Abstract:
Technology disclosed herein relates to retractors and methods of use for surgical procedures, and in particular, spinal surgical procedures. In one embodiment, a surgical retractor includes a pair of pivotable armatures and a translatable armature. A body for supporting the armatures is provided, with a handle connected thereto. The handle includes a first rotary actuator, wherein a rotation of the first rotary actuator moves the pair of pivotable armatures in opposite arcuate directions, and a second rotary actuator, wherein a rotation of the second rotary actuator translates the translatable armature in a linear direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 15/372,426, filed Dec. 8, 2016, which is a continuation of U.S. patent application Ser. No. 15/183,380, filed Jun. 15, 2016, which is a continuation of U.S. patent application Ser. No. 13/601,887, filed Aug. 31, 2012, now issued as U.S. Pat. No. 9,572,560, which claims priority to and the benefit of U.S. Provisional Application Ser. No. 61/529,756, filed Aug. 31, 2011, entitled, “Lateral Retractor System and Methods of Use,” the disclosure of which is hereby incorporated by reference herein in its entirety. 
     
    
     INTRODUCTION 
       [0002]    Current retractor systems for lateral spine surgical procedures create an opening through the side of a patient, and may pass through the psoas muscle. Improved systems are desirable with respect to at least ease of use, stability, visibility and robustness. 
       SUMMARY 
       [0003]    In one aspect, the technology relates to retractors and methods of use for surgical procedures, and in particular, spinal surgical procedures. In one embodiment, a surgical retractor includes a pair of pivotable armatures and a translatable armature. A body for supporting the armatures is provided, with a handle connected thereto. The handle includes a first rotary actuator, wherein a rotation of the first rotary actuator moves the pair of pivotable armatures in opposite arcuate directions, and a second rotary actuator, wherein a rotation of the second rotary actuator translates the translatable armature in a linear direction. 
         [0004]    In one embodiment, a method of creating a distraction corridor to a surgical site is disclosed. The method includes providing a surgical retractor having a handle comprising two rotatable elements, and a plurality of blades moveable relative to the handle. The method includes inserting the plurality of blades simultaneously into a body tissue; actuating a first of the two rotatable elements so as to separate at least two of the plurality of blades; and actuating a second of the two rotatable elements so as to translate at least one of the plurality of blades. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    There are shown in the drawings, embodiments which are presently preferred, it being understood, however, that the technology is not limited to the precise arrangements and instrumentalities shown. 
           [0006]      FIG. 1  depicts a perspective view of a retractor device in an open position. 
           [0007]      FIG. 2  depicts a partial enlarged top view of a retractor device with a top cover removed 
           [0008]      FIG. 3A  depicts a top view of a retractor device in a closed position. 
           [0009]      FIG. 3B  depicts a top view of a retractor device in an open position. 
           [0010]      FIG. 4  depicts a partial exploded perspective view of a handle of a retractor device. 
           [0011]      FIGS. 5A-5C  depict enlarged partial perspective views of a locking element in various positions. 
           [0012]      FIGS. 6A-6C  depict enlarged partial views of a blade/arm interface of a retractor device. 
           [0013]      FIG. 7  depicts a side view and enlarged partial side views of a dilator. 
           [0014]      FIGS. 8A and 8B  depict a perspective view of an intradiscal shim, and the intradiscal shim extending from a blade, respectively. 
           [0015]      FIGS. 8C and 8D  depict a perspective view of a widening shim, and the widening shim connected to a blade, respectively. 
           [0016]      FIGS. 8E and 8F  depict a perspective view of a lengthening shim, and the lengthening shim connected to a blade, respectively. 
           [0017]      FIG. 8G  depicts a sectional view of the intradiscal shim and blade of  FIG. 8B . 
           [0018]      FIGS. 8H and 8I  depict a perspective view of a first anchoring shim, and the first anchoring shim connected to a blade, respectively. 
           [0019]      FIGS. 8J and 8K  depict a perspective view of a second anchoring shim, and the second anchoring shim connected to a blade, respectively. 
           [0020]      FIGS. 8L and 8M  depict a perspective view of a third anchoring shim, and the third anchoring shim connected to a blade, respectively. 
           [0021]      FIG. 8N  depicts a perspective view of a fourth anchoring shim connected to a blade. 
           [0022]      FIGS. 9A-9F  depict a method of using a retractor system for a lateral spinal surgical procedure. 
           [0023]      FIG. 9G  depicts a paddle for use with a retractor system. 
           [0024]      FIGS. 10A and 10B  depict a method of using a retractor system. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  depicts a retractor device  100  that includes a main retractor body  126 , a handle  114 , and a plurality of armatures (arms)  102 - 106  with blades  118 - 122  attached thereto. The retractor body  126  includes a number of components that drive the operable elements of the retractor device  100 . The arms  102 - 106  may be opened and closed by rotating actuators  128 ,  130  on the handle  114 . The blades  118 - 122  attached to each arm  102 - 106  are used to form a surgical distraction corridor in a body tissue. This corridor is enlarged as the arms  102 - 106  are opened. These and other elements of the retractor device  100  are described in more detail below. 
         [0026]    In the depicted embodiment, the retractor body  126  includes a top cover plate  108  and a bottom cover plate (not seen in  FIG. 1 ) that limit access to the drive elements located therein. The top cover  108  plate includes one or more slots  116 . In some embodiments, each of the two pivoting arms  102 ,  106  is connected to a guide pin (not seen in  FIG. 1 ). The pin is located within the slot  116 , and restricts movement of the arm  102 ,  106  to which it is connected as the arm  102 ,  106  is opened and closed. In the depicted embodiment, a slot  116  is associated with each of the pivoting arms, with two pins and slots  116  operating together to restrict the movement of arms  102 ,  106 . In other embodiments, only a single slot  116  may be used. In certain embodiments, the slot(s)  116  may be entirely eliminated. Inclusion of the slot  116 , however, helps control the connection between the pivoting arm  102 ,  106  and the retractor body  126 . One or more articulating arm connection points  110 ,  124  may also be located on the top cover  108 . These connection points  110 ,  124  may be used to connect the retractor device  100  to a discrete articulating arm that is connected to a surgical table or other substantial element. Rigid connection of the retractor device  100  to the surgical table or other fixed structure allows the device  100  to be held in place, so the surgeon may be free to perform other aspects of a procedure without having to hold the retractor device  100 . 
