Patent Publication Number: US-2021169463-A1

Title: Method of using a surgical tissue retractor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/214442, filed Dec. 10, 2018, which is a continuation of U.S. patent application Ser. No. 15/602542, filed May 23, 2017, which is a continuation of U.S. patent application Ser. No. 15/204329, filed Jul. 7, 2016, which is a continuation of U.S. patent application Ser. No. 13/794470, filed Mar. 11, 2013. The contents U.S. patent application Ser. No. 13/794470, filed Mar. 11, 2013 are hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of surgery and more particularly to a retractor for use in inter alia surgery of the lower back. 
     BACKGROUND OF THE INVENTION 
     Retractors are surgical devices used to spread bodily tissues in order to allow a surgeon or surgical assistant to see and access a part of the body that is to be surgically treated. In general, retractors comprise a pair of jaws or blades that grip the bodily tissue and push it apart under the force generated by an actuator, such as a pair of scissor-like arms having a distal end and a proximal end. The proximal end generally defines a pair of handles and the distal end attaches to the pair of blades so that manipulation of the handles causes the blades to move apart from one another. Once an incision is made in the body to be operated on, the blades are inserted into the incision and the actuator is manipulated to move the blades of the retractor apart, thus spreading the tissue and providing an aperture through which the surgeon can access visualize the tissue to be surgically treated. One problem with this type of retractor is that the aperture size is generally limited by the size of the incision, meaning that a large aperture requires a relatively large incision. The drawback to this arrangement is that larger incisions result in the need for longer periods for healing of the incision. There is thus a need for a surgical retractor that is capable of creating a relatively large aperture using a relatively small incision, thereby reducing the invasiveness of the surgical procedure, post-operative healing times and patient discomfort. 
     SUMMARY 
     One embodiment comprises a system for creating an operative corridor in a human body, comprising: a probe, wherein the probe is configured to be placed through the tissues of a patient from the surface of the tissue to a location of interest; a retractor system, wherein the retractor system comprises retractor blades having an internal space, wherein the internal space is substantially the same shape as the probe such that the internal space will slip over the probe when the probe is inserted into the tissues of the patient. 
     Another embodiment comprises a method of accessing a spine. The method incldues forming an incision in tissue; placing a probe into the incision; engaging an end of the probe with an intervertebral disc space; positioning a mating retractor blade system over the probe; sliding the mating retractor blade system down and over the length of the probe; and activating the mating retractor blade system to open the mating retractor blade system to create an operative corridor. 
     Another embodiment comprises a method of accessing a surgery site that includes forming an incision in tissue; placing a probe into the incision; anchoring an end of the probe at the surgery site; positioning a mating retractor blade system over the probe; sliding the mating retractor blade system down the length of the probe; and activating the mating retractor blade system to open the mating retractor blade system to create an operative corridor. 
     Another embodiment comprises a method of accessing a human spine that includes forming an incision in tissue; inserting an endoscope into the incision, wherein the endoscope is configured to allow safe navigation to the spine; sliding a mating retractor system in a close configuration over the endoscope; sliding the mating retractor system down and over at least a portion of the endoscope into the incision in tissue; and ctivating the mating retractor system to create an operative corridor in the tissue. 
     Another embodiment comprise a retractor that includes a first blade assembly comprising a first blade rotatable about a first axis, a second blade rotatable about said first axis and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about said first axis. A second blade assembly includes at least a third blade rotatable about a second axis and optionally a fourth blade rotatable about said second axis and, when said fourth blade is present in said second blade assembly. An adjuster is in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis, wherein said second axis is different from said first axis. The retractor also includes means for moving said first blade assembly relative to said second blade assembly along a third axis that is not parallel to said first and second axes, wherein the first blade assembly moves while the second blade assembly remains substantially stationary. 
     Another embodiment comprises a retractor that includes a first blade assembly comprising a first blade rotatable about a first axis, a fixed second blade and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about said first axis; a second blade assembly comprising at least a third blade rotatable about a second axis wherein said second axis is different from said first axis; and wherein said first blade assembly is movable relative to said second blade assembly along a third axis that is not parallel to said first and second axes; wherein said first blade assembly is configured to detachably separate from said second blade assembly when said retractor is in an open configuration. 
     In certain embodiments, the retractor (surgical retractor) can comprise (a) a first blade assembly comprising a first blade rotatable about a first axis, a second blade rotatable about said first axis and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about said first axis; (b) a second blade assembly comprising at least a third blade rotatable about a second axis and optionally a fourth blade rotatable about said second axis and, when said fourth blade is present in said second blade assembly, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis, wherein said second axis is different from said first axis; and (c) a means for moving said first blade assembly relative to said second blade assembly along a third axis that is not parallel to said first and second axes. 
     Incorporation by Reference 
     All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: 
         FIG. 1  provides a perspective view of a retractor with a pair of blade assemblies in a closed and parallel configuration. 
         FIG. 2  provides a perspective view of a retractor, this time with the blades open in one direction along directional arrows c and d. Opening the retractor in this direction stretches the incision along its length. 
         FIG. 3  provides a perspective view of a retractor, now with the two blade assemblies open in separate directions from the first direction of opening. Opening the retractor blade assemblies stretches the incision open in a second direction that is different from, and essentially not parallel to, the first direction. 
         FIGS. 4, 5 and 6  provide exploded perspective views of a retractor, the handles being separated from the arm assembly and the blade assemblies being separated from the arm assembly. 
         FIGS. 7, 8 and 9  provide top views of the retractor. 
         FIGS. 10 and 11  provide close-up views of a blade. 
         FIG. 12  provides a perspective view of an arm assembly. 
         FIGS. 13-19  provide exploded views of a blade assembly, from which the assembly and operation of the blade assembly can be discerned. 
         FIGS. 23-25  show side views of a first blade of a blade assembly, while 
         FIGS. 26-28  show side views of a second blade of a blade assembly. 
         FIGS. 20-22  show various blades that may be employed in blade assemblies. 
         FIGS. 29-30  show side views of barrels of blade assemblies. 
         FIGS. 30 and 31  show the relationship between the angles of slots in the first blade and the second blade of the blade assembly. 
         FIGS. 32-35  show perspective views of a retractor of the invention in operation. A surgeon makes an incision having length L, into which the closed blade assemblies of the retractor are inserted. The surgeon then opens the retractor to create a lengthwise opening having length L′, wherein L′&gt;L. Finally the surgeon opens the blade assemblies to create a L′×W′ aperture. In some embodiments, the handles  24 ,  44  can be removed from the arm assembly to permit the surgeon even greater ability to see and operate on the tissue to be treated. 
         FIGS. 36A-36F  show the use of a probe to insert a retractor system to form an operative channel through the tissue of a patient to access a portion of the patient&#39;s spine. 
         FIGS. 37A-37D  show various embodiments of a probe system which can be used to insert a retractor system to form an operative channel through the tissue of a patient. 
         FIGS. 38A-38I  show various cross sections of a probe system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The retractor embodiments described herein provides advantages over the prior art retractors comprising a set of blades and an actuator, such as a set of scissor arms. Additional details of these embodiments can be found in U.S. Pat. No. 8,142,355 (issued on Mar. 27, 2012), which is hereby incorporated in its entirety herein. The retractor embodiments described herein can allowed the person skilled in the art to insert a relatively compact set of retractor blades into an incision having a short length. In some embodiments, the compact set of retractor blades are of such a size that they can be inserted within the incision so that they are snugly embraced by the side walls of the incision. Activation of an actuator causes the blades to move apart in a direction that is essentially parallel to the length of the incision. This causes the tissue to stretch in one direction, creating an opening having a length in that direction that is substantially longer than the incision. Once the retractor is opened in the first direction, the actuator may be locked open. Then a pair of adjusters on the blade assemblies may be manipulated to open the blade assemblies, thus pulling the incised tissue apart in directions that are not parallel to the incision. In some embodiments, these directions may be perpendicular, substantially perpendicular or oblique to the incision. Thus there is opened up an aperture that is substantially longer than the incision, and thus is substantially larger than would be possible using a prior art device. Thus in relative terms, the surgeon may use a smaller incision, and in some cases a much smaller incision, than would have been required with a prior art device. Moreover, removal of the retractor, e.g. by closing the blade assemblies, replacing the handles (if necessary), closing the arm assembly and removing the blade assemblies from the incision, causes the incision to relax back to a size that is much smaller than would have resulted from use of the prior art retractor. 
     In some embodiments, the handles, the blade assemblies or both are removable. In some embodiments, the blades of the blade assemblies may take on a variety of shapes and sizes. In some embodiments, a kit can include a plurality of retractors having blades of various sizes, shapes or both. In some embodiments, the kit comprises one or more sets of handles, one or more arm assemblies and two or more blade assemblies (optionally of varying blade sizes and/or shapes). In some embodiments, a kit includes a retractor of as described herein optionally more than two blades, at least two of which differ from one another in size, shape or both, and one or more pedicle screws for performing lumbar surgery. Thus, the embodiments described herein provides a retractor, a variety of surgical kits for performing surgery, especially back surgery, and methods of using the retractor to perform surgery, and especially back surgery. 
