Abstract:
The present invention provides methods and apparatus in which a surgical retractor comprises a plurality of mechanically coupled tissue retaining walls that are guided into position along one or more guides previously implanted into the patient. The walls are preferably coupled by pivots, so that separating some of the walls from one another opens an operating space. There are preferably two guides, which are driven or screwed into the pedicles of vertebrae, or other bone. Since practical considerations will usually mean that the guides are completely parallel to one another, the retractor has oversized channels to receive the guides. The channels are best disposed in a frame, which also serves to hold lock the walls apart. Various convenience features are contemplated including a web disposed between the walls, which expands as the walls are separated. Also contemplated are projections from near the bottoms of one or more of the walls, which can alternatively or additionally help to hold the underlying tissue in place.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 10/645,136, filed on Aug. 20, 2003, which claims priority to U.S. Provisional Application Ser. No. 60/433,343, filed on Dec. 13, 2002, the contents of each expressly incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the invention is surgical retractors.  
       BACKGROUND OF THE INVENTION  
       [0003]     Many types of surgical retractors are known. The simplest devices are tubular probes, or probes adapted with a paddle or other somewhat flatter surface. Recent embodiments of that concept are depicted in U.S. Pat. No. 6,206,826 to Mathews et al. (March 2001). More complicated retractors utilize scissors, bow string, or screw-jack expanders that operate against mating paddles. Those retractors have the advantage of being able to lock the paddles in place, leaving at least one of the surgeon&#39;s hands free for other actions. See e.g., U.S. Pat. No. 6,471,644 to Sidor (October 2002). Still other retractors are self opening, including Cosgrove et al., U.S. Pat. No. 6,162,172 (December 2000). All cited patents herein are incorporated herein by reference.  
         [0004]     While undoubtedly useful in many respects, none of the above-mentioned retractors are readily fixed in position relative to one or more bones. U.S. Pat. No. 5,027,793 to Engelhardt et al. (July 1991) addresses that need to some extent, by providing spikes on the bottom of a retractor wall, and further providing spikes that can be driven into the bone. The contemplated use is to resect the operating area down to the bone, position the retractor, and then pound both the retractor and the spikes into place.  
         [0005]     A problem remains, however, in that the resection required to properly position the retractor can cause considerable trauma to the overlying and surrounding tissues. Another problem is that multiple retractors are needed to retain tissue pushing into the operating area from different directions. The Engelhardt et al. retractor, for example, did not have to address that issue because the preferred application was acetabular surgery, in which the major encroachment was from gluteus muscles that are all substantially superior to the operating site.  
         [0006]     In spinal and some other surgeries these problems can be especially severe. Thus, there is still a need to provide methods and apparatus in which an operating space can be positioned and opened with respect to specific areas of bone, while reducing trauma to surrounding tissue.  
       SUMMARY OF THE INVENTION  
       [0007]     To that end the present invention provides methods and apparatus in which a surgical retractor comprises a plurality of mechanically coupled tissue retaining walls, which are guided into position along one or more guides previously implanted into the patient.  
         [0008]     Preferred embodiments utilize two main walls, and four smaller walls, one on each of the ends of the two main walls. In such embodiments all of the walls are coupled by pivots, such that the faces of the two main walls can be moved towards or apart from each other to open or close an operating space. The faces of at least the main walls are preferably flat, but can be any other suitable shape, including convex. The invention is particularly suited for operating on or near curved bony surfaces, and the bottoms of the walls can be compliant (i.e., advantageously adapted to fit and/or conform to the bone surface below).  
         [0009]     There are preferably two guides, which are driven or screwed into the pedicles of vertebrae, or other bone. The various guides can be implanted into different bones, or different areas of the same bone. Since practical considerations will usually mean that the guides are parallel to one another, the retractor has oversized channels to receive the guides. The channels can be circular in cross section, but are more preferably elongated into an oblong or other slotted shape.  
         [0010]     The channels are best disposed in a frame, which also serves to hold lock the walls apart. Any suitable devices can be used to move apart the main walls to open the operating space, including for example a simple wedge or T-bar, or a mechanism disposed on the frame. The frame can be held in place relative to the guides by wires, nuts, clamps, and so forth.  
