Abstract:
There is disclosed systems and methods for spinal nucleus replacement by constructing channels through vertebral segments on either side of an area into which the spinal nucleus is to be positioned, the channels running from a channel end outside of the area to a channel end abutting the area. One end of a suture is inserted into the outside channel end of a first one of the channels and passed through the first channel and into the area and out of the area through the second channel until it emerges from the second channel. The suture is then used to pull the nucleus into the area.

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/007,648 filed Dec. 7, 2004 now abandoned and entitled “Nucleus Replacement Securing Device and Method”, which claims priority to U.S. Provisional Patent Application Ser. No. 60/527,855 entitled “Nucleus Replacement Securing Device and Method”, filed Dec. 8, 2003, the disclosure of which is hereby incorporated herein by reference. 
     TECHNICAL FIELD 
     This invention relates to securing of a nucleus replacement and more specifically, to assistance in placing, stabilizing, and securing of a nucleus replacement in the disc space between two adjacent vertebrae from a posterior, posterolateral, or lateral approach. 
     BACKGROUND OF THE INVENTION 
     Spinal discs are the primary mechanical cushion for the vertebral column and permit controlled motion between the vertebral segments. Over time, these discs have a tendency to loose water which in turn reduces their cushioning ability. Along with a reduced hydraulic nature, the disc loses its ability to maintain disc height and bear loads resulting in a cascade of degenerative effects. As this degenerative process continues, a disc herniation involving bulging or expelling of disc material can occur leading to pain to the back and lower extremities. When this occurs, it is necessary to remove the herniated disc and reestablish disc height, ultimately in an effort to reduce or eliminate pain. 
     When the pain generating disc is removed, the disc space will collapse resulting in instability and further trauma to surrounding tissue and ensuing pain. Current treatments include installing a bone brace, cage, or other load bearing means often along with bone growth stimulators in an effort to cause fusion of the segment and thus alleviate the pain. This process is, however, believed to place undo stress on other vertebral levels as they compensate for the lack of motion, in turn potentially leading to premature failure of those other discs as well. 
     An improved solution includes replacing the removed internal portion of the disc, or the nucleus, with a nucleus prosthesis to act as the load bearing and motion stabilizing feature in an effort to restore natural spine biomechanics. 
     Devices such as these are outlined in U.S. Pat. No. 6,602,291 wherein the nucleus replacement is inserted into the disc space is a reduced size state, and then is hydrolyzed (or otherwise expanded) to fill the gap. Current methods and concepts have undergone human clinical trials to little success and suffers from an inability to access, place, and then finally secure the nucleus replacement in place. Several attempts at human trials have even resulted in expulsion of these devices out of the disc space. This problem must be addressed to make this technology a viable possibility in spine treatment. 
     BRIEF SUMMARY OF THE INVENTION 
     There is disclosed systems and methods for spinal nucleus replacement by constructing channels through vertebral segments on either side of an area into which the spinal nucleus is to be positioned, the channels running from a channel end outside of the area to a channel end abutting the area. One end of a suture is inserted into the outside channel end of a first one of the channels and passed through the first channel and into the area and out of the area through the second channel until it emerges from the second channel. The suture is then used to pull the nucleus into the area. 
     In a first embodiment, an alignment device mounts to the posterior aspect of the spine and drills curved holes down through the pedicle of the segment and into the disc space of the level. At the adjoining level, holes are also drilled in the pedicle into the adjoining disc space so that each exit of the curved hole meet at a single disc space. A suture is then threaded through the first curved hole, to the disc space, then is extracted from the disc space to the posterior. The suture is threaded through a nucleus replacement, or through the covering around a nucleus replacement, and then back into the disc space where it is pulled through the second hole and out to the pedicle. Having a suture that goes through each pedicle and around the nucleus replacement allows the suture to be pulled from both ends to urge the nucleus replacement into position still secured to the suture. Plugs are then inserted into the pedicle and attached to the suture so as to fix the suture in place. The suture is then cut keeping the nucleus replacement in a fixed position within the disc space. The suture holds the nucleus replacement secured to a fixed position after it has been guided into place. While the nucleus replacement may be permitted a certain amount of movement in certain embodiments, it is secured within the disc space so as not to be expelled therefrom. 
     In a second embodiment, the ends of the suture expelled from both pedicles are joined with a tension band between the two pedicles that can act as a further stabilizing effect to the segment. 
