Abstract:
Briefly, the present invention is directed to methods and instrumentation for performing surgery on the spine along its lateral aspect (side) and generally by a lateral, anterior or an anterolateral surgical approach, such that the instruments enter the body from an approach that is other than posterior and make contact with the spine along its lateral aspect. The present invention provides for the entire surgical procedure to be performed through a relatively small incision and may be performed in either the thoracic or lumbar spine.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    In accordance with 37 C.F.R 1.76, a claim of priority is included in an Application Data Sheet filed concurrently herewith. Accordingly, under 35 U.S.C. §119(e), 120, 121, and/or 365(c) the present invention claims priority of U.S. Patent Application No. 61/585,724, entitled “ACCESS ASSEMBLY FOR ANTERIOR AND LATERAL SPINAL PROCEDURE”, filed on Jan. 12, 2012. The contents of each of the above referenced applications are herein incorporated by reference in its entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates generally to stabilization of adjacent bony structures of the spine and more particularly to an assembly and method for providing anterior and/or lateral access to the disc space of the vertebrae for providing stabilization to the bony structures thereof. 
       BACKGROUND INFORMATION 
       [0003]    It is widely held that healing and/or structural correction is greatly facilitated when a bone is stabilized in the proper position. Various devices for stabilization of bone are well known and routinely practiced in the medical arts. For example, an abnormal spine can be stabilized using a substantially rigid or semi-rigid interconnecting means (rod or plate) and fastening means (screws, clamps, hooks, claws, anchors, or bolts). Multiple fasteners are placed into the spinal pedicle of each vertebra and linked by at least one interconnecting means. Once in place, these systems substantially immobilize the spine and promote bony fusion (arthrodesis). 
         [0004]    With respect to the thoracic spine, it may be afflicted with a variety of ailments, some so severe as to require surgical intervention. A disc herniation may compress the spinal cord and/or nerve roots and cause pain, loss of function, and even complete paralysis of the legs with loss of bowel and bladder control. The correct treatment for such conditions is the removal of the offending discal tissue. However, this has proven both difficult and quite dangerous. When the discs of the thoracic spine are approached posteriorly (from behind), the spinal cord is in the way. To approach the same herniation anteriorly (from the front) requires the very formidable procedure of thoracotomy (cutting open the chest) and moving the heart and lungs out of the way. 
         [0005]    Quite recently surgeons have begun performing these procedures from a lateral approach to the spine (from the side) using fiber optic viewing instruments called thorascopes and numerous small surgical openings through the chest wall (portals) through which various surgical instruments, such as burrs, rongeurs and curettes, may be placed to remove these disc herniations while avoiding formal thoracotomy. Because the discs are very narrow in the thoracic spine and the surgeon is approaching the spine laterally, there is very little space in which to work as the disc is entered. Therefore, the amount of disc removal may be limited. Alternatively, the surgeon might remove the pedicle to gain access to the spinal canal risking further weakening of the already diseased area. 
         [0006]    Sometimes, for a variety of reasons, including the removal of disc material, the thoracic spine may become unstable (too much motion) at any given level. Historically, this has been treated by fusion, the joining together permanently of the unstable vertebrae via a bridge of bone so as to eliminate all motion at that location. Fusions about the thoracic spine have been performed either anteriorly or posteriorly, either procedure being a serious surgical undertaking. 
         [0007]    Stability of the spine is required for fusion to occur. For this reason, and for the purpose of correcting spinal deformity, it is often necessary to use hardware to rigidly internally fixate (stabilize) the spine. To date, the only benefit the use of the thorascope has provided in this regard is to allow the previous thoracotomy incision to be somewhat smaller. 
         [0008]    Thus, the prior art includes numerous drawbacks which have not been entirely addressed. Traditionally, the surgical techniques for stabilization of bone required large incisions (upwards of 6 cm in length) and a considerable amount of muscle be cut and stripped away (retracted) from the bone for an “open” visualization of the bone and access thereto for the placement of the fasteners and instrument implantation. Although this so-called “open” surgical technique has successfully treated non-unions, instability, injuries and disease of the spine, it is not without disadvantages. Given the invasive nature of this technique, a lengthy healing time and considerable post-operative pain for the patient is common. 
