Patent Publication Number: US-2023149007-A1

Title: Retractor Blades For Modular Retractor System And Method Of Use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/155,903, filed Jan. 22, 2021, entitled “Retractor Blades for Modular Retractor System and Method of Use,” and published Nov. 4, 2021 as U.S. Application Publ. No. 2021/0338220, which application claims the benefit of Provisional Patent Application No. 62/939,143, filed on Nov. 22, 2019, and titled “MODULAR RETRACTOR SYSTEM.” The entire disclosures of the applications above are incorporated herein by reference. 
    
    
     BACKGROUND 
     Retractor systems may be used in a variety of different surgical procedures to provide an opening through which the doctor may access the surgical site. In spinal surgeries, for example, a retractor system may be used to provide the surgeon with access to the patient&#39;s spine. The opening created by the retractor system may, for example, enable the doctor to insert surgical instruments into the body or enable visualization of the surgical site using X-ray. 
     Retractor systems may include a plurality of blades. In use, the blades may be inserted into an incision and then retracted to displace tissue surrounding the incision, thereby exposing the surgical site. To minimize trauma to the tissue, this tissue displacement should be refined and controlled. However, current retractor systems do not provide desired control of the distraction. More particularly, the devices currently in use limit the ability of the surgeon to feel the resistance at the blades as tissue is being retracted. The devices currently in use also limit the surgeon&#39;s ability to position and rotate the blades independently. This limited control takes away the skilled surgeon&#39;s ability to finely adjust the movement of the retractor blades. 
     There is a need in the art for a system and method that addresses the shortcomings discussed above. 
     SUMMARY 
     In one aspect, a retractor system used to retract tissue in preparation for an oblique lateral interbody fusion surgical procedure to fuse a vertebra to adjacent bony tissue includes a first retractor blade having a distal end with a flanged tip, a second retractor blade having a distal end with a cambered tip, and a connecting device that is configured to connect the first retractor blade to the second retractor blade. The flanged tip of the first retractor blade is configured to engage a posterior portion of the vertebra. The cambered tip portion of the second retractor blade is configured to engage an anterior portion of the vertebra. 
     In another aspect, a retractor system used to retract tissue in preparation for an oblique lateral interbody fusion surgical procedure to fuse a vertebra to adjacent bony tissue includes a first retractor blade having a first blade portion with a first length, a second retractor blade having a second blade portion with a second length, and a connecting device that is configured to connect the first retractor blade to the second retractor blade. An end of the first retractor blade is configured to engage a posterior portion of the vertebra. An end of the second retractor blade is configured to engage an anterior portion of the vertebra. The first length is substantially less than the second length. 
     In another aspect, a method of positioning a retractor system within a body in preparation for an oblique lateral interbody fusion surgical procedure to fuse a vertebra to adjacent bony tissue includes steps of inserting a first retractor blade having a flanged tip into an incision in the body, positioning the first retractor blade so that the flanged tip engages a posterior side of the vertebra, inserting a second retractor blade with a cambered tip into the incision in the body, positioning the second retractor blade so that the curved tip portion engages an anterior side of the vertebra, and securing the first retractor blade to the second retractor blade to fix their relative positions. 
     Other systems, methods, features and advantages of the embodiments will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the embodiments, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, with emphasis instead being placed upon illustrating the principles of the embodiments. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG.  1    is a schematic view of a modular retractor system in use during a surgical procedure, according to an embodiment; 
         FIG.  2    is a schematic view of a modular retractor system, according to an embodiment; 
         FIG.  3    is a schematic disassembled view of multiple components that comprise a modular retractor system, according to an embodiment; 
         FIG.  4    is a schematic view of a blade-to-blade articulating arm, according to an embodiment; 
         FIG.  5    is a schematic exploded view of a retractor blade, according to an embodiment; 
         FIG.  6    is a schematic cut-away view of a portion of a retractor blade, according to an embodiment; 
         FIG.  7    is a schematic view of a retractor blade assembly in an uncoupled configuration, according to an embodiment; 
         FIG.  8    is a schematic view of a retractor blade assembly in a coupled configuration, according to an embodiment; 
         FIG.  9    is a schematic view of two retractor blades inserted adjacent a segment of the spine, according to an embodiment; 
         FIG.  10    is a schematic view of an end of a table arm being coupled to a retractor blade, according to an embodiment; 
         FIG.  11    is a schematic view of fastening tool being used to couple an end of a table arm to a retractor blade, according to an embodiment; 
         FIG.  12    is a schematic perspective view of a connecting portion of a table arm being partially fastened to a retractor blade, according to an embodiment; 
         FIGS.  13 - 14    are schematic cross-sectional views of a connecting portion of a table arm being fastened to a retractor blade, according to an embodiment; 
         FIGS.  15 - 16    are schematic views of a retractor blade being temporarily fixed to bony tissue using a fixation pin, according to an embodiment; 
         FIGS.  17 - 21    are schematic views showing three retractor blades being coupled together using two blade-to-blade articulating arms, according to an embodiment; 
         FIG.  22    is a schematic view of three retractor blades aligned with a vertebrae to facilitate insertion of an implant, according to an embodiment; and 
         FIGS.  23 - 27    are schematic views of different retractor blade geometries, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments described herein are directed to a modular retractor system and its method of use. The modular retractor system comprises a set of retractor blades that can be used to retract soft tissue and anatomical features in preparation for a surgical procedure. The blades can be independently inserted and positioned adjacent a surgical site and then coupled together using one or more blade-to-blade articulating arms. One or more blades can also be coupled to a fixed structure, such as a surgical table, using a table arm which locks the position of the blade in place relative to the fixed structure. 