     In a third embodiment, the pedicles of the same vertebra are used as access into the adjacent disc space. The two sutures or pathways are through the superior vertebral end place of the vertebra. This allows preservation of the entire periphery of the annulus fibrosis if the nucleus replacement is collapsible and can be inserted through the pedicle. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter. It should be appreciated that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized that such equivalent constructions do not depart from the invention. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  shows a side view of the first embodiment; 
         FIG. 2  shows a section view taken through line  2 - 2  of  FIG. 1 ; 
         FIG. 3  shows a side view of the second embodiment; 
         FIGS. 4A and 4B  show a top view and a side view of the third embodiment; 
         FIGS. 5A and 5B  show top and side views of a vertebra having a collapsible reinforcement mesh; and 
         FIGS. 6A ,  6 B, and  6 C show side views of a vertebral level having the invention implanted, the invention including a flexible rod which allows a supplemental rigid rod for salvage. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to  FIG. 1 , vertebral segment  10  includes superior vertebral level  20  and inferior vertebral level  30 . These are shown as level L 4  and level L 5  in this example, however the concepts taught herein could be used at any level in the spine. A description of a first embodiment of a device and method for using the device for inserting and securing a replacement nucleus within a disc space is now described in connection with vertabral segment  10  of  FIG. 1 .  FIG. 1  shows a nucleus replacement  50  which must be inserted into the disc space  40 . To assist this endeavor, two holes  53   a  and  53   b  are drilled into the vertebral levels  64 ,  65  using fluoro to track a cutting bit in its path, starting from the opening of the pedicles  55   a ,  55   b  and extending on a curved path to the disc space  40  as shown. 
     After the holes are drilled, a suture  60  starting with end  62  is passed through the L 4  pedicle opening  55   a , through the first tunnel  53   a , and into the disc space  40  passing the entry point  54   a . In the first embodiment, the suture would then be grasped and pulled through a posterior opening in the disc space  40 , and out to the posterior of the patient. Suture  60  is then mated to nucleus replacement  50 , and suture  60  is passed back down the access port to the disc space  40  where it is guided back down to the second tunnel  53   b  through opening  54   b . As an aide, a tool could be passed through the opening of pedicle  55   b , through tunnel  53   b , into the disc space  40 . The tool would grab suture  60  and pull end  62  through opening  54   b , through tunnel  53   b , and out to pedicle opening  55   b  where it is pulled out of the body. 
     This method leaves end  62  of suture  60  extending out of the patient and the opposite end  61  of suture  60  also extending out of the patient. The suture would most likely have been cut off at the appropriate length. Suture ends  61 ,  62  are then pulled out away from the patent, pulling with it nucleus prosthesis  50  that is attached to suture  60 . In this way, nucleus replacement  50  is pulled into disc space  40  so that holes  54   a ,  54   b  are directly in line with the suture connection point at the nucleus prosthesis. 
     At this point knots, anchors (not shown) or other stop devices could be attached to suture ends  61 ,  62 . If anchors are used, they would be forcibly press fitted or threaded into the pedicle. The anchors could have features on them that mate with the suture to allow tension and reduction of length on suture ends  61 ,  62  in a zip tie approach so as to maintain position of suture  60  and thus of nucleus replacement  50  at all times. The remaining suture ends would then be cut off flush or above flush to the anchors. 
     In another embodiment, end  62  of suture  60 , while being installed, would pass from opening  54   a  of disc space  40  directly into opening  54   b  and urged through tunnel  53   b  to opening  55   b  of the L 5  pedicle and pulled out of the patient. With end  62  of suture  60  extending out of the patient, a tool could be inserted through opening  56  to disc space  40 , grabbing the suture  60  and pulling slack granted at either end through opening  56  and out of the patient. At this point, nucleus  50  would be harnessed to suture  60  at points  51  and  52 . In so doing, nucleus replacement  50  is now secured to suture  60 . Slack from suture  60  can now be pulled out by suture ends  61 ,  62 , thereby pulling nucleus replacement  50  into disc space  40 , with points  51 ,  52  positioned in line with openings  54   a ,  54   b . Anchors would then be applied in the manner and fashion described above. 
