Patent Publication Number: US-11647998-B2

Title: Tissue dilation system and methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 16/071,033, filed on Jul. 18, 2018 as a national stage entry of International Application No. PCT/US2017/014068, filed on Jan. 19, 2017, which claims priority to, and the benefit of, U.S. Provisional Application Ser. No. 62/280,198 which was filed on Jan. 19, 2016, the entire contents of each of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to surgical dilation systems. More particularly, the present disclosure relates to a tissue dilation system and methods of use. 
     BACKGROUND 
     Development of minimally invasive surgical techniques has expanded to improve orthopedic surgical techniques. Such techniques have advanced the improvement of spinal surgeries, such as instrumental fusions involving one or more vertebral bodies. Unlike minimally invasive procedures which focus on smaller regions of the body, such as arthroscopic knee surgery or gallbladder surgery, spinal fusion surgery can encompass a considerable region of the body. 
     The spinal column is a complex system of bones and connective tissues that provide support for the human body and protection for the spinal cord and nerves. The adult spinal column is comprised of an upper and lower portion. The upper portion contains twenty-four discrete bones, which are subdivided into three areas including seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae. The lower portion is comprised of the sacral and coccygeal bones. The cylindrical shaped bones, called vertebral bodies, progressively increase in size from the upper portion downwards to the lower portion. 
     Minimally-invasive surgery, including arthroscopic surgery and laparoscopic surgery allow for the introduction of fluid (such as liquids or pressurized gasses) for distending tissue and creating working space for the surgeon to operate within. Spinal column surgery does not involve distending tissue to create a cavity in which the surgeon can operate, rather, spinal column surgery often involves interacting with multiple layers of soft tissue, ligaments, nerves, and ultimately bone. For these reasons, the idea of performing minimally invasive orthopedic surgeries has been the focus of many recent medical advances. 
     Minimally-invasive surgery techniques associated with orthopedic surgery often required a surgeon insert a guide wire through tissue toward a pedicle of the vertebral body. The guide wire thereby enabled the surgeon to accurately attach a pedicle screw to the vertebral body to later secure a rail or rod to the vertebral body. However, during installation, the guide wire may not be inserted to a sufficient depth in the vertebral body, resulting in detachment of the guide wire from the vertebral body prior to insertion of the pedicle screw. Disengagement of the guide wire may result in contamination and necessitate replacement of the guide wire. Additionally, a guide wire may deflect or break during the surgical procedure as a result of catching on a foreign object such as a surgeon&#39;s clothing. As a result of deflecting or breaking guide wires, the surgical procedure is prolonged as replacements are fitted as is necessary. 
     As a result, procedures or surgical instrument improvements associated with guiding pedicle screws to vertebral bodies are desirable. 
     SUMMARY 
     The present disclosure relates to a tissue dilation system including a trocar having an elongated body with a bore extending therethrough. A distal region of the elongated body has threads for engaging bone. A stylet is insertable into the bore. The system further includes a first dilator having an elongated body and translatable over an outer surface of the trocar, and an outer dilator having an elongated body and translatable over an outer surface of the first dilator. 
     The tissue dilation system may further include a handle portion configured to be removably attached to the trocar. 
     The handle portion may be configured to be removably attached to the first dilator. 
     The tissue dilation system may further have at least one temporary fixation pin with an elongated body and being translatable along an outer surface of the outer dilator. The temporary fixation pin may have a threaded distal region for engagement with bone. 
     The outer dilator may be configured to receive a surgical device to be translated within the outer dilator for engaging bone. 
     A retractor assembly having a retractor and a screw inserter assembly may also be provided. 
     The retractor assembly may further include a screw and a knob. 
     The present disclosure also provides a method for dilating tissue including inserting a trocar into a target surface. The trocar has a tubular member with a bore extending between proximal and distal regions thereof. The distal region includes threads for engaging bone. The method further includes coupling a stylet to the trocar such that a distal region of the stylet extends beyond the distal region of the trocar. Bone is contacted at the target surface with the distal region of the trocar. The stylet is separated from the trocar by translating a first dilator over the trocar towards bone at the target surface and translating an outer dilator over the first dilator. The outer dilator is then coupled to bone at the target surface. 