         [0011]     Various convenience features are contemplated including a web disposed between the walls, which expands as the walls are separated. The web can be cut, torn, bent away, or otherwise manipulated to expose the tissue below. Also contemplated are projections from near the bottoms of one or more of the walls, which can alternatively or additionally help to hold the underlying tissue in place, and can similarly be removed in any suitable manner from the corresponding wall. The frame or other portion of the retractor can be transparent to aid in surgeon visualization.  
         [0012]     Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a perspective view of a retractor according to the inventive subject matter, in an open configuration;  
         [0014]      FIG. 2  is a perspective view of the retractor of  FIG. 1 , disposed in a closed configuration;  
         [0015]      FIG. 3  is a perspective view of the back and spine of a patient, in which finger dissection is being employed to locate a pedicle of a vertebra;  
         [0016]      FIG. 4  is a horizontal cross-sectional view of a vertebra, showing use of an awl to punch a guide hole into a pedicle;  
         [0017]      FIG. 5  is a horizontal cross-sectional view of the vertebra of  FIG. 4 , in which a screw is being screwed into the hole created in  FIG. 4 ;  
         [0018]      FIG. 6  is a perspective view of the back and spine of a patient in which the closed retractor of  FIG. 2  is being fitted onto the guides implanted into adjacent vertebrae;  
         [0019]      FIG. 7  is a perspective view of the back and spine of the patient of  FIG. 6  in which the retractor is being opened by an opening tool;  
         [0020]      FIG. 8  is a perspective view of the back and spine of the patient of  FIG. 6  in which the retractor has been opened, and the web is being removed to expose various fingers and the underlying tissue;  
         [0021]      FIG. 9  is a perspective view of the back and spine of the patient of  FIG. 6  in which the retractor has been opened, and various fingers (bottom tissue retainers) are being removed;  
         [0022]      FIGS. 10A-10B  are perspective views of another embodiment of a retractor in an open position and attached to a spine;  
         [0023]      FIG. 11A  is a top view of a retractor in a closed position that has been lowered over guides;  
         [0024]      FIG. 11B  is a top view of the retractors of  FIGS. 10A-10B ;  
         [0025]      FIG. 12A  is a top view of the retractor used in  FIGS. 10A-11B  in an open position;  
         [0026]      FIG. 12B  is a front view of the retractor of  FIG. 12A ;  
         [0027]      FIG. 13A  is a side view of an embodiment of a guide for use with the retractor of  FIGS. 10A-12B ;  
         [0028]      FIG. 13B  is a cross-sectional view of the guide of  FIG. 13A ;  
         [0029]      FIG. 14A  is a side view of another embodiment of a guide for use with the retractor of  FIGS. 10A-12B ;  
         [0030]      FIG. 14B  is a cross-sectional view of the guide of  FIG. 14A ;  
         [0031]      FIG. 15  is perspective view of an embodiment of a connector for use with the retractor of  FIGS. 10A-12B ;  
         [0032]      FIG. 16  is a perspective view of an embodiment of a spreader for use with a retractor; and  
         [0033]      FIG. 17  is a perspective view of another embodiment of a retractor frame. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]      FIG. 1  generally depicts a retractor  10 , having a frame  20 , major walls  32 A,  32 B and minor walls  34 , and a locking/opening mechanism  40 . The various walls  32 A,  32 B,  34  are coupled by six hinges  36 , and in the open position depicted in the figure cooperate to define an operating space  50 .  
         [0035]     The frame  20  can be any suitable size and shape according to the particular applications, with larger frames being generally more useful for larger incisions. For posterior lumber surgery on adult humans, the overall dimensions of an especially preferred frame are about 5.5 cm in depth, 3.5 cm in length, 3 cm in width. Frame  20  is preferably made from Delrin™, but can be made of any suitable material, especially a nontoxic polymer such as polyethylene. The frame  20  can advantageously be colored to reduce glare from operating room lighting, and some or all of the frame can be relatively transparent.  