     Each retractor blade can be attached to a releasable handle. A surgeon can insert and manipulate the position of the retractor blade easily using the releasable handle. This enables the surgeon to receive important tactile feedback, reducing the chances of tissue damage caused by imprecise manipulation of the blades. Moreover, since each blade is positioned independently before it is fixed in place relative to the other blades, blade placement is not constrained to fixed spatial configurations, such as positions along a fixed ring or rectangle. Instead, each blade can be placed in an ideal location that is compatible with the particular patient&#39;s anatomy before the blades are securely fixed in place and locked to the operating table. 
     Because the blade-to-blade articulating arms provide a rigid connection between the blades, this eliminates the need for more than one table arm in the surgical area and reduces the need for additional assistance in holding the blades in place. 
     The embodiments describe a particular use of the modular retractor system in preparing an incision for oblique lateral interbody fusion (or OLIF) spinal surgery. OLIF is a less invasive approach to spinal fusion surgery in which the surgeon accesses and repairs the lower (lumbar) spine from the front and side of the body (passing in a trajectory about halfway between the middle of the stomach and the side of the body). During an OLIF procedure, the surgeon uses a corridor between the psoas muscle and the peritoneum to access the spine. The psoas muscles connect the lower back to the thighs and enable movement and flexibility of the back, pelvis, legs, and hips. The peritoneum is the membrane that lines the abdominal cavity. 
     Although the embodiments describe a particular configuration of the retractor system for use with OLIF procedures, it may be appreciated that the retractor system could be used for retracting skin and other tissue during other types of suitable surgeries. Moreover, for use in other kinds of surgeries, in some cases, the linkages between the blades as well as the specific configuration of blades themselves could vary from the configurations described below. 
     The terms “proximal” and “distal” may be used in the description. As used herein, proximal means closer a surgeon or person holding a component, while distal means further from the surgeon or person holding the component. Likewise, the terms “posterior” and “anterior” may be used in the description. A structure (part, portion, etc.) is anterior to another structure when it is closer to the front of the body. A structure that is posterior to another is closer to the back of the body. 
       FIG.  1    is a schematic view of a patient undergoing surgery. Specifically, patient  101  is undergoing a spinal fusion procedure that uses the oblique lumbar interbody fusion (OLIF) approach. In this particular example, the patient is undergoing surgery at the L 5 -S 1  spinal motion segment, also known as the lumbosacral joint. As shown in an enlarged focal view within  FIG.  1   , a retractor system  100  is being used to retract soft tissue and anatomical features in preparation for the procedure. Also visible in  FIG.  1    is a segment  150  of the spinal column, which includes portions of the lumbar spine and the sacral spine in the lower back. For purposes of illustration, a portion of the vascular system  160  is also shown in  FIG.  1   , as OLIF surgery typically requires mobilization of at least some portions of this system, such as the iliac and femoral arteries. For reference, the left common femoral artery is indicated in  FIG.  1    as artery  162 . 
       FIG.  2    is a schematic view of retractor system  100  shown in isolation. Additionally,  FIG.  3    shows a schematic top down view of the various components that may comprise retractor system  100  in a disassembled configuration. 
     Referring now to  FIGS.  2  and  3   , retractor system  100  may include one or more retractor blades. In the illustrated embodiment, retractor system  100  includes a first retractor blade  202 , a second retractor blade  204 , and a third retractor blade  206 . Together, the three retractor blades may be used to retract opposing sides of an incision, as well as to mobilize distinct portions of the anatomy, thereby creating an opening for an oblique lateral approach to the lumbar spine. As discussed in further detail below, the ends of each blade may be curved or otherwise shaped in a manner that assists in retraction of soft tissue and/or bone. For example, some retractor blades could be vein retractors, which tend to have flanged or curled ends that can be used to displace veins or other soft tissue. Other retractor blades could be Hohmann retractors, which may have a rounded tip that facilitates positive engagement with the bone. 
