Abstract:
Disclosed are devices and methods for the controlled movement of neighboring vertebrae and the delivery of an orthopedic implant between adjacent spinous processes. The methods are especially adapted to be performed using minimally invasive surgery or in a percutaneous manner.

Description:
REFERENCE TO PRIORITY DOCUMENT  
       [0001]     This application claims priority of co-pending U.S. Provisional Patent Application Ser. No. 60/724,632, filed Oct. 7, 2005. Priority of the aforementioned filing date is hereby claimed and the disclosure of the Provisional Patent Application is hereby incorporated by reference in its entirety.  
         [0002]     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/286,152 filed Nov. 23, 2005.  
         [0003]     This application also is related to International application Serial No. (attorney docket no. 17348-019W01), filed the same day herewith.  
         [0004]     Where permitted, the subject matter of each of the above noted provisional application, application and international application is incorporated by reference in its entirety by reference thereto. 
     
    
     BACKGROUND  
       [0005]     The present disclosure relates to devices and methods that permit implantation of an orthopedic device between skeletal segments using minimally invasive surgery. The implanted devices are then used to adjust and maintain the spatial relationship(s) of adjacent bones. Depending on the implant design, the motion between the skeletal segments can be increased, modified, limited or completely immobilized.  
         [0006]     Progressive constriction of the central canal within the spinal column is a predictable consequence of aging. As the spinal canal narrows, the nerve elements that reside within it become progressively more crowded. Eventually, the canal dimensions become sufficiently small so as to significantly compress the nerve elements and produce pain, weakness, sensory changes, clumsiness and other manifestations of nervous system dysfunction.  
         [0007]     Constriction of the canal within the lumbar spine is termed lumbar stenosis. This condition is very common in the elderly and causes a significant proportion of the low back pain, lower extremity pain, lower extremity weakness, limitation of mobility and the high disability rates that afflict this age group. The traditional treatment for this condition has been the surgical removal of the bone and ligamentous structures that constrict the spinal canal. Despite advances in surgical technique, spinal decompression surgery can be an extensive operation with risks of complication from the actual surgical procedure and the general anesthetic that is required to perform it. Since many of these elderly patients are in frail health, the risk of developing significant peri-operative medical problems remains high.  
         [0008]     In addition, the traditional treatment of surgical resection of spinal structures may relieve the neural compression but lead to spinal instability in a substantial minority of patients. That is, removal of the tissues that compress the nerves may cause the spinal vertebrae to move in an abnormal fashion and produce pain. Should instability develop, it would require additional and even more extensive surgery in order to re-establish spinal stability. Because of these issues, elderly patients with lumbar stenosis must often choose between living the remaining years in significant pain or enduring the potential life-threatening complications of open spinal decompression surgery.  
         [0009]     Recently, lumbar stenosis has been treated by the distraction—instead of resection—of those tissues that compress the spinal nerves. In this approach, an implantable device is placed between the spinous processes of the vertebral bodies at the stenotic level in order to limit the extent of bone contact during spinal extension. Since encroachment upon the nerve elements occurs most commonly and severely in extension, this treatment strategy produces an effective increase in the size of the spinal canal by limiting the amount of spinal extension. In effect, the distraction of the spinous processes changes the local bony anatomy and decompresses the nerves at the distracted levels.  
         [0010]     A number of devices that utilize this strategy have been disclosed. U.S. Pat. Nos. 6,451,020; 6,695,842; 5,609,634; 5,645,599; 6,451,019; 6,761,720; 6,332,882; 6,419,676; 6,514,256; 6,699,246 and others illustrate various spinous process distractors. Unfortunately, the placement of these devices requires exposure of the spinous processes and the posterior aspect of the spinal column. Thus, these operations still present a significant risk of peri-operative complications in this frail patient population.  
       SUMMARY  
       [0011]     It would be desirable to achieve an improved method for the placement of an orthopedic device between the spinous processes of adjacent spinal segments. A workable method of minimally invasive and/or percutaneous delivery would reduce the surgical risks of these procedures and significantly increase the usefulness of these spinous process distractors. This application discloses devices for the percutaneous placement of inter-spinous process implants. The methods of use disclosed herein provide reliable approaches that maximize the likelihood of optimal device placement and obviate the need for open surgery.  
