can include an exterior sidewall  1008  that defines a lumen  1011  that extends therethrough and is configured to receive the shaft component  707  therein. The nerve mapping tool  710  can be received in the arm  1006  to establish an electrical connection therebetween. 
       FIG.  103    illustrates an alternate embodiment of a multi-tool  1100 . Except as indicated below and as will be readily appreciated by one having ordinary skill in the art, the structure and function of the multi-tool  1100  is substantially the same as that of the embodiments of the multi-tool  700 ,  800 ,  900 ,  1000  described above, and therefore a detailed description is omitted here for the sake of brevity. 
     The multi-tool  1100  can include a cap or locking handle  1102  having multiple components that are configured to move relative to one another to couple one or more surgical devices thereto. As shown, the locking handle  1102  can include a base clamp  1120  and a top clamp  1130 , each having one or more surgical devices coupled thereto. One skilled in the art will appreciate that surgical devices can be coupled to either, or both, of the base clamp  1120  and the top clamp  1130 , as described further below. In use, the base clamp  1120  and the top clamp  1130  can rotate relative to one another to move the locking handle  1102  from an open position to a closed position to lock the shaft component  707  to the locking handle  1102 . 
     The locking handle  1102  can include one or more connection points or ports  1122 ,  1132  therein to which the surgical devices can be coupled. For example, as shown, the locking handle  1102  can include two ports  1122 ,  1132 , each having one of the navigation array  708  and the nerve mapping tool  710  coupled thereto, though, in some embodiments, the locking handle  1102  can be coupled to one or three or more surgical devices. While the navigation array  708  is shown being coupled to the base clamp  1120  and the nerve mapping tool  710  being coupled to the top clamp  1130 , in some embodiments, both the array  708  and the nerve mapping tool  710  can be coupled to the base clamp  1120  or to the top clamp  1130 . 
     In some embodiments, the base clamp  1120  can include a core  1124  for coupling to the surgical devices, e.g., the shaft component. The core  1124  can be overmolded and/or made of a durable material, e.g., metal, plastic, polymer, and so forth, that is configured to promote a more rigid connection with surgical devices received therein. 
     The core  1124  can include one or more bores  1126  extending therethrough that are adapted to receive surgical devices therein, though, in some embodiments, the core  1124  can be received within the surgical devices. The core  1124  can prevent surgical devices from moving or otherwise flexing relative to the locking handle  1102  to ensure that dimensional accuracy is maintained with the locking handle  1102 . In some embodiments, the core can overlap with one or more of the ports  1122 ,  1132  to further stabilize the surgical devices coupled to the multi-tool  1100 . For example, as shown, the core  1124  can extend along the port  1122  to receive the navigation array  708  within the base clamp  1120 . Reinforcing the coupling of the navigation array  708  with the core  1124  can decrease and/or eliminate movement of the array  708  relative to the base clamp  1120 , thereby improving navigational accuracy. 
     The core  1124  can include two bores  1126   a ,  1126   b , though, in some embodiments, the core can include one or three or more bores. The bores  1126   a ,  1126   b  can be positioned substantially perpendicular to one another, as shown, though other orientations of the bores is possible, e.g., parallel or at an oblique angle. The bores  1126   a ,  1126   b  can be in communication with one another such that surgical devices disposed therein can interact with one another, e.g., establish an electrical connection, as discussed further below. The core  1124  can be disposed substantially in the base clamp  1120 , as shown, though, in some embodiments, the bore  1126   a  can extend through the base clamp  1120  and the top clamp  1130  to allow surgical devices to extend through both portions of the locking handle  1102  to ensure greater stability of the shaft component  707  within the multi-tool  1100 . In some embodiments, the bores  1126   a ,  1126   b  can be shaped so as to restrict the surgical devices, e.g., the shaft component and/or the navigation array, to a single orientation to promote navigational accuracy and establish a defined frame of reference between devices. 
     The top clamp  1130  can extend proximally from the base clamp  1120 . In some embodiments, the top clamp  1130  can be juxtaposed with the base clamp  1120  such that the top clamp  130  moves freely relative to the base clamp  1120 . The top clamp  1130  can include one or more ports  1132  therein for coupling to surgical devices. As shown, the port  1132  can include a connecting member  1134  for coupling the nerve mapping tool  710  thereto, though, in some embodiments, other surgical devices, e.g., a navigation array, an imaging machine, and so forth can be coupled thereto. The port  1132  can extend into an opposite direction of the bore  1126   b  of the base clamp  1120  so as not to clutter the surgical site with devices, as shown, though, in some embodiments, the port  1132  can extend in the same direction as the bore  1126   b.    
       FIGS.  104 - 105    illustrate an embodiment of a shaft component  1107  that can be used with the locking handle  1102 . The shaft component  1107  can be received in one or more of the base clamp  1120  and the top clamp  1130  to secure the shaft  1107  to the locking handle  1102 . As discussed above, the shaft component  1107  can include an elongate body  1109  having a solid inner core, though, in some embodiments, the elongate body can be hollow. The shaft component  1107  can have a generally cylindrical shape as shown, though the shaft component  1107  can be circular, triangular, pyramidal, and so forth. In some embodiments, a portion of the elongate body  1109  can include grooves or annular rings  1115  thereon to facilitate grasping of the body  1109  by a user. As shown, the grooves  1115  can be annular indentations formed in the elongate body  1109 , though, in some embodiments, roughened surfaces or Velcro adhesives can be used to enhance grip of the shaft component  1107  and minimize the risk of slippage, which can cause significant structural damage in the surgical site. 
     The elongate body  1109  can extend from a proximal handle  1114  to a distal tip  1116 . The elongate body  1109  can include a dielectric coating on an exterior surface thereof adapted to insulate the elongate body  1109  from electrical current. As discussed above, the distal tip  1116  can include an uncoated material thereon such that the distal tip  1116  can conduct electrical current to tissue when docked therein. In some embodiments, the elongate body  1109  can be made of an insulating material, e.g., plastic, polyurethane, glass, and so forth, to insulate and/or dampen electrical current passing therethrough. 