         [0036]     Frame  20  generally comprises a handle portion  22  that includes the locking mechanism  40 , and a perimeter  24  around the operating space  50 . The locking mechanism  40  is shown as a ratchet, but all other suitable locking mechanisms are also contemplated, especially those that provide for a high degree of reliability and ease of operation. At least one of the walls  32 A,  32 B,  34  is preferably coupled to the perimeter  24  using a pin (not shown).  
         [0037]     Channels  26  are located on opposite sides of the perimeter  24 , and are each sized to receive one of the guides  172  (see  FIGS. 4-9 ). The system is designed to work with a wide range of pedicle screw or other bone fixation systems, and with various numbers of guides, regardless of the specific relationship between screw and guide. In addition, the passageways defined by the channels  26  should be oversized with respect to the outside diameters of the shafts of the guides  172  so that the channels  26  can receive guides  172  that are out of parallel or in some other manner not perfectly aligned with each other. In preferred embodiments the channels define a passageway having a diameter of about 5 to 15 mm, whereas the guides  172  (see  FIGS. 5, 6 ) preferably have a corresponding diameter of about 4 to 6 mm. All ranges set forth herein should be interpreted as inclusive of the endpoints.  
         [0038]     As with other components, the various walls  32 A,  32 B,  34  are preferably made of a biocompatible material, and here again they can have any suitable sizes and shapes, depending on the surgical site or sites for which they are intended. The currently preferred material for retractor walls is polypropylene. Walls  32 A,  32 B,  34 , for example, can be mostly rectangular in vertical cross-section as shown, with bottoms of at least the major walls  32 A,  32 B curved to accommodate specific bone shapes, such as that of the spinous processes of the vertebrae in spinal surgery. It is also contemplated that the bottoms of at least the major walls  32 A,  32 B can be pliable, to conform at least partially to projections and depressions of the underling bone. Walls  32 A,  32 B,  34  are depicted in the figures as having flat sides, but alternatives may be bowed outwardly (convex), inwardly (concave), or may have any other suitable horizontal cross-section.  
         [0039]     One or more of the walls (not shown) can even be inflatable, made out of balloons that define the opening. Of course, the walls  32 A,  32 B,  34  must be sturdy enough, and therefore thick enough, to withstand the expected forces placed upon them. On the other hand the walls  32 A,  32 B,  34  are preferably not so thin that they would cut into the tissue below during deployment. On the other hand, the walls  32 A,  32 B,  34  should not be so thick as to significantly interfere with the size of the operating area. Preferred thickness is from about 3.5 mm to about 5 mm at the thickest point, tapering down to a thickness of 1.5 mm-3 mm at the bottom of each wall. The walls can also be nested in any suitable manner, which simply means that a portion of one wall extends around a portion of another wall.  
         [0040]     The hinges  36  are shown as continuations of the walls  32 A,  32 B,  34 . Indeed all of the walls and hinges can be molded as a single piece, with each of the hinges  36  being formed as an especially thin edge of a wall. This is effectively a “living hinge” that can handle multiple openings, using material properties of polypropylene. All other suitable configurations of hinges are also contemplated. For example, instead of four minor walls  34 , the major walls  32 A,  32 B could be coupled by only a single outwardly bowed, flexible piece (not shown) at each end. Certainly the total number of walls can be greater or less than 6.  
         [0041]     The term “wall” is used herein in a very broad sense, to mean any sort of tissue retaining barrier, generally longer than tall, and considerably taller than thick. Retractor  10  could thus be termed a “linear retractor” to distinguish it from point retractors that are basically pen-shaped probes. But neither the retractor as a whole nor any of the walls are necessarily linear. The term certainly does not require that the wall be so thin as to constitute a cutting blade. Nor does the term “wall” require that the sides thereof be completely patent. The sides of the walls may be pitted or indented as would occur if the sides had a mesh coating (not shown), and the sides may even have through holes (not shown).  