     The foregoing and further needs are met by embodiments, which provide (a) a retractor comprising: (a) a first blade assembly comprising a first blade rotatable about a first axis, a second blade rotatable about said first axis and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about said first axis; (b) a second blade assembly comprising at least a third blade rotatable about a second axis and optionally a fourth blade rotatable about said second axis and, when said fourth blade is present in said second blade assembly, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis, wherein said second axis is different from said first axis; and (c) a means for moving said first blade assembly relative to said second blade assembly along a third axis that is not parallel to said first and second axes. It is to be understood by one of ordinary skill in the art that, while at present a preferred embodiment uses a means for moving said first blade assembly relative to said second blade assembly employs two arms that are held parallel to one another by a means for stabilizing the arms, it is also possible for said means for moving said first blade assembly relative to said second blade assembly to be a pair of crossing arms joined to one another at a pivot point. In such cases, the blade assemblies move relative to one another along an arc. Nonetheless, their general direction of motion relative to one another, and the direction of motion that is of especial interest in the context of the present application, is along an axis that is generally defined by a line passing through the blade assemblies, e.g. at the point where each blade assembly is attached to its respective arm. In particular embodiments, the second blade assembly comprises a third blade, a fourth blade and an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis. In some such embodiments, the first and second axes may be substantially coplanar with one another. Indeed in some currently preferred embodiments, the first and second axes are not only coplanar but also substantially parallel to one another. In particular embodiments, the first and second axes are coplanar with, parallel to, or at some pre-determined skew angle with respect to one another. In some specific examples, the third axis is substantially perpendicular to the first axis, the second axis or both the first and second axes. In particular embodiments, the third axis is substantially perpendicular to both the first axis and the second axis. In some embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some specific embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, the retractor described herein possesses a means for locking said first and second blade assemblies in at least one predetermined position along said second axis. In some particular embodiments, two of said blades are of substantially different sizes in at least one dimension. In some specific embodiments, at least two blades of different sizes form part of the same blade assembly, while in other embodiments, two blades of different sizes form parts of different blade assemblies. In some particular embodiments, at least one of the first, second, third and, when present, forth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, Some embodiments include at least one removable blade assembly. In some specific embodiments, both blade assemblies are removable. 
     In some embodiments, a method (e.g. a method of surgery--in particular spinal surgery, e.g. in the lumbar region of the back) comprises the steps of: (a) providing a retractor comprising: (i) a first blade assembly comprising a first blade rotatable about a first axis, a second blade rotatable about said first axis and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about said first axis; (ii) a second blade assembly comprising at least a third blade rotatable about a second axis and optionally a fourth blade rotatable about said second axis and, when said fourth blade is present in said second blade assembly, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis, wherein said second axis is different from said first axis; and (iii) a means for moving said first blade assembly relative to said second blade assembly along a third axis that is not parallel to said first and second axes; (b) adjusting the first and second blades of the first blade assembly to be substantially parallel to each other to form a first closed blade assembly; (c) adjusting the third blade, and when present the fourth blade, of the second blade assembly to be substantially parallel to the first and second blades of the first blade assembly; (d) making an incision in a tissue of a body; (e) inserting said first blade assembly and said second blade assembly within the incision; (f) moving the first blade assembly away from the second blade assembly along said third axis and along the length of the incision so that the incision is stretched to create an opening longer than the incision; and (g) adjusting the first and second blades of the first blade assembly about said first axis to an open position, and, when said fourth blade of said second blade assembly is present, adjusting the third and fourth blades of the second blade assembly substantially about said second axis to an open position, thereby stretching the incision out from said third axis and creating an aperture in the tissue that is longer and wider than the incision. In some such embodiments, the second blade assembly comprises a third blade, a fourth blade and an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis. In some particular embodiments, the first and second axes are substantially coplanar with one another, substantially parallel to one another and/or substantially perpendicular to the third axis. The third axis is the line passing through the points at which the blade assemblies are joined to the arms of the retractor. As mentioned above, the person skilled in the art will recognize that when the arms are scissor-like arms that cross one another and are joined at a pivot point, the motion of the blade assemblies with respect to one another will trace out an arc. However, the direction of motion of the two blade assemblies with respect to one another will be essentially along the third axis. In any case, in particular embodiments, the first and second axes are coplanar with one another, parallel to one another and/or perpendicular to the third axis. In particular embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some particular embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, at least two of said blades are of substantially different sizes in at least one dimension (e.g. length, width or both). In some specific embodiments, said two blades of different sizes form part of the same blade assembly. In other specific embodiments, said two blades of different sizes form parts of different blade assemblies. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, the retractor further comprise a means for locking said first blade assembly and second blade assembly in a position apart from each other along said second axis. In some embodiments, the method further comprises removing at least a part of said means for moving the first and second blade assemblies toward and away from each other along the second axis. In some embodiments, the incision is made in the lumbar region of the back near the spine. In some embodiments, the method further comprises placing one or more pedicle screws in the spine of the body. In other embodiments, the method further comprises adjusting the first and second blade assemblies to closed positions and removing the retractor from the incision, thereby returning the incision to substantially the same shape and size as prior to retractor insertion. In still further embodiments, at least one blade assembly is removable. In specific embodiments, both blade assemblies are removable. 
     In some embodiments, a kit for performing an operation, includes: (a) a retractor comprising: (i) a first blade assembly comprising a first blade rotatable about a first axis, a second blade rotatable about said first axis and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about said first axis; (ii) a second blade assembly comprising at least a third blade rotatable about a second axis and optionally a fourth blade rotatable about said second axis and, when said fourth blade is present in said second blade assembly, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis, wherein said second axis is different from said first axis; and (iii) a means for moving said first blade assembly relative to said second blade assembly along a third axis that is not parallel to said first and second axes; and (b) at least one member of the group consisting of instructions for using the retractor to perform a surgical operation, scalpels, suture needles, pedicle screws, suture material, spinal implant material, spinal fusion rods, biocompatible adhesive and closure staples. In some embodiments, the second blade assembly of the retractor comprises a third blade, a fourth blade and an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis. In some embodiments, the first and second axes are substantially coplanar with one another. In specific embodiments, the first and second axes are coplanar with one another. In some embodiments, the third axis is substantially perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is substantially perpendicular to both the first axis and the second axis. In some embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, the retractor further comprises a means for locking said first and second blade assemblies in at least one predetermined position along said second axis. In some embodiments, two of said blades are of substantially different sizes in at least one dimension. In particular embodiments, two blades of different sizes form part of the same blade assembly. In some embodiments, two blades of different sizes form parts of different blade assemblies. In some embodiments, at least one of the first, second, third and, when present, forth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, at least one blade assembly is removable. In some specific embodiments, both blade assemblies are removable. 
     In some embodiments, a retractor comprises: (a) a first arm having a distal end and a proximal end; (b) a second arm having a distal end and a proximal end; (c) a first blade assembly, attached near the distal end of the first arm and comprising a first blade, a second blade and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about a first axis; (d) a second blade assembly attached near the distal end of the second arm and comprising at least a third blade rotatable about a second axis, optionally a fourth blade, and when the fourth blade is present, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis; and (e) an actuator adapted to move at least the distal ends of said first and second arms relative to each other along a third axis that is not parallel to the first and second axes. In some embodiments of the retractor, the second blade assembly comprises a third blade, a fourth blade and an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis. In some embodiments, the first and second axes are substantially coplanar with one another. In some embodiments, the first and second axes are coplanar with one another. In some embodiments, the third axis is substantially perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is substantially perpendicular to both the first axis and the second axis. In some embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, the retractor further comprises a means for locking said first and second blade assemblies in at least one predetermined position along said second axis. In some embodiments, at least two of said blades are of substantially different sizes in at least one dimension (e.g. length, width or both). In some embodiments, two blades of different sizes form part of the same blade assembly. In some embodiments, two blades of different sizes form parts of different blade assemblies. In some embodiments, at least one of the first, second, third and, when present, forth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, at least one blade assembly is removable. In some embodiments, both blade assemblies are removable. In some embodiments, the actuator comprises a stabilizer which maintains at least a portion of each of the first and second arms in an attitude substantially parallel to each other when the first and second arms are moved toward and away from each other. In some embodiments, the stabilizing member comprises a first crosspiece having first and second ends, a second crosspiece having third and fourth ends, the first and second crosspieces being connected to each other by a pivot, the first end of the first crosspiece being connected to the first arm by a pivot, the second end of the first crosspiece being slidably connected to the second arm, the third end of the second crosspiece being connected to the second arm by a pivot and the fourth end of the second crosspiece being slidably connected to the first arm. In some specific embodiments, the first end of the first crosspiece is connected to the first arm at a position distal to the slidable connection of the fourth end of the second crosspiece to the first arm. In some more specific embodiments, the third end of the second crosspiece is connected to the second arm at a position distal to the slidable connection of the second end of the first crosspiece to the second arm. In some embodiments, the retractor further comprises a lock adapted to reversibly hold said first and second arms apart from each other along the second axis. In some specific embodiments, the lock is a ratchet lock comprising a ratchet blade and a ratchet release. In some more specific embodiments, the ratchet lock holds the first arm and the second arm apart from each other along the second axis. In some embodiments, the actuator comprises a first handle connected to the proximal end of the first arm and a second handle connected to the proximal end of the second handle, wherein the first handle and the second handle are adapted to move the distal ends of the first and second arms toward and away from each other along the second axis. In some specific embodiments, the first and second handles are connected by a pivot. In some additional embodiments, the actuator further comprises a biasing member adapted to bias the actuator toward a preselected condition. In some specific embodiments, the biasing member is a biasing spring. In some embodiments, the biasing spring biases the distal ends of the first and second arms toward each other. 
