Abstract:
The present invention includes a method of securing a spinal rod to an anchoring device, including releasably securing a locking cap to a distal end of an insertion instrument, the instrument having an outer tubular body, a rod persuader, and a locking shaft, each of the tubular body, rod persuader and locking shaft having proximal and distal ends and positioned coaxial with one another; positioning the distal end of the insertion instrument, and locking cap, into operative engagement with the spinal rod; engaging the anchoring device with the distal end of the tubular body; rotating the proximal end of the rod persuader to longitudinally advance the locking cap and spinal rod distally towards the anchoring device, the proximal end and the distal end of the rod persuader being rotatable relative to one another; and after the locking cap is advanced, rotating the locking shaft to rotate the locking cap thereby.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 11/899,503, filed on Sep. 5, 2007, which is a divisional of U.S. application Ser. No. 10/441,764, filed on May 20, 2003, now U.S. Pat. No. 7,278,995, which claims the benefit of the filing date of U.S. Provisional Application No. 60/385,994 filed on Jun. 4, 2002, the disclosures of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a surgical instrument and, more particularly, to an apparatus and method for securing a spinal rod system. 
     The spinal column is a complex system of bones and connective tissue which protects critical elements of the nervous system. Despite these complexities, the spine is a highly flexible structure, capable of a high degree of curvature and twist through a wide range of motion. 
     For many years, orthopedic surgeons have attempted to correct spinal irregularities and restore stability to traumatized areas of the spine through immobilization. Over the past ten years, spinal implant systems have been developed to achieve immobilization. Such systems often include spinal instrumentation having connective structures such as elongated rods which are placed on opposite sides of the portion of the spinal column intended to be immobilized. Screws and hooks are commonly utilized to facilitate segmental attachment of such connective structures to the posterior surfaces of the spinal laminae, through the pedicles, and into the vertebral bodies. These components provide the necessary stability both in tension and compression to achieve immobilization. 
     Accordingly, the subject disclosure is directed to an apparatus to facilitate securement of the screws and hooks to the connective structures of a spinal stabilization system. Specifically, the apparatus is used in connection with a spinal rod system and assists in positioning the rods of the system relative to the spinal screws and securing the system at a desired orientation. 
     SUMMARY OF THE INVENTION 
     An apparatus for facilitating securing of a spinal rod within an anchoring device having an open end and a locking cap for securing the spinal rod within the open end, includes:
         a handle   an elongated body connected to the handle and defining a longitudinal axis;   a pair of jaws mountable to the elongated body, the jaws adapted for relative movement between an open displaced position and a closed position, the jaws defining structure for engaging the anchoring device when in the closed position thereof;   a rod persuader at least partially disposed within the elongated body and adapted for longitudinal movement therein, the rod persuader advanceable within the elongated body to operatively engage the spinal rod to approximate the spinal rod with respect to the open end of the anchoring device; and   a locking shaft disposed within the elongated body and operatively engageable with the locking cap of the anchoring device, the locking shaft movable relative to the elongated body to move the locking cap to a secured position thereof within the anchoring device to secure the spinal rod relative to the anchoring device.       

     The rod persuader includes mounting structure for releasably mounting the locking cap such that the locking cap engages the spinal rod upon advancing movement of the rod persuader. The locking shaft may be operatively engageable with the rod persuader upon movement of the rod persuader to an advanced position thereof wherein movement of the locking shaft causes corresponding movement of the locking cap releasably engaged to the rod persuader. The locking shaft may be adapted for rotational movement to move the locking cap of the anchoring device to the secured position thereof. 
     The jaws each include detents for releasably engaging corresponding structure of the anchoring device. The jaws may be spring-biased to the open position thereof. One of the jaws is preferably a stationary jaw in fixed relation to the elongated body and the other of the jaws is a movable jaw. A manually engageable lever is connected to the movable jaw. The lever may be movable to cause corresponding movement of the movable jaw between the open and closed position of the jaws. A lockout mechanism including a lockout arm engageable with the manually engageable lever may selectively secure the movable jaw in the closed position. 
