Pedicle screw assembly with inclined surface seat

Abstract

A bone stabilizer assembly includes a fixation element, a coupling element, and a compression nut. The fixation element is adapted to engage a bone and having a head portion and shank portion. The coupling element has an internal bore sized to receive the shank portion of the fixation element and a pyramid-shaped seat for supporting the head portion of the fixation element. The coupling element is adapted to receive a stabilizer rod. The compression nut is engagable with the coupling element and is adapted to rotatingly move distally into the coupling element to translate a force to the head portion through the rod and the saddle such that the head portion is forced against the seat of the coupling element to prevent relative movement between the fixation element and the coupling element.

1 - 7 . (canceled) 
     
     
         8 . A bone stabilizer assembly, comprising:
 a fixation element adapted to engage a bone and having a head portion and a shank portion;   a coupling element having a seat with one or more inclined surfaces that form an internal bore sized to receive the shank portion and retain the head portion, the seat leading to non-parallel inner surfaces in walls of the coupling element;   a stabilizer rod received within the coupling element;   a bottom saddle movably received within the coupling element below the stabilizer rod, the bottom saddle including walls with non-parallel outer surfaces that engage the non-parallel inner surfaces; and   a compression nut engagable with the coupling element, the compression nut adapted to rotatingly move distally into the coupling element to force the bottom saddle into frictional engage between the head portion and the non-parallel inner surfaces.   
     
     
         9 . The assembly of  claim 8 , further comprising a first angle measured from a horizontal plane of the internal bore to the inner surfaces and a second angle measured from the horizontal plane to the outer surfaces. 
     
     
         10 . The assembly of  claim 9 , wherein the first angle and the second angle are substantially the same. 
     
     
         11 . The assembly of  claim 9 , wherein the first angle and the second angle are approximately 100 degrees. 
     
     
         12 . The assembly of  claim 9 , wherein the first angle is greater than 90 degrees. 
     
     
         13 . The assembly of  claim 9 , wherein the first angle is greater than or equal to 105 degrees. 
     
     
         14 . The assembly of  claim 9 , wherein the second angle is greater than the first angle. 
     
     
         15 . The assembly of  claim 9 , wherein the second angle is greater than or equal to 100 degrees. 
     
     
         16 . The assembly of  claim 8 , wherein the inner surfaces form a non-cylindrical surface with a first angle measured from a horizontal plane of the internal bore. 
     
     
         17 . The assembly of  claim 8 , wherein the outer surfaces form a non-cylindrical surface with a second angle measured from a horizontal plane of the internal bore. 
     
     
         18 . The assembly of  claim 8 , wherein the inner surfaces include a decreasing radius of curvature from a proximal end to a distal end of the coupling element. 
     
     
         19 . The assembly of  claim 8 , wherein the outer surfaces include a decreasing radius of curvature from a proximal end to a distal end of the bottom saddle. 
     
     
         20 . The assembly of  claim 8 , wherein the compression nut advances the bottom saddle distally towards the internal bore such that outer surfaces engage more of the inner surfaces to increase the frictional engagement with the head portion.