     In the exemplary configuration, each of the three retractor blades may be utilized for a particular function in preparing the surgical site for an OLIF procedure. For example, first retractor blade  202  may be designed for placement medially of the left common iliac vein, for a left sided up approach, or medially of the right common iliac vein/artery, for a right sided up approach. Second retractor blade  204  may be designed for placement medially for the right common iliac vein/artery, for a left sided up approach, or medially of the left common iliac vein/artery for a right sided up approach. Third retractor blade  206  may be designed for placement caudally of the bifurcation of the veins/arteries. 
     Retractor system  100  may be further comprised of components for attaching blades to one another in a manner that fixes the relative positions of the blades in a substantially rigid manner. In the illustrated embodiment, as shown in  FIG.  2   , retractor system  100  includes a first blade-to-blade articulating arm  220  and a second blade-to-blade articulating arm  222 . As further shown in  FIG.  2   , first blade-to-blade articulating arm  220  is seen to connect first retractor blade  202  with third retractor blade  206 . Likewise, second blade-to-blade articulating arm  222  is seen to connect second retractor blade  204  with third retractor blade  206 . 
     To keep the retractor blades in an absolute fixed position, relative to the operating table, another articulating assembly may be used. For example, as seen in  FIG.  3   , a table arm  250  could be used. Unlike the blade-to-blade articulating arms, table arm  250  may be used to connect a blade to a fixed structure in the operating area. Examples of fixed structures include, but are not limited to: operating tables, guide rails (on a bed or table), and/or any other structure in an operating area whose position is fixed during the procedure. 
     Table arm  250  may comprise an articulating arm portion  252  and a clamp portion  254 . Articulating arm portion  252  may further comprise a base segment  260 , a first articulating segment  262 , a second articulating segment  264 , and a fastening segment  266 . When assembled, the free end of segment  260  may be attached directly to clamp portion  254 . 
     First articulating segment  262  may be coupled to base segment  260  by a ball-and-socket connector  270 , thereby allowing first articulating segment  262  to articulate relative to base segment  260 , as the position and orientation of the latter may be fixed relative to clamp portion  254 . Second articulating segment  264  may be coupled to first articulating segment  262  by a rotating connector  272 . As seen in  FIG.  3   , rotating connector  272  may include a handle  273  that can be used to tighten the connection and lock the rotational angle between the adjacent articulating segments. 
     Fastening segment  266  may be coupled to second articulating segment  264  by another ball-and-socket connector  274 . Fastening segment  266  may further include a fastener  276 , which can be connected to corresponding fasteners on the retractor blades as discussed in more detail below. 
     Referring again to  FIG.  1   , table arm  250  can be fixed at a first end to a rail  180  of an operating table via clamp portion  254 . Clamp portion  254  may be any type of mechanism suitable for removably securing table arm  250  to rail  180 . Fastening segment  266  can be fastened to a retractor blade (e.g., retractor blade  202 ), thereby holding the blade in a fixed position relative to rail  180 . The connection between fastening segment  266  and retractor blade  202  can be better seen in  FIG.  2   . (For purposes of illustration, only a portion of table arm  250  is shown in  FIG.  2   .) 
     Although the exemplary embodiment shows a system comprised of three blades, in other embodiments only two blades could be used to retract an incision for a surgical procedure. In such an embodiment, the system may require only one blade-to-blade articulating arm to connect the two blades. Likewise, in still other surgical procedures, three or more blades could be used. When three or more blades are used, additional blade-to-blade articulating arms could be used to connect the additional blades to one of the first two blades. 
     To facilitate positioning the retractor blades, the system may include a releasable handle for each blade. Once the retractor blade(s) are positioned, one or more of the releasable handles may be removed, e.g., via quick connect connections, from the blades in order to reduce clutter in the operating field. 
     As seen in  FIG.  3   , a retractor system can also include a releasable handle  302 . Releasable handle  302  may be releasably attached to a retractor blade (such as first blade  202 , second blade  204 , or third blade  206 ). Releasable handle  302  may itself be further comprised of a grasping portion  310  and a connector portion  312 . In one embodiment, releasable handle  302  may be a quick connect (QC) handle that utilizes a quick connection fastening system. Although a single releasable handle  302  is shown in  FIG.  3   , it may be appreciated that each blade may be configured with its own releasable handle. 
     To assist in fastening the components of a retractor system to one another, a fastening tool such as hex driver  320  could be used, as described in further detail below. For purposes of clarity a single hex driver is shown in  FIG.  3   , however in other embodiments two or more different hex drivers may be used with a retractor system. In some embodiments, such a hex driver tool may be included with a kit of parts including all of the retractor components. 
