Abstract:
Systems, devices, and associated methods for correcting and stabilizing spinal column deformities that promote ease of use and surgical technique, help minimize attachment anchor sites, facilitate use of straight or contoured rods, and/or help promote a more natural, physiologic motion of the spinal column during and/or after correction.

Description:
BACKGROUND 
     Many systems have been utilized to treat spinal deformities such as scoliosis, spondylolisthesis, and a variety of others. Primary surgical methods for correcting a spinal deformity utilize instrumentation to correct the deformity, as well as implantable hardware systems to rigidly stabilize and maintain the correction. 
     SUMMARY 
     Some embodiments relate to systems, devices, and associated methods for correcting spinal column deformities that promote ease of use and surgical technique, help minimize attachment anchor sites, facilitate use of straight or contoured rods, and/or help promote a more natural, physiologic motion of the spinal column as an adjunct to fusion or non-fusion treatment methods. 
     Some embodiments relate to a transverse coupler for a spinal correction system. The transverse coupler includes an adjustment assembly configured to be secured to a first rod extending longitudinally along a first side of a spine. The adjustment assembly includes a rider, a retainer, and a first rod coupler. The transverse coupler also includes an adjustment arm configured to either partially or fully extend from the first side of the spine to the second side of the spine. The adjustment arm defines a first end, a second end, a first surface, a second surface, and a longitudinal axis extending from the first end to the second end. The transverse coupler also includes a force directing member with an elongate body configured to couple with the rider and the first end of the adjustment arm. The rider and the elongate body are configured to form a complementary fit, wherein the rider can move along the elongate body and couple with the adjustment arm at a plurality of angles. 
     This summary is not meant to be limiting in nature. While multiple embodiments are disclosed herein, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an implantable spinal correction and fusion system, according to some embodiments. 
         FIG. 2  is an isometric view of a transverse coupler of the system of  FIG. 1 , according to some embodiments. 
         FIG. 3  is an isometric view of the transverse coupler of  FIG. 2 , according to some embodiments. 
         FIG. 4  is an exploded view of the transverse coupler of  FIG. 2 , according to some embodiments. 
         FIG. 5  is a perspective view of a rider of the transverse coupler of  FIG. 2 , according to some embodiments. 
         FIG. 6  is an exploded view of the rider of  FIG. 5 , according to some embodiments. 
         FIG. 7  is a top view of the rider of  FIG. 5 , according to some embodiments. 
         FIG. 8  is a side view of the rider of  FIG. 5 , according to some embodiments. 
         FIG. 9  is a side view of an adjustment arm of the transverse coupler of  FIG. 2 , according to some embodiments. 
         FIG. 10  is a top view of the adjustment arm of  FIG. 9 , according to some embodiments. 
         FIG. 11  is a bottom view of the adjustment arm of  FIG. 9 , according to some embodiments. 
         FIG. 12  is a rear view of the adjustment arm of  FIG. 9 , according to some embodiments. 
         FIGS. 13-16  are side and rear views of a force directing member of the transverse coupler of  FIG. 2  and the adjustment arm of  FIG. 9  at various angulations, according to some embodiments. 
         FIGS. 17-19  show the transverse coupler of  FIG. 2  at various stages of realignment, according to some embodiments. 
         FIG. 20  is an isometric view of an alternative embodiment of a transverse coupler of the system of  FIG. 1 , according to some embodiments. 
         FIGS. 21-23  show top, side, and a rear views, respectively, of the transverse coupler of  FIG. 20 , according to some embodiments. 
         FIG. 24  is an isometric view of an alternative embodiment of a transverse coupler of the system of  FIG. 1 , according to some embodiments. 
         FIG. 25  is an isometric view of an alternative embodiment of a transverse coupler of the system of  FIG. 1 , according to some embodiments. 
         FIG. 26  is a perspective view of the transverse coupler of  FIG. 25  with some features not shown to facilitate understanding, according to some embodiments. 
         FIGS. 27-29  show the transverse coupler of  FIG. 25  at various stages of realignment, according to some embodiments. 
     
    
    
     Various embodiments have been shown by way of example in the drawings and are described in detail below. As stated above, the intention, however, is not to limit the invention by providing such examples. 
     DETAILED DESCRIPTION 
     Some embodiments relate to a spinal correction and fusion system for implantation into a patient, as well as associated methods and devices, where the system provides for lateral translational corrective force(s) and/or derotational corrective force(s) on a spinal column with associated instrumentation (e.g., for facilitating vertebral fusion at a selected region of the spine). Some features of the system optionally include implementation of a first, relatively longer rod for correction and stabilization, a second, shorter rod for secondary spinal correction and stabilization. If desired, the stabilization helps promote a fusion. In some embodiments, the spine retains freedom of motion above and below the spinal segment corresponding to the shorter rod, with the first, relatively longer rod remaining implanted. In other embodiments, the first, relatively longer rod is removed following correction and stabilization of the spinal column. A variety of additional or alternative features and advantages of the inventive systems are contemplated and provided by the instant disclosure. As used herein, the phrase “as shown” is indicative of a feature or features shown in the accompanying drawings, although as noted it should be understood that additional or alternative features to those shown are contemplated. 
     Various planes and associated directions are referenced in the following description, including a sagittal plane defined by two axes, one drawn between a head (superior) and tail (inferior) of the body and one drawn between a back (posterior) and front (anterior) of the body; a coronal plane defined by two axes, one drawn between a center (medial) to side (lateral) of the body and one drawn between a head (superior) and tail (inferior) of the body; and a transverse plane defined by two axes, one drawn between a back and front of the body and one drawing between a center and side of the body. The terms pitch, roll, and yaw are also used, where roll generally refers to angulation, or rotation, in a first plane through which a longitudinal axis of a body orthogonally passes (e.g., rotation about a longitudinal axis corresponding to the spinal column), pitch refers to angulation, or rotation, in a second plane orthogonal to the first plane, and yaw refers to angulation, or rotation, in a third plane orthogonal to the first and second planes. In some embodiments, pitch is angulation in the sagittal plane, yaw is angulation in the coronal plane, and roll is angulation in the transverse plane. 
     In various embodiments, changes in pitch, yaw, and/or roll occur concurrently or separately as desired. Moreover, as used herein, “lateral translation” is not limited to translation in the medial-lateral direction unless specified as such. 
       FIG. 1  shows a spinal correction system  10 , according to some embodiments. As shown, the system  10  includes a first rod  12 , a second rod  14 , a plurality of anchors, including a first stabilizing anchor  16 , a second stabilizing anchor  18 , a third stabilizing anchor  20 , a fourth stabilizing anchor  22 , a fifth stabilizing anchor  23 , a sixth stabilizing anchor  25 , a first anchor  24 , a second anchor  26 , a third anchor  28 , a fourth anchor  30 , a first transverse coupler  32 , a second transverse coupler  34 , and a plurality of fasteners  36 , such as bone screws or pedicle screws, for securing components of the system  10  to a spine  40  having a first side  40 A and a second side  40 B. 
     The system  10  is optionally used to bring the spine  40  to a more natural curvature (e.g., prior to or as a part of a single adjustment or multiple adjustments). In some embodiments, an abnormal curvature in the spinal column  40  has been adjusted to a more natural curvature using other instrumentation, prior to or in conjunction with securing portions of the system  10  to the spinal column  40 . In some embodiments, the system  10  is adapted to provide means for leveraged correction, with translation and derotation of the spine  40 . If desired, the system  10  is adapted to provide means for selective fusion of the spine  40  following correction. In other embodiments, the system  10  provides means for maintaining a correction to facilitate spinal remodeling in the absence of substantial vertebral fusion (e.g., without permanent vertebral fusion or without any vertebral fusion). 