     The locking shaft is adapted for rotational movement to move the locking cap to the secured position thereof. The locking shaft is adapted to operatively engage the locking cap upon advancing movement of the rod persuader a predetermined distance thereof whereby rotational movement of the locking shaft causes corresponding rotational movement of the locking cap. The locking shaft define a central lumen therethrough for reception of the rod persuader and the rod persuader is adapted for longitudinal movement within the locking shaft. 
     The locking shaft includes a keyed recess dimensioned to receive corresponding keyed structured of the rod persuader whereby rotational movement of the locking shaft causes corresponding rotational movement of the locking cap. The rod persuader may include a proximal rod portion and a distal rod portion. The proximal rod portion is adapted to rotate relative to the distal rod portion adapted for relative rotational movement. With this arrangement, the distal rod portion includes the keyed structure. 
     Alternatively, the rod persuader may be operatively engageable with the locking shaft such that upon movement of the rod persuader to the predetermined position thereof rotational movement of the rod persuader causes corresponding rotational movement of the locking shaft and locking cap to the secured position thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present invention and, together with the general description given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention. 
         FIG. 1  is a front perspective view of the apparatus for securing a spinal rod system in accordance with the present invention; 
         FIG. 1A  is an enlarged view of the area  1 A- 1 A of  FIG. 1 ; 
         FIG. 2  is an exploded view of the apparatus with parts separated; 
         FIG. 3  is a side elevational view of the apparatus of  FIG. 2 ; 
         FIG. 4  is a rear perspective view of the apparatus of  FIG. 1 ; 
         FIG. 5  is a side cross-sectional view of the apparatus with the jaw mechanism closed; 
         FIG. 5A  is a cross-sectional view taken along the lines  5 A- 5 A of  FIG. 5 ; 
         FIG. 6  is an exploded view of the locking shaft of the apparatus; 
         FIG. 7  is a cross-sectional view of a handle assembly of the locking shaft; 
         FIG. 8  is a perspective view of a handle housing of the handle assembly shown in  FIG. 7 ; 
         FIG. 9  is an axial view of the tubular body; 
         FIG. 10  is a perspective view of the rod persuader of the apparatus; 
         FIG. 11  is a perspective view of a cap spin of the rod persuader; 
         FIG. 12  is an exploded view with parts separated of the rod persuader; 
         FIG. 13  is a cross-sectional view of the cap spin; 
         FIG. 14  is an exploded view of a pedicle screw; 
         FIG. 15  is an enlarged perspective view of area “X” of  FIG. 14 , illustrating the head of the pedicle screw; 
         FIG. 16  is an exploded view of a cap of the pedicle screw as seen from below; 
         FIG. 17  is a perspective view of the assembled cap of the pedicle screw as seen from below; 
         FIG. 18  is a cross-sectional view of the apparatus with the jaw mechanism in the open position; 
         FIGS. 19A-19B  are cross-sectional views of the apparatus with the rod persuader advanced for mounting the locking cap of the spinal rod system; 
         FIG. 20  is a side cross-sectional view of the apparatus of  FIG. 1 , shown mounted on to the head of the pedicle screw; 
         FIG. 21  is an enlarged view of area “ 21 ” of  FIG. 21 ; 
         FIG. 22  is a cross-sectional view of the apparatus taken at “ 22 - 22 ” of  FIG. 20 ; 
         FIG. 23  is a side cross-sectional view of the apparatus illustrating the positioning of a rod in the head of the pedicle screw; 
         FIG. 24  is an enlarged view of area “ 24 ” of  FIG. 23 ; 
         FIG. 25  is a side cross-sectional view of the apparatus illustrating the locking of the cap of the pedicle screw to the head of the pedicle screw; 
         FIG. 26  is an enlarged view of area “ 26 ” of  FIG. 25 ; 
         FIGS. 27A-27B  illustrate release of the rod persuader from the locking cap of the pedicle screw; 
         FIG. 27C  is an enlarged view illustrating the opening of the jaw mechanism; and 
         FIG. 28  is a perspective view of a pair of pedicle screws secured to a vertebral body and having a rod extending through the pair of pedicle screws. 
