Abstract:
An exemplary apparatus for connecting surgical rods according the principles of the present disclosure includes an elongate first arm, an elongate second arm, and a clamping assembly. The elongate first arm includes a first end that couples with a first rod and a second end with a first engagement portion. The elongate second arm includes a first end that couples with a second rod and a second end terminating in a second engagement portion. The clamping assembly includes a passageway that slidably receives the first engagement portion and that retains the second engagement portion and an adjustment member offset from the passageway that adjusts a clamping force to restrict positioning of the second engagement portion relative to the first engagement portion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Application Ser. No. 61/527,199 filed on Aug. 25, 2011, entitled “Apparatus and Method for Connecting Surgical Rods” and U.S. Provisional Application Ser. No. 61/604,333 filed on Feb. 28, 2012, also entitled “Apparatus and Method for Connecting Surgical Rods,” both incorporated by reference in their entirety herein. 
     
    
     FIELD 
       [0002]    The present invention relates generally to the field of surgery, and more specifically, to an apparatus and method for connecting surgical rods. 
       BACKGROUND 
       [0003]    One of the goals of a spinal fusion procedure is to unite two or more vertebrae to prevent them from moving independently of each other. This may be done to improve posture, increase ability to ventilate the lungs, prevent pain, or treat spinal instability and reduce the risk of nerve damage. According to the American Academy of Orthopedic Surgeons, approximately a quarter-million spinal fusions are performed each year, half on the upper and half on the lower spine. 
         [0004]    Posterior spinal fusion surgery involves approaching the patient from the back of patient, as opposed to anterior or lateral spinal fusion through the abdomen or side. There are three know posterior fusion techniques (all three are typically performed with pedicle screw fixation). There have been various approaches and systems for performing posterior spinal surgery. Some conventional systems further 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 one-piece implant to be applied to a dual-rod construct for a top-loading approach. 
         [0005]    Conventional devices and systems for linking rods have a number of disadvantages. Many cross-connectors do not provide sufficient flexibility when adjusting the devices either prior to, during, or after their placement into the patient. Alternatively, many cross-connectors have grown too complex with multiple parts, joints, and locking set screws. Thus, these devices force a surgeon to utilize a specific configuration, leaving very little room for adjustment in accordance with patient&#39;s physiological characteristics and needs. Further, these devices do not allow a surgeon to connect multiple rods by actuating a single setscrew mechanism. 
       SUMMARY 
       [0006]    An exemplary apparatus for connecting surgical rods according the principles of the present disclosure includes an elongate first arm, an elongate second arm, and a clamping assembly. The elongate first arm includes a first end that couples with a first rod and a second end with a first engagement portion. The elongate second arm includes a first end that couples with a second rod and a second end terminating in a second engagement portion. The clamping assembly includes a passageway that slidably receives the first engagement portion and that retains the second engagement portion and an adjustment member offset from the passageway that adjusts a clamping force to restrict positioning of the second engagement portion relative to the first engagement portion. 
         [0007]    In other features, the first engagement portion includes a first recessed portion extending along a longitudinal length of the first arm. The second engagement portion includes a spherical portion configured to pivot and translate within the first engagement portion. The second engagement portion comprises a first hemispherical portion with a first radius and a second hemispherical portion with a second radius greater than the first radius. The passageway includes a second recessed portion that receives the second engagement portion and permits pivoting of the second engagement portion within the clamping assembly. An aperture extends through the clamping assembly adjacent to the passageway. The clamping assembly includes an upper portion, a side portion, and a lower portion that form a generally C-shaped clamping member. 
         [0008]    Another exemplary apparatus for connecting surgical rods according to the principles of the present disclosure includes an elongate first arm, an elongate second arm, and a clamping assembly. The elongate first arm includes a first end that couples with a first rod and a second end with a recessed portion extending along a longitudinal length. The elongate second arm includes a first end that couples with a second rod and a second end terminating in a spherical portion. The clamping assembly extends around the first and second arms and retains the spherical portion within the recessed portion and provides clamping force to control positioning of the first arm relative to the second arm. 
         [0009]    In other features, the recessed portion includes a curved channel with a first radius. The spherical portion comprises a first hemispherical portion with a first radius and a second hemispherical portion with a second radius greater than the first radius. The second arm further comprises a pair of flat surfaces adjacent the spherical portion that engage the clamping member to restrict rotation about a longitudinal axis of the second arm. The clamping assembly includes a setscrew that engages the spherical portion and applies a force to clamp the spherical portion and the recessed portion together. The second arm translates along a longitudinal axis of the first arm. The second arm rotates about a longitudinal axis of the second arm relative to the clamping member. The second arm pivots about a transverse axis extending through the spherical portion that is perpendicular to a longitudinal axis of the second arm. 
