Abstract:
A method for reducing a fixation rod is provided. The method minimizes the surgical corridor by performing fixation within the surgical corridor defined by the screw extender. The screw extender is attached to the spinal implant. The method includes the steps of coupling the proximal end of a first cannulated body with the screw extender and rotating a second cannulated body within the first cannulated body. The method proceeds to the step of actuating a rod pusher with a first driving feature so as to engage the rod pusher with the fixation rod. The rod pusher includes a bore. The method proceeds to the step of rotating an inserter shaft within first cannulated body, second cannulated body and bore of the rod pusher, the inserter shaft including a proximal end with a second driving feature and a distal end with a setscrew attachment feature.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a divisional of U.S. application Ser. No. 13/957,218 filed Aug. 1, 2013, which claims priority from U.S. Provisional Application Ser. No. 61/679,294, filed on Aug. 3, 2012 and entitled “MIS Rod Inserter with Set Screw Inserter” which is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure generally relates to the field of spinal orthopedics, and more particularly to instruments and methods for reducing and securing spinal rods within a spinal fixation system. 
       BACKGROUND 
       [0003]    The spine is a flexible column formed of a plurality of bones called vertebrae separated by cartilaginous disks. The spine includes seven cervical (neck) vertebrae, 12 thoracic (chest) vertebrae, five lumbar (lower back) vertebrae, and the fused vertebrae in the sacrum and coccyx that help to form the hip region. While the shapes of individual vertebrae differ among these regions, each is essentially a short hollow tube containing the bundle of nerves known as the spinal cord. Individual nerves, such as those carrying messages to the arms or legs, enter and exit the spinal cord through gaps between vertebrae. The different vertebrae are connected to one another by means of articular processes and intervertebral, fibrocartilaginous bodies. 
         [0004]    The spinal disks act as shock absorbers, cushioning the spine, and preventing individual bones from contacting each other. Disks also help to hold the vertebrae together. The weight of the upper body is transferred through the spine to the hips and the legs. The spine is held upright through the work of the back muscles, which are attached to the vertebrae. While the normal spine has no side-to-side curve, it does have a series of front-to-back curves, giving it a gentle “S” shape. The spine curves in at the lumbar region, back out at the thoracic region, and back in at the cervical region. 
         [0005]    Various spinal disorders may cause the spine to become misaligned, curved, and/or twisted or result in fractured and/or compressed vertebrae. It is often necessary to surgically correct these spinal disorders. Spinal fusion is a procedure that promotes fusing or growing together of two or more vertebrae in the spine. Spinal fusion can be performed to straighten a spine deformed by scoliosis, neuromuscular disease, cerebral palsy, or other disorders; prevent further deformation; support a spine weakened by infection or tumor; reduce or prevent pain from pinched or injured nerves; or compensate for injured vertebrae or disks. The procedure may improve posture, increase ability to ventilate the lungs, prevent pain, or treat spinal instability and reduce the risk of nerve damage. 
         [0006]    One of the types of spinal fusion procedures is a posterior spinal fusion surgery. This procedure is performed posteriorly, or from the back of patient, as opposed to anteriorly, or through the abdomen. Generally the correct curvature is obtained by manipulating the vertebrae into their proper position and securing that position with a rigid system of screws and rods. The screws may be inserted into the pedicles of the vertebrae to act as bone anchors, and the rods may be inserted into heads of the screws. Two rods may run substantially parallel to the spine and secure the spine in the desired shape and curvature. Thus the rods, which are shaped to mimic the correct spinal curvature, force the spine into proper alignment. Bone grafts are then placed between the vertebrae to aid in fusion of the individual vertebrae together to form a correctly aligned spine. 
         [0007]    There have been various approaches and systems for performing posterior spinal surgery. Some conventional systems include titanium construction that is compatible with current CT and MRI scanning technology, low profile implant systems, top-loading and top-tightening systems, and other parameters. Some systems also include cross-connectors that allow a one-piece implant to be applied to a dual-rod construct for a top-loading approach. 