     
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments of the apparatus for securing a spinal rod system will now be described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. In the drawings and in the description which follows, the term “proximal,” as is traditional, will refer to the end of the apparatus closest to the operator, while the term “distal” will refer to the end of the device or instrument furthest from the operator. 
     Apparatus  100  is adapted for use with a spinal rod system to facilitate manipulation and securement of the rod system relative to the spine of the patient. It is envisioned that apparatus  100  may be suited for a variety of spinal rod systems which incorporate an open ended pedicle screw and a locking member positionable in the screw end for locking engagement with the rod or the screw head. Apparatus  100  is particularly adapted for use with the spinal rod system disclosed in commonly assigned application Ser. No. 09/487,942, filed Jan. 19, 2000, the contents of which are incorporated herein by reference. The spinal rod system disclosed in the &#39;942 application will be described in further detail hereinbelow. 
     Referring initially to  FIG. 1 , the apparatus in accordance with the present disclosure, is shown generally as reference numeral  100 . Apparatus  100  includes several mechanisms, namely, rod persuader  102 , locking shaft  104  and jaw mechanism  106 . Generally, rod persuader  102  functions in engaging a spinal rod of a spinal rod system and manipulating the rod into an open recess of the screw head. Locking shaft  104  secures the locking member of the spinal system within the open pedicle screw head. Jaw mechanism  106  mounts to the pedicle screw to stabilize the apparatus  100  relative to the spinal rod system during operation of the apparatus  100 . 
     With reference to  FIGS. 2-5  in conjunction with  FIG. 1 , jaw mechanism  106  will be initially discussed. In  FIGS. 3-5 , rod persuader  102  is shown removed from the apparatus  100 . Jaw mechanism  106  includes tubular body  108  coaxially arranged about both rod persuader  102  and locking shaft  104 . Tubular body  108  defines an enlarged flange  110  at its proximal end and collar  112  coaxially mounted about the tubular body  108  adjacent the flange  110 . Tubular body  108  has fixed jaw  112  and movable jaw  114  pivotally mounted to the fixed jaw  112 . Fixed jaw  112  includes proximal tubular sleeve  116  which is received within the lumen of tubular body  108  and a pair of spaced apart side walls  118  extending from the tubular sleeve  116 . Fixed jaw member  112  has a region of reduced thickness and includes a tooth  120  projecting from the surface thereof. Tooth  120  defines an elongated circle or racetrack-shaped configuration having a pair of flattened opposed sides; however, it is envisioned that tooth  120  can take any shape and/or configuration. 
     Movable jaw  114  is pivotally mounted to fixed jaw  112  through pivot pin  122  extending through corresponding pivot holes  124 ,  126  of the movable jaw  114  and fixed jaw  112 , respectively. Movable jaw  114  defines a clevis  128  at its proximal end. Clevis  128  has a through bore  130  for receiving connecting pin  132 . Movable jaw  114  further defines tooth  134  at its distal end in diametrical opposed relation to tooth  120  of movable jaw  114 . Tooth  134  is substantially identical in configuration to tooth  120  of fixed jaw  112 . Tooth  134  is best depicted in  FIG. 1A . 
     With continued reference to  FIGS. 2-5 , jaw mechanism  106  further includes lever  136  which is adapted for pivotal movement to cause corresponding pivotal movement of movable jaw  114 . Lever  136  defines a distal region  138  which is received within side walls  118  of fixed jaw  112 . Distal region  138  defines a through hole  140  which receives connection pin  132  to connect lever  136  to movable jaw  114 . Distal region  138  further includes a proximal through hole  142  which receives a pivot pin  144  extending through pivot holes  146  of stationary or fixed jaw  112 . Lever  136  pivots about pivot pin  144  to move movable jaw  114  between the open and closed positions. 