         [0009]    With respect to the human lumbar spine, the treatment of discal disease with neural compression has generally been from a posterior (from behind) approach. Lumbar discs are generally quite large and it is only those protrusions occurring posteriorly which compress the neural elements, which are themselves posterior to the discs. These posterior approaches have included both true posterior approaches and posterolateral approaches to the discs. Further, such approaches have been made via open incisions or through percutaneous stab wounds. In the latter case, instruments are inserted through the stab wounds and monitored by the use of radiographic imaging or the use of an endoscopic viewing device. While it is possible to also decompress a posterior disc herniation in the lumbar spine from an anterior approach (from the front), doing so requires the removal of a very substantial portion or all of the disc material in the front and mid portions of the disc, thus leaving that disc and that spinal segment generally unstable. Therefore, such an anterior approach to the lumbar spine has been reserved for those instances where a fusion is to be performed in conjunction with, and following such a disc removal. 
         [0010]    Fusion is generally induced with the application of bone or bone like substances between bones to induce bony bridging; such procedures have been performed outside the vertebral bodies and/or between the vertebral bodies, the latter being known as an interbody fusion. Such interbody fusions have been performed from posterior, posterolateral and anterior. Interbody fusion from the posterior approach, while still in use, has been associated with significant complications generally related to the fact that the delicate dural sac and the spine nerves cover the back of the disc space and are thus clearly at risk for damage with such an approach. The posterolateral approach has generally been utilized as a compliment to percutaneous discectomy and has consisted of pushing tiny fragments of morsalized bone down through a tube and into the disc space. 
         [0011]    In anterior interbody spinal fusion, the path of entry of the fusion material into the intervertebral space is performed from a straight anterior position. Such an anterior position is achieved in one of two ways. First, by a straight anterior approach which requires that the peritoneal cavity, which contains the intestines and other organs, be punctured twice, once through the front and once through the back on the way to the front of the spine; or secondly, by starting on the front of the abdomen off to one side and dissecting behind the peritoneal cavity on the way to the front of the spine. Regardless of which approach to the front of the spine is used, and apart from the obvious dangers related to the dense anatomy and vital structures in that area, there are at least two major problems specific to the anterior interbody fusion angle of implant insertion itself. First, generally at the L.sub.4 and L.sub.5 discs, the great iliac vessels bifurcate from the inferior vena cava and lie in close apposition to and covering that disc space, making fusion from the front both difficult and dangerous. Secondly, anterior fusions have generally been done by filling the disc space with bone or by drilling across the disc space and then filling those holes with shaped implants. As presently practiced, the preferred method of filling the disc space consists of placing a ring of allograft (bone not from the patient) femur into that disc space. An attempt to get good fill of the disc space places the sympathetic nerves along the sides of the disc at great risk. Alternatively, when the dowel technique is used, because of the short path from the front of the vertebrae to the back and because of the height of the disc as compared to the width of the spine, only a portion of the cylindrical implant or implants actually engage the vertebrae; thus compromising the support provided to the vertebrae and the area of contact provided for the fusion to occur. 
         [0012]    There is, therefore, in regard to the lumbar spine, a need for a new method and apparatus for achieving interbody fusion which avoids the problems associated with all prior methods, and which have included, but are not limited to, nerve damage when performed posteriorly, or the need to mobilize the great vessels when performed anteriorly. Further, the size of the implants are limited by the dural sac posteriorly, and the width of the spine and the delicate vital structures therewith associated anteriorly. Such a method and apparatus for interbody fusion should provide for optimal fill of the interspace without endangering the associated structures, and allow for the optimal area of contact between the implant or implants and the vertebrae to be fused. The method and apparatus should also provide controlled distraction of the bony structures while also providing an interlocking connection to the bony structures to prevent movement or dislodgement of the apparatus. 
