Patent Publication Number: US-7901434-B2

Title: Vertebral rod assemblies and methods

Description:
RELATED APPLICATION 
     The present application is a divisional application of previously-filed U.S. patent application Ser. No. 11/313,000, filed on Dec. 20, 2005, herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present application relates generally to spinal implant assemblies, and more particularly to a vertebral rod system having first and second connectable and adjustable members. 
     The spine is divided into four regions comprising the cervical, thoracic, lumbar, and sacrococcygeal regions. The cervical region includes the top seven vertebrae identified as C1-C7. The thoracic region includes the next twelve vertebrae identified as T1-T12. The lumbar region includes five vertebrae L1-L5. The sacrococcygeal region includes nine fused vertebrae that form the sacrum and the coccyx. The vertebrae of the spine are aligned in a curved configuration that includes a cervical curve, thoracic curve, and lumbosacral curve. 
     Vertebral rods may be implanted to support and position the vertebrae in one or more of these regions. The rods extend along a section of the spine and are connected to the vertebrae with one or more fasteners. The rods may have a curved configuration to conform to the curvature of the spine. Often times two or more rods are connected together and work in combination to support and position the vertebrae. The rods may have the same or different shapes and sizes depending upon their position along the spine. 
     SUMMARY 
     The present application relates to a vertebral rod assembly. The vertebral rod assembly may comprise first and second members that may rotate with respect to each other about a first axis. Each of the first and second members may include a base and a vertebral support rod extending from the base. The base on the first member includes an extension member that extends into an opening formed in the base of the second member. A ring may extend around the extension and may fit within the base of the second member. A fastener may extend through a sidewall of the second member and the ring to lock the first and second members, and to prevent the rotation of the first member and second member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vertebral rod assembly according to one embodiment. 
         FIG. 2  is a perspective view of a first member of a vertebral rod assembly according to one embodiment. 
         FIG. 3  is a perspective view of a second member of a vertebral rod assembly according to one embodiment. 
         FIG. 4  is a cross sectional view of one embodiment of a vertebral rod assembly. 
         FIG. 5  is a perspective view of a vertebral rod assembly according to one embodiment. 
         FIG. 6  is a perspective view a first member of a vertebral rod assembly according to one embodiment. 
         FIG. 7  is a perspective view a second member of a vertebral rod assembly according to one embodiment. 
         FIG. 8  is a perspective view of a ring member according to one embodiment. 
         FIG. 9  is a cross sectional view of one embodiment of a vertebral rod assembly. 
         FIG. 10  is a cross sectional view of one embodiment of a vertebral rod assembly. 
     
    
    
     DETAILED DESCRIPTION 
     The present application is directed to vertebral rod assemblies, with one embodiment generally illustrated as element  10  in  FIG. 1 , having first and second members  12 ,  14 . Members  12 ,  14  are selectively positionable at a variety of angles to conform to the curvature of the patient&#39;s spine. Each member  12 ,  14  includes a rod and a base. A locking device locks the position of the members  12 ,  14  at the desired orientation to prevent further movement. 
       FIG. 2  illustrates the first member  12  having a rod  16  and a base  18 . In one embodiment, the rod  16  is attached to the base  18  and extends outward therefrom. In one embodiment, rod  16  and base  18  are integrally formed together. Base  18  includes a first surface  20  having a plurality of splines  22   a  spaced thereabout forming a series of alternating ridges and valleys. Splines  22   a  cover at least a portion of the first surface  20 . In one embodiment, the splines  22   a  are spaced about the periphery, and extend radially inward from an outer edge of the first surface  20  towards a central point as can be seen in  FIG. 2 . In another embodiment, the splines  22   a  extend outwards from about the central point of the first surface  20  towards the periphery. 
     An extension  24  extends outward from the first surface  20  and includes a shaft  26  having an angled surface  30  that flares outward to form an enlarged head  28 . Surface  30  slopes outward away from the first surface  20  and terminates at a flat outer surface of the head  28 . A rim  32  may be positioned at the peripheral edges of the angled surface  30  and the head  28 . 
