Patent Publication Number: US-2023143005-A1

Title: Lateral rod reducer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/276,515 filed Nov. 5, 2021, which is incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates generally to the field of surgery, and more specifically, to a lateral rod reducer for use in spinal fusion surgery. 
     BACKGROUND 
     Many spinal fixation systems use pedicle screws attached to two or more vertebrae coupled to a fixation rod. The pedicle screw includes a body member or tulip that includes a tulip slot or U-shaped channel to accept the fixation rod. A set screw is used to threadably engage the body member of the screw assembly to secure the stabilizing rod within the body member. Positioning the spinal fixation rod in the screw head typically requires the drawing of the rod to the screw using a rod reducer. 
     Rod reducers are placed over the spinal fixation rod and attached to the pedicle screw body member or tulip. The rod reducer then pushes the spinal fixation rod into the tulip slot or U-shaped channel and a set screw is used to clamp the rod in place. 
     In certain situations, the spinal fixation rod may not be aligned with the tulip slot or U-shaped channel of the pedicle screw during a spinal fusion surgery. Current rod reduction instruments do not correct misalignment of the spinal fixation rod with the tulip slot or U-shaped channel. So the surgeon must use a separate lateral reducer. Lateral reducers currently on the market utilize a hinged lever arm that, when squeezed by the surgeon, laterally reduce the rod. The lever arm concept requires that the surgeon fully squeeze and operate the lever to complete 100% of the available lateral reduction once started. The lateral reducer does not allow for incremental lateral reduction. 
     Thus, there is a need for an improved rod reducer that solves the problems listed above. 
     SUMMARY 
     The present invention is directed to a rod reducer that is both a lateral rod reducer and axial rod reducer. The lateral rod reducer uses an entirely different mechanism never before used for lateral reduction. The lateral rod reducer described herein is capable of both lateral reduction a spinal fixation rod and axial reduction of a spinal fixation rod. Splitting the reducer body geometry to create a jaw that is then driven by a linkage system is novel. The lateral rod reducer of the present invention allows for incremental lateral reduction that utilizes a threaded linkage feature for increased power/mechanical advantage when laterally reducing. This will allow for new techniques of lateral rod manipulation in deformity cases. 
     The lateral rod reducer described herein is capable of reducing a spinal fixation rod both laterally and axially to couple with a pedicle screw. The spinal fixation rod is reduced laterally with a hinged jaw to position the spinal fixation rod over the tulip slot or U-shaped channel of the pedicle screw tulip. The spinal fixation rod is then reduced axially with a ram into the U-shaped channel or tulip slot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1  and  2    show one embodiment of a lateral rod reducer. 
         FIG.  3    is a sectional view of the lateral rod reducer. 
         FIG.  4    is a perspective view showing the distal end of the fixed jaw and hinged jaw. 
         FIG.  5    is a sectional view at A-A of  FIG.  3     
         FIG.  6    is a cross-sectional view showing the fixed jaw and hinge jaw coupled to the tulip of the screw. 
         FIG.  7    is a view showing a spinal fixation rod positioned laterally from a pedicle screw. 
         FIGS.  8 - 11    are views showing operation of the lateral rod reducer moving the spinal fixation rod laterally and then moving the spinal fixation rod axially to the tulip of a pedicle screw. 
         FIGS.  12  and  13    show the lateral rod reducer engaging and translating the spinal fixation rod laterally with the hinged jaw. 
         FIGS.  14  and  15    show axial reduction of the spinal fixation rod into the tulip slot. 
     
    
    
     DETAILED DESCRIPTION 
     In certain situations, the spinal fixation rod may not be aligned with the tulip slot or U-shaped channel of the pedicle screw during a spinal fusion surgery. The present invention solves this problem by providing a lateral rod reducer that is configured to move the spinal fixation rod that is not aligned to position it above the tulip slot or U-shaped channel of the pedicle screw. Once in position, the present invention also provides an axial rod reducer to advance the spinal fixation rod axially into the tulip slot or U-shaped channel. In some embodiments, the present invention may also advance a set screw to secure the spinal fixation rod within the tulip slot or U-shaped channel. 