     While in some instances nucleus replacement  50  may be a single device, in other implementations it may include multiple devices that are inserted into disc space  40 . Turning to  FIG. 2 , a cross-section of the vertebral segment taken at line  2 - 2  of  FIG. 1  is shown including vertebra  30  or L 5  having spinus process  240 , transverse processes  220   a ,  220   b , and pedicle openings  55   b ,  155   b  which have been created by the method described above. The example of  FIG. 2  shows an implementation in which two nucleus replacement devices ( 50   a  and  50   b ) have been inserted into disc space  40 . For example, nucleus replacement  50   a  is inserted in the manner described above in connection with  FIG. 1  for nucleus replacement  50 , and nucleus replacement  50   b  is inserted in a similar manner. Cannulas  210 ,  211  are placed over the openings  55   b ,  155   b  to pass nucleus replacements  50   a ,  50   b  into the disc space  40 . Suture  60  is shown coming out of the page at points  60   a ,  60   b  through attachment points  52   a ,  52   b  (not shown). The posterior longitudinal ligament (PLL)  230  is also shown in this view as being saved, making this method desirable for vertebral stability as the PLL  230  supplies mach of the posterior stability. 
     As a method, the nucleus replacements  50   a ,  50   b  are passed through cannulas  210 ,  211 , through opening  56   a ,  56   b  of the disc space, and passed into the disc space  40 . The nucleus replacement travel ends when holes  51   a ,  51   b , and  52   a ,  52   b  (not shown), line up with holes  54   a ,  54   b  and  64   a ,  64   b  (not shown) with suture  60   a  passing though the left prosthesis  50   a , and suture  60   b  passing through the right prosthesis  50   b.    
     Turning to  FIG. 3 , anchors  70 ,  71  are shown entering into pedicle holes  55   a  and  55   b . At the proximal end of anchors  70 ,  71  are suture  60  securing means  72 ,  73  from which suture  60  is expelled. In this unique embodiment, suture ends  61  and  62  are joined at the ends to an elastic tension member  80  serving as a ligament to the anchors to achieve distraction of the disc space and to promote healthy biomechanics throughout the segment. The nucleus replacement  50  is shown in position within the disc space. 
     Turning to  FIGS. 4A and 4B , a lower vertebra is shown in  FIG. 4A  with anchors  401  placed in the pedicles. The anchors allow for passage of suture through the pedicle to secure nucleus replacement  50  as described above. To assist with bone absorption and subsidence, as shown in  FIG. 4B , nucleus replacement  50  could have a metal base  402  placed on one side to provide stability against the end plate. This metal base plate could be cobalt chrome or another biocompatible metal or it could be plastic, or rigid material. The nucleoplasty would be delivered in a translateral lumbar approach to the disc space. The anchors would be used to maintain position of the device and aid in insertion as described above. 
     Turning to  FIGS. 5A and 5B , a vertebral segment is shown including a cross section through the disc space of the lower vertebra. More specifically,  FIG. 5A  corresponds generally with the view of  FIG. 1  and  FIG. 5B  corresponds generally with the view of  FIG. 2 . Also shown are a plurality of reinforcement mesh elements  500  (shown as elements  500 A and  500 B in  FIG. 5B ) which are collapsible under load. These mesh elements function to reinforce the end plate and the bone central to the end plate. That is, mesh elements  500  include a hole through which suture  60  is pulled, wherein mesh elements  500  reinforce the end plate and the bone central to the end plate to, for example, aid in preventing the hole in the underlying bone from growing larger over time due to stress presented thereto by the suture  60 . This in turn allows for greater load bearing capability while avoiding bone absorption by the body as well as subsidence of an intervertebral implant. Suture ends  62 A and  62 B are shown in illustration (a), which are pulled through holes  501 A and  501 B of mesh elements  500 A and  500 B, respectively. 
     Turning to  FIGS. 6A ,  6 B, and  6 B, a side view of a vertebral segment is shown in  FIG. 6A  having pedicle anchors  601  which have a tension member  602  positioned at the distal end of the anchors. In this embodiment, a flexible rod  603  is secured to the anchors  601  between the segments to provide a dynamic stabilization system including the tension member in front and the counter tension member posterior. As shown in  FIG. 6B , a salvage means including a supplemental rigid rod  604  which further secures to flexible rod  603  or anchors  601  can be used to allow for rigid fixation for fusion. One such fixation means of the supplemental rigid rod is shown in  FIG. 6C  which entails a piggy-back and interlock design. Rigid rod  604  includes a cylindrical cut that mates to flexible rod  603 . It then locks to flexible rod  603  to make a conventional fusion. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the invention is intended to encompass within its scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.