     In some embodiments, a method (e.g. a surgical method for surgery on the spine, e.g. the lumbar region of the spine) includes the steps of: (a) providing a retractor comprising: (i) a first arm having a distal end and a proximal end; (ii) a second arm having a distal end and a proximal end; (iii) a first blade assembly, attached near the distal end of the first arm and comprising a first blade, a second blade and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about a first axis; (iv) a second blade assembly attached near the distal end of the second arm and comprising at least a third blade rotatable about a second axis, optionally a fourth blade, and when the fourth blade is present, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis; and (v) an actuator adapted to move at least the distal ends of said first and second arms relative to each other along a third axis that is not parallel to the first and second axes; (b) ensuring that the first and second blades of the first blade assembly are substantially parallel to each other to form a first closed blade assembly; (c) ensuring that the third blade, and when present the fourth blade, of the second blade assembly are substantially parallel to the first and second blades of the first blade assembly; (d) making an incision in a tissue of a body; (e) inserting said first blade assembly and said second blade assembly within the incision; (f) actuating the retractor such that said first blade assembly and second blade assembly are moved apart from one another along the second axis and the incision is stretched along the length of the incision to create an opening longer than the incision; and (g) adjusting the first and second blades of the first blade assembly along said first axis to an open position, and, when said fourth blade of said second blade assembly is present, adjusting the third and fourth blades of the second blade assembly substantially along said second axis to an open position, thereby stretching the incision along the first axis and creating an aperture in the tissue that is longer and wider than the incision. In some embodiments, the method optionally comprises adjusting the third and fourth blades of the second blade assembly to an open position. In some embodiments, the actuator comprises a means for locking the first and second arms in a position apart from each other along the second axis, wherein the method further comprises locking said first and second arms in a position apart from each other along the second axis. In some embodiments, the actuator further comprises a set of removable handles, the method optionally further comprising removing said set of removable handles from the first and second arms. In other embodiments, the incision is made in the lumbar region of the back near the spine. In further embodiments, the method further comprises placing one or more pedicle screws in the spine of the body. In some embodiments the method further comprises closing the first and second blade assemblies and removing the retractor from the incision, thereby returning the incision to substantially the same shape and size as prior to retractor insertion. 
     In some embodiments, a kit (e.g. a surgical kit, especially a spinal surgery kit, and most particularly a spinal surgery kit for surgery on the lumbar region of the spine. In some embodiments, the kit comprises: (a) a retractor comprising: (i) a first arm having a distal end and a proximal end; (ii) a second arm having a distal end and a proximal end; (iii) a first blade assembly, attached near the distal end of the first arm and comprising a first blade, a second blade and an adjuster in mechanical communication with the first and second blades and adapted to rotate the first and second blades relative to each other about a first axis; (iv) a second blade assembly attached near the distal end of the second arm and comprising at least a third blade rotatable about a second axis, optionally a fourth blade, and when the fourth blade is present, an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis; and (v) an actuator adapted to move at least the distal ends of said first and second arms relative to each other along a third axis that is not parallel to the first and second axes; and (b) at least one member of the group consisting of instructions for using the retractor to perform a surgical operation, scalpels, suture needles, pedicle screws, suture material, spinal implant material, spinal fusion rods, biocompatible adhesive and closure staples. In some embodiments, the second blade assembly comprises a third blade, a fourth blade and an adjuster in mechanical communication with the third and fourth blades and adapted to rotate the third and fourth blades relative to each other about said second axis. In some embodiments, the first and second axes are substantially coplanar with one another. In some embodiments, the first and second axes are coplanar with one another. In some embodiments, the third axis is substantially perpendicular to the first axis, the second axis or both the first and second axes. In some specific embodiments, the third axis is substantially perpendicular to both the first axis and the second axis. In some embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, the retractor further comprises a means for locking said first and second blade assemblies in at least one predetermined position along said second axis. In some embodiments, two of said blades are of substantially different sizes in at least one dimension. In some embodiments, at least two blades of different sizes form part of the same blade assembly. In some specific embodiments, two blades of different sizes form parts of different blade assemblies. In some other embodiments, at least one of the first, second, third and, when present, forth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, at least one blade assembly is removable. In some specific embodiments, both blade assemblies are removable. In some embodiments, the actuator comprises a stabilizer which maintains at least a portion of each of the first and second arms in an attitude substantially parallel to each other when the first and second arms are moved toward and away from each other. In some specific embodiments, the stabilizing member comprises a first crosspiece having first and second ends, a second crosspiece having third and fourth ends, the first and second crosspieces being connected to each other by a pivot, the first end of the first crosspiece being connected to the first arm by a pivot, the second end of the first crosspiece being slidably connected to the second arm, the third end of the second crosspiece being connected to the second arm by a pivot and the fourth end of the second crosspiece being slidably connected to the first arm. In some embodiments, the first end of the first crosspiece is connected to the first arm at a position distal to the slidable connection of the fourth end of the second crosspiece to the first arm. In some embodiments, the third end of the second crosspiece is connected to the second arm at a position distal to the slidable connection of the second end of the first crosspiece to the second arm. In some embodiments, the retractor further comprises a lock adapted to reversibly hold said first and second arms apart from each other along the second axis. In some specific embodiments, the lock is a ratchet lock comprising a ratchet blade and a ratchet release. In some more specific embodiments, the ratchet lock holds the first arm and the second arm apart from each other along the second axis. In some embodiments, the actuator comprises a first handle connected to the proximal end of the first arm and a second handle connected to the proximal end of the second handle, wherein the first handle and the second handle are adapted to move the distal ends of the first and second arms toward and away from each other along the second axis. In some embodiments, the first and second handles are connected by a pivot. In some embodiments, the actuator further comprises a biasing member adapted to bias the actuator toward a preselected condition. In some embodiments, the biasing member is a biasing spring. in some specific embodiments, the biasing spring biases the distal ends of the first and second arms toward each other. 
     In some embodiments, a retractor includes: (a) a first arm having a distal end and a proximal end; (b) a second arm having a distal end and a proximal end, at least said distal end of said first arm and said distal end of said second arm being movable toward and away from each other; (c) a first blade assembly attached near the distal end of the first arm, which comprises a first blade, a second blade and a means for moving said first and second blades relative to each other about a first axis to adopt at least an opened position and a closed position; (d) a second blade assembly attached near the distal end of the second arm, which comprises a third blade, a fourth blade and a means for moving said third and fourth blades relative to each other about a second axis different from said first axis; and (e) a means for moving at least said distal end of said first arm and said distal end of said second arm relative to one another along a third axis that is not parallel to said first and second axes. In some embodiments, the first and second axes are substantially coplanar with one another. In some specific embodiments, the first and second axes are coplanar with one another. In some embodiments, the third axis is substantially perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is substantially perpendicular to both the first axis and the second axis. In some embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some specific embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, the retractor further comprises a means for locking said first and second blade assemblies in at least one predetermined position along said second axis. In some embodiments, two of said blades are of substantially different sizes in at least one dimension. In some embodiments, two blades of different sizes form part of the same blade assembly. In some embodiments, two blades of different sizes form parts of different blade assemblies. In some embodiments, at least one of the first, second, third and, when present, forth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, at least one blade assembly is removable. In some embodiments, both blade assemblies are removable. In some embodiments, the means for moving at least said distal end of said first arm and said distal end of said second arm relative to one another along the second axis comprises a means for maintaining at least a portion of each of the first and second arms in an attitude substantially parallel to each other when the first and second arms are moved toward and away from each other. In some embodiments, the retractor further comprises a means for locking the first and second arms in at least one preselected position. In some embodiments, the means for moving at least said distal end of said first arm and said distal end of said second arm toward along said third axis comprises a removable means for moving said first arm and said second arm relative to each other along the second axis. In some embodiments, the removable means for moving said first arm and said second arm toward and away from each other further comprises a means for biasing the arms toward or away from each other. 
     In some embodiments, a method (e.g. a method of surgery, such as spinal surgery, and in particular spinal surgery in the lumbar region of the back) includes the steps of: (a) providing a retractor comprising: (i) a first arm having a distal end and a proximal end; (ii) a second arm having a distal end and a proximal end, at least said distal end of said second arm and said distal end of said second arm being movable toward and away from each other; (iii) a first blade assembly attached near the distal end of the first arm, which comprises a first blade, a second blade and a means for moving said first and second blades relative to each other along a first axis to adopt at least an opened position and a closed position; (iv) a second blade assembly attached near the distal end of the second arm, which comprises a third blade, a fourth blade and a means for moving said third and fourth blades relative to each other substantially along the first axis to adopt at least an opened position and a closed position; and (v) a means for moving at least said distal end of said first arm and said distal end of said second arm relative to one another along a second axis; (b) ensuring that the first and second blades of the first blade assembly are substantially parallel to each other; (c) ensuring that the third and fourth blades of the second blade assembly are substantially parallel to each other and to the first and second blades of the first blade assembly; (d) making an incision in a tissue of a body; (e) inserting said first blade assembly and said second blade assembly within the incision; (f) actuating the retractor such that said first blade assembly and second blade assembly are moved apart from one another along the second axis and the incision is stretched along the length of the incision to create an opening longer than the incision; and (g) adjusting the first and second blades of the first blade assembly along said first axis to an open position, and, when said fourth blade of said second blade assembly is present, adjusting the third and fourth blades of the second blade assembly substantially along said second axis to an open position, thereby stretching the incision along the first axis and creating an aperture in the tissue that is longer and wider than the incision. In some embodiments, the actuator comprises a means for locking the first and second arms in a position apart from each other along the second axis, the method optionally further comprising locking said first and second arms in a position apart from each other. In some embodiments, the actuator further comprises a set of removable handles, optionally further comprising removing said set of removable handles from the first and second arms. In some embodiments, the incision is made in the lumbar region of the back near the spine. In some embodiments, the method further comprises placing one or more pedicle screws in the spine of the body. In some embodiments, the method further comprises closing the first and second blade assemblies and removing the retractor from the incision, thereby returning the incision to substantially the same shape and size as prior to retractor insertion. 
