Abstract:
A connection assembly configured to securely connect a spinal implant to a bone anchor. In particular, a 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. Furthermore, a connection assembly that will not inadvertently lock the components of the connection assembly preventing the relative movement of the components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 13/966,012 filed on Aug. 13, 2013, which is a continuation of U.S. patent application Ser. No. 13/277,518 filed on Oct. 20, 2011 (now U.S. Pat. No. 8,529,605), which is a continuation of U.S. patent application Ser. No. 12/343,027 filed on Dec. 23, 2008 (now U.S. Pat. No. 8,066,746), all of which are incorporated by reference in their entirety herein. 
    
    
     FIELD 
     The present invention relates generally to a connection assembly, and more particularly, to a variable angle spinal implant connection assembly. 
     BACKGROUND 
     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 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. 
     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 anchors with respect to the rod. 
     SUMMARY 
     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 a 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. 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. 
     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 be 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. 
     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. 
     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 a perspective view of one embodiment of a connection assembly; 
         FIG. 2  is an exploded perspective view of the connection assembly shown in  FIG. 1 ; 
         FIG. 3  is an elevated side view of the connection assembly shown in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the connection assembly shown in  FIG. 1  in the direction of arrows A-A; 
         FIG. 5  is a cross-sectional view of the connection assembly shown in  FIG. 1  in the direction of arrows B-B; and 
         FIG. 6  is a cross-sectional view of another embodiment of a connection assembly. 
     
    
    
     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. 1-4 , a preferred embodiment of a connection assembly  10  is illustrated. The connection assembly  10  preferably includes a housing member  12  and a 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 receiving member  14  includes an aperture  22  at a first end for receiving at least a portion of an anchor  24 , such as a bone screw. One of ordinary skill in the art would recognize that although only a bone screw is shown, the aperture  22  of the 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 receiving member  14  are preferably rotatably connected to each other. The rotatable connection can be of any suitable design, including a threaded connection, a snap-fit, or a captured connection. 
     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. 
     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 . 
     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 . 
     Referring to  FIGS. 2 and 5 , the receiving member  14 , in a preferred embodiment, is generally cylindrical in shape with a generally tapered lumen  15 . In another preferred embodiment, the lumen  15  may not be tapered and instead include a shoulder portion. The receiving member  14  further includes a radially outwardly extending rim portion  34  on a second end that has a plurality of ridges  36  preferably oriented toward the first end of the receiving member  14 . In a preferred embodiment, the receiving member  14  also has a shoulder portion  38 , spaced from the rim portion  34 , on the second end of the receiving member  14 . The receiving member  14  is configured and dimensioned to be received within the channel  30  of the housing member  12 . 
     Turning back to  FIGS. 1-5 , the connection assembly  10  further includes, in a preferred embodiment, an interference member  40 , a gear  42 , a ring member  44 , and a cap member  46 . The interference member  40  has a generally polygonal shape that tapers from a second end to a first end. In a preferred embodiment, the first end of the interference member  40  has a saddle portion  48  that is configured and dimensioned to abut the anchor  24  and the second end of the interference portion  40  has a face  49  from which a cutout  50  extends towards the first end. The face  49  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 a saddle portion that is configured and dimensioned to abut the anchor and a second end that flares outwardly and includes a face for abutting the spinal implant and a cutout. Although the cutout  50  is located near the second end of the interference portion  40 , it is envisioned that the cutout  50  also be located near the first end of the interference portion  40 . The interference portion  40  is configured and dimensioned to be received within the lumen  15  of the receiver member  14 . 
     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 receiving member  14  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 receiving member  14  and the at least one projection  54  is received within the at least one groove  32  in the housing member  12 . 
     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 receiving member  14  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. 
