Abstract:
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 a spinal implant 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. Furthermore, the present invention provides a connection assembly with structure to increase the locking strength of the connection assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation application claiming priority to U.S. patent application Ser. No. 13/558,667, filed Jul. 26, 2012, which is a continuation claiming priority to U.S. patent application Ser. No. 12/401,198, filed Mar. 10, 2009, now issued as U.S. Pat. No. 8,252,030, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a connection assembly, and more particularly, to a variable angle spinal implant connection assembly. 
     BACKGROUND OF THE INVENTION 
     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. 
     However, due to the anatomical structure of the patient, the spinal condition being treated, and, in some cases, surgeon preference, the bone anchors may be required to be positioned at various angles from the elongated rod. In addition, depending on the location of the bone anchor on the spinal column, the anchor may be required to be placed a distance away from the spinal implant. As a result, it can be difficult to obtain a secure connection between the elongated rod and the bone anchors. 
     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 bone anchor with respect to the rod. 
     SUMMARY OF THE INVENTION 
     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 a connection assembly that is able to securely connect the spinal implant to the anchor even when there is a variance in the angle and position of the anchor with respect to the spinal implant. Furthermore, in an embodiment of the present invention, the connection assembly provides additional structure to increase the locking strength of the connection assembly. 
     The connection assembly, in one embodiment, comprises a spinal implant positionable along a spinal column, an anchor member for engaging a vertebral body and a housing member that has an aperture for receiving a portion of the spinal implant and an opening for receiving the anchor member. Preferably, the housing member includes a channel extending through side surfaces of the housing member for receiving the spinal implant, an opening extending through an upper surface and a lower surface of the housing member for receiving the anchor member, a first clamping element for securing the anchor member in the opening of the housing member and a second clamping element for securing the spinal implant in the channel of the housing member. 
     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 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is an exploded view of one embodiment of a connection assembly; and 
         FIG. 2  is a cross sectional view of the connection assembly shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     With reference to  FIGS. 1-2 , a first embodiment of a connection assembly  10  is illustrated. The connection assembly  10  preferably includes a housing member  12  having, at a first end  14 , a generally hook shaped end portion  16  defining a channel  18  configured and dimensioned for receiving at least a portion of a spinal implant  20 , such as a spinal rod. At a second end  22 , the housing member  12  includes a first opening  24  for receiving at least a portion of an anchor  26 , such as a bone screw. The first end  14  and the second end  22  of the housing member  12  are joined by an elongated neck portion  28 . The neck portion  28  preferably integrally joins the first end  14  and the second end  22  to form a unitary, one-piece housing member  12 . 
     In an exemplary embodiment, the first opening  24  is configured and dimensioned to receive the anchor  26 . The first opening  24  extends from an upper surface of the housing member  12  to a lower surface of the housing member  12  forming a through hole. Preferably, the first opening  24  is sized such that a head portion  28  of the anchor  26  can be received within the first opening  24  but cannot pass through the first opening  24 . Looking at  FIG. 2 , a lower end  30  of the first opening  24  includes an arcuate section having a reduced diameter when compared to the diameter of the remainder of the opening  24 . This reduced diameter section prevents the head portion  28  of the anchor  26  from passing through the lower end  30  of the first opening  24  and also serves as a complementary surface to the generally spherical head portion  28 . In an exemplary embodiment, the first opening  24  includes a plurality ribs  32  extending along a portion thereof. Preferably, the ribs  32  are located along or neat the lower end  30  of the first opening  24 . In another exemplary embodiment, at least a portion of the first opening  24  is threaded to receive a fastening member  34 , but the first opening  24  can also be non-threaded. 
     The fastening member  34  is preferably a nut, as best seen in  FIG. 1 , but can be any type of fastening member including, but not limited to, an interference member or a cam member. In an exemplary embodiment, the fastening member  34  includes a threaded outer surface to engage the threading in the first opening  24  and a coupling for engaging a driver or other device for threading the fastening member  34  into the first opening  24 . 
     As mentioned above, the anchor  26 , in an exemplary embodiment, includes a head portion  28  and a shaft portion  36 . In a preferred embodiment, the head portion  28  is generally spherical and includes a plurality of ridges  38  the shaft portion  36  includes a plurality of threads  40 . The head portion  28  further includes a coupling for engaging a driver or other device for driving the anchor  26  into a vertebra. One of ordinary skill in the art would recognize that although only a bone screw is shown and described, the opening  24  is capable of receiving any number of anchors including, but not limited to, other orthopedic screws, hooks, bolts, or other similar bone anchoring devices. 