       FIG.  4    is a schematic view of a blade-to-blade articulating arm  400  (“assembly  400 ”). Referring to  FIG.  4   , assembly  400  may comprise a first segment  402  and a second segment  404 . First segment  402  and second segment  404  may overlap at corresponding inward ends (that is, ends located towards the center of the assembly). Moreover, these segments may be connected in a manner that facilitates rotation about a common axis  410 . A rotating handle  412  also rotates about the same common axis  410  and allows the rotational angle between the segments to be locked into place when tightened. 
     The outward ends of each segment include a blade-engaging connector that is pivotally connected to the segment by a ball-and-socket connector. Specifically, first segment  402  is attached at its outward end to a first blade-engaging connector  420  (“connector  420 ”) by way of a first ball-and-socket connector  430 . Likewise, second segment  404  is attached at its outward end to a second blade-engaging connector  422  (“connector  422 ”) by way of a second ball-and-socket connector  432 . To better illustrate the nature of the ball-and-socket connection, each blade-engaging connector is shown as exploded from its corresponding ball-and-socket connector. However, it may be appreciated that each blade-engaging connector may be fixedly attached to the male end of the associated ball-and-socket connector. 
     Each blade-engaging connector is configured with a ring of teeth that can engage corresponding teeth on one or more blades. Specifically, first connector  420  includes a ring of teeth  421 , while second connector  422  includes a ring of teeth  423 . 
     Each blade-engaging connector is also associated with a threaded fastener. For example, first connector  420  includes a first opening  440  that receives a first threaded fastener  450 . Likewise, second connector  422  includes a second opening  442  that receives a second threaded fastener  452 . These threaded fasteners are used to secure the first and second blade-engaging connectors to the retractor blades, as described below and shown, for example, in  FIGS.  12 - 14   . 
     As seen in  FIG.  4   , each of first connector  420  and second connector  422  has an inward portion, an outward portion, and a curved intermediate portion. For example, second connector  422  may include an outward portion  480 , an inward portion  482 , and an intermediate portion  484 . The outward portion includes teeth for engaging a blade and the inward portion includes an opening to receive a projection from a corresponding ball-and-socket connector. The curved intermediate portion creates a step-down like geometry between the outward and inward portions. This configuration may provide sufficient clearance between the articulating arm and a connector on a retractor blade. Specifically, when the outward end of the connector is attached to a first connector on a retractor blade, the inward end may be displaced away from the blade by a sufficient vertical distance so that the inward end does not come into contact with a second connector on the blade, even as the arm is pivoted about the first connector prior to tightening the connection. 
       FIG.  5    is a schematic exploded view of an embodiment of a retractor blade  500 . In this embodiment, retractor blade  500  may itself be comprised of a blade portion  502 , a mounting portion  504 , and a releasable connector portion  506 . 
     Blade portion  502  may be substantially straight along its length and may include a first side  590  and a second side  592 . The first side may define a first direction that extends away from the first side and which is normal to the first side. The second side may define a second direction that extends away from the second side and which is normal to the second side. 
     Mounting portion  504  may be continuously formed with blade portion  502 , however mounting portion  504  may have a different orientation from blade portion  502 . For example, in the embodiment of  FIG.  5   , a planar surface  510  associated with the length and width of blade portion  502  may be disposed at an angle to a planar surface  512  associated with the length and width of mounting portion  504 . Here, mounting portion  504  is seen to extend away from second side  590  of blade portion  502 . Because the mounting portion is oriented along the direction of the handle, this orientation for mounting portion  504  relative to blade portion  502  allows a surgeon to better grasp and manipulate the retractor blade as it is inserted into the body. 
     Mounting portion  504  may comprise two fastener openings: a first fastener opening  530  and a second fastener opening  532 . Each opening may overlap with a corresponding opening on releasable connector portion  506 . Specifically, fastener opening  530  may correspond to a fastener opening  540  in releasable connector portion  506 , while fastener opening  532  may correspond to a fastener opening  542  in releasable connector portion  506 . These openings may further receive a first threaded connector  550  (through fastener opening  530  and fastener opening  540 ) and a second threaded connector  552  (through fastener opening  532  and fastener opening  542 ). Each connector includes threading that can engaging corresponding threading in the openings of releasable connector portion  506 . When fastened into place, these connectors secure releasable connector portion  506  to mounting portion  504 . 