       SUMMARY OF THE INVENTION 
       [0013]    Briefly, the present invention is directed to methods and instrumentation for performing surgery on the spine along its lateral aspect (side), and generally by a lateral, anterior or an anterolateral surgical approach, such that the instruments enter the body from an approach that is other than posterior and make contact with the spine along its lateral aspect. The present invention provides for the entire surgical procedure to be performed through a relatively small incision and may be performed in either the thoracic or lumbar spine. 
         [0014]    In the preferred embodiment, the access assembly of the present invention comprises a guide wire, a distractor, and a dynamic tube assembly that includes a manually operable locking member for securing the dynamic tube assembly to the bony structure. In at least one embodiment, the locking feature of the dynamic tube assembly may also be utilized for providing additional controlled distraction of the bony structures. The guide wire is provided for initial insertion into the disc space through a small incision in the patient with the assistance of x-rays, thorascope, image intensifier, direct vision or the like. For example, for surgery in the thoracic spine, a small incision in the chest cavity of the patient is made from a lateral approach to the thoracic spine. For surgery in the lumbar spine, a small incision may be made in the abdominal wall of the patient. Once positioned, the guide wire extends between the disc space to outside of the patient to provide a guideway for the distractor member. The distractor is generally an elongated member having a small central aperture sized for cooperation with the guide wire. A first end of the distractor includes a tapered end and a pair of generally flat opposing side surfaces extending along a portion of the length thereof. The opposing side surfaces are spaced a predetermined distance apart to provide a desired distraction (spacing) and alignment of the vertebrae. The second end of the distractor is provided with a surface suitable for striking with a mallet or the like. The outer surface of the distractor is preferably round to act as a guide surface for the dynamic tube assembly. 
         [0015]    The dynamic tube assembly includes an outer tube member and an inner lock member. The inner lock member includes an inner bore sized for cooperation with the outer surface of the distractor member. In this manner, the distractor acts as a guideway for the dynamic tube assembly. The dynamic tube assembly is constructed and arranged so that a portion of the lock member and outer tube member extend a short distance into the disc space adjacent the side surfaces of the distractor and between the two opposed surfaces. The lock member is then rotatable to engage the opposing bony surfaces of the disc space. In this manner, the lock member secures the first end of the dynamic tube assembly into place and releases the distractor member for extraction from the patient through the bore of the dynamic tube assembly. In some embodiments the lock member may include a shaped cam surface that provides additional controlled distraction of the disc space during rotation thereof. The locking function prevents the first end of the dynamic tube assembly from being inadvertently moved from its intended position once placed, while maintaining the adjacent vertebrae in a distracted position and aligned position. Once the dynamic tube assembly is in place within the patient, the distractor and guide wire may be removed, providing an access tunnel to the disc space. The tunnel is provided with sufficient diameter for disc modification or removal as well as the placement of spacers, bone fragments, implants and the like to be passed therethrough to the disc space. Once the operation is completed, rotation of the lock member releases the dynamic tube assembly for removal from the patient. 
         [0016]    Accordingly, it is an objective of the present invention to provide a device and method for performing surgery on the thoracic spine through the chest cavity from a lateral approach to the spine. 
         [0017]    It is a further objective of the present invention to provide a device and method for performing a thoracic discectomy, an interbody fusion, and rigid internal fixation of the spine through the chest cavity from a lateral approach as a single integrated procedure. 
         [0018]    It is yet a further objective of the present invention to provide a device and method for performing a lumbar fusion from the lateral aspect of the spine. 
         [0019]    It is another objective of the present invention to provide a method and device for performing a lumbar fusion and spinal canal decompression from the lateral aspect of the spine. 
         [0020]    It is yet another objective of the present invention to provide a device and method for performing a lumbar fusion, decompressive discectomy, and a rigid internal fixation of the spine as a single integrated surgical procedure. 
         [0021]    It is still yet another objective of the present invention to provide a device and method to achieve discectomy, fusion and interbody stabilization of the lumbar without the need to mobilize the great vessels from the front of the vertebral bodies. 
