Lockable Pedicle Fastener

Abstract

A spinal fixation system comprising at least one fastener having a fastener head at a proximal end and at least one body. The body comprises a rod receiving channel for receiving a fixation rod, a pressure cap for engaging the fastener head, and a fastener head receiving chamber for retaining the fastener head within the body. The fastener head receiving chamber allows for multi-axial movement of the body in relation to the fastener when the pressure cap is disengaged from the fastener head. The body is secured in a mono-axial position in relation to the fastener when the pressure cap is biased against the fastener head.

1 . A spinal fixation system, comprising:
 at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface;   at least one body, wherein the body has a proximal portion and a distal portion;   the proximal portion comprising:
 a rod receiving channel for receiving a fixation rod; 
 an external attachment feature; and 
 a pressure cap disposed at a distal end of the proximal portion wherein a distal end of the pressure cap comprises an interior surface contoured to fit against the substantially spherical surface of the screw head; 
   the distal portion comprising:
 an internal attachment feature for engaging the external attachment feature of the proximal portion, wherein the engaging of the internal attachment feature with the external attachment feature secures the upper body to the lower body; 
 a screw head receiving chamber disposed at a distal end of the distal portion for retaining the screw head within the body; and 
 an external surface operable to engage a drive tool that operates to join the internal attachment feature with the external attachment feature and further cause the pressure cap to apply a bias against the screw head; 
   wherein the screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head; and   wherein the body can be secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.   
     
     
         2 . The spinal fixation system of  claim 1 , further comprising:
   a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.     
     
     
         3 . The spinal fixation system of  claim 2 , wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body. 
     
     
         4 . The spinal fixation system of  claim 1 , wherein the external attachment feature of the proximal portion of the body comprises external threads and the internal attachment feature of the distal portion of the body comprises complementary internal threads. 
     
     
         5 . The spinal fixation system of  claim 1 , wherein the external surface of the distal portion of the body comprises a perimeter of three or more flat sides for engaging the drive tool. 
     
     
         6 . The spinal fixation system of  claim 1 , wherein the at least one screw is a bone screw. 
     
     
         7 . The spinal fixation system of  claim 6 , wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine. 
     
     
         8 . The spinal fixation system of  claim 1 , wherein the rod receiving channel and the screw head receiving chamber are operatively connected to allow a tool to be inserted therethrough to apply torque to the screw. 
     
     
         9 . The spinal fixation system of  claim 1 , wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head. 
     
     
         10 . A spinal fixation system, comprising:
 at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface;   at least one body, the body comprising:
 a rod receiving channel for receiving a fixation rod; 
 an internal attachment feature; 
 a screw head receiving chamber disposed at a distal end of the body for retaining the screw head within the body; 
   at least one pressure cap disposed at a proximal end of the screw head receiving chamber and wherein the pressure cap comprises:
 a distal end with an interior surface contoured to fit against the substantially spherical surface of the screw head for engaging the screw head; 
 an external attachment feature for engaging the internal attachment feature of the body, wherein the engaging of the internal attachment feature with the external attachment feature secures the body to the pressure cap and allows the pressure cap to travel distally until the distal end is biased against the screw head; and 
 an internal surface operable to engage a driving tool operable to adjust the position of the pressure cap in a proximal or distal direction; 
   wherein the screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head; and   wherein the body is secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.   
     
     
         11 . The spinal fixation system of  claim 10 , further comprising:
 a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.   
     
     
         12 . The spinal fixation system of  claim 11 , wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body. 
     
     
         13 . The spinal fixation system of  claim 10 , wherein the internal attachment feature of the at least one body comprises internal threads and the external attachment feature of the at least one pressure cap comprises complementary external threads. 
     
     
         14 . The spinal fixation system of  claim 10 , wherein the internal surface of the pressure cap comprises a perimeter of three or more flat sides for engaging the driving tool. 
     
     
         15 . The spinal fixation system of  claim 10 , wherein the at least one screw is a bone screw. 
     
     
         16 . The spinal fixation system of  claim 15 , wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine. 
     
     
         17 . The spinal fixation system of  claim 10 , wherein the rod receiving channel and the screw head receiving chamber are operatively connected to allow a tool to be inserted therethrough to apply torque to the screw. 
     
     
         18 . The spinal fixation system of  claim 10 , wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head. 
     
     
         19 . A spinal fixation system, comprising:
 at least one screw having a screw head at a proximal end and wherein the screw head comprises a substantially spherical surface;   at least one body, the body having a proximal end and a distal end and further comprising:
 a rod receiving channel for receiving a fixation rod wherein the rod receiving channel is disposed adjacent the proximal end of the body; and 
 a screw head receiving chamber disposed adjacent the distal end of the body; 
 wherein the rod receiving channel and the screw head receiving chamber are operatively connected; 
   a pressure cap for engaging the screw head, the pressure cap comprising:
 a proximal portion disposed at least partially within the rod receiving channel; 
 a distal portion disposed at least partially within the screw head receiving chamber; 
 at least two lateral sides extending from the proximal portion to the distal portion; 
 a screw head interface disposed adjacent to the distal portion of the pressure cap; 
 a rod receiving surface disposed proximal to the screw head interface; and 
 an aperture extending from the rod receiving surface to the screw head interface; 
 wherein the pressure cap is operable to travel from within the rod receiving channel towards the screw head receiving chamber of the body when the fixation rod or a tool is used to apply a distal bias to the rod receiving surface such that the screw head interface of the pressure cap is biased against the screw head in the screw head receiving chamber; 
   a locking mechanism for securing the pressure cap in a biased position against the screw head;   wherein the screw head receiving chamber allows for multi-axial movement of the body in relation to the screw when the pressure cap is disengaged from the screw head; and   wherein the body is secured in a mono-axial position in relation to the screw when the pressure cap is biased against the screw head.   
     
