Abstract:
The present invention is directed to a device that is implanted between the spinous processes of adjacent vertebrae of the spine and used for relieving pain associated with the vertebrae and surrounding tissues and structures by maintaining and/or adding distraction between adjacent vertebrae. The present invention includes a tissue expander adapted to move from a first insertion position, for ease of implantation between spinous processes, to a second retention position that prevents displacement of the implant.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This U.S. patent application is a continuation of and claims priority from U.S. application Ser. No. 11/003,555, filed on Dec. 3, 2004, which claims the benefit of under 35 U.S.C. § 109(e) of U.S. Provisional Patent Application No. 60/565,910, as filed on Apr. 28, 2004, the disclosures of which are incorporated herein by reference. 
     
    
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     NOT APPLICABLE  
       REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK  
       [0003]     NOT APPLICABLE  
       BACKGROUND OF THE INVENTION  
       [0004]     This invention relates to an interspinous process implant and method for implantation.  
         [0005]     The spinal column is a biomechanical structure composed primarily of ligaments, muscles, vertebrae and intervertebral disks. The biomechanical functions of the spine include: 1) support of the body, which involves the transfer of the weight and the bending movements of the head, trunk and arms to the pelvis and legs; (2) complex physiological motion between these parts; and (3) protection of the spinal cord and nerve roots.  
         [0006]     As the present society ages, it is anticipated that there will be an increase in adverse spinal conditions which are characteristic of older people. By way of example, with aging comes an increase in spinal stenosis (including, but not limited to, central canal and lateral stenosis), and facet anthropathy. Spinal stenosis typically results from the thickening of the bones that make up the spinal column and is characterized by a reduction in the available space for the passage of blood vessels and nerves.  
         [0007]     Pain associated with such stenosis can be relieved by medication and/or surgery. It is desirable to eliminate the need for major surgery for all individuals, and in particular, for the elderly.  
         [0008]     Accordingly, a need exists to develop spine implants that alleviate pain caused by spinal stenosis and other such conditions caused by damage to, or degeneration of, the spine. Such implants would distract, or increase the space between, the vertebrae to increase the foramina  1  area and reduce pressure on the nerves and blood vessels of the spine.  
         [0009]     Further, a need exists for an implant that minimizes further trauma to the spine, and obviates the need for invasive methods of surgical implantation. Additionally, a need exists to address adverse spinal conditions that are exacerbated by spinal extension.  
       BRIEF SUMMARY OF THE INVENTION 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  depicts a side view of an embodiment of the implant of the invention, in a first insertion position.  
         [0011]      FIG. 2  is a top-down view of the embodiment of the implant of the invention depicted in  FIG. 1  in the first insertion position.  
         [0012]      FIG. 3  is a side view of the embodiment of the implant of the invention depicted in  FIG. 1  in a second retention position.  
         [0013]      FIG. 4  illustrates a top-down view of an embodiment of the implant of the invention, the implant positioned under a spinous process of the spine with the tissue expander in the second retention position.  
         [0014]      FIG. 5  depicts a side view of an alternative embodiment of the implant of the invention in a first insertion position.  
         [0015]      FIG. 6  depicts a side view of the alternative embodiment of the implant of the invention illustrated in  FIG. 5 , in a second retention position.  
         [0016]      FIG. 7  depicts a top view of yet another embodiment of the implant of the invention, in a first insertion position.  
         [0017]      FIG. 8  depicts a side view of the embodiment shown in  FIG. 9  of the implant of the invention, in a second retention position.  
         [0018]      FIG. 9  depicts a top view of the embodiment of  FIG. 7  in a deployed position between spinous processes.  
         [0019]      FIG. 10  depicts a flow diagram of a method of insertion of an implant of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     Embodiments of the present invention relate to an interspinous process implant including a first wing for implant retention after placement, a spacer for maintaining and/or causing additional distraction, and a tissue expander for converting from a first position for insertion to a second position for retention of the implant after placement between adjacent spinous processes. In the second position, the tissue expander acts like a second wing to prevent displacement of the implant. The disclosed invention further claims a method for lateral insertion of the disclosed implant of the invention.  