     With continued reference to  FIGS. 3-5  in conjunction with  FIG. 2 , apparatus  100  further includes contoured handle  148 . Handle  148  defines a semi-circular inner surface  150  correspondingly dimensioned to cooperate with the outer surface of tubular body  108 . Handle  148  includes a pair of spaced apart walls  152  extending from circular inner surface  150 . Walls  152  include a first pair of holes  154  which receive pin  156 . Pin  156  is accommodated within an arcuate recess  158  formed in an outer surface  110  of the tubular body to thereby axially and rotatably fix tubular body  108  relative to handle  148 . 
     Handle  148  further includes rack  160  pivotally connected to handle  148  through pivot pin  162 . Rack  162  has a plurality of ratchet teeth  164  adapted to cooperate with proximal tooth  166  of lever  136  to selectively secure the lever  136  and thus move movable jaw  114  at desired positions between the open and closed positions thereof. 
     As best depicted in  FIGS. 2 and 5 , apparatus  100  further includes a leaf spring  168  connected to the outer surface of tubular body  108  by fasteners  170 . Leaf spring  168  includes resilient proximal and distal free ends  172 ,  174 . Proximal and distal free ends  172 ,  174  are adapted to engage respective recesses  176 ,  178  formed in rack  160  and lever  136 . Accordingly, with this arrangement, leaf spring  168  functions to both bias the rack  160  into engagement with lever  136  and bias lever  136  towards a position corresponding to a closed position of movable jaw  114 . 
     Referring now to  FIGS. 6-8 , in conjunction with  FIGS. 2 and 5 , locking shaft  104  will now be discussed. Locking shaft  104  includes several components operatively connected to each other, namely, from proximal to distal, handle  180 , connecting sleeve  182  partially disposed within the handle  180 , main body  184  and socket  186  connected to the main body  184 . Handle  180  has a cylindrical housing  188  and a pair of diametrically opposed handles  190  ( FIG. 6 ) extending radially from the housing  188 . Handle assembly  180  includes through bore  191  extending centrally therethrough and an annular rim  192  integrally formed in a distal surface thereof. Preferably, annular rim  192  is spaced a distance from a terminal edge of the distal surface of housing  188 . Housing  188  further includes an off-axis through axial bore  194 . 
     A dowel  196  is received within axial bore  194  and projects from the distal surface of housing  188  for reception within a recess  198  defined in the proximal surface or flange  110  of tubular body  108 .  FIG. 9  is an axial view of the configuration of recess  198  of tubular body  108 . As shown, the recess  198  extends through an arc of about 45 degrees relative to the axis of the tubular body. Thus, handle  180  is capable of rotation relative to the tubular body  108  through an angle equal to the arc of recess  198  of flange  110 , i.e., 45 degrees. Other angular recesses are envisioned as well. Bearing  200  is provided to facilitate rotational movement of handle  180  ( FIG. 7 ). 
     Connecting sleeve  182  of locking shaft  104  is mounted about the proximal end of main body  184  and secured thereto via an interference fit or other conventional means. Connecting sleeve  182  is securely mounted within bore  191  of handle  180  and defines an internal thread  202  ( FIG. 5 ). Socket  186  of locking shaft  104  is partially mounted about main body  184 . Socket  186  defines an internal opening or keyed structure  205  having a racetrack configuration as depicted in the cross-sectional view of  FIG. 5A . 
     Referring now to  FIGS. 10-13 , in conjunction with  FIGS. 1-2 , rod persuader  102  will be discussed in detail. Rod persuader  102  includes rod shaft  204  having handle  206  mounted at its proximal end and cap spin  208  coupled to its distal end. Rod shaft  204  includes a helical thread  210  adjacent its proximal end. Helical thread  210  is adapted to engage internal helical thread  202  of connecting sleeve  182  whereby rotational movement of the rod shaft  204  causes the shaft  204  to axially translate. Cap spin  208  includes a shaped tip  212  for engaging a rear end of a locking cap of the spinal rod system as will be discussed. As seen in  FIG. 11 , shaped tip  212  has a torx configuration, however, alternative configurations may also be utilized to facilitate axial rotation of the locking cap, such as, for example, cruciform, polygonal, hexagonal, etc. In addition, cap spin  208  includes a pair of opposed planar surfaces  214  to define a cross-section of the cap spin  208  which corresponds for reception within keyed opening  202  of socket  186  upon advancement of rod shaft  204  a predetermined distance. 
