Bone anchoring device

Abstract

A bone anchoring device includes an anchoring element having a shaft and a head; a receiving part having a top end, a bottom end, a rod recess, a coaxial bore, and a seat; and a pressure element that is movable within the bore. The head is pivotable with respect to the receiving part and can be fixed at an angle by exerting pressure via the pressure element onto the head. The pressure element has an outer wall portion having a recess or a projection. The receiving part has an inner wall portion having a recess or a projection that cooperates with the recess or projection of the pressure element. The pressure element is configured to assume a first position within the receiving part in which the recess and the projection interact to allow the pressure element to exert a preload onto the head and the head is prevented from freely pivoting but is not locked.

1 . A bone anchoring device comprising:
 an anchoring element having a shaft for anchoring in the bone and a head,   a receiving part having a longitudinal axis from a top end to a bottom end, a rod recess for receiving a rod therein, a coaxial bore extending from the top end in the direction of the bottom end and a seat for receiving the head near the bottom end, and   a pressure element that is movable within the bore;
 wherein the head is pivotable with respect to the receiving part and can be fixed at an angle by exerting pressure via the pressure element onto the head; 
 wherein the pressure element has an outer wall portion having a first feature, wherein the first feature is one of a recess or a projection and wherein the receiving part has an inner wall portion having a second feature, wherein the second feature is the other of a recess or a projection that cooperates with the first feature of the pressure element; 
 wherein the pressure element is configured to assume a first position within the bore of the receiving part wherein the recess and the projection interact to allow the pressure element to exert a preload onto the head and the head is prevented from freely pivoting but is not locked; 
 wherein the pressure element is movable in a first axial direction parallel to the longitudinal axis from an assembly position spaced from the bottom end of the receiving part to the first position closer to the bottom end of the receiving part; and 
 wherein when the pressure element is in the assembly position, the projection and the recess are aligned in the first axial direction and the head is capable of freely pivoting. 
   
     
     
         2 . The bone anchoring device of  claim 1 , wherein the pressure element is configured to assume a second position wherein the pressure element exerts a locking pressure on the head such that the head is locked. 
     
     
         3 . The bone anchoring device of  claim 1 , wherein the assembly position is one of several assembly positions wherein the head is capable of freely pivoting. 
     
     
         4 . The bone anchoring device of  claim 1 , wherein the projection and the recess are sized to form an interference fit between the projection and the recess when the pressure element is in the first position. 
     
     
         5 . The bone anchoring device of  claim 3 , wherein the projection and the recess are sized to form a form-fit connection when the pressure element is in one of the assembly positions where the projection is engaged with the recess. 
     
     
         6 . The bone anchoring device of  claim 1 , wherein a radial dimension of the recess varies in a direction coaxial with the bore axis. 
     
     
         7 . The bone anchoring device according to  claim 1 , wherein the radial dimension of the projection that engages the recess is substantially constant. 
     
     
         8 . The bone anchoring device according to  claim 1 , wherein the projection is provided at the inner wall portion of the receiving part and the recess is provided at the outer wall portion of the pressure element. 
     
     
         9 . The bone anchoring device of  claim 1 , wherein the recess is a notch that extends coaxially with the bore axis of the receiving part. 
     
     
         10 . The bone anchoring device according to  claim 8 , wherein the recess is a notch with a substantially V-shaped cross section that is open at the end of the pressure element facing the head of the bone anchoring element and that has a decreasing depth towards its end opposite to the head. 
     
     
         11 . The bone anchoring element according to  claim 1 , wherein the projection is a tip obtained preferably by crimping. 
     
     
         12 . The bone anchoring device of  claim 1 , wherein the pressure element has a rod recess on its side facing away from the head for receiving the rod that is aligned to the rod recess of the receiving part and wherein the projection and the recess are arranged at 90° with respect to the rod recesses. 
     
     
         13 . The bone anchoring device according to  claim 1 , wherein at least two pairs of cooperating recesses and projections are provided. 
     
     
         14 . The bone anchoring device according to  claim 3 , wherein the pressure element is movable out of the first position into one of the assembly positions by pressing the head against the pressure element. 
     
     
         15 . The bone anchoring device of  claim 1 , wherein a fixation element is provided for fixing the rod. 
     
     
         16 . The bone anchoring device of  claim 1 , wherein the pressure element is continuously movable from the assembly position in which the head is freely pivotable to the first position by exerting pressure onto an end of the pressure element facing away from the head of the bone anchoring element. 
     
     
         17 . The bone anchoring device of  claim 1 , wherein the receiving part and the pressure element are each formed in one piece. 
     
     
         18 . The bone anchoring device of  claim 17 , wherein the projection and the recess are configured to cooperate without spring portions provided at either the receiving part or the pressure element. 
     
     
         19 . The bone anchoring device of  claim 17 , wherein the pressure element is formed integrally with the first feature, and
 wherein the receiving part is formed integrally with the second feature.