Abstract:
An apparatus and a method for performing spondylolisthesis reduction utilizing spinal link implants, the apparatus comprising a jack which is temporarily affixed to the spinal links, where the jack is constructed to provide leverage or fulcrum points such that the vertebrae or sacrum can be moved as required for, proper realignment and to position adjacent link members for connection. The jack comprises a pair of outrigger members connected to a levering member such that each is free to pivot, whereby the relative angle between the members may be altered by movement of the levering member, which is provided with at least one handle to be gripped by the surgeon. Optionally, an outrigger stabilizer member is also provided. The ends of the outrigger members are provided with connector means for temporarily securing the outriggers to the linking members in a secure manner such that any manipulation of the outrigger members is transferred to the spinal link members and thus to the vertebra or sacrum to which they are affixed. With the sacrum and vertebrae properly aligned and positioned, the spinal links are joined to form a rigid structure and the jack is removed.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of medical devices and methods of treatment of spondylolisthesis, and more particularly to the field of such devices and methods for manipulation of adjacent vertebrae or of the lower vertebrae and the sacrum (which in humans is formed of fused vertebrae), whereby the adjacent vertebrae or the vertebrae and sacrum are properly aligned and positioned such that fixation structures can be utilized to secure the adjacent vertebrae or the vertebrae and sacrum in the proper relation. Even more particularly, the invention relates to a mechanical apparatus or jack which can be temporarily attached to spinal implants permanently affixed to both the vertebrae and the sacrum, whereby the surgeon performs the spondylolisthesis reduction by manipulating the jack to properly position the vertebrae and sacrum and then securing the sacrum spinal implant to the vertebral, spinal implant in rigid manner. 
     The invention herein functions with and incorporates portions of the apparatus and method disclosed in my U.S. Pat. No. 6,017,343, issued Jan. 25, 2000, and entitled Apparatus, Method and System for the Treatment of Spinal Conditions and Fixation of Pelvis and Long Bones, the disclosure of which is herein incorporated by reference. The invention will also function with other types of spinal implants and mechanical fixation devices used to create a construct which will secure the adjacent pairs of vertebrae or the sacrum and vertebrae in a fixed, rigid relationship, such as plates or rods. 
     The lumbar vertebrae comprise the five vertebrae positioned below the dorsal vertebrae, and are customarily designated L 1  through L 5 , with L 1  being adjacent the lowermost or twelfth dorsal vertebra and L 5  being adjacent the sacrum. The sacrum is a large, curved, triangular bone having a wide base which articulates from the L 5  vertebra. The anterior surface of the sacrum is generally concave, curving in a pronounced manner from above downward and slightly from side to side. Spondylolisthesis is a condition where adjacent vertebrae, most usually the sacrum and the lower or lumbar vertebrae, are not properly aligned or connected, such that adjacent vertebrae are displaced or the lumbar vertebrae are displaced anteriorly from the upper base of the sacrum. For purposes of this disclosure, the apparatus and method shall be described primarily with reference to spondylolisthesis occurring between the L 5  vertebra and the sacrum, but it is to be expressly understood that the apparatus and method are suitable for manipulation and treatment of any adjacent vertebrae. In a spondylolisthesis reduction, the surgeon properly repositions the vertebrae and sacrum, and then permanently joins the vertebrae and sacrum using mechanical fixation structures. The reduction may require manipulation of the vertebrae and the sacrum in one or more directions, i.e., translation in the anterior/ventral or posterior/dorsal direction, compression or distraction in the longitudinal direction of the vertebral axis, and rotation about the vertebral axis, as well as pivotal flexion of the sacrum in the ventral direction or pivotal extension of the sacrum in the dorsal direction. 
     In my U.S. Pat. No. 6,017,343, spinal implants comprising linking members are disclosed which comprise a central portion joining two end portions, the end portions being apertured to receive a pedicle bolt whereby the link members can be permanently affixed to a vertebra or other bone. The end portions of adjacent link members are aligned to receive a single pedicle bolt and a lock nut, and in this manner pairs of link members can be connected to form a rigid linking structure, where the link members can be affixed to adjacent vertebrae, bones or bone segments in order to create a rigid connecting structure which secures the vertebrae, bones or segments in fixed manner. 