     The method for dilating tissue may include connecting the trocar with bone at the target surface. 
     Translating the first dilator over the trocar may include the first dilator having a serrated edge configured to engage with a target surface. 
     Translating the outer dilator over the first dilator may include the outer dilator having a distal region with a serrated edge configured to engage with a target surface. 
     Translating the first dilator over the trocar may include the first dilator having a bore configured for slidably receiving the trocar. 
     Translating the outer dilator over the first dilator may include the outer dilator having a bore configured to engage with an outer surface of the first dilator. 
     The method for dilating tissue may include removably attaching a handle to either the trocar or the first dilator. 
     The method for dilating tissue may include coupling the first dilator and the outer dilator prior to translating the first dilator over the trocar towards bone at the target surface. 
     The method for dilating tissue may include coupling the outer dilator to bone at the target surface by coupling a temporary fixation pin to bone at the target surface, the temporary fixation pin in communication with the outer dilator and having a threaded distal region configured to engage with the target surface. 
     The method for dilating tissue may include separating the trocar from the target surface. 
     The method for dilating tissue may include separating the first dilator from the target surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate embodiments of the tissue dilation system of the present disclosure. 
         FIG.  1    is a perspective view of a trocar for use in a tissue dilation system; 
         FIG.  2    is a front plan view of the trocar illustrated in  FIG.  1   ; 
         FIG.  3    is a cross-sectional view of the trocar of  FIG.  2    as taken along section line  3 - 3  of  FIG.  2   ; 
         FIG.  4    is a perspective view of the trocar of  FIG.  1    attached to a handle portion; 
         FIG.  5    is a front plan view of the trocar and handle portion of  FIG.  4   ; 
         FIG.  6    is a cross-sectional view of the trocar and handle portion of  FIG.  5    taken along section line  6 - 6  of  FIG.  5   ; 
         FIG.  7    is a perspective view of a tissue dilation system according to the present disclosure; 
         FIG.  8    is a plan view of the tissue dilation system of  FIG.  7   ; 
         FIG.  9    is a cross-sectional view of the tissue dilation system of  FIG.  8    as taken along section line  9 - 9  of  FIG.  8   ; 
         FIG.  10    is a perspective view of the trocar of  FIG.  1    and a first dilator according to the present disclosure; 
         FIG.  11    is enlarged view of the area of detail of  FIG.  10   ; 
         FIG.  12    is a front plan view of the trocar and first dilator of  FIG.  10   ; 
         FIG.  13    is a cross-sectional view of the trocar and first dilator of  FIG.  12    taken along section line  13 - 13  of  FIG.  12   ; 
         FIG.  14    is an exploded view, with parts separated, of an alternate embodiment of a tissue dilation system according to the present disclosure; 
         FIG.  15    is a perspective view of a further embodiment of a tissue dilation system according to the present disclosure; 
         FIG.  16    is an exploded view, with parts separated, of the tissue dilation system of  FIG.  15   ; 
         FIG.  17    is a side elevation view of the tissue dilation system of  FIG.  15   ; 
         FIG.  18    is a cross-sectional view of the tissue dilation system of  FIG.  17    taken along section line  18 - 18  of  FIG.  17   ; 
         FIG.  19    is an enlarged view of the area of detail of  FIG.  18   ; 
         FIG.  20    is an enlarged view of the area of detail of  FIG.  18   ; 
         FIG.  21    is a perspective view of a retractor collar; 
         FIG.  22    is a perspective view of an outer dilator; 
         FIG.  23 A  is a front plan view of the outer dilator of  FIG.  22   ; 
         FIG.  23 B  is a side plan of the outer dilator of  FIG.  22   ; 
         FIG.  24    is a cross-sectional view of the outer dilator of  FIG.  23 B , taken along section line  24 - 24  of  FIG.  23 B ; 
         FIG.  25 A  is a top plan view of the outer dilator of  FIG.  22   ; 
         FIG.  25 B  is a bottom plan view of the outer dilator of  FIG.  23 B ; 
         FIG.  26 A  is a side plan view of a temporary fastener; 
         FIG.  26 B  is a top view of the temporary fastener of  FIG.  26 A ; and 
         FIG.  27    is a front plan view of another embodiment of an outer dilator and the temporary fastener of  FIG.  26 A . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. 
