Patent Publication Number: US-2007100366-A1

Title: Minimally invasive tissue expander systems and methods

Description:
BACKGROUND  
      In minimally invasive surgical procedures providing access to the surgical site is a balancing act between minimizing the size of the incision and providing enough room for the surgeon to manipulate the instruments to perform the surgery. Access devices, including expandable tubular retractors and ports are used to retract the skin, muscles and tissue from the surface of the skin to the surgical site providing an unobstructed pathway for the surgeon to work. Typically, a sequential dilation technique is used to insert an access device. To minimize the damage to the tissue and muscles in creating a pathway, a small incision is made in the skin and a guide wire is inserted. Next a small diameter tubular member is advanced over the guide wire until it reaches the desired surgical site. As the tube is advanced it pushes the skin and tissue out of the way creating the surgical path. A second tubular member having a slightly larger diameter is then advanced over the first tubular member creating a wider path. These steps are repeated using tubular members of increasing diameter until the desired size of the path is created. Finally, an access device is advanced over the largest tubular member and the tubular members are removed leaving the access device in place. Using this technique minimizes trauma to the tissue as the tissue is expanded or stretched rather than cut as in an open procedure.  
      Some drawbacks with the dilator system include the number of steps it takes to create the desired size for the access device, and difficulty in inserting and removing the tubular members.  
     SUMMARY  
      Disclosed herein are tissue expander systems and methods of use. In one embodiment a tissue expander system may include a first paddle having a connecting feature and a second paddle having a connecting feature adapted to connect to the connecting feature of the first paddle forming an assembly of the first and second paddles. The system may further include an outer sleeve adapted to slide over the first and second paddles. The outer sleeve may also have slots to receive the first and second paddles. The system may also include a handle for insertion and/or removal of the paddles.  
      In an alternate embodiment the tissue expander system may include first and second paddles having mating channels for connecting the paddles. The system may also include an outer sleeve with slots for receiving the paddles. In yet another embodiment, the tissue expander system may include first and second paddles and an access device for creating a pathway to the surgical site.  
      The surgeon when using the tissue expander system inserts a first paddle through an incision into proximity with the vertebral body; inserts a second paddle through the incision; connects the second paddle to the first paddle; inserts an outer sleeve over the first and second paddles into proximity with the vertebral body; and places an access device over the outer sleeve.  
      In an alternate use, the surgeon may insert a paddle through an incision to a point proximate the vertebral body; rotate the paddle within the incision; and insert an access device over the paddle to create a pathway to the vertebral body. The surgeon may choose to add an outer sleeve over the paddle prior to placing the access device.  
      In yet another alternate method of creating a minimally invasive pathway to a vertebral body, the surgeon may insert a paddle through an incision to a point proximate the vertebral body; insert a second paddle within the incision in connection with the first paddle; and insert an access device over the first and second paddles to create a pathway to the vertebral body.  
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
      These and other features and advantages of the tissue expander system 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 tissue expander system and methods disclosed herein and, although not to scale, show relative dimensions.  
       FIG. 1A  illustrates a perspective view of the first paddle of the tissue expander system.  
       FIG. 1B  illustrates a side view of the first paddle shown in  FIG. 1A .  
       FIG. 1C  illustrates an end view of the first paddle shown in  FIG. 1A .  
       FIG. 2A  illustrates a perspective view of the second paddle of the tissue expander system.  
       FIG. 2B  illustrates a side view of the second paddle shown in  FIG. 2A .  
       FIG. 2C  illustrates an end view of the second paddle shown in  FIG. 2A .  
       FIG. 3A  illustrates a perspective view of the outer sleeve of the tissue expander system.  
       FIG. 3B  illustrates a side view of the outer sleeve shown in  FIG. 3A .  
       FIG. 3C  illustrates an end view of the outer sleeve shown in  FIG. 3A .  
