Monoplanar bone anchoring device with selectable pivot plane

Abstract

A bone anchoring device is provided including a receiving part for receiving a rod, the receiving part having a longitudinal axis, a first bore coaxial with the longitudinal axis and a second bore; an anchoring element having a first end for insertion into a bone and a second end positionable within the second bore, the second end including a head. The anchoring element is movable relative to the receiving part in a limited angular range about the longitudinal axis, the angular range lying in a single plane. The bone anchoring device further includes a guiding member configured to rotate in the first bore, wherein the head of the anchoring element is connected to the guiding member and wherein a form-fit connection between the head and the guiding member limits the movement of the anchoring element to the single plane. A first locking element acts on the guiding member to fix the rotational position of the guiding member and a second locking element acts on the head to fix the head relative to the receiving part.

1 . A bone anchoring device comprising:
 a receiving part for receiving a rod, the receiving part having a longitudinal axis, a first bore coaxial with the longitudinal axis and a second bore;   an anchoring element having a first end for insertion into the bone and a second end positionable within the second bore, the second end including a head;   the anchoring element being movable relative to the receiving part in a limited angular range about the longitudinal axis, the angular range lying in the single plane;   a guiding member configured to rotate in the first bore; wherein the head of the anchoring element is guided by the guiding member and wherein a form-fit connection limits the movement of the anchoring element to the single plane;   a locking device comprising a first locking element that acts on the guiding member to fix the rotational position of the guiding member and a second locking element that acts on the head to fix the head.   
     
     
         2 . The bone anchoring device of  claim 1 , wherein the receiving part comprises a U-shaped recess for inserting the rod by means of which two open legs are formed and wherein an internal thread is provided at the open legs. 
     
     
         3 . The bone anchoring device of  claim 2 , wherein the first locking element comprises an outer thread which is configured to work in combination with the internal thread on said legs and wherein the coaxial bore comprises an internal thread, which is configured to work in combination with an outer thread on the second locking element. 
     
     
         4 . The bone anchoring device of  claim 1 , further comprising a pressure element having a recess shaped to support the rod and configured to be arranged between the guiding member and the locking device. 
     
     
         5 . The bone anchoring device of  claim 4 , wherein the pressure element is configured to exert pressure onto the guiding member but not on the head. 
     
     
         6 . The bone anchoring device of  claim 4 , wherein the pressure element is substantially cylindrical and has a first end facing the locking device and a second end facing the head and wherein a recess for the head is provided at the second end that is sized so that a portion of the head is accommodated therein without contacting the pressure element. 
     
     
         7 . The bone anchoring device of  claim 6 , wherein the pressure element has a recess at its first end and wherein the second locking element can extend into the recess without contacting the pressure member. 
     
     
         8 . The bone anchoring device of  claim 1 , wherein an edge bounding the second bore is asymmetric to permit the bone anchoring element to pivot at a larger angle at a first location of the edge than at another location of the edge relative to the longitudinal axis. 
     
     
         9 . The bone anchoring device of  claim 8 , wherein the receiving part has a countersunk area at the edge bounding the second bore. 
     
     
         10 . The bone anchoring device of  claim 8 , wherein a seat member is provided that has a seat for the head and that can be assembled and mounted to the receiving part to define an edge bounding the second bore that is asymmetric to permit the bone anchoring element to pivot at a larger angle at a first location of the edge than at another location of the edge relative to the longitudinal axis. 
     
     
         11 . The bone anchoring device of  claim 10 , wherein the seat member is configured to rotate in the second bore before locking. 
     
     
         12 . The bone anchoring device of  claim 10 , wherein the seat for the head in the seat member is spherical. 
     
     
         13 . The bone anchoring device of  claim 10 , wherein the seat member has a recess at its edge for a form-fit connection to the head. 
     
     
         14 . The bone anchoring device of  claim 1 , wherein the head has a substantially spherical segment shape in which the rotational axis of the sphere extends perpendicular to the shank axis. 
     
     
         15 . A method of medical treatment using an anchoring element having a first end and a second end, the second end including a head; a receiving part for receiving a rod, the receiving part having a longitudinal axis, a first bore coaxial with the longitudinal axis and a second bore; and a locking device comprising a first locking element and a second locking element; wherein the head and the guiding member are configured to have a form-fit connection that limits the movement of the anchoring element to a single plane;
 the method comprising:
 inserting the anchoring element into the receiving part; 
 positioning the second end of the anchoring element within the second bore of the receiving part; 
 inserting the guiding member into the first bore, wherein the guiding member is rotatable inside the first bore; 
 assembling the head with the guiding member to form the form-fit connection between the head and the guiding member that limits the movement of the anchoring element to a single plane relative to the guiding member; 
 inserting a rod into the first bore; 
 fixing the rotational position of the guiding member with the first locking member; and 
 fixing the head with the second locking member.