         [0042]     Locking/opening mechanism  40  is shown as a typical ratcheting type mechanism, with teeth  44 , and having a release  46 . Frame  20  can have both a locking mechanism and an opening mechanism (not shown), or either one by itself. There are numerous other locking and/or opening mechanisms known to the field, and presumably others will become known in the future. It is contemplated that any suitable locking and/or opening mechanisms can be used.  
         [0043]     Operating space  50  will be larger or smaller depending on the sizes and shapes of the walls, and the extent to which the walls are separated out from one another. Preferred area of the operating space  50  is between 7 cm 2  and 14 cm 2 .  
         [0044]      FIG. 2  generally depicts the retractor  10  of claim  1 , disposed in a closed configuration. The terms “closed” and “open” with respect to configurations of the retractor  10  are relative. Thus, closed merely means substantially closed, but does not require complete closure, so that the walls  32 A,  32 B are juxtaposed. In a closed position the walls  32 A,  32 B may well be separated by up to 1 mm or more. Similarly, in a contemplated open configuration, walls  32 A,  32 B would likely be separated by at least 1.5 cm, but may be separated by up to 2.3 cm or more.  
         [0045]      FIG. 3  generally depicts a portion of the spine  100  of a patient, in which the paraspinous muscles are designated schematically by semitransparent bands  110 ,  112 , respectively. The spine  100  includes vertebrae  120 , each of which includes transverse processes  122 , spinous processes  124 , and pedicles  126 . An incision  130  has been made, and a finger  142  of hand  140  is being used to dissect through the muscle and locate one of the pedicles  126 . Of course a wedge, probe or other tool could be use in place of or in addition to the finger  142  to locate the pedicles.  
         [0046]      FIG. 4  generally depicts cannula  150  that positions an awl or probe  152  for use in producing a hole  160  in the pedicle  126 . The awl  152  can be manually pushed or otherwise forced through the cortex  127  of the pedicle. Cannula  150  is preferably made of radiolucent material such as plastic or carbon fiber, while awl and probe  152 , and other tool attachments and inserts are all preferably made of metal such as surgical steel, titanium, or other durable, radio opaque material. Positioning the cannula  150  can be aided by fluoroscopy or other visualization technique.  
         [0047]     In preferred methods, the awl  152  is withdrawn, and a longer, thinner probe (not shown) is inserted through the pedicle  126  into the softer medulla  128  of the body  129  of the vertebra  120 . The longer pin is then withdrawn, and in  FIG. 5 a  screwdriver  176  is used to insert a screw  174 . The screw has a head  170 , which holds a guide  172  in place. The screwdriver  176  is then removed, leaving the screw  174  implanted into the vertebra  120 , and guide  172  rotatably attached to the top of screw  174 . The process is repeated to insert another guide  172  into another area of bone, which in the case of spinal surgery is most likely the pedicle of an immediately superior or inferior vertebra on the same side. In other surgeries (not shown), the second, or possibly even a further guide, can be inserted into a different location of the same bone as received the first guide.  
         [0048]     In  FIG. 6  the guides  172  that are implanted into adjacent vertebrae  120  have been inserted into the channels  26  of the closed retractor  10 . Those skilled in the art will realize that the channels can have other configurations besides those shown in the drawing, and can be multi-level rather than simply a single level.  
         [0049]     In  FIG. 7  the retractor  10  is being opened by an expander  180 , which is manually inserted between the opposing walls to produce and widen a gap between them. In this figure the expander generally comprises a wedge with a handle. The expander  180  is preferable over using unassisted fingers because it involves a mechanical advantage. Alternatively, the retractor can be opened using a thumb and fingers-opposing force method using the handle  22  and frame  20 . There are numerous alternatives which may or may not involve any mechanical advantage, including for example a T handle coupled to a shaft and a cam (not shown).  
         [0050]     In  FIG. 8  the retractor  10  has been opened to reveal a web  12  positioned between walls  32 A,  32 B and  34 . The web  12  is preferably a thin, flexible sheet of latex or other biocompatible plastic, which can be easily cut, ripped, or in some other manner disrupted to expose various retaining fingers  14  and the underlying tissue  105 . Web  12  is shown as covering the entire floor of the operating space  50 , but it could alternatively cover a lesser space, and could extend between or among different walls. The fingers  14  are depicted as extending from or rotating out below the web  12 , but some or all of the fingers  14  could alternatively be positioned above the web  12 . Each of web  12  and fingers  14  are certainly optional.  