     Although the system  10  is shown in  FIG. 1  with a selected number of components, such as six stabilizing anchors  16 ,  18 ,  20 ,  22 ,  23 ,  25 , four anchors  24 ,  26 ,  28 ,  30 , two transverse couplers  32 ,  34 , more or fewer components are implemented as appropriate. For example, in some embodiments, the system  10  includes the first rod  12 , the second rod  14 , a single transverse coupler, such as the first transverse coupler  32 , and a first anchor, such as the first anchor  24 , with the first rod  12  secured by the first transverse coupler  32  and the second rod  14  secured between the first transverse coupler  32  and the first anchor  24 . A variety of other configurations are also contemplated. 
     As shown in  FIG. 1 , the first rod  12 , also described as an elongate member, is secured to the spinal column  40  at a pre-selected offset from a longitudinal axis of the spinal column  40 . For example, the first rod  12  is optionally secured at an offset along a medial-lateral axis ML, or right-left axis, and anterior-posterior axis AP, or back-front axis. In some embodiments, the first rod  12  is secured on the left side of the spinal column  40  as shown. As subsequently described, the offset is optionally selected to cause at least a relative lateral translation (e.g., central or medial movement and/or anterior-posterior movement) and derotational shift (e.g., about a central axis of the spine) of selected vertebrae such that the spinal column  40  exhibits a more natural position. 
     The first rod  12  is elongate and cylindrical and includes a superior portion  50 , an intermediate portion  52 , and an inferior portion  54 , according to some embodiments. The first rod  12  is adapted, or otherwise structured, as desired, to extend along the spinal column  40 . The first rod  12  is optionally contoured to complement a desired spinal curvature. In some embodiments, the first rod  12  is substantially rigid, defining a substantially round cross-section with a mean diameter of about 6 mm and being formed of a suitable biocompatible material, such as titanium alloy ASTM F136, or cobalt chromium alloy ASTM F1537 or any other suitable implantable material. If desired, the first rod  12  incorporates some flex, or springiness while substantially rigidly retaining its shape. Though some material examples have been provided, the first rod  12  is optionally formed of a variety of materials, such as stainless steel or suitable polymeric materials and a variety of cross-sectional shapes. 
     The first rod  12  has a longitudinal axis X1—where the rod  12  is substantially straight, the longitudinal axis X1 is substantially straight and, where the rod  12  is substantially curved or angled, the longitudinal axis X1 is similarly curved or angled. The sections  50 ,  52 ,  54  of the first rod  12  are optionally continuously formed or are formed as separate, connected parts as desired. Expandable rod designs are also contemplated. 
     As shown in  FIG. 1 , the second rod  14  is substantially shorter than the first rod  12 . For example, the second rod  14  is optionally configured to extend along an apical region of the spine  40  and/or between a desired number of anchors, such as the first and second anchors  24 ,  26 . The second rod  14  is optionally formed of similar materials and with similar cross-section(s) to that of the first rod  12 , as desired. 
     As shown in  FIG. 1 , the first stabilizing anchor  16  and the first anchor  24  are adapted, or otherwise structured, to be mounted, or fixed to one or more vertebrae, such as vertebrae  41  and  42  located at or near inferior and apical regions, respectively, along the spine  40 . Additional examples of stabilizing anchors and anchors in accordance with some embodiments of the system  10  are set forth in U.S. application Ser. No. 13/301,514, filed on Nov. 21, 2011 and entitled TRANSVERSE CONNECTOR FOR SPINAL STABILIZATION SYSTEM, the entire contents of which are hereby incorporated by reference. 
       FIGS. 2 to 4  show the first transverse coupler  32  (also described as an anchor or connector) of the system  10 , according to some embodiments. As shown in  FIG. 2 , the first transverse coupler  32  is adapted, or otherwise structured, to be positioned laterally across a vertebra, such as the first apical vertebra  42  ( FIG. 1 ) located at or near the apex of the defective curvature along the spine  40 . As shown, the first transverse coupler  32  is designed to extend, either partially or fully, from the first side  40 A of the spine  40  to the second side  40 B of the spine  40 . 
       FIGS. 2 and 3  provide isometric views of the first transverse coupler  32 , according to some embodiments. As shown, the first transverse coupler  32  is adapted, or otherwise structured, to receive the first rod  12 , such that the first rod  12  is secured laterally relative to a portion of the first transverse coupler  32 . In some embodiments, the first rod  12  is substantially prevented from translating in a direction generally perpendicular to the longitudinal axis X1 at a first pivot point P1 while the rod  12  is able to slide axially, or translate axially, along the longitudinal axis X1 through the first pivot point P1 and also to change in pitch and yaw about the first pivot point P1. 
     In some embodiments, the first transverse coupler  32  is adapted, or otherwise structured, to substantially limit rotation, or roll, of the first rod  12  about the longitudinal axis X1 of the first rod  12 . According to some embodiments, the first transverse coupler  32  provides a means for allowing the rod  12  to angulate without substantial lateral translation relative to the portion of the first transverse coupler  32  and without substantial rotation about the longitudinal axis X1. 
     In some embodiments, the first transverse coupler  32  provides a means for selectively locking the first rod  12  to substantially prevent changes in axial translation, pitch, yaw, and/or roll. The selective locking feature is optionally suitable for constraining movement of the rod  12  under conditions associated with implantation of the system  10  and/or under conditions associated with spinal loading of the system  10  following implantation and securement of the system to the spine  40 . 
     The first transverse coupler  32  is optionally adapted secured to an anchor point on the second side of the spine. In some embodiments, the transverse coupler  32  is secured to an anchor point on the second side  40 B of the spine  40  where the anchor point is a spinal anchor directly secured to a vertebral body (not shown). For example, the spinal anchor is optionally a pedicle screw, hook or clamp. In some embodiments, the transverse coupler  32  is secured to an anchor point on the second side  40 B of the spine  40  where the anchor point includes a rod coupler configured to be secured to a second rod  14  extending longitudinally along a second side  40 B of a spine  40 . 
     In some embodiments, the first transverse coupler  32  is adapted to receive the second rod  14  such that the second rod  14  is secured laterally against lateral translation relative to a portion of the first transverse coupler  32 . In some embodiments, the second rod  14  is substantially prevented from translating in a direction substantially perpendicular to the longitudinal axis X2 at a second pivot point P2. In turn, in some embodiments, the second rod  14  is able to slide axially, or translate axially, along a second longitudinal axis X2, relative to the first transverse coupler  32  through a second pivot point P2. The second rod  14  is optionally able to change in pitch and yaw about the second pivot point P2. 
     The first transverse coupler  32  is optionally adapted, or otherwise structured, to substantially limit rotation, or roll, of the second rod  14  about the second longitudinal axis X2 of the second rod  14 . The first transverse coupler  32  provides means for allowing the second rod  14  to angulate without substantial lateral translation relative to the portion of the first transverse coupler  32  and without substantial rotation about the second longitudinal axis X2, according to some embodiments. 
