Abstract:
A method of securely connecting a spinal implant to a bone anchor by using an offset connection assembly. The variable angle connection assembly is able to securely connect the spinal implant to the anchors even when there is a variance in the angle and position of the anchors with respect to the spinal implant. The connection assembly will not inadvertently lock the components of the connection assembly preventing the relative movement of the components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/278,471 filed on Oct. 21, 2011, which is a continuation application of U.S. patent application Ser. No. 12/686,134 filed on Jan. 12, 2010, which issued as U.S. Pat. No. 8,070,781. These applications are incorporated herein by reference in their entireties for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a connection assembly, and more particularly, to a variable angle spinal implant connection assembly. 
       BACKGROUND OF THE INVENTION 
       [0003]    Spinal deformities, spinal injuries, and other spinal conditions may be treated with the use of spinal implants. Spinal implants are designed to support the spine and properly position the components of the spine. One such spinal implant includes an elongated rod and a plurality of bone anchors. The elongated rod is positioned to extend along one of more of the components of the spine and the bone anchors are attached to the spinal components at one end and secured to the elongated rod at the other end. 
         [0004]    However, due to the anatomical structure of the patient, the spinal condition being treated, and, in some cases, surgeon preference, the hone anchors may be required to he positioned at various angles and distances from the elongated rod. As a result, it can be difficult to obtain a secure connection between the elongated rod and the bone anchors. 
         [0005]    As such, there exists a need for a connection assembly that is able to securely connect an elongated rod to bone anchors despite a variance in the angle and position of the hone anchors with respect to the rod. 
       SUMMARY OF THE INVENTION 
       [0006]    In a preferred embodiment, the present invention provides a connection assembly that can be used to securely connect a spinal implant to a bone anchor. In particular, the present invention preferably provides an offset variable angle connection assembly that is able to securely connect the spinal implant to the anchors even when there is a variance in the angle and position of the anchors with respect to the spinal implant. Additionally, in a preferred embodiment, the present invention provides for a medial locking offset bone anchor connection that allows for the preservation of adjacent anatomical structure, such as adjacent facets. Furthermore, in a preferred embodiment, the present invention provides a connection assembly that will not inadvertently lock the components of the connection assembly preventing the relative movement of the components. 
         [0007]    In a preferred embodiment, the connection assembly comprises a housing member that has an aperture for receiving a portion of a spinal implant, an opening for receiving a securing member for securing the spinal implant and a channel for receiving a receiving member. The receiving member preferably has an aperture for receiving a portion of an anchor, a rim portion having at least one ridge, and a lumen. In addition, in a preferred embodiment, the receiving member is configured and dimensioned to he received in the channel of the housing member so that the receiving member is rotatably and translatably connected to the housing member. An interference member is preferably received in the lumen of the receiving member and is translatable in the lumen. In a preferred embodiment, an end of the interference member has an anchor contacting surface for locking the anchor in place. 
         [0008]    In a preferred embodiment, the connection assembly further comprises an annular member that is positioned over the receiving member and received in the channel of the housing member. Preferably, a face of the annular member has at least one ridge and the at least one ridge on the rim portion of the receiving member faces the at least one ridge on the second face of the annular member. In a preferred embodiment, the ridges are configured and dimensioned to engage with each other to lock rotational movement of the housing member and the receiving member. 
