Patent Publication Number: US-2005137461-A1

Title: Telescoping blade assembly and instruments for adjusting an adjustable blade

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority to U.S. Provisional Patent Application Ser. No. 60/530,565, filed Dec. 18, 2003, entitled Surgical Retractor Systems, Illuminated Cannula, and Method of Use, which is incorporated herein by reference 
    
    
     BACKGROUND  
      In surgical procedures, it is important to minimize trauma to the patient and damage to tissue to facilitate patient recovery. One way to accomplish this is to minimize the size of the incision for the surgical procedure. A number of retractors are available that are designed to expand a small surgical incision and provide access to a surgical site. Such retractors often require the surgeon to select retractor blades of an appropriate length and width for the patient&#39;s anatomy during the surgical procedure. As a result, conventional retractors often include a large set of retractor blades of varying fixed lengths and widths for use with the retractor. Such fixed retractor blades may not conform to each patient&#39;s individual anatomy.  
     SUMMARY  
      Disclosed herein are retractor blade assemblies that facilitate the retraction of soft tissue during a surgical procedure and may be adjusted to conform to varying patient anatomy. The disclosed retractor blade assemblies may be used with a wide range of surgical retractors and in any type of surgical procedure in which a retractor may be employed, including, for example, minimally invasive spine surgery. Also disclosed herein are surgical instruments that may be employed to easily adjust an adjustable blade of a retractor blade assembly, such as one of the retractor blade assemblies disclosed herein.  
      In one exemplary embodiment, a retractor blade assembly may comprise a fixed blade having a longitudinal axis and an adjustable blade operatively coupled to the fixed blade and adjustable relative to the fixed blade along the longitudinal axis of the fixed blade. In the exemplary embodiment, the adjustable blade may include a flexible tab that is movable between a first position, in which the tab is generally co-planar to the adjustable blade, and a second position, in which the tab is oriented generally transverse to the adjustable blade.  
      In another exemplary embodiment, a retractor blade assembly may comprise a fixed blade having a longitudinal axis, an adjustable blade operatively coupled to the fixed blade and adjustable relative to the fixed blade along the longitudinal axis of the fixed blade, and a flexible sheath coupled at one portion to the fixed blade and at a second portion to the adjustable blade.  
      In a further exemplary embodiment, a retractor blade assembly may comprise a fixed blade having a longitudinal axis and a plurality of adjustable blades operatively coupled to the fixed blade and adjustable relative to the fixed blade along the longitudinal axis of the fixed blade between a proximal position and a distal position. In the exemplary embodiment, the plurality of adjustable blades may include one or more laterally adjustable blades that are adjustable relative to one another in a direction transverse to the longitudinal axis of the fixed blade when the plurality of adjustable blades are adjusted to a distal position.  
      In one exemplary embodiment, an instrument for adjusting an adjustable blade of a retractor blade assembly may comprise a handle and an instrument body coupled to the handle. In the exemplary embodiment, the instrument body may include a distal end having a distal facing notch formed therein. The notch may be defined by a first surface and a second surface, which may be angled proximally toward the first surface. In the exemplary embodiment, the notch may be sized to receive a portion of the adjustable blade between the first surface and the second surface. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
      These and other features and advantages of the retractor blade assemblies, instruments, and methods disclosed herein will be more fully understood by reference to the following detailed description in conjunction with the attached drawings in which like reference numerals refer to like elements through the different views. The drawings illustrate principles of the retractor blade assemblies and instruments disclosed herein and, although not to scale, show relative dimensions.  
       FIGS. 1 and 2  are perspective views of an exemplary embodiment of a retractor blade assembly;  
       FIG. 3  is a perspective view of the fixed blade of the retractor blade assembly of  FIGS. 1 and 2 ;  
       FIG. 4A  is a perspective view of the inner surface of the adjustable blade of the retractor blade assembly of  FIGS. 1 and 2 , illustrating the flexible tab in a first position;  
       FIG. 4B  is a side elevational view of the proximal end of the adjustable blade of  FIG. 4A , illustrating the flexible tab in a second position;  
       FIG. 5  is a perspective view of the outer surface of the adjustable blade of the retractor blade assembly of  FIGS. 1 and 2 ;  
       FIG. 6  is a perspective view of the outer surface of the retractor blade assembly of  FIGS. 1 and 2 ;  
       FIG. 7  is a perspective view of the proximal end of the inner surface of the adjustable blade of  FIG. 4 ;  
       FIG. 8A  is a perspective view of another exemplary embodiment of a retractor blade assembly;  
       FIG. 8B  is a side elevational view of the proximal end of the fixed blade of the retractor blade assembly of  FIG. 8A ;  
       FIG. 8C  is a perspective view of the proximal end of the fixed blade of the retractor blade assembly of  FIG. 8A , illustrating an instrument for adjusting the adjustable arm of the fixed blade;  
       FIG. 8D  is a side elevational view of the distal end of the instrument of  FIG. 8C ;  
       FIG. 9  is a perspective view of an adjustable blade of the retractor blade assembly of  FIG. 8A ;  
       FIG. 10  is a perspective view of another exemplary embodiment of a retractor blade assembly;  
       FIG. 11  is a perspective view of the inner surface of the retractor blade assembly of  FIG. 10 ;  
       FIG. 12  is a side elevational view in cross section of the retractor blade assembly of  FIG. 10 ;  
       FIG. 13  is a top view in cross section of the retractor blade assembly of  FIG. 10 ;  
       FIG. 14  is a perspective view of another exemplary embodiment of a retractor blade assembly, illustrating the adjustable blade in a proximal position;  
       FIG. 15  is a perspective view of the retractor blade assembly of  FIG. 14 , illustrating the adjustable blade in a distal position;  
       FIG. 16  is a perspective view of the inner surface of the retractor blade assembly of  FIG. 14 ;  