         [0008]    In minimally invasive surgery (MIS), access to the screws may be severely limited to the space provided by extenders or extension members attached to the screw heads. For example, an exemplary posterior system including screws and extenders may be found in commonly assigned U.S. Application Pub. No. 2010/0036443, entitled “Systems and Methods for Spinal Fixation” filed on Aug. 11, 2009 to Hutton et al. The system may be used in a MIS setting. The extenders may attach to the screw heads at a distal end and extend outside the MIS surgical opening at a proximal end. The extenders are generally tubular and may also include slots along their lengths for insertion of fixation rods. The extenders include a cannula extending from the proximal end to the distal end for insertion of various instruments and setscrews. For example, one or more instruments may be required to position the fixation rods into the heads of the screws, seat the rods within the heads, insert set screws to retain the rods within the heads, and tighten the set screws to rigidly fix the system together to ensure proper bone fusion. 
         [0009]    A typical rod reduction instrument may include a cannulated tube that slides over the screw extender. For example, the reduction instrument may include a cannula through which the screw extender may slide. Thus, the reduction instrument may include a larger footprint than the surgical opening. The larger footprint may increase the size of the surgical opening. The reduction instrument may also inhibit loading and insertion of a setscrew used to secure the rod within the screw head. For example, after reduction of the rod into the screw head, a separate instrument may be used to insert the setscrew and advance the setscrew into the screw head to fix the rod therein. 
       SUMMARY 
       [0010]    An instrument for reducing a fixation rod within a screw extender that attaches to a spinal implant includes first, second, and third cannulated bodies and an inserter shaft. The first cannulated body includes a proximal end that couples with the screw extender. The second cannulated body rotates within the first cannulated body and includes a proximal end with a first driving feature and a distal end with an internal threaded portion. The third cannulated body includes a proximal end that engages the internal threaded portion and a distal end with a rod pusher for engaging the fixation rod. The inserter shaft rotates within the third cannulated body and includes a proximal end with a second driving feature and a distal end with a setscrew attachment feature. 
         [0011]    In other features, rotation of the second cannulated body positions the third cannulated body to reduce the fixation rod within at least one of the screw extender and the spinal implant. The setscrew attachment feature retains a setscrew rotates to engage the setscrew with the spinal implant for securing the fixation rod within the spinal implant. The rod pusher includes a pair of cantilevered arms extending distally away from the third cannulated body. The first driving feature attaches to a removable handle for rotating the second cannulated body. The first cannulated body couples with the screw extender by a threaded connection. The rod pusher includes a ridge for engagement with a slot within the screw extender. The rod pusher includes a curved engagement surface configured to engage a curved surface of the fixation rod. 
         [0012]    In still other features, the instrument includes a quick connect sleeve for coupling the first cannulated body with the screw extender. The instrument includes a handle including a first actuation feature that engages the first driving feature and a second actuation feature that engages the second driving feature. 
         [0013]    A method for reducing a fixation rod within a screw extender that attaches to a spinal implant includes the steps of coupling a proximal end of a first cannulated body with the screw extender; rotating a second cannulated body within the first cannulated body, the second cannulated body including a proximal end with a first driving feature and a distal end with an internal threaded portion; engaging proximal end of a third cannulated body with the internal threaded portion; engaging a rod pusher on a distal end of the third cannulated body with the fixation rod; and rotating an inserter shaft within the third cannulated body, the inserter shaft including a proximal end with a second driving feature and a distal end with a setscrew attachment feature. 
         [0014]    In other features, rotating the second cannulated body positions the third cannulated body to reduce the fixation rod within at least one of the screw extender and the spinal implant. 
         [0015]    In still other features, the method includes the steps of retaining a setscrew on the setscrew attachment feature and engaging the setscrew with the spinal implant for securing the fixation rod within the spinal implant; engaging the fixation rod with a pair of cantilevered arms extending distally away from the third cannulated body; attaching a removable handle to the first driving feature and rotating the second cannulated body; coupling the first cannulated body with the screw extender by a threaded connection; engaging a ridge of the rod pusher with a slot within the screw extender; engaging a curved engagement surface of the rod pusher with a curved surface of the fixation rod; coupling the first cannulated body with the screw extender with a quick connect sleeve; and engaging a first actuation feature of a handle with the first driving feature and a second actuation feature of the handle with the second driving feature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIGS. 1A and 1B  are perspective views of a first exemplary instrument for reducing and securing spinal rods according to the principles of the present disclosure. 
           [0017]      FIG. 2  is an exploded view of a screw extender system, the first exemplar instrument, and a handle according to the principles of the present disclosure. 