         [0012]     The present disclosure relates to devices and methods adapted to accurately place an orthopedic device between adjacent spinous processes. The technique employs a percutaneous approach and constitutes a minimally invasive method of delivery.  
         [0013]     In one aspect, the patient is placed on his side or in the prone position. The hips and knees are flexed. The disclosed procedure is performed under x-ray guidance and the target level is identified radiographically. Bone screws are percutaneously inserted into the spinous processes of the upper and lower vertebrae of the stenotic site. A distractor is placed onto the two screws and a guide tube (with inner trocar) is placed through a distractor platform and percutaneously positioned under x-ray guidance so that the distal end of the guide tube rests immediately lateral to the space between the spinous processes. Alternatively, the procedure is performed under direct visualization using minimally invasive surgery. The inner trocar is removed and an insertion tube is placed though the guide tube. The implant is placed into the insertion tube and guided into position between the two spinous processes. In one embodiment, this is accomplished by a curvilinear guide at the distal end of the insertion tube.  
         [0014]     In another embodiment, the distraction platform is not used and a guide tube is percutaneously placed into position immediately lateral to the space between the spinous processes under X-ray guidance. The inner trocar is removed and the insertion tube is used to deliver the implant as described above. In another embodiment, guide tubes are placed on each side of the space between the spinous processes. After trocar removal, insertion tubes are placed and the implant is guided into the interspinous space from one side or the other.  
         [0015]     In another embodiment, a different distraction platform is employed. In this version, the platform bore used to position the guide tube is placed at or near the vertebral midline. The implant is advanced in a substantially straight trajectory through the ligament between the spinous processes and directly into the implantation site.  
         [0016]     The placement system described herein provides an easy and reliable way of placing an orthopedic device between the spinous processes of two adjacent vertebrae. Using this method, the implant can be placed rapidly, precisely, with a few small skin incisions and a minimized amount of tissue dissection. The method permits minimally-invasive device placement using only local anesthesia into those afflicted patients who are at least able to withstand the stress of open surgical intervention.  
         [0017]     Other features and advantages should be apparent from the following description of various embodiments, which illustrate, by way of example, the principles of the disclosed devices and methods.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  shows a perspective view of a platform of an implantation device for implanting an orthopedic device between skeletal segments.  
         [0019]      FIG. 2  shows a pair of distraction screws attached to two vertebrae prior to mounting of the platform thereon.  
         [0020]      FIG. 3  shows how the platform mounts onto the distraction screws.  
         [0021]      FIG. 4  shows the platform device, a guide tube, and an inner trocar.  
         [0022]      FIGS. 5A-5C  show various views of the guide tube.  
         [0023]      FIG. 6  shows the guide tube and a trocar collectively positioned within the platform.  
         [0024]      FIG. 7  shows the guide tube mounted on the platform after the trocar has been removed.  
         [0025]      FIG. 8  shows an insertion member prior to insertion into the guide tube.  
         [0026]      FIG. 9  shows the insertion member mounted in the guide tube, which is mounted on the platform.  
         [0027]      FIG. 10A  shows a perspective view of the insertion tube.  
         [0028]      FIG. 10B  shows a perspective, cross-sectional view of the insertion tube.  
         [0029]      FIG. 10C  shows a first side view of the insertion tube.  
         [0030]      FIG. 10D  shows a second side view of the insertion tube.  
         [0031]      FIG. 10E  shows a cross-sectional side view of the insertion tube along line E-E of  FIG. 10C .  
         [0032]      FIGS. 11A-11D  show various views of an implant.  
         [0033]      FIG. 12  shows an implant being inserted into a proximal opening of the insertion tube, which is positioned inside the guide tube.  
         [0034]      FIGS. 13A-13C  show how the implant passes through the insertion tube and into an interspinous position.  
         [0035]      FIG. 14  shows another embodiment of the implantation platform.  
         [0036]      FIG. 15  shows an additional embodiment of the implantation platform.  
         [0037]      FIGS. 16A and 16B  show another embodiment of an implantation procedure. 