         [0022]    It is still yet another objective of the present invention to provide a device for performing surgery on the spine that includes a controlled locking mechanism for securing the surgical device to the bony structure. 
         [0023]    It is still yet another objective of the present invention to provide a device for performing surgery on the spine that includes a cam surface for providing controlled distraction of a disc space. 
         [0024]    Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0025]      FIG. 1  is a perspective view of one embodiment of the present invention; 
           [0026]      FIG. 2  is a partial perspective view of the embodiment shown in  FIG. 1  illustrating the first end thereof; 
           [0027]      FIG. 3  is a perspective view of one embodiment of the guide wire of the present invention; 
           [0028]      FIG. 4  is a perspective view of one embodiment of the distractor member of the present invention; 
           [0029]      FIG. 5  is a partial perspective view of the first end of the distractor member illustrated in  FIG. 4 ; 
           [0030]      FIG. 6  is a partial perspective view of one embodiment of the dynamic tube assembly of the present invention; 
           [0031]      FIG. 7  is a partial perspective view of the dynamic tube assembly shown in  FIG. 6  illustrating the locking member positioned in the locking position; 
           [0032]      FIG. 8  is a partial perspective view of the dynamic tube assembly shown in  FIG. 6  illustrating the locking member positioned in the unlocked position; 
           [0033]      FIG. 9  is a partial perspective view of the dynamic tube assembly shown in  FIG. 6  illustrating the locking member positioned in the unlocked position; 
           [0034]      FIG. 10  is a perspective view of a segment of the thoractic spine and of the guide wire of the present invention being inserted from a lateral approach into the disc space between two adjacent vertebrae; 
           [0035]      FIG. 11  is a perspective view of the distractor member being inserted over the guide wire of  FIG. 10 ; 
           [0036]      FIG. 12  is a perspective view of the dynamic tube assembly being inserted over the distractor member of  FIG. 11 ; 
           [0037]      FIG. 13  is a front view of a portion of the segment of thoractic spine shown in  FIG. 1  illustrating the dynamic tube assembly fully seated into the disc space over the distractor member with the locking member in the unlocked position; 
           [0038]      FIG. 14  is a front view of the segment of the thoractic spine shown in  FIG. 13  illustrating the locking member in the locked position with the distractor member removed; 
           [0039]      FIG. 15  is an end view of one embodiment of the locking dynamic tube assembly; 
           [0040]      FIG. 16  is an end view of one embodiment of the dynamic tube assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0041]    While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0042]    Referring generally to  FIGS. 1-16 , an access assembly  10  constructed and arranged for anterior, lateral anterolateral spinal procedures is illustrated. The present invention provides for the entire surgical procedure to be performed through a relatively small incision, and may be performed in either the thoracic or lumbar spine. In the preferred embodiment, the access assembly  10  comprises a guide wire  12 , a distractor  14 , and a dynamic tube assembly  16  that includes a manually operable locking member  18  for securing the dynamic tube assembly to a bony structure. 
         [0043]    The guide wire  12  is provided for initial insertion into the disc space through a small incision in the patient with the assistance of x-rays, thorascope, image intensifier, direct vision or the like, see  FIG. 10 . For example, for surgery in the thoracic spine, a small incision in the chest cavity of the patient is made from a lateral approach to the thoracic spine. For surgery in the lumbar spine, a small incision may be made in the abdominal wall of the patient. The first end  22  of the guide wire  12  may be inserted with the assistance of a jam shidi needle or other suitable cannula. Alternatively, the guide wire may have sufficient rigidity for direct insertion. The first end  22  of the guide wire  12  may include a particular shape that aids in the insertion such as, but not limited to, a conical point, trocar, spherical or blunt. Once positioned, the central shaft  24  of the guide wire  12  extends between the disc space to outside of the patient to provide a guideway for the distractor member. The second end  26  of the guide wire  12  generally includes a blunt square cut. The guide wire  12  is preferably constructed from a biocompatible metal material such as spring temper stainless steel or nitinol. However, it should be noted that any material having sufficient rigidity to act as a guideway for the distractor member may be utilized without departing from the scope of the invention. 