     As used herein, the term “distal” refers to the portion of the component being described which is closer to a patient, while the term “proximal” refers to the portion of the component being described which is farther from the patient. 
     The term “clinician” as used herein refers to a doctor, nurse, healthcare provider which may include support personnel, or other operators of the surgical system described. 
     Additionally, the positional terms “front,” “rear,” “top,” “bottom,” “side,” and other like directional terms are used for convenience to assist the reader in understanding the present disclosure, and are not intended to limit the disclosure. 
     Referring initially to  FIG.  1   , a trocar  100  is shown including a proximal region  104 , a tubular member  106 , and a distal region  116 . The proximal region  104  includes a proximal end  102  which may be operably coupled to a stylet  300  (see  FIGS.  4 - 6   ). The proximal region  104  of the trocar  100  may further be dimensioned to receive a handle portion  200  thereon, (see  FIG.  4   ) or other surgical tools (not shown) useful for a dilation procedure. 
     The tubular member  106  of the trocar  100  extends between the proximal region  104  and the distal region  116  of the trocar  100 . The tubular member  106  may be configured and dimensioned for atraumatic advancement through tissue along a longitudinal axis A-A as the trocar  100  is advanced by a clinician toward a target surface (not shown). Likewise, the distal region  116  of the trocar  100  includes a tapered surface  108  located between the tubular member  106  and an engagement member  112  for promotion of atraumatic advancement of the trocar  100  through tissue and operative engagement with an inner dilator  400  (see  FIG.  7   ). The engagement member  112  may include a helical thread, barb, expanding lip, rotated or expanded cam, and other such shaped elements disposed on the outer surface  112 A (see  FIG.  3   ) of the engagement member to secure the trocar  100  to the target surface. The engagement member  112  further includes an engagement tip  114  which may include a single or multi-beveled tip for easy viewing via a sub-dermal imaging system as the trocar  100  is advanced toward a target surface. 
     Referring now to  FIGS.  2 - 3   , the trocar  100  includes a bore  118  which extends through the trocar  100  along the longitudinal axis A-A. The bore  118  is dimensioned to slidably receive a stylet  300  (see  FIG.  6   ) therein for selective engagement of the target surface by either a distal tip  308  of the stylet  300  or the engagement tip  114  (see  FIG.  6   ). The bore  118  may be dimensionally defined by an inner surface of the trocar  100 . 
     Referring now to  FIGS.  4 - 6   , the trocar  100  is shown in combination with a handle portion  200  and a stylet  300 . The handle portion  200  includes a handle member  202  which is capable of being gripped by a clinician&#39;s hand. The handle portion  200  may further include an extension  206  with one or more flanges  204  disposed thereon for engagement by a clinician about the longitudinal axis A-A during assembly and removal of the handle portion  200  from the trocar  100 . An engagement surface  208  may be located in the distal region of the handle portion  200 , defining a cavity  212  therein. The cavity  212  may be dimensioned to fixably receive the proximal region  104  of the trocar  100 . Additionally, the cavity  212  and the proximal region  104  of the trocar  100  may be dimensioned to transfer rotational or torsional force from the handle portion  200  to the trocar  100 . The cavity  212  and proximal region  104  of the trocar may be shaped in a variety of ways, including two or more sided shapes, asymmetrical shapes, or patterned shapes that are complementary such that cavity  212  is rotatably coupled with the proximal region  104  and removably coupled to the trocar  100 . 