     In the embodiments shown, the lateral rod reducer utilizes a hinged jaw coupled to a lateral reduction mechanism that is configured to extend laterally to engage a spinal fixation rod and then closes the hinged jaw to medially reduce the spinal fixation rod to the tulip slot or U-shaped channel of pedicle screw. The fixed jaw engages the pedicle screw with a dovetail connection while the hinged jaw engages the spinal fixation rod. The lateral reduction mechanism includes a threaded ram and linkage mechanism driven by a hexalobe connection at the top of the instrument. Turning the hexalobe drive closes the jaw to bring the spinal fixation rod in-line with the tulip slot. The hexalobe connection is not pertinent to the functionality, different drive patterns could be used. Once the hinged jaw is closed, the lateral rod reducer behaves like a traditional sequential reducer. Drivers are used to translate a threaded ram which pushes the rod down into the tulip slot. 
       FIGS.  1  and  2    show one embodiment of a lateral rod reducer  200  having a body  205  with a fixed jaw  210  and a hinged jaw  215  extending from a distal end of the body  205 . The fixed jaw  210  is configured to couple with a tulip  110  of a pedicle screw  100  using a dovetail connection, and the hinged jaw  215  is configured to couple with the tulip  110 . A lateral reduction mechanism  230  is configured to rotate the hinged jaw  215  laterally outward to engage a spinal fixation rod  120  and then rotate the hinged jaw  215  medially inward to reduce the spinal fixation rod  120  to the tulip  110 . The axial reduction mechanism  235  with an axial threaded ram  220  is used to apply a load and reduce the spinal fixation rod  120  axially into a tulip slot  115  of the pedicle screw  100 . Both the fixed jaw  210  and hinged jaw  215  are configured to engage the tulip  110  to secure the connection between the lateral rod reducer  200  and pedicle screw  100  for spinal rod reduction. 
       FIG.  3    is a cross-sectional view of the lateral rod reducer  200  showing the body  205  having a side lumen  206  housing the lateral reduction mechanism  230 , and a central lumen  260  housing the axial reduction mechanism  235 . The fixed jaw  210  is coupled to the body  205  and the hinged jaw  215  is coupled to the lateral reduction mechanism  230 . In other embodiments, both the jaws may be hinged jaws. The fixed jaw  210  and hinged jaw  215  include a distal portion configured to engage the tulip or head  110  of the pedicle screw  100 . The hinged jaw  215  is further configured to engage and laterally reduce a spinal fixation rod  120 . 
     The lateral reduction mechanism  230  includes a lateral threaded ram  245  positioned within a threaded portion of the side lumen  206 . A distal end of the lateral threaded ram  245  is coupled to a proximal end of a linkage mechanism  240 , and a distal end of the linkage mechanism  240  is coupled to the hinged jaw  215 . The lateral threaded ram  245  includes a lateral driver connection  250  at a proximal end configured to engage a lateral driver  255 . The lateral driver  255  is configured to rotate the lateral threaded ram  245  to move the linkage mechanism  240  forward or backward to open or close the hinged jaw  215 . The lateral driver connection  250  may be a hexalobe connection, but many different drive patterns could be used. 
     The axial reduction mechanism  235  includes an axial threaded ram  220  positioned within a threaded portion of the central lumen  260  of the body  205 . The axial threaded ram  220  includes an axial driver connection or feature  265  at a proximal end configured to engage an axial driver  270 . The axial driver  270  is configured to rotate axial threaded ram  220  to advance or retract it. The axial driver connection  265  may be a hexalobe connection, but many different drive patterns could be used. The distal end of the axial threaded ram  220  is configured to engage a spinal fixation rod  120  and reduce it to the tulip slot  115  of a pedicle screw  100 . In some embodiments, the lateral driver  255  and axial driver  270  may be the same driver, so only one driver is need for lateral and axial reduction of the spinal fixation rod  120 . 
