Abstract:
A novel system and method for use for ensuring appropriate positioning of a cable about bone portions, particularly, vertebral bone, for stabilization of the spine during spinal reconstructive and fusion procedures is disclosed. The system includes cabling uniquely adapted for spinal reconstruction processes, ligature passers and hook passers of varying sizes to facilitate looping of the cable about the spinal/vertebral bone, and a tensioning apparatus which secures the cable at a predetermined tensioned value about the vertebral bone. A novel method for applying a cable about vertebral bone for spinal stabilization is also disclosed.

Description:
BACKGROUND  
         [0001]    1. Field of the Disclosure  
           [0002]    The present invention is directed to orthopaedic reconstruction, and more particularly, to a system and method for spinal reconstruction and stabilization of the cervical, lumbar and thoracic spine.  
           [0003]    2. Discussion of the Prior Art  
           [0004]    Surgical apparatii intended for reconstructive spine surgery and reconstructive spinal procedures in conjunction with bone fusion are known. These apparatii may typically include metal cables and wires which are looped to encircle adjacent bones to hold them together for healing or fusion. The wires may be clamped together to ensure the cable is retained in a looped tensioned condition about the bone portions. Tensioning apparatii are often used to apply a predetermined tension to the cable.  
           [0005]    Known cable systems are subject to several disadvantages which detract from their usefulness in spinal reconstruction surgery. In particular, there are significant complications with the use of metal wires and cables, including breakage of the wire and cable, difficulty in maneuvering about the operative site, cutting into the bone and interference with imaging procedures. The known tensioning apparatii are complicated and difficult to manipulate. Moreover, known systems fail to adequately facilitate the cable looping and securing process, and are deficient in securing a bone graft utilized in the fusion/healing process.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, the present invention is directed to a novel system and method for use for ensuring appropriate positioning of a cable about bone portions, particularly, vertebral bone, for stabilization of the spine during spinal reconstructive and fusion procedures. The system includes cabling uniquely adapted for spinal reconstruction processes, ligature passers and hook passers of varying sizes to facilitate looping of the cable about the spinal/vertebral bone, and a tensioning apparatus which secures the cable at a predetermined tensioned value about the vertebral bone. A novel method for applying a cable about vertebral bone for spinal stabilization is also disclosed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    Preferred embodiments of the disclosure are described in further detail herein with reference to the drawings wherein:  
         [0008]    [0008]FIG. 1 is a side plan view of the tensioning apparatus of the system for orthopaedic spinal stabilization in accordance with the principles of the present disclosure;  
         [0009]    [0009]FIG. 2 is a side cross-sectional view of the tensioning apparatus of FIG. 1;  
         [0010]    [0010]FIG. 3 is an enlarged isolated view of the ratcheting mechanism of the tensioning apparatus;  
         [0011]    [0011]FIG. 4 is a top plan view of the apparatus of FIG. 1;  
         [0012]    [0012]FIG. 5 is an axial plan view of the control knob of the apparatus illustrating the knob&#39;s operating positions;  
         [0013]    [0013]FIGS. 6A and 6B are schematic views illustrating release and locking positions of the apparatus;  
         [0014]    [0014]FIG. 7 is a view similar to the view of FIG. 3, illustrating rotation of the control knob corresponding to a release position of the apparatus;  
         [0015]    [0015]FIG. 8 is an isolated view of a cable engaging pawl of the tensioning apparatus;  
         [0016]    [0016]FIGS. 9 and 10 are top plan views of the tensioning apparatus illustrating the cable engaging pawls in an engaged position and disengaged position, respectively;  
         [0017]    [0017]FIG. 11 is an isolated view of the graduated scale mechanism indicating the degree of tension of the looped cable;  
         [0018]    [0018]FIG. 12 is a side plan view of the hook passer of the system;  
         [0019]    FIGS.  13 A- 13 C are views of the ligature passer of the system;  
         [0020]    FIGS.  14 - 17  are views illustrating the sequence of use of the instruments of the system in accordance with a preferred procedure for spinal stabilization;  
         [0021]    [0021]FIG. 18 is a top plan view illustrating movement of the pawl engaging mechanism during actuation of the movable grip; and  
         [0022]    [0022]FIG. 19 is a view illustrating securement of the looped cable. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]    Referring now to the drawings wherein like references identify similar or like elements throughout the several views, there is illustrated the system for spinal stabilization in accordance with the principles of the present disclosure.  
