Rod and anchor system and method for using

Abstract

A method of conducting a surgical procedure including implanting an anchor into a bone, wherein the anchor comprises a receiving portion and a screw, the screw including a screw head contained within the receiving portion and pivotally engageable with a surface of the receiving portion, and wherein the receiving portion and the screw comprising a different material. The method further includes selecting a rod from a group of rod types and coupling the rod with the receiving portion to stabilize a position of a portion of the spine.

1 - 20 . (canceled) 
     
     
         21 . A bone anchor comprising:
 a receiving portion comprising a recess and a pair of arms defining an implant cavity between the arms;   a crown contained within the receiving portion;   a ring; and   a screw comprising a screw head contained within the receiving portion, the screw head extending through the ring.   
     
     
         22 . The bone anchor recited in  claim 21 , wherein the receiving portion comprises a first material and the screw comprises a second material, the second material being different than the first material. 
     
     
         23 . The bone anchor recited in  claim 22 , wherein the second material has a modulus of elasticity different than a modulus of elasticity of the first material. 
     
     
         24 . The bone anchor recited in  claim 21 , wherein the ring comprises a first material and the screw and the crown each comprise a second material, the second material being different than the first material. 
     
     
         25 . The bone anchor recited in  claim 24 , wherein the second material has a modulus of elasticity different than a modulus of elasticity of the first material. 
     
     
         26 . The bone anchor recited in  claim 21 , wherein the receiving portion and the ring each comprise a first material and the screw comprises a second material, the second material being different than the first material. 
     
     
         27 . The bone anchor recited in  claim 26 , wherein the second material has a modulus of elasticity different than a modulus of elasticity of the first material. 
     
     
         28 . The bone anchor recited in  claim 21 , wherein the receiving portion and the ring each comprise a first material and the crown comprises a second material, the second material being different than the first material. 
     
     
         29 . The bone anchor recited in  claim 28 , wherein the second material has a modulus of elasticity different than a modulus of elasticity of the first material. 
     
     
         30 . The bone anchor recited in  claim 21 , further comprising analogs including a rod, the rod being configured for disposal in the implant cavity. 
     
     
         31 . The bone anchor recited in  claim 30 , wherein the rod comprises a first material and the screw comprises a second material, the second material being different than the first material. 
     
     
         32 . The bone anchor recited in  claim 31 , wherein the second material has a modulus of elasticity different than a modulus of elasticity of the first material. 
     
     
         33 . A bone anchor comprising:
 a receiving portion comprising a recess and a pair of arms defining an implant cavity between the arms;   a crown contained within the receiving portion, the crown including opposite first and second surfaces;   a ring; and   a screw comprising a screw head contained within the receiving portion, the screw head extending through the ring, the first surface engaging the screw head,   wherein the ring is disposed in the recess to prevent the screw from translating axially relative to the receiving portion in one direction, and   wherein the receiving portion and the ring each comprise a first material and the screw and the crown each comprise a second material, the second material being different than the first material.   
     
     
         34 . The bone anchor recited in  claim 33 , wherein the first material has a yield strength greater than a yield strength of the second material. 
     
     
         35 . The bone anchor recited in  claim 33 , wherein the implant cavity is U-shaped. 
     
     
         36 . The bone anchor recited in  claim 33 , wherein the second surface is concavely curved. 
     
     
         37 . The bone anchor recited in  claim 33 , wherein the screw is configured to pivot with respect to the receiving portion in a plurality of planes. 
     
     
         38 . The bone anchor recited in  claim 33 , wherein the receiving portion comprises an inner surface defining a chamber, the recess extending into the inner surface such that the recess is in communication with the chamber, the screw head and the crown being positioned in the chamber such that a first portion of the screw head engages the crown and a second portion of the screw head engages the inner surface. 
     
     
         39 . The bone anchor recited in  claim 33 , wherein:
 the receiving portion comprises an inner surface defining a chamber, the recess extending into the inner surface such that the recess is in communication with the chamber, the screw head and the crown being positioned in the chamber; and   the ring is positioned in the recess and engages the screw head to retain the screw head in the chamber.   
     
     
         40 . The bone anchor recited in  claim 39 , wherein the ring is spaced apart from the crown when the screw head and the crown are positioned in the chamber. 
     
     
         41 . The bone anchor recited in  claim 33 , wherein:
 the receiving portion comprises an inner surface defining a chamber, the recess extending into the inner surface such that the recess is in communication with the chamber, the chamber being in communication with a distal opening of the receiving portion, the distal opening having a maximum width that is greater than that of the crown; and   side surfaces of the crown engage the inner surface of the receiving portion that defines the chamber.   
     
     
         42 . The bone anchor recited in  claim 33 , wherein an upper surface of the screw head engages the first surface of the crown, the first surface of the crown defining an aperture having a semi-hemispherical shape. 
     
     
         43 . The bone anchor recited in  claim 33 , wherein:
 the implant cavity is defined by inner surfaces of the arms, the inner surfaces of the arms each comprising a threaded portion; and   the bone anchor further comprises a set screw with threads configured to mate with the threaded portions to couple the set screw to the bone anchor.   
     
     
         44 . The bone anchor recited in  claim 43 , wherein the set screw comprises the first material 
     
     
         45 . The bone anchor recited in  claim 33 , wherein the first material is cobalt chromium molybdenum. 
     
     
         46 . The bone anchor recited in  claim 33 , wherein the second material is titanium. 
     
     
         47 . The bone anchor recited in  claim 33 , wherein the receiving portion and the screw have a difference in elemental weight percent of at least about 5 wt %. 
     
     
         48 . The bone anchor recited in  claim 33 , wherein the first material is cobalt chromium molybdenum and the second material is titanium. 
     
     
         49 . The bone anchor recited in  claim 33 , wherein the ring is a split ring having a gap in a circumference of the ring. 
     
     
         50 . A surgical system comprising:
 a spinal rod; and   a bone anchor comprising:
 a receiving portion comprising a recess and a pair of arms defining an implant cavity between the arms, the implant cavity being configured for disposal of the rod; 
 a crown contained within the receiving portion, the crown including opposite first and second surfaces; 
 a ring; and 
 a screw comprising a screw head contained within the receiving portion, the screw head extending through the ring, the first surface engaging the screw head, 
   wherein the ring is disposed in the recess to prevent the screw from translating axially relative to the receiving portion in one direction, and   wherein the receiving portion and the ring each comprise a first material and the screw and the crown each comprise a second material, the second material being different than the first material.   
     
     
         51 . The surgical system recited in  claim 50 , wherein:
 the rod comprises a third material that is different than the first material and the second material; and   at least one of the first material and the second material have a greater yield strength than the third material.   
     
     
         52 . A surgical system comprising:
 a spinal rod; and   a bone anchor comprising:
 a set screw comprising a threaded outer surface; 
 a receiving portion comprising a recess and a pair of arms defining an implant cavity between the arms, the implant cavity being configured for disposal of the rod, the arms each including a threaded portion mated with the threaded outer surface to couple the set screw to the receiving portion; 
 a crown contained within the receiving portion, the crown including opposite first and second surfaces; 
 a ring; and 
 a screw comprising a screw head contained within the receiving portion, the screw head extending through the ring, the first surface engaging the screw head, 
   wherein the ring is disposed in the recess to prevent the screw from translating axially relative to the receiving portion in one direction,   wherein the set screw, the receiving portion and the ring each comprise a first material and the rod, the screw and the crown each comprise a second material, the second material being different than the first material.