Abstract:
A technique and system is provided for efficiently, effectively and safely performing an interbody lumbar fusion. The technique and system utilizes: (1) a rotary shaver that provides a shaving cannula; (2) an outflow/insertion cannula which provides a dual purpose cannula; and (3) a fusible balloon which provides a biodegradable intervertebral bag. The patient&#39;s disc is shaved and cut out with the shaver while the shavings are sucked out with the dual purpose cannula. Afterwards, the balloon is inserted at the tip of the dual purpose cannula and the balloon is filled with a grafting substance. The balloon assumes the shape of the removed disc. The grafting substance will fuse to the balloon and to the adjacent vertebrae and provide a support where the removed disc was.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to spinal surgery, and more particularly, to a technique and system for performing an interbody lumbar fusion. 
         [0002]    A herniated disc (disk), herniated nucleus pulposis, ruptured lumbar invertebral disc, slipped disc, prolapsed disc, compressed disc, degenerative disc, injured disc, or damaged disc, can cause sever back pain. One successful method of treatment involves removing the disc, also referred to as “diskectomy”, and spinal fusion, also known as “spondylodesis” or “spondylosyndesis”. 
         [0003]    The standard way of performing a lumbar intervertebral fusion is either through an anterior approach or through a posterior approach. Either approaches involve fairly extensive dissection by which the intervertebral disc is removed and an implant, polyether ether ketone (PEEK) and/or bone, is placed into the disc space. The goal of the implanted device is to provide support for the adjacent vertebrae bodies and to ultimately fuse the adjacent vertebral bodies. Although this method can be highly effective there can be considerable postsurgical morbidity due to the extensile approach that is necessary. 
         [0004]    It is, therefore, desirable to provide an improved technique and system, which overcomes most, if not all of the preceding disadvantages. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    An improved minimally invasive surgical (MIS) technique and system are provided for performing an interbody lumbar fusion which is effective, efficient and safe. The improved MIS technique and system features a navigable disc removal device and an osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon. 
         [0006]    Among the many benefits of the improved technique and system are:
       1. no need to perform an extensile dissection;   2. uses MIS technique and therefore minimizes soft tissue dissection; and   3. the disc annulus and all ligaments surrounded the disc are spared.       
 
         [0010]    The patient friendly technique and system utilizes a two cannula posterior-lateral approach to the disc space. Both cannulas can be inserted just lateral to the lumbar facets within the safe zone below the exiting nerve of the corresponding disc. 
         [0011]    One cannula can have a cutting/shaving tip which is navigatable and the other cannula can have a suction device to extract the shaved disc and for placement of the intervertebral device. The shaving cannula can also have water inflow to introduce water into the disc space to aid extraction. 
         [0012]    On completion of disc extraction, a balloon made of a biodegradable substance such as polylatic acid or polylactide (PLA) which is a biodegradable, thermoplastic, aliphatic polyesteror, other biodegradable material can be introduced into the disc space via the extraction cannula. 
         [0013]    The balloon preferably has specific structural characteristics:
       1. not round or oval;   2. collapsible on introduction;   3. flat to concave on upper and lower surfaces when deployed; and   4. sides that are expandable in a cranial/caudal direction, medial/lateral direction, and anterior/posterior direction, which allows the device (balloon) to fully occupy the disc space.       
 
         [0018]    Once the balloon is inserted it can be filled with a fusion graft substance which on insertion and pressure becomes firm and weight bearing. After the balloon is filled with a fusion graft substance, both cannulas can be removed. 
         [0019]    In the preferred form, the MIS system comprises: a navigable intervertebral disc removal device; an intervertebral balloon; and a dual purpose cannula which has an extraction portion for extracting a shaved disc of a patient and has an insertion portion for inserting the balloon in a space where the shaved disc was extracted. 
         [0020]    The navigable intervertebral disc removal device can comprise a shaver assembly that provides a shaving cannula and/or rotary shaver. Preferably, the navigable intervertebral disc removal device has at least one power driven blade. The illustrated navigable intervertebral disc removal device can also include a shaft connected to the blade and a set of moveable shaver discs which are spaced from the blade and connected to the shaft for accommodating axial and transverse movement of the shaft. The illustrated navigable intervertebral device can also comprise a casing with a head having a shaver access opening for the blade and an outflow irrigation opening and can have a steerability (steering) section that is spaced from the shaver access opening. The navigable intervertebral disc removal advice can also comprise a flexible steering rod. The illustrated navigable intervertebral disc removal device can further have a water inflow tube. 