       FIG. 4A  illustrates a perspective view of the paddle insertion handle for the tissue expander system.  
       FIG. 4B  illustrates a side view of the paddle insertion handle shown in  FIG. 4A .  
       FIG. 5  illustrates a view of the assembly of the first and second paddles shown in  FIGS. 1 and 2 .  
       FIG. 6A  illustrates a perspective view of the assembly of the second paddle, first paddle and the outer sleeve.  
       FIG. 6B  illustrates a perspective view of the assembly shown in  FIG. 6A .  
       FIG. 6C  illustrates an end view of the assembly shown in  FIG. 6A .  
       FIG. 6D  illustrates the assembly of the first and second paddle with an access device.  
       FIG. 7  illustrates a cross-section of an assembly of a first paddle, a second paddle and an outer sleeve having docking features.  
      FIGS.  8 A-D illustrate another embodiment of a tissue expander system.  
      FIGS.  9 A-C illustrate another embodiment of an elliptically shaped tissue expander system.  
      FIGS.  10 A-D illustrate another embodiment of a tissue expander system having only one paddle. 
    
    
     DETAIL DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the tissue expander system and methods 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 tissue expander system and methods 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 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. 1-10  illustrate various components of an exemplary embodiment of a tissue expander system. The system may be used for numerous surgical procedures but will be described below in relation to spinal surgery. One skilled in the art will understand that the system can also be used for other surgical procedures including orthopedic. The system may be used with any number of surgical approaches used in spinal surgery including anterior, posterior, anterior/lateral, lateral, and posterior/lateral.  
      The exemplary tissue expander assembly  100  shown in  FIG. 6A  includes a first paddle  10 , a second paddle  30  and an outer sleeve  50 . The exemplary assembly  100  may be employed to expand skin, tissue, and muscle through a minimally invasive incision to create a pathway to a surgical site, i.e., a vertebral body. For example, the first paddle  10  is inserted through a skin incision and advanced proximate to the vertebral body. The first paddle  10  maybe rotated 90 degrees to expand or stretch the surrounding tissue, muscle and skin. The second paddle  30  is then inserted in connection with the first paddle  10  to form an assembly within the incision as shown in  FIG. 5 . The orientation of the paddles with respect to each other may be varied such that the angle between the first paddle  10  and the second paddle  30  may be acute (&lt;90 degrees), obtuse (&gt;90 degrees) or right (=to 90 degrees). Depending on the shape of the first and second paddles other various-shaped assemblies could also be constructed. The outer sleeve  50  is advanced over the assembly forming a circular or ellipsoidal shaped assembly and creating a pathway to the surgical site. An access device  200 , such as a port or expandable retractor, may be advanced over the assembly to maintain the pathway during the surgical procedure. The tissue expander assembly  100  may be removed in one step, i.e., the first paddle  10 , the second paddle  30  and the outer sleeve  50  may be removed simultaneously. The assembly  100 , when employed in the exemplary manner, thus may be used to expand or dilate tissue, muscle or skin to create a pathway to the surgical site.  
      The first paddle  10  of the exemplary assembly  100  illustrated in  FIGS. 1A and 1B  extends from a distal end  18  to a proximal end  20 , along a longitudinal axis and has a connecting feature  22  adapted to connect the first paddle  10  to the second paddle  30 . The connecting feature  22  may be in the form of a tongue and groove, complementary mating shapes, a channel or other structures suitable for connecting the first paddle  10  to the second paddle  30 . In the exemplary embodiment, the first paddle  10  is generally rectangular in shape having radiused edges  28  as seen in  FIG. 1C . One skilled in the art will appreciate that the first paddle  10  may have other cross sectional shapes including, for example, v-shaped or elliptical. The distal end  18  of the first paddle  10  may be tapered for ease of insertion. The distal end  18  may also have features  12  to aid in docking to bone at the surgical site such as serrated edges, teeth, or roughened surface area. An example of a distal end  18  of a first paddle  10  having teeth  12  is shown in  FIG. 7 .  