     It is an object of this invention to provide an apparatus, a system and a methodology for the manipulation and fixation of adjacent vertebrae or the lumbar vertebrae and the sacrum for spondylolisthesis reduction, whereby a mechanical manipulator device or jack is provided which allows the surgeon to properly position and secure the vertebrae and sacrum in a relatively quick and straightforward manner. It is a further object to provide such an apparatus and method which enables the surgeon to translate, compress, distract, rotate, flex or extend either or both the vertebrae and the sacrum as required, which is easily connected to and removed from spinal implant link members affixed to the vertebrae and the sacrum, and which functions to retain proper positioning of the vertebrae and sacrum as the surgeon connects the link members of the sacrum to the link members of the vertebrae. It is a further object to provide such an apparatus whose component parts are adjustable to accommodate variation in patient size and to present a variety of angular combinations as required for a particular reduction operation. These and other objects not expressly stated above will be readily apparent from examination of the disclosure to follow. 
     SUMMARY OF THE INVENTION 
     The invention comprises an apparatus and a method for performing spondylolisthesis reduction between adjacent vertebrae and more particularly between the lower vertebrae and the sacrum, where the method utilizes spinal implants, such as spinal link members comprising central portions bridging two apertured end portions, where the end portions of two such link members may be aligned to receive a pedicle bolt, a bolt which is driven into the vertebral body or the sacrum, or a joining bolt which is independent of the vertebral body or sacrum, such that the two link members can be secured to the vertebra or sacrum and to each other by lock nuts to form a rigid structure. The apparatus comprises a jack or manipulator device which is temporarily affixed to transversely mounted central portions of the spinal links, where the jack is constructed to provide leverage or fulcrum points such that the vertebrae or sacrum can be moved as required for proper realignment and to position adjacent link members for connection. The jack apparatus comprises a pair of outrigger members connected to a levering member, where the outrigger members and levering member are provided with plural apertures to receive pivot bolts, in order to allow for variation in the relative angular and linear dispositions of the members. The outrigger members and levering member are connected such that each is free to pivot, whereby the relative angle between the members may be altered by movement of the levering member, which is provided with at least one handle to be gripped by the surgeon. Optionally, an outrigger stabilizer member is also provided for attachment to the outrigger members in similar manner, such that the combination of the outrigger members, levering member and stabilizer member defines a four-sided polygon. The ends of the outrigger members are provided with connector means for temporarily securing the outriggers to the transverse portions of the linking members in a secure manner such that any manipulation of the outrigger members is transferred to the spinal link members and thus to the vertebra or sacrum to which they are affixed. The connector means preferably comprises a hook member which receives the transverse portion of the linking member and a threaded locking ring which can be translated against the transverse portion to secure it against the hook member of the outrigger member. The apparatus is also preferably provided with a position locking member which comprises an elongated body pivotally attached to the levering member, where the position locking member can be temporarily secured to one of the outrigger members to prevent relative movement between the outrigger members and the levering member in order to secure the apparatus in a particular angular configuration. 
     The preferred method comprises the steps of affixing spinal linking members to dorsal side of the base of the sacrum and to the dorsal side of at least the L 5  vertebrae, or to any adjacent vertebrae. The spinal link members affixed to the sacrum preferably comprise one transversely mounted linking member whose central portion defines a transverse bridging member extending laterally across the sacrum and two longitudinally disposed linking members, where one end of each longitudinally disposed linking member is secured to an end of the transversely mounted linking member while the other end of each longitudinally disposed linking member remains free. A pair of longitudinally disposed linking members are each affixed to the L 4  and L 5  vertebra (an L 4  to L 5  fusion being representative of this technique), or to any two adjacent vertebrae that are slipped relative to each other, and a transversely mounted linking member is affixed across the L 4  vertebra and connected to the longitudinally disposed linking members. Another pair of longitudinally disposed linking members are connected to the longitudinally disposed linking members on the L 5  vertebra, with each having a free end. After proper reduction has been achieved, the free ends of the longitudinally disposed linking members on the sacrum and the L 5  vertebra will be connected using a bolt and lock nut. To manipulate the vertebrae and sacrum as required, the outrigger members are joined to the transverse members of the spinal link members on the L 4  vertebra and the sacrum, such that the outrigger members extend in the dorsal direction. The outrigger stabilizer member and levering member are then connected to the outrigger members to define a polygonal configuration, which may be a parallelogram, a trapezoid or other four-sided configurations. The surgeon then manipulates the vertebrae and sacrum as required by pulling on the levering handle and secures the apparatus against angular movement once proper positioning is achieved and the free ends of the longitudinally disposed linking members are aligned. The relative positions of the outrigger members and the levering member and stabilizer member may be changed during the course of the reduction as required to provide proper leveraging and positioning. The free ends of the linking members are then connected to form a rigid, interlocked construct which extends from the L 4  vertebra through the L 5  vertebra to the sacrum. The jack apparatus is then removed from the spinal link members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of the invention, showing the relationship between the levering member, outrigger members, stabilizer member and position locking member. 