         [0027]    The retractor body  126  is connected to a handle  114  that may be disengageable, as described below. In the depicted embodiment, the handle  114  includes two rotatable actuators  128 ,  130  that are used to actuate the arms of the retractor device  100 . In some embodiments, rotation of the main retractor actuator  128  (centrally located on the handle  114  in the depicted embodiment) actuates the two pivoting arms (i.e., the cranial and caudal arms  102 ,  106 ). In some embodiments, rotation of the posterior actuator  130  (located at the end of the handle  114  in the depicted embodiment) actuates the posterior arm  104 . In alternative embodiments, the position of the actuators  128 ,  130  may be switched or otherwise vary. In other embodiments, each armature has a separate handle rotatable actuator to allow the armatures to be opened individually. In still other embodiments, the handle contains a single rotatable actuator that actuates all of the armatures simultaneously. The rotational axis A is shared by both the main retractor actuator  128  and the posterior actuator  130 . In alternative embodiments, other actuator elements may be used. In one example, the actuator element for the pivoting arms may be a circular disc having an axis of rotation substantially orthogonal to the axis A of the handle  114 . The disc may be connected to a worm gear, lead screw ( FIG. 2 ), or other element within the handle  114  that operates the pivoting arms  102 ,  106 . A similar disc may be used for the posterior arm  104 . Alternatively, a translating element, for example a slide movable parallel to the axis of the handle  114 , may be used to actuate the posterior arm  104 . As described in more detail below, some or all of the handle  114  may be removably connected to the retractor body  126 . A connection element  112  may connect the handle  114  to the retractor body  126 . In certain embodiments, the connection element  112  incorporates a lock having multiple positions and functions as described below with regard to  FIGS. 5A-5C . 
         [0028]    In some embodiments, retractor  100  includes three arms  102 - 106  used to help form a surgical distraction corridor in a body tissue. In some cases, arms  102 - 106  include two pivoting arms  102 ,  106  and one translating arm  104 , with each or some having a blade  118 - 122  extending therefrom. A first end of each of the pivoting arms  102 ,  106  is attached to the retractor body  126 . The opposite end of each arm  102 ,  106  is secured to a blade  118 ,  120  that is inserted into the body tissue. For certain embodiments, such as when retractor  100  is used in a lateral spinal surgical procedure, the terms “cranial” and “caudal” may be associated with certain arms  102 ,  106  and blades  118 ,  120  to help identify their position relative to the patient. For example, arm  102  and blade  120  may be referred to as caudal arm  102  and caudal blade  120 . Similarly, arm  106  and blade  118  may be referred to as a cranial arm  106  and cranial blade  118 . In that regard, the cranial blade  118  is located on the side of the retractor  100  closest to the head of the patient, while the caudal blade  120  is located on the side of the retractor  100  closest to the legs. The cranial and caudal blades  118 ,  120  are similarly configured, such that either blade  118 ,  120  may be considered either the cranial or caudal blade, depending on which side the patient is laying during a surgical procedure. In one embodiment, both pivoting arms  102 ,  106  (and therefore both blades  118 ,  120 ), pivot in an arcuate direction away from a centerline of the retractor device  100 , defined by the axis A of the handle  114 , as the main actuator  128  is rotated. Of course, other embodiments of the retractor device may be configured such that separate actuators are used for each of the two pivoting arms  102 ,  106 . Using a single actuator for both pivoting blades  118 ,  120 , however, helps ensure even opening of the surgical corridor during use and a balancing of forces against the blades  118 ,  120 . 
         [0029]    The translating arm  104  has first and second ends, with the first end connected to the main retractor body  126  and the second end connected to a blade  122 . The translating arm  104  may be referred to as the posterior arm  104  and is configured to move axially along the axis A. That is, the arm  104  may be drawn into and extended out of the retractor body  126 , as the posterior actuator  130  is actuated. The posterior arm  104  may also include an articulating arm connection element  132 , thereby providing an additional point of connection of the retractor device  100  to the surgical table or other secure structure. The posterior blade  122  is secured to the translating arm  104 , either directly or with a pivotable connection as described above with regard to the blades  118 ,  120 . Additionally, although the device  100  is typically utilized such that the handle  114  is pointed toward the surgeon, the device  100  may also be oriented so that the handle  114  is pointed away from the surgeon during use. In that case, the translating arm  104  may be referred to as an anterior arm  104 . 