         [0051]     In  FIG. 9  the retractor  10  has been opened, and various fingers  14  are being removed. Such removal can be accomplished in any suitable manner, including by cutting (as with a scalpel or scissors), bending by hand or with a tool, and so forth. There may be wide fingers, narrow fingers, long or short fingers, closely spaced or widely spaced fingers, flat or rounded fingers, and so on (not shown). Where fingers are used, they are preferably molded as continuous extensions of the walls.  
         [0052]     Also shown in  FIGS. 8 and 9  are threads  190  the guides  172  can be at least partially threaded, and can thereby that receive wing nuts or other correspondingly threaded pieces  192  that assist in anchoring the frame  20  to the guides  172 . In alternative configurations one could use non-threaded lock down pieces such as finger clamps  193 . In especially preferred embodiments alternative templates (not shown) can be placed on top of the frame, and held in place using the wing nuts, finger clamps, or other hold-down devices. The frame can also be used to hold additional devices, such as suction or lighting, introduced into the field  50  and held in place by a coupling device on the frame  20 .  
         [0053]     Preferred methods of inserting a tissue retractor  10  into a patient involve the steps of providing a retractor  10  having paired tissue retracting surfaces (such as on walls  32 A,  32 B,  34 ) and first and second guide receiving areas (such as channels  26 ); percutaneously or otherwise implanting first and second guides (such as guides  172 ) into different areas of bone in the patient; then positioning upper ends of the first and second guides through the first and second guide receiving areas, respectively, then fully inserting the retractor down the guides and into the patient, effectively splitting the muscle; and finally moving the tissue retracting surfaces apart from one another to open the operating space. These methods are especially useful where one or more of the guides are screws, which are implanted into very specific anatomical structures such as the pedicles of vertebrae. The contemplated methods are also extremely useful in opening operating spaces overlying adjacent bones. Especially preferred methods optionally employ nuts, clamps, or other readily attachable and tightenable mechanisms to stabilize the retractor  10  on the guides.  
         [0054]     From the description above, it should now be apparent that the novel methods and apparatus disclosed herein turn the normal retracting procedure on its head. Instead of positioning the retaining wall or walls and then holding them in place by implanting spikes or posts into the bone, the present procedure implants the spikes or posts, and then uses them as guides to position the retaining wall(s).  
         [0055]     The advantages of turning the procedure around are significant. Among other things, this new procedure allows the surgeon to exactly position the retractor  10  at the intended operative site because the positioning can be done precisely with respect to underlying bony structures (e.g., the pedicle  126  of a vertebra). The screws are implanted where the surgeon wants them, and the guides  172 , being attached to the top of the screws guide the retractor down into the desired anatomy, splitting the muscles, and defining a operating site  50  within the walls  32 A,  32 B and  34 . After that the operating site  50  is opened, giving the surgeon the desired exposure needed to conduct the surgery., without excess retraction and resulting tissue destruction.  
         [0056]     Another advantage is that these new methods and apparatus speed up the procedure and makes more efficient use of resources relative to the prior art. Among other things, after the guides  172  and screws  174  are placed and the retractor  10  is attached and opened, there is no more need for fluoroscopy, which can be moved along to a different room.  
         [0057]     Still other advantages involve convenience and reduction in surgeon stress. The novel methods and apparatus make it mentally easier on the surgeon. After the screws  174  are in, in the first part of the procedure, everything else in terms of opening the operating site is fairly straightforward. This helps the surgeon relax mentally and physically.  