       FIG. 17  is a perspective view of the adjustable blade of the retractor blade assembly of  FIG. 14 ;  
       FIG. 18  is a perspective view of the inner surface of the adjustable blade of  FIG. 17 ;  
       FIG. 19  is a perspective view of an exemplary embodiment of an instrument for adjusting the adjustable blade of a retractor blade assembly;  
       FIG. 20  is a perspective view of the instrument of  FIG. 19 , illustrating the distal end of the instrument engaging the adjustable blade of the retractor blade assembly of  FIG. 1 ;  
       FIG. 21  is a perspective view of the distal end of the instrument of  FIG. 19 , illustrating the distal end engaging the adjustable blade of the retractor blade assembly of  FIG. 1 ;  
       FIG. 22A  is a perspective view of the distal end of the instrument of  FIG. 19 ;  
       FIG. 22B  is a side elevational view of the distal end of the instrument of  FIG. 19 ;  
       FIG. 23  is a side elevational view of another exemplary embodiment of a retractor blade assembly including a flexible sheath, illustrating the adjustable blade in a proximal position;  
       FIG. 24  is a side elevational view of the retractor blade assembly of  FIG. 23 , illustrating the adjustable blade in a distal position;  
       FIG. 25  is a side elevational view of the inner surface of another exemplary embodiment of a retractor blade assembly, illustrating the adjustable blade in a proximal, laterally compact position;  
       FIG. 26  is a side elevational view of the inner surface of the retractor blade assembly of  FIG. 25 , illustrating the adjustable blade in a distal, laterally expanded position;  
       FIG. 27  is a bottom view of the retractor blade assembly of  FIG. 25 , illustrating the adjustable blade in a proximal, laterally compact position;  
       FIG. 28  is a side elevational view of the inner surface of the adjustable blade of the retractor assembly of  FIG. 25 , illustrating the adjustable blade in a laterally expanded configuration;  
       FIG. 29  is a side elevational view of the adjustable blade of the retractor assembly of  FIG. 25 , illustrating the adjustable blade in a laterally compact configuration;  
       FIG. 30  is a side elevational view of the distal end of an alternative exemplary embodiment of the adjustable blade of the retractor blade assembly of  FIG. 25 ;  
       FIG. 31  is a side elevational view of the inner surface of the adjustable blade of another exemplary embodiment of a retractor blade assembly, illustrating the adjustable blade in a laterally compact configuration;  
       FIG. 32  is a side elevational view of the inner surface of the adjustable blade of  FIG. 31  illustrating the adjustable blade in a laterally expanded configuration; and  
       FIG. 33  is a side elevational view of the inner surface of the adjustable blade of another exemplary embodiment of a retractor blade assembly. 
    
    
     DETAILED DESCRIPTION  
      Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the retractor blade assemblies and instruments disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the retractor blade assemblies and instruments specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.  
      The articles “a” and “an” are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.  
      The term “distal” as used herein with respect to any component or structure will generally refer to a position or orientation that is proximate, relatively, to a surgical site within the body. Conversely, the term “proximal” as used herein with respect to any component or structure will generally refer to a position or orientation that is distant, relatively, to a surgical site within the body.  
      The terms “comprise,” “include,” and “have,” and the derivatives thereof, are used herein interchangeably as comprehensive, open-ended terms. For example, use of “comprising,” “including,” or “having” means that whatever element is comprised, had, or included, is not the only element encompassed by the subject of the clause that contains the verb.  
       FIGS. 1-7  illustrate an exemplary embodiment of a retractor blade assembly  10  including a fixed blade  12  and an adjustable blade  14  that is operatively coupled to the fixed blade  12  and is adjustable relative to the fixed blade  12  along the longitudinal axis  16  of the fixed blade  12  between a proximal position and a distal position. The exemplary retractor blade assembly  10  may be used alone or in combination with other retractor blades to form a surgical retractor that is suitable for retracting tissue during a surgical procedure. For example, the exemplary surgical retractor blade assembly  10  may be employed in one or more of the retractors disclosed in commonly-owned U.S. Provisional Patent Application No. 60/530,565, entitled Surgical Retractor Systems, Illuminated Cannula, and Method of Use, which is incorporated herein by reference. The retractor blade assembly  10  may used to retract any type of tissue in any type of surgical procedure, including, for example, minimally invasive spine procedures, and to create a working channel from a skin incision to a surgical site in vivo.  
      The fixed blade  12  of the exemplary retractor blade assembly  10  includes a proximal end  18  spaced apart along the longitudinal axis  16  from a distal end  20 . The proximal end  18  may be configured to connect with a surgical retractor or with other retractor blade assemblies of similar or dissimilar constructions. In the exemplary embodiment, for example, the proximal end  18  includes an opening  22  for receiving an arm  24  ( FIG. 6 ) of a retractor, such as a retractor disclosed in above-referenced provisional patent application. One skilled in the art will appreciate that the proximal end  18  may be alternatively configured, depending on the type of retractor, to facilitate connection with other types of retractors. The fixed blade  12  includes a pair of spaced apart channels  24 A and  24 B that extend longitudinally from the proximal end  18  to the distal end  20  of fixed blade  12 . Each channel  24 A,  24 B is sized and shaped to receive a rail  50  provided on the adjustable blade  14 , as discussed in more detail below. The channels  24 A,  24 B cooperate with the rails  50 A,  50 B to guide the adjustable blade  14  during adjustment relative to the fixed blade  12 . The channels  24 A,  24 B are oriented parallel to one another and parallel to the longitudinal axis  16  of the fixed blade  12 , although other orientations are possible depending on the desired path for the adjustable blade  14 . In addition, the length of the channels  24 A,B can be varied depending on, for example, the length of the adjustable blade  14  and the amount of longitudinal adjustment desired. The channels  24 A,  24 B need not extend along the entire length of the fixed blade  12 , as in the illustrated embodiment.  