       FIG.  105    illustrates the proximal handle  1114  in greater detail. As shown, the proximal handle  1114  can include a locking groove  1116  thereon. The locking groove  1116  can include one or more indentations to retain a position of the shaft component  1107  within the locking handle  1102 . For example, the locking groove  1116  can extend around a perimeter of the proximal handle  1114  to form a space for receiving retention features (not shown) of the locking handle  1102 . The proximal handle  1114  can be advanced through the locking handle  1102  until the retention feature engages the locking groove  1116  to prevent further advancement of the shaft component  1107 . The locking groove  1116  can be located distal to a proximal-most end of the locking handle  1102 , as shown, though, in some embodiments, the locking groove  1116  can be disposed at the proximal-most end of the locking handle  1108 . In some embodiments, the locking groove  1116  can be made of an uncoated material to facilitate electrical contact. The uncoated material can be the same material as that of the distal tip  1116  of the shaft component  1107 , though the type of uncoated material can differ. 
     The proximal handle  1114  can include one or more flats  1118  on a surface thereof. The flats  1118  can provide indexing and torque transmission when the shaft component  1107  is disposed in the locking handle  1102 . The flats  1118  can extend from the proximal-most end of the proximal handle to a shoulder  1119 , as shown. In some embodiments, the shoulder  1119  can abut one or more components of the locking handle  1102  to prevent further proximal advancement of the shaft component  1107  therethrough. In some embodiments, the retention features can abut a surface of the shoulder  1119  to set a position of the shaft component  1107  within the locking handle  1102 . 
       FIGS.  106 A- 106 B  illustrate a locking mechanism of the locking handle  1102  that is configured to lock the shaft component  1107  to a surgical device that passes through the locking handle  1102 . For example, the base clamp  1120  and the top clamp  1130  can rotate relative to one another to move the locking handle  1102  from the open position to the closed position to secure the shaft component  1107  therein. As shown in  FIG.  106 A , the base clamp  1120  and the top clamp  1130  can be disposed substantially perpendicular to one another in the open position, though, in some embodiments, the base clamp  1120  and the top clamp  1130  can be aligned or at an oblique angle with respect to one another in the open position. 
     In some embodiments, the top clamp  1130  can also include a channel  1136  therein. The channel  1136  can be in communication with the base clamp  1120  such that the surgical device, e.g., the shaft component  1107 , disposed in the locking handle  1102  can be advanced into and/or through the top clamp  1130 . As shown, the channel  1136  can be substantially rectangular such that the proximal handle  1114  of the shaft component  1007  disposed therein can be flush therewith, though, in some embodiments, the opening can be circular, cylindrical, triangular, pyramidal, and so forth. 
     In use, the shaft component  1107  can be advanced or slid proximally through the channel  1136  such that the shaft component  1107  protrudes proximally through the channel  1136  in the top clamp  1130 , though, in some embodiments, the shaft component can be advanced or slid distally through the opening in the top clamp  1130 . The shaft component  1107  can advance through one or more of the base clamp  1120  and the top clamp  1130  until the retention features of the locking handle  1102  engage the locking groove  1116  to fix a position of the shaft component  1107  with respect to the locking handle  1102 . To move the locking handle  1102  to the closed position lock the position of the shaft component  1107  therein, the top clamp  1130  can rotate a quarter turn, e.g., approximately 90 degrees, with respect to the base clamp such that the base clamp  1120  and the top clamp  1130  are aligned, as shown in  FIG.  106 B . As shown, the top clamp  1130  can rotate in a first direction, e.g., counterclockwise, to lock the locking handle  1102 , though in some embodiments, clockwise rotation of the top clamp  1130 , or, alternatively, clockwise or counterclockwise rotation of the base clamp  1120  can lock the locking handle  1102 . During rotation of the clamps, the retention features of the locking handle travel through the locking groove  1116  until the retention features disengage from the locking groove  1116  to abut an outer wall of the shaft component  1107 . When the retention features abut the wall, the shaft component  1107  is prevented from translating or rotating relative to the clamps  1120 ,  1130 , thereby locking the shaft component  1107  to the locking handle  1102 . In some embodiments, once the multi-tool  1100  is in the locked position, an electrical connection can be established between surgical devices using a washer (not shown) disposed within the locking handle. The washer can include a throughhole having a pin disposed therein for establishing an electrical connection between devices. 
     To disengage the shaft component  1107  from the multi-tool  1100 , the top clamp  1130  can be rotated in a second, opposite direction relative to the base clamp  1120  to return the locking handle  1102  to the open position. Once in the open position, the shaft component  1107  can move relative to the locking handle  1102  or be removed from the locking handle  1102  to allow introduction of other surgical devices through the locking handle  1102 . 
       FIG.  107    illustrates an alternate embodiment of a multi-tool  1200 . Except as indicated below and as will be readily appreciated by one having ordinary skill in the art, the structure and function of the multi-tool is substantially the same as that of the embodiments of the multi-tool  700 ,  800 ,  900 ,  1000 ,  1100  described above, and therefore a detailed description is omitted here for the sake of brevity. 
     The multi-tool  1200  can include a cap  1202  coupled thereto. As shown, the cap  1202  can include a knob  1230  instead of or in addition to the top clamp described above. The knob  1230  can be positioned proximal to a base  1220 , as shown, to couple the shaft component  1107  to the cap  1202 . While not shown, various configurations of these features can be used. For example, the knob  1230  can be disposed distal to the base  1220  to fix a position of, and/or lock, the shaft component  1107  within the multi-tool  1200 . By way of further example, the shaft component  1107  can protrude proximally from the base  1220  to allow the knob  1230  to lie along a surface of the base  1220  to engage the shaft component  1107 . The knob  1230  can be secured to the base  1220  using one or more retention pins  1240 , as shown. 
       FIGS.  108 - 109    illustrate the cap  1202  of the multi-tool  1200  in greater detail. The base  1220  can include a receiving orifice  1250  therein. The receiving orifice  1250  can be formed as a recess in a surface of the base  1220  to couple one or more components of the multi-tool  1200  to the cap. For example, the receiving orifice  1250  can be formed in a proximal surface  1220   p  of the base  1220  so as to form an indentation in the proximal surface  1220   p  thereof. As shown, the knob  1230  can be disposed in the indentation formed by the receiving orifice  1250  during assembly of the multi-tool  1200 . In some embodiments, the receiving orifice  1250  can be shaped such that the knob  1230  can be placed flush with the wall of the orifice  1250 , though, in some embodiments, the shape of the indentation formed by the receiving orifice  1250  can be rectangular, square, triangular, and so forth to create one or more relief areas between the knob  1230  and the base  1220 . In some embodiments, the receiving orifice  1250  can include one or more abutment surfaces  1252  for selectively engaging with the knob, as described further below. 