       FIG. 3  illustrates the second member  14  having a rod  34  and a base  36 . As with the first member  12 , rod  34  is attached to or integrally formed with the base  36  and extends outward therefrom. Base  36  includes a first surface  38  having a plurality of splines  22   b  formed as alternating ridges and valleys. Splines  22   b  are formed to correspond to the size and spacing of splines  22   a  on the first member  12 . An opening  40  extends from the first surface  38  into the interior of the base  36  and is sized to receive the extension  24 . One or more openings  42  are formed in a sidewall of the base  36  and extend into the interior of the base  36 . In one embodiment, a pair of openings  42  are positioned in the base  36  and spaced apart by about 180° (i.e., the openings  42  are on opposite sides of the base  36 ). Multiple openings  42  allow for easier access during the locking and unlocking procedures as will be discussed below. In one embodiment, the one or more openings  42  may be threaded. 
     A fastener  44  extends through the opening  42  formed in the base  36 . In the embodiment illustrated in  FIG. 4 , fastener  44  is a screw having threads that engage the threads formed on the opening  42 . Fastener  44  inserts into the opening  42 , and has a contact surface  46  that contacts against the surface  30  of the extension  24 . The surfaces  30 ,  46  have corresponding shapes to increase the area of contact between the fastener  44  and extension  24  when the first and second members  12 ,  14  are coupled in a locked configuration. As illustrated in  FIG. 4 , the contact surface  46  at the end of the fastener  44  is angled and corresponds to the angle of surface  30 . In other embodiments, however, surfaces  30 ,  46  may not have corresponding shapes. In still other embodiments, fastener contact surface  46  and/or the inserted end of the fastener  44  are shaped to engage the shaft  26 . 
       FIG. 4  illustrates the assembly  10  in a locked configuration. Placing the first and second members  12 ,  14  in this locked configuration prevents the first and second members  12 ,  14  from rotating relative to each other about an axis of rotation R 1 . To rotate the first and second members  12 ,  14  about axis R 1 , the assembly  10  may be placed in an unlocked configuration as described below in more detail. 
     As seen in  FIG. 4 , the extension  24  of base  18  inserts into the opening  40  formed in the base  36 . When extension  24  is fully inserted, splines  22   a  and  22   b  engage and interlock with each other. Once engaged, the interlocking splines  22   a ,  22   b  prevent the relative rotation of the first and second members  12 ,  14 . Fastener  44  inserts into opening  42  and is rotated about an axis R 2  until fastener  44  engages second member  14 . In a particular embodiment, fastener  44  inserts into opening  42  and is rotated about axis R 2  until the contact surface  46  engages the angled surface  30  of extension  24 . Continuing to rotate fastener  44  about axis R 2  causes the contact surface  46  to apply a force to the angled surface  30  that locks the second base  36  to the first base  18 . This prevents the separation and rotation of the first and second members  12 ,  14 . This force also maintains the splines  22   a ,  22   b  in the interlocking relationship. In the embodiment of  FIG. 4 , the axis of rotation R 2  is substantially perpendicular to the axis of rotation R 1 . In other embodiments, the axis of rotation R 2  is substantially non-parallel to the axis of rotation R 1 . 
     To place the assembly  10  in the unlocked configuration, in one embodiment fastener  44  is rotated about axis R 2  such that contact surface  46  moves away from surface  30 . This movement releases the locking force that contact surface  46  applies to the angled surface  30 . This movement also allows for disengaging the interlocked splines  22   a ,  22   b . Once the splines  22   a ,  22   b  are disengaged, the first and/or second members  12 ,  14  may be rotated relative to each other by rotating first and/or second bases  16 ,  34  about axis R 1 . It is not necessary to separate the contact surface  46  from the angled surface  30  completely, nor is it necessary to remove fastener  44  from base  36  altogether. Rather, it is enough to rotate fastener  44  a sufficient amount to reduce the force applied by the contact surface  46  to the angled surface  30  and to disengage the splines such that the first and second members  12 ,  14  may rotate relative to one another. 