         [0030]      FIG. 2  depicts an embodiment of the drive mechanisms for opening and closing the arms  102 - 106  of the retractor device  100 . As shown, a main worm drive mechanism  214  or lead screw is used to actuate the cranial and caudal arms  102 ,  106 . Rotation of the main worm drive  214  by the main actuator  128  (not shown) rotates the main worm gears  210 ,  212 , thereby separating or pivoting the cranial and caudal arms  102 ,  106 . In some embodiments, worm drive  214  engages teeth on worm gears  210 ,  212 . In one embodiment, the use of a worm drive mechanism  214  to separate the cranial  118  and caudal blades  120  allows for a large number of open positions between the blades  118 ,  120 . In some cases, the worm drive mechanism  214  provides an unlimited number of open positions depending on the amount of rotation of main worm drive  214 . Additionally, the blades  118 ,  120  are brought together using the worm drive mechanism  214 . In other words, the worm driver  214  and worm gear mechanisms  210 ,  212  prevent the cranial arm  102  and caudal arm  106  from moving unless specifically actuated. In this manner, the blades  118 ,  120  are maintained in a desired position until the worm drive mechanism  214  is actuated to further open or close the blades  118 ,  120 . A posterior drive element may be a lead screw  204  mechanism that is engaged with a lead nut  202  to the translating arm  104 , allowing for movement of the translating arm  104 . In the depicted retractor device  100 , the shaft that connects the lead screw  204  to the posterior actuator  130  passes through the main worm drive  214  that activates the cranial and caudal arms  102 ,  106 . As with the worm drive  214 , forces applied directly to the posterior blade  122  or arm  104  will not move those elements, compared to a ratchet-type or other system. 
         [0031]      FIGS. 3A and 3B  depict the retractor device  100  in closed and open positions, respectively. When in the closed position, in one embodiment, the blades  118 - 122  form a perimeter that is configured to surround one or more generally round dilators ( FIG. 7 ) that are first introduced into a body tissue. These dilators and the use thereof, are further described below. The blades  118 - 122  need not abut one another but may be so configured if desired. Gaps or spaces between the blades  118 - 122  when in the closed position are generally not a concern unless these gaps are large enough to allow creep of tissue between the blades  118 - 122 . In a particular embodiment, a gap exists between the cranial blade  118  and the caudal blade  120 , even when the cranial arm  106  and caudal arm  102  are in a closed and abutting position. In some embodiments the gap extends the entire length of blades  118  and  120 . Rotating the main actuator  128  located on the handle  114  moves the arms and the blades  118 ,  120  away from each other, in arcuate directions. Rotation of the posterior actuator  130  moves the posterior arm  104  and blade  122 . When the blades  118 - 122  are inserted into a body tissue, this movement forces the tissue apart, creating a surgical corridor, the interior of which may be accessed by a surgeon. 
         [0032]      FIG. 4  depicts a partial exploded view of an embodiment of the handle  114 , specifically, the portion of the handle  114  that actuates the cranial and caudal arms  102 ,  106 . The main actuator  128  portion of the handle  114  is connected to an elongate shaft  408 . The connection element/lock  112  includes an internal thread connection  404  that mates with a corresponding thread connection  404 ′ on a friction sleeve  402 . Rotation of the connection element/lock  112  rotates the friction sleeve  402 . A number of locking elements  406  project from the friction sleeve  402  and engage with a collar  416 . As the locking elements  406  engage with the collar  416 , functionality of the retractor device  100  changes, as described with regard to  FIGS. 5A-5C . Collar  416  is coupled to core  410 . In one embodiment, pins  412  couple collar  416  to core  410  and are welded or otherwise affixed in place. 
         [0033]      FIG. 5A  depicts a first position of the connection element  112 , as that element engages with the collar  412 . In this position, referred to as a “soft engagement” position, ball bearings  414  are free to move within the constraints of a C-spring  502 , because of openings  418  present between the locking elements  406  of the friction sleeve  402 .  FIG. 5B  depicts a second position, wherein the connection element  112  is rotated a desired or set amount, such as about thirty (30) degrees, about forty-five (4S) degrees, about sixty (60) degrees, or the like. In this position, the locking elements  406  are moved forward, such that the C-spring  502  is locked out, thereby restricting movement of the ball bearing  414 . This position captures the shaft  406  and allows the retractor arms to be opened and closed.  FIG. 5C  depicts a third position, wherein the connection element  112  is rotated an additional desired or set amount, such as about another thirty (30) degrees, about another forty-five (4S) degrees, about another sixty (60) degrees, or the like. This moves the friction sleeve  402 , and therefore the locking elements  406 , further forward so as to engage a corresponding toothed plate in the retractor body  126 . In this position, the friction sleeve  402  is in the fully locked position, such that the gaps  418  are restricting the C-spring  502  from expanding. This locks the ball bearings  414  in place, and the locking elements  406  are in a position where they will interface with the corresponding teeth in the retractor body  126  (not shown). The center core  410 , the handle body, and the collar  416  are fixed relative to each other, using a variety of techniques. For example, in one embodiment pins  412  couple collar  416  to core  410 . 
         [0034]      FIGS. 6A-6C  depict enlarged partial views of a blade/arm interface  600 , and show various technologies incorporated therein.  FIG. 6A  depicts an end of the cranial arm  106 , and blade  118 . The blade  118  is pivotably connected to the arm  106 , specifically with a blade base  604  that is positionable within a toeing cut-out  606  in the arm  106 . In one embodiment, blade  118  has a curved proximal end which engages the blade base portion of arm  106 . The blade base  604 , in one embodiment, is rotatably coupled to arm  106 . In this embodiment, a blade attachment mechanism, depicted in  FIG. 6B  as a screw  612 , threads through a hole in blade  118  proximal end and into a threaded opening in the top of blade base  604 . Once blade  118  is coupled to the blade base  604  of arm  106 , rotation of the blade base  604  allows the distal end of blade  118  to be toed in a desired direction as described below. In a particular embodiment, a toeing screw  608  is coupled to the blade base  604 . Rotation of toeing screw  608  causes movement of the blade base  604  relative to arm  106 . In a particular embodiment, toeing screw  608  extends through a threaded hole in blade base  604 . Further rotation of toeing screw  608  causes the tip portion of screw  608  to engage toeing cut-out  606  and thereafter provide for rotation of the blade base  604  relative to cut-out  606 . In this manner, blade  118  also rotates, which allows the distal end of the blade  118  to move past its initial orientation that is generally orthogonal to the arm  106 . In certain embodiments, each of the cranial and caudal blades may be toed up to about ten (10) degrees, up to about twenty (20) degrees, or up to about thirty (30) degrees from orthogonal. In a preferred embodiment, the toeing of blades  118 ,  120  allows the distal ends of blades  118 ,  120  to be toed outwards, providing a larger opening near the operative site. Regardless of the maximum toeing angle, the toeing screw  608  allows for infinite degrees of variability across the entire range of motion. In certain embodiments, the posterior blade (not shown) may be toed as well, although the posterior blade  122  typically does not have toeing ability. This toeing functionality may also be incorporated into the caudal arm  102 , as depicted in  FIG. 6B . While the depicted embodiment shows blade  118  proximal end coupled to a rotatable blade base  604 , in another embodiment the proximal end of blade  118  includes structure for providing the rotation function. In this manner, the blade  118  is firmly coupled to the arm  106 , but provides the rotation for a controlled toeing function. 