         [0021]      FIG. 1  shows a side view of an embodiment of an implant  100  of the disclosed invention. The implant  100  comprises a spacer  16  that maintains the distraction of the spinous processes of adjacent vertebrae, once the spacer  16  is positioned between the spinous processes  12 ,  14 . The spacer  16  can have various shapes including, by way of example only, a cylindrical shape, an elliptical shape, or tear-drop shape when viewed in cross-section substantially perpendicular to a longitudinal or elongated axis  34  of the spacer  16 . The longitudinal axis  34  is oriented from the left lateral to right lateral spine, when the implant  100  is positioned in the spine.  
         [0022]     The spacer  16  has a first or proximal end  18  and a second or distal end  20 . At the first end  18 , the spacer  16  is connected with a first wing  22 . The first wing  22  functions as a first retaining unit. That is, the first wing  22  prevents displacement of the implant  100  once the implant  100  is positioned in the spine, with the spacer  16  between adjacent spinous processes. From the first wing  22  extends a shaft  17  upon which the rotatable spacer  16  is rotatably mounted, so that the spacer  16  can rotate independently from the first wing  22  for positioning of both elements of the implant  100 . Alternatively, the first wing  22  can be fixedly connected with, or integral to the spacer  16 .  
         [0023]     The second end  20  of the spacer  16  is located adjacent to a tissue expander  24 . The tissue expander  24  has a wedge-shaped first end  26  that is distal to the spacer  16 , and a second end  28  that is adjacent the spacer  16 . As discussed below, the tissue expander  24  can be rotated about the axis  34 . When the tissue expander  24  is rotated about the rotation axis  34 , it is converted from a first insertion position  36  (shown in  FIGS. 1 and 2 ) to a second retention position  42  (shown in  FIGS. 3 and 4 ).  
         [0024]     In  FIGS. 1 and 2 , the tissue expander  24  is in the first insertion position  36 , where  FIG. 1  is a side view of an embodiment of the implant of the invention, and  FIG. 2  is a top-down view of an embodiment of the implant  100  of the invention, in the same first insertion position  36  as the implant  100  depicted in  FIG. 1 . The first end  26  of the tissue expander  24  is wedge-shaped in the direction of insertion, where the implant  100  is inserted laterally. That is, where the implant  100  is to be inserted laterally, the wedge-shaped first end  26  is narrowest at the point of insertion and broadens along the length of the tissue expander  24  toward the second end  28  of the tissue expander  24  that is located adjacent to the second end  20  of the spacer  16 . The wedge shape of the tissue expander  24  facilitates insertion of the implant  100  by initiating distraction, if no other method is used during implantation, or by adding to or maintaining distraction created by another source, if any other such source is employed.  
         [0025]      FIG. 2  shows a top-down view of the implant  100 , with the tissue expander  24  in the first insertion position  36 . The elongated base element  32  of the tissue expander  24  in the first insertion position  36 , where insertion is from a lateral direction, is oriented in an anterior-posterior direction relative to a patient. In contrast, as discussed in greater detail below, the elongated base element  32  of the tissue expander  24  in the second retention position  42  is oriented substantially perpendicular to the first insertion position  36 , in a direction that is substantially perpendicular to the anterior-posterior direction relative to the patient. In this embodiment, the elongated base element  32  in the first insertion position  36  can further be described as substantially perpendicular to the orientation of the first wing  22 , the first wing  22  being at about a 90″ angle from the anterior-posterior direction relative to the patient, substantially parallel to the axial plane of the patient.  
         [0026]      FIG. 3  depicts a side view of the implant  100  with the tissue expander  24  rotated to the second retention position  42 . The tissue expander  24  in the second retention position  42  can prevent displacement of the implant  100  after insertion in the spine of a patient. The tissue expander  24 , including the wedge-shaped first end  26 , and the elongated element  32 , can rotate from the first insertion position  36  ( FIG. 1 ) adapted to facilitate insertion, to the second retention position  42  ( FIG. 3 ) after insertion and positioning of the implant  100 .  