     The in some arrangements a kit can include (a) a retractor comprising: (i) a first arm having a distal end and a proximal end; (ii) a second arm having a distal end and a proximal end, at least said distal end of said first arm and said distal end of said second arm being movable toward and away from each other; (iii) a first blade assembly attached near the distal end of the first arm, which comprises a first blade, a second blade and a means for moving said first and second blades relative to each other along a first axis to adopt at least an opened position and a closed position; (iv) a second blade assembly attached near the distal end of the second arm, which comprises a third blade, a fourth blade and a means for moving said third and fourth blades relative to each other substantially along the first axis to adopt at least an opened position and a closed position; and (v) a means for moving at least said distal end of said first arm and said distal end of said second arm relative to one another along a second axis; and (b) at least one member of the group consisting of instructions for using the retractor to perform a surgical operation, scalpels, suture needles, pedicle screws, suture material, spinal implant material, spinal fusion rods, biocompatible adhesive and closure staples. In some embodiments, the first and second axes are substantially coplanar with one another. In some embodiments, the first and second axes are coplanar with one another. In some embodiments, the third axis is substantially perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is substantially perpendicular to both the first axis and the second axis. In some embodiments, the third axis is perpendicular to the first axis, the second axis or both the first and second axes. In some embodiments, the third axis is perpendicular to both the first and second axes. In some embodiments, the retractor of the kit further comprises a means for locking said first and second blade assemblies in at least one predetermined position along said second axis. In some embodiments, at least two of said blades are of substantially different sizes in at least one dimension. In some embodiments, at least two blades of different sizes form part of the same blade assembly. In some embodiments, two blades of different sizes form parts of different blade assemblies. In some embodiments, at least one of the first, second, third and, when present, forth blades is a comb-shaped blade. In some embodiments, at least one of the first, second, third and, when present, fourth blades is a substantially flat blade. In some embodiments, at least one blade assembly is removable. In some embodiments, both blade assemblies are removable. In some embodiments, the means for moving at least said distal end of said first arm and said distal end of said second arm relative to one another along the second axis comprises a means for maintaining at least a portion of each of the first and second arms in an attitude substantially parallel to each other when the first and second arms are moved toward and away from each other. In some embodiments, the retractor of the kit further comprises a means for locking the first and second arms in at least one preselected position. In some embodiments, the means for moving at least said distal end of said first arm and said distal end of said second arm toward along said third axis comprises a removable means for moving said first arm and said second arm relative to each other along the second axis. In some embodiments, the removable means for moving said first arm and said second arm toward and away from each other further comprises a means for biasing the arms toward or away from each other. 
     In some embodiments, a retractor blade assembly, includes: (a) a first blade having attached thereto a first barrel, the first barrel having a wall circling an axis and defining a first lumen, a first channel in the wall having a first slope with respect to the axis and a second channel in the wall having a second slope with respect to the axis and having C 2  symmetry about the axis with respect to the first slope, (b) a second blade having attached thereto a second barrel, the second barrel having a wall circling an axis and defining a second lumen, a third channel in the second wall having a third slope at a third angle with respect to the axis, and a fourth channel in the second wall having a fourth slope at a fourth angle with respect to the axis, the slope of the third angle being opposite in sign with respect to the axis to that of the first angle and the fourth channel having C 2  symmetry about the axis with respect to the third channel, wherein the first barrel fits within the second lumen of the second barrel such that the first and third channels intersect to form a first gap and the second an fourth channels intersect to form a second gap; (c) a cylindrical plunger having an axis, an outer surface, a first end and a second end, the first end having a hole through and at a right angle to the plunger axis, and the second end having a screw thread cut into the surface of the plunger, the cylindrical plunger fitting within the first lumen of the first barrel such that said hole aligns with the first gap and the second gap and the hole, first gap and second gap forming a passage; (d) a rod fitting through the passage such that movement of the plunger along the axis causes the first barrel to rotate in a first direction and the second barrel to rotate in a second direction opposite the first direction; (e) a holder possessing a third lumen, wherein the second barrel fits within the third lumen; and (f) a nut having an internal screw thread and fitting over the end of the plunger; whereby rotation of the nut causes the internal screw thread of the nut to engage the plunger screw thread and causes the plunger to move along its axis, thereby causing the first and second barrels to rotate about the axis in opposite directions. In some embodiments of the blade assembly the third angle is opposite in sign and congruent with the first angle and the fourth angle is opposite in sign and congruent with the second angle. In some embodiments of the blade assembly at least the first angle has a magnitude with respect to the axis of less than about 75.degree.. In some embodiments of the blade assembly, each angle has a magnitude with respect to the axis of less than about 75.degree.. In some embodiments of the blade assembly each angle has a magnitude with respect to the axis of about 20.degree. to about 70.degree. In some embodiments of the blade assembly, each channel has a first end and a second end and the nut and plunger are threaded so that the rod moves from the first end of the channels to the second end within 1 to 10 full rotations of the nut. In some embodiments of the blade assembly, the rod moves from the first end to the second end of the channels within 2 to 8 full rotations of the nut. In some embodiments of the blade assembly the rod moves from the first end to the second end of the channels within 3 to 6 full rotations of the nut. In some embodiments of the blade assembly, the rod moves from the first end to the second end of the channels within 4 to 6 full rotations of the nut. In some embodiments of the blade assembly, at least one blade is comb shaped. In some embodiments of the blade assembly, both blades are comb shaped. In some embodiments of the blade assembly, at least one blade is fan shaped. In some embodiments of the blade assembly, both blades are comb shaped. In some embodiments of the blade assembly, the holder is adapted to be removably affixed to an arm of a retractor. In some embodiments of the blade assembly, the holder is irreversibly affixed to an arm of a retractor. 
     Thus, the some embodiments provides a retractor as described herein, wherein at least one blade assembly is a retractor blade assembly, comprising: (a) a first blade having attached thereto a first barrel, the first barrel having a wall circling an axis and defining a first lumen, a first channel in the wall having a first slope with respect to the axis and a second channel in the wall having a second slope with respect to the axis and having C 2  symmetry about the axis with respect to the first slope, (b) a second blade having attached thereto a second barrel, the second barrel having a wall circling an axis and defining a second lumen, a third channel in the second wall having a third slope at a third angle with respect to the axis, and a fourth channel in the second wall having a fourth slope at a fourth angle with respect to the axis, the slope of the third angle being opposite in sign with respect to the axis to that of the first angle and the fourth channel having C 2  symmetry about the axis with respect to the third channel, wherein the first barrel fits within the second lumen of the second barrel such that the first and third channels intersect to form a first gap and the second an fourth channels intersect to form a second gap; (c) a cylindrical plunger having an axis, an outer surface, a first end and a second end, the first end having a hole through and at a right angle to the plunger axis, and the second end having a screw thread cut into the surface of the plunger, the cylindrical plunger fitting within the first lumen of the first barrel such that said hole aligns with the first gap and the second gap and the hole, first gap and second gap forming a passage; (d) a rod fitting through the passage such that movement of the plunger along the axis causes the first barrel to rotate in a first direction and the second barrel to rotate in a second direction opposite the first direction; (e) a holder possessing a third lumen, wherein the second barrel fits within the third lumen; and (f) a nut having an internal screw thread and fitting over the end of the plunger; whereby rotation of the nut causes the internal screw thread of the nut to engage the plunger screw thread and causes the plunger to move along its axis, thereby causing the first and second barrels to rotate about the axis in opposite directions. In some embodiments, the third angle is opposite in sign and congruent with the first angle and the fourth angle is opposite in sign and congruent with the second angle. In some embodiments, at least the first angle has a magnitude with respect to the axis of less than about 75.degree.. In some embodiments, each angle has a magnitude with respect to the axis of less than about 75.degree.. In some embodiments, each angle has a magnitude with respect to the axis of about 20.degree. to about 70.degree.. In some embodiments, each channel has a first end and a second end and the nut and plunger are threaded so that the rod moves from the first end of the channels to the second end within 1 to 10 full rotations of the nut. In some embodiments, the rod moves from the first end to the second end of the channels within 2 to 8 full rotations of the nut. In some embodiments, the rod moves from the first end to the second end of the channels within 3 to 6 full rotations of the nut. In some embodiments, the rod moves from the first end to the second end of the channels within 4 to 6 full rotations of the nut. In some embodiments, at least one blade is comb shaped. In some embodiments, both blades are comb shaped. In some embodiments, at least one blade is fan shaped. In some embodiments, both blades are comb shaped. In some embodiments, the holder is adapted to be removably affixed to an arm of a retractor. In some embodiments the holder is irreversibly affixed to an arm of a retractor. 