         [0035]      FIG. 6B  also depicts one or more channels  602  on the blade  120  that each may receive a probe, a K-wire, a stimulation electrode, or the like. In some embodiments, the stimulation electrode may be used to detect the location, and/or proximity of nerves in the target area, which may help avoid damage to the nerves.  FIG. 6C  depicts a rear perspective view of the caudal blade  120  of  FIG. 6B . The channel  602  for receiving the probe may be a substantially open slot along a rear face of the blade  118 , as depicted in  FIG. 6C . In general, the channel  602  may extend to a distal end of the blade  118 , such that the electrode may detect the location and/or proximity of any nerves once it is advanced into the tissue. Of course, channels  602  may be located elsewhere on the blade  118  as well. In certain embodiments, the channel  602  extends along only a portion of the length of the blade  118 , or is not present at all. In some embodiments, the channel  602  has a jog, a bend, or a narrowed region along at least a portion of the length of channel  602 . In some embodiments, the jog or bend is near the distal end of blade  118 . In this manner, the elongated flexible element, such as a K-wire or probe, inserted into the channel  602  is at least partly held in place within channel  602  due to the increased friction needed to move the flexible element relative to the jog, bend or narrowed portion. This feature may be useful, for example, to help maintain the flexible element within channel  602  while blade  118  is being inserted or removed from the patient tissue. 
         [0036]      FIG. 7  depicts side and enlarged partial side views of a dilator  700  that may be used in conjunction with the retractor depicted herein. One or more dilators  700  may be used to further increase a diameter of an initial distraction corridor as described in more detail below. Similar to the channel located on the retractor blade(s), a channel  702  may also be located on the dilator(s)  700 , and may be sized to accommodate a stimulation electrode, a probe, or other elongate element. In certain embodiments, a single stimulating electrode may be used with each component (e.g., a first dilator, a second dilator, retractor blade) introduced into the body tissue. After insertion of the first dilator, the electrode may be withdrawn and inserted into a channel of a next dilator, then into a channel in a retractor blade, until the blades are opened, thereby creating the desired surgical corridor. In some embodiments, a top surface  708  of the proximal end  704  may be constructed of hardened material to allow the dilator  700  to be impacted with an object such as a hammer during insertion. In a particular embodiment, dilator  700  comprises anodized aluminum, with the proximal end  704  comprising a steel impaction cap. In this manner, the proximal end may be struck with a hammer or other impaction tool with little to no deformation of proximal end  704 . In some embodiments, proximal end  704  may be flared (much like the head of a nail). At least a portion of the distal end  706  may be tapered to ease insertion into the initial distraction corridor. 
         [0037]      FIGS. 8A-8F  depict various embodiments of shims that may be used in conjunction with a retractor device such as described herein. In the depicted embodiments, some of the shims include one or more tabs  806  or other mechanisms to engage a ratcheted groove  804  located on the interior face of the blades  802 . The tab/ratchet interface allows the depth of insertion of the shim to be adjusted based on the needs of the surgeon performing the particular procedure, and the groove  804  is configured such that multiple depths may be achieved. In the depicted embodiment, the groove  804  comprises two opposing ratcheted surfaces that are engaged by opposing tabs  806  on the shim which is, in this case, an intradiscal shim  810 . In some embodiments, tabs  806  extend from flexible arms  808  that may be deflected inward, such as by an elongate instrument used for shim insertion or retraction. Tab  806  is disengaged from the groove  804 , allowing the shim  810  to be moved upward or downward along the blade  802 . In some embodiments, arms  808  are compressed towards each other to allow shim  810  to slidingly engage the blade  802  without a ratcheting of tabs  806  and groove  804 . The outer edges of shim  810  may engage a corresponding feature in blade  802  to allow a sliding or telescoping movement between shim  810  and blade  802 . In some embodiments, one or more outer edges of shim  810  engage a slot, a groove, a lip, an overhang, or the like in blade  802  to provide for a controlled sliding movement of shim  810  relative to blade  802 . In this manner, the shim  810  may be adjusted to a desired position relative to blade  802 , and then released to securely lock in place using tabs  806  and groove  804 . This arrangement also helps prevent the shim  810  from disengaging from blade  802 . The depicted intradiscal shim  810  may be used to fix a position of one of the blades  802  (typically, the posterior blade) relative to a spine. The distal tip  812  of the intradiscal shim  810  is sized and configured so as to be temporarily lodged between two vertebrae during a spinal procedure. The intradiscal shim  810  may, for example, restrict lateral movement of the blade  802  to which the shim  810  is attached. Intradiscal shim  810  also helps restrict blade  802  movement in the cranial-caudal directions, and the anterior-posterior directions as well. A widening shim  814  is depicted in  FIGS. 8C and 8D  and is used, inter alia, to prevent tissue creep into the spaces between the blades  802  when they are opened. A lengthening shim  816  is depicted in  FIGS. 8E and 8F  and is used to lengthen the effective depth of penetration of the blades  802 , allowing a deeper surgical corridor to be opened in a body tissue. In general, the widening and lengthening shim  814 ,  816  are utilized on the cranial and caudal blades. In some embodiments, the shims  810 ,  814 ,  816  are interchangeable, with each available for use with any of the retractor blades  802 . 