     The base  1220  can include one or more ports  1222  extending therethrough. The ports  1222  are configured to receive surgical devices, e.g., the navigation array  708 , the nerve mapping tool  710 , and so forth, therein for coupling to the multi-tool  1200 . 
     As shown, and as discussed with respect to the embodiments above, each port  1222  can include a core or connector  1224  for reinforcing the coupling of surgical instruments to the base  1220  and the multi-tool  1200 . The connectors  1224  can be integratedly coupled to the base  1220  such that the connectors  1224  cannot be separated from the base, though, in some embodiments, the connectors  1224  can be removably coupled to the handle. The connectors  1224  can include a generally tubular central portion defined by a sidewall circumscribing a bore  1226 . The bore  1226  can define a diameter D 1  through which instruments, implants, or other objects can be inserted. The bore  1226  can extend along a central longitudinal axis L of the connector  1224  from a proximal end  1224   p  to a distal end  1224   d . As shown, the central longitudinal axis L can be generally perpendicular to the shaft component  707 , though, in some embodiments, the axes can be aligned or obliquely angled with respect to one another. 
     The base  1220  can include a channel  1227  therein. The channel  1227  can be configured to allow surgical devices, e.g., the shaft component  1107  to be inserted therethrough. As shown, the ports  1222  and/or the core  1224  can be in communication with the channel to allow surgical devices inserted through the ports to interface with the shaft component  707 . The channel  1227  can be defined by a sidewall  1228  circumscribing the channel  1227 . The channel  1227  can extend along a central longitudinal axis A 2  of the base  1220  from the proximal surface  1220  to the distal surface  1220   d . In some embodiments, and as shown, the channel  1227  can terminate in the receiving orifice  1250 . The channel  1227  can define a diameter D through which instruments, implants, or other objects can be inserted. The channel  1227  can be configured to allow either proximal or distal loading of the instruments therethrough. An interior surface of the channel  1227  can be threaded or can include other mating features for cooperating with an instrument inserted therethrough, e.g., the shaft component  1107 , to advance the instrument longitudinally relative to the base  1220 . In some embodiments, the base  1220  can include two or more channels to allow insertion of multiple instruments therethrough. 
     In some embodiments, the channel  1227  can include a stabilizing component  1229 . The stabilizing component can be disposed in the base  1220  to provide a rigid interface between surgical instruments inserted therethrough. For example, the stabilizing component  1229  can be aligned with central longitudinal axis A 2  of the channel  1227  to allow the shaft component  1107  to pass through the stabilizing component  1229 . In some embodiments, the stabilizing component can be fixedly coupled to, or integrally formed with, the base  1220 , though, in some embodiments, the stabilizing component  1220  can be an insert that can be removably coupled to an interior of the base  1220 . 
     As shown, the connectors  1224  can protrude from the stabilizing component  1229  so as to allow the shaft component  1107  disposed within the stabilizing component  1229  to interface with surgical instruments received within the connectors  1224 . For example, the channel  1227  and the bores  1226  can be in communication with one another such that instruments inserted through the bores  1226  can interface with, e.g., establish an electrical connection, surgical devices disposed in the channel  1227 . For example, the two connectors  1224  shown in  FIG.  109    can receive the navigation array  708  and the nerve mapping tool  710 , as described above, to allow one or more of the navigation array  708 , the nerve mapping tool  710 , and/or the shaft component  1107  to electrically communicate. In some embodiments, the base  1220  can include one, or three or more connectors  1224  extending therethrough. 
     As shown in  FIG.  109   , the base  1220  can receive a retention pin or a cross pin  1240  for coupling the knob thereto. For example, the base  1220  can include one or more openings  1242  in a surface thereof that are configured to receive the retention pins  1240  therethrough. The retention pin  1240  can couple the knob  1130  to the base  1120  while allowing the knob  1130  to rotate relative therewith. The retention pin  1240  can travel within pin slots or paths formed in the knob, as described further below. 
       FIGS.  110 A- 110 B  illustrate the knob  1230  in greater detail. The knob  1230  can include a generally rounded or ring-shaped body  1232  defined by a sidewall  1234  having a channel  1237 . The channel  1237  can extend along an axis A 3  from a proximal end  1230   p  of the knob  1230  to a distal end  1230   d  of the knob  1230 . In some embodiments, the channel  1237  can correspond with a shape of an instrument inserted therethrough. In some embodiments, the shape of the channel  1237  can vary across a length of the channel. For example, the channel  1237  at the distal end  1230   d , as shown in  FIG.  110 A , can include a rectangular shape while the channel  1237  at the proximal end  1230   p , as shown in  FIG.  110 B , can include a rounded shape. The shape of the channel  1237  at the distal end  1230   d  can allow distal loading and proximal advancement of the shaft component  1107 , while the shape of the channel  1237  at the proximal end  1230   p  can allow proximal loading and distal advancement of the shaft component  1107 . In some embodiments, the shape of the channel  1237  can be independent of the direction of loading and advancement of the shaft component  1107 . 
     The knob  1230  can have a circular shape, as shown, or can have various other shapes, such as oval, oblong, square, rectangular, triangular, and so forth. In some embodiments, as discussed above, the knob  1230  can correspond with a shape of the receiving orifice  1250  in which it is disposed. 
     The knob  1230  can include one or more handles or gripping surfaces  1238  located along the sidewall  1234  thereof. The gripping surfaces  1238  can be in the form of indentations or grooves formed in the exterior of the knob  1230  such that a force that is exerted on the gripping surfaces  1238  can move the knob  1230  between the open position and the closed position, as discussed further below. While the gripping surfaces  1238  are shown as being evenly distributed along a circumference of the knob  1230 , in some embodiments, the gripping surfaces  1238  can extend from the knob  1230  such that a force that is exerted on the gripping surfaces  1238  can move the gripping surfaces  1238  and the knob  1230  between the open and closed positions. 