     Additionally, each connector includes a ring comprised of teeth. Specifically, first connector  550  includes an outer ring  560  that is comprised of teeth  562 . Likewise, second connector  552  includes an outer ring  570  that is comprised of teeth  572 . The teeth of each connector are configured to engage corresponding teeth in one or more of the articulating arms (such as teeth  421  or teeth  423  shown in  FIG.  4   ). 
     As seen in  FIG.  5   , releasable connector portion  506  includes a quick connect end  580  that is sized and shaped to mate with a corresponding opening in a quick connect handle (such as handle  302  of  FIG.  3   ). 
       FIG.  6    is a schematic perspective cross-sectional view of a portion of retractor blade  500 . Referring to  FIG.  6   , retractor blade  500  may include a first surface  602  and an opposing second surface  604 . When inserted into the body, second surface  604  may be placed against soft tissue and/or bone in order to retract or pull at the tissue. First surface  602  may face inwardly towards a cavity created inside the body by the use of two or more retractor blades. In some cases, the body of retractor blade  500  may be curved so that first surface  602  takes on a concave geometry, while second surface  604  takes on a convex geometry. The curvature of retractor blade  500  may help provide additional strength and support over a substantially flat blade. Additionally, when used in conjunction with other concave blades, the concavity of the blades provides an enlarged opening through which the surgery may be performed. Further, the convex geometry of second surface  604  may be more gentle to tissue being retracted. 
     Along first surface  602 , retractor blade  500  may further include two slots for receiving fixation pins (such as Steinman pins), K wires, or other devices used for fixation. Specifically, retractor blade  500  may include a first slot  620  adjacent one edge, and a second slot  622  adjacent the other edge. 
     First surface  602  can further include a T-shaped channel  630  that runs through the center of the blade along a lengthwise direction. Channel  630  may accommodate an illumination device. For example, in  FIG.  7    an illumination device  750  can be seen extending through channel  630 . Illumination device  750  could be a strip-like device that provides illumination, allowing a surgeon to better visualize the area where the blade has been inserted. Using a channel inside the surface of the blade allows the illumination device to be integrated into the blade without the illumination device protruding from the blade&#39;s surface, possibly impacting adjacent tissue. In one embodiment, the illumination device comprises a sheath or segment of malleable aluminum, so that once inserted to the desired position within channel  630 , the proximal end of the illumination device may be bent back to help keep the device in place and out of the way of the surgeon. 
     It may be appreciated that one or more blades in a retractor system could include slots for fixation devices (like pins) and/or channels for illumination devices. In the exemplary embodiment, both first blade  202  and third blade  206  are configured with these slots and channels, as seen in  FIG.  2   . 
       FIGS.  7  and  8    depict configurations of retractor blade  500  and a corresponding releasable handle  702 , which are collectively referred to as blade assembly  700 . Specifically,  FIG.  7    shows retractor blade  500  disconnected from releasable handle  700 , while  FIG.  8    shows retractor blade  500  connected to releasable handle  700 . By using a quick connection between the blade and handle, a surgeon can easily remove the handle once the blade has been placed in the desired position, thereby helping clear the operative area of unnecessary components. This also reduces any chance that the handles may interfere with the placement of one or more articulating arms (either the blade-to-blade arms or the table arm). 
       FIGS.  9 - 21    depict schematic views of a procedure for assembling the retractor system at a surgical site in a manner that allows each blade to be individually inserted and positioned by a surgeon before the relative positions of the blades are fixed with respect to one another. For purposes of clarity, the exemplary procedure describes a process for inserting and assembling the retractor system in preparation for an OLIF surgical procedure. However, it may be appreciated that similar steps could be performed in preparing different parts of the body for other kinds of procedures. For purposes of illustration, only the components of retractor system  100  are shown, however it may be appreciated that the components are inserted, moved, and connected by a surgeon and/or surgical assistant(s). 
     After an incision has been made and dissection to the spinal segment of interest (such as the L 5 -S 1  segment) is completed, a surgeon may insert first retractor blade  202  and second retractor blade  204  into the incision area, as seen in  FIG.  9   . In some cases, an illumination device  910  may be used with first retractor blade  202  to more easily identify the L 5 -S 1  disc via direct visualization. As seen in  FIG.  9   , first retractor blade  202  is coupled to releasable handle  902 , and second retractor blade  204  is coupled to releasable handle  904 . Using these handles facilitates easier blade manipulation for the surgeon. 
     Upon insertion, second blade  204  may be used to retract the medial aspect of the incision (not shown) and first blade  202  may be used to retract the lateral aspect of the incision. Moreover, first blade  202  may be placed on the medial or inner aspect of the left common femoral (artery  920 ) artery to ensure there are no peritoneal contents between the blade and the L 5 -S 1  disc. Second blade  204 , meanwhile, may be used to gently mobilize the prevertebral fascia over the L 5 -S 1  disc space. 