         [0038]    While the widening shim  814  and lengthening shim  816  are each depicted as discrete from the blades  802 , in alternative embodiments they may be non-removably coupled to the blades  802  prior to insertion into the body tissue. In a particular embodiment, intradiscal shim  810  is slidably and non-removably coupled to the posterior blade. This helps prevent the shim  810  from inadvertently disconnecting from the blade  802 , which would defeat the purpose of using an intradiscal shim  810  to fix the position of the blade  802  in the body. In this manner, the intradiscal shim  810  operates as an extension of the retractor blade  802  when a distal tip  812  of the shim  810  is positioned to extend beyond the distal tip of the retractor blade  802 . When not in use, the shim  810  is withdrawn into the retractor blade  802  such that the distal tip  812  of the shim  810  does not extend beyond the distal tip of the retractor blade  802 . 
         [0039]    A configuration of such a blade/shim interface where the shim is not removable from the blade  802  is depicted in  FIG. 8G . The shim  810  and blade  802  are coupled together in a manner to allow a slidable relationship between the shim  810  and the blade  802 . In the depicted embodiment, inner edges  818  of the blade  802  substantially surround wings  820  of the shim  810 , which prevents the shim  810  from being pulled away from the blade  802 . A travel stop  822  is located at a bottom of the blade groove  804  or adjacent the blade groove  804 . The travel stop  822  prevents the shim  810  from being removed from the bottom of blade  802 . In addition, pins or other structure (not seen in  FIG. 8G ) operate to restrict movement of shim  810  towards the top of blade  802 . In this manner, intradiscal shim  810  has a limited range of sliding motion relative to blade  802 , but is not removable from blade  802  through either the top (proximal) or bottom (distal) ends of blade  802 . 
         [0040]      FIGS. 8H and 8I  depict an anchoring shim  824  that may be used with the retractor devices described herein. The anchoring shim  824  includes a body  826  that is configured to slide within the groove  804  of the blade  802 . The blade  802  includes inner edges  818  that substantially surround or engage wings  820  of the anchoring shim  824 , similar to the blades and wings depicted in  FIG. 8G , above. Unlike the shims of  FIGS. 8A-8G , however, the anchoring shim  824  lacks any rear projections to engage with the ratcheted groove  804 . Instead, the anchoring shim  824  is configured to slide unimpeded along the blade  802 . Tabs  828  may engage with an elongate tool to move the anchoring shim  824  within the groove  804  or to hold the shim  824  steady. Unlike the tabs  806  depicted above, however, these tabs  828  need not be deflected inward to move the shim  824 . Instead, the tabs  828  serve as a point of connection with the elongate tool. In some embodiments, the elongate tool also engages the blade inner edges, wings, grooves, or similar structure of the blade for additional control of shim movements when using the elongate tool. Extending from and through the body  826  is a fastener  830  that may be used to anchor the blade  802  to a vertebral body. In the depicted embodiment, fastener  830  is a threaded screw with a tool engaging proximal portion. Other fasteners also may be used, including pins, elongate wires, or the like. In some embodiments, the anchoring shim  824  is utilized on the cranial or caudal blades, for coupling of the fastener  830  to a vertebral body. A head of the fastener  830  may be actuated by a tool, such as a hex driver or other device for securing the fastener  830  to bone. Once one of either the cranial or caudal blades are anchored via the shim  824 , opening of the retractor device arms will result in the unanchored blade moving away from the anchored blade, thus moving a central axis of the surgical corridor away from the anchored blade. 
         [0041]      FIGS. 8J and 8K  depict another embodiment of an anchoring shim  832 . This anchoring shim  832  utilizes deflectable tabs  808  to selectively locate associated projections (not shown) within the ratcheted groove  804  (similar to the shims of  FIGS. 8A-8G ). Two fastener retention ears  834  are located on either side of the vertebral screw  830 . This anchoring shim  832  differs additionally from the anchoring shim  824  of  FIGS. 8H and 8I  in that the fastener holding force provided by the retention ears  834  is less than that provided by the enclosed body  824  of the first anchoring shim  824  of  FIGS. 8H and 8I . For example, the shim  832  main body and ears  834  generally surround fastener  830  on three sides, leaving a gap on one side. As a result, a force applied to blade  802  in a direction generally opposite this gap may allow shim  832  to disengage from fastener  830 . In some circumstances, this may be desired. In other cases, the anchoring shim  832  may be used when the blades  802  have already been opened. 
         [0042]      FIG. 8L and 8M  depict yet another embodiment of an anchoring shim  836 , that also utilizes deflectable tabs  808  to selectively locate associated projections (not shown) within the ratcheted groove  804  (similar to the shims of  FIGS. 8A-8G ). A single fastener retention hook  838  wraps at least partially around the fastener  830 . Accordingly, this anchoring shim  836  may provide more screw holding force than the embodiment depicted in  FIGS. 8J and 8K . Regardless of the differences, use of each of the anchoring shims described herein may be desirable at different stages of a surgical procedure, depending on particular working conditions, clearance issues, or surgeon preferences. 