     In some embodiments, a kit includes a retractor as described herein, wherein at least one blade assembly comprises: (a) a first blade having attached thereto a first barrel, the first barrel having a wall circling an axis and defining a first lumen, a first channel in the wall having a first slope with respect to the axis and a second channel in the wall having a second slope with respect to the axis and having C 2  symmetry about the axis with respect to the first slope; (b) a second blade having attached thereto a second barrel, the second barrel having a wall circling an axis and defining a second lumen, a third channel in the second wall having a third slope at a third angle with respect to the axis, and a fourth channel in the second wall having a fourth slope at a fourth angle with respect to the axis, the slope of the third angle being opposite in sign with respect to the axis to that of the first angle and the fourth channel having C 2  symmetry about the axis with respect to the third channel, wherein the first barrel fits within the second lumen of the second barrel such that the first and third channels intersect to form a first gap and the second an fourth channels intersect to form a second gap; (c) a cylindrical plunger having an axis, an outer surface, a first end and a second end, the first end having a hole through and at a right angle to the plunger axis, and the second end having a screw thread cut into the surface of the plunger, the cylindrical plunger fitting within the first lumen of the first barrel such that said hole aligns with the first gap and the second gap and the hole, first gap and second gap forming a passage; (d) a rod fitting through the passage such that movement of the plunger along the axis causes the first barrel to rotate in a first direction and the second barrel to rotate in a second direction opposite the first direction; (e) a holder possessing a third lumen, wherein the second barrel fits within the third lumen; and (f) a nut having an internal screw thread and fitting over the end of the plunger; whereby rotation of the nut causes the internal screw thread of the nut to engage the plunger screw thread and causes the plunger to move along its axis, thereby causing the first and second barrels to rotate about the axis in opposite directions. 
     In some embodiments, a method as described herein uses a retractor as described herein, wherein at least one blade assembly is a retractor blade assembly, comprising: (a) a first blade having attached thereto a first barrel, the first barrel having a wall circling an axis and defining a first lumen, a first channel in the wall having a first slope with respect to the axis and a second channel in the wall having a second slope with respect to the axis and having C 2  symmetry about the axis with respect to the first slope; (b) a second blade having attached thereto a second barrel, the second barrel having a wall circling an axis and defining a second lumen, a third channel in the second wall having a third slope at a third angle with respect to the axis, and a fourth channel in the second wall having a fourth slope at a fourth angle with respect to the axis, the slope of the third angle being opposite in sign with respect to the axis to that of the first angle and the fourth channel having C 2  symmetry about the axis with respect to the third channel, wherein the first barrel fits within the second lumen of the second barrel such that the first and third channels intersect to form a first gap and the second an fourth channels intersect to form a second gap; (c) a cylindrical plunger having an axis, an outer surface, a first end and a second end, the first end having a hole through and at a right angle to the plunger axis, and the second end having a screw thread cut into the surface of the plunger, the cylindrical plunger fitting within the first lumen of the first barrel such that said hole aligns with the first gap and the second gap and the hole, first gap and second gap forming a passage; (d) a rod fitting through the passage such that movement of the plunger along the axis causes the first barrel to rotate in a first direction and the second barrel to rotate in a second direction opposite the first direction; (e) a holder possessing a third lumen, wherein the second barrel fits within the third lumen; and (f) a nut having an internal screw thread and fitting over the end of the plunger; whereby rotation of the nut causes the internal screw thread of the nut to engage the plunger screw thread and causes the plunger to move along its axis, thereby causing the first and second barrels to rotate about the axis in opposite directions. 
     The embodiments will now be further described with reference to the appended drawings. In  FIG. 1  there is shown a perspective view of a retractor  10  according to the present invention. The retractor  10  comprises a first arm  12 , having a distal end  14  to which is attached a first blade assembly  16 , comprising a first blade  18 , a second blade  20  and an adjuster  22 ; a second arm  32 , having a distal end  34 , to which is attached a second blade assembly  36  comprising a third blade  38 , a fourth blade  40  and an adjuster  42 . The retractor further comprises a first handle  24  having a distal end  28  and a proximal end  26  and a second handle  44  comprising a distal end  48  and a proximal end  46 . The two handles  24  and  44  are joined to one another by a pivot  50  and are spanned by a biasing spring  52 . The retractor  10  further comprises a ratchet lock  54 , which has serrations  56  that are adapted to engage an engagement member  58 , which together with the ratchet lock  54  serves to hold the retractor in a particular position. In  FIG. 1 , the retractor  10  is shown in the “closed” position, meaning that the two blade assemblies  16  and  36  are relatively close to one another, as are the two arms  12  and  32  and the distal ends  28  and  48  of the handles  24  and  44 , respectively. Depression of the proximal ends  26  and  46  of handles  24  and  44 , respectively, in the directions of the arrows a and b results in the blade assemblies  16  and  36  moving apart along the directional arrows c and d, thus causing retractor  10  to assume the configuration depicted in  FIG. 2 . Note that the directional arrows c and d define a geometric line passing through and joining axis f, which passes vertically through first adjuster  22 , and axis g, which passes vertically through second adjuster  42 . Hereinafter axis f may be referred to alternatively as a first axis, axis g may be referred to alternatively as a second axis and the axis defined by directional arrows c and d may alternatively be referred to as a third axis. The importance of these axes will become evident upon consideration of the remaining figures. 
     As can be seen in  FIG. 2 , the retractor  10  is in an “open” position, meaning that the first blade assembly  16  is relatively separated from the second blade assembly  36  along the third axis defined by directional arrows c and d. Thus, as the blade assembly  16  moves along line d and blade assembly  36  moves along line c they exert force in the direction of lines d and c, respectively. Insertion of the blade assemblies  16  and  36  into an incision (not shown) in a closed position (as in  FIG. 1 ) and opening the blade assemblies  16  and  36  to an open position (as in  FIG. 2 ) results in a stretching of the incision along the same axis defined by directional lines c and d. 
     It is noted that in the embodiment depicted in  FIGS. 1 and 2 , the actuator comprises a pair of arms  12  and  32  and a pair of handles  24  and  44 . The person skilled in the art will recognize that other embodiments of an actuator may be used. For example, scissor-like actuators are known in the clamp and retractor arts. In some such embodiments, the actuator comprises a pair of handles such as those depicted in  FIG. 1  having attached at the distal ends of the handles  28  and  48  a pair of blade assemblies  16  and  36  according to the illustrated embodiment. Moreover, while the handles  24  and  44  are depicted as being roughly parallel and joined together at a pivot point  50 , it is also within the skill in the art to use a pair of crossed (e.g. scissor-like) handles joined by a pivot. These and other embodiments of actuators are known in the art and contemplated as being within the scope of some aspects of the application. It is also to be understood that when the actuator is a scissor-like embodiment, the motion of blade assemblies  16  and  36  traverse an arc rather than a straight line upon opening of the retractor. Nevertheless, the spatial relationship of the two blade assemblies  16  and  36  can be conceptualized as changing along a line described by arrows c and d, which for the purpose of brevity is referred to herein as an axis, and in particular the third axis (axes f and g being the first and second axes). 
     The actuator comprising a pair of arms  12  and  32  and a pair of handles  24  and  44  as just described allows movement of both arms  12  and  32  about pivot  50  (as illustrated in  FIGS. 7 and 8 ). In some embodiments, the movement of one handle  24  toward the other handle  44  causes outward movement of only one arm while the other arm is left entirely fixed or moves a lessor amount. A retractor  10  system in which actuation of the system induces movement of only one arm (or reduced movement) of the retractor  10  can be particularly desirable in situations in which the retractor  10  will be used in close proximity to a delicate or sensitive anatomy. For example, if a surgeon desires to operate near a crucial nerve, the surgeon can use a retractor  10  with only one movable arm to protect the nerve by placing the fixed arm next to the nerve. Therefore, upon actuating the retractor  10 , only the arm opposite the nerve will move out to open the surgery site. In such a manner, the surgeon can effectively protect crucial structures while using the retractor  10  herein disclosed to access a nearby surgery site. In operation, the retractor  10  with a fixed arm operated substantially the same as other embodiments of the retractors  10  herein disclosed. For example, both systems can have blade systems  36  and  16  to further expand the surgery site. Thus, in one arrangement, the retractor can include a said first blade assembly that movable relative to a fixed second blade assembly and wherein said first blade assembly is configured to detachably separate from said second blade assembly when said retractor is in an open configuration. 
     Turning adjuster  22  about axis f in the direction of adjustment arrow h, and adjuster  42  about axis g in the direction of adjustment arrow j, results in opening of the blade assemblies  16  and  36 , respectively, as depicted in  FIG. 3 . As shown in  FIG. 3 , opening of the blade assembly  16  causes the blade  20  to exert force in the direction of direction arrow n, while blade  18  exerts force in the direction of direction arrow p. Likewise, opening of blade assembly  36  causes blade  40  to exert force in the direction of arrow k, while blade  38  exerts force in the direction of arrow m. Thus, after insertion of the closed blade assemblies  16  and  36  of a closed retractor  10  in an incision, opening the retractor  10  and then opening the blade assemblies  16  and  36 , the retractor  10  creates and maintains an aperture in the incised tissue that is both longer (i.e. dimensionally larger in the direction of the incision) and wider (i.e. dimensionally larger in a direction perpendicular or oblique to the direction of the incision) than the incision. It is to be understood that, while this description is especially apt where the incision is a straight line incision of about 0.1 to about 3 inches in length, it can apply to any shape of incision (e.g. an arc, a sinusoid, etc.) of any length. In particular embodiments of the applciation, the contemplated size of the incision is about 0.5 to 2 inches in length and the blade assemblies  16  and  36  are appropriately sized so that when the retractor  10  is closed the blade assemblies  16  and  36  fit lengthwise within the incision without requiring substantial stretching of the incised tissue prior to opening of the retractor  10 . Thus, in some embodiments, the blades  18 ,  20 ,  38  and  40  are sized to snugly fit within the incision when the blade assemblies are closed and the retractor is in a closed position. 