     The knob  1230  can include a mating tab  1236  extending therefrom. The mating tab  1239  can be a separate component mounted to the knob  1230  or, as shown, can be formed integrally or monolithically with the knob to fixedly couple to the knob  1230  such that a force that is exerted on the knob  1230  can move the mating tab  1236  and the knob as a single unit. The mating tab  1236  can be configured to engage the abutment surfaces  1252  on the receiving orifice  1250  to maintain the rotational position of the knob  1230  relative to the base  1220 , as described further below. 
     The knob  1230  can include a wing tab or projection  1239  extending therefrom. The wing tab  1239  can be a separate component mounted to the knob  1230  or, as shown, can be formed integrally or monolithically with the knob  1230  to fixedly couple to the knob such that a force that is exerted on the knob  1230  can move the wing tab  1239  and the knob as a single unit. In other arrangements, the knob  1230  can include fewer or additional springs and mating tabs. The wing tab  1239  can be configured to flex or bend relative to the knob  1230  to allow the knob to move into and out of engagement with the receiving orifice  1250  when switching between the open position and the closed position, as discussed further below. In some embodiments, the wing tab  1239  can be connected to the knob by a spring (not shown) such as a leaf spring, coil spring, wave spring, non-cantilevered projection, or other bias element that can move the wing tab  1239  between an open configuration and a closed configuration. 
     The knob  1230  can include one or more pin paths  1241  therein. The pin paths can be defined as ports formed in the knob  1230  that can receive the retention pin  1240  therethrough. In some embodiments, the pin paths  1241  can be circumferential cut-outs in the knob  1230  that can receive the retention pin  1240  therethrough. The retention pin  1240  can travel through the pin path  1241  as the knob  1230  is rotated relative to the base  1230  to move the multi-tool  1200  between the open and closed positions. In some embodiments, the knob  1230  can have two or more pin paths  1241  therein. 
       FIG.  111 A  illustrates the cap  1202  of the multi-tool  1200  in the open position and  FIG.  111 B  illustrates the cap  1202  of the multi-tool  1200  in the closed position. The knob  1230  can be rotated to move the multi-tool  1200  between (i) an open position in which the shaft component  1107  is free to translate and rotate relative to the cap  1202 , and (ii) a closed position in which the shaft component  1107  is restrained from translating and rotating relative to the cap  1202  to limit or prevent relative movement of the shaft component  1107 . 
     The base  1220  and the knob  1230  can include one or more indicators that show whether the multi-tool  1200  is in the open position or in the closed position. For example, as shown in  FIG.  111 A , the base  1220  and/or the knob  1230  can include labels or images thereon to indicate the position of the multi-tool  1200 . The base  1220  can include a first image  1260  of a padlock in a closed position that can be aligned with a second image of arrows  1262  on the knob  1230 . While a set of arrows  1262  is shown, a circle, or another mark that can align with, or point to, the padlock image on the base  1220  can be used. When the arrow  1262  points away from the padlock image  1260 , the multi-tool  1200  is not in the closed position, e.g., in the open position. The multi-tool  1200  can include additional indicators for communicating the position of the multi-tool  1200 . In some embodiments, the base  1220  can include an image of a padlock in an unlocked or open position that can be aligned with the arrows on the cap  1230  to indicate that the multi-tool is in the open position. It will be appreciated other images can be used instead or in addition, such as text labels, e.g., that read “open” and “closed,” or “unlocked” and “locked,” respectively, other drawings, and the like. 
     Additional features of the relative arrangement of the base  1220  and the knob  1230  can suggest that the multi-tool  1200  is in open position. For example, as shown in  FIG.  111 A , the wing tab  1239  can protrude at an angle from the knob  1230 , which can indicate that the knob  1230  is in the open position. The arrows  1262  on the knob  1230  do not point to the indicator  1260  on the base  1260 , which can also indicate that the multi-tool is in the open position. In some embodiments, the mating tab  1236  can be disposed outside of any relief areas in the receiving orifice  1250 , which can also indicate that the multi-tool  1200  is in the open position. 
     The knob  1230  can be rotatable about the axis A 3  to move between an open position and a closed position. As shown in  FIG.  111 B , the knob  1230  can be rotated in a counterclockwise direction, when viewed from a proximal perspective, to move the knob  1230  into the closed position, though, in other embodiments, the direction of rotation can be reversed. As a rotational force is imparted onto the knob  1230 , the one or more retention pins  1240  can travel from a first end of the pin path  1241  towards a second end of the pin path  1241 . As the retention pins  1240  approach the second end of the pin path  1241 , the retention pins  1240  can engage the flats  1118  of the shaft component  1107 , thereby preventing further rotation of the knob  1230 . During rotation of the knob  1230 , the wing tab  1239  can enter the relief area in the receiving orifice  1250  and abut the abutment surface  1252  in the receiving orifice  1250 . As the knob  1230  rotates further, the abutment surface  1252  can move or snap the wing tab  1239  towards the knob  1230  such that the wing tab  1239  is moved to a position that is flush with the knob  1230  to prevent further rotation of the knob. Further rotation of the knob  1230  can also be prevented by the pin path  1241 , which can restrict further travel of the retention pin  1240  therein. 
       FIG.  111 B  illustrates the multi-tool  1200  with the knob  1230  in the closed position. As shown, the wing tab  1239  and the mating tab  1236  can be disposed in the relief areas of the receiving orifice  1250  to prevent the knob  1230  from rotating with respect to the base  1220 . The indicator  1262  on the knob  1230  can be aligned with the indicator  1262  on the knob  1230 . That is, the arrows  1262  on the knob  1230  can point to the first image  1260  to suggest that multi-tool  1200  is in the closed position. To switch the multi-tool  1200  to the open position, the knob  1230  can be rotated in a second, opposite direction, e.g., clockwise, to release the wing tab  1239  from the receiving orifice  1250 . As a rotational force is imparted onto the knob  1230  into the second direction, the retention pins  1240  can disengage from the flats  1118  of the shaft component  1107  and travel from the second end of the pin path  1241  towards the first end of the pin path  1241 . As the knob  1230  continues to rotate, the wing tab  1239  exists the relief area to pivot the wing tab  1239  away from the knob  1230  to return the multi-tool  1200  to the open position. Once in the open position, the shaft component  1107  is free to translate and/or rotate within the multi-tool  1200 . 