         [0043]    Yet another anchoring shim  840  is depicted in  FIG. 8N . This anchoring shim  840  is similar in configuration to the anchoring shim  824  of  FIGS. 8H and 8I , in that it may freely slide within the groove  804  of the blade  802 . Further, housing  826  has a channel or hole therethrough to receive the fastener  830 . Again, fastener  830  may be a threaded screw, a non-threaded screw, a pin, an elongate wire, or the like. Connected to the housing  826  is an elongate arm  842 . Arm  842  is coupled to the armature  844  to which the blade  802  is attached. In this manner, once the fastener  830  is anchored to the vertebral body, the blade  802  may be disconnected from the arm  844  and from the shim  840  and removed from the surgical corridor. This may occur, for example, by removing screw  612  holding the proximal end of blade  802  to armature  844 , and lifting the blade  802  vertically to disengage blade  802  from shim  840 . The elongate arm  842  allows the armature  844 , and thus the retractor, to remain secured to the anchoring shim  840 . Accordingly, access to the interior of the surgical corridor may be improved with the blade  802  removed therefrom. 
         [0044]    In another embodiment, one or more of the retractor blades comprise telescoping blades. In such an embodiment, the retractor blade includes a proximal-most portion coupled to the retractor arm and a distal-most portion. The proximal-most portion and the distal-most portion overlap in a telescoping or nestled fashion to allow the retractor blade to have a variable overall length. In some embodiments, the telescoping blade components have a slidable relationship, but are non-separable, to ensure they stay connected while opening or holding the surgical corridor. In some embodiments, shims described herein have a boss, peg, or similar feature on the back of the shim which slides in a groove or slot in the blade to which it is coupled. The groove has a closed distal end that operates as a travel stop for the shim boss or the like. In this manner, the boss and groove combination, or similar structure, prevents the shim from sliding out the distal end of the blade. 
         [0045]      FIGS. 9A-9C  depict a method of performing a surgical procedure with the systems and devices described herein.  FIG. 9A  depicts a transverse cross-sectional view  900  of the torso  902  of a human body. For a lateral surgical procedure, the patient is positioned on a surgical table and x-rays, such as true lateral and anterior-posterior, may be taken. The surgeon may then make a first incision in the desired location. The initial distraction corridor (i.e., separation of the muscle fibers) is made using blunt dissection, as depicted in  FIG. 9A . Blunt dissection requires a surgeon to digitally penetrate the torso  902  with one or more fingers  904 . Using blunt dissection, a posteriorly-directed trajectory (aiming for the transverse process) is used to enter the retroperitoneal space  906 . Once the retroperitoneal space  906  has been entered, the tissue is distracted into the free space of the retroperitoneum. The peritoneum may be moved anterior with the fingers  904  and blunt dissection continued to palpate to the transverse process posteriorly. The finger  904  may be slid forward to the retro-psoas recess and over the dome of the psoas to ensure retroperitoneal viscera have been safely retracted anteriorly. In general, the distraction corridor is formed in a direction generally towards the spine  908 . 
         [0046]      FIG. 9B  depicts an anterior view of a spine  908 . After the blunt dissection depicted in  FIG. 9A , a first dilator  910  is inserted through the incision. The location of the first dilator  910  may be verified using lateral fluoroscopy. It is desirable that the first dilator  910  be targeted to the center of the intervertebral disc space  912 . The first dilator  910  may be advanced through the psoas muscle (not shown) using a rotating motion. In some cases, the first dilator  910  may be located between about the center and about the posterior-third of the disc space  912 , and the position verified using lateral fluoroscopy. Once the first dilator  910  is an acceptable position, a K-wire  914  may be inserted through the center thereof and into the disc space  912 . The K-wire  914  may be inserted approximately half-way across the disc space  912  to assist in securing the access entry point. Again, anterior-posterior and lateral fluoroscopy may be used to ensure the proper location of the K-wire  914  and the first dilator  910 . Thereafter, a second dilator (not shown in  FIG. 9B ) may be advanced over the first dilator  910 , using a rotating motion. 
         [0047]      FIG. 9C  depicts a perspective view of a spine  908 . After insertion of the second dilator  916  over the first dilator  910 , the retractor blades  918  of the retractor device  920  are placed around the second dilator  916  and advanced downward into position. Position of the blades  918  may be verified as in-line with the disc space using fluoroscopy. It is generally desirable that the retractor  920  be parallel to the disc space  912  and the retractor working channel (the space between the blades  918 ) be aligned with the disc space  912 . In some cases, such as when working around other bony structure (e.g., ribs, iliac crest, etc.), the retractor  920  may be angled in the cranial/caudal direction relative to the patient. The retractor  920  may next be secured in place by connecting an articulating arm (not shown) to one of the retractor connection points. The articulating arm is also connected to a generally fixed or stable structure, such as the surgical table, to provide a steady platform for retractor  920 . 
         [0048]    The surgical corridor may now be expanded and otherwise altered as desired in accordance with the manipulations of the retractor device  920  described above. Typical functions include separation of the cranial/caudal blades, retraction of the posterior blade, toeing of the blades, etc. Once the retractor blades  918  are opened to the desired position, the first dilator  910 , the second dilator  916 , and the K-wire  914  may be removed. Once these components are removed, an implant insertion procedure may be performed. Any number of actions may be taken, in almost any order, to insert an implant. For example, an intradiscal shim (as depicted above), may be extended out of the posterior blade in which it is located during insertion and into the disc space  912 . The position of this element may be verified using anterior-posterior fluoroscopy. Additionally, widening or lengthening shims may be advanced as needed. If desired, the handle  922  may be removed from the retractor device  920 . Annulotomy and discectomy procedures may then be undertaken to remove the disc material, and an appropriately sized implant may be inserted. After implantation, the retractor blades  918  may be closed and removed from the body and the surgical corridor sutured closed. 