      The fixed blade  12  may optionally include one or more stops for fixing the adjustable blade  14  at a position along the longitudinal axis of the fixed blade  12 . In the exemplary embodiment, for example, the fixed blade  12  includes a plurality of stops, in the form of teeth  30 , aligned longitudinally along the fixed blade  12 . The teeth  30  are configured to be engaged by a projection  72  provided on the adjustable blade  14 , as discussed in more detail below. The number and position of the stops provided on the fixed blade  12  may be varied depending on the particular application. Moreover, the configuration of the stops may be varied. For example, each stop may be a hole, detent, rib, shoulder, or any other structure for fixing the adjustable blade  14 , in a temporary or permanent manner, relative to the fixed blade  12 . In other exemplary embodiments, one or more stops may be provided on the adjustable blade  14  in addition to or in place of one or more stops provided on the fixed blade  12 .  
      Continuing to refer to  FIGS. 1-7 , the adjustable blade  14  of the exemplary embodiment includes a proximal end  40  spaced apart from a distal end  42 . The adjustable blade  14  may include an inner surface  44  and an outer surface  46 . The inner surface  44 , in cooperation with the inner surface  26  of the fixed blade  12 , can define a working channel for the retractor assembly  10 . The outer surface  46  of the adjustable blade  14 , in cooperation with the outer surface  28  of the fixed blade  12 , can face and contact tissue to be retracted to inhibit the retracted tissue from entering or otherwise interfering with the working channel defined by the inner surfaces  26 ,  44  of the retractor blade assembly  10 . The outer surface  46  of the adjustable blade  14  and the outer surface  28  of the fixed blade  12  may each include surface texturing, e.g., one or more grooves or surface roughening, or other surface treatments or coatings to improve gripping of retracted tissue. The adjustable blade  14  may include one or more guide rails  50  that cooperate with one or more channels  24  provided on the fixed blade  12 . In the illustrated embodiment, for example, the adjustable blade  14  includes a pair of spaced apart guide rails  50 A,  50 B. Each of the guide rails  50 A,  50 B are sized to seat within a respective one of the channels  24 A,  24 B. As discussed above, the guide channels  50 A,  50 B cooperate with the channels  24 A,  24 B, to guide the adjustable blade  14  during adjustment relative to the fixed blade  12 . Like the channels  24 , the length, orientation, and number of rails  50  may be varied. The rails  50  need not extend along the entire length of the adjustable blade  14 , as in the exemplary embodiment.  
      One skilled in the art will appreciate that the location of the channels  24  and guide rails  50  may reversed, e.g., the adjustable blade  14  may be provided with one or more channels  24  and the fixed blade  12  may be provided with one or more guide rails  50 .  
      The outer surface  46  of the adjustable blade  14  may include one or more grooves  52  that engage the fixed blade  12  to facilitate alignment of the adjustable blade  14  relative to the fixed blade  12  and facilitate tissue engagement. In the illustrated embodiment, for example, the outer surface  46  includes a pair of longitudinally aligned, parallel grooves  52 A,  52 B that are sized and shaped to engage a pair of longitudinally aligned parallel ribs  29 A,  29 B provided on the fixed blade  12 .  
      The adjustable blade  14  may include a flexible tab  60  that facilitates adjustment of the adjustable blade  14  relative to the fixed blade  12  and cooperates with one or more of stops provided on the fixed blade  12  to fix the adjustable blade  14  relative to the fixed blade  12 . The flexible tab  60 , in the exemplary embodiment, is movable between a first position, in which the tab  60  is generally co-planar to the adjustable blade  14  as illustrated in  FIG. 4A , and a second position, in which the tab  60  is oriented generally transverse to the adjustable blade  14 , as illustrated in  FIG. 4B . In the first co-planar position, the inner surface  62  of the tab  60  is preferably aligned with the inner surface  44  of the adjustable blade  14  such that the tab  60  minimizes interference with the working channel created by the retractor blade assembly  10 . The flexible tab  60 , when in the first position, may be configured to engage to the fixed blade  12  to fix the adjustable blade  14  relative to the fixed blade  12 , as discussed below. In certain embodiments, including the illustrated embodiment, the tab  60  may be biased to the first position. In the second position, as illustrated in  FIG. 4B , the inner surface  62  of the tab  60  is oriented at an angle to the inner surface  44  of the adjustable blade  14 . The angle of inner surface  62  in the second position may be varied depending on the configuration, e.g., the shape and material, of the flexible tab  60 . In certain exemplary embodiments, the angle is greater than 3°. The flexible tab  60 , when in the second position, may be configured to disengage the fixed blade  12  to facilitate adjustment of the adjustable blade  14  relative to the fixed blade  12 . In such embodiments, the angle of the inner surface  62  may be selected to permit disengagement.  