         [0010]    Another exemplary apparatus for connecting surgical rods according the principles of the present disclosure includes a first arm, a second arm, and a collar. The first arm includes a first end formed into a first hook that secures to a first rod and a second elongated end including a channel that extends along a longitudinal length. The second arm includes a first end formed into a second hook that secures to a second rod and second elongated end terminating in a spherical portion. The collar includes a passageway that retains the spherical portion within the channel and that receives a force adjustment member to adjust a clamping force on the spherical portion to allow positioning of the second arm relative to the first arm in a first configuration and to restrict positioning of the first arm relative to the second arm in a second configuration. 
         [0011]    In other features, the spherical portion comprises a first hemispherical portion with a first radius that corresponds to a radius of a recessed portion within the passageway and a second hemispherical portion with a second radius that corresponds to a radius of the channel. The second arm translates freely along a longitudinal axis of the first arm in the first configuration. The second arm rotates freely about a longitudinal axis of the second arm in the first configuration. The second arm pivots about a transverse axis extending perpendicular to a longitudinal axis of the first arm in the first configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIGS. 1 and 2  are perspective views of an exemplary apparatus for connecting surgical rods according to the principles of the present disclosure. 
           [0013]      FIGS. 3-5  illustrate an exemplary first arm of the apparatus according to the principles of the present disclosure. 
           [0014]      FIGS. 6-8  illustrate an exemplary second arm of the apparatus according to the principles of the present disclosure. 
           [0015]      FIGS. 9 and 10  illustrate an exemplary setscrew for use with the first and second arms according to the principles of the present disclosure. 
           [0016]      FIGS. 11-13  illustrate an exemplary collar of the apparatus according to the principles of the present disclosure. 
           [0017]      FIGS. 14 and 15  illustrate another exemplary setscrew for use with the collar according to the principles of the present disclosure. 
           [0018]      FIGS. 16 and 17  are elevational side views of the exemplary apparatus illustrating rotational movement of the second arm relative to the first arm and the collar according to the principles of the present disclosure. 
           [0019]      FIG. 18  is a cross-sectional view of the exemplary apparatus according to the principles of the present disclosure illustrating translational and rotational movement of the first and second arms. 
           [0020]      FIGS. 19 and 20  illustrate translational movement of the first arm relative to the second arm and the collar according to the principles of the present disclosure. 
           [0021]      FIGS. 21-24  illustrate rotational movement of the second arm relative to the first arm and the collar according to the principles of the present disclosure. 
           [0022]      FIG. 25  is a perspective view of another exemplary apparatus for connecting surgical rods according to the principles of the present disclosure. 
           [0023]      FIG. 26  is an exploded perspective view of another exemplary collar of the apparatus according to the principles of the present disclosure. 
           [0024]      FIGS. 27 and 28  are perspective views of the collar of  FIG. 26  according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The exemplary embodiments of the present invention include two arms with fixed hooks that couple to the alignment rods and a single central link between opposite ends of the two arms provides six degrees of freedom of movement. The six degrees of freedom include rotation and translation along three Cartesian axes passing through the central link The axes may be described with respect to the sagittal, coronal, and transverse planes of the human anatomy. In some examples, axes normal to these planes may be referred to as the sagittal, coronal, and transverse axes. The sagittal and coronal axes may lie perpendicular to one another in the transverse plane. The transverse and sagittal axes may lie perpendicular to one another in the coronal plane. The coronal and transverse axes may lie perpendicular to one another in the sagittal plane. 
         [0026]    The apparatus may generally include a pair of arms, each including a hook at its outer end for attachment to spinal rods extending in the cephalad-caudal direction. The arms extend generally transverse to the spinal rods along their longitudinal axes. The longitudinal axes extend generally parallel to a transverse plane of the body. Each of the pair of arms includes coupling features or engagement portions at its inner end secured by a clamping assembly. For example, the apparatus may include a first arm including a first end that couples with a first rod and a second end with an engagement portion and a second arm including a first end that couples with a second rod and a second end terminating in a spherical head. The central portion of the apparatus may include a collar assembly that allows positioning of the semi-spherical head in the engagement portion in a first configuration and restricts positioning of the semi-spherical head in the engagement portion in a second configuration. 
