Abstract:
A bi-directional mechanically deployed rod mechanism utilizes non-parallel cam surfaces with a unique engagement, entrapment, and release methodology. The instrument utilizes a unique spring loading pivot point and lockout mechanisms to prevent early release of the pivot point and bi-directional cam surfaces.

Description:
PRIORITY 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/891,745, filed on Oct. 16, 2013, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present invention generally relates to spinal fusion surgeries. More particularly, the present invention relates to articulating rod holders for use in spinal fusion surgeries. 
     BACKGROUND 
     Pedicle screws and rod constructs are typically used for posterior fixation of vertebral bodies in spinal fusion surgeries. When spinal fusions are performed percutaneously, each screw may be attached to a temporary extension tubular device with slots generally timed to the screw slots which are designed for rod seating. Various rod holding devices exist to place the rods percutaneously into the extension slots and subsequently into the screw slots. These devices generally require extensive manipulation and the elongation of the surgical incision. Articulating rod holders allow rod insertion parallel to the extensions with mechanical rotation to a perpendicular position to the extensions for final seating. 
     Existing technology for articulating rod holders use either a one way cam whereby mechanical rotation from parallel to perpendicular is unidirectional and reversal cannot be mechanically activated/driven, or by parallel cams for bidirectional mechanical deployment. Each methodology has limitations. 
     SUMMARY 
     Disclosed is a new bi-directional mechanically deployed rod mechanism design that utilizes non-parallel cam surfaces with a unique engagement, entrapment, and release methodology. The instrument disclosed herein also utilizes a unique spring loading pivot point and lockout mechanisms to prevent early release of the pivot point and bi-directional cam surfaces. 
     The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. It is understood that the features mentioned hereinbefore and those to be commented on hereinafter may be used not only in the specified combinations, but also in other combinations or in isolation, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-4  depict an embodiment of the non-parallel cam surfaces with a unique engagement, entrapment, and release methodology according to certain embodiments of the invention. 
         FIGS. 5-10  depict an embodiment of the invention having an independent rod with its pivot point and forward cam driving point, cam driver entrance point, exit point, and reversal retention arc according to certain embodiments of the invention. 
         FIG. 11  depicts an embodiment of an articulating rod handle according to an embodiment of the invention. 
         FIG. 12  depicts an embodiment of a rod holder guide according to the invention. 
         FIGS. 13-15  depict an embodiment of the instrument of the present invention having a guide in place. 
     
    
    