     With reference to  FIG. 12 , handle  206  includes a through bore  216  sized and shaped to receive the proximal end of rod shaft  204  therein. Preferably, handle  206  includes a threaded opening  218  which is formed transverse to bore  216  and receives a lock screw  220  for engaging the outer surface of rod shaft  204  and thus prevents handle  206  from separating from rod shaft  204 . Cap spin  208  is rotatably mounted to rod shaft  204  through a slip fit connection effected by circumferential recess  222  of the cap spin  208  and slip pin or bearing  224  extended through a bore in rod shaft  204  and received within the recess  222 . 
     Referring now to  FIGS. 14-17 , the spinal rod system intended for use with instrument  100  is illustrated in detail. As discussed hereinabove, this system is disclosed in commonly assigned application Ser. No. 09/487,942. Spinal rod system  400  includes an elongated spinal rod  402  having a circular cross-section and a substantially smooth outer surface finish. As illustrated, anchoring devices in the form of bone screws  404  are provided for securing spinal rod  402  to the spine during a spinal stabilization procedure. 
     With continuing reference to  FIGS. 14-17 , and in particular to  FIGS. 14 and 15 , bone screw  404  includes a head portion  406  defining a horizontal and a vertical axis. A shank portion  408  depends from head portion  406  and a threaded portion  410  having a helical thread  412  extending about the outer periphery depends from shank portion  408 . Helical thread  412  is particularly adapted to securely engage the vertebral bodies of the spine. Head portion  406  defines a substantially U-shaped channel  414 , formed along the horizontal axis thereof, for receiving spinal rod  402 . In particular, U-shaped channel  414  is defined by the interior surfaces of side walls  416  and  418  and curved lower wall  420 , which extends therebetween. Head portion  406  further includes an elongated slot  423  formed in each side wall  416 ,  418 . It is envisioned that slots  423  are configured and adapted to receive tooth  120  of fixed jaw member  122  and tooth  146  of movable jaw member  124 . 
     Bone screw  404  includes a locking cap  430  having an upper portion  432  and a lower portion  434 . Upper portion  432  includes a substantially cylindrical cap body  436  defining an axial reception port  438  for receiving and cooperating with shaped tip  212  of cap spin  208  of rod persuader  102 . Upper portion  432  further includes a pair of circumferentially opposed arcuate engagement flanges  440 ,  442  which extend radially outward from cap body  436 . Engagement flanges  440 ,  442  include oppositely inclined, radially inward sloping, camming surfaces for cooperating with a corresponding complimentary inner opposed arcuate engagement slot  422 ,  424  formed in opposed side walls  416 ,  418  of head portion  406 . Flanges  440 ,  442  of locking cap  430  become engaged in corresponding slots  422 ,  424  upon rotation of upper portion  432  of locking cap  430  relative to head portion  406  of bone screw  404 . 
     Lower portion  434  of locking cap  430  is configured and adapted for cooperative reception within U-shaped channel  414  of head portion  406  and is adapted to engage spinal rod  402  extending through U-shaped channel  414 . More particularly, lower portion  434  has a curved exterior surface which compliments the interior curvature of side walls  416 ,  418  of had portion  406 . Lower portion  434  of locking cap  430  is provided with a hemi-cylindrical channel  444  formed in an undersurface thereof for engaging and cooperating with spinal rod  402  upon loading of locking cap  430  in U-shaped channel  414 . Lower portion  434  includes a radially extending flange  446  which aides in the alignment and positioning of lower portion  434  with respect to spinal rod  402 . 