     FIG. 2 is a view of the levering member taken from the dorsal direction. 
     FIG. 3 is a view of the stabilizer member taken from the dorsal direction. 
     FIG. 4 is a view of an outrigger member taken along the vertebral axial direction. 
     FIG. 5 is a view of the outrigger member of FIG. 4 taken along the opposite vertebral axial direction. 
     FIG. 6 is a view of the position locking member taken from the dorsal direction. 
     FIG. 7 is a view of the position locking member of FIG. 6 taken from the ventral direction. 
     FIG. 8 is partial view of the outrigger member, showing the connector means for joining the outrigger to the transverse portion of the linking member. 
     FIG. 9 is a view of a pivot bolt member. 
     FIG. 10 is a side view of an alternative embodiment of the invention showing two handles, where the angular relation between the outrigger members and the levering member and stabilizing member have been altered during the reduction process. 
     FIG. 11 is a view of the spinal linking members. 
     FIG. 12 is a lateral view of the spinal linking members as affixed to the sacrum and the vertebrae, prior to reduction. 
     FIG. 13 is a view similar to FIG. 10, where the stabilizing member is not present. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawings, the invention will now be described in detail with regard for the best mode and the preferred embodiment, inclusive as to the apparatus, the system utilizing the apparatus and the spondylolisthesis reduction method and method of use of the apparatus. As shown comprehensively in FIGS. 1 and 10, and with individual components illustrated in FIGS. 2 through 9, the apparatus aspect of the invention is in general a manipulator or jack apparatus  10  comprising a levering member  20 , a pair of outrigger members  30 , and possibly a stabilizer member  40  and a positioning locking member  70 . The outrigger members  30  are connected to the levering member  10  and the stabilizer member  40  in a manner which allows these components to pivot or move angularly relative to each other within a plane containing these components. In general, the combination of the levering member  20 , outrigger members  30  and stabilizer member  40  defines a four-sided polygonal interior space. The combination may define a parallelogram, as shown in FIGS. 1 and 10 where the levering member  20  remains parallel to the stabilizer member  40  and where the outrigger members  30  remain parallel to each other as the angles between the components are changed, or the combination may define any four-sided polygonal shape where one or both sets of opposing components are not connected so as to be in parallel. In this discussion, taking the spine as the starting point, the term dorsal shall be taken to refer to the direction to the rear of the spine during the reduction procedure, i.e., outwardly through the patient&#39;s back, the terms ventral or anterior shall be taken to refer to the direction to the front of the spine, the term proximal shall refer to the axial direction to the top of the spine and the term distal to the axial direction to the bottom of the spine. The term longitudinal shall refer to the direction along the spinal axis and the term transverse shall refer to the direction generally perpendicular to the spinal axis and perpendicular to the dorsal and ventral directions. The apparatus and method shall be more particularly described and illustrated herein with regard to spondylolisthesis occurring between the L 5  vertebra and the sacrum, but it is to be understood that the apparatus and method are equally applicable to spondylolisthesis occurring between any adjacent vertebrae. 
     The levering member  20  comprises an elongated main body  22  having a free distal end  23  and a proximally mounted handle  21 , or as shown in FIGS. 10 and 13 both a proximally mounted handle  21  and a distally mounted handle  21  replacing free distal end  23 , where the main body  22  is provided with a longitudinally extended slot  24  which passes completely through the main body  22  in the dorsal/ventral direction, as seen in FIG.  2 . Preferably the handle, or handles,  21  is disposed angularly from the central axis of the main body  22  in the dorsal direction. A plural number of longitudinally spaced apertures or bores  25  for receiving the pivot bolts  50  are disposed transversely through the main body  22  and slot  24 , with the apertures  25  being internally threaded on one side only to securely receive the threaded end  53  of the pivot bolts  50 , which as shown in FIG. 9 comprise a large head  51 , preferably knurled or scored on the radial surface for better gripping purposes, a non-threaded central body portion  52  and the threaded end  53 , where the non-threaded body  52  resides within the slot  24  when the bolt  50  is inserted completely into the apertures  25 . The main body  22  may be circular in cross-section as shown and the distal end  23  may have a hooked configuration as shown. 