         [0024]    The following discussion will include a description of each instrument utilized in performing a spinal procedure followed by a description of preferred methods for spinal stabilization utilizing the instrumentation in accordance with the present disclosure.  
         [0025]    In the discussion which follows, the term “proximal”, as is traditional, will refer to the portion of the structure which is closest to the operator, while the term “distal” will refer to the portion which is furthest from the operator.  
         [0026]    The system for spinal stabilization includes several components, namely, a surgical cable, a tensioning apparatus for applying the surgical cable about the spinal bone, and hook and ligature passers utilized to facilitate looping of the cable about the bone. The preferred surgical strand or cable is a radiolucent cable system known under the trademark SecureStrand™ which is available from Surgical Dynamics, Inc. of Norwalk, Conn. This cable is made of braided high strength radiolucent ultra-high molecular weight polyethylene (UHMWPE) fiber. The cable consists of  8  yarns of fiber, each having 120 fibers, and being braided to form a cable about 1 mm in diameter. The cable derives its strength from the unique fibers used to create it. These extended-chain polyethylene fibers are characterized by a high degree of orientation with a minimum of chain folding. The SecureStrand™ cable system avoids many of the potential complications caused by implantation of metal wires and metal cables, including wire/cable breakage, hemorrhage, contusion, laceration and interference with magnetic resonance and x-ray imagery. Furthermore, the cable is sufficiently flexible for looping about bone tissue and may be secured relative to bone tissue through knotting procedures.  
         [0027]    Referring now to FIG. 1, in conjunction with FIGS.  2 - 4 , tensioner apparatus of the system will be discussed. Tensioning apparatus  100  includes a handle  102  and an elongated member  104  extending distally from the handle  102 , and defining a longitudinal axis “a”. Handle  102  includes frame  106  having a stationary grip and a movable grip  108  pivotally mounted within the frame  106  about pivot pin  110 . Movable grip  108  includes pawl  114  which forms part of the ratchet mechanism for tensioning the cable. Pawl  114  pivots about pivot pin  116  and has a coil spring  118  which biases the pawl  114  distally to a normally engaged position corresponding to an operative position of the ratchet mechanism as depicted in FIG. 2. Coil spring  118  is connected to handle  102  through pin  120 .  
         [0028]    An elongated actuating member  122  extends through frame  106  and elongate member  104 . Actuating member  122  includes an inner rod  124  and an outer sleeve  126  coaxially mounted about the rod  124 . A screw  125  received within a corresponding threaded aperture  127  at the distal end of rod  124  engages the distal end of outer sleeve  126  such that the inner rod  124  and outer sleeve  126  move concurrently in the distal direction. Outer sleeve  126  is adapted for rotational movement relative to rod  124  and has control knob  128  coaxially mounted to its proximal end through stationary screw  131 . Outer sleeve  126  includes ratchet teeth  130  which cooperate with pawl  114  of movable grip  108  to move outer sleeve  126 . Outer sleeve  126  further defines a longitudinal slot  132  within the elongate member  104  in which an internal sleeve locking pin  134  is received (FIG. 2).  
         [0029]    As best depicted in FIG. 5, locking knob  128  is rotatable about the longitudinal axis “a” through at least three positions, namely, “release”, “tension” and “lock” positions, to cause rotational movement of the outer sleeve  126  through three corresponding positions. In the “tension” position, which is depicted in FIG. 2, ratchet teeth  130  of outer sleeve  126  are engaged with pawl  114 , thereby permitting the outer sleeve  126  to move upon movement of movable grip  108  to tension the cable. Also in the “tension” position, sleeve locking pin  134  is disposed in longitudinal slot  132  of the outer sleeve  126  such that the locking pin  134  traverses the longitudinal slot  132  during axial movement of outer sleeve. This relationship is shown schematically in FIG. 6A. In the “release” position depicted in the cross-sectional view of FIG. 7, control knob  128  is rotated in a counter-clockwise direction (FIG. 5) to rotate outer sleeve  126 , i.e., outer sleeve  126  is angularly displaced whereby ratchet teeth  130  are disengaged from pawl  114  thereby permitting actuating member  122  to move without restriction in either the proximal direction or distal direction. In the “lock” position, control knob  128  is rotated clockwise with respect to FIG. 5, “¼” turn through an angular displacement of 90°. In this position, internal locking pin  134  is received within a transverse groove  136  extending from longitudinal slot  132  of outer sleeve  126  thereby preventing the outer sleeve  126  from moving axially as depicted in the schematic view of FIG. 6B. Thus, in the “lock” position, the instrument is not capable of being used in a tensioning mode of operation.  