     With continued reference to  FIGS.  4 - 6   , the handle portion  200  and trocar  100  may be combined with a stylet  300 . The stylet  300  includes a knob  302  having a knurled surface which may be gripped by a clinician. The knob  302  may further include threads  304  which operably engage threads  210  of the handle portion  200  for releasably coupling the stylet  300  and the handle portion  200 . The stylet  300  further includes a shaft  306  extending from the knob  302 , with the shaft  306  being configured and dimensioned for slidably engaging the bore  118  of the trocar  100 . Further still, the shaft  306  may be dimensioned such that when the stylet  300  is threadably coupled with the handle portion  200 , the distal tip  308  of the shaft  306  extends beyond a distal end of the engagement tip  114  of the trocar  100 . 
     Handle portion  200  may engage with trocar  100  via a spring collet (not shown). In the fixed position, the spring collet associated with handle portion  200  includes ball bearings which are located between the handle portion  200  and the trocar  100 . The ball bearings apply pressure against the trocar  100 , thereby maintaining the position of the handle portion  200  relative to the trocar  100 . To remove the handle portion  200 , the clinician applies upward force (i.e., proximal movement) to the handle portion  202  relative to the flanges  204 . By pulling the handle portion  202  proximally relative to the flanges  204 , the pressure applied to the ball bearings is reduced, thereby allowing the clinician to remove the handle  200 . The handle  200  is releasably coupled with the trocar  100  by releasing the handle portion  202 , thereby applying pressure against the ball bearings and trocar  100 . Alternatively, it is contemplated that the reverse arrangement may be employed where proximal movement of the flanges  204  relative to the handle portion  202  release pressure against the ball bearings allowing the handle  200  to be separated from the trocar  100 . 
     Referring now to  FIGS.  7 - 9   , a tissue dilation system “D” is shown with the trocar  100 , the handle portion  200 , an inner dilator  400 , and an outer dilator  500 . As shown, in combination, the handle portion  200  attaches to the trocar  100 . When the handle portion  200  is removed from the trocar  100 , the inner dilator  400  may be passed over the trocar  100 , and the outer dilator  500  may be passed over the inner dilator  400 . The inner dilator  400  may be dimensioned to selectively engage with the trocar  100  or the outer dilator  500  during assembly of the tissue dilation system “D” during a surgical dilation procedure. 
     With additional reference to  FIG.  10   , the inner dilator  400  includes a receiving portion  402 , a tubular member  404 , a tapered surface  406 , and a bore  408  (see  FIG.  13   ). The receiving portion  402  may be dimensioned to engage with a surgical tool (not shown) during the dilation procedure, the surgical tool permitting the clinician to apply force distally against the inner dilator  400 . Engagement of the receiving portion  402  with the surgical tool assists the clinician while advancing inner dilator  400  through tissue where the application of additional distal force is desired. The tubular member  404  extends between a proximal and distal region of the inner dilator  400  along longitudinal axis A-A defining the bore  408  therethrough. The tubular member  404  further includes a tapered surface  406  located in the distal region of the inner dilator  400  for atraumatically displacing tissue while the inner dilator  400  is advanced toward the target surface. 
     With continued reference to  FIGS.  7 - 9   , the outer dilator  500  includes two flanges  502  for a clinician to grip during the dilation procedure. The flanges  502  extend from the tubular member  504  of the outer dilator  500  in the proximal region of the tubular member  504 . The tubular member  504  may have one or more openings  510  located thereon, allowing a clinician to view a bore  518  defined through the tubular member  504 . The bore  518  of the outer dilator  500  is dimensioned to permit the outer dilator  500  to be passed over the inner dilator  400  such that the inner dilator  400  extends therethrough. Further, a clinician can view the progression of the outer dilator  500  over the inner dilator  400  through the one or more openings  510  of the outer dilator  500 . 