     In some embodiments, the first transverse coupler  32  provides a means for selectively locking the second rod  14  to substantially prevent changes in axial translation, pitch, yaw, and/or roll. The selective locking feature is optionally suitable for constraining movement of the rod  14  under conditions associated with implantation of the system  10  and/or under conditions associated with spinal loading of the system  10  following implantation and securement of the system to the spine  40 . 
     The first transverse coupler  32  is optionally formed of suitable biocompatible metallic materials, such as titanium, titanium alloy ASTM F136, stainless steel, cobalt chromium alloy ASTM F1537, and/or suitable biocompatible polymeric materials, such as PEEK and/or composite materials. 
       FIG. 4  is an exploded view of the first transverse coupler  32 . As shown, the first transverse coupler  32  includes an adjustment assembly  60  (also described as an adapter or adjustor) adapted to be secured to a first rod  12  extending longitudinally along a first side  40 A of the spine  40 . According to some embodiments, the adjustment assembly  60  includes a rider  66 , an adjustment retainer  70 , and a first rod coupler  72  to receive the first rod  12 . As shown, the first transverse coupler  32  also includes an adjustment arm  62  adapted to be secured to the second rod  14  and extends from the first side  40 A of the spine  40  to a second side  40 B of the spine  40 , as well as a force directing member  64  having an elongate body  74  adapted to extend between the adjustment assembly  60  and the adjustment arm  62 . 
     As subsequently described, in some embodiments, the first rod coupler  72  is a multi-piece design (e.g. as shown in  FIGS. 2-8 ). In other embodiments, the first rod coupler  72  is a single-piece design adapted, or otherwise structured, for receiving the first rod  12  ( FIGS. 25-26 ). 
     As shown in  FIG. 4 , the adjustment assembly  60  connects to the force directing member  64  and the first rod  12 , which extends along the first side  40 A of the spine  40 . As shown in  FIG. 1  and  FIGS. 13-16 , the adjustment assembly  60  and force directing member  64  are optionally adapted to be positioned on the first side  40 A of the spine  40 . In some embodiments, the adjustment arm  62  is adapted to span across a portion of the first apical vertebra  42  (e.g., lamina-to-lamina or pedicle-to-pedicle on a single vertebra). 
       FIGS. 5-8  show features of the adjustment assembly  60 . As shown, the adjustment assembly  60  has a first rod coupler  72 , a rider  66  (also described as a slider or adjuster), and an adjustment retainer  70 , also described as a fastener or tightener (see  FIGS. 7 and 8 ). 
     As shown in  FIGS. 4-6 , the first rod coupler  72  of the adjustment assembly  60  includes a body  82  and a sleeve insert  84 . In some embodiments, the body  82  defines a sleeve aperture  88  extending through a first side  93  of the body  82  to a second side  94  of the body  82 . The sleeve aperture  88  is configured for receiving the sleeve insert  84 , according to some embodiments. In some embodiments, the sleeve aperture  88  is adapted to mate with the sleeve insert  84 , the sleeve insert  84  forming a revolute, substantially concave articulation surface  86 . In some embodiments, the sleeve insert  84  forms a revolute, substantially convex articulation surface  90  that complements the sleeve aperture  88 . The body  82  has also optionally has a pin chase  92  (e.g. a cylindrical through hole) that extends from the outer surface  96  of the body  82  to the articulation surface  86 . 
       FIG. 7  is a top plan view of the adjustment assembly  60  showing some of the internal features of the body  82 . As shown, the concave articulation surface  86  of the aperture  88  is adapted, or otherwise structured, to form a substantially complementary fit with the sleeve insert  84 . In some embodiments, the sleeve insert  84  is able to be captured by the body  82  within the aperture  88  and have relative angular movement with respect to the body  82 . 
     In some embodiments, the sleeve insert  84  has a passage  98  defining a pivot point P1 through which a portion of the first rod  12  is able to be received. As shown, the pivot point P1 is defined in the passage, where, upon assembly, the first rod  12  passes through the first pivot point P1 such that the longitudinal axis X1 of the rod  12  at the first pivot point P1 is generally concentric with the center of the passage. 
     As shown, the sleeve insert  84  has a smooth bore  100  for receiving the first rod  12 . In some embodiments, the sleeve insert  84  is adapted to help allow the first rod  12  to pass through the passage  98  at the first pivot point P1, where the passage  98  helps allow the rod  12  to angulate about the longitudinal axis X1 at the first pivot point P1 (shown in  FIGS. 2, 3, 6, and 8 ) while rotation and lateral translation of the first rod  12  with respect to the first rod coupler  72  is substantially limited in all planes. In alternative terms, the first rod coupler  72  of the adjustment assembly  60  is configured to be substantially laterally constrained by a first rod  12  when the first rod coupler  72  receives the first rod  12 . The first rod coupler  72  selectively locks rotation of the first rod  12  while helping to allow the first rod  12  to axially translate through the first rod coupler  72  and to pivot in pitch and yaw at the first pivot point P1, according to some embodiments. 
     As shown in  FIGS. 4, 6, and 8 , in some embodiments, the body  82  also includes a first protrusion  102  (e.g., a pin) or protrusions (not shown) that extend inwardly into the aperture  88  from the articulation surface  86 . The first protrusion  102  is optionally a pin with a head  104 , a neck  106 , and a body  108 , the neck  106  being located between the head  104  and the body  108  (see  FIG. 4 ). The head  104 , the neck  106 , and the body  108  are optionally substantially cylindrical with the head  104  having a greater diameter than the body  108  and the body  108  having a greater diameter than the neck  106 . The first protrusion  102  is optionally received in the pin chase  92  such that the head  104  projects into the aperture  88 . In some embodiments the first protrusion  102  and/or body  108  is press fit into the pin chase  92  and/or welded, adhered, or otherwise secured within the pin chase  92 . In some embodiments, the first protrusion is temporary and is removable in association with an implantation procedure, providing temporary prevention of roll of the sleeve insert  84  within the body  82  before, during, and/or after securing the system  10  to the spine  40 , for example. 
     As shown, the body of the first rod coupler  72  also includes a locking portion  120 . In some embodiments, the locking portion  120  has an upper portion  122  and a lower portion  124  separated by a gap  126  ( FIG. 6 ). In some embodiments, the upper portion  122  has a through slot  125  ( FIG. 6 ) that helps allow a locking member  128  (e.g., a male threaded bolt) to slidably pass through the upper portion  122 . The lower portion  124  optionally has a bore (e.g., a female threaded bore), at least partially extending through the lower portion  124 . The upper portion  122  and the lower portion  124  can optionally be locked, or clamped, together with the locking member  128  secured across the gap  126 . In some embodiments, the locking portion  120  of the first rod coupler  72  is adapted to lock the sleeve insert  84  within the body  82  of the first rod coupler  72 . 
     In some embodiments, the locking portion  120  is adapted to lock the first rod  12  to the first rod coupler  72 . As shown in  FIG. 4 , the sleeve insert  84  has a gap  132  that facilitates locking of the sleeve insert  84  onto the first rod  12 . For example, in some implementations, upon sufficiently tightening the locking member  128 , the sleeve insert  84  is locked onto rod  12  to arrest axial translation of the rod  12  through the sleeve insert  84 . In some implementations, the locking action of the body  82  on the sleeve insert  84  arrests changes in pitch and yaw. In different terms, the rod  12  is able to be selectively locked relative to the first transverse coupler  32  to substantially prevent changes in axial translation, pitch, yaw, and/or roll as desired. 