         [0027]    The exemplary embodiments of the present invention are advantageous over the prior art because the apparatus provides greater flexibility for implant adjustment in situ while reducing the number of parts in the assembly. The greater flexibility may provide better fit between the alignment rods and reduce surgery time. The reduced number of parts may decrease likelihood of part failures, reduce costs of manufacturing, and simplify the implantation procedure. 
         [0028]    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. 
         [0029]    Referring now to  FIG. 1 , an exemplary crosslink apparatus  100  for connecting surgical alignment rods includes a first arm  102  and a second arm  104  coupled by a collar  106 . The first arm  102  includes a first end  108  configured to couple with a first alignment rod (not shown) and a second end  110  with a first engagement portion  112 . The second arm  104  includes a first end  114  configured to couple with a second alignment rod (not shown) and a second end  116  with a second engagement portion  118 . The collar  106  includes features that allow positioning of the first engagement portion  112  relative to the second engagement portion  118  in a first configuration and restricts positioning of the first engagement portion  112  relative to the second engagement portion  118  in a second configuration. For example, in  FIG. 1 , the collar  106  may fit snugly around the first and second engagement portions  112  and  118  to sufficiently lock the first arm  102  in position relative to the second arm  104 . In  FIG. 2 , the collar  106  may fit loosely around the first and second engagement portions  112  and  118  to enable free translation of the first arm  102  relative to the second arm  104  and the collar  106  and free rotation of the second arm  104  relative to the first arm  102  and the collar  106 . 
         [0030]    Referring to  FIGS. 3-5 , additional features of the first arm  102  are illustrated in greater detail. At the first end  108 , the first arm  102  may terminate in a first hook  120 . The first hook  120  may include a radius R corresponding to the radius or diameter of the first alignment rod. At the second end  110 , the engagement portion  112  may include a channel  122  on an upper surface  124 . The second end  110  may further include a lip  126  that extends away from a lower surface  128  of the first arm  102 . The lip  126  may prevent the first arm  102  from sliding out of the collar  106  after installation. For example, the lower surface  128  may be substantially flat to allow sliding engagement between the engagement portion  112  and the collar  106 . As the first end  108  slides away from the collar assembly  106 , the lip  126  may contact an outer edge of the collar  106 . A first aperture  130  may pass through a portion of the first end  108 . The first aperture  130  may receive a first setscrew  132  (shown in  FIGS. 1 ,  14 , and  15 ) that locks the first hook  120  with the first alignment rod (not shown). 
         [0031]    Referring to  FIGS. 6-8 , additional features of the second arm  104  are illustrated in greater detail. At the first end  114 , the second arm  104  may terminate in a second hook  134 . The second hook  134  may include a radius R corresponding to the radius or diameter of the second alignment rod. At the second end  116 , the second engagement portion  118  may terminate in a head  136 . The head  136  may include a first portion  136   a  and a second portion  136   b . The first portion  136   a  may extend from an upper surface  138  of the second engagement portion  118  and the second portion  136   b  may extend from a lower surface  140  of the second engagement portion  118 . The first portion  136   a  may include a semi-spherical shape with a first radius R 1  and the second portion  136   b  may include a semi-spherical shape with a second radius R 2 . The head  136  may be configured to engage the channel  122  of the first arm  102 . For example, the channel  122  may include a routed portion of the upper surface  124  having a radius substantially similar to one of the first and second radii R 1  and R 2 . A second aperture  142  may pass through a portion of the first end  114 . The second aperture  142  may receive a second setscrew  144  (shown in  FIG. 1 ) that locks the second hook  134  with the second alignment rod (not shown). The second setscrew  144  may be substantially similar to the first setscrew  132 . 
         [0032]      FIGS. 9-10  illustrate additional features of the first setscrew  134  (and second setscrew  144 ) that enable coupling with surgical rods. The setscrew  132  includes a head portion  146 , a threaded portion  148 , and a tapered end portion  150 . The head portion  146  includes a driving feature  152  for receiving a screwdriver or other tool that may advance the threaded portion  148  relative to a corresponding threading within the aperture  132 . The tapered portion  150  may include a straight tapered edge or alternatively a contoured edge (not shown) for engagement with a surgical rod. The tapered portion  150  may engage the surgical rod and force the rod into contact with the first hook  120 . The second setscrew  144  may include similar features and similarly engage a second surgical rod and force the second rod into contact with the second hook  134 . 