         [0058]     Another embodiment of a retractor  210  is shown in  FIGS. 10A-12B . As seen in the perspective views of  FIGS. 10A-10B , retractor  210  may be comprised of a frame  220  and a blade portion  230 , which may form an opening  212  used to perform surgical procedures therein. Blade portion  230  may also have an insertion portion configured to be at least partially inserted into a patient. Retractor  210  may be associated with a portion of a spine  100  via guides  240 ,  250  and connectors  260 . Connectors  260  may have an attachment portion  262  for selective attachment to the frame  220  via indentations  222 . Blade portion  230  may have at least one blade, and a plurality of blades may be separated by a hinge  232 . Guides  240 ,  250  may be (as in the embodiments shown in  FIGS. 10A-11B ) two different types of guides, or they may be the same types of guides. Guides  240 ,  250  may be associated with bones screws  270 , which may be inserted into the pedicle of a vertebrae  120 , and which may or may not have an attachment portion connected to the heads of such screws  270 .  
         [0059]      FIG. 11A  shows a top view of a retractor  210  slidably engaged with guides  240 ,  250 , before a connector  260  has been utilized. In this embodiment, blade portion  230  is in a closed configuration, and retractor  210  has been lowered toward the spine  100  over guides  240 ,  250 . Guides  240 ,  250  may be within the opening  212  created by the blades of blade portion  230 . Before connectors  260  are attached to guides  240 ,  250  and the frame  220 , retractor  210  may be slidably engaged with guides  240 ,  250 , such that the distance between retractor  210  and spine  100  may be altered to a desired distance.  
         [0060]      FIG. 11B  shows a top view of a retractor  210  in an open position, and fixedly associated with guides  240 ,  250  via connectors  260 . As can be seen in this embodiment, connectors  260  have been used to associate guides  240 ,  250  with frame  220 , and the blades of blade portion  230  have been opened to create a larger opening  212  than in  FIG. 11A . Guides  240 ,  250  are seen in this embodiment to engage (either directly or indirectly) bone screws  270 . Preferably, guides  240 ,  250  can assume a variety of angulations in relation to a bone screw  270 . This may be achieved by providing a polyaxial association between guides  240 ,  250  and a bone screw  270 . Bone screws  270  may be introduced into the body and into engagement with the body by numerous suitable methods, including utilizing a cannula and/or dilator to access the desired insertion location by creating an access port.  
         [0061]     In use, and in reference to  FIGS. 11A-11B , guides  240 ,  250  are attached to bone screws  270 , such that guide  240 ,  250  project away from the spine  100 . While two guides  240 ,  250  are shown, it is contemplated, that one, three, or more guides  240 ,  250  may be utilized. Moreover, although two bone screws  270  are shown for use with retractor  210 , it is expressly contemplated that one, three, or more bone screws  270  may be used. The number of guides  240 ,  250  may be less, the same, or more than the number of bone screws  270 . As stated above, guides  240 ,  250  preferably are polyaxially and/or pivotably associated with a bone screw  270 .  
         [0062]     After guides  240 ,  250  are attached to bone screws  270 , retractor  210  may be lowered over the guides  240 ,  250  such that the guides  240 ,  250  pass through the opening  212  of blade portion  230 , and project upwardly away from the retractor  210 . Preferably, blade portion  230  is in a closed position when the retractor  210  is lowered over guides  240 ,  250 . As stated above, it may be preferable to do so to create a generally linear leading edge of the blade portion  230  to increase ease of insertion into an incision.  
         [0063]     Once retractor  210  has been lowered to a desired relationship relative to the spine  100  or other body tissue, a user may slide a connector  260  over each guide  240 ,  250  such that connector  260  is lowered to a connecting position. In the embodiment shown in  FIGS. 10A-11B , connector  260  connects a guide  240 ,  250  to frame  220  by associating an attachment portion  262  with an indentation on the frame  222 , and concurrently releasably fixing the connector  260  with a guide  240 ,  250 . Other embodiments of a connector  260  (other than the embodiment shown herein, and in detail in  FIG. 15 , infra) are expressly contemplated, and will be appreciated by those skilled in the art.  