           [0018]      FIG. 3  a perspective view of the instrument and handle engaged with the screw extender system to reduce and secure a spinal rod according to the principles of the present disclosure. 
           [0019]      FIG. 4  is an exploded view of the first exemplary instrument according to the principles of the present disclosure. 
           [0020]      FIG. 5  is an exploded view of first and second cannulated bodies of the first exemplary instrument according to the principles of the present disclosure. 
           [0021]      FIGS. 6A and 6B  are side views of the first exemplary instrument in a retracted position prior to a reduction step and during the reduction step according to the principles of the present disclosure. 
           [0022]      FIGS. 7A and 7B  are cross-sectional views of the instrument of  FIGS. 6A and 6B  along planes VII-A and VII-B according to the principles of the present disclosure. 
           [0023]      FIG. 8  is a perspective view of the handle according to the principles of the present disclosure. 
           [0024]      FIGS. 9A and 9B  are side and cross-sectional views along the plane IX-B of the handle of  FIG. 8  according to the principles of the present disclosure. 
           [0025]      FIGS. 10A and 10B  are side views of the first exemplary instrument reducing the fixation rod within the screw extender system according to the principles of the present disclosure. 
           [0026]      FIGS. 11A and 11B  are cross-sectional views of the instrument of  FIGS. 10A and 10B  along the planes XI-A and XI-B respectively according to the principles of the present disclosure. 
           [0027]      FIGS. 12A and 12B  are enlarged views of the instrument of  FIGS. 11A and 11B  in circled areas XII-A and XII-B respectively according to the principles of the present disclosure. 
           [0028]      FIGS. 13A and 13B  are side and cross-sectional views along the plane XIII-B of a second exemplary instrument for reducing the fixation rod within a screw extender system according to the principles of the present disclosure. 
           [0029]      FIG. 14  is an exploded view of the instrument of  FIGS. 13A and 13B  according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Each of the instruments and methods for reducing and securing a spinal rod of the present disclosure includes features that provide a decreased footprint for insertion within the cannula of a screw extender. Each of the instruments includes features for preloading and insertion of a setscrew to secure the spinal rod within the head of a previously inserted screw. Each of the instruments includes features for easy and quick attachment to the screw extender and features various driver attachments for reducing and/or advancing the setscrew to rigidly secure the fixation rod within the head of the screw. 
         [0031]    Embodiments of the invention will now be described with reference to the Figures, wherein like numerals reflect like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive way, simply because it is being utilized in conjunction with detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the invention described herein. The words proximal and distal are applied herein to denote specific ends of components of the instrument described herein. A proximal end refers to the end of an instrument nearer to an operator of the instrument when the instrument is being used. A distal end refers to the end of a component further from the operator and extending towards the surgical area of a patient and/or the implant. 
         [0032]      FIGS. 1A and 1B  illustrate perspective views of a first exemplary instrument  100  for reducing a fixation rod within a receiving portion of the screw head and inserting a setscrew to rigidly secure the rod to the head. For example, as illustrated in  FIGS. 2 and 3 , the instrument  100  may be used with a minimally invasive surgery (MIS) system comprising one or more screw extenders  300 , screw assemblies  400 , and fixation rods  500 . Exemplary MIS systems with similar screws, extenders, and rods may be found in commonly assigned U.S. Pub. No. 2010/0036443. However, features of the instrument  100  may be compatible with various other MIS systems known in the art. The instrument  100  may be used with actuation means such as a handle  600  that connects with the instrument  100 . 
         [0033]    The instrument  100  includes various features to reduce the fixation rod  500  into a receiving portion  402  of the screw assembly  400  and insert a setscrew  404  to retain the fixation rod  500  therein. As illustrated in  FIG. 3 , the instrument  100  may be inserted into the screw extender  300  and couple at its proximal end. A distal end of the screw extender  300  couples with the receiving portion  402  of the screw assembly  400 . The handle  600  attaches to the proximal end of the instrument  100  and includes features to actuate the instrument  100 . The fixation rod  500  may be inserted into the distal end of the screw extender  300  while the instrument  100  is in the retracted position. The fixation rod  500  may be advanced distally as the instrument  100  moves towards the extended position. The fixation rod  500  may be fully seated within the receiving portion  402  of the screw assembly  400  when the instrument  100  is in the extended position. Once the fixation rod  500  is fully seated, the handle  600  may include a second actuating feature  604  for actuating the instrument  100  to advance the setscrew  404  into the receiving portion  402  of the screw assembly  400  to rigidly couple the fixation rod  500  therein. 