     With the two blades inserted, first blade  202  can be provisionally attached to table arm  250 , which may have been previously clamped to a rail or other fixed structure. As seen in  FIG.  10   , table arm  250  can be attached to first blade  202  by placing fastener  276  over a corresponding connector on first blade  202 . 
     As shown in  FIG.  9   , first retractor blade  202  can include first connector  950  and second connector  952 . Fastener  276  can be attached to first connector  950  of first retractor blade  202  by either hand tightening fastener  276  or by using a fastening tool. In the example shown in  FIG.  11   , hex driver  320  may be used to tighten fastener  276 . Hex driver  320  may include an opening at its end that engages the hexagonal shaped body of fastener  276 . 
       FIGS.  12 - 14    illustrate views of a connecting portion  1220  of table arm  250  being fastened to a portion of a retractor blade  1200 . For purposes of illustration, connecting portion  1220  is shown in isolation. In  FIG.  12   , connecting portion  1220  is aligned with a connector  1202  of retractor blade  1200 , so that fastener  1230  can be inserted through a corresponding hole in connector  1202 . Referring next to the cross-sectional views of  FIGS.  13  and  14   , the threading  1232  of fastener  1230  may engage corresponding threading  1204  that is disposed in the interior cavity  1206  of connector  1202 . Rotating fastener  1230  by hand or using a tool drives the end of connecting portion  1220  towards connector  1202 . As seen in  FIG.  14   , when fully fastened, teeth  1222  on connecting portion  1220  may engage teeth  1208  on connector  1202  to prevent any rotation between connecting portion  1220  and connector  1202 . 
     It may be appreciated that this same connection mechanism can be used to connect the ends of any of blade-to-blade articulating arms with connectors on any of the retractor blades. In particular, each of the blade-to-blade articulating arms may be configured with similar connecting portions that can be fastened to connectors on the retractor blades. 
     Referring now to  FIGS.  15  and  16   , with table arm  250  now secured to first retractor blade  202 , retractor blade  202  can be further positioned if needed and then secured to the sacrum using a fixation device. In the exemplary embodiment, a fixation pin  1510  is inserted into a corresponding slot of the first retractor blade  202 . With the pin inserted, hex driver  1504  can be placed over the head of the pin. A mallet  1502  can be used to initiate insertion of the pin into the bone ( FIG.  15   ). The hex driver  1504  can then be used to fully insert the pin  1510  into sacrum  1520 . 
       FIG.  16    shows retractor blade  202  secured to sacrum  1520  after both fixation pin  1510  and fixation pin  1512  have been inserted into the bone using the above method. 
     After first retractor blade  202  has been secured to sacrum  1520  using pins, any additional tightening of the connection between first retractor blade  202  and table arm  250  can be done. Optionally, first releasable handle  902  can be disconnected from retractor blade  202  and removed from the operating area, as shown in  FIG.  17   , since first retractor blade  202  no longer needs to be manipulated during the procedure. 
     Third retractor blade  206  (with releasable handle  906  attached) can also be inserted at this time. In this example, third retractor blade  206  is inserted at the bifurcation  1704  of the artery. The surgeon can then manually adjust the position of third retractor blade  206  as needed independently of the positions of both first retractor blade  202  and second retractor blade  204 . 
     As shown in  FIG.  18   , third retractor blade  206 , once positioned, can be secured to first retractor blade  202  using first blade-to-blade articulating arm  220 . Specifically, a first end  1802  of first blade-to-blade articulating arm  220  is fastened to second connector  952  (see  FIG.  17   ) of first retractor blade  202 . A second end  1804  of first blade-to-blade articulating arm  220  is then fastened to a connector  1702  (see  FIG.  17   ) of third retractor blade  206 . These components may be fastened together in a similar manner to the fastening of table arm  250  to first retractor blade  202 , a depicted in  FIGS.  12 - 14   . As seen in  FIG.  18   , a hex driver  1820  may be used to tighten the corresponding fasteners on assembly  220 . 
     The dynamic range of motion that can be accomplished by blade-to-blade articulating arm  220  by way of the ball-and-socket connections at its ends, and the twisting connection at its center, allows blade-to-blade articulating arm  220  to adapt to any relative configuration of first retractor blade  202  and third retractor blade  206 . Moreover, rotating handle  1810  can be used to lock the two main segments of the assembly in place. Once attached to both first retractor blade  202  and third retractor blade  206 , first articulating arm  220  may provide a rigid connection between the blades that locks their relative positions in place. At this point, releasable handle  906  can be released from third retractor blade  206 , as indicated in  FIG.  19   . 