     Multiple openings  42  within the sidewall of the base  36  provide additional options for locking the device. Positioning the members  12 ,  14  along the spine at the proper angle may result in one of the openings  42  being blocked. In this event, the fastener  44  may be inserted into a second opening  42  that is accessible. Additionally, more than one fastener  44  may be used for engagement with a different fastener  44  inserted within each of the openings  42 . 
       FIGS. 5-10  illustrate another embodiment of assembly  10 . As seen in  FIG. 5 , assembly  10  comprises the first and second members  12 ,  14 , and an end cap  50  coupled to assembly  10  using a mechanical fastener  52 . As in the previous embodiment, the first and second members  12 ,  14  are selectively positionable at a variety of angles to conform the first and second rods  16 ,  34  generally to the curvature of the patient&#39;s spine. 
       FIGS. 6-7  illustrate the first and second members  12 ,  14  in more detail. As seen in  FIG. 6 , surface  20  comprises splines  22   a  formed as a plurality of alternating ridges and valleys that extend radially inward from a sidewall  56 . Splines  22   a  are spaced inward from the sidewall  56  forming a generally flat edge surface  54   a  that extends around the periphery of base  18 . Shaft  26  comprises a substantially cylindrical member that connects to and extends outward from surface  20 . A threaded opening  58  at one end of shaft  26  extends into the shaft  26 . The threaded opening  58  is formed to receive the mechanical fastener  52  that secures the end cap  50  to assembly  10 . 
     Shaft  26  also includes a tab  60  extending from its exterior sidewall. Tab  60  includes a ramped surface  64  that terminates at surface  62  that extends substantially perpendicular from the shaft  26 . A stop  66  extends outward beyond the surface  62  and has one or more opposing contact surfaces  68 . As described below in more detail, tab  60  comprises part of the locking device that locks the position of the first and second members  12 ,  14  at the desired orientation and may limit the angle through which the first and second members  12 ,  14  may rotate. 
     As best seen in  FIG. 7 , second member  14  includes a surface  70  having splines  22   b  comprising a plurality of ridges and valleys that extend radially inward towards the center of base  36 . The size and spacing of splines  22   b  corresponds generally to splines  22   a . A generally flat edge surface  54   b  extends between splines  22   b  and the peripheral edge of base  36 . When the first member  12  is mated to the second member  14 , the splines  22   b  extend into the base  18  to engage with the splines  22   a . Additionally, the flat edge surface  54   b  contacts corresponding flat edge surface  54   a  on base  18 . 
     An opening  74  with a notch  76  are formed in the surface  70 , and open into a receiving section  75 . Opening  74  and notch  76  are sized to receive the shaft  26  and the tab  60 , respectively, when the first member  12  mates with the second member  14 . One or more openings  78  are formed in a sidewall of the base  36  and extend into the receiving section  75 . The openings  78  may be disposed at any desired position on the sidewall of base  36 . Centerlines of the openings  78  may be perpendicular to centerlines of the opening  74 . As described in more detail below, the fastener  44  extends through the opening  78  to lock the first and second members  12 ,  14 . 
       FIG. 8  illustrates a ring  80  that fits within the receiving section  75  and extends around the shaft  26 . Ring  80  is a substantially cylindrical member that includes an outer sidewall  82  and an inner sidewall  84  that form a cavity  86 . A notch  88  is formed on the inner sidewall  84  to receive the tab  60  extending from the shaft  26 . An angled surface  90  slopes upward from a peripheral edge of the inner sidewall  84  and is angled to correspond to the angle of the ramped surface  64 . Angled surface  90  also extends around the inner circumference of the ring  80  from the notch  88  to a stop surface  92 . A threaded opening  94  extends through the ring into the cavity  86  and is sized to receive fastener  44 . 
     In one embodiment, a stop surface  92  is formed at one end of the angled surface  90 . Stop surface  92  contacts the stop  66  on the tab  60  to control the extent of relative rotation of the first and second members  12 ,  14 . During rotation, the ramped surface  64  may slide along angled surface  90  until the contact surface  68  of the stop  66  engages the stop surface  92 . In one embodiment as illustrated in  FIG. 8 , members  12 ,  14  rotate through an angle of approximately 180°. However, those skilled in the art will readily appreciate that the stop surface  92  may be formed on the ring  80  at any position such that the first and second members  12 ,  14  may only rotate a predetermined distance in one direction to limit the rotation. 
