Bone fixation assembly

Abstract

A bone fixation assembly and associated method. The bone fixation assembly includes a bone fastener having a head and a bone-engaging portion, a receiver defining an opening along a first axis for receiving the bone fastener at a variable angle, and at least one supporting augment coupled to the bone fastener. The receiver has an inner articulation surface at a lower portion of the opening and matingly articulates with the supporting augment.

1 . A bone fixation assembly comprising: 
 a bone fastener having a head and a bone-engaging portion;    a receiver defining an opening along a first axis for receiving the bone fastener at a variable angle, the receiver having an inner articulation surface at a lower portion of the opening; and    at least one supporting augment coupled to the bone fastener and matingly articulable with the articulation surface of the receiver.    
     
     
         2 . The bone fixation assembly of  claim 1 , wherein the at least one supporting augment includes two separate supporting augments.  
     
     
         3 . The bone fixation assembly of  claim 1 , wherein the articulation surface is substantially spherical and wherein the supporting augment has an outer mating surface that is substantially spherical.  
     
     
         4 . The bone fixation assembly of  claim 1 , wherein a lower end of the opening is configured for receiving the head of the bone fastener therethrough.  
     
     
         5 . The bone fixation assembly of  claim 4 , further comprising a fastener ring, the fastener ring couplable to the head of the bone fastener such that the fastener ring can be inserted assembled to the bone fastener from the lower end of the opening.  
     
     
         6 . The bone fixation assembly of  claim 5 , wherein the fastener ring is supportable on a groove of the supporting augment.  
     
     
         7 . The bone fixation assembly of  claim 6 , wherein the fastener ring is a split ring.  
     
     
         8 . The bone fixation assembly of  claim 6 , wherein the supporting augment is shaped for allowing variable angulation of the fastener.  
     
     
         9 . The bone fixation assembly of  claim 2 , wherein each supporting augment includes a notch on an upper surface of the augment.  
     
     
         10 . The bone fixation assembly of  claim 8 , wherein each supporting augment includes two oppositely inclined end surfaces.  
     
     
         11 . The bone fixation assembly of  claim 9 , wherein each supporting augment is shaped for partial overlapping about the notch during assembly.  
     
     
         12 . The bone fixation assembly of  claim 8 , wherein the supporting augment is further shaped for preventing removal of the fastener when the ring is coupled to the supporting augment and to the head of the fastener.  
     
     
         13 . The bone fixation assembly of  claim 1 , further comprising a fastener cap for coupling the head of the fastener to an inner surface of the receiver.  
     
     
         14 . The bone fixation assembly of  claim 13 , further comprising a cap ring for coupling the fastener cap and the receiver.  
     
     
         15 . The bone fixation assembly of  claim 14 , wherein the receiver defines a channel extending along a second axis generally perpendicular to the first axis.  
     
     
         16 . The bone fixation assembly of  claim 15 , wherein the channel is shaped for receiving a fixation rod above the fastener cap.  
     
     
         17 . The bone fixation assembly of  claim 14 , wherein the cap ring is a split ring.  
     
     
         18 . A method for spinal fixation comprising: 
 providing a receiver defining an opening along a first axis for receiving a bone fastener at a variable angle, the receiver having an inner articulation surface at a lower portion of the opening;    inserting the head of the bone fastener into the opening;    inserting at least one supporting augment into the opening, the at least one supporting augment articulable with the articulation surface;    coupling the at least one supporting augment to the head of the bone fastener; and    varying the angle of the bone fastener relative to the first axis by articulating the at least one supporting augment relative to the articulation surface.    
     
     
         19 . The method of  claim 18 , wherein coupling the at least one augment is performed after inserting the head of the bone fastener into the opening.  
     
     
         20 . The method of  claim 18 , wherein inserting the head of the bone fastener into the opening includes inserting the head through a lower end of the opening.  
     
     
         21 . The method of  claim 20 , wherein coupling the at least one supporting augment to the head of the bone fastener includes preventing the head of the bone fastener from withdrawal through the opening.  
     
     
         22 . The method of  claim 18 , wherein coupling the at least one supporting augment to the head of the bone fastener includes coupling a retention member to the at least one supporting augment and to the head of the bone fastener.  
     
     
         23 . The method of  claim 20 , further comprising inserting a cap through an upper end of the opening for engaging the head of the bone fastener.