       FIG.  20    illustrates the system once second blade-to-blade articulating arm  222  has been used to fix the position of second retractor blade  204 . Specifically, second blade-to-blade articulating arm  222  has been secured to third retractor blade  206  at one end, and to second retractor blade  204  at another. Once second blade-to-blade articulating arm  222  has been fastened in place and tightened as needed, second releasable handle  904  can be released from second retractor blade  204 , as seen in  FIG.  21   . 
     In this final configuration, each retractor blade is fixed in place relative to one another. Specifically, third retractor blade  206  has a fixed position relative to first retractor blade  202  by way of first blade-to-blade articulating arm  220 . Likewise, second retractor blade  204  has a fixed position relative to third retractor blade by way of second blade-to-blade articulating arm  222 . And second retractor blade  204  and first retractor blade  202  have fixed relative positions by way of their mutual attachments to third retractor blade  206 . Additionally, the attachment of first retractor blade  202  to table arm  250  fixes the positions of the blades within the operating area. 
       FIG.  22    depicts a schematic view of the retractor system aligned with a vertebra  2202  along a transverse plane through the body. As seen in  FIG.  22   , different blades may have different shaped distal ends (or tips) to perform different functions in preparing for an implant. For example, first retractor blade  202  includes a flanged tip  2210  at its distal end that facilitates both retraction of the incision and may help support and stabilize first retractor blade  202  against a posterior portion of vertebra  2202  during and after the fixation of the blade to vertebra  2202  using Steinman pins (as in  FIG.  16   ). In some embodiments, the flanged tip  2210  may be bent at an approximately  90  degree angle away from the rest of first blade portion  2230 . Third retractor blade  206  may also have a flanged tip (see, for example, the side view of third blade  206  in  FIG.  3   ) to hold the bifurcation of the artery in place. By contrast, the second retractor blade  204  has a slightly curved (or “cambered”) tip  2212  at its distal end. This slight curvature of end  2212  helps the end of second retractor blade  204  to better accommodate the convex surface along an anterior portion  2242  of vertebra  2202 . 
     As illustrated in  FIG.  22   , the curvature of flanged tip  2210  is substantially greater than the curvature of cambered tip  2212 . For clarity, the radius of curvature of each tip is indicated within enlarged views of  FIG.  22   . Flanged tip  2210  has a first radius of curvature  2250  and cambered tip  2212  has a second radius of curvature  2252 , which is substantially larger than first radius of curvature  2250 . This increased radius of curvature corresponds with a smaller relative curvature for cambered tip  2212 , as curvature is inverse to the radius of curvature. 
     Not only is the degree of curvature different between flanged tip  2210  and cambered tip  2212 , but the direction of curvature is also different. Flanged tip  2210  bends towards a direction that is normal to second side  2231  of first blade portion  2230 . In other words, flanged tip  2210  bends behind the first retractor blade as it faces towards a retracted opening in the body. This ensures that flanged tip  2210  can be used to retract and keep tissue away from the retracted opening. 
     By contrast, cambered tip  2212  bends towards a direction that is normal to first side  2233  of second blade portion  2232 . This creates a concave surface for cambered tip  2212  along the first side  2233  of second blade portion  2232 . This concave surface is adapted to engage the convex surface of anterior portion  2242  of vertebra  2202 . 
       FIG.  22    also illustrates the difference in length between first retractor blade  202  and second retractor blade  204 . Here, first blade portion  2232  of second retractor blade  204  is seen to be slightly longer than a corresponding second blade portion  2230  of first retractor blade  204 . The difference in length accommodates the different distances between the incision and different locations along the vertebra. In particular, the distance between the incision and posterior portion  2240  of vertebra  2202  is slightly less than the distance between the incision and anterior portion  2242  of vertebra  2202 , due to the orientation of the body during the OLIF procedure. Thus, first retractor blade  202  has a slightly shorter length than the length of second retractor blade  204 , to accommodate these different distances and ensure the end of each retractor blade is able to engage the appropriate portion of vertebra  2202 . For purposes of illustration, the different lengths for first retractor blade  202  and second retractor blade  204  are indicated in  FIG.  3   , as first length  290  and second length  292 , respectively. 
     In one embodiment, a ratio between the first length and the second length may be in a range between approximately  90  percent and approximately  97  percent. That is, first blade portion  2230  may be somewhere between 90 percent to 97 percent shorter than second blade portion  2232 . In one embodiment, first blade portion  2230  has a length of  140  mm, while second blade portion  2232  has a length of 150 mm. In another embodiment, first blade portion  2230  has a length of approximately 170 mm, while second blade portion  2232  has a length of approximately 180 mm. In another embodiment, first blade portion  2230  has a length of approximately 200 mm, while second blade portion  2232  has a length of approximately 210 mm. 
