Abstract:
Embodiments of the invention include instruments and methods for providing surgical access to a surgical site. Some embodiments include a flexible arm that adjustably holds a retractor blade to enable access to the surgical site.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of instruments for providing access during surgical procedures, and more particularly relates to retractor instruments for enabling access to a surgical site and shielding tissue during a surgical procedure. 
     BACKGROUND 
     Surgical procedures have generally become less disruptive to peripheral tissues as surgical techniques have progressed. Traditional surgical procedures used to treat tissues through incisions have often been very disruptive to peripheral tissues. Such procedures may include incisions through the skin, muscles, vessels, nerves, and other tissues, and may include long and deep incisions. Traditional procedures may include retractors that are either larger than is necessary to effectively perform a procedure or that are cumbersome to operated and therefore require longer periods of retraction than is necessary to perform a procedure. Traditional procedures, consequently, may lead to more trauma to peripheral tissues, more pain, and more lengthy and expensive recoveries. Cumbersome equipment that results in longer operating times may also lead to greater hospital, surgical staff, and physician expenses. 
     Modern surgical instruments and techniques have enabled less invasive and more expedient access to surgical sites. By way of non-limiting example, less invasive surgical instruments and techniques have been used in spinal surgery to separate and progressively dilate and retract tissues rather than to sever and retract the tissues. Developments in less invasive surgical instruments and methods have been significant, but there remains a need for enhancement of instruments and methods. Enhanced instruments and methods may include features that enable one or more of improvements to the efficiency, speed, access capability, or size of an instrument used in one or more methods. 
     Although particular embodiments of the surgical instruments and methods are described herein in association with particular spinal surgical procedures and surgical approaches, certain instruments and methods may be equally effective in other surgical procedures in the spine or in other areas of the anatomy. 
     SUMMARY 
     One embodiment of the invention is a surgical access instrument. The surgical access instrument may include a flexarm retractor with a base, a first retractor appendage coupled to the base wherein the first retractor appendage has a length and lateral sides along its length, a flexible arm coupled to the base at a proximal end of the flexible arm such that a distal end of the flexible arm is movable relative to the base, and a second retractor appendage coupled to the flexible arm at the distal end of the flexible arm wherein the first retractor appendage has a length and lateral sides along its length. The surgical access instrument may also include a transverse retractor coupled to the base of the flexarm retractor. The transverse retractor may include an assembly with a frame, a threaded shaft rotatably coupled with the frame, a first carriage coupled with the threaded shaft that is configured to translate along the threaded shaft when the shaft is turned, and a second carriage coupled with the threaded shaft that is configured to translate along the threaded shaft when the shaft is turned. Embodiments of the transverse retractor may also include a first transverse retractor appendage coupled with the first carriage, wherein the first retractor appendage has a length and lateral sides along its length, and a second transverse retractor appendage coupled with the second carriage, wherein the second retractor appendage has a length and lateral sides along its length. In some embodiments, the first retractor appendage, the second retractor appendage, the first transverse retractor appendage, and the second transverse retractor appendage are configured to be aligned substantially along their respective lengths and an access portal to the surgical site is formed among a lateral side of the first retractor appendage, a lateral side of the second retractor appendage, a lateral side of the first transverse retractor appendage, and a lateral side of the second transverse retractor appendage. 
     An embodiment of the invention is a flexible retractor for holding back tissue near a surgical site. The flexible retractor may include a base, a first retractor appendage coupled to the base wherein the first retractor appendage has a length and lateral sides along its length, a flexible arm coupled to the base at a proximal end of the flexible arm such that a distal end of the flexible arm is movable relative to the base, and a second retractor appendage coupled to the flexible arm at the distal end of the flexible arm wherein the first retractor appendage has a length and lateral sides along its length. The first and second retractor appendages may be aligned substantially along their respective lengths and an access portal to the surgical site is formed between a lateral side of the first retractor appendage and a lateral side of the second retractor appendage. 
     Still another embodiment of the invention is a transverse retractor. Embodiments of the transverse retractor include an assembly with a frame, a threaded shaft rotatably coupled with the frame, a first carriage coupled with the threaded shaft that is configured to translate along the threaded shaft when the shaft is turned, and a second carriage coupled with the threaded shaft that is configured to translate along the threaded shaft when the shaft is turned. Embodiments of the transverse retractor include a first transverse retractor appendage coupled with the first carriage, wherein the first retractor appendage has a length and lateral sides along its length, and a second transverse retractor appendage coupled with the second carriage, wherein the second retractor appendage has a length and lateral sides along its length. In some embodiments, a first portion of the threaded shaft that is coupled with the first carriage has right-hand threads and a second portion of the threaded shaft that is coupled with the second carriage has left-hand threads such that rotation of the shaft in a first rotational direction causes the first and second transverse retractor appendages to move together simultaneously and rotation of the shaft in a second rotational direction opposite from the first rotational direction causes the first and second transverse retractor appendages to move apart simultaneously. 