         [0049]      FIG. 9D  depicts a perspective view of the retractor device  920  with the blades  918  in an open position. In this figure, the spine has been removed for clarity. As described elsewhere herein, rotation R of the main actuator  926  of the handle  922  opens the cranial and caudal arms  928 . Resistance of the patient tissue, however, may make difficult the rotation R of the main actuator  926  about the handle axis A. In that case, the posterior actuator  930  may be withdrawn from the handle  922  along the axis A. Thereafter, a tip of the posterior actuator  930  may be inserted into one of several torque points  932  about an outer diameter of the main actuator  926 . A torque T may be applied to the posterior actuator  930 , such that actuator  930 t acts as a lever to make for easier rotation R of the main actuator  926 . Once the arms  928  have been opened to the desired position, the posterior actuator  930  may be returned to its original location on the handle  922 . As previously described, in some embodiments main actuator  926  operates a worm gear drive to allow blades  918  to be opened a desired amount and maintained. 
         [0050]      FIG. 9E  depicts a perspective view of the retractor device  920  with the blades  918  in an open position. In this figure, the spine has been removed for clarity. Forces acting on the blades  918  by the body tissue may also cause the retractor device  920  to move undesirably. To overcome such forces, a pivot lever  934  may be connected to one of the arm connections  936  (that are typically used for connection to an articulating arm, as described above) and a torque T′ applied. This will rotate R′ the entire device  920  about the device axis A, thus improving the ability to position the device  920  as desired. This may be especially helpful when attempting to anchor any of the blades  918  to the vertebrae with the anchoring shims described above. Pivot lever  934  also may be used to rotate retractor  920  about the dilators to aid in the insertion of retractor  920  towards the surgical site, or provide a hand-hold for a user to better hold, support or manipulate retractor  920 . 
         [0051]      FIG. 9F  depicts other components that may be utilized with the retractor device  920  to fix the position of the device  920  within the body and/or to create or maintain a desired operative opening. As shown, a span member  938  connects to the free ends of both of the articulating arms  928 . In some embodiments, the span  938  defines a slot  940  through which one or more anchor rods  942  may be passed. The anchor rods  942  may be screwed into vertebral bodies, typically on either side of a target disc  912 . In addition to fixing the position of the device  920  relative to the spine  908 , the anchor rods  942  may also be used to hold back tissue that may creep into the space between the cranial and caudal blades  918  once opened. 
         [0052]    In an alternative embodiment, an additional or optional paddle  944  is provided to help create or maintain a desired operative window. For example, and as depicted in  FIG. 9G , paddle  944  may be coupled to a span  946  placed between the two pivoting arms (not depicted in  FIG. 9G ) after the surgical access corridor is created. The span  946  may be similar or identical to the span  938  of  FIG. 9F . In general, the paddle  944  is positioned generally opposite the posterior blade, although it could be coupled to the span  938  at any location. In this manner, the paddle  946  helps maintain an additional side, such as an anterior side, of the surgical access corridor. The paddle may simply be a static blade or rod, or other elongate member having any cross-sectional profile. In the depicted embodiment, the paddle  944  includes an elongate rod  948  having a wider base  950 . Opposite the wider base  950  is a handle  952  that may be moved as desired to position the paddle  944 . A fastener member, shown as a threaded knob, operates to couple elongate rod  948  to the span  946 . The fastener member further may couple the elongate rod  948  to control the depth of paddle  944  relative to the surgical location. In most embodiments, the paddle  944  lacks any additional structure that would enable use thereof with shims. However, in alternative embodiments, such structure (grooves, etc.) may be incorporated if desired. Since the paddle  944  is generally used to prevent tissue creep from the space between the cranial and caudal blades, any type of rigid structure that can hold tissue is sufficient. 
         [0053]    The methods depicted in  FIGS. 9A-9C  may be modified by the incorporation of known neuromonitoring techniques. Neuromonitoring is not required to perform the procedures described herein, but may be desirable and is therefore incorporated at the surgeon&#39;s discretion. A number of different neuromonitoring systems may be utilized. Manufacturers of acceptable systems include Caldwell Laboratories, Inc., of Kennewick, Wash. Caldwell Laboratories, as well as other manufacturers, also manufactures monitoring probes (also referred to as electrodes) that may be utilized in conjunction with various surgical instruments or alone for treatment or diagnostic purposes. These electrodes are typically disposable elements that may be inserted into the body as required. The dilators described herein, as well as the retractor blades, include one or more channels to receive such probes. The probes may be inserted before or after insertion of the particular component into the body, again at the surgeon&#39;s discretion. Neuromonitoring techniques, in conjunction or discrete from surgical implements, are well-known to persons of skill in the art. Regardless, when electrodes are used in conjunction with the components described herein, the electrode is typically first inserted into the appropriate channel of the component. Once the component is inserted into the desired depth within the body, the neuromonitoring equipment is then activated and the response from the nerves detected. Proper operation of neuromonitoring equipment typically requires that the component first be inserted, stopped at a desired position, then neuromonitoring performed. This gives the surgeon the feedback necessary to adjust the position of the component so as to avoid the nerves. This may be performed in steps, advancing the component a certain distance, stopping advancement, monitoring, and repeating advancement as required. 
         [0054]      FIGS. 10A and 10B  depict a method  1000  of using a retractor system. Although the method is described in the context of lateral-approach spinal surgery, it should be noted that the systems and methods described herein may be used in virtually any surgery where limited muscular trauma is desired. In surgeries where limited, controlled separation of muscle fibers is desirable, the retractor system described herein may be particularly advantageous. Although described in conjunction with  FIGS. 10A and 10B , the order of steps or procedures may differ from that depicted. First, as previously depicted in  FIG. 9A , the patient is properly positioned and an incision is made in the desired location and the initial distraction corridor is formed via blunt (i.e., digital) dissection (operation  1002 ). After the initial distraction corridor is formed, a first dilator is inserted (operation  1004 ). Thereafter, a K-wire may be inserted via the lumen of the first dilator and secured to the disc space (operation  1006 ). This helps prevent movement of the dilator, thus keeping that element (and the subsequent elements) properly positioned within the body. Thereafter, a second dilator is inserted over the first dilator (operation  1008 ), such that the first dilator (and K-wire located therein) are located within the lumen of the second dilator. If desired, additional dilators may be used to create a larger corridor before insertion of the retractor. A retractor device is then inserted over the second dilator (operation  1010 ). During insertion of the retractor device, the arms and blades of the device are in the closed position (that is, the position where each blade is located as close as possible to the two adjacent blades). Blades containing the intradiscal shim have a sufficiently low profile to allow for insertion of the retractor with the intradiscal shim. Further, the low profile of the intradiscal shim and the shim extension tool allows the shim to be advanced from a retracted position to an extended position after the retractor has been inserted and before the dilators have been removed. This helps secure the retractor with the intradiscal shim between two bony structures, such as vertebrae, before the dilator(s) and/or K wire is removed. Additionally, any blades that may have toeing functionality should be set such that the blades are parallel to the direction of insertion. During insertion, all three of the blades of the retractor device are inserted simultaneously. 