      In the exemplary embodiment illustrated in  FIGS. 1A and 1B , the connecting feature  22  of the first paddle  10  is a channel extending distally from the proximal end  20 . The first paddle  10  has a length l cfp , width w fp  and thickness t fp . The length l fp  is such that the proximal end  20  of the first paddle  10  will extend above the skin incision. The channel  22  may extend over a portion of the first paddle  10  to a length l cfp  such that the percentage of l cfp  to l fp  is between 5% and 95%. The width w fp  of the first paddle  10  may be substantially constant between the proximal  20  and distal end  18  portions and may narrow near the proximal end  20  creating shoulders  24   a,b.  The narrow portion  26  of the first paddle  10  extending past the shoulders  24   a,b  may be used as a handle or to support a handle  80  for insertion or removal. The channel  22  is sized to receive a connecting feature  32  of the second paddle  30 . The width of the channel  22  may be between 5% and 95% of the width of the first paddle  10 . The width of the first paddle  10  may correlate to the desired size of the access device  200  to be used for the surgery.  
      The exemplary embodiment of the second paddle  30  illustrated in FIGS.  2 A-C has a distal end  38 , a proximal end  40  and a connecting feature  32  adapted to connect with the connecting feature  22  of the first paddle  10  to connect the two paddles. The connecting feature  32  is exemplified as a channel extending along a portion of the second paddle  30  from the distal end  38 . The distal end  38  of the second paddle  30  may be tapered for ease of insertion. The distal end  38  may also have the same feature  12  for docking to the bone at the surgical site as the first paddle  10 . The second paddle  30  has an overall length l sp  from the proximal end  40  to the distal end  38 . The channel  32  has a length l csp  extending from the distal end  38  between 5% and 95% of l sp  the length of the second paddle  30 . The second paddle  30  has a width w sp , which may be equal to the width of the first paddle  10 . The width w sp  of the second paddle  30  may be substantially constant between the proximal end  40  and distal end  38  and may narrow near the proximal end  40  creating shoulders  34   a,b.  The narrow portion  36  of the second paddle  30  extending past the shoulders  34   a,b  may be used as a handle or to support a handle  80  for insertion or removal. The narrow portion  36  may be a solid shaft extending proximally from the shoulders or may have a channel  42  extending distally from the proximal end  40  for receiving a handle as illustrated in  FIG. 2A .  
      The thickness of the second paddle  30  may be sized to be received within the channel  22  of the first paddle  10  creating a friction fit between the second paddle  30  and the first paddle  10 . Alternately, the connecting feature  22  of the first paddle  10  and the connecting feature of the second paddle  30  may have interlocking features such as tongue and groove, ball plunger and detent, or pin and slot. The connecting features  22 ,  32  may have different complementary configurations to engage each other. The connecting features  22 , 32  may also be angled with respect to each other to alter the paddle assembly shape such that the angles between the first paddle  10  and the second paddle  30  may be acute (&lt;90 degrees), obtuse (&gt;90 degrees) or right (=90 degrees).  
      The first paddle  10  is inserted through a minimally invasive incision such that the width of the paddle w fp  is parallel to the longitudinal axis of the incision. Once the first paddle  10  is inserted to the desired depth it may be rotated approximately 90 degrees to further separate the tissue and muscle fibers leading to the surgical site proximate a vertebral body. The second paddle  30  is placed through the incision such that the connecting feature  32  of the second paddle  30  is aligned with the connecting feature  22  of the first paddle  10 . The second paddle  30  is advanced along the channel  22  until the distal portion  38  of the second paddle  30  reaches the surgical site proximate the vertebral body. As the second paddle  30  is inserted it expands the tissue and muscles within the pathway to the surgical site proximate the vertebral body. As shown in  FIG. 5  the connected first paddle  10  and the second paddle  30  are at right angles to each other forming a +-shape assembly.  