     The first rod coupler  72  defines a rod pivot point P1 and is optionally configured to be transitioned from an unlocked state in which a first rod  12  received by the first rod coupler  72  is able to axially translate and change in pitch and yaw about the first rod pivot point P1 to a locked state in which the first rod  12  received by the first rod coupler  72  is locked against axial translation and changes in pitch and yaw about the rod pivot point. When the first rod coupler  72  receives the first rod  12 , the first rod coupler  72  is substantially laterally constrained by the first rod, according to some embodiments. 
     As shown in  FIGS. 5-8 , the rider  66  (also described as slider or adjuster) includes a first surface  110  and a second surface  112  connected by a lateral wall  114 . In some embodiments, the rider  66  is substantially oval-shaped and extends from the lower portion  124  of the locking portion  120 . As shown, the first surface  110  of the rider  66  faces generally away from the adjustment arm  62 . During operation, the adjustment retainer  70  abuts the first surface  110  of the rider  66  and moves the rider  66  along the force directing member  64 , according to some embodiments. Although the adjustment retainer  70  is shown on the rider  66 , it should be understood that the adjustment retainer  70  and the rider  66  are not a single unit, but are separate, relatively moveable components, according to some embodiments. As shown, the second surface  112  of the rider  66  faces generally toward the adjustment arm  62 . During operation, the second surface  112  of the rider  66  engages with the adjustment arm  62  when the adjustment assembly  60  is moved along the force directing member  64  and brought in contact with the adjustment arm  62 , according to some embodiments. 
     As shown in  FIG. 6 , the rider  66  also includes a slot  116  extending through the rider  66  from the first surface  110  to the second surface  112 . As shown, the slot  116 , also described as an articulation aperture, has an elongate transverse cross-section. In some embodiments, the slot  116  is configured to receive the elongate body  74  of the force directing member  64  such that the elongate body  74  of the force directing member  64  is adjustable within the slot  116  in the direction in which the slot  116  is elongated. In operation, the rider  66  is optionally moveable along the force directing member  64  by, for example, moving the rider along the force directing member. The slot  116  is optionally configured to help allow the force directing member  64  extend through the rider  66  at a substantially orthogonal angle relative to the second surface of the rider  66 , as well as a variety of additional angles as desired. For example, the slot  116  is optionally configured to help allow the force directing member  64  to angulate, or pivot, within the slot  116  such that the force directing member extends through a plurality of angles (e.g., orthogonal and non-orthogonal) relative to the second surface  112  of the rider  66 . In some embodiments, the slot  116  is configured to allow the force directing member  64 , but not the adjustment retainer  70  to extend through the slot  116  of the rider  66 . Consequently, the adjustment retainer  70  abuts the first surface  110  of the rider  66  adjacent the slot  116  and does not extend through the slot  116  of the rider  66 , according to some embodiments. 
     As shown in  FIGS. 7 and 8 , the adjustment retainer  70  is configured to couple to the force directing member  64 . The adjustment retainer  70  is configured to travel along the force directing member  64  in a direction of a central axis defined by the elongate body  74  of the force directing member  64  as desired. In some embodiments, the adjustment retainer  70  is a threaded cap  130  (e.g., a female threaded nut) configured to mate with and be screwed down the length of the force directing member  64 , pressing against the rider  66 , and thereby helping to move the rider  66  along the force directing member  64  as the adjustment retainer  70  is actuated along the force directing member  64 . 
       FIGS. 2-4  show features of the force directing member  64  (also described as a connector), according to some embodiments. In some embodiments, the force directing member  64  includes the elongate body  74  and extends from a first end  140  and a second end  142 . In other embodiments, the elongate body includes a head portion with a pocket configured to receive a rod, for example, a rod-shaped portion of the rider and/or adjustment arm (not shown). In some embodiments, the force directing member  64  includes a threaded, elongate body  74  adapted to mate with the threaded cap  130  of the adjustment retainer  70 . Alternatively, in some embodiments, the elongate body  74  has teeth, barbs or stepped features along the elongate body  74  adapted to mate with teeth, barbs, or complementary features of the adjustment retainer  70 . Some examples of the force directing member  64  optionally include, but are not limited to, a threaded screw, a standard bolt, a toggle bolt, a female threaded partial tube, a cable tie, a zip tie, a peg fastener or other type of selectively adjustable mechanism. 
     The first end  140  of the force directing member  64  is optionally adapted to be received within an aperture  144 , also described as an articulation aperture or a socket, of the adjustment arm  62 . In some embodiments, the first end  140  of the force directing member  64  is adapted to allow the force directing member  64  to change in pitch, yaw and roll from within the aperture  144 . As shown in  FIG. 2 , the first end  140  is generally spherically shaped and is adapted to fit within the aperture  144 . In some embodiments, the first end  140  of the force directing member  64  is adapted to substantially limit the force directing member  64  from substantially changing in pitch, yaw and roll from within the aperture  144 . The first end  140  of the force directing member  64  is optionally a generally polygon-shaped end. For example, a force directing member  64  with a square-end, when fit into a complementary polygon-shaped aperture of the adjustment arm  62 , is substantially prevented from changing in pitch, yaw, and roll from within the aperture. Alternatively, a force directing member can optionally include a cylinder-end, e.g. a T-shaped first end, which when fit into a complementary shaped aperture of the adjustment arm  62 , is substantially prevented from changing in pitch, but allows changes in yaw and roll from within the aperture. 
     The force directing member  64  is adapted to be secured to the adjustment assembly  60  and the adjustment arm  62  such that the elongate body  74  of the force directing member  64  extends between the rider  66  of the adjustment assembly  60  and the adjustment arm  62 , according to some embodiments. The first force directing member  64  has the elongate body  74  optionally defining an effective length L ( FIGS. 13 and 14 ) between the rider  66  of the adjustment assembly  60  and the adjustment arm  62 . Alternatively, the elongate body  74  may optionally define the effective length L as the distance between a second surface  112  of the rider  66  and the first end  140  of the force directing member  64  (not shown). The effective length L is dependent on the position of the adjustment retainer  70  along the force directing member  64 , according to some embodiments. An effective angle α ( FIGS. 17 and 19 ) between the force directing member  64  and a first surface  160  (shown in  FIG. 9 ) of the adjustment arm  62  is optionally dependent on the position of the first and second rods  12 ,  14 . As the adjustment retainer  70  is engaged, or rotated clockwise (for right hand threaded components), along the force directing member  64 , the effective length L is shortened and the angle α is increased as desired (for example, see α1 in  FIG. 17 ). If the adjustment retainer  70  is disengaged, or rotated counter-clockwise (for right hand threaded components), the effective length L is lengthened and the angle α is decreased as desired (for example, see α2 in  FIG. 19 ). Although a screw, or threaded, adjustment mechanism is shown, a variety of alternative adjustment mechanisms (e.g., a pawl and ratchet system) are contemplated. 
       FIGS. 9-12  show features of the adjustment arm  62  (also described as a transverse connector or arm), according to some embodiments. The adjustment arm  62  is optionally configured to extend from a first side  40 A of the spine  40  to a second side  40 B of the spine  40 . As shown, the adjustment arm  62  includes a second rod coupler  150 , a connecting portion  152 , and a base portion  154 , the adjustment arm having a first end  156 , a second end  158 , the first surface  160 , a second surface  162 , and a longitudinal axis X3 extending from the first end  156  to the second end  158 . 