      The flexible tab  60  may have a variety of shapes and sizes. In the illustrated embodiment, for example, the tab  60  is generally rectilinear in shape. The exemplary tab  60  includes a proximal end  64  having a proximally facing surface  66 , a distal end  68 , and two parallel, longitudinally aligned lateral surfaces  70 A,  70 B. The distal end  68 , in the illustrated embodiment, is coupled to and formed from the adjustable blade  14 . In this configuration, the tab  60  may pivot about the distal end  68  between the first position and the second position. The distal end  68  of the tab  60  need not be formed from the adjustable blade  14 . In other exemplary embodiments, for example, the distal end  68 , or other portions of the tab  60 , may be separately constructed from the adjustable blade  14  and then coupled to the adjustable blade  14  by conventional fastening mechanisms. The tab  60  may be constructed from a flexible and resilient material such that the tab  60  may be deflected to the second position and, upon release, may return to the first position.  
      The tab  60  may include a projection  72  that is configured to engage the fixed blade  12 , for example, one or more stops provided on the fixed blade  12 , to fix the adjustable blade  14  relative to the fixed blade  12 . The projection  72  may be sized and shaped to engage a stop provided on the fixed blade  12 . In the exemplary embodiment, for example, the projection has a triangular shaped cross-section that is sized to engage one or more of the teeth  30  provided on the fixed blade  12 . In other embodiments, the projection  72  may be spherical or hemispherical in shape to engage a hole or detent formed in the fixed blade  12 . In the exemplary embodiment, the projection  72  engages one of the teeth  30  when the tab  60  is in the first position. When the tab  60  is moved away from the fixed blade  12  to a second position, the projection  72  may disengage the tooth, allowing the adjustable blade  14  to be adjusted relative to the fixed blade  12 .  
      In certain exemplary embodiments, including the illustrated embodiment, a portion of the tab  60  may include an instrument engagement surface that is configured, e.g., sized, shaped, and/or oriented, to facilitate adjustment of the adjustable blade  14  by an instrument. In the illustrated embodiment, for example, the proximally facing surface  66  of the tab  60  is sized, shaped, and oriented to be engage by an instrument, such as the instrument illustrated in  FIGS. 19-22 , to facilitate adjustment of the adjustable blade  14 . In particular, the proximally facing surface  66  of the tab  60  is oriented generally perpendicular to the longitudinal axis of the fixed blade  12 .  
      Continuing to refer to  FIGS. 1-7 , the adjustable blade  14  may include an opening adjacent an instrument engagement surface to facilitate positioning of an instrument against the instrument engagement surface. In the illustrated exemplary embodiment, for example, an opening  74  through the adjustable blade  14 , i.e., spanning between the inner surface  44  and the outer surface  46 , is positioned proximal the proximally facing surface  66  of the flexible tab  60 . The opening  74  may have a size and shape to receive a portion of instrument, such as the distal end of the instrument illustrated in  FIGS. 19-22 . For example, in the illustrated embodiment, the opening  74  has a length L o  and width W o  that is greater than or equal to a L i  and W i  of a portion of the instrument  500  illustrated in  FIGS. 19-22 , as discussed in further detail below. The opening  74  allows positioning of a portion of the distal tip of the instrument  500  between the flexible tab  60  and the fixed blade  12 .  
      The fixed blade  12  and the adjustable blade  14  may be constructed from any material suitable for use in vivo, including, for example, metal, such as stainless steel or titanium, polymers, ceramics, or combinations thereof. In certain exemplary embodiments, the fixed blade  12  may be constructed from stainless steel and the adjustable blade may be constructed from a polymer.  
       FIGS. 8-9  illustrate another exemplary embodiment of a retractor blade assembly  110  having a fixed blade  112  and an adjustable blade  114  that is adjustable relative to the fixed blade  112  along the longitudinal axis of the fixed blade  112 . In the illustrated embodiment, the proximal end  118  of the fixed blade  112  is configured to engage a portion of a retractor, such as an arm  24  of a retractor. In particular, the proximal end  118  includes a fixed arm  119 , which is oriented generally transverse to the longitudinal axis of the fixed blade  112 , and an adjustable arm  121 , which is oriented generally parallel to the longitudinal axis of the fixed blade  112  and is adjustable relative to the fixed arm  119  to selectively engage a portion of a retractor, such as the arm  24  of the retractor, therebetween. In particular, the adjustable arm  121  is adjustable between a closed position, illustrated in  FIG. 8A , in which the distance between the fixed arm  119  and the adjustable arm  121  is less than or equal to the portion of the retractor to be engaged, and an open position in which the distance between the fixed arm  119  and the adjustable arm  121  is greater than the portion of the retractor to be engaged. In the exemplary embodiment, the adjustable arm  121  is biased to a closed position by a spring  123  or other biasing mechanism. A button  125 , lever, handle or other adjustment mechanism may be provided to facilitate adjustment of the adjustable arm  121 , as illustrated in  FIGS. 8A and 8B . In other exemplary embodiments, an instrument  175  for adjusting the adjustable arm  121  relative to the fixed arm  119  may be provided, as illustrated in FIGS.  8 C-D. For example, the proximal end  118  of the fixed blade  112  may include an opening  177  for receiving the distal end  179  of the instrument  175 . The opening  177  may communicate with the adjustable arm  121  to allow a portion of the distal end  179  to contact the adjustable arm  121  to advance the adjustable arm  121  away from the fixed arm  119 . The distal end  179  may have an L-shaped cross section including a base section  181  that extends generally transverse to the longitudinal axis of the instrument  175 . The opening  177  may be generally key-shaped to allow the distal end  179  to pass through in one orientation and upon rotation of the instrument  175 , the base section  181  may engage a ledge or other structure to fix the adjustable blade  121  in a desired position.  