     Another embodiment of the invention is a method of creating an access portal to a surgical site. The method may include introducing a first retractor into the surgical site such that the retractor is in a position to separate tissues along a first axis, and introducing a flexarm retractor into the surgical site such that the flexarm retractor is in a position to separate tissues along a second axis that is substantially transverse to the first axis. The flexarm retractor of some embodiments may include a base, a first retractor appendage coupled to the base, a flexible arm coupled to the base at a proximal end of the flexible arm, and a second retractor appendage coupled to the flexible arm at a distal end of the flexible arm. Method embodiments may also include coupling the flexarm retractor with the first retractor, separating the first retractor appendage from the second retractor appendage to create an access portal to the surgical site, and actuating a control on the flexarm retractor to stiffen the flexible arm to fix the second retractor appendage in a desired location. 
     Yet another embodiment of the invention is a method of creating an access portal to a surgical site. The method includes introducing a retractor with two appendages into the surgical site such that the retractor is in a position to separate tissues along an axis. The retractor may include mechanisms for switching from a first state where one rotational control moves both appendages simultaneously together or apart along the axis to a second state where the one rotational control moves only one of the appendages along the axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a surgical access instrument. 
         FIG. 2  is a perspective view of the flexarm retractor portion of the surgical access instrument of  FIG. 1 . 
         FIG. 3  is a perspective view of the flexarm retractor portion of the surgical access instrument of  FIG. 1  with certain components removed. 
         FIG. 4  is a perspective view of the flexarm retractor portion of the surgical access instrument of  FIG. 1  with certain components removed. 
         FIG. 5  is a perspective view of the flexarm retractor portion of the surgical access instrument of  FIG. 1  with certain components removed. 
         FIG. 6  is a perspective view of the transverse retractor portion of the surgical access instrument of  FIG. 1 . 
         FIG. 7  is a perspective view of the transverse retractor portion of the surgical access instrument of  FIG. 1 . 
         FIG. 8  is a perspective view of the transverse retractor portion of the surgical access instrument of  FIG. 1 . 
         FIG. 9  is a perspective view of the transverse retractor portion as illustrated in  FIG. 8  with portions of the transverse retractor cut away to illustrate additional components. 
         FIG. 10  is an elevation view of internal components of the transverse retractor with a central shaft rotationally engaged with two portions of the threaded shaft. 
         FIG. 11  is an elevation view of internal components of the transverse retractor with a central shaft rotationally engaged with one portion of the threaded shaft and rotationally disengaged with another portion of the threaded shaft. 
         FIG. 12  is a perspective view of a surgical access instrument. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of a surgical access instrument  1  is illustrated in  FIG. 1 . The illustrated surgical access instrument  1  includes a flexarm retractor  10  couple with a transverse retractor  30 . An embodiment of the flexarm retractor  10  will be described in more detail with reference to  FIGS. 1-5 . An embodiment of the transverse retractor will be described in more detail with reference to  FIGS. 6-11 . 
     The flexarm retractor  10  illustrated includes a base  11 . As most clearly illustrated in  FIG. 4 , the base  11  of the embodiment shown has a C-shaped body  12  and a rack  13 . The C-shaped body  12  is configured to couple with the transverse retractor  30 . The coupling between the C-shaped body  12  and the transverse retractor  30  may be an interference fit where the inside of the C-shaped body  12  is pressed against the transverse retractor  30 . An interference fit may be adequate to maintain the integrity of the surgical access instrument  1  because forces generated by interactions among components of the surgical access instrument  1 , and the retracted tissues may also serve to stabilize the flexarm retractor  10  relative to the transverse retractor  30 . The C-shaped body  12  is prevented by the extents of the C-shape from translating up and down relative to the transverse retractor  30 . Rotational movement allowed between the C-shaped body  12  and the transverse retractor may be advantageous in surgical procedures where the transverse retractor  30  is first placed in a surgical site, and then the flexarm retractor  10  is added to the construct to complete the surgical access instrument  1 . For example, when the transverse retractor  30  is in place in a surgical site, the C-shaped body  12  may be placed against the transverse retractor  30  with one or both of a first retractor appendage  21  and a second retractor appendage  22  rotated up and out of the surgical site. The flexarm retractor may then be rotated about the C-shaped body  12  to insert the first retractor appendage  21  and the second retractor appendage  22  into the surgical site in a desired location. 