         [0034]    Continuing now also with  FIGS. 4 and 5 , the instrument  100  may include a plurality of concentric bodies and shafts that rotate relative to one another to linearly displace features that apply force on the fixation rod  500 . Various features may engage the screw extender  300  and retain and drive the setscrew  404  to lock the fixation rod  500  with the screw assembly  400 . The instrument  100  includes a first body  102 , a second body  104 , and a third body  106 . The first body  102  includes first cannula  108  that receives the second body  104 . The first cannula  108  may be substantially smooth from a proximal end to a distal end of the first body  102  which permits rotation of the second body  104  therein. At the proximal end of the first body  102 , coupling means, such as an external thread  110 , may be configured to couple with mating threads  302  on a proximal end of a screw extender  300  as shown in  FIG. 2 . 
         [0035]    The second body  104  extends through the first cannula  108  and may include retaining portions, such as a proximal cap  112  and a distal lip  114  that extend outside the first cannula  108  and retain the second body  104  therein. The proximal cap  112  and distal lip  114  may retain the second body  104  within the first body  102  while permitting rotation within the first cannula  108 . The proximal cap  112  may removably couple with the second body  104  to retain the second body  104  within the first cannula  108 . The proximal cap  112  may include a first driving feature  116  that mates with features of the handle  600  for rotating the second body  104  within the first body  102 . For example, first driving feature  116  may include a recessed portion including a first geometry such as a rectangular or square shape that mates with corresponding geometry of a first actuating shaft  602  of the handle  600 . As the first driving feature  116  is rotated, one or more portions of the second body  104  may rotate in the same direction. 
         [0036]    The second body  104  includes a second cannula  118  that receives the third body  106 . At a distal end of the second cannula  118 , an internally threaded portion  120  may be configured to engage features of the third body  106  as illustrated in detail with  FIGS. 7A and 7B . The third body  106  includes a proximal end that engages the internally threaded portion  120  of the second cannula  118 . For example, the proximal end may include a mating external threaded portion  122  for threaded engagement with the second cannula  118 . The third body  106  includes a distal end that engages the fixation rod  500  as described herein. For example, the distal end may include a rod pusher  124  for engaging the fixation rod  500 . The rod pusher  124  includes a substantially cylindrical profile. The rod pusher  124  may include one or more arms  126  extending distally away from the third body  106 . For example, the arms  126  may cantilever away from the sides of the rod pusher  124 . The arms  126  may terminate in contoured tips  127  conforming to the radius of the fixation rod  500 . 
         [0037]    The third body  106  may include a third cannula  128  for receiving an inserter shaft  130 . The inserter shaft  130  may include features for retaining, inserting, and driving the setscrew  404 . In the present example, the inserter shaft  130  includes an elongated, cylindrical profile extending from a proximal end to a distal end. The inserter shaft  130  may rotate freely within the third cannula  128 . The proximal end of the inserter shaft  130  may extend proximally through the second cannula  118  and past the first driving feature  116 . The proximal end of the inserter shaft  130  may include a second driving feature  132  that mates with an actuator for rotating the inserter shaft  130  within the third body  106 . For example, the second driving feature  132  may include a shaped portion of the inserter shaft  130  including a second geometry such as a rectangular or square shape. As the second driving feature  132  is rotated, the inserter shaft  130  may rotate in the same direction. The distal end of the inserter shaft  130  may extend outside the third cannula  128  and include an attachment feature  134  such as a hexalobe or splined pattern. The attachment feature  134  may retain the setscrew  404  by frictional engagement with a recessed portion of the setscrew  404  as known in the art. 