         [0009]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred or exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a perspective view of one embodiment of a connection assembly; 
           [0012]      FIG. 2  is an exploded perspective view of the connection assembly shown in  FIG. 1 ; 
           [0013]      FIG. 3  is an elevated side view of the connection assembly shown in  FIG. 1 ; 
           [0014]      FIG. 4  is a cross-sectional view of the connection assembly shown in  FIG. 1  in the direction of arrows A-A; and 
           [0015]      FIG. 5  is a cross-sectional view of the connection assembly shown in  FIG. 1  in the direction of arrows B-B. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0017]    With reference to  FIGS. 1-4 , a preferred embodiment of an offset connection assembly  10  is illustrated. The connection assembly  10  preferably includes a housing member  12  and an offset receiving member  14 . The housing member  12  includes an elongated aperture  16  at a first end for receiving at least a portion of a spinal implant  20 , such as a spinal rod, and the offset receiving member  14  includes an aperture  22  for receiving at least a portion of an anchor  24 , such as a bone screw. The aperture  22  (and anchor  24 ) is linearly offset from the spinal implant  20 , or in other words, the center of the aperture  22  is offset a distance x from a central axis  8 . One of ordinary skill in the art would recognize that although only a bone screw is shown, the aperture  22  of the offset receiving member  14  is capable of receiving any number of anchors including, but not limited to, other orthopedic screws, hooks, bolts, or other similar bone anchoring devices. The housing member  12  and the offset receiving member  14  are preferably rotatably connected. The rotatable connection can be of any suitable design, including a threaded connection, a snap-fit, or a captured connection. 
         [0018]    In a preferred embodiment, the housing member  12  also includes a second aperture  26  at the first end for receiving a securing member  28 . The second aperture  26  extends from an outer surface of the housing member  12  toward the elongated aperture  16 . In a preferred embodiment, the second aperture  26  is in fluid communication with the elongated aperture  16 . At least a portion of the second aperture  26  is preferably threaded to receive the securing member  28 , but the second aperture  26  can also be non-threaded. 
         [0019]    The securing member  28  is preferably a threaded set screw, as best seen in  FIG. 2 , but can be any type of securing member including, but not limited to, a bolt, a pin, a shoe, an interference member, or a cam member. In a preferred embodiment, the securing member  28  is captured in the second aperture  26  preventing accidental disengagement of the securing member  28  from the housing member  12 . The securing member  28  is captured in the second aperture  26  by including an overhanging portion  29  on the securing member  28  that abuts against the termination of the threading in the second aperture  26 . 
         [0020]    With continued reference to  FIG. 2 , the housing member  12  also includes, in a preferred embodiment, a channel  30  which extends from a second end of the housing member  12  toward the first end of the housing member  12 . The channel  30  is in fluid communication with the elongated opening  16 . Preferably, at least a portion of the channel  30  includes threading  31  interrupted by at least one groove  32  extending from the second end of housing  12  toward the first end of housing member  12 . In a preferred embodiment, the at least one groove  32  extends towards the first end of the housing member only a predetermined amount and preferably includes an end face  33  that defines the end of the groove  32 . 
         [0021]    The offset receiving member  14 , in a preferred embodiment, includes a first end and a second end, the aperture  22  located between the ends. The offset receiving member further includes a channel  35  and a resilient leg  50 . Referring to  FIGS. 2 and 5 , the offset receiving member  14 , in a preferred embodiment, receives in the channel  35  a connection member  17  which is generally cylindrical in shape with a generally cylindrical lumen  15 . 
         [0022]    The connection member  17  preferably includes threading  63  and a slot  65  at one end of the lumen  15 , at a first end of the connection member  17 . In another preferred embodiment, the lumen  15  may include a tapered shoulder portion  19 . The connection member  17  further includes a radially outwardly extending rim portion  34  on a second end that has a plurality of ridges  36  preferably oriented toward the offset receiving member  14 . In a preferred embodiment, the connection member  17  also has a shoulder portion  38 , spaced from the rim portion  34 , on the second end of the connection member  17 . The connection member  17  is configured and dimensioned to be received within the channel  30  of the housing member  12  and he received within channel  35  of the offset receiving member  14 . 