     In an exemplary embodiment, the housing member  12  also includes a second opening  42  at the first end  16  for receiving a securing member  44 . The second opening  42  extends from an outer surface of the housing member  12  toward the channel  18  so that the second opening  42  is in fluid communication with the channel  18 . At least a portion of the second opening  42  is preferably threaded to receive the securing member  44 , but the second opening  42  can also be non-threaded. 
     The securing member  44  is preferably a threaded set screw, as best seen in  FIG. 1 , 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 an exemplary embodiment, the securing member  44  includes a coupling for engaging a driver or other device for threading the securing member  44  into the second opening  42 . In another exemplary embodiment, the securing member  44  is captured in the second opening  42  preventing accidental disengagement of the securing member  44  from the housing member  12 . The securing member  44  is captured in the second opening  42  by including an overhanging portion on the securing member  44  that abuts against the termination of the threading in the second opening  42 . 
     In an exemplary use, the anchor  26  is passed shaft-first through the first opening  24  of the housing member  12  until the head portion  28  is located within the first opening  24 . The anchor  26  can then be placed in the bone at a desired location taking into account the clinical situation, the patient anatomy, and the surgeon preference. It is important to note that since the head portion  28  is generally spherical, the housing member  12  can be rotated with respect to the anchor  24  in a ball and socket-like fashion. This provides three dimensional variability of the anchor  24  with respect to the housing member  12 . 
     Independent of the anchor  26 , the spinal implant  20  is typically placed along at least a portion of the length of the spinal column in an orientation and location that ideally suited for treatment, again taking into account the clinical situation, the patient anatomy, and the surgeon preference. Preferably, the spinal implant  20  is received in the channel  18  of the housing member  12 . The channel  18  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  or otherwise couple to the spinal rod  20  at any portion along its length. 
     Additionally, since the housing member  12  and anchor  26  are rotatable with respect to each other, even if the anchor  26  and the spinal implant  20  are angularly offset, the housing member  12  can be oriented to a desired position to connect the spinal implant  20  and the anchor  26 . An advantage of this arrangement is that the anchor  24  and the spinal implant  20  can be connected without the need to contour the spinal implant  20 . This simplifies the surgical procedure, reduces operating time, and prevents undue stress or damage to the spinal implant caused by the contouring. Once the desired orientation and positioning of the connection assembly  10  is achieved, the connection assembly  10  can be locked, securing the anchor  26  and the spinal implant  20 . 
     To lock the connection assembly  10 , the securing member  44  is threaded into the second opening  42  in the housing member  12  where it contacts and pushes the spinal implant  20  toward wall  46  of the channel  18 . As best seen in  FIG. 2 , the spinal implant  20  is locked in place with respect to the housing member  12  when the implant  20  is lodged between the wall  46  of the channel  18  and the lower end of the securing member  44 . 
     Independent of securing member  44 , fastening member  34  is threaded into first opening  24  in the housing member  12  where it contacts and pushes the head portion  28  of the anchor  26  toward the lower end  30  of the first opening  20 . As best seen in  FIG. 2 , the anchor  26  is locked in place with respect to the housing member  12  when the anchor  26  is lodged between the fastening member  34  and the lower end  30  of the first opening  20 . As mentioned earlier, the head portion  28  of the anchor  26  includes a plurality of ridges  38 . These members are configured and dimensioned to interdigitate with the ribs  32  when the head portion  28  is located in the lower end  30  of the first opening  20 . Upon sufficient torque being applied to the fastening member  34 , which, in turn, pushes on the head portion  28 , the ridges  38  will deform around the ribs  32  forming a stronger, more secure “cold weld” between the anchor  26  and the housing member  12 . This “cold weld” provides exceptional load bearing capabilities thereby increasing the versatility of the connection assembly. For example, because of the increased locking strength and load bearing capabilities, the locking assembly  10  can be used in a variety of high loading, high stress anatomical areas and procedures, such as, being used in the iliac crest area as well as with the SI or upper sacral area of the spine. 
     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 be included within the scope of the following claims.