     Both the inner dilator  400  and the outer dilator  500  include tapered surfaces  406 ,  506  dimensioned to minimize unintentional engagement of tissue surrounding or located at the target surface by a clinician during the dilation procedure. The tapered surface  406 ,  506  of both the inner dilator  400  and outer dilator  500  gradually displace tissue as the inner dilator  400  or outer dilator  500  is advanced through tissue during the dilation procedure toward the target surface. 
     The outer dilator  500  may further include a serrated edge  508  located on the distal end of the outer dilator  500 . The serrated edge  508  provides a surface for rigid connection with bone or other target tissue along a target surface. By including serrated edge  508 , outer dilator  500  may be positioned relative to the bone or other target tissue with or without additionally securing the outer dilator  500  to the target surface prior to advancement of a retractor assembly  600  through the outer dilator  500 . 
     With reference to  FIG.  9   , the cross-section of tissue dilation system “D” shows, in combination, the trocar  100 , inner dilator  400 , outer dilator  500 , and handle portion  200 . As the inner dilator  400  is advanced over the trocar  100 , the inner dilator  400  is positionally maintained relative to the target surface by the trocar  100  with the inner surface of the inner dilator  400  slidably engaging with the outer surface  106 A of the trocar  100 . Likewise, as the outer dilator  500  is advanced over the inner dilator  400 , the outer dilator  500  is positionally maintained relative to the target surface by the inner dilator  400  with the inner surface of the outer dilator  500  slidably engaging with the outer surface  404 A of the inner dilator  400 . Once the outer dilator  500  is advanced and engaged with the target surface, both the inner dilator  400  and the trocar  100  may be removed from the tissue dilation system “D” to allow for placement of a pedicle screw at the target surface via the outer dilator  500 . 
     While a tissue dilation procedure has been described in terms of sequential placement of an inner dilator  400  and outer dilator  500  over a trocar  100  toward a target surface, it is contemplated that, depending on the circumstances of the dilation procedure, the trocar  100  may be combined with the inner dilator  400 , the inner dilator may be combined with the outer dilator  500 , or the trocar  100 , the inner dilator  400 , and the outer dilator  500  may all be combined prior to advancement through tissue toward a target surface during the dilation procedure. 
     Referring now to  FIG.  10   , the trocar  100  is shown in combination with the inner dilator  400 . During combination of the trocar  100  the inner dilator  400 , the inner dilator  400  is advanced over the trocar  100 , thereby displacing tissue as the inner dilator  400  is advanced toward a target surface. The inner dilator  400  may further be engaged at the receiving portion  402  with a surgical tool (not shown) during the dilation procedure. The inner dilator  400  includes a tubular member  404  with the bore  408  dimensioned to pass over the trocar  100 , and an outer surface  404 A dimensioned to slidably engage with inner surface of the outer dilator  500  (see  FIG.  7   ) therealong. The inner dilator  400  further includes a tapered surface  406  which is dimensioned to engage the distal region  116  of the trocar  100  (see  FIG.  11   ). 
     Referring now to  FIG.  11   , the distal region of the inner dilator  400  includes an inner dilator end  406 A dimensioned to abut a tapered surface flange  108 A of the trocar  100 . The inner dilator end  406 A is located at the proximal-most region of the inner dilator  400  and comes into contact with the tapered surface flange  108 A of the trocar  100  as the inner dilator  400  is advanced toward the target surface. Contact between the tapered surface flange  108 A and the inner dilator end  406 A limits distal advancement of the inner dilator  400  through tissue toward the target surface. It is contemplated that, in alternative embodiments, the tapered surface flange  108 A of the trocar  100  may be dimensioned so as to allow the inner dilator  400  to advance toward the target surface. Additionally, the inner dilator  400  may have an inner dilator end  406 A which is serrated for engaging with bone at a target surface. 
     Referring to  FIGS.  12 - 13   , the trocar  100  is shown in combination with the inner dilator  400  of  FIG.  10   . The bore  118  of the trocar  100 , as shown in  FIG.  13   , defines a lumen therethrough within the trocar  100 . 