     As shown, the connecting portion  152  of the adjustment arm  62  has an elongate body  164  that extends from the base portion  154  to the second rod coupler  150 . In some embodiments, the first surface  160  of the adjustment arm  62  faces generally toward the adjustment assembly  60  and the second surface  162  of the adjustment arm  62  faces generally away the adjustment assembly  60 . In operation, the first surface  160  of the adjustment arm  62  also engages with the adjustment assembly  60  when the adjustment assembly  60  is moved along the force directing member  64  and brought in contact with the adjustment arm  62 , according to some embodiments. 
       FIG. 9  is a side view of the adjustment arm  62 , according to some embodiments. As shown, the second end  158  of the adjustment arm  62  includes the second rod coupler  150 , which is configured to be secured to a second rod  14  extending longitudinally along a second side  40 B of a spine  40 . In some embodiments, the second rod coupler  150  of the adjustment arm  62  is substantially similar to the first rod coupler  72  of the adjustment assembly  60 , with the exception that the second rod coupler  150  receives the second rod  14 . The second rod coupler  150  of the adjustment arm  62  is optionally configured to substantially limit roll of the second rod  14  where the second rod  14  is received by the second rod coupler  150 . As shown in  FIG. 9 , the second rod coupler  150  is adapted to be substantially laterally constrained by the second rod  14  with the second rod  14  being able to axially translate through the second rod coupler  150  and to pivot in pitch and yaw at the second rod coupler  150  at a second pivot point P2. 
     As shown in  FIG. 4 , a body  168  of the second rod coupler  150  also includes a second protrusion  166  (e.g., a pin) or protrusions (not shown) that extends inwardly into the aperture from the articulation surface  148 . In some embodiments, the second protrusion  166  is substantially similar to the first protrusion  102  of the first rod coupler  72 , discussed previously herein, and substantially prevents a sleeve insert  182  from rolling within the body  168  of the second rod coupler  150 . 
     As shown in  FIG. 9 , the second rod coupler  150  of the adjustment arm  62  includes a locking mechanism similar to the first rod coupler  72 . In some embodiments, the locking portion  170  has a first portion  172  and a second portion  174  separated by a gap  176 . The first portion  172  and the second portion  174  can be locked, or clamped, together with the locking member  180  is secured into a through slot  178  and across the gap  176 , according to some embodiments. As shown, the sleeve insert  182  also has a gap  184  ( FIG. 4 ) that facilitates locking of the sleeve insert  182  onto the second rod  14 . For example, upon sufficiently tightening the locking member  180 , the sleeve insert  182  is optionally locked onto rod  14  to substantially arrest axial translation of the second rod  14  through the sleeve insert  182 . In some embodiments, the locking action of the body  168  of the second rod coupler  150  on the sleeve insert  182  substantially arrests changes in pitch and yaw. In different terms, the second rod  14  is able to be selectively locked relative to the first transverse coupler  32 , in accordance with some embodiments. The selective locking feature is optionally suitable for constraining movement of the rod  14  under conditions associated with implantation of the system  10  and/or under conditions associated with spinal loading of the system  10  following implantation and securement of the system to the spine  40 . 
     As mentioned previously and as shown in  FIGS. 10 and 11 , the first end  156  of the adjustment arm  62  includes an articulation aperture  144  extending from the first surface  160  to the second surface  162 . In some embodiments, the articulation aperture  144  is adapted to receive the force directing member. The articulate aperture  144  has a revolute, substantially concave inner surface with an elongate opening extending in the direction of the longitudinal axis X3 ( FIGS. 10-12 ). 
     As shown in  FIGS. 13-16 , the elongate body  74  of the force directing member  64  extends from the first surface  160  of the adjustment arm  62  at an angle relative to the longitudinal axis X3. In some embodiments, the force directing member  64  extends from first surface  160  of the adjustment arm  62  at an adjustable angle relative to the longitudinal axis X3. The angle may be, for example, optionally adjusted to any angle between 0 to 90 degrees. In some embodiments, the force directing member  64  is rigidly secured to the first end  156  of the adjustment arm  62  and extends from the first surface  160  of the adjustment arm  62  at a substantially fixed angle relative to the longitudinal axis. In some embodiments, the elongate body  74  of the force directing member  64  extends from the first surface  160  of the adjustment arm  62  at a substantially orthogonal angle relative to the longitudinal axis X3. 
     In some embodiments, the spherically shaped first end  140  of the force directing member  64  fits within an articulation aperture  144 . The first end  140  of the force directing member  64  is optionally received within the articulation aperture  144  ( FIGS. 10 and 11 ) of the adjustment arm  62  such that the force directing member  64  is able to angulate. In some embodiments, the force directing member  64  is substantially free to angulate in a first plane of angulation A1 ( FIGS. 13 and 15 ) to a greater degree than in other planes of angulation (e.g., a second plane of angulation A2 as shown in  FIGS. 14 and 16 ). The first plane of angulation A1 is depicted as a line ( FIGS. 14 and 16 ). The first plane A1 is defined by the longitudinal axis X3 and the normal axis X4 of the transverse coupler, both falling within the first plane A1. The first plane A1 is generally orthogonal to the second plane A2 while being generally parallel to the longitudinal axis X3 and the normal axis X4. The second plane of angulation A2 is depicted as a line ( FIGS. 13 and 15 ), where the first plane A1 extends orthogonally from the second plane A2. The normal axis X4 falls within the second plane A2, the normal axis X4 being generally parallel the second plane A2. In some embodiments, the force directing member  64  is substantially free to angulate in a single plane of angulation (e.g., the first plane A1) or multiple planes of angulation (e.g., the first plane A1 and the second plane A2) as desired. 
     In some embodiments, the force directing member  64  is received within the articulation aperture of the adjustment arm  62  such that the force directing member  64  is able to angulate. The force directing member  64  is able to optionally articulate in a first plane of angulation A1 to a greater extent than the force directing member  64  is able to angulate in a second plane of angulation A2 that is substantially perpendicular to the first plane of angulation. In some embodiments, the force directing member  64  has an angulation range of 90 degree, wherein the force directing member  64  is able to articulate through an angle of about 45 degrees or more in the first plane of angulation A1. The force directing member  64  optionally articulates in the first plane of angulation A1 and is substantially prevented from articulating in the second plane of angulation A2. It is also contemplated that the force directing member  64  is able to articulate in a multiple planes of angulation, according to some embodiments. 
       FIGS. 17-19  show a view of the system  10  taken in a transverse plane to the spine  40  near the apex of the defective curvature, with some inferior and superior portions of the spine  40  and system  10  not shown to simplify illustration. As shown, the transverse coupler  32  is secured to the first apical vertebra  42  and to the first and the second rods  12 ,  14 . In sequentially viewing the Figures, it can be seen that during operation, the vertebrae  42  is laterally translated and derotated while the transverse coupler  32  is being adjusted, according to some methods of using the system  10 . After the adjustment, the first apical vertebra  42  is then locked against further rotation or lateral movement by locking the transverse coupler  32  to both the first and the second rods  12 ,  14 , according to some embodiments.  FIGS. 17 and 18  show the vertebra  42  in an uncorrected state, or a partially derotated and laterally offset state with the first and the second rods  12 ,  14  secured in first and the second rod couplers  72 ,  150  of the first transverse coupler  32 . 
