Bone fixation apparatus

Abstract

A bone fixation apparatus adapted for use in spinal stabilization. The apparatus includes a threaded bone screw having a spherical head that is received in a receiver cup. The receiver cup also includes a slot or groove through which a support rod passes. A saddle is positioned in the receiver cup below the support rod and above the head of the threaded bone screw. Alignment flanges are positioned partially around an opening on the receiver cup opposite the bone screw. A cap having internal grooves corresponding to the alignment flanges mates with the receiver cup. The cap may be positioned onto the receiver cup in a first orientation and secured to the receiver cup by rotating approximately one quarter turn. A compression member is screwed into internal threads on an opening of the cup to provide pressure on the support rod, thereby fixing the rod to the receiver cup.

1 . A bone fixation apparatus, comprising: 
 a receiver cup comprising at least one receiver engagement portion, said receiver engagement portion comprising two or more opposed cup flanges, each extending partially around a top surface of said receiver cup, the receiver cup additionally comprising one or more mating stops; and    a cap comprising at least one cap engagement portion that slidably engages the at least one receiver engagement portion when rotated on the receiver cup less than one full rotation, said cap engagement portion comprising two or more opposed cap flanges, each extending partially around a bottom surface of said cap, the cap additionally comprising one or more mating stops;    wherein said mating stops on said receiver engagement portion and said mating stops on said cap engagement portion comprise mating sets of at least one recess and at least one pin;    wherein each pin extends through an opening in said receiver engagement portion or said cap engagement portion; and    wherein said mating stops on said receiver engagement portion and said mating stops on said cap engagement portion are configured to engage said cap to said receiver cup upon less than one full rotation of said cap on said receiver cup.    
   
   
       2 . The bone fixation apparatus of  claim 1 , further comprising: 
 a bone fastener having a head and a body, the head captured in the receiver cup and the body extending through the receiver cup; and    a support rod having a portion extending into the receiver cup through at least one cutout in the receiver cup.    
   
   
       3 . The bone fixation apparatus of  claim 2 , further comprising: 
 a compression member coupled to the cap and configured to fix the position of the support rod relative to the receiver cup.    
   
   
       4 . The bone fixation apparatus of  claim 2 , further comprising a saddle interposed between the support rod and the head of the bone fastener.  
   
   
       5 . The bone fixation apparatus of  claim 2 , wherein the bone fastener comprises a threaded fastener.  
   
   
       6 . The bone fixation apparatus of  claim 2 , wherein the bone fastener comprises a pedicle screw.  
   
   
       7 . The bone fixation apparatus of  claim 1 , wherein the at least one receiver engagement portion surrounds approximately one half of a perimeter of the receiver cup.  
   
   
       8 . The bone fixation apparatus of  claim 1 , wherein the at least one cap engagement portion slidably engages the at least one receiver engagement portion when rotated on the receiver cup less than one half rotation.  
   
   
       9 . The bone fixation apparatus of  claim 1 , wherein the at least one cap engagement portion slidably engages the at least one receiver engagement portion when rotated on the receiver cup by one quarter rotation.  
   
   
       10 . A bone fixation apparatus, comprising: 
 a receiver cup comprising at least one receiver engagement portion, said receiver engagement portion comprising two or more opposed cup flanges, each extending partially around a top surface of said receiver cup; and    a cap comprising at least one cap engagement portion that slidably engages the at least one receiver engagement portion when rotated on the receiver cup less than one full rotation, said cap engagement portion comprising two or more opposed cap flanges, each extending partially around a bottom surface of said cap,    the cap additionally comprising a notch on the top surface of the cap aligned with the opposed flanges indicating flange position relative to the receiver cup when in an engaged configuration.    
   
   
       11 . The hone fixation apparatus of  claim 10 , further comprising: 
 a bone fastener having a head and a body, the head captured in the receiver cup and the body extending through the receiver cup; and    a support rod having a portion extending into the receiver cup through at least one cutout in the receiver cup.    
   
   
       12 . The bone fixation apparatus of  claim 11 , further comprising: 
 a compression member coupled to the cap and configured to fix the position of the support rod relative to the receiver cup.    
   
   
       13 . The bone fixation apparatus of  claim 11 , further comprising a saddle interposed between the support rod and the head of the bone fastener.  
   
   
       14 . The bone fixation apparatus of  claim 11 , wherein the bone fastener comprises a threaded fastener.  
   
   
       15 . The bone fixation apparatus of  claim 11 , wherein the bone fastener comprises a pedicle screw.  
   
   
       16 . The bone fixation apparatus of  claim 10 , wherein the at least one receiver engagement portion surrounds approximately one half of a perimeter of the receiver cup.  
   
   
       17 . The bone fixation apparatus of  claim 10 , wherein the at least one cap engagement portion slidably engages the at least one receiver engagement portion when rotated on the receiver cup less than one half rotation.  
   
   
       18 . The bone fixation apparatus of  claim 10 , wherein the at least one cap engagement portion slidably engages the at least one receiver engagement portion when rotated on the receiver cup by one quarter rotation.