         [0021]    The preferred balloon comprises an osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon comprising biodegradable material. The illustrated balloon has a contour replicating and complementing a patient&#39;s disc. 
         [0022]    A more detailed explanation of the invention is provided in the following detailed descriptions and appended claims taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a top profile perspective view of a navigable intervertebral disc removal device of a minimally invasive surgical (MIS) system for performing an interbody lumbar fusion in accordance with principles of the present invention. 
           [0024]      FIG. 2  is a side profile perspective view of the navigable intervertebral disc removal device. 
           [0025]      FIG. 3  is a cross sectional side view of an osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon providing an intervertebral bag of the MIS system for performing an interbody lumbar fusion in accordance with principles of the present invention. 
           [0026]      FIG. 4  is a back profile perspective view of the navigable intervertebral disc removal device being inserted into an intervertebral disc of a patient. 
           [0027]      FIG. 5  is a posterior profile perspective view of a spinal segment of the patient. 
           [0028]      FIG. 6  is a cross sectional top profile view of the spinal segment of the patient. 
           [0029]      FIG. 7  is a top profile view of the navigable intervertebral disc removal device and a dual action cannula that provides an outflow/insertion cannula of the MIS technique and system for performing an interbody lumbar fusion in the spinal segment of the patient in accordance with principles of the present invention and illustrating in dotted line movement of the navigable intervertebral disc removal device for shaving and cutting the patient&#39;s disc into pieces. 
           [0030]      FIG. 8  is a cross sectional top profile view of the osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon inserted by the dual action cannula and an insertion rod into the disc space after the patient&#39;s disc has been removed. 
           [0031]      FIG. 9  is a cross sectional side profile view of the osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon inserted by the dual action cannula and insertion rod into the disc space after the patient&#39;s disc has been removed. 
           [0032]      FIG. 10  is a cross sectional side profile view of the osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon inserted by the dual action cannula and insertion rod in the disc space and being filled by a grafting substance to form a fusion support (fusion implant) to securely connect and fuse adjacent vertebrae bodies. 
           [0033]      FIG. 11  is a cross sectional side profile view of the fusion support in the disc space for fusing the fusion material to the osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon and adjacent vertebrae bodies after the dual action cannula and insertion rod have been removed. 
           [0034]      FIG. 12  is a perspective view of a shaver with a shaver blade, shaft and stackable discs. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    The following is a detailed description and explanation of the preferred embodiments of the invention and best modes for practicing the invention. 
         [0036]    Referring to the drawings, a minimally invasive surgical (MIS) system  100  is provided for performing interbody lumbar fusion. The MIS system has: a navigable intervertebral disc removal device  102  for removing a patient&#39;s disc  104 ; and a device providing an osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon  106 ; and a dual action cannula  108 . The term “osteoconductive” as used in this application means that the balloon assists in replacing the disc space  110  previously occupied by the patient&#39;s disc with a fusion support (fusion implant) so as to allow bones to form between and fuse to adjacent vertebrae bodies of the patient. The term “osteoinductive” as used in this application means that the balloon assists in replacing the disc space  110  previously occupied by the patient&#39;s disc with a fusion support (fusion implant) so as to induce bones to form between and fuse to adjacent vertebrae bodies of the patient. The term “osteoconductive” as used in this application means that the balloon assists in replacing the disc space  110  previously occupied by the patient&#39;s disc with a fusion support (fusion implant) so as to form bones between and fuse to adjacent vertebrae bodies of the patient. 