       FIGS.  112 - 115    illustrates an alternate embodiment of a multi-tool  1300 . Except as indicated below and as will be readily appreciated by one having ordinary skill in the art, the structure and function of the multi-tool is substantially the same as that of the embodiments of the multi-tool  700 ,  800 ,  900 ,  1000 ,  1100 ,  1200  described above, and therefore a detailed description is omitted here for the sake of brevity. 
     The multi-tool  1300  can include quick-connect features that enable easy toggling between components of the tool, e.g., the shaft component and the cap. As shown, the multi-tool  1300  can include a clamp  1302  in lieu of, or in addition to, the cap described with respect to the embodiments above. The clamp  1302  can be defined by a sidewall  1304  circumscribing a channel  1305  that extends therethrough. The channel  1305  can be configured to receive at least a portion of another tool or instrument therein. The channel  1305  can extend along a central longitudinal axis A 4  that aligns with the central longitudinal axis A 1  of the shaft component  707 . The channel  1305  can define a diameter D 2  through which instruments, e.g., the shaft component  707 , can be inserted. The clamp  1302  can further include one or more arms  1306  that protrude from the sidewall  1304  for coupling the navigation array  708  and the nerve mapping tool  710  thereto. 
     The clamp  1302  is shown in greater detail in  FIGS.  113 A- 113 B . The clamp  1302  can include a slider  1312  that translates along a surface thereof. The slider  1312  can be configured to operate as a one directional clamp to lock an axial position of the shaft component  707  to the clamp  1302 . For example, the slider  1312  can translate between a first position in which the clamp  1302  is in an open position to allow the shaft component  1302  to rotate and/or translate freely relative to the multi-tool  1300 , and a second position in which the claim  1302  is in a closed position which prevents the shaft component  707  from rotating and/or translating relative to the multi-tool  1300 . 
     The clamp  1302  can include one or more tracks or slots  1314  on a surface thereof. The tracks  1314  can be formed as indentations or throughholes in the sidewall  1304  of the clamp. For example, as shown, in  FIG.  115   , the clamp can include a first track  1314   a  and a second track  1314   b  formed therein. The first track  1314   a  can be positioned substantially parallel to a length of the clamp  1302  and the second track  1314   b  can be angled with respect to the axis of the clamp  1302  and/or a shaft component inserted therethrough, as shown and described further below. The tracks  1314   a ,  1314   b  can extend substantially through an entire width of the clamp, e.g., from arm to arm, as shown, though, in some embodiments, the tracks can encompass narrower sections of the sidewall. 
     The slider  1312  can be disposed in the track  1314   a ,  1314   b  and move relative thereto to lock and unlock the shaft component  707  relative to the clamp  1302 . As shown, the slider  1312  can include a length that is smaller than a length of the tracks  1314   a ,  1314   b  such that the slider  1312  can move proximally and distally within the tracks  1314   a ,  1314   b . The slider  1312  can extend through the tracks  1214   a ,  1314   b  to protrude from opposite sidewalls  1304  of the clamp  1302 , though, in some embodiments, the slider  1312  can terminate within the tracks  1314   a ,  1314   b  such that the slider  1312  protrudes from only one side of the clamp  1302 . 
     The slider  1312  can include one or more gripping surfaces  1316  on a surface thereof. The gripping surfaces  1316  can include grooves or ridges in a surface thereof to provide friction when held by a user. As shown, the gripping surfaces  1316  can be located on opposite sides of the slider  1312 , though, in some embodiments, the gripping surfaces can be located on a single side of the slider  1312 . When a force is exerted on the gripping surfaces  1316 , the gripping surfaces  1316  and the slider can move as a single unit. 
     The slider  1312  can include one or more orifices or holders  1318  formed therein. The holders  1318  can be defined in an interior surface of the slider  1312  to receive one or more gripping pins  1320  therein, as described further below. The holders  1318  can have a cylindrical shape, as shown, or can have various other shapes, such as oval, oblong, square, rectangular, triangular, and so forth. As shown, the slider  1312  can include one or more sets of holders  1318  that lie along the length of the slider. As shown, two sets of holders  1318  can be distributed on opposite sides of the slider  1312  such that the shaft component  707  is disposed between the holders  1318 . The holders  1318  can lie along a common axis, though, as shown in  FIG.  114   , one or more holders  1318  in each set can be biased relative to the remaining holders to promote engagement with surgical devices disposed within the clamp, as described further below. 
     The gripping pins  320  can extend interiorly from the holders  1318 . The gripping pins  1320  can extend along an axis A 5  that is substantially perpendicular to the axis A 1  of the shaft component  707 . While each holder  1318  can include gripping pins  1320  therein, in some embodiments, as shown in  FIG.  115   , one or more holders  1318  can be devoid of pins  1320 . The gripping pins  1320  can be fixedly coupled to the holders  1318  such that a force that is exerted on the gripping pins  1320  can move the gripping pins  1320  and the slider  1312  as a single unit. In some embodiments, the gripping pins  1320  can be formed integrally or monolithically with the holders, though, in some embodiments, the gripping pins  1320  can be removably received within the holders  1318 . As shown, the gripping pins  1320  can have a cylindrical shape, as shown, or can have various other shapes, such as oval, oblong, square, rectangular, triangular, and so forth that correspond to the shape of the holder  1318  in which the pin is disposed. 
     The clamp  1302  can include one or more bias elements or springs  1322  coupled thereto. The springs  1322  can extend distally from a proximal end  1302   p  of the clamp  1302  to the holder  1318  and/or gripping pins  1320  disposed in the slider  1312  to create separation between the slider  1312  and the proximal end  1302   p  of the clamp  1302 . A force exerted by the springs  1322  can bias the slider  1312  distally such that the slider  1312  is spaced apart from the proximal end  1302   p  of the clamp  1302  by a length of the spring  1322 . The springs  1322  can bias the gripping pins  1320  towards one another such that a distance between the biased gripping pins is smaller than a distance between unbiased gripping pins. While two biased gripping pins  1320  are shown, in some embodiments, one or three or more gripping pins  1320  can be biased by springs  1322 . The gripping pins  1320  can be configured to engage with instruments, implants, or other objects, e.g., the shaft component  707 , received therebetween to secure their position within the clamp  1302 . 