         [0030]    With reference again to FIGS. 2 and 3, the pawl mechanism further includes a ratchet lock  138  disposed within frame  106  of handle  102  adjacent control knob  128 . Ratchet lock  138  moves transversely relative to the longitudinal axis “a” within slot  140  of frame  106  to releasably engage/disengage ratchet teeth  130  of actuating member  122 . Ratchet lock  138  is biased to the engaged position depicted in FIG. 3 by coil spring  142 . Ratchet lock  138  is adapted to releasably lock outer sleeve  126  of actuating member  122  subsequent to each incremental movement of the outer sleeve  126  in a proximal or tensioning direction, i.e., the ratchet lock  138  is displaced downwardly upon engagement of pawl  114  with a crest  130   c  of each respective ratchet tooth whereby upon clearance of the crest  130   c  the ratchet lock  138  engages the leading vertical surface  130   v  of the tooth. Accordingly, when in the “tension” condition of control knob  128  the pawl mechanism releasably incrementally locks outer sleeve  126  actuating member  122  while preventing distal loosening movement thereof. Ratchet lock  138  also provides an audible signal during each “click” of the ratchet teeth to indicate the progression of the tensioning procedure.  
         [0031]    With reference to FIGS. 2, 4 and  8 , apparatus  100  further includes a cable engaging pawl mechanism  144  adjacent its distal end. Cable engaging pawl mechanism  144  includes plate  146  which is operatively connected to outer sleeve  126  of actuating member  122  through screw  148 . Plate  146  moves longitudinally upon longitudinal movement of outer sleeve  126 . A pair of cable engaging pawls  150  are pivotally mounted to plate  146  through pivot screws  152  on opposed sides of elongated member  104 . Each cable engaging pawl  150  is movable about screw  152  between a cable engaging position depicted in FIGS. 4, 8 and  9  and a cable release position. In the engaging position depicted in FIG. 9, the pawls  150  clamp the cable ends “e” against respective vertical surfaces  154  of plate  146 . Each pawl  150  is normally biased to the engaged position through torsional spring  155  which is coaxially mounted about each screw  152 .  
         [0032]    A cable release trigger  156  extending beneath elongate member  104  moves the pair of cable engaging pawls  150  between the cable engaging and release positions. More particularly, release trigger  156  includes a U-shaped portion  158  engageable by the index finger of the user and release rod  160  which extends to plate  146 . Release rod  160  is operatively connected to a pair of cam pins  162  which are received within corresponding slots  164  of plate  146 . Each cam pin  162  traverses its respective slot  164  upon longitudinal movement of release trigger  156  to open and close cable engaging pawls  150 . In particular, upon depressing or proximal movement of release trigger  156 , the cam pins  162  connected to the release rod  160  move proximally within slots  164  to engage pawl  150  to open the pawls  150  to the position depicted in FIG. 10. Release of release trigger  156  permits pawls  150  to return to their normal engaged position under the influence of torsion springs  155 .  
         [0033]    With reference now to FIGS. 3, 4 and  11 , tensioner apparatus  100  further includes a graduated spring scale  170  disposed adjacent control knob  128  to indicate to the user the degree of tension of the cable. Spring scale  170  includes spring  172  and an indicator pin  174  which is operatively connected to the pin  172 . Pin  172  extends through slot  176  of indicator panel  178 . Spring  172  operatively engages the proximal end of outer sleeve  126  of actuating member  122 . When the outer sleeve  122  is displaced rearwardly upon movement of tensioning trigger  108 , spring  172  is compressed accordingly. The degree of compression of spring  172  which is directly related to the forces on actuating member  122  through the tensioned cable is indicated by the location of scale pin  174  relative to the graduated markings on the indicator panel  178 . This permits the surgeon to readily obtain the level of tension of the cable.  
         [0034]    Referring now to FIG. 9, in conjunction with FIG. 1, tensioning apparatus  100  further includes a distal bull nose  180 . Bullnose  180  includes opposed cable receiving grooves  182  (phantom) which receive each cable end “e” prior to passing through the cable pawl mechanism  144 . Apparatus  100  also includes a plastic collar  184  having grooves  186  which receives the extreme free ends of the cable “c”.  