     As been seen in  FIG. 16 , the lower surface of upper portion  432  of locking cap  430  includes a recessed seating area  448  and an associated axial reception bore  450 . Recessed seating area  448  is configured and dimensioned to accommodate lower portion  434 , while reception bore  450  is configured and dimensioned to receive and engage an axial post  452  which projects from an upper surface  454  of lower portion  434  of locking cap  430 . The interaction of axial post  454  and axial reception bore  450  facilitates relative rotational movement of upper portion  432  relative to lower portion  434  when locking cap  430  is loaded into and locked in head portion  406  of bone screw  404  during a spinal stabilization procedure. 
     Use of a two-part locking cap enables a surgeon to load locking cap  430  into U-shaped channel  414  and properly position lower portion  434  against spinal rod  402  so as to ensure a tight engagement between hemi-cylindrical channel  444  and the cylindrical surface of the spinal rod. Thereafter, upper portion  432  may be rotated into a locked position relative to lower portion  434 . 
     During a spinal stabilization procedure, bone screws  404  are first implanted into the vertebral bodies of the spine and spinal rods  402  are then fitted into U-shaped channels  414  of each bone screw  404 . Once bone screws  404  are in place and spinal rod  402  seated within U-shaped channels  414 , locking caps  430  are loaded into head portion  406 . At such a time, hemi-cylindrical channel  444  of lower portion  434  will engage the cylindrical surface of spinal rod  402  and be maintained in a fixed axial orientation with respect to spinal rod  402  due to the mating relationship between lower portion  434  and U-shaped channel  444 . 
     Locking cap  430  is preferably loaded in such a manner so that the radially outward extending engagement flanges  440 ,  442  of upper portion  432  are parallel to the axis of spinal rod  402 . Once upper portion  432  of locking cap  430  has been properly oriented with respect to head portion  406 , with radially extending flange  446  aligned with spinal rod  402 , upper portion  432  is rotated in a clockwise direction relative to lower portion  434  of locking cap  430  using an appropriate rotational tool, e.g., apparatus  100 . Thereupon, arcuate engagement flanges  440 ,  442  of upper portion  432  engage corresponding engagement slots  422 ,  424  to drive the locking cap  430  into engagement with the spinal rod  402 . Once rotated into a locked position, lower portion  434  of locking cap  430  is seated within recesses seating area  448  defined in the bottom surface of upper portion  432  of locking cap  430 . At such a time, the position of head portion  406  of bone screw  404  is fixed with respect to the longitudinal axis of spinal rod  402 . As appreciated, locking cap  430  rotates through approximately 45 degree arc to assume the secured position thereof. 
     Turning now to  FIG. 18 , use of a rod apparatus  100  in conjunction with spinal stabilization system  400  will be shown and described. Initially, with reference to  FIG. 18 , jaw mechanism  106  of apparatus  100  is moved from the closed position of  FIG. 5  to the opened position of  FIG. 18 . In order to open jaw assembly  106 , the surgeon manipulates rack  160  in a direction “A 1 ,” to overcome the spring bias of proximal free end  172  of leaf spring  168  acting on planar surface of rack  160  to thereby disengage tooth  166  of lever  136  from teeth  164  of rack  160 . With proximal end  172  of lever  168  disengaged, lever  136  is automatically pivoted about pivot pin  144  by a spring force acting in a direction “B” on recess  208  by distal free end  174  of leaf spring  168 , thereby moving lever  136  away from tubular body  108  and causing movable jaw  114  to pivot to the open position depicted in  FIG. 18 . It is appreciated that lever  136  does not need to be spring biased to perform the operation. 
     Referring now to  FIGS. 19A and 19B , attention is directed to mounting locking cap  430  of spinal rod system  400  onto rod persuader  102 . Rod persuader  102  is introduced within locking shaft  104  and tubular body  108 , and advanced via rotation (in the direction D 1 ) until cap spin  208  projects distally beyond socket head  186  of locking shaft  106  and within jaw mechanism  106 . Locking cap  430  is loaded onto shaped tip  212  of cap spin  208  with reception port  438  receiving the tip  212  in frictional relation therewith. Once locking cap  430  is mounted, rod persuader  102  is retracted by rotating handle  206  in a counterclockwise direction to withdraw locking cap  430 . It is noted that in the withdrawn position of locking cap  430 , cap body  436  is received within the arcuate recesses of the jaw mechanism while flanges  440 ,  442  of the locking cap  430  extend through the linear spaces defined between fixed and movable jaws  112 ,  114 . Thus, locking cap  430  is in a fixed angular position within jaw mechanism  106 . It is also appreciated that apparatus  100  may be pre-loaded with a locking cap  430  thereby obviating the aforementioned loading step. 