     The stabilizer member  40  comprises a main body  41  which also has a longitudinally extending slot  42  passing completely through the main body  41  in the dorsal/ventral direction, as seen in FIG. 3. A plural number of longitudinally spaced apertures or bores  43  for receiving the pivot bolts  50  are disposed transversely through the main body  41  and slot  42 , with the apertures  43  being internally threaded on one side only to securely receive the threaded end  53  of the pivot bolts  50 . Preferably the apertures  43  in the stabilizer member  40  and the apertures  25  in the levering member  20  are of the same number and identically spaced. 
     The outrigger members  30 , shown in dorsal and proximal views in FIGS. 4 and 5, each comprises a main body  31 , which is generally rectangular in cross-section, an angled dorsal end  32 , and connector means  33  on the ventral end. The main body  31  is provided with transversely extending apertures  37 , non-threaded, at spaced intervals. The apertures  37  receive the body portion  52  of the pivot bolts  50 . The main body  31  is sized to fit within the levering member slot  24  and the stabilizer member slot  42 , such that the levering member  20  and the stabilizer member  40  can be positioned at various points on the outrigger members  30  by aligning the corresponding apertures  25  or  43  with the outrigger apertures  37  and fastening a pivot bolt  50 . The connector means  33  defines the mechanism for releasably securing the outrigger member  30  to the transverse bridging member  95  of the spine link members  90 , and as best shown in FIG. 8 comprises in combination an externally threaded segment  34  adjacent the main body  31 , a ventrally disposed hook member  35  which extends in the longitudinal direction, and a locking ring member  36  comprising an internally threaded nut  61  to mate with the externally threaded segment  34 , a collar member  62  joined to the nut  61  in a manner that allows the collar  62  to rotate independently of the nut  61 , and a longitudinally extending flange member  63 . With the transverse bridging member  95  of the spine link member  90 , which is generally rectangular in cross-section, disposed between the hook member  35  and the collar  62 , rotation of the nut  61  relative to the outrigger member  30  in the proper direction causes the connector means  33  to advance to secure the transverse bridging member  95  in the rectangular space defined by the combination of the hook member  35 , collar  62  and flange  63 , whereby movement by the surgeon of the outrigger member  30  in any direction is transferred directly to the spine link member  90 . Disconnection of the outrigger member  30  from the spine link member  90  is accomplished by reversal of these steps. 
     The jack  10  is preferably provided with a position locking member  70 , shown in the opposing longitudinal views in FIGS. 6 and 7, which allows the surgeon to lock the levering member  20 , outrigger members  30  and stabilizing member  40  in a particular angular configuration relative to tension in the ventral direction. The position locking member  70  comprises an insertion body  71 , generally rectangular in cross-section, an externally threaded end  72  and a non-threaded aperture  75  positioned in the insertion body  71 . The insertion body is sized to fit within the levering member slot  24 , such that the aperture  75  can be aligned with an aperture  25  in the levering member and secured with a pivot bolt  50 , whereby the position locking member  70  can pivot in the longitudinal direction relative to the levering member  20 . A slot  73  is provided in the threaded end  72  facing to the distal direction, which is sized to receive the angled end  32  of the distal outrigger member  30 , as shown in FIGS. 1 and 10. An internally threaded lock nut  74  is disposed on the threaded end  72 , such that the locking nut  74  can be rotated to abut against the angled end  32  of the outrigger member  30 , thereby preventing angular movement between the levering member  20 , outrigger members  30  and stabilizer member  40  as a result of tension in the ventral direction. 