     The coupling between the C-shaped body  12  and the transverse retractor  30  may also be a fixed or pinned coupling in some embodiments. By way of example and without limitation, the coupling may be achieved by welding, may include an adhesive, may include a fastener such as a screw, pin, bolt, rivet, or the like, or may be accomplished through any other effective mechanism. 
     The rack  13  of the embodiment illustrated in  FIGS. 1-5  provides a connection between the base  11  and the first retractor appendage  21  through a bar  23 . The bar  23  extends away for the base  11  and terminates at the first retractor appendage  21 . The bar  23  shown is slideably coupled to the base  11  such that the first retractor appendage  21  may be moved closer to or more distant from the surgical site relative to the base  11  by sliding the bar  23  relative to the base  11 . A pinion assembly  24  couples with the rack  13 . The pinion assembly  24  includes a catch  25  that provides a releasable connection between the pinion assembly  24  and one or more teeth  14  of the rack  13 . The combination of the teeth  14  and the catch  25  allows for movement of the rack  13  relative to the pinion assembly  24  to be selectively maintained at a desired position. In some embodiments, the catch  25  is biased toward engagement with the teeth  14  such that pressure on a lever end  26  of the catch  25  is required to disengage the catch  25  from the teeth  14 . The teeth  14  may be formed such that the pinion assembly  24  ratchets in either direction relative to the base  11 . By these or other effective mechanisms, the first retractor appendage  21  may be switched between a free state and a locked state relative to the base  11 . The first retractor appendage  21  may also be connected directly to the base  11  in some embodiments without the intervening bar  23  as illustrated. This connection may be fixed or may be releasable. 
     The pinion assembly  24  also includes a spindle  27  in some embodiments. The spindle  27  includes one or more cogs (not shown) around a perimeter of the spindle  27  that engage with the teeth  14  of the rack  13 . By turning the spindle  27 , the cogs may be advanced along the teeth  14  to move the rack  13  relative to the pinion assembly  24 . The spindle  27  may further include a wing nut, internal hex, external hex, or other opening or component useful in applying torque to the spindle  27  to turn the spindle  27  and move the rack  13  relative to the pinion assembly  24 . 
     As illustrated in  FIG. 5 , the first retractor appendage  21  includes a length extending along its longitudinal axis and lateral sides  29  along its length. The first retractor appendage  21  illustrated has a radius or curve about its longitudinal axis. The curve of the illustrated embodiment has a relatively large radius, but may be significantly reduced in some designs of the invention. For example, the radius may be small to produce essentially a section of a tube approximately the same diameter as the width of the retractor appendage illustrated in  FIG. 5 . In other embodiments, the retractor appendage may be substantially flat or planar to form a substantially flat blade. 
     As illustrated in  FIGS. 1-3 , a flexible arm  15  is coupled to the base  11  at a proximal end  16  of the flexible arm  15 . A distal end  17  of the flexible arm  15  is movable relative to the base  11 . In the embodiment shown, multiple cannulated joints  18  interconnect with one another along a curvilinear path to form a continuous cannulated member. In some embodiments, the multiple cannulated joints  18  may interconnect with one another along a linear path. A tensile element  19  is disposed through the cannula of the multiple cannulated joints  18 . Several of the cannulated joints  18  are removed from  FIG. 3  to show an end of one of the cannulated joints  18  and the tensile element  19 . The flexible arm  15  of the illustrated embodiment may have a free state and a locked state relative to the base  11 . The free state may exist when the tensile element  19  is loosened and some or all of the cannulated joints  18  are rotatable relative to one another. Another example of a free state is where tension is applied to the tensile element  19  to create some resistance among the cannulated joints  18 , but adequate lateral pressure to the flexible arm will result in movement of the flexible arm  15  relative to the base  11 . A locked state may exist where significant tension is applied to the tensile element  19  to prevent rotation or movement of the cannulated joints  18  relative to one another. In some embodiments, the second retractor appendage  22  may separately or in conjunction with the flexible arm  15  include a free state and a locked state as a result of tension applied to the tensile element  19  or by other effective mechanisms. 