         [0037]    The navigable intervertebral disc removal device can comprise a shaver assembly  112  ( FIGS. 1 and 2 ) that provides a shaver cannula  114 . The navigable intervertebral disc removal device can have an outer casing  116  with an interior  118  and an elongated head  120  with a rounded convex tip  122 . The head can have a shaver access opening  124 , such as a 0.5 cm opening, and an outflow irrigation opening  126  or hole which provide a water outlet for injecting and spraying sterile water. The navigable intervertebral disc removal device can be constructed of a medical grade material, such as titanium, stainless steel or other metal or impact resistant plastic. The casing can have a steerability (steering) section with an accordion-shaped or style connection  127  that is spaced from the shaver access opening and allows steering, maneuvering and navigation of the navigable intervertebral device. The navigable intervertebral disc removal device (shaver assembly) can also include: a shaft  128  that extends into the casing, a flexible steering rod  130  that extends into the casing, and a water inlet tube  132  that extends into the casing and communicates with the outflow irrigation opening of the head. The water inflow tube can be made of medical grade material, such as plastic or rubber, and can be connected to a sterile water source such a three liter plastic bag of water. The sterile water can be pumped by a water pump or can flow by gravity flow. 
         [0038]    The navigable intervertebral disc removal device can have a shaver  133  at least one power driven circular blade  134 , such as a spiral or helical blade or a set, series, or array of circular blades, such as a 0.5 cm blade, that is accessible and communicates with the shaver access opening and is positioned within the interior of the casing for shaving, cutting and removing the patient&#39;s disc. The power driven circular blade can be a pneumatically operated rotary and/or oscillating circular blade or an electrically powered rotary and/or oscillating circular blade. A pneumatic pump or electrical motor can be mounted on or adjacent a wall in the hospital where the procedure (technique) is being performed to power the blade. The power drive circular blade can be positioned at or near a tip of the shaft. 
         [0039]    The navigable intervertebral disc removal device can also have an array, series or set of stackable moveable shaver discs  136  ( FIG. 12 ) which are spaced from the blade of the shaver and are connected to the shaft for accommodating longitudinal and lateral movement and motion of the shaft. The shaver discs can be constructed of metal or impact resistant plastic. In the illustrated embodiment, the shaver discs comprise complementary rotatable shaver discs. Each shaver disc can have a convex forward portion  138  and a rearward concave, planar or flat portion  140 . At least some of the concave portions can have a cavity  142  which provides a nipple-receiving opening  144 . At least some of the convex portions can have an axial protuberance  146  which provides a nipple  148  for engaging and is aligned with the cavity of an adjacent rearward portion. Desirably, the shaver discs are moveable in a transverse direction. 
         [0040]    The osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon preferably comprises an intervertebral bag  150  ( FIG. 3 ) with an expandable contour  152  for replicating and complementing a patient&#39;s disc. Before being expanded, the balloon is in a normally collapsed storage position in an extended and deployed form which is generally flat or slightly concave. The intervertebral bag can be expandable and/or inflatable to an expanded position in a cranial and caudal direction for occupying a disc space after the patient&#39;s disc has been removed, so that the annulus is spared. The intervertebral bag can have an interior  154  ( FIG. 10 ) to receive a grafting material  156  which provides a graft substance, such as Grafton brand grating material that is available from Osteotech, Inc. The grafting material can fuse and provide a fusion support  155  (fusion implant) ( FIG. 11 ) in the disc space for securely connecting and fusing adjacent vertebrae bodies  157  and  159  of the patient. Desirably, the intervertebral balloon comprises a medical grade biodegradable or bio-absorbable fusible material, such as polylatic acid or polylactide (PLA) which is a biodegradable thermoplastic, aliphatic polyesteror, or other plastic or paper, which can be absorbed and fused with the fusion support. A grafting material-engageable insertion rod  158  ( FIGS. 8 and 9 ) can be provided for inserting and pushing the graft substance into the interior of the intervertebral bag. The insertion rod can also give rigidity to the balloon. The insertion rod can be made of a medical grade material, such as titanium, stainless steel, or other metal or impact-resistance plastic. 
         [0041]    The dual action cannula can comprise a tube  160  ( FIG. 3 ) that provides an outflow/insertion cannula  162 . The dual action cannula can have an extraction section  164  ( FIG. 7 ) which provides a suction device and outflow inlet portion for extracting and discharging the removed patient&#39;s disc. The dual action cannula can also have an insertion portion  166  ( FIG. 8 ) for inserting the intervertebral balloon in the disc space after the patient&#39;s disc has been removed. The tubular dual action cannula can be fabricated of a medical grade material, such as titanium, stainless steel or other metal or impact resistant plastic. 