     Referring to  FIG.  14   , the handle portion  200 , trocar  100  and inner dilator  400  are shown separated from the outer dilator  500 . In an embodiment of the present disclosure, after the outer dilator  500  is advanced toward the target surface and secured via serrated edge  508  to target tissue, the inner dilator  400  and trocar  100  may be removed from the tissue dilation system “D”, with the outer dilator  500  remaining connected to target tissue at the target surface. To remove the inner dilator and the trocar  100 , a clinician may grip the handle member  202  of the handle portion  200  and apply force proximally relative to the target surface to remove the trocar  100 . A step (not shown) is located at a distal end of the trocar  100  that engages the inner dilator  400  such that the trocar  100  and inner dilator  400  can be removed together. Alternatively, the clinician may apply pressure proximally to the flanges  502  of the outer dilator  500 , thereby maintaining pressure against the outer dilator  500  and preventing dislodgement of the outer dilator  500  from the target surface as the inner dilator  400  and trocar  100  are removed from the tissue dilation system “D”. 
     Referring to  FIGS.  15 - 18   , a retractor assembly  600  may be slidably inserted into the bore  518  of the outer dilator  500  to advance a screw “S” toward a target surface. The retractor assembly  600  includes a screw inserter assembly  604 , a knob  602 , a retractor collar  608 , a retractor  610 , and a screw “S”. 
     The knob  602  may include one or more flanges for a clinician to grip during the placement of a screw “S”. It is contemplated that the knob  602  may be replaced with a variety of alternative rotational force application mechanisms, designs of which will be apparent to one skilled in the art. The knob  602  is located in a proximal region  614  of the screw inserter assembly  604  and is dimensioned to receive handle portion  200  (see  FIG.  4   ) thereon. 
     The screw inserter assembly  604  may further include one or more openings  606  located along its surface. The openings  606  may be selectively located so as to promote engagement with varying surgical instruments (not shown) during the dilation and a screw “S” placement procedure. The screw inserter assembly  604  is dimensioned to be slidably assembled with the retractor collar  608  and the retractor  610 . The retractor collar  608  may further be dimensioned to enclose a proximal region of the retractor  610 , thereby preventing maintaining blades of the retractor  610  in a fixed position. 
     For a detailed description of a retractor assembly  600 , reference may be made to U.S. Pat. No. 8,246,538 entitled “Minimally Invasive Retractor with Separable Blades and Method of Use,” and U.S. Pat. No. 8,734,338 entitled “Minimally Invasive retractor and Methods of Use,” the entire disclosures of which are incorporated herein by reference. 
     Referring to  FIG.  15   , the retractor assembly  600  is shown in combination with an outer dilator  500  (see  FIG.  7   ). A retractor collar  608  is dimensioned to abut flange  502  for selective detachment of the retractor  610  from the retractor collar  608  as the retractor assembly  600  is advanced toward the target surface. It is contemplated that the retractor collar  608  may be dimensioned so as to be slidably inserted into the bore  518  of the outer dilator  500  while advancing the retractor assembly  600  toward the target surface. The retractor collar  608  further includes an inner surface  608 A and an outer surface  608 B, with the inner surface  608 A being dimensioned to receive a retractor  610  during assembly therein (see  FIG.  19   ). 
     Referring to  FIG.  16   , in use the retractor assembly  600  is advanced through a bore  518  of the outer dilator  500 , with the outer dilator  500  being fixed to a target surface. Prior to insertion, the clinician assembles screw “S” to the distal region of the screw inserter assembly  604 . During assembly, the clinician slides the retractor  610  over the screw “S” and the screw inserter assembly  604 , thereby advancing the retractor  610  toward the proximal region of the retractor assembly  600 . The clinician also attaches knob  602  to the retractor assembly  600 . In combination, the clinician may advance the retractor assembly  600  through the bore  518  of the outer dilator  500  advancing from the proximal region of the outer dilator  500  to the distal region of the outer dilator  500  toward a target surface. 