     
         20 . The spinal fixation system of  claim 19 , further comprising:
 a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.   
     
     
         21 . The spinal fixation system of  claim 20 , wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body. 
     
     
         22 . The spinal fixation system of  claim 19 , wherein the at least one screw is a bone screw. 
     
     
         23 . The spinal fixation system of  claim 22 , wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine. 
     
     
         24 . The spinal fixation system of  claim 19 , wherein the aperture extending from the rod receiving channel to the screw head receiving chamber is operable to allow a tool to be inserted therethrough to apply torque to the screw. 
     
     
         25 . The spinal fixation system of  claim 19 , wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head. 
     
     
         26 . The spinal fixation system of  claim 19 , wherein the locking mechanism comprises:
 a linear rack of one or more teeth disposed on the external surface of one or more of the lateral sides of the pressure cap; and   one or more pawls disposed within the rod receiving channel of the body, operable to engage the one or more teeth of the pressure cap such that when the one or more pawls engage at least one of the one or more teeth, the pressure cap is secured in a biased position against the screw head.   
     
     
         27 . The spinal fixation system of  claim 26 , wherein the one or more teeth are asymmetrical in shape such that each tooth has a moderate slope on a distal edge and a much steeper slope on a proximal edge wherein interaction of the one or more pawls with the one or more teeth allows the pressure cap to travel distally but prevents travel in the proximal direction when the pawl is engaged. 
     
     
         28 . The spinal fixation system of  claim 27 , wherein the one or more pawls comprise a spring-loaded clip. 
     
     
         29 . The spinal fixation system of  claim 19 , wherein the rod receiving channel further comprises at least two lateral walls and wherein the locking mechanism comprises:
 an undercut disposed within one or more of the lateral walls of the rod receiving channel;   one or more flanges disposed at the proximal end of the pressure cap;   wherein, upon a distal pressure being applied to the rod receiving surface, the pressure cap is operable to travel distally within the rod receiving channel such that when the one or more flanges engage the undercut of the rod receiving channel the pressure cap is secured in a biased position against the screw head.   
     
     
         30 . The spinal fixation system of  claim 19 , wherein the locking mechanism comprises:
 one or more bores disposed within the body at a proximal end of the screw head receiving chamber and extending from an external surface of the body to an internal surface of the screw head receiving chamber;   one or more wedge elements disposed within the one or more bores wherein the one or more wedge elements are operable to travel laterally within the bores;   one or more recesses disposed within the pressure cap proximal to the screw head interface; and   wherein pressure applied in a medial direction to the one or more wedge elements causes a medial end of the one or more wedge elements to fit between a proximal surface of the one or more bores and a distal surface of the one or more recesses in a wedged position such that in the wedged position the pressure cap is secured in a biased position against the screw head.   
     
     
         31 . A spinal fixation system, comprising:
 at least one fastener having a fastener head at a proximal end;   at least one body, wherein the body comprises:
 a rod receiving channel for receiving a fixation rod; 
 a pressure cap for engaging the fastener head; and 
 a fastener head receiving chamber for retaining the fastener head within the body; 
   wherein the fastener head receiving chamber allows for multi-axial movement of the body in relation to the fastener when the pressure cap is disengaged from the fastener head; and   wherein the body is secured in a mono-axial position in relation to the fastener when the pressure cap is biased against the fastener head.   
     
     
         32 . The spinal fixation system of  claim 31 , further comprising:
 a compression element disposed at the proximal end of the rod receiving channel wherein the compression element is operable to apply a bias to the proximal surface of the fixation rod and thereby retain the fixation rod within the rod receiving channel.   
     
     
         33 . The spinal fixation system of  claim 32 , wherein the compression element comprises a set screw having external threads for cooperating with complementary internal threads, wherein the complementary internal threads are disposed on the proximal portion of the body or on a blocker inserted into a blocker receiving portion on the proximal portion of the body. 
     
     
         34 . The spinal fixation system of  claim 31 , wherein the at least one screw is a bone screw. 
     
     
         35 . The spinal fixation system of  claim 34 , wherein the at least one bone screw is configured to be screwed into a pedicle portion of a spine. 
     
     
         36 . The spinal fixation system of  claim 31 , wherein the rod receiving channel and the screw head receiving chamber are operatively connected to allow a tool to be inserted therethrough to apply torque to the screw. 
     
     
         37 . The spinal fixation system of  claim 31 , wherein the screw head receiving chamber includes a constriction element that operates to create a friction fit between an interior surface of the screw head receiving chamber and the substantially spherical surface of the screw head.