       FIG. 9  illustrates a cross sectional view of the assembly  10 . As in the previous embodiment, placing the first and second members  12 ,  14  in this locked configuration prevents the first and second members  12 ,  14  from rotating relative to each other about the axis of rotation R 1 . During assembly, ring  80  is positioned within the receiving section  75  with opening  94  in the ring aligning with the opening  78  in the base  36 . An outer diameter of the ring  80  is smaller than an inner diameter of the receiving section  75  such that the ring  80  can move along axis R 1  within the receiving section  75 . Further, the shaft  26  inserts into the opening  74  with the tab  60  aligning with the notch  76  in the opening and the notch  88  in the ring  80 . Fastener  44  is initially inserted into openings  78 ,  94 . 
     Prior to tightening the fastener  44 , first and second members  12 ,  14  are rotated to position the rods  16 ,  34 . Once oriented, fastener  44  is tightened causing the ring  80  to move along axis R 2  within the receiving section  75  towards the fastener  44 . This movement, in turn, causes the angled surface  90  on the ring  80  to contact and apply a locking force to the ramped surface  64  on the tab  60 . Adjusting the fastener  44  within the openings  78 ,  94  adjusts the degree of the locking force and thus prevents further rotation of the first and second members  12 ,  14 . 
     When the first and second members  12 ,  14  are positioned together, the splines  22   b  formed on base  36  engage and interlock with the splines  22   a  formed on base  16 . This engagement further prevents rotation of the first and second members  12 ,  14 . In addition, flat edge surfaces  54   a  and  54   b  contact each other to form a substantially smooth seam extending around the circumference of the first and second bases  18 ,  36 . 
     End cap  50  may be connected to assembly  10  using screw  52 . End cap  50  is sized to extend across the receiving section  75 . End cap  50  may further include a gasket to sealingly engage the sidewall of the base  36  and seal the receiving section  75 . 
       FIG. 10  illustrates another embodiment with a shaft  26  that terminates at a head  28 . Both the shaft  26  and head  28  have a substantially constant width that form a “T”. Fastener  44  includes a contact surface  47  that engages the shaft  26  to lock the device  10 . Contact surface  47  substantially matches the shaft  26  to increase the contact area. Fastener  44  may further be positioned for an edge to contact the head  28  to further lock the device  10 . In one embodiment, the locking force is provided between the contact surface  47  and the shaft  26 . In another embodiment, the locking force is provided between the edge of the fastener  44  and head  28 . 
     The various figures have illustrated bases  18  and  36  as having a circular shape. However, bases  18  and/or  36  may have other shapes and sizes. Further, the shapes and sizes of the bases  18 ,  36  may be the same or may be different. Likewise, the various openings may have different shapes and sizes to receive one or more various sizes and/or types of fasteners. 
     Rods  16  and  34  may have variety of lengths and diameters. The lengths and/or diameters of one or both of the rods  16 ,  34  may be the same or different. Moreover, one or both of the rods  16 ,  34  may be integrally formed with the sidewalls of their respective bases  16 ,  36 , or formed separately and attached to the sidewalls of their respective bases  18 ,  36 . Further, splines  22   a ,  22   b  may extend continuously around their respective bases  16 ,  34  or alternatively, may be formed in sections that are spaced apart along the surfaces of the first and second bases  18 ,  36 . 
     In one embodiment, axes of rotation R 1  and R 2  are substantially perpendicular. Examples include the embodiment illustrated in  FIGS. 4 ,  9 , and  10 . In other embodiments, however, the axes are aligned at a variety of angular orientations. Further, axis R 2  may be aligned to be substantially parallel with one or both rods  16 ,  34 . In other embodiments, axis R 2  may be positioned in a non-parallel manner. 
     The present invention may be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. A seal may be placed on one or both bases  18 ,  36  to sealingly engage the bases together in the locked configuration. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.