     In order to secure the first rod  12  onto the spine  40 , the first and second stabilizing anchors  16 ,  18  are optionally secured at an inferior spinal position, or level, (e.g., to an inferior vertebrae) and a superior spinal position, or level (e.g., to a superior vertebrae), respectively. In some embodiments, the first rod  12  is substantially laterally constrained by the first and second stabilizing anchors  16 ,  18  such that the first rod  12  extends longitudinally on the first side  40 A of the spine  40  and is laterally constrained relative to the inferior and superior vertebrae. 
     The second rod  14  is optionally secured on an opposite side of the spine at intermediate positions along the spine by a first intermediate anchor and a second intermediate anchor, for example. The first and second intermediate anchors are adapted to substantially constrain the second rod  14  against substantial lateral translation as desired. The first intermediate anchor (e.g., the fifth stabilizing anchor  23  as shown in  FIG. 1 ) is optionally secured to a first, intermediate vertebrae and a second, intermediate vertebrae, each located between the superior and inferior vertebrae to which the first and second stabilizing anchors are secured. In some embodiments, the first and second intermediate anchors are secured to vertebral bodies located on or adjacent vertebral bodies that form an apex, or apical region of the deformity. As shown in  FIG. 1 , with the spine  40  in a generally corrected state, the first intermediate anchor is positioned at a lower vertebral position, or level than the adjustment assembly  60  and at a higher vertebral position, or level than the first stabilizing anchor  16 . In turn, the second intermediate anchor (e.g., the sixth stabilizing anchor  25 ), is optionally positioned along the spine  40  at a higher vertebral position, or level along the second rod  14  between the adjustment assembly  60  and the second stabilizing anchor  18 . 
     In order to assemble the transverse coupler  32  onto the system  10  ( FIG. 1 ), a physician can optionally articulate components of the transverse coupler  32  (e.g. the force directing member  64  and the adjustment assembly  60 ), such that the rod couplers  72 ,  150  of the transverse coupler  32  are able to reach the first and the second rods  12 ,  14 . Alternatively or additionally, a physician or other user can optionally employ a variety of tools and associated methods. For example, the user can optionally use a surigical tool, such as a wrench, clamp, or gripping tool, compressor, distractor adapted to couple to the first rod  12 , the second rod  14 , the first transverse coupler  32 , and/or other spinal devices. The tool is used to assist the physician in derotating and/or translating the spinal column  40  during a correction as desired. The tool is optionally used to assist the physician in maintaining a desired configuration while assembling the system  10  onto the spine  40 . 
     As shown in  FIG. 17 , the first transverse coupler  32  is assembled onto the first apical vertebra  42 . During assembly, the first and the second rod couplers  72 ,  150  of the first transverse coupler  32  are optionally adjusted to an unlocked state when coupled to the first and the second rods  12 ,  14  respectively, such that the physician has free movement as desired, when assembling the transverse coupler  32  onto the spine  40 . In some embodiments, the first and the second rod couplers  72 ,  150  are adjusted to an unlocked state to reduce binding of the rods  12 ,  14  and to provide more degrees of freedom to the first transverse coupler  32  during the lateral translation and derotation of the spine. 
     During or after assembly, the transverse coupler  32  is optionally adjusted to a locked state onto the rods  12 ,  14  of the system  10  to allow for lateral translation and derotation of the first apical vertebra  42 . In some embodiments, the first and the second rods  12 ,  14  are generally locked against rotation roll within the corresponding couplers  72 ,  150  of the first transverse coupler  32 , as previously discussed herein. The first rod  12  is optionally left unlocked within the first rod coupler  72  while the second rod  14  is locked against axial translation and changes in pitch and yaw within the second rod coupler  150 . In some embodiments, the first rod  12  is able to change in pitch and yaw, while the second rod  14  is substantially constrained against changes in pitch, yaw, and roll during at least a portion of the correction. 
     In some embodiments, the first rod  12  is able to axially translate and change in pitch and yaw about the first pivot point P1 while the vertebra  42  is being laterally translated and derotated during the full duration of the correction. In other embodiments, the first rod  12  is locked against changes in pitch and yaw during a portion of the correction and/or after the correction.  FIGS. 17-19  depict a use of the transverse coupler  32  such that the first rod  12  is able to change in pitch, yaw, and axial translation during a correction and is locked against changes in pitch, yaw, and axial translation after the correction, according to some embodiments. 
       FIG. 18  shows the first apical vertebra  42  in a partially derotated and a laterally offset state and  FIG. 19  shows the first apical vertebra  42  in a maximally derotated and laterally translated state, according to some embodiments. The first transverse coupler  32  operates to laterally translate and rotate the second rod  14  towards the first rod  12  such that a portion of the spine  40  is moved into a more correct configuration, in accordance with some embodiments. For example, comparing  FIG. 19  to  FIG. 17 , it can be seen that the distance between the first rod  12  and the second  14  has significantly shortened (identified as D1 and D2 in  FIGS. 17 and 15 ) after the correction. Shown by an arrow in the Figures, the first transverse coupler  32  is optionally adapted to derotate the vertebra  42  and laterally translate the vertebra  42 , either contemporaneously, sequentially, or combinations thereof. 
       FIG. 19  shows the first apical vertebra  42  maximally derotated and laterally translated. The transverse coupler  32  is optionally locked after the vertebra  42  has been laterally translated and derotated as desired (e.g., as shown in  FIG. 19 ), to prevent relative translational and rotational movement between the first rod  12  and second rod  14  to stabilize and hold the vertebra  42  in the corrected position. Additional anchors  23 ,  25 ,  28 ,  30  are added to the spine  40  as desired to provide additional stability to the spine  40 . In some embodiments, after the vertebra  42  has been laterally translated and/or partially derotated and the transverse coupler  32  has been locked to the rods, the adjustment retainer  70  is actuated along the force directing member  64  to derotate, or further derotate, the spine  40 . 
     An illustrative but non-limiting example of correcting a spinal defect includes securing the first stabilizing anchor  16  at an inferior spinal position and the second stabilizing anchor  18  at a superior spinal position along the first side  40 A of the spine  40 . The first rod  12  is extended longitudinally on the first side  40 A of the spine  40  and is substantially laterally constrained between the first and the second stabilizing anchors  16 ,  18 , according to some embodiments. 
     The first anchor  24  is optionally secured at an inferior spinal position and the second anchor  26  is secured at the superior spinal position along the second side  40 B of the spine  40 . The second rod  14  extends longitudinally on the second side  40 B of the spine  40  and is substantially laterally constrained between the first and the second anchors  24 ,  26 , according to some embodiments. 
     The first transverse coupler  32  is optionally assembled onto the first and the second sides  40 A,  40 B of the spinal column  40 , either at some time prior to, during, or after securing the stabilizing anchors  16 ,  18 ,  24 ,  26  to the spine  40 . In some embodiments, the transverse coupler  32  is assembled onto the first side  40 A of the spine  40  by coupling the first rod coupler  72  of the adjustment assembly  60  to the first rod  12 . The first rod  12  is able to axially translate and change in pitch and yaw, but is substantially restricted from lateral translation at the first rod coupler  72 , according to some embodiments. 