         [0055]    Once the retractor device is inserted to the desired depth, the K-wire and dilators may be removed from the area between the blades (operation  1012 ). To secure the retractor device at the desired location, an articulating arm connected to the surgical table or other fixed element may be connected to one of the connection points on the retractor device body or posterior arm (operation  1014 ). In some embodiments, operation  1014  occurs prior to operation  1012 . In addition to the articulating arm, an intradiscal shim located within the posterior blade may also be extended into the disc space to further secure the device in the desired location. The operation of extending the intradiscal shim is described below. Once the retractor device is in the desired position, the cranial and caudal arms (and, therefore the cranial/caudal blades) may be expanded and the posterior blade retracted (operation  1016 ). Once the various blades are expanded to the desired distance, a surgical procedure may be performed. 
         [0056]    However, the retractor device described herein includes, or may be utilized with, a number of supplemental components to increase versatility of the device. This versatility allows a surgeon to modify the surgical corridor (operation  1018 ) as required or desired to address particular internal anatomical conditions, or to otherwise improve usability of the retractor device. For example, and as noted first above, the intradiscal shim may be extended from its stored position in the posterior blade to further fix the position of the device relative to the spine (operation  1018   a ). Other shims may also be used in conjunction with the cranial and caudal blades. For example, the widening and/or lengthening shim may be used to supplement the blades. In some embodiments, the shims are loaded into their respective blades after the retractor blades have been inserted into the patient. This occurs, for example, by inserting the shim down through the proximal end (top) of the blade using a shim inserter tool. Alternatively, at least some of the shims have a sufficiently low profile to be inserted into the blades prior to insertion of the blades into the patient. As previously noted, there may be a small gap between one or more blades as the blades are inserted over the largest dilator. To use either of the widening or lengthening shims, the shim is placed into the shim groove in the desired blade, then advanced down towards the end of the blade (operation  1018   b ). The tab and groove interface of the shim and blade allows the shim to be advanced as far as required or desired, and resists or prevents undesired movement of the shim back towards the proximal end of the blade. The cranial and caudal blades may also be toed out to increase the area of the corridor proximate the spine (operation  1018   c ). If more robust fixation of the blades within the surgical corridor is desired, anchoring shims may be used to engage the vertebra (operation  1018   d ). Typically, the anchoring shims are inserted after the blades have been inserted into the patient and opened or separated at least enough to allow shim insertion. Alternatively or additionally, one or more rods may also be anchored (operation  1018   e ). Another modification of the corridor includes utilizing the supplemental paddle between the cranial and caudal arms to prevent tissue creep into the space therebetween (operation  1018   f ). Of course, any or all of these operations may be performed at any desired time to modify, enhance, or otherwise support the surgical corridor. 
         [0057]    Regardless, once the desired corridor is obtained, an implant insertion procedure is performed (operation  1020 ). The steps of the implant insertion procedure would be known to a person of skill in the art and are not described further. Once the implant insertion procedure is completed, shims and other optional features are retracted or removed. The retractor blades may be closed and the device removed from the body, allowing the surgeon to close the incision (operation  1022 ). As described above, neuromonitoring may be utilized during any point of the method, at the discretion of the surgeon. 
         [0058]    Materials utilized in the manufacture of the retractor system may be those typically used in surgical equipment. Stainless steel, titanium, and other robust metals that may be sterilized may be used. In applications where fluoroscopy is desirable or required during the procedure (e.g., in the spinal surgery procedures described herein), radio-lucent materials may be particularly desirable. In those applications, aluminum, anodized aluminum, and rigid polymers may be utilized. In some embodiments, the retractor blades comprise aluminum which has been anodized with a hard coat anodizing process to create an electrical insulated material. Such blades may be useful, for example, in the event the surgeon prefers to use electrical nerve monitoring equipment. Carbon fiber-reinforced polymers may be particular useful, as they are lightweight, extremely strong, and may be sterilized. Of course, retractor systems utilizing a combination of materials may be used. For example, radio-lucent materials may be used for the blades and less expensive radio-opaque material may be utilized for the elongate element and armatures. Use of radio-lucent materials for the cover plate, armatures, and body may be particularly advantageous, as an instrument so configured will be less visible in lateral x-rays. Additionally, radio-opaque materials may be impregnated in discrete locations of components manufactured of radio-lucent materials such that position of certain parts of the system may be visible during procedures, without impeding overall visibility. 
         [0059]    While there have been described herein what are to be considered exemplary and preferred embodiments of the present technology, other modifications of the technology will become apparent to those skilled in the art from the teachings herein. The particular methods of manufacture and geometries disclosed herein are exemplary in nature and are not to be considered limiting. It is therefore desired to be secured in the appended claims all such modifications as fall within the spirit and scope of the technology. Accordingly, what is desired to be secured by Letters Patent is the technology as defined and differentiated in the following claims, and all equivalents.