     DETAILED DESCRIPTION 
     In the following descriptions, the present invention will be explained with reference to example embodiments thereof. However, these embodiments are not intended to limit the present invention to any specific example, embodiment, environment, applications or particular implementations described in these embodiments. Therefore, description of these embodiments is only for purpose of illustration rather than to limit the present invention. It should be appreciated that, in the following embodiments and the attached drawings, elements unrelated to the present invention are omitted from depiction; and dimensional relationships among individual elements in the attached drawings are illustrated only for ease of understanding, but not to limit the actual scale. 
     Referring to  FIGS. 1-4 , an embodiment of the non-parallel cam surfaces with a unique engagement, entrapment, and release methodology of the invention are shown in side views. The articulating rod holder  100  generally comprises a rod  102  and a driver  104 . The rod includes a rod interface  106  disposed on an end thereof. 
     The rod interface  106  extends outwardly from the end of the rod and defines a pivot point  108  adjacent to the rod end. The interface also defines a cam driver entrance  110  in a horizontal or longitudinal direction, an exit  112  in a vertical or lateral direction, and forward pivot point  114  defined at the intersection of the entrance and exit planes. A cam driver reverse retention arc  116  is defined in the interface diagonally across the pivot point and longitudinally between the entrance and exits. 
     As shown in  FIG. 2 , the driver cam engagement projections  118  and  120  extending from an end of the driver  104  features are engaged with the rod interface  106 . In particular, the pivot member  118  is engaged with the pivot point  108  and the driver cam  120  is engaged with the cam driver region of the interface. In the depicted orientation, the rod and driver are longitudinally aligned such that the driver cam  120  is in the load position. 
     In  FIG. 3 , the rod  102  is pivoted until it is oriented at an oblique angle with respect to the longitudinal axis of the driver  104 . In this orientation the driver cam  120  is entrapped for push/pull forces between the retention arc  116  and pivot point  114 . 
     In  FIG. 4 , the rod  102  is pivoted until it is oriented at a right angle with respect to the longitudinal axis of the driver  104 . In this orientation the driver cam  120  is in the unload/removal configuration. 
       FIGS. 5-10  illustrate various structural and operational aspects of certain embodiments in perspective view. In  FIG. 5 , the rod  102  includes the rod or female pivot point  108 , cam driver entrance  110 , cam driver exit  112 , and cam driver pivot point  114 . However, now can be more clearly seen various structures of the drive members  118  and  120 . 
     In particular, the driver pivot member  118  includes a male driver pivot projection  109  adjacent a distal end of the pivot projection  118  for engagement with respective female pivot depressions  108 . The driver cam member  120  defines a driver pivot point  115  at a distal end of the cam member  120 , for engaging the respective cam surfaces of the rod interface  106 . Also, a driver reverse retention channel  119  is defined in the drive member  120  proximally of the driver pivot point  115  in order to engage the inner surface of the reverse retention arc  116 . 
     In  FIG. 6 , the rod and driver are shown to be engaged while in longitudinal alignment similar to that shown in  FIG. 2 . This is an “unlocked” position. 
     In  FIG. 7 , the “locked” position is shown. Here, drive members  118  and  120  are retracted longitudinally into the driver  104 , while engaged with the rod  102  as shown in  FIG. 6  such that the rod and driver move towards one another. Thus, this embodiment differs from that of  FIGS. 1-4  in that the drive members are spring loaded to be extended during installation and connection with the rod interface  106 . 
       FIGS. 8 and 9  depict the rod  102  pivoted with respect to the longitudinal axis of the driver  104  in an oblique angle ( FIG. 8 ) and right angle ( FIG. 9 ). In both orientations, the rod and driver remain in a “locked” position. 
       FIG. 10  depicts the drive members  118  and  120  now extended to the “unlocked” position and disengaged with the rod interface  106 . 
     In certain embodiments, the drive members  118 ,  120  may be closed by a sliding collar, or other equivalent mechanism which slides, over at least a portion of the rod interface. 
     The driver cam  120  in certain embodiments has a longitudinal length from the driver pivot point  115  to the reverse retention slot  119  such that while the cam  120  is entrapped between the rod pivot point  114  and reverse retention arc  116 , both forward and reverse articulation occurs along the longitudinal axis. At full 90 degree articulation, cam driver  120  aligns with the cam driver exit  112 . The retention sleeve, collar or other retention mechanism is retracted to disengage the respective pivot points  108  and  109 , and the rod  102  is removed. 
       FIG. 11  depicts an embodiment of an articulating rod handle  122 . In one example embodiment, a movable handle  124  is be spring loaded with respect to a fixed handle  126 . The movable handle  124  is moved by application of force towards the fixed handle  126  to articulate the rod  102  with respect to the driver. Releasing the force applied to the movable handle  124  reverses the rod articulation. 
     According to one example embodiment, the handle mechanism  122  includes a locking sleeve actuator  128  or other mechanism to retract the drive members  118  and  120  into the driver (or to extend a locking collar or other mechanism over the rod interface  106 ). Such action may be achieved by cam surfaces on both sides of at least one of the drive members which engage the locking sleeve. The cam surfaces may slide against the locking sleeve driving the members to the closed position by forward positioning. A release button  130  can be provided to return the locking sleeve (or reverse the retraction) to the unlocked position. 
     A means, such as a slide lock button  132 , can be provided to the handle assembly  122  to lock the movement of the movable handle  124  in any position of its travel. When the slide lockout button  132  is engaged, the movable handle  124  is restricted or frozen in place such that the cam member  120  is prevented from withdrawing from the exit slot of the rod. This action may result in mechanical forward and reverse rod articulation between zero degrees (rod parallel to the device shaft) to about 88 degrees from parallel in certain embodiments. 
     The rod  102  may be loaded into the handle assembly  122 , which includes the driver  104 , by the user pushing the locking sleeve release button in, dropping a retention bar, thus allowing the locking sleeve to be pulled back. Such action moves the drive members to spring into the open position. The user may then slide the rod into the distal pivot points  108  and engage the drive cam  120  until the driver members  118  and  120  seat into the rod interface  106  simultaneously. Next the locking sleeve may be slid forward (or members retracted) to lock the pivot projections  109  into the rod pivot depressions  108  and engaging the locking sleeve member  128  of the handle assembly  122 . 
     For final positioning and seating of the rod into a screw saddle at about 90 degrees of rod articulation, the lock out button  132  may be pushed in, releasing the movable handle  124  to a fully closed, 90 degree rod articulation position. When the movable handle  124  is released and returned to the non-articulated position by handle spring force, a driving bar connecting the handle  124  to the rod  102  withdraws out of a rod exit slot. 
     With the driving bar withdrawn from the rod exit slot, final release of the rod may require the rod and pivot member  118  points to be released. The user may push the locking sleeve release button  130 , dropping the associated retention bar, and pull back the jaw locking sleeve. Then the pivot points are released by retracting the pivot member away from the rod pivot points  108 . 
       FIG. 12  depicts an example embodiment of a rod holder guide  134 . 
       FIG. 13  depicts the instrument  100  of the present invention including the guide  134  engaged with a tower assembly  136 . The tower assembly engages a screw assembly  138 . The guide  134  may be attached to the tower assembly similarly to the pivot member  118  and rod interface described preciously. 
     As shown in  FIG. 14 , the tower assembly  134  is engaged with the handle assembly  122 , which is in the locked position.  FIG. 15  depicts the same device as  FIG. 14 , but now the driver is unlocked and the rod is articulated to a right angle with respect to the longitudinal axis of the driver. 
     The articulating rod  102  may be inserted through the guide  134  to keep the rod orientation parallel to the extension direction, maintain the rod&#39;s alignment with the slot in the extension and to define the final depth of extension. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is, therefore, desired that the present embodiment be considered in all respects as illustrative and not restrictive. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.