     Referring to  FIGS.  17 - 20   , the retractor assembly  600  is shown in combination with the outer dilator  500 . In a contemplated embodiment, upon assembly the retractor collar  608  secures the proximal portion of the retractor assembly  600  along a proximal region of the bore  518  of outer dilator  500 . Additionally, the screw “S” may be engaged by an engagement portion  618  of the screw inserter assembly  604  (see  FIG.  20   ), with both the screw inserter assembly  604  and screw “S” providing outward force to secure the retractor  610  at a distal region of the bore  518  of the outer dilator  500  therein. 
     Referring to  FIG.  19   , the retractor collar  608  includes a distal collar surface  608 F which, when combined with the retractor assembly  600  (see  FIG.  15   ) abuts flange  502  of the outer dilator  500 . As a clinician advances the retractor assembly  600  beyond a predetermined point, the clinician may dislodge the retractor  610  from the retractor collar  608 . Once dislodged, the retractor collar  608  may maintain position in the bore  518  of the outer dilator  500  to stabilize the retractor assembly  600  as the retractor assembly  600  is advanced toward the target surface. To remove the outer dilator  500  from the surgical site, the clinician may apply force proximal relative to the target surface to dislodge the outer dilator  500  from the target surface. 
     Referring to  FIG.  20   , engagement portion  618  may further include engagement tip  618 A dimensioned to engage screw head  616 A. As a result of the mating of the engagement tip  618 A with the screw head  616 A, rotation of the screw inserter assembly  604  rotates the screw “S” for insertion into or removal from target tissue (i.e., bone). After placing the screw “S” into target tissue, the clinician may apply sufficient force to screw inserter assembly  604  proximally or away from screw “S” to the screw inserter assembly  604 , thereby dislodging the screw inserter assembly  604  from the screw “S” and the retractor  610 . If the clinician determines it necessary to remove screw inserter assembly  604  while leaving retractor  610  in position, the surgeon may apply force as is necessary to dislodge the screw inserter assembly  604  from the retractor collar  608 , thereby maintaining the position of the retractor collar  608  and the retractor  610 , relative to screw “S”. 
     With continued reference to  FIG.  20   , a distal region  620  of the retractor  610  may be shaped so as to require force to dislodge the retractor  610  from the screw “S”. Upon removal of the screw inserter assembly  604 , the retractor  610  may contract around the screw head  616 A. It is contemplated that retractor  610  may be made of a pliable, biocompatible, and sterilizable material such as polypropylene, polyethylene, or polycarbonate. By including pliable, biocompatible, and sterilizable materials, the retractor  610  may be deformed at the distal retractor end  620  as the retractor  610  is slid over the screw head  616 A. 
     Referring to  FIG.  21   , the retractor collar  608  is illustrated, including an outer collar surface  608 B, an inner surface  608 A, a distal collar surface  608 F, and collar flanges  608 D. Upon insertion into the retractor  610 , the proximal region of retractor  610  may be pressed against the distal collar surface  608 F. The inner surface  608 A thereby prevents retractor  610  from separating along retractor seams (not shown) during the surgical dilation procedure. The collar flanges  608 D are dimensioned to be received by the proximal region of the retractor  610  prior to insertion into the tissue dilation system “D”. The collar flanges  608 D may include a tapered surface  608 E which facilitates assembly of the retractor  610  and the retractor collar  608  during the dilation procedure, as is necessary. 
