Bone anchoring device

Abstract

A bone anchoring device has an anchoring element, a receiving portion, and a pressure element. The anchoring element includes a shank to be anchored in a bone or a vertebra and a head, the head having an exterior surface with a spherical segment-shaped portion. The shank and the head are separate parts. The receiving portion includes a first end, a second end opposite to the first end, a longitudinal axis passing through the two ends, a bore coaxial with the longitudinal axis, and a first region adjacent to the second end for receiving a spherical segment-shaped section of the head. The pressure element exerts pressure on the head to lock the head in the receiving portion. The head has a hollow inner portion to receive a free end portion of the shank and wherein the head and the end portion are formed such that the end portion can be elastically clamped by the head.

1 .- 13 . (canceled) 
   
   
       14 . A bone anchoring device comprising:
 an anchoring element comprising:
 a shank to be anchored in a bone or a vertebra, the shank having a conically shaped first end portion having a free end and a second end opposite the free end, the diameter of the conically shaped first end portion increasing in a direction from the second end to the free end; 
 a head having an exterior surface with a spherical segment-shaped portion and a hollow inner portion to receive the first end portion of the shank, the head comprising a surface facing the free end of the shank to form an abutment preventing the shank from moving through the hollow inner portion past the abutment when the shank is received in the hollow inner portion; and 
 wherein said shank and said head are separate parts; 
   a receiving portion comprising a first end, a second end opposite to the first end, a longitudinal axis passing through the two ends, a bore coaxial with the longitudinal axis, and a first region adjacent to the second end for receiving the spherical segment-shaped section of said head; and   a pressure element which exerts pressure on said head to lock said head in the receiving portion, the pressure element having a spherical recess on a side facing the head, which cooperates with the head when pressure is exerted   
   
   
       15 . The bone anchoring device of  claim 14 , wherein the hollow inner portion has a mating shape corresponding to the conically shaped end portion 
   
   
       16 . The bone anchoring device of  claim 14 , wherein said conical shape is a truncated cone. 
   
   
       17 . The bone anchoring device of  claim 14 , wherein a cone angle of the conically shaped end portion is selected such that a self-locking occurs between the head and the end portion. 
   
   
       18 . The bone anchoring device of  claim 17 , wherein said angle is between about 2 and 10 degrees. 
   
   
       19 . The bone anchoring device according to  claim 14 , wherein the head comprises a spring-like edge facing towards the end portion of the shank. 
   
   
       20 . The bone anchoring device of  claim 14 , wherein the head comprises one or more slits which are directed substantially parallel to the rotational axis of the head and are open on a side facing the end portion of the shank. 
   
   
       21 . The bone anchoring device of  claim 14 , wherein the hollow inner portion is shaped as a hollow truncated cone and extends from one end of the head to an opposite end. 
   
   
       22 . The bone anchoring device of  claim 14 , wherein said receiving portion has a U-shaped recess extending from the first end in the direction of the second end which forms a channel to receive a rod. 
   
   
       23 . A bone anchoring assembly comprising:
 a shank to be anchored in a bone or a vertebra and a head, the shank having a conically shaped first end portion having a free end and a second end opposite the free end, the diameter of the conically shaped first end portion increasing in a direction from the second end to the free end;   a head having an exterior surface with a spherical segment-shaped portion and a hollow inner portion to receive the first end portion of the shank, the head comprising a surface facing the free end of the shank to form an abutment preventing the shank from moving through the hollow inner portion past the abutment when the shank is received in the hollow inner portion; and   wherein said shank and said head are separate parts;   a receiving portion comprising a first end, a second end opposite to the first end, a longitudinal axis passing through the two ends, a bore coaxial with the longitudinal axis, and a first region adjacent to the second end for receiving the spherical segment-shaped section of said head;   a pressure element which exerts pressure on said head to lock said head in the receiving portion, the pressure element having a spherical recess on a side facing the head, which cooperates with the head when pressure is exerted; and   a tool for separating the shank and the head, the tool comprising an elongated member having an end configured to engage the abutment to separate the shank from the head.   
   
   
       24 . The bone anchoring assembly of  claim 23 , wherein the abutment includes an opening configured to receive the end of the tool. 
   
   
       25 . The bone anchoring assembly of  claim 24 , wherein the opening of the abutment includes an inner thread, and wherein the end of the tool comprises an outer thread configured to engage the inner thread of the opening. 
   
   
       26 . A method of attaching a bone anchoring device to a bone or vertebrae, the bone anchoring device comprising an anchoring element comprising a shank to be anchored in a bone or a vertebra, the shank having a conically shaped first end portion having a free end and a second end opposite the free end, the diameter of the conically shaped first end portion increasing in a direction from the second end to the free end, an elastic head having an exterior surface with a spherical segment-shaped portion and a hollow inner portion to receive the first end portion of the shank, wherein said shank and said head are separate parts, a receiving portion comprising a first end, a second end opposite to the first end, a longitudinal axis passing through the two ends, a bore coaxial with the longitudinal axis, and a first region adjacent to the second end for receiving the spherical segment-shaped section of said head, and a pressure element which exerts pressure on said head to lock said head in the receiving portion, the pressure element having a spherical recess on a side facing the head, which cooperates with the head when pressure is exerted, the method comprising:
 inserting the conically shaped first end portion of the shank in the bore of the receiving portion from the second end of the receiving portion;   attaching the shank to the bone or vertebrae; and   attaching the shank to the elastic head.   
   
   
       27 . The method of  claim 26 , wherein the shank is attached to the bone or vertebrae after being inserted in the bore of the receiving portion. 
   
   
       28 . The method of  claim 26 , wherein the shank is attached to the bone or vertebrae before being inserted in the bore of the receiving portion. 
   
   
       29 . The method of  claim 26 , wherein attaching the shank to the elastic head comprises inserting the first end portion of the shank in the hollow inner portion of the head, wherein the head comprises a surface facing the free end of the shank to form an abutment preventing the shank from moving through the hollow inner portion past the abutment when the shank is inserted in the hollow inner portion. 
   
   
       30 . The method of  claim 26 , wherein attaching the shank to the elastic head comprises the free end of the shank elastically expanding a spring-like edge of the head facing towards the end portion of the shank. 
   
   
       31 . The method of  claim 26 , wherein attaching the shank to the elastic head comprises one or more slits of the head which are directed substantially parallel to the rotational axis of the head and are open on a side facing the end portion of the shank causing the head to elastically receive the end portion of the shank in the hollow inner portion of the head. 
   
   
       32 . The method of  claim 26 , wherein the hollow inner portion has a mating shape corresponding to the conically shaped end portion