      The outer sleeve  50  of the tissue expander assembly  100  shown in  FIGS. 3A and 3B  has a generally tubular shape with a central lumen  52  extending from a distal  58  end to a proximal  60  end. The outer sleeve  50  is sized to slide over the assembly of the first  10  and second  30  paddles. Extending proximally from the distal end  58  along the longitudinal axis of the outer sleeve  50  are slots  54   a,b,c,d.  As illustrated in  FIG. 6B , each slot  54  is sized to receive a portion of the second paddle  30  or first paddle  10 . The length of each slot  54  is adapted to accommodate the shoulders  24   a,b  and  34   a,b  formed on the first  10  and second  30  paddles. The distal end  58  of the outer sleeve  50  may be tapered to ease insertion. The length of the outer sleeve  50  is less than the overall length of the first  10  and second  30  paddles, such that the proximal ends  20 ,  40  of the first paddle  10  and second paddle  30  extend through the lumen of the outer sleeve  50 . The outer sleeve  50  may have a generally circular or ellipsoidal shape depending on the shape of the access device  200  to be used. As shown in  FIG. 3C , the inner diameter d i  of the lumen  52  of the outer sleeve  50  is smaller than the width w fp  of the first paddle  10  and the width w sp  of the second paddle  30  such that the narrow portion  26 ,  36  of the first  10  and second  30  paddles fits within the lumen  52  of the outer sleeve  50 . The outer diameter d 0  of the outer sleeve  50  is the same as or greater than the width w fp  of the first paddle  10  and the width w sp  of the second paddle  30 . The slots  54   a,b,c,d  of the outer sleeve  50  are sized to accommodate the width of the first and second paddles such that when the outer sleeve  50  is placed over the paddles the circumference of the outer sleeve is completed by the assembly.  
      The outer sleeve  50  is advanced through the incision over the first  10  and second  30  paddles. The slots  54   a,b,c,d  slide over the widest portion of the first  10  and second  30  paddles until the shoulders  24   a,b  and  34   a,b  abut the proximal end of the slots  54 , as shown in  FIG. 6A . The first  10  and second  30  paddles fill the slots  54   a,b,c,d  of the outer sleeve  50  creating a tissue expander assembly  100  that retracts tissue and muscles along the pathway to the surgical site.  FIG. 6C  illustrates the completed circumference of the outer sleeve  50  with an end view from the bottom of the assembly  100 . The access device  200 , shown in  FIG. 6B  may be placed over the tissue expander assembly  100  to create the pathway to the surgical site. The tissue expander assembly  100  may be removed in one step by grabbing the first paddle  10  by the proximal end  20 , leaving the access device  200  in place. Alternately, as shown in  FIG. 6D , the outer sleeve  50  may not be used and the access device  200  may be placed directly over the assembly of the first paddle  10  and the second paddle  30 .  
      In an alternate method, a guide wire can be inserted at the desired surgical site location. The first paddle may be cannulated (not shown) and inserted over the guide wire. After the first paddle is inserted, the guide wire is removed and the second paddle inserted as described in the method above.  
      The first paddle  10 , the second paddle  30 , and the outer sleeve  50  may be provided in varying sizes (diameters and lengths) correlating to the size of the access port  200  to be used. The paddles may range in diameter size from 10 mm to 35 mm, preferably from 13 mm to 26 mm. The second paddle  30  may also have depth markings for measuring the depth at the skin incision for assistance in determining the length of the access device  200  to be used. The paddles  10 ,  30  and outer sleeve  50  may be manufactured from any biocompatible material such as metal, plastic, or composite and may be radiopaque or radiolucent. If radiolucent, the paddles and or outer sleeve may also include depth markers made from radiopaque rings for intra-operative depth measurements under fluoroscopy. Alternately, the distal ends of the paddles and sleeve may be radiopaque to aid the surgeon under fluoroscopy.  