     The transverse coupler  32  is optionally assembled onto the second side  40 B of the spine  40  by coupling the second rod coupler  150  of the adjustment arm  62  to the second rod  14 . In some embodiments, the second rod  14  is locked from axial translation and changing in pitch, yaw and roll at the second rod coupler  150 . The adjustment arm  62  of the first transverse coupler  32  is positioned across the first apical vertebra  42  such that a connecting portion  152  of an adjustment arm  62  extends from the first side  40 A of the spine  40  to the second side  40 B of the spine  40 , according to some embodiments. 
     As previously discussed, the first transverse coupler  32  includes the force directing member  64  that is optionally the threaded toggle bolt. The force directing member  64  is optionally secured to the adjustment assembly  60  and the adjustment arm  62  with an initial effective length. 
     In some embodiments, an adjustment retainer  70  is actuated along the force directing member  64  by rotating the threaded cap  130  of the adjustment retainer  70  clockwise along a threaded portion of the force directing member  64 . Actuating the retainer  70  decreases the effective length L as desired. In some embodiments, the effective length L becomes approximately zero when the adjustment arm  62  becomes seated flush against the adjustment assembly  60 . The force directing member  64  is optionally cut or broken off to a shorter length, as desired, during the procedure as the effective length L decreases from the initial effective length. 
     As the adjustment retainer  70  is optionally actuated along the force directing member  64 , the rider  66  provides a resistance force that transmits through the force directing member  64  to the adjustment arm  62 . In some embodiments, the resistance force causes the second rod  14  to move towards the first rod  12 , which laterally translates a portion of the spine  40  towards the first rod  12 . 
     In some embodiments, the adjustment retainer  70  is actuated along the first force directing member  64  such that the first surface  160  of the adjustment arm  62  comes into contact with the adjustment assembly  60 . The adjustment retainer  70  is then optionally further actuated to pivot the rider  66  and the adjustment arm  62  towards each other such that the first surface  160  of the adjustment arm  62  becomes seated flush against the second surface  112  of the rider  66 . In some embodiments, the adjustment assembly  60  receives the force directing member  64  within an articulation aperture  144  having an elongate transverse cross-section, allowing the force directing member  64  to articulate in the first plane of angulation as the adjustment retainer  70  is driven along the first force directing member  64 . As the adjustment assembly  60  and the adjustment arm  62  impinge and ultimately become seated together, the force directing member  64  articulates into a generally orthogonal angle relative to the longitudinal axis X3 defined by the adjustment arm  62 , according to some embodiments. In some embodiments, as the force directing member  64  articulates, the first apical vertebra  42  derotates. Once the adjustment arm  62  and the adjustment assembly  60  are brought into the desired amount of contact or the desired effective length L of the force directing member  64  has been achieved. 
       FIG. 20  shows an isometric view of an alternative embodiment of a first transverse coupler  200  of the system  10 , also described as a transverse connector. The first transverse coupler  200  is optionally adapted, or otherwise structured, to be positioned laterally across one or more of the vertebrae, such as the first apical vertebra  42  ( FIG. 1 ) located at or near an apical position along the spine  40 . As shown, the first transverse coupler  200  is adapted to extend from the first side  40 A of the spine  40  toward, and ultimately across to the second side  40 B of the spine  40 . 
     As shown, the first transverse coupler  200  includes features that are substantially similar to the first transverse coupler  32 . In some embodiments, the adjustment arm  202  is substantially similar to the adjustment arm  62  of the first transverse coupler  32 , and thus various features of the adjustment arm  62  of the first transverse coupler  32  also apply to the adjustment arm  202  of the first transverse coupler  200 . 
     As shown in  FIG. 20 , the first transverse coupler  200  includes an adjustment assembly  250  adapted to be secured to a first rod  12 . In some embodiments, the adjustment assembly  250  includes a rider  252 , an adjustment retainer  254 , and a first rod coupler  256  to receive the first rod  12 . 
       FIGS. 21-23  show a top, a side and a rear view of the first transverse coupler  200 . In some embodiments, the rider  252  and the adjustment retainer  254  of the first transverse coupler  200  engage with an adjustment arm  202  and/or a force directing member  204  in a manner substantially similar to the rider  66  and adjustment retainer  70  of the first transverse coupler  32 . The various features of the rider  66  and the adjustment retainer  70  of the first transverse coupler  32  also apply to the rider  252  and the adjustment retainer  254  of the first transverse coupler  200 . The main difference between the first transverse coupler  200  and the first transverse coupler  32  is the first rod coupler  256 , according to some embodiments. 
     As shown in  FIGS. 20 and 23 , the first rod coupler  256  includes a head portion  258  is substantially U-shaped having a first prong  262  and a second prong  264  defining a pocket  266  for receiving the first rod  12 . The head portion  258  of the adjustment assembly  250  serves to couple the first transverse coupler  200  to the first rod  12 . As shown, the prongs  262 ,  264  are threaded for receiving a clamping screw  268  adapted to engage and secure the first rod  12  immobilized within the pocket  266 . The first rod coupler  256  of the adjustment assembly  250  is optionally configured to receive the first rod  12  such that the first rod  12  is free to change in at least roll within the first rod coupler  256 . In some embodiments, first rod coupler  256  is configured to receive the first rod  12  such that the first rod  12  is free to change in pitch and roll, but is substantially limited from changes in yaw within the first rod coupler  256 . In some embodiments, the first rod coupler  256  is configured to be transitioned from an unlocked state in which the first rod  12  is free to move in at least one of slide, pitch, yaw or roll with respect to the first rod coupler  256  to a locked state. In some embodiments, the first rod  12  is received by the first rod coupler  256  such that the first rod coupler  256  becomes substantially laterally constrained by the first rod  12 . The first rod coupler  256  optionally locks the first rod  12  against axial translation, changes in pitch, yaw and roll about a rod pivot point with respect to the first rod coupler  256 . 
       FIG. 24  provides another alternative embodiment of the first transverse coupler  300 , which includes an adjustment assembly  350  adapted to be secured to a first rod  12 . In some embodiments, the adjustment assembly  350  includes a rider  352 , an adjustment retainer  354 , and a first rod coupler  358  to receive the first rod  12 . The first rod coupler  358  optionally receives the first rod  12  in a substantially similar manner to the adjustment assembly  250  of the first transverse coupler  200 , and therefore various features of the adjustment assembly  250  of the first transverse coupler  200  also apply to the adjustment assembly  350  of the first transverse coupler  300 . The primary difference between the first transverse coupler  300  and the first transverse coupler  200  is the design of the second rod coupler  312  of the adjustment arm  302 , according to some embodiments. 
     As shown in  FIG. 24 , the adjustment arm  302  is substantially similar to the adjustment arm  62  of the first transverse coupler  32  with a difference of having a second rod coupler  312  that includes a U-shaped head portion  314 . The head portion  314  is substantially U-shaped and includes a first prong  306  and a second prong  308  that defines a pocket  310  for receiving the second rod  14 . The head portion  314  of the adjustment arm  302  serves to couple the first transverse coupler  300  to the second rod  14 . As shown, the prongs  306 ,  308  are optionally threaded for receiving a clamping screw (not shown) adapted to engage and secure the second rod  14  immobilized within the pocket  310 . The second rod coupler  312  receives the second rod  14  similar to how the first coupler  356  receives the second rod  14 , and therefore those various features of the first rod coupler  256  are also applicable to the second rod coupler  312  with respect to the second rod  14 . 