     All of the cannulated joints  18  have been removed from the tensile element  19  in the  FIG. 5  illustration to show how the tensile element  19  of the embodiment interacts with the bar  23 . The tensile element  19  shown fits into a notch  28  in the bar  23  to accommodate movement of the rack  13  next to the bar  23 . The tensile element  19  of the embodiment shown in  FIGS. 1-5  is threaded through a hole  89  ( FIG. 4 ) in the base  11  and fixed to the bar  23 . Consequently, movement of the bar  23  relative to the base  11  by turning of the spindle  27  results in tensioning of the tensile element  19  and locking of the flexible arm  15 . Therefore, by common activation of this control, the first retractor appendage  21 , the flexible arm  15 , and the second retractor appendage  22  may all be switched between a free state and a locked state relative to the base  11 . In other embodiments, the bar  23  is independently movable relative to the base  11  and the tensile element  19  is separately able to be tensioned. For example, and without limitation, the notch  28  may pass through the bar  23  in some embodiments, and the tensile element  19  may include a separate control for tightening and loosening the tensile element  19 , and therefore the flexible arm  15 . In such an embodiment, turning of the spindle  27  results in movement of the first retractor appendage  21  relative to the base  11 , and activation of the separate control tightens or loosens the tensile element  19  and the flexible arm  15 . 
     As shown in  FIG. 2 , the second retractor appendage  22  includes a length extending along its longitudinal axis and lateral sides  9  along its length. The second retractor appendage  22  illustrated has a radius or curve about its longitudinal axis. The curve of the illustrated embodiment has a relatively large radius, but may be significantly reduced in some designs of the invention. For example, the radius may be small to produce essentially a section of a tube approximately the same diameter as the width of the retractor appendages illustrated in  FIG. 2 . In other embodiments, the retractor appendage may be substantially flat or planar to form a substantially flat blade. 
     As is shown in combinations of  FIGS. 1-3  and  5 , the first retractor appendage  21  and the second retractor appendage  22  are aligned substantially along their respective lengths. An access portal  99  to a surgical site is formed between lateral sides  29 ,  9  of the first retractor appendage  21  and the second retractor appendage  22 . 
     In  FIGS. 6-11 , an embodiment of the transverse retractor  30 , including various internal components, is illustrated. The transverse retractor  30  may be coupled to an operating table or other piece of surgical support structure through eyelets  95 . An assembly  35  includes a frame  36 , a threaded shaft  40  rotatably coupled with the frame  36 , a first carriage  31  coupled with the threaded shaft  40  that is configured to translate along the threaded shaft  40  when the threaded shaft  40  is turned, and a second carriage  32  coupled with the threaded shaft  40  that is configured to translate along the threaded shaft  40  when the threaded shaft  40  is turned. The frame  36  illustrated includes a housing  33 , a center strut  34 , a first end cap  37 , and a second end cap  38 . The housing  33  of the illustrated embodiment is coupled to the center strut  34  with fasteners (not shown) that extend through fastener openings  63  ( FIG. 8 ) and fastener openings  64  ( FIGS. 6 and 7 ). The first end cap  37  is coupled to the housing  33  with a fastener  67 , and the second end cap  38  is coupled to the housing  33  with a fastener  68 . In other embodiments, couplings between the components of the frame  36  may be by any effective means, such as but not limited to, welding, application of adhesives, clamping, snap fit components, or with other types of fasteners not specifically listed. 
     The threaded shaft  40  shown at least in part in each of  FIGS. 6-11  couples with and rotates in the frame  36 . In the illustrated embodiment, the frame  36  supports the threaded shaft  40  with rotatable couplings in the first end cap  37 , the second end cap  38 , and at the center strut  34 . One or all of the rotatable couplings may include a bushing, a bearing, or a close tolerance fitting of some operable type. The rotatable couplings may include components made from materials other than the materials of the first end cap  37 , the second end cap  38 , and at the center strut  34 , or may be formed as a part of these components. The threaded shaft  40 , or portions of the shaft, may be restricted from movement along a longitudinal axis of the threaded shaft  40  by fasteners (not shown) that extend through fastener openings  63  and fastener openings  64 , and through grooves  49  ( FIGS. 9-11 ) in the threaded shaft  40 . 
     The threaded shaft  40  may be a unitary piece in some embodiments. In other embodiments, such as the one shown in more detail in  FIGS. 9-11 , the threaded shaft  40  is composed of multiple components and interact to provide additional functionality to the transverse retractor  30  and surgical access instrument  1 . In either type of embodiment, a first portion  41  of the threaded shaft  40  may have right-hand threads that interact with a first carriage  31 , and a second portion  42  of the threaded shaft  40  may have left-hand threads that interact with a second carriage  32 . With such an arrangement, rotation of the threaded shaft  40  in a first rotational direction will result in the first carriage  31  and the second carriage  32  moving together, or toward one another, simultaneously. Rotation of the threaded shaft  40  in a second rotational direction opposite from the first rotational direction will result in the first carriage  31  and the second carriage  32  moving apart simultaneously. 