     
    
     DETAILED DESCRIPTION  
       [0038]     Disclosed are devices and methods for the placement of an orthopedic implant between skeletal segments (such as vertebrae) using limited surgical dissection. The implanted devices are used to adjust and maintain the spatial relationship(s) of adjacent bones.  
         [0039]      FIG. 1  shows a perspective view of a platform device that is used to implant an orthopedic device between skeletal segments, such as between a first vertebral body V 1  and a second vertebral body V 2 . For clarity of illustration, the vertebral bodies are represented schematically and those skilled in the art will appreciate that actual vertebral bodies include anatomical details not shown in  FIG. 1 . Moreover, although described in the context of being used with vertebrae, it should be appreciated that the implantation device and associated methods can also be used with other skeletal segments. For clarity of illustration, certain anatomical details, such as the patient&#39;s skin, are not shown in the figures.  
         [0040]     With reference to  FIG. 1 , the implantation device generally includes a platform  105  that is removably mounted onto elongated distraction screws  110   a  and  110   b  (collectively screws  110 ). The platform  105  includes a movably adjustable mounting member  115  having a bore  122  that receives tools for guiding and inserting an implant into a space  127  between adjacent vertebrae. While not illustrated for simplicity, an additional instrument can be used to separate and retain sides  120  of the platform  105  and thereby distract the space  127  between the two spinous processes or vertebrae in the longitudinal plane. Alternatively, a rack-like ratcheting member can be added to the platform  105  in order to distract and maintain the distracted position of the two vertebrae. Further, distraction screws  110  can be also used to alter the vertebral alignment in the horizontal plane. Thus, the screws  110  and the platform  105  can be used to actuate, manipulate and/or move the vertebral bodies V 1 , V 2  relative to one another so as to achieve a desired spatial relationship. With the vertebrae retained by distraction screws  110  and platform  105 , the intended implant placement site can be defined relative to the position of the screws  110 , the position of the platform  105  and/or the spatial relationship between them. The implant is then guided to the intended implantation site based on these defined spatial positions.  
         [0041]      FIG. 2  shows the two vertebrae prior to mounting of the platform  105 . The distraction screws  110   a  and  110   b  are anchored onto the spinous processes of vertebrae V 1  and V 2 , respectively, such that each distraction screw  110  is attached at its distal end to a separate vertebra. In this regard, the distal end of each screw  110  can include a structure for attaching to the spinous process, such as a threaded shank  112 .  
         [0042]      FIG. 3  shows how the platform  105  mounts onto the distraction screws  110 . The platform  105  includes a pair of elongated sleeves  305   a  and  305   b  that are sized and positioned to receive the distraction screws  110   a  and  110   b , respectively, within internal shafts of the sleeves. When the sleeves  305  are inserted over the distraction screws  110 , the platform  105  is mounted over the vertebrae as shown in  FIG. 1 .  
         [0043]     With reference to  FIG. 4 , the implantation device further includes a guide tube  405  and a trocar  410 . The guide tube  405  is sized and shaped to be inserted into the bore  122  , as represented by the line A in  FIG. 4 .  FIG. 5A  shows a perspective view of the guide tube  405 ,  FIG. 5B  shows a side view of the guide tube  405 , and  FIG. 5C  shows an end-wise view of the guide tube  405 . The guide tube has a proximal end  505  and a distal end  510 . The guide tube  405  is hollow such that an internal shaft extends therethrough with the internal shaft opening at the proximal  505  and distal ends  510  of the guide tube  405 . A slot-like opening  515  is located at the distal end  510  along one side of the guide tube  405 .  
         [0044]     The guide tube  405  includes alignment means  520 , such as indentations  520 , on its outer wall that are intended to interact with the complimentary protrusions in the mounting member  115 . The indentations  520  permit placement of the guide tube  405  in a predetermined orientation relative to the mounting member  115  of the platform  105 . In this way, the guide tube  405  is always placed with the distal opening  515  facing the space  127  between the spinous processes, as described below. Likewise, the guide tube  405  has protrusions  527  on its inner wall that compliment indentations  1025  on the outer wall of an insertion tube  805  (described below). These features ensure that the distal openings of both tubes face the space between the spinous processes, as described in more detail below.  