      In the illustrated embodiment, the fixed blade  112  includes a plurality of stops in the form of detents  130 . The detents  130  are longitudinally aligned and may be sized to receive a projection provided on a flexible tab  160 .  
       FIGS. 10-13  illustrate another exemplary embodiment of a retractor blade assembly  210  having a fixed blade  212  and an adjustable blade  214  that is longitudinal adjustable relative to the fixed blade  212 . In the illustrated embodiment, the fixed blade  212  includes a plurality of longitudinally aligned parallel guide rails  215  that cooperate with a plurality of longitudinally aligned parallel slots  217  provided on the adjustable blade  214  to guide the adjustable blade  214  during adjustment relative to the fixed blade  212 . The rails  215  may be complementary in shape to the grooves  217 , as in the illustrated embodiment. In the illustrated embodiment, each rail  215  and each corresponding groove has a generally trapezoidal cross section. In this configuration, each rail  215  and each groove  217  interlock in the manner of a dovetail joint to limit the motion of the adjustable blade  214  to one direction, parallel to the longitudinal axis of the fixed blade  212 . Although each rail  215  (and each groove  217 ) is similar in size and shape in the illustrated exemplary embodiment, one skilled in the art will appreciate that the fixed blade  212  may have rails  215  of varying size and shape and the adjustable blade  214  may have grooves  217  of varying size and shape. For example, in certain exemplary embodiments, the fixed blade  212  may have one rail with a trapezoidal cross section and one or more other rails with a different, e.g., non-trapezoidal, cross section.  
      In the illustrated embodiment, the fixed blade  212  may include a stop in the form of a ridge  230  provided at the distal end of the fixed blade  212 . The ridge  230 , in the illustrated embodiment, is oriented generally perpendicular to the longitudinal axis of the fixed blade  212 , although other orientations are possible. The ridge  230  may span the width of the fixed blade  212 , as in the illustrated embodiment, or may extend along a portion or portions of the width of the fixed blade  212 . The adjustable blade  214  may include a shoulder  272  that engages the ridge  230  to limit the extent of longitudinal advancement of the adjustable bladed  214 .  
       FIGS. 14-18  illustrate another exemplary embodiment of a retractor blade assembly  310  including a fixed blade  312  and an adjustable blade  314  that is adjustable along the longitudinal axis of the fixed blade  312 .  FIG. 14  illustrates the adjustable blade  314  in a proximal, retracted position in which a substantial portion of the adjustable blade  314  is positioned within the fixed blade  312 .  FIGS. 15 and 16  illustrate the adjustable blade  314  in a distal, expanded position in which a portion of the adjustable blade  314  is withdrawn from the fixed blade  312  thereby increasing the overall length of the retractor blade assembly  310 .  
      Referring in particular to  FIG. 16 , the fixed blade  312  includes a pair of spaced apart channels  324 A and  324 B that extend longitudinally from the proximal end  318  to the distal end  320  of fixed blade  312 . Each channel  324 A,  324 B is sized and shaped to receive a portion of the adjustable blade  314 , such as a lateral edge  349 A,  349 B of the adjustable blade  314  as in the illustrated embodiment. In the illustrated embodiment, the channels  324 A,  324 B engage the lateral edges  349 A,  349 B to limit the motion of the adjustable blade  314  to longitudinal motion during adjustment relative to the fixed blade  312 . The channels  324 A,  324 B are oriented parallel to one another and parallel to the longitudinal axis of the fixed blade  312 , although other orientations are possible depending on the desired path for the adjustable blade  314 . In addition, the length of the channels  324 A,B can be varied depending on, for example, the length of the adjustable blade  314  and the amount of longitudinal adjustment desired. The channels  324 A,  324 B need not extend along the entire length of the fixed blade  312 , as in the exemplary embodiment, but instead may extend along a portion or discrete portions of the fixed blade  312 .  
      Referring in particular to  FIG. 17 , the inner surface  344  of the adjustable blade  314  may includes a plurality of stops, in the form of teeth  330 , aligned longitudinally along the adjustable blade  314 . In the illustrated embodiment, for example, two parallel columns of teeth  330 A, B are provided on the lateral edges  349 A,  349 B, respectively, of the adjustable blade  314 . The teeth  330  are configured to be engaged by a projection provided on the fixed blade  312 . For example, in the illustrated embodiment, each channel  324 A,B of the fixed blade  312  may be provided with a projection (not shown), provided, for example, at the distal end of each channel  324 A, B. Each projection may engage one of the teeth  330  to fix the adjustable blade  314  in a position relative to the fixed blade  312 .  
      In certain exemplary embodiments, the outer surface  346  of the adjustable blade  314  and the outer surface  328  of the fixed blade  312  may each include surface texturing, e.g., one or more grooves or surface roughening, or other surface treatments or coatings to improve gripping of retracted tissue. In the illustrated embodiment, for example, the outer surface  346  of the adjustable blade  314  may include one or more grooves  352  to facilitate tissue engagement. The grooves  352  may be aligned longitudinally along the length of the adjustable blade  314 , as in the exemplary embodiment, or in other orientations or length(s) suitable to facilitate tissue engagement.  