         [0042]    The back of the patient has a spinal cord  170  ( FIGS. 4-10 ) with nerve roots  174  and pedicels  176 . The patent also has spinal segments  177  with a nucleus pulposus  178  ( FIG. 6 ), annulus fibrosus  180 , hyaline cartilage  182  ( FIG. 4 ), superior articular facet  184  ( FIG. 6 ), spinous process  186 , and transverse process  188 . 
         [0043]    The MIS system is particularly useful in a minimally invasive surgical (MIS) process which provides a technique and/or procedure for performing interbody lumbar fusion. The patient is preferably administered a general anesthetic before the MIS process. The process can include inserting and navigating a navigable intervertebral disc removal device in a nucleus pulposis of a patient posteriorly and laterally of a lumbar facet and in proximity to a patient&#39;s disc in a safe zone  190  below an exiting nerve of the patient&#39;s disc. The dual action cannula can be inserted and positioned in the nucleolus pulposis posteriorly and laterally of another lumbar facet and in proximity to the patient&#39;s disc in the safe zone. The dual action cannula can be inserted before or after the navigable intervertebral disc removal device or simultaneously therewith. 
         [0044]    The MIS process, technique and procedure preferably include shaving and substantially removing the patient&#39;s disc with the intervertebral disc removal device and extracting and discharging the removed patient&#39;s disc with the dual action cannula. In the illustrated embodiment, the patient&#39;s disc is shaved with at least one rotatable cutting blade of the navigable intervertebral disc removal device and the cutting blade is pneumatically or electronically driven and rotated. Preferably, sterile water is injected through the water inlet tube into the shaving cannula about the blade during shaving and cutting to cool the blade and assist in extracting and discharging the disc shavings (cuttings). Advantageously, the cutting blade can be moved longitudinally and laterally with stackable shaver discs. 
         [0045]    The osteoconductive, osteoinductive or osteogenic, collapsible intervertebral balloon can be inserted with the dual action cannula into a disc space previously occupied by the patient&#39;s disc. A grafting substance can then be dispensed into the balloon in the disc space. Advantageously, the grafting substance and balloon are fused in the disc space adjacent vertebrae bodies of the patient to form a fusion support (fusion implant) there between. Preferably, the balloon comprises a biodegradable material and is absorbed in the fusion support. 
         [0046]    In the preferred process and system, the balloon comprises an intervertebral bag which is expanded in a cranial and caudal direction to fill the disc space and provide a contour that replicates the shape of the patient&#39;s disc. After the grafting substance is dispensed and inserted into the intervertebral bag, the grating substance is compacted and compressed, such as with the grafting material-engageable insertion rod. The navigable intervertebral disc removal device and/or dual action cannula can be removed after the grafting substance is dispensed into the intervertebral balloon. 
         [0047]    Among the many advantages of the MIS Technique and System for Performing an Interbody Lumbar Fusion are:
       1. No need to perform an extensile dissection.   2. Uses MIS technique therefore minimizes soft tissue dissection.   3. The disc annulus and all ligaments surrounded the disc are spared.   4. The ability to remove the patient&#39;s disc with a navigatable shaver cannula.   5. The fusion balloon is not round but rather replicates the shape of the patient&#39;s disc and spread the forces out along the entire end place of the vertebral body.   6. The balloon is made of a bio-absorbable substance which allows the balloon to incorporate and become part of the fusion and fusion support.   7. Superior MIS technique and system.   8. Superb capabilities for removing a patient&#39;s disc.   9. Outstanding performance.   10. Reliable.   11. Safe.   12. Light weight.   13. Portable.   14. Patient friendly.   15. Easy to use.   16. Durable   17. Economical.   18. Attractive.   19. Efficient.   20. Effective.       
 
         [0068]    Although embodiments of the invention have been shown and described, it is to be understood that various modifications, substitutions, and rearrangements of parts, components, equipment, and/or process (method) steps, as well as other uses of the MIS system and techique, can be made by those skilled in the art without departing from the novel spirit and scope of this invention.