         [0033]    Referring now to  FIGS. 11-13 , the collar  106  includes features that enable sliding engagement with the first arm  102  and rotational engagement with the second arm  104 . The collar  106  includes an upper portion  154 , side portions  156 , first and second sagittal portions  158  and  160 , and a lower portion  162  that together form a substantially cuboidal construct. The first sagittal portion  158  includes a first opening  164  for receiving the first arm  102 . For example, the second end  110  of the first arm  102  may be inserted through the first opening  164  and the lower surface  128  may slidably engage an interior surface  166  of the lower portion  162 . The second sagittal portion  160  includes a second opening  168  for receiving the first arm  102  and the second arm  104 . For example, the second end  118  of the second arm  104  may be inserted through the second opening  168 . The second end  110  of the first arm  102  may pass through the interior of the collar  106  and exit through the second opening  168 . The lip  126  on the second end  110  may prevent the first arm  102  from sliding out of the collar  106 . 
         [0034]    The upper portion  154  may include a third aperture  170  extending to the interior of the collar  106 . The third aperture  170  may receive a third setscrew  172 , shown in  FIGS. 1 ,  14 , and  15 , for selectively locking the second ends  110  and  118  of the arms  102  and  104  respectively. The setscrew  172  includes a head portion  174 , a threaded portion  176 , and a recessed portion  178 . The head portion  174  includes a driving feature  180  for receiving a screwdriver or other tool that may advance the threaded portion  176  relative to a corresponding threading within the aperture  170 . The recessed portion  178  may include concave section having radius similar to the radius R 1  of the semispherical head  136   a . The end portion  170  may include a conical shaped section configured to receive the semispherical head  136   a.    
         [0035]      FIGS. 16 and 17  illustrate side views of the crosslink  100  looking into the first arm  102  and the second arm  104  respectively.  FIG. 18  illustrates a cross-section of the crosslink  100  along the plane XVIII of  FIG. 17 . The central setscrew  172  engages the upper first portion  136   a  of the head  136 . The lower second portion  136   b  of the head  136  engages the channel  122 . The channel  122  engages interior surface  166  of the lower portion  162  of the collar  106 . When the setscrew  172  is loosened, the first arm  102  may slide inside the collar  106  and the second arm  104  may rotate inside the collar  106 . As the setscrew  172  is tightened, the first arm  102  may be locked against the second arm  104  within the collar  106 . The first arm  102  may slide a distance D in a direction substantially parallel to a sagittal axis of the body. The second arm  104  may rotate about the head  136  in the transverse plane, the sagittal plane, and the coronal plane. 
         [0036]    Referring now also to  FIGS. 19 and 20 , translation of the first arm  102  relative to the second arm  104  and collar  106  in the transverse plane is shown. The first arm  102  may slide within the collar  106  while the head  136  of the second arm  104  rests within the channel  122 . Thus, the overall length of the crosslink  100  may vary between a first length D 1  and a second length D 2  measured from the radial center of the first hook  120  and the second hook  134 . The travel of the first arm  102  may be limited by a stop  180  on the first end  108  and the lip  126  on the second end  110 . The stop  180  may engage the first transverse portion  158  when the crosslink  100  includes the first length D 1 . The lip may engage the lower portion  162  when the crosslink  100  includes the second length D 2 . Therefore, the overall length of the crosslink  100  may be limited in the transverse plane by the lip  126  and the stop  180 . 
         [0037]    Referring now also to  FIGS. 21 and 22 , rotation of the second arm  104  relative to the first arm  102  and the collar  106  in the coronal plane is shown. The second arm  104  may rotate within the collar  106  about the head  136 . The head  136  may freely rotate within the cavity formed by the channel  122  and the recessed portion  178  of the setscrew  172  similar to a ball joint. The second arm  104  may rotate through an angle A 2 . The rotational position of the second arm  104  may be limited by engagement of a portion of the second end  118  with the second transverse portion  160  of the collar  106 . 
         [0038]    Referring now also to  FIGS. 23 and 24 , rotation of the second arm  104  relative to the first arm  102  and the collar  106  in the sagittal plane is shown. The second arm  104  may rotate within the collar  106  about the head  136 . The head  136  may freely rotate within the cavity formed by the channel  122  and the recessed portion  178  of the setscrew  172  similar to a ball joint. The second arm  104  may rotate through an angle A 3 . The rotational position of the second arm  104  may be limited by engagement of a portion of the second end  118  with the second transverse portion  160  of the collar  106 . 