         [0023]    Turning back to  FIGS. 1-5 , the offset connection assembly  10  further includes, in a preferred embodiment, an interference member  40 , a gear  42 , a ring member  44 , a cap member  45  and an end cap member  46 . The interference member  40  has a generally cylindrical shape that tapers, in part, from a second end to a first end. The taper forms a shoulder portion  51 . In a preferred embodiment, the first end of the interference member  40  has an end portion  48  that is configured and dimensioned to abut a resilient leg  50  on offset receiving member  14 . On a second end of the interference member  40 , there is a face  49  which preferably is flat, but may also be arcuate and generally conforms to the shape of the spinal implant  20 . In another preferred embodiment, the interference member  40  has a generally rectangular shape with a first end having an end portion  48  that is configured and dimensioned to abut the resilient leg  50  and a second end that flares outwardly and includes face  49  for abutting the spinal implant. The interference portion  40  is configured and dimensioned to be received within the lumen  15  of the connection member  17 . 
         [0024]    The gear  42 , as best seen in  FIG. 2 , preferably is generally annular in shape and has a plurality of ridges  52  on one face and at least one projection  54  extending radially outwardly from the gear  42 . In a preferred embodiment, the gear  42  is configured and dimensioned to fit over the shoulder portion  38  of the connection member  17  and within channel  30  of the housing member  12 . The gear  42  is preferably oriented so that the ridges  52  face the ridges  36  on the rim portion  34  of the connection member  17  and the at least one projection  54  is received within the at least one groove  32  in the housing member  12 . 
         [0025]    In a preferred embodiment, the ring member  44  is generally annular in shape, has a first face and a second face, and is configured and dimensioned to fit over the connection member  17  and abut against the shoulder portion  38 , as best seen in  FIGS. 4 and 5 . Preferably, the ring member  44  also is configured and dimensioned to be received within the channel  30  of the housing member  12 . In a preferred embodiment, the ring member  44  is made from titanium, but the ring member  44  can also be made from any biocompatible material including resilient polymers. 
         [0026]    The cap member  45 , in a preferred embodiment, is generally annular in shape and has a first face and a second face. The cap member  45  includes an extension portion  56  on the first face of the cap member  45  and a lumen  60 . As best seen in  FIGS. 2 ,  4  and  5 , the extension portion  56  preferably is threaded along at least a portion thereof and includes a ramp portion  57 . Although the extension portion  56  preferably includes threading, in another preferred embodiment, the extension portion may not be threaded. Preferably, the diameter of the extension portion  56  is smaller than the diameter of the portion of the cap member  45  immediately adjacent to the extension portion  56  creating a shoulder portion  58 . In a preferred embodiment, the cap member  45  is configured and dimensioned so the extension portion  56  engages the threading  31  in the channel  30  of the housing member  12  and the shoulder portion  58  abuts the second end of the housing member  12 . The lumen  60  of the cap member  45  is configured and dimensioned to receive the connection member  17 . In a preferred embodiment, the cap member  45  is captured in the channel  30  of the housing member  12  to prevent the cap member  45  from inadvertently unthreading from the housing member  12 . 
         [0027]    The end cap member  46 , in a preferred embodiment, is generally annular in shape and has a first face and a second face. The end cap member  46  includes an extension portion  61  on the first face of the end cap member  46 . The extension portion  61  preferably is threaded along at least a portion thereof. Although the extension portion  61  preferably includes threading, in another preferred embodiment, the extension portion may not be threaded. In a preferred embodiment, the end cap member  46  is configured and dimensioned so the extension portion  61  engages the threading  63  in the lumen  15  of the connection member  17 . As best seen in  FIGS. 2 ,  4  and  5 , at least a portion of the first face of the end cap member  46  abuts the second end of the offset receiving member  14 . In a preferred embodiment, the end cap member  46  is captured in the lumen  15  of the connection member  17  to prevent the end cap member  46  from inadvertently unthreading from the connection member  17 . 
         [0028]    With reference to FIGS.  1  and  3 - 5 , in a preferred arrangement of the elements of the offset connection assembly  10 , the housing member  12  is rotatably connected to the offset receiving member  14 . As mentioned above, the connection member  17  is received within the channel  30  of the housing member  12  and within the channel  35  of the offset receiving member  14 . In a preferred embodiment, a second end of the connection member  17  abuts a medial wall  13  located within the housing member  12  and a first end of the connection member  17  extends beyond the second end of the housing member  12 . Positioned within the lumen  15  of the connection member  17  is the interference member  40 . 