       FIG.  4    is a perspective view showing the distal end of the fixed jaw  210  and hinged jaw  215  and  FIG.  5    is a sectional view at A-A of  FIG.  3    showing the engagement features of the fixed jaw  210  and hinged jaw  215 . 
     The fixed jaw  210  has an internal pocket  211  shaped to partially wrap around the tulip&#39;s cross-sectional shape having a dovetail geometry with inwardly curved ends  212 . The fixed jaw  210  is designed to slide axially on the tulip  110 . This aligns the lateral rod reducer  200  with the tulip  110 . The fixed jaw  210  further includes an inward protrusion  213  configured to couple with a recess in the tulip  110 . The inward protrusion  213  may be part of an internal surface of the pocket  211 , or may be part of a flexible attached member  214 , as shown in the figures. The flexible attachment member  214  is configured to flex the inward protrusion  213  outwardly when the fixed jaw  210  is slid onto the tulip  110 , then flex back when the inward protrusion  213  reaches the recess on the side of the tulip  110 . 
     The hinged jaw  215  includes an internal pocket  216  that is U-shaped to partially wrap around the tulip&#39;s cross-sectional shape when the hinged jaw  215  is in the closed position. The hinged jaw  215  is designed to engage the tulip  110  after lateral reduction of the spinal fixation rod  120 . The hinged jaw  215  includes an inward protrusion  217  configured to couple with a recess in the tulip  110 . 
     Once the fixed jaw  210  and hinged jaw  215  are coupled to the tulip  110 , the connection between the lateral rod reducer  200  and the tulip  110  of the pedicle screw  100  is secure so that they will not separate during axial reduction of the spinal fixation rod  120 . 
       FIG.  6    is a cross-sectional view showing the fixed jaw  210  and hinge jaw  215  coupled to the tulip  110  of the screw  100 . Once the fixed jaw  210  and hinged jaw  215  have coupled with the tulip  110 , the lateral rod reducer  200  is locked on the screw  100  to hold it in place during axial reduction of the spinal fixation rod  120  into the tulip recess  115 . 
       FIG.  7    is a view showing a pedicle screw  100  used in spinal surgery having threads  105  for attachment to the spine and proximal head  110  with a tulip slot or U-shaped channel  115  sized for a spinal fixation rod  120 . In the figure, the spinal fixation rod  120  is positioned laterally from the pedicle screw  100  and not aligned with the tulip slot or U-shaped channel  115 . In this lateral position, the spinal fixation rod  120  cannot be reduced into the tulip slot  115 . The spinal fixation rod  120  will need to be moved medially  125  so that it is positioned over the tulip slot  115 , then the spinal fixation rod  120  will need to be moved axially  140  into the tulip slot  115 . 
       FIGS.  8 - 11    show a one embodiment of a lateral rod reducer  200  configured to laterally move  125  a spinal fixation rod  120  that is not aligned with the tulip slot or U-shaped  115  during a spinal fusion surgery to position it above the tulip slot  115 . The lateral rod reducer is then configured to move the spinal fixation rod  120  axially  140  to reduce it into the tulip slot  115 . 