         [0035]    Referring now to FIG. 12, hook passer  200  of the system will be discussed. Hook passer  200  is intended to pass the SecureStrand™ cable about adjacent vertebral bodies. Hook passer  200  includes a hook body  202  defining a general semi-circular shape and having an eye loop  204  at a trailing end and a narrowed blunt entry end  206 . Eye loop  204  is generally elongated and is dimensioned for reception of the looped cable end. During manufacture, eye loop  204  is bent in itself to define an open hook appearance detailed in the Figure.  
         [0036]    With reference now to FIGS.  13 A-C, ligature passer  300  of the system will be discussed. Ligature passer  300  is also intended for looping the cable end with respect to the vertical bodies and includes handle  302  and elongated portion  304  extending distally from the handle  302 . Elongated portion  302  includes an arcuate end portion  306  which is bent between an angle ranging about 70°-110° relative to the axis “a” of the elongated portion. The extreme distal end of the ligature passer includes an eye loop  308  dimensioned for reception of the looped SecureStrand™ cable. The handle  302  includes a knurled portion  308  to facilitate gripping engagement by the user.  
         [0037]    The use of system  100  for spinal stabilization will now be discussed. Subsequent to removal of a portion of the vertebrae and/or removal of an intervertebral disc, the spine is to be stabilized for healing and fusion. A three foot length of SecureStrand™ cable is cut from a cable roll and folded upon itself. With the assistance of hook passer  200  or ligature passer  300 , depending on the preference of the surgeon, the looped end of the cable “c” may be engaged to respective eye loops of the passers, and the passers are manipulated to pass the cable “c” beneath a pair of opposed vertebrae V 1 , V 2 , i.e., the spinous process or adjacent lamina as depicted in FIG. 14.  
         [0038]    Once the looped cable “c” is positioned with respect to the vertebral bone portions V 1 , V 2 , attention is directed to tying the appropriate knot with the cable “c”. In the preferred procedure, a racking hitch is formed in the looped cable end by inwardly twisting the cable loop upon itself to the orientation depicted in FIG. 15. In procedures involving fusion, a bone graft “b” may be placed between the vertebrae. Thereafter, both free ends “e” of the cable “c” are pulled through the racking hitch as depicted in FIG. 16. The bone graft “b” is shown in FIG. 16. Both free ends are advanced in order to close the racking hitch against the vertebral bodies V 1 , V 2 . Thereafter, the free ends of the cable “c” are used to tie a half hitch, as depicted in FIG. 17. The half hitch is advanced to abut the racking hitch to secure the bone graft between the adjacent vertebrae V 1 , V 2 . The half hitch is tightened with moderate hand pressure.  
         [0039]    The procedure is continued by applying tension to each of the cable ends. Tensioner apparatus  100  is introduced into the surgical site. A first free end “e” of the cable “c” is positioned about the bull nose  180  of the apparatus with the cable receiving groove  182  and the second free end “e” is positioned within the opposed groove  182  as depicted in FIG. 9. With reference to the FIG. 10, the cable release trigger is depressed to outwardly displace the cable engaging pawls  150  to permit the cable ends “e” to be passed within the openings defined between the pawls  150  and the vertical surfaces  154  of plate  146 . Thereafter, the extreme ends of the cable “c” are positioned within grooves  186  of holder  184  as also depicted in FIG. 10. Movable grip  108  is actuated to move, through action of the ratchet mechanism, actuating member  122 , plate  146  and cable engaging pawls  150  proximally as depicted in FIG. 18 to tighten the cable ends. During actuation, spring scale  170  is continually monitored to monitor the desired degree of tension to the cable strands. Once the desired level of tension is achieved, control knob  128  is rotated to the “release” position, and the control knob is pushed forwardly. Then, the control knob is rotated to the “lock” position. The cable release trigger is depressed to release the cable from the pawls and the ends of the cable are removed from the plastic holder. As depicted in FIG. 19, a second half hitch opposite to the first half hitch is created to form a square knot. A third half hitch is then formed opposite the second half hitch and advanced to the square knot to secure the cable. Thereafter, the free ends of the cable are cut beyond the knob with, e.g., a cauterizer.  
         [0040]    While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the disclosure, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. For example, the system and method of application can be utilized in other areas of the body including knee, hip elbow etc. . . . to join adjacent bone portions.