     In use, the gripping pins  1320  can ride within the tracks  1314   a ,  1314   b  formed in the sidewall  1304  of the clamp  1302  to allow proximal-distal translation of the pins  1320  and the slider  1312  associated therewith. For example, as shown, the gripping pins  1320  can ride in the first track  1314   a  and the biased gripping pins can ride in the second track  1314   b . When assembling the multi-tool, the shaft component  707  can be inserted distally and advanced proximally through the clamp  1302 . Continued proximal advancement of the shaft component  707  can exert a force on the biased gripping pins  1320  to counter the biasing force exerted by the springs  1322  to move the gripping pins  1320  proximally. Proximal movement of the gripping pins  1320  can contract the length of the springs  1322  to move the gripping pins  1320  proximally in the second track  1314   b  at an angle to the axis of the shaft component  707 , thereby separating the gripping pins  1320 . Proximal movement of the gripping pins  1320  can also move the slider  1312  proximally. 
     The gripping pins  1320  and the slider  1312  can continue to travel proximally in the second track  1314   b  until the distance between the gripping pins  1320  is substantially equal to a diameter D 3  of the shaft component, as shown in  FIG.  114   . In this configuration, the gripping pins  1320  stop moving proximally and the pins  1320  are biased distally by the springs  1322 . The bias force allows the gripping pins  1320  to engage the shaft component  707  to exert a clamping force thereon prevent further translation and/or rotation of the shaft component  707  relative to the clamp  1302 . Any attempt to pull the proximal handle  714  of the shaft component  707  out of the clamp reinforces the clamping force exerted by the gripping pins  1320  on the shaft component  707 . 
     Once secured, an electrical connection can be established between the shaft component  707  and one or more of the navigation array  708  and the nerve mapping tool  710 . For example, in the multi-tool  1300  shown in  FIG.  115   , current can pass through contact between the gripping pins  1320  and the shaft component  707 , through the springs  1322 , and into the proximal end  1302   p  of the clamp  1302  that is attached to the nerve mapping tool  710 . 
     To change a position and/or disengage the shaft component  707  from the clamp  1302 , a proximal force can be exerted on the slider  1312 , such as with the hand of a user. Exerting a proximal force on the slider  1312  to counter the distally biasing force of the bias element  1322  can proximally advance the slider  1312  to release the gripping pins  1320  from the shaft component  707 . Once the gripping pins  1320  are released, the position of the shaft component  707  can be changed and the shaft component  707  can be disengaged from the clamp  1302 . The clamp  1302  can then be coupled to another instrument, e.g., a second shaft component. 
       FIGS.  116 A- 116 B  illustrate an alternate embodiment of a multi-tool  1400  quick-connect feature. Except as indicated below and as will be readily appreciated by one having ordinary skill in the art, the structure and function of the multi-tool is substantially the same as that of the embodiments of the multi-tool  700 ,  800 ,  900 ,  1000 ,  1100 ,  1200 ,  1300  described above, and therefore a detailed description is omitted here for the sake of brevity. 
     As shown, the multi-tool  1400  can include a cap  1402  configured to receive the shaft component  707  therein. A stopper  1404  can extend distally from the cap  1402  that can be used in lieu of, or in addition to, the slider  1312  having gripping pins  1320  to secure the shaft component  707  to the cap  1402 . For example, the stopper  1404  can include a sidewall  1406  that defines an opening  1408  therein configured to receive the shaft component  707  therethrough. 
     The proximal handle  714  of the shaft component  707  can be received through the opening  1408  in the stopper  1404  and advanced proximally therethrough. The stopper  1404  can include a retention mechanism (not shown) that can engage the grooves  715  in the shaft component  707  to prevent further translation and/or rotation of the shaft component  707  relative to the cap  1402 . To deploy the retention mechanism, the stopper  1404  can be advanced distally such that the retention mechanism snaps into the groove  715 . To change a position and/or disengage the shaft component  707  from the stopper  1404 , the stopper  1404  can be advanced proximally, such as with the hand of a user, to disengage the stopper  1404  from the groove of the shaft component  707  to release the shaft component  707  therefrom. 
       FIGS.  117 - 118    illustrate one method of using an embodiment of the multi-tools disclosed herein for docking a shaft component in target tissue to insert an access port for performing a procedure, e.g., a posterior lumbar surgery. Except as indicated below and will be readily appreciated by one having ordinary skill in the art, the steps of the described method can be performed in various sequences, and one or more steps can be omitted or added. A detailed description of every sequence of steps and of every embodiment is omitted here for the sake of brevity. While the method is discussed with respect a given set of embodiments, it will be appreciated that any of the embodiments discussed herein can be used to perform the steps below. 
     In use, a bone anchor or a contra-lateral screw can be implanted in a body of a patient, e.g., in a pedicle or in the lumber spine of the patient. In some embodiments, the bone anchor can be inserted with a navigation array to calibrate the array to the system and pre-operative and post-operative images of the patient. Calibration can include analysis of position and/or orientation of the bone anchor within the dimensions of the patient. Using the location of the array and its position within the patient, a target site for insertion of an access port can be determined. 
     To insert the access port, an incision can be made at the target site  1 . Once the incision is sufficiently sized, the shaft component  707  of the multi-tool  700  can be inserted into the target site  1 . The shaft component  707  can be inserted under guidance from one or more of the navigation array  708  and the nerve mapping tool  710  to ensure precision of placement of the shaft component  707  and that surrounding tissues, nerves, and/or bones are not damaged during insertion. The distal tip  716  of the shaft component  707  can be configured to slide along bone while also being sharp such that the distal tip  716  can dock to the bone when impacted with sufficient force. Force that is sufficient to dock the shaft component  707  to the target site  1  can include finger pressure or via manual force by a user, though, in some embodiments, the shaft component can be tapped  707  into the bone using a mallet, hammer, or the like. As shown in  FIG.  117   , in some embodiments, the distal tip  716  can sweep across a bone surface until the tip  716  reaches the target site  1 , at which point the tip  716  can advance into the target site  1  while avoiding the exiting nerve root. 