       FIG. 4  shows the device  10  with handle assembly  2 , comprising inter alia the handles  24  and  44 , separated from arm assembly  4 , comprising inter alia arms  12  and  32 . As can be seen in  FIG. 4 , the distal end  28  of handle  24  has a connecting pin  62  that fits within a connecting hole  64  on the first arm  12 , while the distal end  48  of handle  44  has a connecting pin  82  that fits within a connecting hole  84  in the arm  32 . In the depicted embodiment, the blade assembly  16  is removable from the distal end  14  of arm  12  and the blade assembly  36  is removable from the distal end  34  of arm  32 . As depicted, the blade assembly  16  can be connected to the arm  12  by inserting the projection  70  on the proximal end of holder  6  within orifice  68  in the distal end  14  of arm  12 . Likewise blade assembly  36  can be connected to arm  32  by inserting the projection  90  on the proximal end of holder  8  within the orifice  88  in the distal end  34  of arm  32 . 
       FIG. 5  depicts the arms  12  and  32  of the arm assembly  4  in an open position. In this position it can be seen that arms  12  and  32  are joined one to another by a pair of cross members  72  and  92 , which are joined together by a cross member pivot  100 . The cross member  72  is connected to arm  32  via a pivot  98  and to arm  12  via a rod  74 , which is moveable along the length of slot  76 . Likewise the cross member  92  is connected to arm  12  via a pivot  78 , and to arm  32  via a rod  94 , which is moveable along the length of slot  96 . One skilled in the art will recognize that the handle assembly  2  may be removed from the arm assembly  4  by removing the pins  62  and  82  from their respective holes  64  and  84 , resulting in the device  11  depicted in  FIG. 12 . This may occur at any time, e.g. prior to or during sterilization of the retractor  10  or during a surgical procedure once the retractor  10  has been opened. Removal of the handle assembly  2  during surgery may afford a member of the surgical team greater freedom of motion, an improved field of view or both. 
     As can be seen in  FIGS. 4 and 5 , the blade assemblies  16  and  36  can be removed from the arm assembly  4 . One may find it convenient to remove the blade assemblies  16  and  36  in order to expedite sterilization of the blade assemblies  16  and  36  and/or in order to exchange one or both blade assemblies  16  and  36  for other blade assemblies (e.g. different size blades, different configuration of blades, etc.) as discussed in more detail herein. 
       FIG. 6  is an exploded view of the retractor  10  with the blade assemblies  16  and  36  in an open position.  FIG. 7  is a view of retractor  10  from above in a closed position. In this view it can be clearly seen that the biasing spring  52  tends to bias the handles  12  and  32  apart. Also shown in this view are axes z and z′. In some embodiments, the blade assemblies  16  and  36  are adapted to rotate about the axes z, z′. In some embodiments, these added degrees of freedom permit the blade assemblies  16 ,  36  to be rotated outward so that they are farther apart at the lower parts of the blades than at the top. This allows the retractor  10  to create an even larger aperture without having to open the retractor  10  any farther.  FIG. 8  shows a top view of the retractor  10  in an open position. As shown in  FIG. 8  the ratchet  54  locks into position to hold the retractor  10  in an open position.  FIG. 9  shows the retractor  10  from above with the blade assemblies  16  and  36  in open positions.  FIGS. 10 and 11  are expanded views of blade assembly  36  in closed ( FIG. 10 ) and open ( FIG. 11 ) positions. 
       FIGS. 13-19  depict the assembly of an embodiment of a blade assembly  36 , which comprises blades  40  and  38 . Starting with  FIG. 13 , left opening blade subassembly  242  comprises blade  40 , which is connected to inner barrel  244 . The blade  40  comprises a plurality of teeth  254  connected to a bridge  252 , which in turn is connected to the inner barrel  244  such that rotating the inner barrel  244  about axis y to the left (clockwise) results in the teeth  254  also turning to the left (clockwise). The inner barrel  244  has a slot  246  cut into the upper portion  245  of the inner barrel  244 . Specifically, the upper portion  245  of the inner barrel  244  is that portion of the inner barrel  244  above the highest point at which the bridge  252  connects to the inner barrel  244 . Not shown in this view is a corresponding slot on the other side of barrel  244 , which is depicted in  FIGS. 29 and 30  as slot  247 , as discussed in more detail herein. The inner barrel  244  also has a lumen  248  through the inner barrel  244  and an engagement groove  250  circumscribing the inner barrel  244  above the slot  246 . 
     The right opening blade subassembly  202  comprises blade  38  comprising teeth  214  connected to a bridge  212 , which in turn is attached to the outer barrel  204 . The outer barrel  204  also possesses a lip  209 , which is a ledge about the lower portion of the barrel  204 . The bridge  212  is connected to the lip  209  such that rotation of the outer barrel  204  to the right (counterclockwise) about axis y results in the blade  38  also turning to the right (counterclockwise) about the axis y. The outer barrel  204  has a lumen  208  as well as a pair of slots  206 ,  207  cut into upper portion  205  of the barrel  204 . For the sake of clarity, the upper portion  205  of the outer barrel  204  is that portion of the outer barrel  204  above the lip  209 . The relationship of the slots  206 ,  207 ,  246  and  247  are depicted in  FIGS. 29-31 . 
     In  FIG. 29  there is depicted a side view of barrel outer barrel  204  and inner barrel  244 . For purposes of clarity, the barrels  244  and  204  are depicted without the additional components of the blade sub-assemblies attached, such as the blades. As can be seen in  FIG. 29 , slot  206  penetrates the upper portion  205  of outer barrel  204 . Slot  207 , shown in dotted lines, also penetrates the upper portion  205  of the outer barrel  204 , albeit on the opposite side of the outer barrel  204 . The outer barrel  204  also has a lip  209 , as mentioned above, which is below the upper portion  205  of the outer barrel  204 . Slot  246  penetrates the upper portion  245  of inner barrel  244 . Slot  247 , shown in dotted lines, also penetrates the upper portion  245  of the inner barrel  244 , albeit on the opposite side of the inner barrel  244 . As shown in  FIG. 30 , the inner barrel  244  and the outer barrel  204  have a common axis y, which passes vertically through the lumens (not shown) of the barrels  244  and  204 . Axis y thus forms a C 2  symmetry axis for slots  206  and  207 , as well as for slots  246  and  247 . More specifically, slot  206  forms an angle .alpha. with respect to the y axis, whereas the slot  207  forms an angle -.alpha. with respect to the axis y. Viewed from the vantage offered in  FIG. 29 , these angles .alpha. and -.alpha. have equal magnitude but opposite slope with respect to the axis y. In a like manner, the slot  246  forms an angle .beta., with respect to the axis y and the slot  247  forms an angle -.beta. with respect to the axis y. Thus slots  206  and  207  possess C 2  symmetry about the axis y, as rotation of inner barrel  244  about the axis y results in slots  246  and  247  equivalently changing places, as these slots possess congruent angles with respect to the y axis and are located  180 .degree. about the axis y from one another. Similarly, the slots  246  and  247  possess C 2  symmetry about the axis y, as rotation of the slots  246  and  247  about the y results in slots  206  and  207  changing places, as these slots are essentially identical with respect to the y axis. Note that .alpha. and -.beta. have similar orientation as do -.alpha. and .beta. This accounts for the opposite rotation of the barrels  204 ,  244 . Note also that in this embodiment angles .alpha., .beta., -.alpha. and -.beta. are essentially congruent, although in some embodiments of the application it may be desirable for .alpha. and -.alpha. to differ in magnitude from .beta. and -.beta. One of skill in the art would recognize that this latter arrangement would cause barrels  204  and  244  to rotate at different rates in opposite directions. Additionally, in the depicted embodiment it is presumed that the slots  206  and  207  are of equal length and start and end at essentially the same height as each other. However, it will be understood that the length of the slots  206  and  207  may be affected inter alia by the method used to form such features in the barrel  204  (e.g. machining, molding, etc.) and the assignment of C 2  symmetry to the slot pair  206 ,  207  is intended as an illustrative convenience. More specifically, it is intended that breaking the strict mathematical C 2  symmetry of the slots  206 ,  207  will not affect the operation of the application. Likewise breaking the strict mathematical C 2  symmetry of the slots  246 ,  247  will not affect operation of the device. Thus, lengthening or shortening one of slots  206  or  207 , moving one of the slots  206  or  207  up or down the barrel (along the axis y) or both changing the length and the position of one of the slots  206 ,  207  will not defeat the purpose of the device. Similarly, lengthening or shortening one of slots  246  or  247 , moving one of the slots  246  or  247  up or down the barrel (along the axis y) or both changing the length and the position of one of the slots  246 ,  247  will not defeat the purpose of the device. Thus, for the slot pair  206 ,  207  to satisfy the C 2  symmetry requirement for the purposes of the present device, it is sufficient that a portion of the slots  206 ,  207  satisfy the C 2  symmetry requirement. Likewise, it is sufficient for a portion of the slot pair  246 ,  247  to satisfy the C 2  symmetry requirement in order for the slot pair  246 ,  247  to satisfy the C 2  symmetry requirement for the purposes of the present device. However, in the currently preferred embodiment, the slot pair  206 ,  207  possess strict C 2  symmetry, as does the slot pair  246 ,  247 , within reasonable tolerances (e.g. about +/−2%). It is also noted that, while the slots  206 ,  207 ,  246  and  247  are depicted as having constant slope with respect to the axis y, it is possible and well within the skill in the art for the slots to have serpentine or other curved slopes with respect to the axis y so long as the C 2  symmetry requirement is satisfied through at least a portion of the slot pairs  206 ,  207  and  246 ,  247 . ( FIG. 31  shows the angles .alpha., -.alpha., .beta. and -.beta. independent of the barrels in order to provide easier visualization of their relationships to one another.) 