         [0038]    Other features of the instrument  100  may include a coupler for quick connect and secure coupling of the instrument  100  to the screw extender  300 . The coupler may include an outer sleeve  136 , an inner sleeve  138 , and a bias mechanism  140 . Pins  142  extending radially from the proximal end of the first body  102  may pass through slots  144  in the outer sleeve  136  and slots  146  in the inner sleeve  138  and permit the coupler to slide relative to the first body  102 . The bias mechanism  140  may bias the sleeves  136  and  138  distally or proximally. To attach the instrument  100  to the screw extender  300 , the user may compress or expand the bias mechanism  140  to engage the external thread  110  on the first body  102  with the mating threads  302  of the screw extender  300 . In other features, a limit pin  148  may extend through a transverse slot  150  in the inserter shaft  130 . The limit pin  148  may limit advancement of the inserter shaft  130  distally through the third cannula  128  by engagement with the proximal end of the third body  106 . For example, ends of the limit pin  148  may extend outside the transverse slot  150  to engage the distal end of the third body  106  as the inserter shaft  130  slides distally through the third cannula  128 . Thus, the inserter shaft  130  may rotate freely in the third cannula  128  but not pass completely through the third cannula  128 . 
         [0039]      FIGS. 6A-7B  illustrate additional views of the instrument  100  in both retracted ( FIGS. 6A and 7A ) and extended ( FIGS. 6B and 7B ) positions as used with MIS systems. In the retracted position, the instrument  100  includes a first overall length L 1  as measured from a top surface of the proximal cap  112  to the contoured tips  127  of the arms  126 . As the second body  104  rotates, the external threaded portion  122  of the rod pusher  124  engages the internally threaded portion  120  of the second cannula  118 . Rotation in a first direction, such as a clockwise direction, causes the rod pusher  124  to extend distally. Rotation in a second direction, such as a counter-clockwise direction, causes the rod pusher  124  to retract proximally. In the extended position, the instrument includes a second overall length L 2  as measured from the top surface of the proximal cap  112  to the contoured tips  127  of the arms  126 . The second length L 2  may be greater than the first length L 1 . Both the first length L 1  and the second length L 2  may be less than a length L 3  of the screw extender  300  as shown in  FIG. 2 . The inserter shaft  130  may freely float within the third cannula  128  as the rod pusher  124  retracts and extends relative to the second body  104 . The limit pin  148  limits movement of the inserter shaft  130  distally by engaging the upper surface of the rod pusher  124 . 
         [0040]      FIGS. 8-9B  illustrate additional features of the handle  600  for actuation of the instrument  100 . The handle  600  includes a handle body  606  with the second actuating feature  604  at its distal end. The second actuating feature  604  may engage the first driving feature  116  of the instrument  100 . For example, the second actuating feature  604  may include a shaped portion of the handle body  606  corresponding to the shape of the first driving feature  116 , such as a square or rectangular profile. The handle body  606  may include an outer gripping surface such as applied silicone. As the handle body  606  rotates, the second actuation feature  604  rotates. The handle body  606  may include a fourth cannula  608  through which a handle shaft  610  extends. The fourth cannula  608  may extend from a proximal end to a distal end of the handle  600 . 
         [0041]    A proximal cap  612  and a distal cap  614  may thread onto the ends of the fourth cannula  608  and include apertures through which the handle shaft  610  may pass. The apertures  616  may provide bearing surfaces for improved rotation of the handle shaft  610  within the handle body  606 . A third actuating feature  618  on the distal end of the handle shaft  610  may extend outside the fourth cannula  608 . The third actuating feature  618  may engage the second driving feature  132  of the instrument  100 . For example, the third actuating feature  618  may include a recessed portion  620  or pocket corresponding to the shape of the second driving feature  132 , such as a square or rectangular profile. On the proximal end of the handle shaft  610 , a knob  622  may be used to rotate the handle shaft  610 . 
         [0042]    Referring now to  FIGS. 10A-12B , the instrument  100  is shown coupled within the screw extender  300  that is attached to the screw assembly  400 . The instrument  100  may be actuated by the handle  600  to reduce the fixation rod  500  within the screw assembly  400  and insert the setscrew  404  to retain the fixation rod  500  within the receiving portion  402 . For example, the proximal end of the instrument  100  may be coupled to the proximal end of the screw extender  300  via threaded engagement and/or the coupler sleeves  136  and  138 . The first body  102 , second body  104 , and third body  106  extend distally into the screw extender  300 . 