       FIG. 25  shows an isometric view of another first transverse coupler  400  of the system  10 , also described as a fixed transverse coupler. The first transverse coupler  400  is optionally adapted, or otherwise structured, to be positioned laterally across one or more of the vertebrae, such as the first apical vertebra  42  ( FIG. 1 ) located at or near an apical position along the spine  40 . As shown, the first transverse coupler  200  is adapted to extend from the first side  40 A of the spine  40  toward, and ultimately across to the second side  40 B of the spine  40 . 
     As shown, the first transverse coupler  400  includes features that are substantially similar to the first transverse coupler  32 . In some embodiments, the first transverse coupler  400  includes an adjustment assembly  450  adapted to be secured to a first rod  12 . In some embodiments, the adjustment assembly  450  includes a rider  452 , an adjustment retainer  454 , and a first rod coupler  456  to receive the first rod  12 . In some embodiments, the adjustment assembly  450  is substantially similar to the adjustment assembly  60  of the first transverse coupler  32 . 
     The first transverse coupler  400  optionally includes an adjustment arm  402  with a second rod coupler  412  adapted to be secured to the second rod  14  and extends from the first side  40 A of the spine  40  to the second side  40 B of the spine  40 . In some embodiments, the adjustment arm  402  has a first end  406  and a second end  408  and a longitudinal axis X3 extending between the first and the second ends  406 ,  408 . The adjustment arm  402  optionally has a first surface  414  and a second opposite surface  416  ( FIG. 26 ). 
       FIG. 26  shows a view of the adjustment arm  402 , with some features not shown to facilitate understanding, which is substantially similar to the adjustment arm  62  of the first transverse coupler  32  with a difference of having a force directing member  404  rigidly secured to the first end  406  of the adjustment arm  402 . In some embodiments, the force directing member  404  extends from the first surface  414  of the adjustment arm  402  at a generally orthogonal angle relative to the longitudinal axis X3. In other embodiments, the force directing member  404  extends from the first surface  414  of the adjustment arm  402  at a non-orthogonal angle relative to the longitudinal axis X3. The force directing member  404  has an elongate body  410  extending between the adjustment assembly  450  and the adjustment arm  402 , according to some embodiments. 
     The adjustment arm  402  optionally includes an elongated portion  418  with an aperture  420  at the first end  406  of the adjustment arm  402 . The aperture  420  is optionally adapted to receive at least a portion of a surgical tool that may be used during the implant procedure to obtain and hold a spinal correction. 
       FIGS. 27-29  show a view of the system  10  taken in a transverse plane to the spine  40  near the apex of the defective curvature, with some inferior and superior portions of the spine  40  and system  10  not shown to simplify illustration. As shown, the transverse coupler  400  is secured to the first apical vertebra  42  and to the first and the second rods  12 ,  14 . In sequentially viewing the Figures, it can be seen that during operation, the first apical vertebra  42  is laterally translated and derotated while the transverse coupler  400  is being adjusted, according to some methods of using the system  10 .  FIGS. 27 and 28  show the first apical vertebra  42  in a partially derotated and a laterally offset state and  FIG. 29  shows the first apical vertebra  42  maximally derotated and laterally translated. 
     In order to assemble the transverse coupler  400  onto the system  10  ( FIG. 1 ), a physician can optionally angulate the adjustment assembly  450  of the transverse coupler  200  (e.g.) such that the rod couplers  456 ,  412  of the transverse coupler  400  are able to reach the first and the second rods  12 ,  14 . Alternatively or additionally, a physician or other user can optionally employ a variety of tools and associated methods. For example, the user can use a surgical tool, such as a wrench, clamp, or gripping tool, adapted to couple to the first rod  12 , the second rod  14 , the first transverse coupler  400 , and/or other spinal devices as desired. In some embodiments, the surgical tool optionally assists the physician in derotating and/or translating a spinal column  40  during a correction. The surgical tool optionally assists the physician in maintaining a desired configuration while assembling the system  10  onto the spine  40 . 
     A spinal correction using the first transverse coupler  200  as shown in  FIGS. 27-29  optionally proceeds similarly to the spinal correction using the transverse coupler  32  as shown in  FIGS. 13-16 . 
     An illustrative but non-limiting example of correcting a spinal defect using the first transverse coupler  400  is provided herein. Stabilizing anchors  16 ,  18 , anchors  24 ,  26 , and rods  12 ,  14  are optionally secured to the spine  40  using the operation as discussed previously. 
     The first transverse coupler  200  is assembled onto the first and the second sides  40 A,  40 B of the spinal column  40 , either at some time prior to, during, or after securing the stabilizing anchors  16 ,  18 ,  24 ,  26  to the spine  40 . In some embodiments, the transverse coupler  400  is assembled onto the first side  40 A of the spine  40  by coupling the first rod coupler  456  of the adjustment assembly  250  to the first rod  12 . The first rod  12  is able to axially translate and change in pitch and yaw, but is substantially restricted from translating laterally at the first rod coupler  456 , according to some embodiments. 
     The transverse coupler  400  is optionally assembled onto the second side  40 B of the spine  40  by coupling the second rod coupler  412  of the adjustment arm  402  to the second rod  14 . In some embodiments, the second rod  14  is locked from axial translation and changing in pitch, yaw and roll at the second rod coupler  412 . The adjustment arm  402  of the first transverse coupler  400  is be positioned across the first apical vertebra  42  such that a connecting portion  422  of an adjustment arm  402  extends from the first side  40 A of the spine  40  to the second side  40 B of the spine  40 , according to some embodiments. 
     As previously discussed, the first transverse coupler  400  optionally has the force directing member  404  rigidly coupled to the adjustment arm  402 . In some embodiments, the adjustment retainer  454  is actuated along the force directing member  404  by rotating a threaded cap  455  of the adjustment retainer  454  clockwise along a threaded portion of the force directing member  404 . Actuating the adjustment retainer  454  decreases an effective length L ( FIG. 27 ) of the force directing member  404  as desired. In some embodiments, the effective length L becomes approximately zero when the adjustment arm  402  becomes seated flush against the adjustment assembly  450 . In other words, actuating the retainer  454  optionally changes the distance and orientation of the rider  452  with respect to the adjustment arm  402 . In some embodiments, actuating the retainer  454  optionally couples the rider  452  to the adjustment arm  402 . The force directing member  404  is optionally cut or broken off to a shorter length, as desired, during the procedure as the effective length L decreases from the initial effective length. 
     As the adjustment retainer  454  is optionally actuated along the force directing member  404 , the rider  452  provides a resistance force that transmits through the force directing member  404  to the adjustment arm  402 . In some embodiments, the resistance force causes the second rod  14  to move towards the first rod  12 , which laterally translates a portion of the spine  40  towards the first rod  12 . 
     In some embodiments, the adjustment retainer  454  is actuated along the first force directing member  404  such that the first surface  414  of the adjustment arm  402  comes into contact with the adjustment assembly  450 . The adjustment retainer  454  is then optionally further actuated to pivot the rider  452  and the adjustment arm  402  towards each other such that the first surface  414  of the adjustment arm  402  becomes seated flush against a second surface  460  of the rider  452 . As the adjustment assembly  450  and the adjustment arm  402  impinge and ultimately become seated together, according to some embodiments. Once the adjustment arm  402  and the adjustment assembly  450  are brought into the desired amount of contact or the desired effective length L of the force directing member  404  has been achieved. 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.