     A first receiver  71  for a rotational tool in the first portion  41  of the threaded shaft  40  is shown in  FIG. 6 . The first receiver  71  shown is an internal hexagonal shaped opening. Any other functional shape would be acceptable in addition to a hex shape. For example and without limitation, a triangular, square, or other polygonal shape, a star shape, a shape with re-entrant surfaces, and a rounded but non-circular shape would be acceptable. Additionally, in some embodiments an external receiver may be used that extends beyond the surface of the first end cap  37  so that it may be engaged by a rotational tool of any functional shape. 
     A second receiver for a rotational tool may be embodied in either or both internal receiver  72  and external receiver  73 , as illustrated in  FIGS. 7-9 . The internal receiver  72  shown is an internal hexagonal shaped opening. Any other functional shape would be acceptable in addition to a hex shape. For example and without limitation, a triangular, square, or other polygonal shape, a star shape or other shape with re-entrant surfaces, and a rounded but non-circular shape would be acceptable. The external receiver  73  illustrated is a hexagonal shaped component that extends beyond the surface of the second end cap  38  so that it may be engaged by a rotational tool. In addition to hex shaped, the external receiver may be of any functional shape, for example and without limitation, a triangular, square, or other polygonal shape, a shape with re-entrant surfaces, and a rounded but non-circular shape. 
     The threaded shaft  40  shown in  FIGS. 9-11  includes a central shaft  80  on a common axis and disposed through the first portion  41  of the threaded shaft  40  and the second portion  42  of the threaded shaft  40 . In the illustrated embodiment, the first portion  41  and the second portion  42  of the threaded shaft  40  are separate pieces. The central shaft  80  includes a central shaft receiver for accepting a rotational tool used to turn the central shaft  80 . In the embodiment shown, the first receiver  71  and internal receiver  72  serve as central shaft receivers for the central shaft  80 . In some embodiments, the central shaft receiver may extend outside of the coupling of the threaded shaft  40  with the frame  36  to allow particular rotation capabilities or other operation of the central shaft beyond the frame  36 . For the embodiment of  FIGS. 9-11 , the central shaft  80  may be translated along the common axis relative to the first portion  41  and the second portion  42  of the threaded shaft  40 . 
       FIGS. 9 and 10  show the central shaft  80  in a first position, and  FIG. 11  shows the central shaft in a second position relative to the first portion  41  and the second portion  42  of the threaded shaft  40 . In the first position, central shaft  80  is rotationally engaged with both the first portion  41  and the second portion  42  of the threaded shaft  40 . In the second position, central shaft  80  is rotationally engaged with the first portion  41  of the threaded shaft  40  but disengaged from the second portion  42  of the threaded shaft  40 . 
     A detent  39  is shown in  FIGS. 9-11  engaged with the central shaft  80  in two locations. In  FIGS. 9 and 10 , the detent  39  engages the central shaft  80  in a first indentation  81 . In  FIG. 11 , the detent engages the central shaft  80  in a second indentation  82 . The detent  39  is coupled to the housing  33  of the frame  36 . The detent  39  of the embodiment shown is biased toward the central shaft  80 . The central shaft  80  includes a first key  87  for rotationally engaging with the first portion  41  of the threaded shaft  40  and a second key  88  for rotationally engaging with the second portion  42  of the threaded shaft  40 . The first and second keys  87 ,  88  may be hexagonal shaped, as illustrated. Additionally, and without limitation, their shape may be a triangular, square, or other polygonal shape, a star shape, a shape with re-entrant surfaces, a rounded but non-circular shape, or any other shape or fitting capable of transferring torque. 
     In operation, when the detent  39  is in the first indention  81 , the first key  87  is engaged with a like shaped opening in the first threaded portion  41 , and the second key  88  is engaged with a like shaped opening in the second threaded portion  42 . Consequently, turning of any of the first receiver  71 , the internal receiver  72 , or the external receiver  73  will result in turning of both the first threaded portion  41  and the second threaded portion  42 , and the first carriage  31  and the second carriage  32  will move simultaneously. 