      An insertion handle  80  shown in  FIG. 4A  may be used to insert the first  10  and second  30  paddles. The handle  80  has a generally cylindrical configuration having a distal portion  88  and a proximal portion  90 . A first channel  82  extends through the handle  80  from the distal portion  88  towards the proximal portion  90 . Within the channel  82  are connecting features  94  to connect the handle  80  to the first paddle  10 . The connecting features  94  may include friction fit, ball plungers, spring loaded pins, grooves and detents. Alignment features  92  may be placed within the channel  82  to aid with alignment of the proximal end  20  of the paddle  10  during connection to the handle  80 . The handle  80  may be connected to the first paddle  10  prior to insertion within the skin incision. After the first paddle  10  is inserted the handle  80  may then be removed from first paddle  10  and connected to the second paddle  30  for insertion. In an alternate embodiment the handle  80  may have multiple intersecting channels for connecting to both the first paddle  10  and the second paddle  30  simultaneously. The multiple channels allow the handle  80  to connect to both first  10  and second  30  paddles at the same time providing for easier insertion of the second paddle and/or removal of the entire assembly  100  in one step.  
      An alternate embodiment of a tissue expander system  100 ′ may have a generally elliptical shape to accommodate an elliptical access device such as a port or expandable retractor as illustrated in FIGS.  9 A-C. The elliptical shaped tissue expander system  100 ′ includes a first paddle  10 ′, a second paddle  30 ′ and an outer sleeve  50 ′ similar to the system  100  described above. In this embodiment the second paddle  30 ′ may have a width w p2  greater than the width of the first paddle w p1    10 ′ to create a t-shaped assembly. Alternately, the first paddle  10 ′ may have a width w p1  greater than the width of the second paddle w p2    30 ′. The outer sleeve  50 ′ has a generally elliptical shape. Slots  54 ′ are configured to slide over the paddle assembly. The paddles are inserted as above and the outer sleeve  50 ′ is advanced over the paddle assembly. An elliptical shaped access device, such as a port or expandable retractor, not shown, is placed over the system  100 ′.  
      Another embodiment of a tissue expander system is illustrated in FIGS.  8 A-D. The system  500  has components similar to the first system  100  including a first paddle  510 , a second paddle  530 , and an outer sleeve  550 . In this embodiment the first paddle  510  and second paddle  530  have different shapes and connecting features from the first embodiment while the outer sleeve  550  remains substantially the same. The first paddle  510  has a distal end  518 , a proximal end  520 , and a connecting feature  522  adapted to connect the first paddle  510  to the second paddle  530 . The first paddle  510  extends along a longitudinal axis between the proximal end  520  and the distal end  518 . In the exemplary embodiment, the first paddle  510  is generally v-shaped and has radiused edges as seen in  FIG. 8A . The distal end  518  of the first paddle  510  may be tapered for ease of insertion. The distal end  518  may also have features to aid in docking to bone at the surgical site such as serrated edges, teeth, or roughened surface area.  
      The first paddle  510  has a length l fp , such that the proximal end  520  of the first paddle  510  will extend above the skin incision. The connecting feature  522  may extend over the entire length of the paddle or only a portion of the first paddle  510 . A shaft or handle (not shown) may extend from the proximal end  520  of the first paddle  510  for inserting and removing the paddle. The connecting feature  522  is adapted to connect with a complementary shaped connecting feature on the second paddle  530 . As shown in  FIG. 8A  the connecting feature  522  is in the form of a rounded projection.  