         [0027]     In one embodiment, the tissue expander  24  rotates about 90″ to be reconfigured into the second retention position  42 , which alters the orientation of the wedge-shaped first end  26  of the tissue expander  24  and the elongated base element  32 . In the second retention position  42 , the tissue expander  24  is rotated about 90″ so that the elongated element  32  ( FIG. 3 ) is substantially perpendicular to the anterior-to-posterior direction of a patient. In other words, instead of being oriented with the axis  38  of the elongated element  32  from anterior to posterior (FIGS.  1  (side view) and  2  (top-down view)), the elongated base element  32  is rotated about the elongated axis  34  of the spacer  16 , so that the elongated base element  32  is oriented generally parallel to the first wing  22  ( FIG. 3 ). It will be understood by those of ordinary slull in the art that the shift need not be 90″ and could be by way of example of 45″ or 60″.  
         [0028]      FIG. 4  depicts the embodiment of the implant  100 , positioned between adjacent spinous processes, upon initial insertion and in the configuration of  FIGS. 1 and 2 .  
         [0029]     The tissue expander  24  can be locked into the second retention position  42 , as depicted in  FIGS. 1-3 . In this embodiment, the shaft  17  has a bore  46  extending completely therethrough, which bore  46  has the same longitudinal axis  34  as does shaft  17 . Positioned in bore  46  is a shaft  48  which can rotate in bore  46 , and which is connected to tissue expander  24 . Shaft  48  includes a head  50  which has a slot  52  that can accept a rotation tool, such as a screwdriver. Rotation of the shaft  48  causes the tissue expander  24  to rotate. Thus once the implant  100  is positioned between spinous processes, a screwdriver can be used to rotate the tissue expander  24  from the insertion position as seen in  FIGS. 1 , and  2  to the retention position shown in  FIG. 3 . In a preferred embodiment the shaft  48  can rotate the tissue expander  24  about 90″. Alternatively, different amounts of rotation can be accomplished. Although the patient&#39;s tissue will hold the tissue expander  24  in the rotated position, if desired, a mechanism can be included to fix the shaft  48  in the rotated position. Such mechanism can include a detent extending from head  50  which can lock into a recess in the first wing  22  as the shaft  48  is rotated. Another mechanism can include ridges extending from the head  50  of the shaft  48  which can lock into recesses in the first wing  22 . One of ordinary skill in the art can appreciate that other lock-and-key mechanisms, or other mechanism that allows rotation and locking into the desired second retention position  42 , can also be employed to secure the second retention position  42  for implant  100 .  
         [0030]      FIGS. 5 and 6  depict an alternative embodiment of the implant  200  of the disclosed invention. In this embodiment, both the first wing  222  and the tissue expander  224 , are secured to shaft  248  and can rotate together, from a first insertion position  236  ( FIG. 5 ) to a second retention position  242 , ( FIG. 6 ) once the implant  200  is positioned between the adjacent spinous processes. In the first insertion position  236 , the first wing  222  and an elongated base element  232  of the tissue expander  224  are oriented for ease of insertion in an anterior-to-posterior direction of the patient. In the second retention position  242 , for second wing  226  ( FIG. 6 ) the elongated base element  232  of the tissue expander  224  and the first wing  222  are oriented about 90″ from the first insertion position  236 , or in other words, substantially perpendicular to the anterior-to-posterior direction of the first insertion position  236 .  
         [0031]     The implant  200  has a tissue expander  224  having a wedge-shaped distal end  226  and a proximal end  228  that is located adjacent to rotatable spacer  216  at a second distal end  220  of a rotatable spacer  216 . A first wing  222  is located adjacent to a proximal first end  218  of spacer  216 . Focusing first on the tissue expander  224 , the wedge-shaped distal end  226  is oriented in the first insertion position  236  to accommodate insertion between spinous processes  212 , 214 , with the flat distal part of the wedge  226  oriented in an anterior-to-posterior direction in a patient. Also in the first insertion position  236 , the elongated base element  232  of the tissue expander  224 , located adjacent to the spacer  216 , is oriented so that it is elongated in a direction that is anterior-to-posterior when the implant  200  is implanted laterally in a patient.  
         [0032]     With respect to the first wing  222 , when the tissue expander  224  is oriented in the first insertion position  236 , the first wing  222  is oriented, like the tissue expander  224 , in an anterior-to-posterior direction relative to a patient. As with the tissue expander  226  rotation of the shaft  248  causes the first wing  222  to rotate so that is about perpendicular to an anterior-posterior direction.  