     The central shaft  80  may be translated along the common axis relative to the first portion  41  and the second portion  42  of the threaded shaft  40  by applying a force F to the central shaft  80 , as noted in  FIG. 10 .  FIG. 11  illustrates the result of applying adequate force F to the central shaft  80  to overcome the biasing force of the detent  39  and thereby moving the central shaft  80  to the second position such that the detent  39  is located in the second indentation  82  rather than the first indentation  81 . As seen in  FIG. 11 , the central shaft  80  is rotationally engaged with the first portion  41  of the threaded shaft  40  by engagement with first key  87 . However, the central shaft  80  is rotationally disengaged from the second portion  42  of the threaded shaft  40  at second key  88 . Consequently, turning of the first receiver  71  or the internal receiver  72  will result in turning the first threaded portion  41  and moving the first carriage  31 , but not in turning the second threaded portion  42  and moving the second carriage  32 . Turning of the external receiver  73  will result in turning the second threaded portion  42  and moving the second carriage  32 , but not in turning the first threaded portion  41  and moving the first carriage  31 . With this mechanism, it is possible to independently control either the first carriage  31  or the second carriage  32  from a single end of the transverse retractor  30 . This feature may be useful in expediently controlling the transverse retractor  30  without repositioning the device relative to a patient. 
     In the transverse retractor  30  shown in  FIGS. 6-9 , a first transverse retractor appendage  51  is coupled with the first carriage  31 . The first retractor appendage  51  has a length and lateral sides  58  along its length. The transverse retractor  30  also includes a second transverse retractor appendage  52  coupled with the second carriage  32 . The second transverse retractor appendage  52  has a length and lateral sides  59  along its length. The coupling between each of the transverse retractor appendages  51 ,  52  and respective carriages  31 ,  32  of the illustrated embodiment is a rotatable coupling. In some embodiments, pressing of a button  91  rotationally releases each transverse retractor appendage  51 ,  52 , relative to the respective carriages  31 ,  32  allowing for relative rotation of the retractor appendages  51 ,  52 . Releasing the button  91  may lock each transverse retractor appendage  51 ,  52 , relative to the respective carriages  31 ,  32  near a position of the transverse retractor appendage  51 ,  52  at the time its respective button  91  is released. Instrument hooks  93  on each of the transverse retractor appendages  51 ,  52 , are provided with some embodiments to facilitate attaching an instrument to apply rotational force to the transverse retractor appendages  51 ,  52 . Rotating the transverse retractor appendages  51 ,  52  may provide better access to a surgical site, including a larger subcutaneous working channel. 
     The first transverse retractor appendage  51  illustrated has a radius or curve about its longitudinal axis. The curve of the illustrated embodiment is a relatively small radius, but may be significantly enlarged in some designs of the invention. For example, the radius may be enlarged to produce a slightly curved appendage as illustrated in  FIGS. 2 and 3 . In other embodiments, the transverse retractor appendage may be substantially flat or planar to form a substantially flat blade. 
     The second transverse retractor appendage  52  illustrated has a radius or curve about its longitudinal axis. The curve of the illustrated embodiment is a relatively small radius, but may be significantly enlarged in some designs of the invention. For example, the radius may be enlarged to produce a slightly curved appendage as illustrated in  FIGS. 2 and 3 . In other embodiments, the transverse retractor appendage may be substantially flat or planar to form a substantially flat blade. 
     As is shown in combinations of  FIGS. 1 ,  2 , and  6 , the first retractor appendage  21 , the second retractor appendage  22 , the first transverse retractor appendage  51 , and the second transverse retractor appendage  52  are configured to be aligned substantially along their respective lengths and an access portal  99  to the surgical site is formed among the lateral sides  29 ,  9 ,  58 ,  59  of the first retractor appendage  21 , the second retractor appendage  22 , the first transverse retractor appendage  51 , and the second transverse retractor appendage  52 . 
     Another embodiment of a surgical access instrument  101  is illustrated in  FIG. 12 . The illustrated surgical access instrument  101  includes a flexarm retractor  110  couple with a transverse retractor  130 . The flexarm retractor  110  illustrated includes a base  111 . The base  111  of the embodiment shown is configured to couple with the transverse retractor  130  along a housing  133  of a frame  136  of the transverse retractor  130 . The coupling between the base  111  and the transverse retractor  130  may also be an interference fit or a fixed or pinned coupling in some embodiments. By way of example and without limitation, the coupling may be achieved by welding, may include an adhesive, may include a fastener such as a screw, pin, bolt, rivet, or the like, or may be accomplished through any other effective mechanism. 