         [0043]    In the retracted position as best illustrated in  FIGS. 10A, 11A, and 12A , the contoured tips  127  of the arms  126  may begin to engage the fixation rod  500  at some distance from the receiving portion  402  of the screw assembly  400 . The setscrew  404  may be secured to the attachment feature  134  of the inserter shaft  130  which floats freely within the third cannula  128 . As the handle body  606  rotates in the first direction, the second actuating feature  604  rotates second body  104  within the first body  102  via the first driving feature  116 . The rotational movement causes the rod pusher  124  to advance distally and apply force to the fixation rod  500  via the arms  126 . The inserter shaft  130  may follow the rod pusher  124  distally with the attached setscrew  4040  floating just above the fixation rod  500 . The rod pusher  124  continues to advance distally until the fixation rod  500  is seated within the receiving portion  402  of the screw assembly  400 . 
         [0044]    In the extended position as best illustrated in  FIGS. 10B, 11B, and 12B , the contoured tips  127  of the arms  126  may continue to engage the fixation rod  500  and hold it within the receiving portion  402  of the screw assembly  400 . The setscrew  404  may be advanced by the inserter shaft  130  onto threads of the receiving portion  402  by rotating the knob  622  of the handle  600 . As the knob  622  rotates in a first direction, for example a clockwise direction, the setscrew  404  may engage more of the thread of the receiving portion  402  and advance distally towards the fixation rod  500 . The knob  622  may rotate in a second opposite direction, for example, a counter-clockwise direction, to remove the setscrew  404 . Once the setscrew  404  has been inserted and tightened sufficiently, the instrument  100  may be uncoupled from the screw extender  300 . 
         [0045]      FIGS. 13A-14  illustrate another exemplary instrument  700  for reducing a fixation rod within a screw extender. The instrument  700  includes a first body  702 , a second body  704 , and a third body  706 . The first body  702  includes a first cannula  708  that receives the second body  704 . The first cannula  708  may be substantially smooth from a proximal end to a distal end of the first body  702  to permit rotation of the second body  704  therein. The first body  702  may slide over the proximal end of a screw extender such as screw extender  300 . The second body  704  may include a threaded portion  710  for engagement with the mating threads  302  of the screw extender  300 . A proximal end of the second body  704  may include a proximal cap  712  with a driving feature  716 . The driving feature  716  mates with features of the handle  600  for rotating the second body  704  within the first body  702 . For example, driving feature  716  may include a recessed portion including a first geometry such as a rectangular or square shape that mates with corresponding geometry of the first actuating shaft  602  of the handle  600 . As the driving feature  716  is rotated, one or more portions of the second body  704  may rotate in the same direction. 
         [0046]    The second body  704  includes a second cannula  718  that receives the third body  706 . The third body  706  includes a proximal end that engages the second cannula  718 . For example, the proximal end may include a flexible collet  720  for engagement with one or more grooves  722  within the second cannula  718 . The flexible collet  720  may snap into the groove  722  by elastically deforming radially inward. Once the flexible collet  720  couples within the groove  722 , the third body  706  may rotate within the second cannula  718 . The third body  706  includes a distal end that engages the fixation rod  500  as described herein. For example, the distal end may include a rod pusher  724  for engaging the fixation rod  500 . The rod pusher  724  includes a substantially cylindrical profile. The rod pusher  724  may include one or more arms  726  extending distally away from the third body  706 . For example, the arms  726  may cantilever away from the sides of the rod pusher  724 . The arms  726  may terminate in contoured tips  727  conforming to the radius of the fixation rod  500 . 
         [0047]    The present exemplary instrument  700  may reduce the fixation rod  500  within the screw assembly  400  by threaded engagement with mating threads  302  on the screw extender  300 . For example, the instrument  700  may be threaded onto the screw extender by engaging threaded portion  710  with the mating threads  302 . The arms  726  may engage the slots  304  of the screw extender  300 . The handle  600  or other actuation instrument may be inserted into the driving feature  716  to rotate the second body  704  to either advance the instrument  700  distally or proximally within the screw extender  300 . For example, rotating the second body  704  in a first direction, such as a clockwise direction, advances the instrument  700  distally to engage the arms  726  with the fixation rod  500  for reduction. Rotating the second body  704  in a second direction, such as a counter-clockwise direction, retracts the instrument  700  proximally to disengage the arms  726 . The third body  706  may include a third cannula  728  to receive an inserter shaft similar to the inserter shaft  130  of the instrument  100  of  FIGS. 1-12 . 
         [0048]    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.