         [0045]     With reference again to  FIG. 4 , the trocar  410  is sized and shaped to be inserted into the guide tube  405 , as represented by the line B.  FIG. 6  shows the guide tube  405  and trocar  410  collectively positioned within the bore  122  of the platform  105 . That is, the trocar  410  is positioned within the guide tube  405  and the guide tube  405  is positioned within the bore  122 . When positioned as such, the opening  515  ( FIGS. 5A, 5B ) is positioned adjacent to and oriented toward the space between the vertebrae V 1  and V 2 .  
         [0046]     The trocar  410  can be removed from the guide tube  405  while the guide tube  405  remains mounted in the mounting member  115  of the platform  105 .  FIG. 7  shows the guide tube  405  mounted on the platform  105  after the trocar  410  has been removed from the guide tube  405 . With reference now to  FIG. 8 , the implantation device further includes an insertion tube  805  that is sized and shaped to insert into the guide tube  405 , as represented by the line C in  FIG. 8 .  FIG. 9  shows the insertion member  805  mounted in the guide tube  405 , which is mounted on the mounting member  115  of the platform  105 .  
         [0047]     The insertion tube  805  is now described in more detail with reference to  FIGS. 10A-10E . The insertion tube  805  is adapted to receive and guide an implant into a space between the vertebrae, as described below. The insertion tube  805  is elongated and includes an passageway  1005  that opens at both a distal end  1010  and proximal end  1015  of the insertion tube  805 . The distal opening  1020  is positioned on a side of the insertion tube  805 . As mentioned, the insertion tube  805  includes alignment means, such as indentations  1025 , on its outer wall. The indentations  1025  are sized and shaped to mate with the protrusions  527  ( FIG. 5C ) on the inner wall of the guide tube  405 . In this manner, the distal opening  1020  of the insertion tube  805  aligns with the distal opening  515  of the guide tube  405  when the insertion tube  805  is positioned within the guide tube  405 .  
         [0048]     With reference to  FIGS. 10B and 10E , the internal passageway  1005  of the insertion tube  805  includes a guide ramp  1030  or other such structure adjacent the opening  1020 . The guide ramp  1030  is adapted to guide an implant toward the opening  1020  as the implant is moved down the passageway  1005 , as described below. It should be appreciated that other structures can be used to guide the implant toward the opening  1020 . In one embodiment, the ramp  1030  has a shape that compliments the shape of an implant that is guided through the insertion tube  805 .  
         [0049]      FIGS. 11A-11D  show various views of an exemplary implant  1105  that can be used with the implantation device described herein. The implant  1105  is sized and shaped to slidably fit within the passageway  1005  ( FIG. 10B ) of the insertion tube  805 . The implant  1105  can be, for example, a device intended to preserve vertebral movement or a fusion device that immobilizes vertebral movement. For clarity of illustration, structural details of the implant  1105  are not shown in  FIGS. 11 A-11D , although it should be appreciated that the implant  1105  can have a variety of structures, shapes and sizes.  
         [0050]     An exemplary method of use for the implantation device is now described. Pursuant to the method, the platform  105 , bore  122 , and/or the guide  405  and insertion tubes  805  are positioned and aligned in a defined relationship relative to the intended implant placement site. The platform  105  can be movable or stationary or it can change between a movable and stationary state. The guide tube  405  and/or insertion tube  805  can be percutaneously positioned into a defined spatial relationship relative to the intended implant placement site based on their interaction with the platform  105 .  
         [0051]     With reference to  FIG. 2 , the distraction screws  110  are first anchored onto the vertebral bodies. Next, as shown in  FIG. 3 , the platform  105  is mounted onto the distraction screws  110  by sliding the sleeves  305  over the distraction screws  110 .  
         [0052]     It should be appreciated that the platform  105  can be attached to the vertebrae by other means. For example, the platform  105  can attach onto one or more spinous process using a clamp or spinous process-encircling attachment. Moreover, the platform  105  can be also attached to a first vertebra using a single distraction, clamp or encircling attachment while a secondary post rests within the inter-spinous space (that is, the space between the two spinous processes) and abuts the spinous process of the second vertebra. An example of the method is shown in  FIG. 15 . Alternatively, the platform  105  can contain one or more attachments that are positioned within the inter-spinous space and that can attach onto or abut one or both spinous process. Finally, the platform can attach onto a single vertebrae that would forgo the ability to manipulate the spatial relationship between the vertebrae but retain the implant placement function. It should be appreciated that the preceding are exemplary embodiments and do not constitute an exhaustive list of potential platforms.  