         [0029]    In a preferred embodiment, also received within the channel  30  of the housing member  12  is the gear  42  which fits over the shoulder portion  38  of the connection member  17 . The at least one projection  54  on the gear  42  is received within the at least one groove  32  and preferably abuts the end face  33  of the groove  32 . The end face  33  of the groove  32  is spaced from the medial wall  13  of the housing member  12  by a predetermined amount, so the gear  42 , when placed in the channel  30 , is spaced from the rim portion  34  of the offset receiving member  14  by a predetermined amount. Accordingly, the ridges  36  on the rim portion  34  are spaced from the ridges  52  on the gear  42 . The purpose of this spacing is important and is explained further below. 
         [0030]    In a preferred embodiment, the ring member  44  is also received within the channel  30  of the housing member  12  and also fits over the connection member  17 . However, the inner diameter of the ring member  44  is smaller than the shoulder portion  38  of the receiving member  14 . As a result, at least a portion of the second face of the ring member  44  will abut the shoulder portion  38 . Preferably, the remaining portion of the second face of the ring member  44  will contact the gear  42 . 
         [0031]    The cap member  45 , in a preferred embodiment, is also received within the channel  30  of the housing member  12  and also fits over the connection member  17 . The threads on the threaded potion  56  engage with the threads  31  on the channel  30  to threadingly engage the cap member  46 . Preferably, the threaded portion  56  is threaded into the channel  30  until the shoulder portion  58  contacts the second end of the housing member  12 . In this position, the ramp portion  57  of the threaded portion  56  abuts the first face of the ring member  44 . 
         [0032]    The preferred arrangement of the elements, as discussed above, allow the housing member  12 , the gear  42  and the cap member  45  to rotate with respect to the receiving member  14 , the connection member  17 , the ring member  44 , the interference member  40 , and the end cap member  46 . As the housing member  12  rotates, the gear  42  will also rotate because of the at least one projection  54  located in the at least one groove  32 . Likewise, since the cap member  45  is threaded and preferably captured in the channel  30  of the housing member  12 , the cap member  45  also rotates when the housing member  12  rotates. In contrast, the connection member  17 , although captured within the channel  30  of the housing member  12  by virtue of the cap member  45  and the rim portion  34 , is capable of rotating as well as translating within the channel  30 . Similarly, the ring member  44 , although captured within the channel  30  of the housing member  12  by virtue of the shoulder portion  38  of the connection member  17  and the ramp portion  57  of the cap member  45 , is capable of rotating within channel  30 . Consequently, the ring member  44  does not rotate when the housing member  12  rotates. The receiving member  14  also is capable of rotating with respect to the housing member  12  as the receiving member  14  is connected to the housing member  12  through the connection member  17 , which, as just discussed, is capable of rotating with respect to the housing member  12 . 
         [0033]    A preferred connection of the spinal implant  20  to the anchor  24  through the connection assembly  10  is best depicted in  FIGS. 1 ,  2  and  3 . In an exemplary use, the anchor  24  is implanted into a component of the spinal column, such as a vertebral body in the spinal column. Preferably, the aperture  22  of the receiving member  14  of the connection assembly  10  receives the anchor  24 . The aperture  22  is configured and dimensioned to receive any portion of the anchor  24  allowing the connection assembly  10  to be placed anywhere along the length of the anchor  24 . Accordingly, the connection assembly  10  can be translated along the anchor  24  until the desired position is achieved. 