         [0064]     After connectors  260  are in place, the blade portion  230  of retractor  210  may be opened to enlarge opening  212  to a desired amount. Blade portion  230  may be opened similar to the methods described above. Preferably, blade portion  230  is associated with frame  220  such that blade portion  230  is configured to maintain an open position once it is urged into that open position. This may be achieved by the use of a locking/opening mechanism  40  as described above, or a variation of such a mechanism. The force required to open blade portion  230  may be substantially aligned with the direction of the displacement of at least a portion of the blade portion  230 . An example of this may be seen by comparing  FIGS. 11A-12A , as a portion of blade portion  230  has been displaced in the direction of force applied to gripping portion  236 , as seen in  FIGS. 11B-12A .  
         [0065]      FIG. 12A  shows a top view of the retractor  210  with blade portion  230  in an open position. As seen in illustrated embodiment, frame  220  may have plurality of indentations  222  for associating with a connector  260 . Any suitable number of indentations  222  are contemplated, and the placement, shape, and size of the indentations  222  may be varied. Frame  220  may also have a slot  223  for receiving a tab portion  234  of blade portion  230 . The interaction of slot  223  and tab portion  234  may serve to releasably secure frame  220  to blade portion  230 . Frame  220  and blade portion  230  may also be secured by way of a slot (not shown) within blade portion  230  and a hook element (not shown) projected from frame  220 . Various other securing and fixing relationships between frame  220  and blade portion  230  are contemplated to ensure that frame  220  and blade portion  230  are sufficiently secured during use. Frame  220  may also have an opening  224 , which may be larger than the maximum size of opening  212 . Frame  220  may also have a handle portion  225 , which may have a locking/opening assembly  226  and a flange  227 . Locking/opening assembly  226  may be associated with a contoured portion  235  of a blade portion  230 , and may function substantially similarly to locking/opening mechanism  40 , described above. Flange  227  may be useful in gripping the handle portion  225  of the frame  220 .  
         [0066]     Blade portion  230  may have at least one blade, and may have at least one hinge  232  disposed between blades. Hinge  232  may have any or all of the characteristics of a “living hinge,” as described above. Blade portion  230  may also have a projecting portion  233 , which may have a contoured portion  235  and a gripping portion  236 . As stated above, contoured portion  235  may interact with locking/opening assembly  226  of frame  220  to control the opening of blade portion  230 , and also allow the blade portion  230  to be releasably locked in an open position. In the embodiment shown in  FIG. 12A , this is achieved by providing a resilient tab in locking/opening assembly  226  and a series of parallel ridges on contoured portion  235 , wherein as gripping portion  236  is pulled toward flange  227 , resilient tab may engage subsequent rows of ridges on contoured portion  235 . Moreover, ridges may be designed such that the resilient tab may not “back-our” of engagement with a subsequent ridge and return to a previous ridge, so that a unidirectional relative movement between the locking/opening assembly  226  and contoured portion  235  is maintained. The result of this arrangement may therefore be that as blade portion  230  is opened, it&#39;s opening  212  may not thereafter be reduced in size unless a user intervenes.  
         [0067]      FIG. 12B  shows a front view of the retractor of  FIG. 12A , showing blade portion  230  in more detail. Blade portion  230  may have major blades  231   a  and minor blades  231   b  separated by hinges  232 . Major blades  231   a  may be larger in size than minor blades  231   b . Blade portion  230  may have any suitable number of major blades  231   a , minor blades  231   b , and/or hinges  232 , the number of which may be varied at least in part on the desired shape and size of opening  212 , and the amount of flexibility desired by the blade portion  230 . Major and minor blades  231   a ,  231   b  may also each have curved lower edges  237   a ,  237   b , which may assist the insertion process into an incision.  
         [0068]      FIGS. 13A-14B  show embodiments of guides  240 ,  250  for use with retractor  210 . As seen in the side view of  FIG. 13A , and cross-sectional view of  FIG. 13B , guide  240  may have an attachment end  242 , a free end  241 , and a shaft extending therebetween having a threaded portion  244 . Guide  240  may also have a bore  245  extending between a leading opening  247  and a trailing opening  246 . Bore  245  may be beneficial for accepting a guide wire (not shown). Guide  240  may further have a bulbous attachment portion  243  located adjacent to the attachment end  242 . Attachment portion  243  may directly or indirectly be associated with a bone screw  270 , and may do so by way of a threaded portion  249 . Guide  240  may also have a flattened portion  248  and an annular groove  248   a , which may allow for releasably lockable insertion into an insertion instrument (not shown).  