     The cap member  46 , in a preferred embodiment, is generally cylindrical in shape and tapers from a first end to a second end. The cap member includes an extension portion  56  near the first end of the cap member 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  46  immediately adjacent to the extension portion  56  creating a shoulder portion  58 . In a preferred embodiment, the cap member  46  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  46  is configured and dimensioned to receive the receiving member  14 . In a preferred embodiment, the cap member  46  is captured in the channel  30  of the housing member  12  to prevent the cap member  46  from inadvertently unthreading from the housing member  12 . 
     With reference to  FIGS. 1 and 3-5 , in a preferred arrangement of the elements of the connection assembly  10 , the housing member  12  is rotatably connected to the receiving member  14 . As mentioned above, the receiving member  14  is received within the channel  30  of the housing member  12 . In a preferred embodiment, the second end of the receiving member  14  abuts a medial wall  13  located within the housing member  12  and the first end of the receiving member  14  extends beyond the second end of the housing member  12 . Positioned within the lumen  15  of the receiving member  14  is the interference member  40 . 
     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 receiving member  14 . 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 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. 
     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 receiving member  14 . 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 . 
     The cap member  46 , in a preferred embodiment, is also received within the channel  30  of the housing member  12  and also fits over the receiving member  14 . The threads on the threaded portion  56  engage with the threads  31  on the channel  30  to threadingly engage the threaded cap  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 . 
     The preferred arrangement of the elements, as discussed above, allow the housing member  12 , the gear  42  and the cap member  46  to rotate with respect to the receiving member  14 , the ring member  44 , and the interference member  40 . 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  46  is threaded and preferably captured in the channel  30  of the housing member  12 , the cap member  46  also rotates when the housing member  12  rotates. In contrast, the receiving member  14 , although captured within the channel  30  of the housing member  12  by virtue of the cap member  46  and the rim portion  34 , is capable of rotating as well as translating within the channel  30 . Accordingly, the receiving member  14  does not rotate when the housing member  12  rotates. 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 receiving member  14  and the ramp portion  57  of the cap member  46 , is capable of rotating within channel  30 . Consequently, the ring member  44  does not rotate when the housing member  12  rotates. 
     A preferred connection of the spinal implant  20  to the anchor  24  through the connection assembly  10  is best depicted in  FIGS. 1, 3 and 4 . 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. 
     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 . 
     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 . 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 . 
     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 , with the aid of the cutout  50 , compresses in the lumen  15  of the receiving member  14 , and continues towards the anchor  24 , while the receiving member  14  remains stationary. The saddle portion  48  of the interference member  40  abuts the anchor  24 , pushing 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 . 
     As the spinal implant  20  continues to move towards the anchor  24  and continues to push the interference member  40 , the interference member  40  no longer being able to compress any further in the lumen  15 , pushes against the walls of the lumen  15  and moves the receiving member  14 . As the receiving member  14  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 receiving member  14  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. 
     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 . 
     Turning now to  FIG. 6 , a second preferred embodiment of a connection assembly  110  is shown. The connection assembly  110  preferably includes a housing member  112  and a receiving member  114 . The housing member  112  includes an elongated aperture  116  at a first end for receiving at least a portion of a spinal implant  120  and the receiving member  114  includes an aperture  122  at a first end for receiving at least a portion of an anchor  124 . The housing member  112  and the receiving member  114  are preferably rotatably connected to each other. 
     In a preferred embodiment, the housing member  112  also includes a second aperture  126  at the first end for receiving a securing member  128 . The second aperture  126  extends from an outer surface of the housing member  112  toward the elongated aperture  116 . In a preferred embodiment, the second aperture  126  is in fluid communication with the elongated aperture  116 . At least a portion of the second aperture  126  is preferably threaded to receive the securing member  128 . In a preferred embodiment, the securing member  128  is captured in the second aperture  126  preventing accidental disengagement of the securing member  128  from the housing member  112 . 
     With continued reference to  FIG. 6 , the housing member  112  also includes, in a preferred embodiment, a channel  130  which extends from a second end of the housing member  112  toward the first end of the housing member  112 . The channel  130  is in fluid communication with the elongated opening  116 . Preferably, at least a portion of the channel  130  includes threading  131 . 