     Once the shaft component  707  is docked, the cap  702  of the multi-tool  700  can be disassembled from the shaft component in the variety of ways described above, while leaving the shaft component  707  docked in the target site  1 . The target site  1  can then be enlarged by serial dilation to allow an access port to be received therein. In serial dilation, one or more cannulated dilators can be inserted sequentially into the target site  1  over the shaft component  707  to increase the opening in the target site  1 . For example, a series of cannulated dilators  2 ,  4 ,  6 , each having a diameter that is larger than the shaft component  707 , and each previous dilator, can slide over the shaft component  707  and the previously-inserted dilator into the target site  1 . 
     The cannulated dilators  2 ,  4 ,  6  can include a generally tubular shape having a sidewall that circumscribes a channel  3 ,  5 ,  7  that extends therethrough. The channels  3 ,  5 ,  7  can extend parallel to the central longitudinal axis A 1  of the shaft component  707  to receive the shaft component  707 , as well as cannulated dilators of smaller diameters, therethrough. As shown, the first dilator  2  can be inserted over the shaft component  707  such that the shaft component passes through the channel  3 , the second dilator  4  can be inserted over the shaft component  707  and the first dilator  2 , the third dilator  6  can be inserted over the shaft component  707  and the first  2  and second dilators  4 , and so forth. 
     In some embodiments, each of the cannulated dilators  2 ,  4 ,  6  of the series of dilators used in serial dilation can have a different length. For example, as shown, a length L 2  of the first dilator  2  can be longer than a length L 4  of the second dilator  4 , which can be longer than a length L 6  of the third dilator  6 , and so forth. The larger length of the previously-inserted dilator allows the dilator to protrude distally from the subsequently-inserted dilator to allow removal of the previously-inserted dilator from the target site. That is, as shown in  FIG.  118   , the first and second dilators  2 ,  4  protrude distally from the third dilator  6 , allowing for removal of the first and second dilators  2 ,  4  from the target site  1  prior to introduction of a fourth dilator, and/or an access port. 
     Serial dilation can proceed by continuing to add cannulated dilators of increasing diameter into the target site  1  until the opening at the target site is sized to receive the access port therein. As shown, three dilators  2 ,  4 ,  6  are inserted into the target site, though in some embodiments, two or fewer, or four or more dilators can be used until the target site is sufficiently dilated to receive the port therein. In some embodiments, the access port can have a length that is smaller than the previously-inserted dilator, e.g., the third dilator  6 , in order to allow the previously-inserted dilator to be removed from the target site  1 . 
       FIG.  119    illustrates an embodiment of an access port  100  that can be inserted into the target site  1 . For example, the access port  100  can be used to create an access path for objects, e.g., devices such as bone anchors, instruments and/or surgical material, e.g., sutures, to be introduced into a surgical site. The access port  100  can include a generally tubular or cylindrical-shaped body defined by a sidewall  102  having a central opening  104 . The opening  104  can extend along an axis A 6  from a proximal end  100   p  of the access port  100  to a distal end of the access port  100   d . In some embodiments, the opening  104  can be shaped to correspond with a shape of an object or an instrument being inserted therethrough. It will be appreciated that the access port  100  can be a cannula, tube, retractor, bladed retractor, dilator, and/or another example of an access device known to one having ordinary skill in the art for creating an access path into a surgical site of a patient. The opening  104  of the access port  100  can have a uniform diameter, though, in some embodiments, the access port  100  can have two or more diameters, as discussed further below. 
     In some embodiments, the central opening  104  of the access port  100  can include multiple channels therein. As shown, the central opening  104  can include a working channel  106  and a camera channel  108 . The working channel  106  can be configured to receive objects and/or instruments therethrough while the camera channel  108  can support a camera being inserted therein to allow users to observe the distal end of the access port  100  and the target site  1 . The working channel  106  and the camera channel  108  can be separated from one another with a wall  110  that passes through an interior portion of the access port  100 , though, in some embodiments, the channels can be in communication with one another to allow objects to pass between the channels. In some embodiments, the working channel  106  and the camera channel  108  can be recesses formed in the proximal end  100   p  of the access port  100 , as shown, though, as shown in  FIG.  122   , one or more of the camera channel  108  and the working channel  106  can protrude proximally from the access port  100  to receive devices, instruments, and/or objects therethrough. 
     The access port  100  disclosed herein can be made from a rigid or a flexible material. Some non-limiting examples of rigid materials can include stainless steel, titanium, nickel, cobalt-chromium, or alloys and combinations thereof, polymers such as PEEK, ceramics, carbon fiber, and so forth. Some non-limiting examples of flexible materials can include rubber, any of a variety of flexible polymers, and so forth. The material can be chosen based on the surgical site, type of surgery, and/or the objects used during the procedure. Rigid materials can provide added support for objects introduced into the surgical site, while flexible materials can be more easily manipulated by a surgeon to increase an amount of space at the surgical site. It will be appreciated that flexible materials that are sufficiently deformable can allow the access port to be removed when intended, without damaging surrounding tissue. 
     The sidewall  102  of the illustrated access port  100  can be smooth to facilitate insertion of the access port with minimal friction. While minimizing damage to surrounding tissue, having a smooth sidewall  102  can make the access port  100  prone to unintended backing out of the patient. In some embodiments, surface structures can be added to the access port  100  to retain the access port within the surgical site and prevent ejection. The surface structures can include screws, pins, serrations, or other features known in the art to increase friction to prevent backing out of a structure from a target site  1 . 
     In some embodiments, the access port  100  can couple to instruments and/or devices to manipulate the orientation of the access port in situ, e.g., adjust a position of the access port. For example, the central opening  104  can include one or more mating features  112  thereon for receiving corresponding mating features of an instrument and/or device. As shown, the mating features  112  can include indentations formed in the proximal end  102   p  of the access port  100 . In some embodiments, the mating features  112  can be protrusions that are received in corresponding mating features of the instruments and/or device coupled to the access port. 
       FIGS.  120 - 122    illustrate an embodiment of a plug or port adjuster  120  that can be coupled to the access port  100  to adjust an orientation of the port. For example, the port adjuster  120  can couple to the proximal end  100   p  of the access port  100  to facilitate one-handed operation and adjustment of the orientation and/or angle of the port. 