     A rack  113  of the illustrated embodiment provides a connection between the base  111  and the first retractor appendage  121  through a bar  123 . The bar  123  extends away for the base  111  and terminates at the first retractor appendage  121 . The bar  123  shown is fixed to the base  111 . In other embodiments, the bar  123  may be slideably coupled to the base  111  so that the first retractor appendage  121  may be moved closer to or more distant from the surgical site relative to the base  111  by sliding the bar  123  relative to the base  111 . 
     The first retractor appendage  121  includes a length extending along its longitudinal axis and lateral sides  129  along its length. The first retractor appendage  121  illustrated has a radius or curve about its longitudinal axis. The curve of the illustrated embodiment has a relatively large radius, but may be significantly reduced in some designs of the invention. For example, the radius may be small to produce essentially a section of a tube. In other embodiments, the retractor appendage may be substantially flat or planar to form a substantially flat blade. 
     A flexible arm  115  is coupled to the base  111  at a proximal end  116  of the flexible arm  115 . A distal end  117  of the flexible arm  115  is movable relative to the base  111 . In the embodiment shown, multiple cannulated joints  118  interconnect with one another along a curvilinear path to form a continuous cannulated member. In some embodiments, the multiple cannulated joints  118  may interconnect with one another along a linear path. A tensile element (not shown) may be disposed through the cannula of the multiple cannulated joints  118 . The flexarm retractor  110  includes a control  127  in some embodiments attached to the tensile element to tighten and release the tensile element. The flexible arm  115  of the illustrated embodiment may have a free state and a locked state relative to the base  111 . The free state may exist when the tensile element is loosened and some or all of the cannulated joints  118  are rotatable relative to one another. Another example of a free state is where tension is applied to the tensile element to create some resistance between the cannulated joints  118 , but adequate lateral pressure to the flexible arm  115  will result in movement of the flexible arm  115  relative to the base  111 . A locked state may exist where significant tension is applied to the tensile element to prevent rotation or movement of the cannulated joints  118  relative to one another. In some embodiments, the second retractor appendage  122  may separately or in conjunction with the flexible arm  115  include a free state and a locked state as a result of tension applied to the tensile element or by other effective mechanisms. 
     In some embodiments, the control  127  also releases and locks the bar  123  relative to the base  111 . Therefore, by common activation of the control  127 , the first retractor appendage  121 , the flexible arm  115 , and the second retractor appendage  122  may all be switched between a free state and a locked state relative to the base  111 . In other embodiments, the bar  123  is independently movable relative to the base  111  and the tensile element is separately able to be tensioned. 
     The second retractor appendage  122  includes a length extending along its longitudinal axis and lateral sides  109  along its length. The second retractor appendage  122  illustrated has a radius or curve about its longitudinal axis. The curve of the illustrated embodiment has a relatively large radius, but may be significantly reduced in some designs of the invention. For example, the radius may be small to produce essentially a section of a tube. In other embodiments, the retractor appendage may be substantially flat or planar to form a substantially flat blade. 
     As is shown in  FIG. 12 , the first retractor appendage  121  and the second retractor appendage  122  are aligned substantially along their respective lengths. An access portal  199  to a surgical site is formed between lateral sides  129 ,  109  of the first retractor appendage  121  and the second retractor appendage  122 . 
     The transverse retractor  130  may be coupled to an operating table or other piece of surgical support structure through eyelets  195 . An assembly  135  includes a frame  136 , a threaded shaft  140  rotatably coupled with the frame  136 , a first carriage  131  coupled with the threaded shaft  140  that is configured to translate along the threaded shaft  140  when the threaded shaft is turned, and a second carriage  132  coupled with the threaded shaft  140  that is configured to translate along the threaded shaft  140  when the shaft is turned. The frame  136  illustrated includes a housing  133 , a center strut  134 , a first end cap  137 , and a second end cap  138 . The housing  133  of the illustrated embodiment is coupled to the center strut  134 . The first end cap  137  is coupled to the housing  133 , and the second end cap  138  is coupled to the housing  133 . Couplings between the components of the frame  136  may be by any effective means, such as but not limited to, welding, application of adhesives, clamping, snap fit components, or with any type of fastener. 
     The threaded shaft  140  shown couples with and rotates in the frame  136 . In the illustrated embodiment, the frame  136  supports the threaded shaft  140  with rotatable couplings in the first end cap  137 , the second end cap  138 , and at the center strut  134 . One or all of the rotatable couplings may include a bushing, a bearing, or a close tolerance fitting or some operable type. The rotatable couplings may include components made from materials other than the materials of the first end cap  137 , the second end cap  138 , and at the center strut  134 , or may be formed as a part of these components. 