      The adjustable blade  314  may include an adjustment mechanism that engages the fixed blade  312  to facilitate adjustment of the adjustable blade  314  relative the fixed blade  312 . In the illustrated embodiment, for example, the adjustable blade  314  includes a pair of prongs  361  that extend from the inner surface  344  of the adjustable blade  314  to engage a longitudinally oriented slot  363  provided in the fixed blade  312 . Each prong  361 A, B extends through the slot  363  and includes a flange  365 A, B that engages the outer surface of the fixed blade  312  to inhibit separation of the adjustable blade  314  from the fixed blade  312 . The prongs  361 A, B may be flexible and resilient. For example, the prongs  361 A, B may be compressed toward one another from an expanded configuration, illustrated in  FIG. 18 , to a collapsed position. In the expanded configuration, the prongs  361 A, B may engage the sidewalls of the slot  363  to inhibit adjustment of the adjustable blade  314  relative to the fixed blade  312 . In a collapsed position, the prongs  361 A, B may be disengaged from the sidewalls of the slot  363  to facilitate adjustment of the adjustable blade  314  relative to the fixed blade  312 . The prongs  361 A, B may be biased to the expanded configuration, as in the illustrated embodiment.  
       FIGS. 19-22B  illustrate an exemplary embodiment of an instrument  500  for adjusting an adjustable blade of a retractor blade assembly. The exemplary instrument  500  will be described in connection with the retractor blade assembly  10  described above in connection with  FIGS. 1-7 , although one of skill in the art will appreciate that the exemplary instrument  500  may be used with any type of retractor blade assembly, including any of the exemplary embodiments of the retractor blade assemblies disclosed herein. In the illustrated embodiment, the instrument  500  includes a handle  502  positioned at a proximal end of the instrument  500  and an instrument body  504  that extend distally from the handle  502  to terminate at a distal end  506  of the instrument  500 . The illustrated instrument  500  is bayoneted, e.g., the longitudinal axis of the handle  500  is offset from the longitudinal axis of a distal portion of the instrument body  504 , to minimize obstruction of the working channel of the retractor blade assembly during use. The handle  502  may be offset by any amount, depending, for example, on the retractor blade assembly with which the instrument is designed for use, although, one of ordinary skill in the art will appreciate that the instrument  500  need not be bayoneted and that in certain embodiments the handle  502  and the instrument body  504  may be coaxial.  
      The distal end  506  of the instrument  500  may be configured to facilitate engagement of the instrument  500  with an adjustable blade of a retractor blade assembly. For example, in the illustrated embodiment, the distal end  500  has a distal facing notch  508  formed therein for engagement with, for example, a portion of the tab  60  of the adjustable blade  14 . The distal notch  508 , in the illustrated embodiment, is defined by a first surface  510  and a second surface  512 . The first surface  510  extends proximally from the distal end  506  and is oriented generally parallel to the longitudinal axis of the distal end  506  of the instrument body  504  and a top surface  514  of the instrument body  504 . The second surface  512  is angled proximally from the distal end  508  toward the first surface  510 . The orientation of the second surface  512  and the first surface  510  may be varied depending on the geometry of the retractor blade assembly with which the instrument  500  is design for use. For example, in the illustrated embodiment, the second surface  512  is oriented at an angle to the bottom surface  516  of the instrument body  504  to facilitate engagement of the distal end  508  with the tab  60  of the adjustable blade  14  of the exemplary retractor blade assembly  10 . In particular, the orientation of the second surface  512  is selected to move the tab  60  from the first position, in which the projection  72  engages one of the teeth  30  of the fixed blade  12 , to the second position, in which the tab  60  is moved away from the fixed blade  12  and the projection  72  is disengaged from the tooth, as the distal end  506  of the instrument  500  is advanced distally. The angle of orientation of the second surface  512 , indicated by angle A in  FIG. 22B , may be any acute angle. In certain exemplary embodiments, the angle A may be approximately 20° to approximately 40°. In one exemplary embodiment, the angle A is approximately 25°.  
      In certain exemplary embodiments, including the illustrated embodiment, the distal notch  508  may include a third surface  518  that is interposed between the first surface  510  and the second surface  512 . In the illustrated embodiment, the third surface  518  is oriented generally perpendicular to the longitudinal axis of the distal end  506  of the instrument body  504  to facilitate engagement of the third surface  518  with the proximally facing instrument engagement surface  66  of the tab  60 . The orientation of the third surface  518  may be varied depending on, for example, the orientation of the surface with which the third surface  518  is design to engage. The third surface  518 , in the illustrated embodiment, is arcuate in shape, although the third surface  518  may be linear, angled or other suitable shapes. In alternative exemplary embodiments, the first surface  510  and the second surface  512  may intersect, in which case a third surface will not be present.  
      Continuing to refer to  FIGS. 19-22B , in particular  FIGS. 22A-22B , the instrument body  504  may include a cut-out formed therein to facilitate engagement of the distal end  506  with an adjustable blade of a retractor blade assembly. In the illustrated embodiment, for example, the distal end  506  of the instrument body  504  includes a cut-out  520  that is formed in the bottom surface  516  of the instrument body  504  and is positioned proximal to the notch  508 . The cut-out  520  may be configured, e.g., sized, shaped, and positioned, to engage a portion of an adjustable blade to facilitate proximal adjustment of the adjustable blade relative to the fixed blade. In the illustrated embodiment, for example, the cut-out  520  is configured to engage a proximal edge  65  of the adjustable blade  14  ( FIGS. 5 &amp; 7 ). In particular, the length L C  of the cut-out  520  ( FIG. 22B ) may be greater than or equal to the length L P  of the proximal edge  65  of the adjustable blade  14  ( FIG. 5 ) and the cut-out  520  may be proximally offset from the distal end  506  of the instrument body  504  a length L I , which may be greater than or equal to the L O  of the opening  74  in the adjustable blade  14  ( FIG. 7 ).  