         [0033]     In this embodiment, as indicated above, the first wing  222  and the tissue expander  224  are joined together by the shaft  248  which has a longitudinal axis  234 . The spacer  216  can rotate upon shaft  248 . Shaft  248  includes a head  250  which has a slot  252  that can accept a rotation tool such as a screwdriver. Rotation of the shaft  248  causes the first wing  222  as well as the tissue expander  224  to rotate. Thus, once the implant  200  is positioned between spinous processes, a screwdriver can be used to rotate the tissue expander  224  and the first wing  222  from the insertion position  236  as seen in  FIG. 5  to the retention position  242  shown in  FIG. 6 . In a preferred embodiment, the shaft  248  can rotate the first wing  222  as well as the tissue expander  224  about 90″. Alternatively, different amounts of rotation can be accomplished.  
         [0034]     Although the patient&#39;s tissue will hold the first wing  222  and the tissue expander  224  in the rotated position, if desired, a mechanism can be included to fix the shaft  248  in the rotated position. Such mechanism can include a detent extending from the shaft  248  which can lock into a recess in the spacer  216 . Accordingly, in the second retention position  242 , both the first wing  222  and the tissue expander  224  are rotated about 90″ and can be locked into place.  
         [0035]      FIGS. 7 and 8  depict yet another embodiment  300  of the implant of the invention. In this embodiment  300 , the tissue expander  324  has a first insertion position  336  ( FIG. 7  being a view looking down on the spinal column), and a second retention position  342  ( FIG. 8  being a view looking from posterior to anterior into the spinal column). The tissue expander  324  converts between the first insertion position  336  and the second retention  342  position through a pivoting motion, that may also include a rotation motion.  
         [0036]     In this embodiment  300 , the first wing  322  is positioned adjacent to a spacer  316  at a first end  318  of the spacer. As above with the implants  100  and  200 , the spacer  316  is rotatably mounted over a hollow spacer-mounting shaft  317  extending from the first wing  322 . The spacer  316  can be cylindrical, or it can have other shapes, including but not limited to elliptical or tear-drop shape in cross-section.  
         [0037]     The tissue expander  324  of implant  300  comprises an upper segment  380  that is pivotally connected via a pivoting joint  382 , or other pivoting means, with a lower segment  384 . That is, a second end  381  of the upper segment  380  meets a second end  383  of the lower segment  384  via the pivoting joint  382 . A coiled spring  321  is provided around pivoting joint  382  and biees both the upper segment  380  and the lower segment  384  of the tissue expander  324  against the spacer  316 . The pivoting joint  382  is connected with a first end  388  of a rod  386 . Rod  386  is slidably disposed in a bore  319  which runs the entire length of the spacer  316 , and is located within hollow spacer-mounting shaft  317 .  
         [0038]     The pivoting joint  382  and the rod  386  provide the mechanism whereby the tissue expander  324  is converted from the first insertion position  336  to the second retention position  342 . In the first insertion position  336 , depicted in  FIG. 7 , the first end  388  of the rod  386  extends outside the spacer  316 . The pivoting joint  382 , functionally connected with the first end  388  of the rod  386 , is not in contact with the second end  320  of the spacer  316 , but instead is separated by a segment of the rod  386  from the second end  320  of the spacer  316 . The upper segment  380  of the tissue expander  324  and the lower segment  384  of the tissue expander  324  meet at the pivoting joint  382  to form a wedge-shaped first end  326  of the tissue expander  324  that is not in contact with the second end  320  of the spacer  316  when the tissue expander  324  is in the first insertion position  336 . In one embodiment, wedge-shaped first end  326  of the tissue expander  324  can be wedge-shaped in the lateral direction of insertion, i.e., perpendicular to an anterior-to-posterior direction of a patient. The wedge-shaped first end  326  is useful for inserting the implant  300  between adjacent spinous processes.  
         [0039]     Rod  386  includes a head  350  at the end of the rod  386  distal from the tissue expander  324 . The head  350  has a slot  352  that can accept a tool adapted to be used to rotate and pull the rod  386  through a bore  319  of shaft  317  toward the first wing, causing the upper segment  380  and lower segment  384  of the tissue expander  324  to become aligned, such that the tissue expander  324  is no longer wedge-shaped in the first insertion position  336  ( FIG. 7 ). Instead, the tissue expander  324  adopts the form of a second wing ( FIG. 8 ). In this embodiment, the tissue expander  324  is wedge-shaped in the direction of lateral insertion in the first insertion position  336 , and the tissue expander in the second retention position is oriented substantially vertical, or substantially perpendicular to the anterior-to-posterior direction of the patient.  