         [0053]     After the platform  105  is mounted, the mounting member  115  of the platform  105  is then movably adjusted to a position at the level of the space between the vertebral bodies (i.e., the spinous processes) under x-ray guidance and then locked in position, such as by using a locking screw  125  or other locking means. With reference to  FIG. 4 , the trocar  410  is then inserted into the guide tube  405  and both are placed through the bore  122  of the mounting member  115 , as shown in  FIG. 6 . The guide tube  405  and the trocar  410  have been pushed through the skin such that their distal ends approach toward the vertebral bodies. At this stage in the procedure, the distal opening  515  ( FIG. 5A ) of the guide tube  405  is positioned such that it is adjacent to and opens toward the space  127  between the vertebral bodies. The trocar  410  is then removed from the guide tube  405  such that the empty guide tube  405  is mounted on the platform  105  with the distal end  510  of the guide tube  405  is adjacent to the space  127  between the vertebral bodies V 1 , V 2 , as shown in  FIG. 7 .  
         [0054]     Insertion tube  805  is inserted into the guide tube  405 , as shown in  FIG. 8 , and advanced through the tissues until the distal end  101 O is positioned adjacent to the desired implant placement site. The distal opening  1020  ( FIG. 10A ) of the insertion tube  805  is aligned with the distal opening  515  of the guide tube  405 . Both openings  515 ,  1020  are positioned such that they are open toward the space  127  between the vertebral bodies. Implant  1105  is inserted into the proximal opening of the insertion tube  805 , as shown in  FIG. 12 . A pusher can be used to advance the implant  1105  in a direction  1300  through the inner passageway  1005  of the insertion tube  805  and toward the desired position in inter-spinous space  127 .  FIGS. 13A-13C  show how the implant  1105  passes through the insertion tube  805  and into an interspinous space  127 . As shown in  FIG. 13A , the implant  1105  has been pushed through the passageway  1005  to a position near the distal end  1010  of the insertion tube  805 .  
         [0055]     As mentioned, the guide ramp  1030  is adapted to guide the implant  1105  toward the opening  1020  and toward the interspinous space  127 . With reference to  FIGS. 13B and 13C , the implant  1105  is pushed out of the opening  1020  and into the desired location within the inter-spinous space  127 . After implant placement, all of the implantation devices are removed but the implant  1105  is retained.  
         [0056]     In the embodiments described above, the insertion tube  805  is positioned within the platform  105  along an axis that is offset from the vertical midline M such that the implant  1105  approaches the implant site from the side. In another embodiment, the platform bore  122  that is used to position the insertion tube  805  is placed at or near the vertebral midline M. An example of this platform embodiment is shown in  FIG. 14 . In this procedure, the implant  1105  is advanced in a substantially straight trajectory through the ligament (not visible) between the spinous processes and directly into the implantation site. Moreover, the insertion tube  805  has no guide ramp  1030  so as to provide the desired straight implant placement trajectory through the insertion tube  805 .  
         [0057]      FIGS. 16A and 16B  show another embodiment of an implantation procedure. In this embodiment, the distraction platform  105  is not employed. During implantation, the guide tube  405  and the trocar  410  are positioned adjacent to the interspinous space  127  under X-ray or direct visual guidance. The guide tube  405  is positioned over a series of progressively larger tubes. Once positioned, the insertion tube  805  is passed into the guide tube  405 . The implant  1105  is then guided and placed into the interspinous space via the insertion tube  805  in the manner described above. In another embodiment, two or more tubes can be placed on each side of the interspinous space and the implant  1105  can be passed between the two tubes into the implantation site.  
         [0058]     Although embodiments of various methods and devices are described herein in detail with reference to certain versions, it should be appreciated that other versions, embodiments, methods of use, and combinations thereof are also possible. Therefore the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.