     Referring to  FIGS.  22 - 25   , another embodiment of an outer dilator is illustrated as outer dilator  500 ′ and may include an outer tubular member  504 ′, an inner tubular member surface  512 ′, flange  502 ′, and a tapered surface  506 ′. The flanges  502 ′ may further include an openings  514  dimensioned to receive a temporary fixation pin  700  (see  FIGS.  26 A,  26 B ). The outer dilator  500 ′ may further include one or more cavities  516  located along the outer tubular member  504 ′, each cavity  516  dimensioned to receive at least a portion of temporary fixation pin  700  therealong. Additionally, protrusion  522  may be located along the outer tubular member  504 ′ and may partially or fully enclose each cavity  516 , thereby preventing the temporary fixation pin  700  from moving laterally relative to outer dilator  500 ′ while guiding longitudinal movement of the temporary fixation pin  700 . 
     Referring to  FIGS.  26 A- 26 B , the temporary fixation pin  700  may include a recess  702 , a proximal region  704 , a tubular member  706 , threads  708 , and a tip  710 . The recess  702  may be located in a proximal region of the temporary fixation pin  700 . The recess  702 , as illustrated in  FIG.  26 B  has a hexalobular shape, which permits engagement with a surgical tool, providing increased grip for application of rotational force to temporary fixation pin  700 . It will be apparent to one skilled in the art that recess  702  may be shaped in a variety of different ways which permit precise transfer of rotational force from a surgical instrument (not shown) while reducing the chance of stripping the recess  702  during installation and removal. 
     With continued reference to  FIG.  26 A , a tubular member  706  traverses the longitudinal axis A-A, connecting a proximal region  704  to threads  708  and a temporary fixation pin tip  710 . 
     Referring to  FIG.  27   , another embodiment of an outer dilator is illustrated as outer dilator  500 ″ and may include an outer tubular member  504 ″, an inner tubular member surface  512 ″, flange  502 ″, and a tapered surface  506 ″. The flanges  502 ″ further include openings  514 ″ dimensioned to receive a temporary fixation pin  700  (see  FIGS.  26 A,  26 B ) therethrough. The temporary fixation pin  700  of  FIGS.  26 A- 26 B  is combined with outer dilator  500 ″. During installation, the tip  710  may be advanced through the proximal region of outer dilator  500 ′ through opening  514 ″ located on flange  502 ″. The temporary fixation pin  700  may subsequently be advanced along longitudinal axis A-A to be engaged with the target surface. After assembly, the temporary fixation pin  700  may maintain force against flange  502 ″, thereby providing additional force against outer dilator  500 ″, fixing outer dilator  500 ″ to target tissue. 
     It is contemplated that a kit may be provided including the tissue dilation system “D” as disclosed herein. Additionally, a kit may include the retractor system  600  as described herein, either combined with the tissue dilation system “D” or as a stand-alone kit. In alternative kits, outer dilator  500 ′ and/or outer dilator  500 ″ may be included separately, or in combination with one or more temporary fixation pins  700 , inner dilator  400 , trocar  100 , and/or handle portion  200 . It is also contemplated that temporary fixation pins  700  may be included in a separate kit. Additional tools which may be useful for a clinician during the dilation procedure may be included in the described kits. The kits described in the present disclosure may be provided with sterile packaging to facilitate opening and immediate use in a sterile environment such as an operating room. 
     Any of the components presently disclosed may be formed of any suitable biocompatible material which is of sufficient strength to receive both the longitudinal and rotational forces necessary for the procedures described. It is contemplated that the disclosed devices may be made of materials including, but not limited to, titanium, titanium alloys, stainless steel, cobalt chrome, and nickel titanium or polymer compositions. 
     Persons skilled in the art will understand that the structures and methods specifically described herein and shown in the accompanying figures are non-limiting exemplary embodiments, and that the description, disclosure, and figures should be construed merely as exemplary of particular embodiments. It is to be further understood that the present disclosure is not limited to the precise embodiments described, and that various other changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the disclosure. Additionally, the elements and features shown or described in connection with certain embodiments may be combined with the elements and features of certain other embodiments without departing from the scope of the present disclosure, and that such modifications and variations are also included within the scope of the present disclosure, and that such modifications and variations are also included within the scope of the present disclosure. Accordingly, the subject matter of the present disclosure is not limited to what has been particularly shown and described.