         [0069]      FIGS. 14A-14B  show another embodiment of a guide  250 . As seen in the side view of  FIG. 14A , and cross-sectional view of  FIG. 14B , guide  250  may have an attachment end  252 , a trailing end  251 , and a shaft extending therebetween having a threaded portion  254 . Guide  250  may also have a bore  245  extending between a leading opening  257 , and terminating at end  258 . Guide  250  may further have an attachment portion  253  located adjacent attachment end  252 . Attachment portion  253  may be an open-faced chamber for direct or indirect association with a bone screw  270 . Though described independently, guides  240 ,  250  may have any of the characteristics of the other. Further modifications and combinations will be appreciated by those skilled in the art.  
         [0070]     An embodiment of a connector  260  is shown in  FIG. 15 . Connector  260  may have an attachment portion  262  for association with a frame  220 . Connector  260  may also have a central bore  264  for receiving a guide  240 ,  250 . Central bore  264  may be provided by coextensive openings in attachment portion  262  and nut  265 . Nut  265  may house a compression nut  266 .  
         [0071]     To adjust the clearance within central bore  264 , compression nut  266  may be depressed and released. Specifically, when compression nut  266  is depressed by a user relative to nut  265 , central bore  264  may be substantially free from obstruction, such that a guide  240 ,  250  may be passed through bore  264 . Upon release of compression nut  266 , it may be urged back it its original position by a compression spring (not shown) housed within nut  265 , and bear against the guide  240 ,  250  within bore  264  such that guide  240 ,  250  is fixed within bore  264 . Compression nut  266  may also have a threaded bore (not shown) for threaded engagement with a threaded portion  244 ,  254  of guides  240 ,  250 . Other methods and arrangements of releasable securement between guides  240 ,  250  and connector  260  is expressly contemplated, as will be appreciated by those skilled in the art.  
         [0072]     An embodiment of a wedge-spreader  280  is shown in  FIG. 16 . Wedge-spreader may have any or all of the same design characteristics and advantages of expander  180  described and shown in  FIG. 7 , above. Wedge-spreader  280  may have a wedge  281  having a leading edge  282 , a handle  283 , and a connecting portion  284  therebetween. Wedge-spreader  280  may be beneficial in assisting with the opening of blade portion  230 .  
         [0073]     Another embodiment of frame  320  is shown in  FIG. 17 . Similar to frame  220  discussed above, frame  320  may have indentations  322  for association with a connector  260 , a slot  323  for receiving a tab portion  235  of a blade portion, and an opening  324 . Frame  320  may further have a handle portion  325  having a locking/opening assembly  326  having a resilient tab, and a flange  327 . Frame  320  may further have raised projections  328  and  329  as well disposed along the outer perimeter of the frame. Projections  328 ,  329  may be beneficial in providing suitable locations along the frame  320  for engagement with a clamp (not shown) that may be utilized to affix the frame  320  to an external structure. Projections  328 ,  329  may also be useful for affixing a light device, suction device, nerve root effector, or other instrument to the frame  320 .  
         [0074]     Though several embodiments of the retractors discussed above are described for use with at least one guide, it is expressly contemplated that all retractors described herein may be used without the use of at least one guide, or any other attachment mechanism. Thus, a surgeon may find it preferable to utilize the retractor of  FIGS. 1-2 ,  12 A- 12 B without the use of any mechanism or components to attach the retractor to the body before or during operation of the retractor. In using the retractor in this way, a surgeon may make an incision in a desired location, and then insert the retractor directly into the incision. This procedure may be preferable when the desired retraction area is not overly deep, or does not involve undue force to retract body tissue in such retraction area. This procedure may also be preferable when is difficult or impractical to attach guides near or in the retraction area prior to or during insertion of the retractor.  
         [0075]     Thus, specific embodiments and applications of novel retractors have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.