         [0034]    In an exemplary use, the spinal implant  20  is typically placed along at least a portion of the length of the spinal column in an orientation that is generally perpendicular to the anchor  24 . Preferably, the spinal implant  20  is also received in the connection assembly  10 , where the spinal implant  20  is received in the elongated opening  16  in the housing member  12 . The elongated opening  16  is configured and dimensioned to receive any portion of the spinal implant  20  allowing the connection assembly  10  to be place anywhere along the length of the spinal implant  20 . 
         [0035]    Additionally, since the housing member  12  and the receiving member  14  are rotatably connected to each other, even if the anchor  24  and the spinal implant  20  are angularly offset, the connection member  10  can be oriented to a desired position to connect the spinal implant  20  and the anchor  24 . Furthermore, as mentioned above, the anchor  24  is linearly offset from the spinal implant  20 , or in other words, the anchor  24  is offset a distance x from the central axis  8 , which is defined as extending from the first end of the housing member  12  to the second face of the end cap member  46 . This linear offset allows for an offset connection of the anchor  24  to the spinal implant  20  thereby allowing for the preservation of adjacent anatomical components, such as the adjacent facets. Once the desired angular orientation and translational positioning of the connection assembly  10  with respect to the anchor  24  and the spinal implant  20  is achieved, the connection assembly  10  can be locked, securing the anchor  24  and the spinal implant  20 . 
         [0036]    To lock the connection assembly  10 , the securing member  28  is threaded into the second aperture  26  in the housing member  12  where it contacts and pushes the spinal implant  20  toward the anchor  24 . The spinal implant  20  contacts the face  49  of the interference member  40  and pushes the interference member  40  towards the anchor  24 . As the interference member  40  is pushed by the spinal implant  20  towards the anchor  24 , the interference member  40  moves in the lumen  15  of the connection member  17  towards the anchor  24 , while the connection member  17  remains stationary. The end portion  48  of the interference member  40  abuts the resilient leg  50 , pushing the resilient leg  50  into the anchor  24 , which, in turn, pushes the anchor  24  into a sidewall of the aperture  22  in the receiving member  14 , locking the anchor  24  in place with respect to the connector assembly  10 . 
         [0037]    As the spinal implant  20  continues to move towards the anchor  24  and continues to push the interference member  40 , the shoulder portion  51  of interference member  40  abuts the walls of the lumen  15  and pushes against the walls of the lumen  15  moving the connecting member  17 . As the connecting member  17  moves, the shoulder portion  38  pushes against the second face of the ring member  44 . Since the first face of the ring member  44  abuts the ramp portion  57  of the cap member  46 , after a predetermined force is applied to the ring member  44  by the shoulder portion  38 , the ring member  44  deflects or bends in the direction of the ramp portion  57 . With the ring member  44  no longer blocking the shoulder portion  38 , the connecting member  17  continues moving towards the anchor  24  until the ridges  36  on the rim portion  34  of the receiving member  14  engage the ridges  52  on the gear  42 . With the ridges  36  and  52  engaged, the relative rotation of the housing member  12  and the receiving member  14  of the connection assembly  10  is locked. At this point, the spinal implant  20  is also locked in place between the threaded member  28  and the walls of the housing member  12  that define the elongated opening  16 . With the spinal implant  20  locked in place, the relative rotation of the housing member  12  and the receiving member  14  locked, and the anchor  24  locked in place, the entire assembly is locked against movement. Adjustments to the entire assembly can be made by loosening the threaded member  28  and then re-tightening the threaded member  28  once the preferred positioning and orientation has be achieved. 
         [0038]    It is important to note that because of the shoulder portion  38  abutting the ring member  44  and the at least one projection  54  of the gear  42  abutting the end face  33  of the at least one groove  32 , prior to the bending or deflection of the ring member  44 , the ridges  36  on the rim portion  34  of the receiving member  14  can not engage the ridges  52  on the gear  42 . This arrangement of elements prevents any inadvertent engagement of the ridges  36 ,  52  thereby preventing any unintended rotational locking of the housing member  12  with respect to the receiving member  14 . 
         [0039]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to he included within the scope of the following claims.