     The jack  10  is preferably utilized in conjunction with spine link members  90 , which are shown in FIGS. 11 and 12, the structure, function and method of affixation of these link members  90  being more fully disclosed and described in U.S. Pat. No. 6,017,343, incorporated by reference herein. Alternatively, other spinal implant or structural linking members affixed to the sacrum  100  and vertebrae  110  may be used as substitutes for the spine link members  90  shown in the figures, such as rods or plates, provided means for temporary connection of the connector means  33  of the outrigger members  30  in a manner whereby movement of the outriggers  30  is transferred to the linking members is provided. The link members  90  comprise a central portion  91  joining two ends  92 , the ends having relatively large circular apertures  93  to receive pedicle bolts  98  and lock nuts  99 . At least one surface of the ends  92  is preferably provided with a mechanical interlocking or friction surface  94 , which may comprise a series of radially extending ridges, such that relative rotation between the end  92  of one link member  90  and the aligned and abutting end  92  of a second link member  90  is hindered or precluded. The length of the central portion  91  will vary in order to achieve proper alignment of the apertures  93  of interconnected link members  90 , with the longest central portion  91  defining a transverse bridging member  95  for a link member  90  which is mounted to extend transversely on either the base  101  of the sacrum  100  or one of the lumbar vertebrae  110 . To affix a link member  90  to either the sacrum  100  or a vertebra  110 , or to affix a link member  90  between two adjacent vertebrae  110  spanning the intervertebral disks  104 , pedicle bolts  98  are securely implanted in the bone using known methodology, and the link members  90  are placed onto the pedicle bolts  98  and secured using lock nuts  74 . 
     For the preferred methodology of the invention, a pair of link members  90  are positioned to extend generally longitudinally to connect the L 4  vertebra  104  and the L 5  vertebra  105 . A transversely disposed link member  90  is positioned with its transverse bridging member  95  extending across the L 4  vertebra  104  and with its ends  92  aligned with the distal ends  92  of the longitudinally disposed link members  90 , and the three link members  90  are secured with a pair of lock nuts  99 . Another pair of link members  90  is interconnected and locked to the proximal ends  92  of the longitudinally disposed link members  90  spanning the vertebrae  110 , with the proximal ends  92  of these link members  90  extending away from the L 5  vertebra  105  toward the sacrum  100 . Correspondingly, a transversely disposed link member  90  is placed across the base  101  of the sacrum  100 , and the proximal ends  92  of a pair of longitudinally disposed link members  90  are secured to the ends  92  of the transversely extending link member  90 . The distal ends  92  of the longitudinally extending link members  90  extend away from the sacrum  100  toward the L 5  vertebra  105 . In this manner, the non-connected ends  92  of the link members  90  mounted onto the L 5  vertebra  105  and the sacrum  100  can be joined to each other with an independent joining bolt member  97  and lock nut  99  after the spondylolisthesis reduction has been performed, creating a rigid structure comprising eight link members  90  joining and immobilizing the L 4  vertebra  104 , the L 5  vertebra  105  and the sacrum  100 . 
     Once the spine link members  90  are properly positioned and affixed in secure manner, the outrigger members  30  are affixed to the transverse bridging members  95  of the transversely disposed link members  90 , with the connector means  33  centrally disposed along the transverse bridging members  95 . Distraction, flexion or extension of the sacrum  100  can be accomplished by securing either the stabilizer member  40  or the levering member  20  to the outrigger members  30  and pivoting the proximal outrigger member  30  using the stabilizer member  40  or levering member  20  to provide a fulcrum point. The location of the intersection points between the stabilizer member  40  or levering member  20  and the outrigger members  30  affects the angular and linear relationships between the components, and is determined by patient physical factors and the manipulations necessary to be performed by the surgeon. Where the stabilizer member  40  is first utilized, the levering member  20  is then secured to the outrigger members  30  after the first stage of manipulations has been accomplished, with the chosen intersection points for the necessary angular and linear relationships again being determined by patient factors. Translation is accomplished by pulling the levering member handle  21 , utilizing the sacrum  100  as a fulcrum such that the vertebrae  110  are moved in the dorsal direction. As manipulation progresses, it may be necessary to disconnect and reconnect the levering member  20  or the stabilizer member  40 , or both, from the outrigger members  30  in order to adjust the angular and linear relationships between the components to provide for the proper manipulation. To overcome ligamentum taxis, to allow for adjustment of the position of the spine link members  90 , or to secure the jack  10  in the final orientation for connection of the sacrum link members  90  to the L 5  vertebra link members  90 , the position locking member  70  is utilized. When the reduction has been accomplished such that the positional relationship between the vertebrae  110  and the sacrum  100  is as desired, the non-connected ends  92  of the link members  90  mounted onto the L 5  vertebra  105  and the sacrum  100  will be properly aligned and are now joined to each other with an independent joining bolt member  97  and lock nut  99 . With the vertebrae  110  and sacrum  100  now rigidly fixed by the link member  90  construct, the connector means  33  are loosened and the jack  10  is removed from the spine link members  90 . 
     It is understood that equivalents and substitutions to certain elements set forth above may be obvious to those skilled in the art, and therefore the true scope and definition of the invention to be as set forth in the following claims.