     The lateral rod reducer  200  includes a body  205  housing both a lateral reduction mechanism  230  and an axial reduction mechanism. The lateral reduction mechanism includes a jaw actuation mechanism  230  coupled to fixed jaw  210  and a hinged jaw  215  extending from a distal end of the body  205 . In the embodiment shown, the fixed jaw  210  is a fixed jaw and the hinged jaw  215  is a hinged jaw. In other embodiments, both the fixed and hinged jaws  210 ,  215  may be hinged. The lateral reduction mechanism  230  is configured to laterally translate the spinal fixation rod  120  to the pedicle screw  100 . Once the fixed and hinged jaws  210 ,  215  are closed, the lateral rod reducer  200  utilizes a ram  225  coupled to an axial reduction mechanism  230  positioned within the body  205  to axially push or advance the spinal fixation rod  120  down into the tulip slot  115  to reduce the spinal fixation rod  120  to the pedicle screw  100 . A set screw is then attached to the 
       FIG.  8    shows the lateral rod reducer  200  approaching the pedicle screw  100  and spinal fixation rod  120 . The fixed and hinged jaws  210 ,  215  are in the open position. 
       FIG.  9    shows the fixed and hinged jaws  210 ,  215  of the lateral rod reducer  200  in the open or expanded position with the fixed jaw  210  engaging the pedicle screw  100  and hinged jaw  215  engaging the spinal fixation rod  120 . Once in position, the lateral reduction mechanism  230  rotates  135  the hinged jaw  215  toward the fixed jaw  210 , which moves the spinal fixation rod  120  medially  125 . 
       FIG.  10    shows the fixed and hinged jaws  210 ,  215  in the closed position engaging the head  110  of the pedicle screw  100 . In this position, the spinal reduction rod  120  is above the tulip slot  115  and ready to be pushed into the tulip slot  115 . 
       FIG.  11    shows the ram  220  extending axially  140  by the lateral reduction mechanism  230 . During axial movement, the ram  220  pushes spinal fixation rod  120  into the tulip slot  115  of the pedicle screw  100 . 
     Lateral Reduction of the Spinal Fixation Rod 
     In certain situations, the fixation rod  120  is not aligned with the tulip slot  115  of the pedicle screw  100  during a spinal fusion surgery. The lateral rod reducer  200  is used to reduce the spinal fixation rod with the tulip slot  115 . 
       FIGS.  12  and  13    show the lateral rod reducer  200  engaging and translating the spinal fixation rod  120  laterally with the hinged jaw  215 . The process starts with the hinged jaw  215  in the open position, with the fixed jaw  210  engaging the tulip  110  and hinged jaw  215  engaging the spinal fixation rod  120  ( FIG.  12   ). The surgeon uses the lateral driver  255  to rotate the hexalobe connection  250  to drive the lateral threaded ram  245  and linkage mechanism  240 , which rotates the hinged jaw  215  medially from the open position to the closed position, where the spinal reduction rod  120  is above the tulip slot  115  and ready to be pushed into the tulip slot  115  ( FIG.  13   ). In the closed position, the hinged jaw  215  engages the tulip  110 . The fixed jaw  210  and hinge jaw  215  may include engagement features to couple with the tulip  110  and lock the lateral rod reducer  200  to the screw  100  to assist in axial reduction of the spinal fixation rod.  120   
     Axial Reduction of the Spinal Fixaiton Rod 
     Once the hinged jaw  215  is closed, the lateral rod reducer  200  behaves like a traditional sequential reducer. An axial drive  270  is use to translate a threaded ram  220  axially, which reduces the spinal fixation rod  120  into the tulip slot  115 . 
       FIGS.  14  and  15    show axial reduction of the spinal fixation rod  120  into the tulip slot  115 . The fixed jaw  210  and hinged jaw  215  are coupled to the tulip  110 . The axial driver  270  engages the proximal end of the axial threaded ram  220 . As the axial driver  270  is rotated, the axial threaded ram  220  advances distally and engages the spinal fixation rod  120  and pushes it distally into the tulip slot  115 . Once the spinal fixation rod  120  is within the tulip slot  115 , a set screw is used to lock them together. 
     The lateral rod reducer  200  is then removed. 
     Example embodiments of the methods and systems of the present invention have been described herein. As noted elsewhere, these example embodiments have been described for illustrative purposes only and are not limiting. Other embodiments are possible and are covered by the invention. Such embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but should be defined only in accordance with the following claims and their equivalents.