      The instrument  500  may be constructed from any material suitable for use in vivo, including, for example, metal, such as stainless steel or titanium, polymers, ceramics, or combinations thereof.  
      In use, the distal end  506  of the instrument body  504  may be engaged to the adjustable blade  14  of the retractor blade assembly  10  to facilitate proximal and distal adjustment of the adjustable blade  14  relative to the fixed blade  12 . In particular, distal end  504  is advanced distally to position the proximal end of the tab  60  within the notch  508 . As the proximal end of the tab  60  is advanced into the notch  508 , the second surface  512  causes the tab  60  to move from the first position to the second position to disengage the projection  72  from a tooth of the fixed blade  12 , thereby freeing the adjustable blade  14  to move relative to the fixed blade  12 . The distal end  506  is advanced distally until the proximal edge  65  is positioned within the cut-out  520  and the third surface  518  abuts the proximally facing surface  66  of the tab  60 . Once the instrument  500  is positioned, the adjustable blade  14  may be adjusted, proximally or distally, using the instrument. The instrument  500  can be used to adjust the adjustable blade  14  prior to or during a surgical procedure.  
       FIGS. 23 and 24  illustrate another embodiment of a retractor blade assembly  610  having a fixed blade  612  and an adjustable blade  614  that is longitudinally adjustable relative to the fixed blade  612 . The exemplary retractor blade assembly  610  includes a flexible sheath  605  coupled at a first portion  607  to the fixed blade  612  and at a second portion  609  to the adjustable blade  614 . In the exemplary embodiment, the flexible sheath  605  is coupled at one end to the fixed blade  612  and at another end to the adjustable blade  614 , although any portion or portions of the flexible sheath  605  may be coupled to the blades. The flexible sheath  605  may be connected at any point along the length of the fixed blade  612  or the adjustable blade  614 . In the illustrated embodiment, for example, the flexible sheath  605  is connected to the distal end of the fixed blade  612  and at the distal end of the adjustable blade  614 .  
      The flexible sheath  605  may be configured to inhibit tissue impingement between the adjustable blade  614  and the fixed blade  612 , particularly when the adjustable blade  614  is adjusted proximally and withdrawn into the fixed blade  612 . The flexible sheath  605  is preferably connected to the outer surface  646  of the adjustable blade  614  and the outer surface  628  of the fixed blade  612 . In the illustrated embodiment, the flexible sheath  605  is connected to both the inner surface ( 626 ,  644 ) and the outer surface ( 628 ,  646 ) of the fixed blade  612  and the adjustable blade  614 , respectively. The flexible sheath  605  may span at least a substantial portion of the width of the outer surface  646  of the adjustable blade  614 . In the illustrated embodiment, the flexible sheath  605  is tubular in shape and is positioned to surround the adjustable blade  614 .  
      The flexible sheath  605  may be constructed from any flexible material, including, for example, flexible polymers. In certain exemplary embodiments, the flexible sheath  605  may be constructed from an elastomeric polymer. The flexible sheath  605  may be constructed to be expandable from a generally collapsed configuration, as illustrated in  FIG. 23 , to an expanded configuration, illustrated in  FIG. 24 , during adjustment of the adjustable blade  614  to a distal position. In the expanded configuration, the flexible sheath  605  may be stretched along the surfaces of the adjustable blade  614  to inhibit tissue from entering the fixed blade  612 .  
       FIGS. 25-29  illustrate another exemplary embodiment of a retractor blade assembly  710  including a fixed blade  712  and an adjustable blade assembly  714  that is adjustable along the longitudinal axis  716  of the fixed blade  712 .  FIG. 25  illustrates the adjustable blade assembly  714  in a proximal, retracted position in which a substantial portion of the adjustable blade assembly  714  is positioned within the fixed blade  712 .  FIG. 26  illustrates the adjustable blade assembly  714  in a distal, expanded position in which a portion of the adjustable blade assembly  714  is withdrawn from the fixed blade  712  thereby increasing the overall length of the retractor blade assembly  710 .  
      In the certain exemplary embodiments, including the illustrated embodiment, the adjustable blade assembly  714  comprises a plurality of laterally adjustable blades that are adjustable relative to one another in a direction transverse to the longitudinal axis  716  of the fixed blade  712  when the adjustable blade assembly  714  is advanced to a distal position, as illustrated in  FIG. 25 . In the illustrated embodiment, for example, the adjustable blade assembly  714  comprises three adjustable blades  714 A,  714 B, &amp;  714 C, each of which is adjustable longitudinally relative to the longitudinal axis  716  of the fixed blade  712  and at least two of which, adjustable blades  714 A and  714 C, are also adjustable relative to one another along an arcuate axis X that is oriented transverse to the longitudinal axis  716  of the fixed blade  712 . The adjustable blade assembly  714  may include any number of laterally adjustable blades of any size or shape, depending on, for example, the desired width of the retractor blade assembly in the expanded configuration. Moreover, the amount of lateral expansion and the orientation of the laterally adjustable blades may be varied depending on, for example, the desired width of the retractor blade assembly in the expanded configuration.  