         [0044]    The distractor  14  is generally an elongated member having a first end  28 , a central portion  30  and a second end  32 . Extending through a central portion of the distractor is a small central aperture  34  sized for cooperation with the outer surface of the center portion of the guide wire  12 . The first end of the distractor preferably includes a tapered end  36  for ease of insertion into the disc space. In a most preferred embodiment, the tapered end includes a frustoconical shape. However, it should be noted that other shapes may be utilized for the tapered end so long as they provide a smooth transition from the outer diameter of the guide wire to the outer diameter of the distractor. Such shapes may include, but should not be limited to, spherical, bullet, pyramid or suitable combinations thereof. A pair of generally flat opposing side surfaces  38  extend along a portion of the length of the center portion  30 . The opposing side surfaces are spaced a predetermined distance apart  40 , which may include a taper, to provide a desired distraction (spacing) and alignment of the vertebrae. The second end  32  of the distractor  14  is provided with a surface  42  suitable for striking with a mallet or the like. The outer surface  44  of the distractor is preferably round to act as a guide surface for the dynamic tube assembly. It should be noted that while the inner and outer surfaces of the distractor member are illustrated as being round, other matched shapes may be utilized without departing from the scope of the invention. 
         [0045]    The dynamic tube assembly  16  includes an outer tube member  50  and an inner lock member  52 . The dynamic tube assembly  16  includes a first end  56 , a center portion  58 , a second end  60 , an outer surface  59  and an inner surface  61 . The first end  56  includes a pair of tab members  62  integrally formed thereto and sized so that they extend a short distance into the disc space adjacent the distractor and between the two opposed surfaces. In this manner, the dynamic tube assembly may be easily traversed to its desired functional position. The second end  60  of the dynamic tube assembly  16  includes a gripping portion  64  for providing counter-rotation force to the dynamic tube assembly during actuation of the lock member  52 . The inner surface of the outer tube member is sized to cooperate with the outer surface of the locking member so as to function as a bearing surface for rotation of the lock member. 
         [0046]    The inner lock member  52  extends through the inner bore  54  of the outer tube member  50  and includes a first end  66 , a center portion (not shown), a second end  70 , an inner bore  54 , and an outer surface  72 . The first end of the lock member preferably includes at least two locks  74  extending beyond and having approximately the same width as the tabs  62 , whereby the lock member may be rotated to align substantially therewith for insertion alongside the distractor. The distal ends of the locks each include at least one barb portion  76  which may include a ramp portion  78 , a rear surface  80  and a pair of side surfaces  82 . The ramp portion  78  provides easy entry through tissue and the like, while the side surfaces  82  may be constructed and arranged to bite and/or cut into the bone during rotation to create a secure engagement. The center portion  68  of the lock member is sized and shaped to cooperate with the inner surface  61  of the outer tube member  50  to allow free rotation therebetween. The second end  70  of the lock member  52  extends through the outer tube member terminating in a second gripping portion  84  which may include a hex  86  of shape constructed and arranged for providing rotational torque to the lock member for engagement or disengagement thereof. The inner bore  54  is sized for cooperation with the outer surface  44  of the distractor member  14 . In this manner, the distractor acts as a guideway for the dynamic tube assembly. The lock member is then rotatable to engage the opposing bony surfaces of the disc space. In this manner, the lock member secures the first end of the dynamic tube assembly into place and releases the distractor member for extraction from the patient while maintaining the adjacent vertebrae in a distracted and aligned position. In some embodiments the lock member may include a shaped cam surface  88  that provides additional controlled distraction of the disc space during rotation thereof. Once the dynamic tube assembly is in place within the patient, the distractor and guide wire may be removed providing an access tunnel to the disc space. The tunnel is provided with sufficient diameter for disc modification or removal as well as the placement of spacers, bone fragments, implants and the like to be passed therethrough to the disc space. Once the operation is completed, rotation of the lock member releases the dynamic tube assembly for removal from the patient.