     Once retraction is complete, discectomy and endplate preparation will be completed. Next, an implant specifically designed for the OLIF approach (approximately 25° off the coronal plane) will be implanted. When inserted using an approach 25° off the coronal plane, the lordosis of the implant will be correctly aligned with the lordosis of the spine. In  FIG.  22   , following retraction, an implant  2204  has been successfully inserted between vertebra  2202  and an adjacent vertebra or part of the sacrum. 
     In some embodiments, each of the three blades that comprise the retractor system could have different geometries and/or dimensions. In one embodiment, for example, first retractor blade  202  has the geometry of retractor blade  500  shown in  FIG.  5   . The geometry of third retractor blade  206  may be similar to that of first retractor blade  202  with some modifications. As an example, in some embodiments, third retractor blade  206  may have the geometry of the blade shown in  FIG.  23   . The geometry of blade  2302  may be similar in some respects to retractor blade  500 . In particular, retractor blade  2302  may include similar channels  2320  for receiving Steinman pins, as well as a central channel  2322  for receiving an illumination device. However, in some cases, retractor blade  2302  may be substantially narrower than retractor blade  500 . For example, in one embodiment, first retractor blade  202  could have a width of approximately 30 mm, while third retractor blade  206  could have a width of approximately 20 mm. This narrower width may help third retractor blade  206  to better fit into the bifurcation of an artery. 
     In some embodiments, second retractor blade  204  may have a similar geometry to retractor blade  2402  shown in  FIG.  24   . As seen in comparing  FIGS.  23  and  24   , retractor blade  2402  has a slightly different geometry to retractor blade  2302 . Specifically, retractor blade  2402  lacks channels for receiving pins, though it does include a central channel  2404 . Additionally, the rounded tip  2406  may help engaging tissue for mobilization. 
     Still other variations in blade design are possible. For example,  FIGS.  25  through  27    illustrate schematic views of variations in the geometry of the blade ends. For example, some embodiments could include a blade  2502  with a substantially straight end  2504 , as depicted in  FIG.  25   . Some embodiments could include a blade  2602  with a bent end  2604  having a convex tip  2606 , as depicted in  FIG.  26   . Other embodiments could include a blade  2702  with a bent end  2704  having a concave tip  2706 , as depicted in  FIG.  27   . The type of blade tip geometry may be selected according to the type of tissue that must be retracted. 
     As already discussed, the modular retraction system of the embodiments is configured to build a rigid frame outside of the body after the blades have been properly positioned by hand and pinned to a vertebral body. 
     The present system gives the surgeon the flexibility to place the blades wherever they want without being limited by a rigid frame. This ensures that the blades are placed perfectly every time based on unique anatomic structures while still providing a rigid frame once the components of the system have been assembled and tightened. Placing the retractor blades by hand provides the surgeon with tactile feedback to help reduce the risk of vascular injury. Blade to blade fixation eliminates the need for someone (typically a physician assistant) to hold one of the blades in place during the procedure. If two blade to blade connections are used, this eliminates the need for a second table arm and removes clutter from the sterile field. 
     While the exemplary embodiments describe using the modular retractor system to prepare for an OLIF approach at L 5 -S 1  between the bifurcation, it can also be utilized for an OLIF approach at levels higher up in the lumbar spine. Furthermore, the retractor blades could be utilized for any surgical approach, spine or otherwise, that requires soft tissue retraction. 
     It is contemplated that in some embodiments interchangeable parts of a modular retractor system could be prepared as kits that can be accessed prior to, or during, a surgical procedure. The kits could be prepared to include multiple retractor blades, releasable handles, blade-to-blade articulating arms, table arms, fixation pins, fastening tools such as hex drivers, and illumination devices. 
     For each of the three retractor blades described above (e.g., first retractor blade  202 , second retractor blade  204 , and third retractor blade  206 ) a kit could be configured with interchangeable blades having different dimensions (for example, different lengths). As an example, a kit could include three different sizes associated with first retractor blade  202 . These could include a 140 mm length blade, a 170 mm length blade, and a 200 mm length blade. Additionally, a kit could include three different sizes of retractor blades associated with second retractor blade  204 . These could include a 150 mm length blade, a 180 mm length blade, and a 210 mm length blade. Furthermore, a kit could include three different sizes of retractor blades associated with third retractor blade  206 . These could include a 140 mm length blade, a 170 mm length blade, and a 200 mm length blade. 
     While various embodiments have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the embodiments. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Any feature of any embodiment may be used in combination with or substituted for any other feature or element in any other embodiment unless specifically restricted. Therefore, it will be understood that any of the features shown and/or discussed in the present disclosure may be implemented together in any suitable combination. Accordingly, the embodiments are not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.