         [0040]     In contrast, in another embodiment, the tissue expander  324  in the first insertion position  336  is not wedge-shaped in a top view during lateral insertion, as discussed above. Instead, the wedge-shape of the tissue expander  324  in the first insertion position  336  is wedge-shaped looking into the spine from a posterior to anterior direction. As such, merely pulling without rotating rod  386  causes upper segment  380  of the tissue expander  324  and the lower segment  384  of the tissue expander  324  to pivot about the pivoting joint  382 , as above. Thus without rotating the tissue expander  324 , the tissue expander  324  after reconfiguration will be oriented as depicted in  FIG. 8 .  
         [0041]      FIG. 9  depicts the embodiment of  FIGS. 7 and 8  deployed between spinous processes from a top view.  
         [0042]     A rotating tool, such as a hook mounted on the end of a rod, can be used to pull the rod  386  through the bore  319 , and can be used to rotate the tissue expander  324  so that it is generally parallel to the first wing  322 . In a preferred embodiment, the rod  386  can rotate the tissue expander about 90″. Alternatively, different amounts of rotation can be accomplished as needed to adapt to the anatomical structure of a patient.  
         [0043]     Although the patient&#39;s tissue will hold the tissue expander  324  in the rotated position  242 , if desired, a mechanism can be included to fix the rod  386  in the rotated position. Such mechanism can include a detent extending from head  350  which can lock into a recess in the first wing  322  as the rod  386  is pulled toward the first wing  322  and rotated when the head  350  is adjacent to the first wing  322 . Another mechanism can include ridges extending from the head  350  of the rod  386  which can lock into recesses in the first wing  322 .  
         [0044]     One of ordinary skill in the art will appreciate that the locking components need not be limited to a detent and recess. The invention contemplates any locking mechanism that can secure the implant  300  in a second retention position  342  with the tissue expander  324  reconfigured to a second wing.  
         [0045]      FIG. 10  depicts a method  400  of insertion of an embodiment of the invention from a lateral or postero-lateral approach. Using the disclosed method, any of implants  100 ,  200 , and  300  can be implanted. [0044] First, an implant as in, by way of example only, embodiment  100 , is provided  420 , and the spine is accessed  430 . Access can be accomplished laterally or posterolaterally. The implant with the tissue expander  24  in the first insertion position  36  then is inserted  440  between the spinous processes, either from the right lateral side, or the left lateral side.  
         [0046]     The tissue expander  24  is wedge-shaped in the first insertion position  36 , as described above, and is used to distract the vertebrae somewhat to facilitate the lateral insertion of the spacer  16  between the adjacent spinous processes. This level of distraction may suffice to fully insert the implant  100 . However, if additional distraction is necessary prior to insertion of the tissue expander, distraction can be added prior to insertion  435 , by methods already well-known in the art.  
         [0047]     Once the implant  100  is positioned  450  with the spacer maintaining distraction of the adjacent spinous processes, the tissue expander  24  is moved from the first insertion position to the second retention position  460 . For implant  100 , moving the tissue expander  24  involves rotating  470  the tissue expander  24  to the second retention position  42 . The rotation in one embodiment is preferably about 90″. However, varying degrees of rotation are also possible. The tissue expander  24  locks into the second retention position  42 , as described above. The base element  32  in the second retention position  42  is parallel to the first wing  22 , which also serves to retain the implant  100  in position and prevent displacement.  
         [0048]     For an implant as in embodiment  200 , both the first wing  222  and the tissue expander  224  are rotated together  470 , because in embodiment  200 , the spacer  216  is connected with the first wing  222 .  
         [0049]     For an implant as in embodiment  300 , the tissue expander  324  is moved  460  from a wedge-shaped first insertion position  336  to a retaining arm or second wing second retention position  342 .  
         [0050]     After the converting step  460  the incision is closed  470 .  
         [0051]     The foregoing description of embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention and the various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and its equivalence.