     With bone screw  404  secured into a vertebrae “V” and spinal rod  402  positioned generally adjacent U-shaped channel  414  of bone screw  404 , jaw mechanism  106  is coupled to head portion  406  of bone screw  404 . In particular, lever  136  is moved toward handle  148  to cause pivotal movement of movable jaw  114  to the closed position depicted in  FIGS. 20 and 21 . In the closed position, teeth  120 ,  134  of fixed and movable jaws  112 ,  114  are received within correspondingly dimensioned slots  423  of screw head portion  406 . Jaw assembly  106  is locked onto head portion  406  by the ratcheting engagement of teeth  164  of rack  160  with tooth of lever  136 . 
     Rod persuader  102  is then rotated in a direction “D 1 ,” wherein helical threads  210  of rod shaft  204  engage internal threads  196  of connecting sleeve  182  to thereby distally displace rod shaft  204 . During distal movement of rod shaft  204 , locking cap  430  mounted to cap spin  286  of rod shaft  204  engages spinal shaft  402  to drive spinal shaft  402  in direction “E 1 ,” i.e., into U-shaped channel  414  of bone screw  404 . It is appreciated that during rotation of rod shaft  204  cap spin  208  does not rotate due to the slip fit connection depicted in  FIG. 13  and discussed hereinabove and the engagement of cap body  436  within the interior surfaces of jaws  112 ,  114 . 
     Rod shaft  204  is rotated in direction “D 1 ” until spinal shaft  402  and locking cap  430  are fully seated within U-shaped channel  414  of bone screw  404 , as seen in  FIGS. 23 and 24 . Thereafter, handle assembly  180  of locking shaft  104  is rotated through a 45 degree arc of rotation (relative to tubular body  108  discussed hereinabove) to cause corresponding rotation of main body  184  and socket  186  of the locking sleeve  104 . As socket  186  rotates, the keyed structure f socket head  186  and cap spin  208  causes the cap spin  208  and thus locking cap  430  to rotate. As seen in  FIGS. 25 and 26 , the rotation of locking cap  430  also results in engagement flanges  440 ,  442  being rotated into respective camming slots  422 ,  424  of head portion  406  of bone screw  404  thereby locking spinal rod  402  in U-shaped channel  414  of bone screw  404  in compressive relation therewith. 
     With reference to  FIGS. 27A-27C , following the fixation of locking cap  430  and spinal rod  402  to bone screw  404 , rod shaft  204  is rotated in a direction “D 2 ,” opposite direction “D 1 ,” to withdraw rod persuader  102  and to disengage shaped tip  212  of cap spin  208  from locking cap  430 . Jaw assembly  120  is then opened as depicted in  FIG. 27C  to remove the apparatus. 
     As seen in  FIG. 28 , rod persuader  100  can be used multiple times to lock a spinal rod  402  to multiple bone screws  404  which are screwed into vertebrae “V” of the spinal chord. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described to be protected. For example, it is envisioned that continued rotation of rod persuader  102  may effectuate locking of the locking cap within the screw  404  without requiring separate rotation of the handle  180  of the locking shaft  104  by the user. In this regard, the rod persuader may be mechanically connected (through a friction fit, etc. . . . ) to the locking shaft such that rotation of the rod persuader subsequent to driving the spinal rod within the screw head will cause rotation of the locking shaft and thus the locking cap. It is envisioned with this arrangement that handle  180  of the locking shaft may be engaged to secure the locking shaft during rotating withdrawal of the rod persuader  102  from the apparatus  100 . 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.