       FIG. 13  further depicts threaded plunger  260  having a bottom  266  and a top  268 . The plunger  260  has a set of screw threads  265  near the top  268  and a hole  262  at a right angle to and passing through the y axis. Also depicted is a holder  270  comprising a lumen  272  and a projection  274 . Additionally there is depicted an adjustment nut (or adjuster)  280  having internal threads  286  and two engagement holes  284 . Also depicted are a connector pin  292  and two engagement pins  294 . 
     As seen in  FIG. 14 , the left turning barrel  244  fits within the lumen  208  of the right turning barrel  204 . The plunger  260  then fits within the lumen  248  of the left turning barrel  244 , as depicted in  FIG. 15 . In this configuration, the left turning slot  246  crosses the right turning slot  206  forming a passage  261  through which, as depicted in  FIG. 16 , the connector pin  292  fits. As depicted in  FIG. 16 , the blades  38  and  40  are in a closed position with the connector pin  292  at the bottom of the slots  24 . In this configuration, it is seen that the two blades  38 ,  40  interlace to form a substantially planar blade pair, thus rendering the blade pair especially suitable for insertion within a small incision. One skilled in the art will recognize that moving the blades  38  and  40  apart will cause the barrels  244  and  204  to rotate in opposite directions, thereby causing connector pin  292  to rise along slots  246  and  206 , thereby causing the plunger  260  to rise along the y axis. Conversely, pulling the plunger  260  up along the y axis would cause the connector pin  292  to rise along the slots  246  and  206 , thereby causing the barrels  244  and  204  to rotate in opposite directions, thus causing the blades  40  and  38  to move apart. Conversely, starting with the connector pin  292  at the top of slots  246  and  206 , pressing the plunger  260  down will cause the connector pin  292  to move down the slots  246  and  206 , thereby causing the barrels  244  and  204  to rotate in opposite directions, thereby causing the blades  38  and  40  to rotate toward one another. As can be seen in  FIG. 17 , the assembly of barrel  244 , barrel  204  and plunger  260  fits through the lumen  272  of the holder  270  so that the threads  264  toward the end  268  of the plunger  260  are visible above the lumen  272  of the holder  270  and the lip  209  of the outer barrel  204  abuts the holder  270 . As can be seen in  FIG. 18 , the adjustment nut (adjuster)  280  fits over the end  268  of the plunger  260  and is held in place by pushing the engagement pins  294  through the engagement holes  284 . One of skill in the art will appreciate that the engagement pins  294  thus engage the engagement groove  250  on the barrel  244 , thereby permitting the adjustment nut  280  to freely turn about the y axis, but preventing the adjustment nut  280  from moving up or down along the y axis. The inner threads  286  of the adjustment nut  280  thus engage the outer threads  264  of the plunger  260 . Turning the adjustment nut  280  about the y axis in one direction causes the plunger  260  to move upward along the y axis, while turning the adjustment nut  280  in the opposite direction causes the plunger  260  to move downward along the y axis. As explained above, movement of the plunger  260  causes movement of the connector pin  292  up and down the y axis. Movement of the pin  260  in one direction creates force in one direction on the slots in one barrel and in the opposite direction on the slots in the other barrel. Thus, the adjustment nut  280  can be turned to open an close the blade assembly  36 .  FIG. 19  shows a fully assembled blade assembly  36  in the closed position. 
     The blades used in the blade assemblies may have a variety of configurations.  FIG. 20  shows an alternate embodiment of a blade assembly  300  according to the device, which comprises a holder  302  connected to a projection  308 , which is adapted to reversibly insert into the end of an actuator arm (not shown). The blade assembly  300  further comprises an adjuster  304  and a plunger  306 . The adjuster  304  is threaded on the inside, just as the plunger  306  is threaded on its outer surface, so that turning the adjuster causes the plunger  306  to move up and down. The plunger  306  operates through the holder  302  to turn the blades  320 ,  330  in opposite directions as described in more detail with regard to  FIGS. 1-13  above. In particular, the plunger  306  operates to turn inner barrel  322  in the opposite direction to outer barrel  332  essentially as described above. Inner barrel  322  is connected to bridge  312  from which project teeth  316 . Together bridge  312  and teeth  316  form the blade  320 . Outer barrel  332  is connected to bridge  314  from which project teeth  318  and fan  334 . Together bridge  314 , teeth  318  and fan  334  form the blade  330 . 
     Another embodiment of a blade assembly  300  is shown in  FIG. 21 , where the blade  320  comprises fan  338 ; and blade  330  comprises fan  336 . As can be seen in  FIGS. 22-28 , blades  320 ,  330  can have a variety of lengths of bridges  312 ,  314 , teeth  316 ,  318 , etc. (In these figures, the same numbering is used as in  FIGS. 1-13 . 
     In some embodiments, contemplates kits comprising a retractor. In some embodiments, the kit comprises a single actuator (e.g. a removable handle and arm assembly as described herein and depicted in the figures, a scissor-like assembly, etc.) and a plurality of removable and exchangeable blade assemblies. In some embodiments, the kit comprises at least three blade assemblies having amongst the three blade assemblies at least two distinct blade configurations. In other embodiments, the kit comprises from 3 to 12 blade assemblies having amongst the several blade assemblies from 2 to 12 distinct blade configurations. In some embodiments, the kit comprises at least two pairs of identical or substantially similar blade assemblies. In other embodiments, the kit comprises from 2 to 10, especially about 2 to 5 such pairs of blade assemblies. The blade configurations that are represented in such kits can include comb-like blades, interlocking comb-like blades (as depicted e.g. in  FIGS. 1-12 ), fan-like blades (as depicted in  FIG. 21 ), combinations of toothed and fan-like blades (as depicted in  FIG. 20 ), etc. 
     It is noted that in some embodiments the threads  286  and  268  can be canted with respect to the y axis to provide mechanical advantage to the operator opening and closing the blade assembly  36 . In particular, the threads may be canted so that one full rotation of the nut  280  will result in the connector pin  292  rising from  1 / 10  to all the way from its lowest position to its highest position. In some embodiments, the user will be required to perform from about 1 to about 10 full rotations, especially about 2 to about 8 full rotations, and in particular about 2, 3, 4, 5, 6, 7 or 8 full rotations of the nut  280  to cause the connector pin to traverse the length of the slots  206  and  246 , thereby moving the blade assembly  36  from its fully open to its fully closed position or vice versa. 
     A method according to the an embodiment can be visualized by referring to  FIGS. 32-35 . In  FIG. 32 , there is depicted a retractor  10  comprising a pair of handles  24 ,  44  and a pair of blade assemblies  16 ,  36  as described in more detail herein. An incision I having a length L is made in a suitable tissue, such as the skin overlying or in proximity to the lumbar region of the spine. The blade assemblies  16 ,  36  are in a closed position and aligned relatively parallel to one another. In  FIG. 33 , the blade assemblies  16 ,  36  have been inserted into the incision I. Pressure on handles  24 ,  44  causes the retractor  10  to open: i.e. blade assemblies  16 ,  36  move apart from one another in the general directions of directional arrows c, d, respectively. As can be seen in  FIG. 34 , the incision I is stretched open in the direction of the directional arrows c and d so that it obtains a length L′ greater than length L of the incision. Turning the adjusters  22 ,  24  in the direction of the curved arrows about the axes f and g, respectively results in the opening of the blade assemblies  16 ,  36 , causing the incision Ito open as can be seen in  FIG. 35 . As can be seen in  FIG. 35 , the aperture A is opened having a length L′ and a width W′. The aperture A thus provides an access area of dimensions L′.times.W′ for surgical personnel to view the operating field, to pass instruments, sutures, implants and other surgical materials through the aperture. Reversal of the steps outlined in  FIGS. 32-35  results in a final incision I having substantially the same length L and essentially no width, just as the original incision I. By way of comparison, in order for a prior art device having a pair of blades to crease such an aperture, the incision I would have to have a length L′ and the blades would have to have a width of L′. Thus, the present embodiment permits the use of a much smaller incision to create the aperture. Thus, the present embodiment permits less invasive surgical methods, quicker and more comfortable recovery from surgery and potentially cost savings for the medical coverage provider. 
       FIGS. 36A-36F  illustrate a probe  400  and a method for its use in conjunction with the retractor  10 .  FIG. 36A  illustrates a probe  400  and a portion of a spine, including a first vertebra  440 , a second vertebra  450 , and a disc  460  disposed between the first vertebra  440  and the second vertebra  450 . The probe  400  can have a probe body  410 , a proximal end  413 , a distal end  412 , an anchor tip  430 , and a distal shoulder  420 . The anchor tip  430  can be disposed at the distal end  412  of the probe body  410 . The distal shoulders  420  can be located at the distal end  412  of the probe  400  at the base of the anchor tip  430 . In modified embodiments, the probe  400  can have a distal end of a different shape. For example, the distal end  412  can be formed without the shoulder  420  and/or without the tip  430  and/or one of both elements can be modified in shape. 