     The threaded shaft  140  may be a unitary piece in some embodiments. In other embodiments, the threaded shaft  140  is composed of multiple components and interacts to provide additional functionality to the transverse retractor  130  and surgical access instrument  101  as, for example, detailed with regard to the transverse retractor  30  above. A first portion of the threaded shaft  140  may have right-hand threads that interact with a first carriage  131 , and a second portion of the threaded shaft  140  may have left-hand threads that interact with a second carriage  132 . With such an arrangement, rotation of the threaded shaft  140  in a first rotational direction will result in the first carriage  131  and the second carriage  132  moving together, or toward one another, simultaneously. Rotation of the threaded shaft  140  in a second rotational direction opposite from the first rotational direction will result in the first carriage  131  and the second carriage  132  moving apart simultaneously. 
     In embodiments of the transverse retractor  130 , various transverse retractor appendages may be coupled to one or both of the first carriage  131  and the second carriage  132 . Transverse retractor appendages  51 ,  52  detailed above are non-limiting examples of devices that may be used in conjunction with the first carriage  131  and the second carriage  132 . 
     Embodiments of the invention include a portal means for accessing a surgical site. The portal or access means may include a first retractor means for retracting tissue in a first direction. Additionally, the portal means may include a flexarm retractor means for retracting tissue in a second direction substantially transverse to the first direction. The flexarm retractor may further be capable of assuming a flexible state and a rigid state along its length in response to the actuation of a single control. 
     All or a portion of the surgical access instruments of embodiments of the disclosed invention may be made of any biocompatible material. For example and without limitation, materials of the surgical access instruments may include non-reinforced polymers, carbon-reinforced polymer composites, PEEK and PEEK composites, low density polyethylene, shape-memory alloys, titanium, titanium alloys, cobalt chrome alloys, stainless steel, ceramics and combinations thereof. Material of the surgical access instruments may be radiopaque or may be radiolucent. If radiolucent, the instruments may include markers placed in certain components of the instruments to provide for guidance of the instruments under radiographic imaging. 
     Another embodiment of the invention is a method of creating an access portal to a surgical site. The method includes introducing a first retractor into the surgical site such that the retractor is in a position to separate tissues along a first axis. The first retractor may include mechanisms for independently moving two retractor appendages or blades along the first axis. The method also includes introducing a flexarm retractor into the surgical site such that the flexarm retractor is in a position to separate tissues along a second axis that is substantially transverse to the first axis. The flexarm retractor of some embodiments includes a base, a first retractor appendage coupled to the base, a flexible arm coupled to the base at a proximal end of the flexible arm, and a second retractor appendage coupled to the flexible arm at a distal end of the flexible arm. The method further includes coupling the flexarm retractor with the first retractor, separating the first retractor appendage from the second retractor appendage to create an access portal to the surgical site, and actuating a control on the flexarm retractor to stiffen the flexible arm to fix the second retractor appendage in a desired location. In some embodiments, actuating the control on the flexarm retractor to stiffen the flexible arm also locks the first retractor appendage relative to the base. Embodiments of the method may further include operating the first retractor to separate tissues along the first axis. 
     Still another embodiment of the invention is a method of creating an access portal to a surgical site. The method includes introducing a retractor with two appendages into the surgical site such that the retractor is in a position to separate tissues along an axis. The retractor may include mechanisms for switching from a first state where one rotational control moves both appendages simultaneously together or apart along the axis to a second state where the one rotational control moves only one of the appendages along the axis. In some embodiments, the mechanism for switching between the first and second states requires application of a force to a portion of the retractor along the axis. In some embodiments, application of another force in a direction substantially opposite to the direction of the first force results in a return to the first state where one rotational control moves both appendages simultaneously together or apart along the axis. 
     Various method embodiments of the invention are described herein with reference to particular devices. However, in some circumstances, each disclosed method embodiment may be applicable to each of the devices, or to some other device operable as disclosed with regard to the various method embodiments. 
     Terms such as proximal, distal, near, lower, upper, lateral, and the like have been used herein to note relative positions. However, such terms are not limited to specific coordinate orientations, but are used to describe relative positions referencing particular embodiments. Such terms are not generally limiting to the scope of the claims made herein. 
     While embodiments of the invention have been illustrated and described in detail in the disclosure, the disclosure is to be considered as illustrative and not restrictive in character. All changes and modifications that come within the spirit of the invention are to be considered within the scope of the disclosure.