     The port adjuster  200  can be defined by a sidewall  202  having a central lumen  204  that extends therethrough. The central lumen  204  can extend along a central longitudinal axis A 7  of the port adjuster  200  from a proximal end  200   p  of the port adjuster  200  to a distal portion  200   d . The central lumen  204  can define a space through which instruments, implants, or other objects can be inserted. For example, the central lumen  204  can define an inner diameter D 4  that extends through the port adjuster  200 . The inner diameter D 4  can be smaller than the diameters of the working channel  106  and/or the camera channel  108  of the access port such that instruments received through the central lumen  204  of the port adjuster  200  can be advanced through the access port  100 . The instruments can be inserted proximally or distally through the central lumen  204 . 
     The distal portion  200   d  of the port adjuster  200  can be configured to be received in the proximal end  100   p  of the access port  100 . For example, the distal portion  200   d  can include a generally cylindrical shaft in which the central lumen  204  passes. The distal portion  200   d  can be sized such that it can be inserted through the central opening  104  in the access port  100 . As shown in  FIG.  121   , the distal portion  200   d  can be received in either of the working channel  106  or the camera channel  108  to couple the port adjuster  200  to the access port  100  without blocking one of the working channel  106  or the camera channel  108 . 
     The proximal end  200   p  of the port adjuster  200  can include a handle  206  or another feature that facilitates gripping of the instrument by the user. The handle  206  can be configured to adjust an angle and/or orientation of the access port  100  prior to, or after, insertion into the target site  1 . For example, the handle  206  can include a bulb or a joystick extending proximally from the distal portion  200   d . The handle  206  can be used similar to a gear shift in a car to manipulate a position of the port. In some embodiments, the port adjuster  200  can position the port into a desired position under guidance from the navigation array  708  and the nerve mapping tool  710 . The handle  206  can include a handle lumen (not shown) therein that is in communication with the central lumen  204  of the distal portion  200   d  such that tools inserted through the central lumen  204  can pass through the handle lumen, and tools inserted through the handle lumen can pass through the central lumen  204 . 
     The handle  206  and the distal portion  200   d  can be separated by an abutment surface or shoulder  300  that is defined by a platform that can rest against the proximal end  100   p  of the access port  100 , as shown in  FIG.  121   . The abutment surface  300  can prevent the adjustment port  200  from advancing too far distally into the central opening  104  of the access port  100 . The abutment surface  300  can wrap around the circumference of the port adjuster  200 , although, in some embodiments, the abutment surface  300  can include a cutout therein so as not to block access to the camera channel  108 , as shown in  FIGS.  121 - 122   . The abutment surface  300  can also include one or more mating features  302  thereon configured to be received in the mating features of the access port  100  to couple the port adjuster  200  to the access port. 
     As shown in  FIG.  122   , the port adjuster  200  can be received in the working channel  106  such that the central axis A 7  of the port adjuster  200  is aligned or coincident with the axis A 6  of the access port  100  to allow instruments, devices, and/or other objects to be advanced therethrough. In some embodiments, the handle  206  can flex and/or bend to change the position of the access port  100  to increase the ease with which tools are inserted through the access port  100  and/or to change the position of a camera disposed through the working channel  106  in the target site  1 . For example, in some embodiments, the handle  206  can be configured to move in all six degrees of freedom (surge, heave, sway, yaw, pitch, and roll) to adjust an angle of the access port  100  and/or to rotate the port to change camera position. Adjustment of the access port  100  can occur prior to passing tools through the central opening  104  of the access port and the port adjuster  200  or once the tools are disposed therein to reposition the port. In some embodiments, the port adjuster  200  can be coupled to the access port  100  prior to insertion of the access port  100  into the target site  1  to provide better control during insertion of the access port over the cannulated dilators into the target site. 
       FIGS.  123 - 125    illustrate an embodiment in which the multi-tool  700  can be used to navigate the access port  100 . For example, the multi-tool  700  can be inserted through the port adjuster  200  and the access port  100  to position the access port  100  in the target site  1 . As shown in  FIG.  123   , the shaft component  707  of the multi-tool  700  can be received through the coincident lumens of the port adjuster  200  and the working channel  106  of the access port  100  to enter the target site  1 . In such a configuration, the shaft component  707  can advance distally through the access port  100  such that the distal tip  716  extends distally from the access port  100 , as shown in  FIGS.  124 - 125   . The shaft component  707  can then contact tissue at the target site  1  distal of the access port  100 . The shaft component  707  can be docked to the target site  1  in this configuration. Inserting the shaft component  707  through the working channel  106  can allow for indirect navigation of the access port  100  without requiring a permanently affixed navigation array to be coupled thereto, which can be bulky and interfere with the procedure. A camera or another visualization device can be inserted through the camera channel  108  and advanced into the target site  1  to visualize the distal tip  716  of the shaft component  707  and assess the trajectory and/or path of the shaft component  707  into the target site  1 . 
     In some embodiments, the navigation array  708  and the nerve mapping tool  710  can be attached to the shaft component  707 , as described in the embodiments above, in addition to the camera in the camera channel  108  to ensure precision of the placement of the shaft component  707  in the target site  1 . 
     It should be noted that any ordering of method steps expressed or implied in the description above or in the accompanying drawings is not to be construed as limiting the disclosed methods to performing the steps in that order. Rather, the various steps of each of the methods disclosed herein can be performed in any of a variety of sequences. In addition, as the described methods are merely exemplary embodiments, various other methods that include additional steps or include fewer steps are also within the scope of the present disclosure. 
     The instruments disclosed herein can be constructed from any of a variety of known materials. Exemplary materials include those which are suitable for use in surgical applications, including metals such as stainless steel, titanium, nickel, cobalt-chromium, or alloys and combinations thereof, polymers such as PEEK, ceramics, carbon fiber, and so forth. The various components of the instruments disclosed herein can be rigid or flexible. One or more components or portions of the instrument can be formed from a radiopaque material to facilitate visualization under fluoroscopy and other imaging techniques, or from a radiolucent material so as not to interfere with visualization of other structures. Exemplary radiolucent materials include carbon fiber and high-strength polymers. 
     The instruments and methods disclosed herein can be used in minimally-invasive surgery and/or open surgery. While the instruments and methods disclosed herein are generally described in the context of spinal surgery on a human patient, it will be appreciated that the methods and instruments disclosed herein can be used in any type of surgery on a human or animal subject, in non-surgical applications, on non-living objects, and so forth. 
     Although specific embodiments are described above, it should be understood that numerous changes may be made within the spirit and scope of the concepts described.