     In some embodiments, the probe  400  can be rectangular in horizontal cross section (i.e., the plane bisecting the probe  400  perpendicular to the axis formed by the proximal end  413  and the distal end  412 ). In other embodiments, the probe  400  can be circular in horizontal cross section or oval cross section.  FIG. 38A-381  illustrate some representative cross sectional shape the probe  400  can have, including: a circle (shown in  FIG. 38A ); an oval (shown in  FIG. 38B ); a triangle (shown in  FIG. 39C ); a flattened oval (shown in  FIG. 38D ); a thin flattened oval (shown in  FIG. 38E ); a rounded rectangle (shown in  FIG. 38F ); a thin rounded rectangle (shown in  FIG. 38G ); a rectangle (shown in  FIG. 38H ); and a thin rectangle (shown in  FIG. 381 ). In yet other embodiments, the probe  400  can be any other appropriate shape, including but not limited to square, triangular, and ellipsoid. A rectangular cross-sectional shape can include a shape in which the corners of the device are rounded and/or arrangements in which the adjacent sides are not exactly perpendicular (e.g., plus or minus 10 degrees, 5 degrees, 1 degrees or 0.1 degrees from perpendicular) and/or when the sides of the probe have ridges, bends that deviate 10%, 5%, 1% or 0.1% from the width or length of a side.  FIG. 37A and 37B  illustrate a probe  400  with circular cross section and a probe  400  with an oval cross section respectively. 
     In some embodiments, the probe  400  can be constructed out of a biocompatible metal, such as but not limited to stainless steel, titanium, and cobalt chrome moly. In other embodiments, the probe  400  can be constructed out of a biocompatible ceramic. In still other embodiments, the probe  400  can be constructed out of any stiff, biocompatible material, including such classes of materials as metals, ceramics, and polymers, or any combinations thereof. 
     In some embodiments, the probe  400  can have a vertical length (i.e., length from the distal end  412  to the proximal end  413 ) in the range of about 5-50 cm, about 6-40 cm, about 7-30 cm, about 7-20 cm and about 8-10 cm or any other range which is appropriate to allow the probe  400  to function as desired. In some embodiments, the probe  400  can have a width in its largest, non-vertical dimension, in the range of about 5 mm-5 cm, about 6 mm-4 cm, about 7 mm-3 cm, and about 8 mm-2 cm, including about 1.5 cm. 
     In some embodiments, the distal shoulders  420  can extend horizontally in from the edges of the probe  400  in the range of about 0.1-5 mm, about 0.2-4 mm, about 0.3-3 mm, about 0.4-2 mm, about 0.5-1 mm, and about 0.6-0.8 mm. In some embodiments, the external corners where the distal shoulders  420  meet the vertical edges of the probe  400  can be squared. In other embodiments, the external corners where the distal shoulders  420  meet the vertical edges of the probe  400  can be rounded or smoothed. In some embodiments, the distal shoulders  420  can be machined flat on the bottom (particularly in such embodiments in which the probe  400  is a shape other than rectangular). In other embodiments, the distal shoulders  420  can be sharpened across their entire length to form a blade along their entire length. In other embodiments, the distal shoulders can be are sharpened across only a portion of their length to form a blade along only a portion of their length. For example, in some embodiments, only half of each distal shoulder  420  is sharpened (e.g., either the half of the distal shoulders  420  abutting the anchor tip  430  or the half of the distal shoulders  420  abutting the edges of the probe  400 ). 
     In some embodiments, the anchor tip  430  can extend downward from the distal end  412  of the probe  400 . In some embodiments, the anchor tip  430  can be substantially triangular (illustrated in  FIG. 36A ). In other embodiments, the anchor tip  430  can be substantially parabolic. In other embodiments, the anchor tip  430  can be a small cylindrical member, such as a trocar. In yet other embodiments, the anchor tip  430  can be any shape which allows anchoring of the probe  400  in tissue. In some embodiments, the edges of the anchor tip  430  can be machined to be substantially smooth. In other embodiments, the edges of the anchor tip  430  can be sharpened to form a blade. 
     In some embodiments, at least a portion of the vertical edges of the probe  400  can be sharpened. In some of these embodiments, the portion of the edges of the probe  400  which are sharpened can be disposed near the distal end  412  of the probe  400 . As a representative example,  1 - 5 cm of the edges of the probe  400  extending up from the distal end  412  and distal shoulders  420  can be sharpened to form a blade to facilitate insertion of the probe  400  into corporeal tissue of a patient. 
     In operation, the probe  400  can be inserted into a patient, preferably into an anchorable location, such as a collagenous tissue, bone, or vertebral disc.  FIG. 36A  illustrates the probe  400  being inserted into a patient (not fully shown) toward the spine (only a first vertebra  440 , second vertebra  450 , and disc  460  are illustrated in this representative example). The probe  400  illustrated in  FIG. 36A  is a thin, blade like rectangular probe  400  with a triangular anchor tip  430  and squared corners where the distal shoulders  420  meet the edges of the probe  400 . The structure of the probe  400  can facilitate its passage through tissues of a patient which can run parallel to the flat surfaces of the probe. In operation, a physician can select a location in which he desires to use a retractor  10  to form an operative channel in the tissues of the patient (the spine will be used in this example for illustration purposes only). After the surgeon selects the location for retractor  10  placement, he can insert the probe  400  by placing the anchor tip  430  against the surface of the patient and applying pressure to the proximal end  413 . The physician can then continue to apply pressure, thereby pushing the probe  400  through the tissue of the patient, until the probe  400  is fully in place. In some embodiments, an imaging modality can be used during the insertion of the probe  400 . As a representative, non-limiting example, X-ray fluoroscopy can be used during insertion of the probe  400  to ensure correct placement. Any appropriate imaging modality can be used to monitor the placement of the probe  400 . In some embodiments, a surgeon can make an incision with another instrument, such as a scalpel, prior to the insertion of the probe  400 , into which the probe  400  is inserted. 
       FIG. 36B  illustrates the probe  400  fully in place in a patient. The probe  400  has been inserted into the side of the spinal column (here defined by a first vertebra  440 , a second vertebra  450 , and the disc  460  between them).  FIG. 36B  illustrates the placement of the probe  400  in a location in which the anchor tip  430  can anchor the probe  400 . As shown in  FIG. 36B , the probe  400  has been inserted into the patient until the anchor tip  430  has sunk at least some distance into the disc  460  between the first vertebra  440  and second vertebra  450 . The anchor tip  430  has sunk into the disc  460  up until the distal shoulders  420  of the probe  400 . The distal shoulders  420  serve in this example to limit the possible insertion depth of the anchor time  430  of the probe  400 . 
       FIG. 36C  illustrates a retractor  10  (as disclosed herein) and a placed probe  400 . The retractor  10  has blades as disclosed above which, when in their close conformation, fit substantially closely around the probe  400 . The blades of the retractor  10  can be any type of blade as described above, including but not limited to a comb style blade, a fan style blade, or a combination style blade. 
       FIG. 36D  illustrates the retractor  10  and placed probe  400  of  FIG. 36C  where the blades of the retractor  10  in their closed conformation have been placed around the probe  400  and slipped down around the probe  400  into the channel already formed by the probe  400  in the patient, to the spine.  FIG. 36D  shows the retractor  10  still in its closed conformation and the blades still in their closed conformation such that the blades substantially closely enclose the probe  400 .  FIG. 36E  illustrates the same retractor  10  of  FIG. 36D  where the retractor  10  has been engaged and the blades have been deployed (both as have been disclosed fully above) to pull open the incision formed by the insertion of the probe  400 . 
       FIG. 36F  illustrates the retractor  10  and blades in place prepared for physician access to the desired spinal location wherein the probe  400  has been removed for physician access. The probe  400  can allow a surgeon to easily and quickly insert a retractor  10  without cutting an incision all the way to the surgery site prior to inserting the retractor  10  into the desired location to access the surgery site. Rather, the surgeon can quickly and easily insert the probe  400  into the desired location, anchor the probe  400  using the anchor tip  430  in the desired location, slip the blades of the retractor  10  around the probe  400 , and then simply slip the retractor  10  into place at which point in time the retractor and blades can be engaged to open up the surgical site and the probe  400  may be removed. 
     In one embodiment, the probe  400  comprises at least one electrode, wherein the at least one electrode is capable of stimulating a nerve to provoke an electromyographic response in the nerve.  FIG. 37C  illustrates a probe  400  with an electrode  431  disposed at the distal end  412  of the probe  400  on the anchor tip  430 . In some embodiments, only one electrode is used. In other embodiments, a plurality of electrodes can be used, including about 1-10 electrodes, about 2-8 electrodes, about 3-6 electrodes and about 4-5 electrodes. In some embodiments, at least one electrode can be disposed on the anchor tip  430 . In some embodiments, at least one electrode can be disposed on the probe body  410 . The electrod  431  can be allowed to any of the embodiments described hering 
     In some embodiments, the probe  400  comprises an endoscope  499 , wherein the endoscope  499  can comprise an imaging element  432  at the distal end  412  of the endoscope  499 . In some of these embodiments, the endoscope  499  can be configured to both allow a surgeon to visualize the placement of the probe  400  as well as allow a surgeon to slide a retractor  10  down over the probe  400  and into place as described herein to create an operative channel. In some embodiments, the endoscope  499  can include an anchor tip  430 . Such an endoscope can be applied to any of the embodiments described herein. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.