      The second paddle  530  illustrated in  FIG. 8B  has a distal end  538 , a proximal end  540  and a complementary connecting feature  532 , in this embodiment shown as a rounded channel. The second paddle  530  has a generally rectangular shape and has radiused edges. The distal end  538  of the second paddle  530  may be tapered for ease of insertion. The distal end  538  may also have the same feature for docking to the bone at the surgical site as the first paddle  510 . The second paddle  530  has an overall length l sp  from the proximal end  540  to the distal end  538 . The width of the second paddle  530  may correlate to the radius of the desired size of the access device to be used for the surgery. A shaft or handle (not shown) may extend from the proximal end of the second paddle  530  for use during insertion or removal of the paddle. The connecting feature  532  of the second paddle  530  as shown in  FIG. 8B  is a rounded channel complementary to the shape of the rounded projection  522  on the first paddle  510 . Other complementary connecting features may include a dovetail, ball plunger, pin and slot, or detent. The connecting features  522 , 532  may also be angled with respect to each other to alter the paddle assembly shape, for example the paddles may be angled at acute, obtuse or right angles to each other.  
      The first paddle  510  is inserted through a minimally invasive incision. Once the first paddle  510  is inserted to the desired depth it may be rotated to further separate the tissue and muscle fibers leading to the surgical site. The second paddle  530  is inserted into the incision such that the connecting feature  532  connects with the connecting feature  522  of the first paddle  510 . When the first paddle  510  has a v-shape and the second paddle  530  has a rectangular shape, the assembly of the two paddles when viewed from the top or bottom resembles a Y-shaped assembly.  FIG. 8D  illustrates an end view of the assembly of the first  510  and second  530  paddles along with the outer sleeve  550 .  
      The outer sleeve  550  has substantially the same configuration as the outer sleeve  50  in the first embodiment. The outer sleeve  550  has slots  554   a,b,c  positioned to accommodate the shapes of the first  510  and second  530  paddles. As shown in  FIG. 8C , the outer sleeve  550  slides over the assembly of the first  510  and second  530  paddles to complete the circumference of the desired shape corresponding to the shape of the access device to be inserted. The access device  200  (not shown) is then advanced over the outer sleeve  550 . The entire assembly  500  including the first  510  and second  530  paddles and outer sleeve  550  may be removed simultaneously in one step leaving the access device  200  in the desired location.  
      An alternate embodiment of the tissue expander system, illustrated in FIGS.  10 A-D includes a first paddle  610 . The paddle  610  extends from a proximal end  620  to a distal end  618  and has a generally rectangular shape with radiused edges. The distal end  618  may taper for ease of insertion. The paddle  610  has a width w p  at its widest point and a width w np  at its narrowest point. Shoulders  624   a,b  are formed where the paddle  610  changes width. The system also includes an outer sleeve  650  having a generally tubular shape with a central lumen  652  extending from a proximal end  660  to a distal end  658 . The outer sleeve  650  has slots  654   a,b  extending proximally from the distal end  658 . The central lumen  652  is sized to accommodate the narrow width portion  626  of the paddle  610  while the slots  654   a,b  are sized to receive the widest portion of the paddle  610 . The length of each slot  654   a,b  is adapted to accommodate the shoulders  624   a,b  of the paddle  610 . The outer diameter of the outer sleeve  650  may be the same as the inner diameter of the access device  200  to be used for the procedure.  
      The paddle  610  is inserted through a minimally invasive incision such that the width is parallel to the incision to the desired depth proximate a vertebral body. The paddle  610  is rotated approximately 90 degrees to stretch the tissue and muscle in all directions. The outer sleeve  650  may be inserted through the incision over the paddle  610  aligning the slots  654   a,b  with the shoulders  624   a,b  of the paddle  610 . The outer sleeve  650  is advanced until it is proximate the vertebral body. The access device  200  may then be advanced over the assembly of the paddle  610  and the outer sleeve  650 .  FIG. 10C  illustrates the assembly with the access device  200  in place. The paddle  610  and outer sleeve  650  may be removed simultaneously in one step by pulling on the proximal end  620  of the paddle. Alternately, the surgeon may choose to skip the outer sleeve and directly insert the access device  200  over the paddle  610  as shown in  FIG. 10D .  
      While the tissue expander systems 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.