     The receiving member  114 , in a preferred embodiment, is generally cylindrical in shape with a cylindrical lumen  115  extending from a second end to the first end. Preferably, the cylindrical lumen is in fluid communication with the aperture  122 . In a preferred embodiment, in the lumen  115  of the receiving member  114 , a plurality of ridges  132  are present. The receiving member  114  is configured and dimensioned to be received within the channel  130  of the housing member  112  and includes threading  117  on an outer surface thereof to engage with the threading  131  in the channel  130 . Since the receiving member  114  is threadingly received in the channel  130  of the housing member  112 , the lateral position of the receiving member  114  with respect to the housing member  112  can be adjusted by rotating the receiving member  114 . This allows for controlled lateral adjustment of the anchor  124  with respect to the spinal implant  120 . 
     The connection assembly  110  further includes, in a preferred embodiment, an implant interference member  140  and an anchor interference member  142 . The implant interference member  140  has a generally cylindrical shape and includes a channel  144  that extends from a first end towards a second end of the implant interference member  140 . In a preferred embodiment, at least a portion of the channel  144  of the implant interference member  140  includes threading  146  to engage the anchor interference member  142 . The implant interference member  140  also preferably includes at least one cutout portion  145 , extending from the second end towards the first end, that separates at least a portion of the implant interference member  140  into sections. In a preferred embodiment, the implant interference member  140  also includes ridges  148  on an outer surface thereof. The implant interference member  140  is configured and dimensioned to be received in part within the lumen  115  of the receiving member  144  and in part within the channel  130  of the housing member  112 . 
     The anchor interference member  142 , in a preferred embodiment, also is generally cylindrical and includes threading  150  extending along at least a portion of the anchor interference member  142  from a second towards a first end. The anchor interference member  142  is configured and dimensioned to be received within the channel  144  of the implant interference member  144 . In a preferred embodiment, the threading  150  of the anchor interference member  142  threadingly engages the threading  146  in the channel  144  of the implant interference member  140 . 
     With continued reference to  FIG. 6 , to lock the connection assembly  110 , the securing member  128  is threaded into the second aperture  126  in the housing member  112  where it contacts and pushes the spinal implant  120  toward the anchor  124 . The spinal implant  120  contacts the implant interference member  140  and pushes the implant interference member  140  towards the anchor  124 . As the implant interference member  140  is pushed by the spinal implant  120  towards the anchor  124 , the anchor interference member  142 , which is threadingly engaged with the implant interference member  140 , also moves towards the anchor  124 . The first end of the anchor interference member  142  abuts the anchor  124 , pushing the anchor  124  into a sidewall of the aperture  122  in the receiving member  114 , locking the anchor  124  in place with respect to the connector assembly  110 . 
     As the spinal implant  120  continues to move towards the anchor  124  and continues to push the implant interference member  140 , the implant interference member  140  abuts against a medial wall  152  in the receiving member  114  and is no longer able to translate in the lumen  115  of the receiving member  114 . The continued movement of the spinal implant  120  toward the anchor  124  results in the implant interference member  140  splaying radially outwardly with the aid of the at least one cutout  145 . The implant interference member  140  splays outwardly until until the ridges  148  on the puter surface of the implant interference member  140  engage the ridges  132  in the lumen  115  of the receiving member  114 . With the ridges  132  and  148  engaged, the relative rotation of the housing member  112  and the receiving member  114  of the connection assembly  110  is locked. At this point, the spinal implant  120  is also locked in place between the threaded member  128  and the walls of the housing member  112  that define the elongated opening  116 . With the spinal implant  120  locked in place, the relative rotation of the housing member  112  and the receiving member  114  locked, and the anchor  124  locked in place, the entire assembly is locked against movement. Adjustments to the entire assembly can be made by loosening the threaded member  128  and then re-tightening the threaded member  128  once the preferred positioning and orientation has be achieved. 
     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.