      Continuing to refer to  FIGS. 25-29 , the adjustable blades  714 A-C may be adjustable from a laterally contracted configuration, illustrated in  FIG. 25 , to a laterally expanded configuration, illustrated in  FIG. 26 . In the illustrated embodiment, for example, the adjustable blades  714 A-C assume a laterally contracted configuration when the adjustable blade assembly  714  is in a proximal position and expand laterally when the adjustable blade assembly  714  is advanced to a distal position. The adjustable blades  714 A-C, in the illustrated embodiment, are interconnected at pivot point  715  such that the laterally adjustable blades  714 A &amp;  714 C expand laterally in the manner of a fan. The laterally adjustable blades  714 A &amp;  714 C are pivotable about the pivot point  715  from a laterally contracted or collapsed position, in which the longitudinal axis of each adjustable blades  714 A-C are oriented approximately parallel to the longitudinal axis  716  of the fixed blade  712 , to a laterally expanded position, in which the longitudinal axis of each of the laterally adjustable blades  714 A &amp;  714 C is oriented at an angle to the longitudinal axis  716  of the fixed blade  712 . In certain exemplary embodiments, including the illustrated embodiment, the laterally adjustable blades  714 A &amp;  714 C may be biased to the laterally expanded configuration. In the illustrated embodiment, for example, the adjustable blade assembly  714  includes a torsion spring  719  to bias the laterally adjustable blades to the laterally expanded configuration.  
      In certain exemplary embodiments, the fixed blade  712  may be configured to constrain the laterally adjustable blades in a laterally contracted or collapsed configuration. For example, in the illustrated embodiment, the fixed blade  712  has a generally C-shaped cross-section defined by two spaced apart arcuate sidewalls  721 A,B, as illustrated in  FIG. 27 . The laterally adjustable blades  714 A &amp;  714 C may be engaged by the sidewalls  721 A,B to constrain the adjustable blade assembly  714  in the laterally contracted configuration when the adjustable blades  714 A-C are at least partially withdrawn into the fixed blade  712 .  
      In certain exemplary embodiments, in particular embodiments in which the laterally adjustable blades are biased to a laterally expanded configuration, the adjustable blade assembly  714  may include a mechanism to limit the lateral expansion of the laterally adjustable blades  714 A &amp;  714 C. For example, in the illustrated embodiment, each of the adjustable blades  714 A-C includes a pin  723  that is configured to engage a slot  725  in an adjacent adjustable blade. The slots  725  may be shaped and oriented to control the lateral adjustment of the laterally adjustable blades  714 A and  714 C. For example, in the illustrated embodiment, each slot  725  is arcuate in shape to facilitate lateral adjustment of the laterally adjustable blades  714 A &amp;  714 C along an arcuate path. One skilled in the art will appreciate that the shape and orientation of the slots  725 , as well as the position of the pins  723 , may be varied depending on the extent of lateral adjustment desired.  
       FIG. 30  illustrates another exemplary embodiment of an adjustable blade assembly  814  that includes a plurality of adjustable blades  814 A- 814 C, at least two of which, laterally adjustable blades  814 A and  814 C, are laterally adjustable relative to one another. In the illustrated embodiment, each adjustable blade  814 A-C includes a pair of spaced apart raised edges  829 ,  831 . The raised edges  829  are configured to engage raised edges  831  to limit lateral expansion of the laterally adjustable blades  814 A &amp;  814 C.  
       FIGS. 31 and 32  illustrate another exemplary embodiment of an adjustable blade assembly  914  that includes a plurality of laterally adjustable blades  914 A- 914 B, each of which is laterally adjustable relative to another adjustable blade, for example, center adjustable blade  914 C, which is not laterally adjustable, as well as each other. In the illustrated embodiment, the laterally adjustable blades  914 A and  914 B are independently laterally adjustable along an axis that is transverse to the longitudinal axis of the fixed blade. The center adjustable blade  914 C includes two spaced apart pins  923 A and  923 B each of which engages a slot  925 A,  925 B in a respective one of the laterally adjustable blades  914 A and  914 B. The slots  925 A,  925 B are linear in shape and oriented generally perpendicular to the longitudinal axis of the fixed blade and the center adjustable blade  914 C. One skilled in the art will appreciate that the slots  925 A,B may have a variety of shapes and may be oriented in a variety of orientations, depending, for example, on the desired lateral width of the retractor blade assembly:  
       FIG. 33  illustrates another exemplary embodiment of an adjustable blade assembly  1014  that includes a plurality of laterally adjustable blades  1014 A- 1014 B, which are laterally adjustable relative to one another. In the illustrated embodiment, the laterally adjustable blades  1014 A and  1014 B are independently laterally adjustable along an axis that is transverse to the longitudinal axis of the fixed blade. The laterally adjustable blades  1014 A and  1014 B, in the illustrated embodiment, are pivotally connected about a pivot pin  1015  that couples the laterally adjustable blades  1014 A and  1014 B to a central adjustable blade  1014 C. One or more of the laterally adjustable blades  1014 A and  1014 B may include a slot  1031  or other structure to facilitate lateral adjustment of the laterally adjustable blades  1014 A and  1014 B, for example, with an instrument.  
      While the retractor blade assemblies, instruments, and methods of the present invention have been particularly shown and described with reference to the exemplary embodiments thereof, those of ordinary skill in the art will understand that various changes may be made in the form and details herein without departing from the spirit and scope of the present invention. Those of ordinary skill in the art will recognize or be able to ascertain many equivalents to the exemplary embodiments described specifically herein by using no more than routine experimentation. Such equivalents are intended to be encompassed by the scope of the present invention and the appended claims.