         [0039]    The crosslink  100  may be used to link a pair of alignment rods to provide additional strength and rigidity to the fixation construct. For example, the first end  108  of the first arm  102  may be attached to a first alignment rod. The first hook  120  may wrap around the first alignment rod and the first setscrew  132  may be tightened. The second end  110  of the first arm  102  may slide inside the collar  106  to adjust the overall length of the crosslink  100  and enable the first end  114  of the second arm  104  to reach the second alignment rod. The first end  114  of the second arm  104  may be attached to a second alignment rod. The second hook  134  may wrap around the second alignment rod and the second setscrew  144  may be tightened. The second end  116  of the second arm  104  may slide inside the collar  106  and rotate to adjust the angle of engagement between the second hook  134  and the second alignment rod. The second end  116  may rotate in three planes. 
         [0040]    Once the arms  102  and  104  of the crosslink  100  have been positioned and the respective hooks  120  and  134  have been secured, the setscrew  172  within the collar  106  may be advanced to retain the head  136  and channel  122  within the collar  106 . Adjustment of the arms  102  and  104  may continue while the setscrew  172  is loose. When the arms  102  and  104  are properly positioned, the setscrew  172  may be tightened to lock the first arm  102  and the second arm  104  in place within the collar  106 . 
         [0041]    Referring now to  FIGS. 26-27B , another example of a crosslink  200  includes similar features as the crosslink  100  described above. Included are the first arm  102  and the second arm  104  of the previous example in  FIGS. 1-25 . For example, the first arm  102  includes the first end  108  configured to couple with a first alignment rod and the second end  110  with the first engagement portion  112 . The second arm  104  includes the first end  114  configured to couple with a second alignment rod and a second end  116  with a second engagement portion  118 . 
         [0042]    A clamping collar  206  replaces the collar  106 . The collar  206  includes features that allow positioning of the first engagement portion  112  relative to the second engagement portion  118  in a first configuration and restricts positioning of the first engagement portion  112  relative to the second engagement portion  118  in a second configuration. For example, similar to the collar  106  in  FIG. 1 , the collar  206  may fit snugly around the first and second engagement portions  112  and  118  to sufficiently lock the first arm  102  in position relative to the second arm  104 . And similar to the collar  106  In  FIG. 2 , the collar  206  may fit loosely around the first and second engagement portions  112  and  118  to enable free translation of the first arm  102  relative to the second arm  104  and the collar  206  and free rotation of the second arm  104  relative to the first arm  102  and the collar  206 . 
         [0043]    The collar  206  includes features that enable sliding engagement with the first arm  102  and rotational engagement with the second arm  104 . The collar  206  includes an upper portion  254 , a side portion  256 , and a lower portion  262  that together form a substantially C-shaped clamp. The second end  110  of the first arm  102  may be inserted through the collar  206  and the lower surface  128  may slidably engage an interior surface of the lower portion  262 . The second end  118  of the second arm  104  may be inserted through the collar  206 . The second end  110  of the first arm  102  may pass through the interior of the collar  206 . The lip  126  on the second end  110  may prevent the first arm  102  from sliding out of the collar  206 . 
         [0044]    The clamping collar  206  may include a third aperture  270  that receives a third setscrew  272 . The third aperture  270  is offset from a transverse centerline of the crosslink  200  extending through the arms  102  and  104 . The third aperture  270  may extend through the upper portion  254  and the lower portion  262 . The third aperture  270  may be opposite from the side portion  256  as shown in  FIG. 26 . An upper portion  270   a  of the third aperture may include chamfered edges while a lower portion  270   b  of the third aperture may include a threaded section. The setscrew  272  includes a head portion  274 , a threaded portion  276 , and a driving feature  280 . The collar  206  includes a recessed portion  278  that may include the chamfered edges. For example, the recessed portion  278  may include concave section having radius similar to the radius R 1  of the semispherical head  136   a . The recessed portion  278  may include a conical shaped section configured to receive the semispherical head  136   a.    
         [0045]    The setscrew  272  may be advanced through the third aperture  270  to clamp the upper portion  254  and lower portion  262  around the ends of the first arm  102  and the second arm  104 . Tightening the setscrew  272  increases clamping forces on the semi-spherical portions  136  of the end of the second arm  104  and forces the end into the channel  122  of the first arm  102 . 
         [0046]    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.