Bone anchoring element with thread that can be unscrewed

Abstract

A bone anchoring element ( 1 ) for anchoring an external device in a bone is described. A head ( 2 ) capable of connection to the external device is provided with a shaft ( 3 ) that can be anchored in a bone. A predetermined section of the shaft ( 3 ) has a bone thread ( 5 ). Moreover, the shaft ( 3 ) also has at least one bone thread-free surface ( 6,7; 11,12; 16,17; 21,22,23 ) that extends from a first end to a second end of the predetermined section essentially along the direction of the shaft axis. The bone anchoring element ( 1 ), thus provided, is pressed or soft-hammered into a hole ( 8, 28 ) previously generated in the bone and fixed in the bone by rotation by a predetermined angle. If the bone anchoring element has to be removed this can be achieved by unscrewing it in the standard fashion. The disclosure also describes methods for using the bone anchoring element.

1 . A bone anchoring element for anchoring an external device in a bone, the bone anchoring element comprising:
 a head section that can be connected to the external device; and   a shaft that can be anchored in the bone and is connected to the head section, having a longitudinal axis;   the shaft comprising:
 a bone thread on a predetermined section of the shaft, the bone thread having a crest, and a first end and a second end spaced apart longitudinally along the shaft, and 
 at least one bone thread-free surface that extends along the direction of the shaft axis from the first end to the second end of the bone thread. 
   
   
   
       2 . The bone anchoring element according to  claim 1 , wherein a first distance between the bone thread-free surface and the shaft axis is smaller than a second distance between the crest of the bone thread and the shaft axis. 
   
   
       3 . The bone anchoring element according to  claim 1 , further comprising a plurality of bone thread-free surfaces. 
   
   
       4 . The bone anchoring element according to  claim 3 , wherein the shaft further comprises a circumference and wherein the plurality of bone thread-free surfaces are positioned approximately at equal distances from each other around the shaft circumference. 
   
   
       5 . The bone anchoring element according to  claim 1 , further comprising two or three bone thread-free surfaces. 
   
   
       6 . The bone anchoring element according to  claim 1 , wherein at least one bone thread-free surface has a geometry such that a cross section of the shaft perpendicular to the longitudinal axis of the shaft shows the surface as a straight line. 
   
   
       7 . The bone anchoring element according to  claim 1 , wherein at least one bone thread-free surface has a concave shape. 
   
   
       8 . The bone anchoring element according to  claim 1 , wherein the bone thread-free surface extends parallel to the shaft axis. 
   
   
       9 . The bone anchoring element according to  claim 1 , wherein the bone thread-free surface extends from the first end to the second end of the bone thread in a helical form. 
   
   
       10 . The bone anchoring element according to  claim 1 , wherein the shaft has an end opposite to the head section and the predetermined section extends to the end of the shaft. 
   
   
       11 . The bone anchoring element according to  claim 1 , the shaft further comprising an end opposite to the head section, the end comprising a tip. 
   
   
       12 . The bone anchoring element according to  claim 1 , wherein at least one bone thread-free surface is roughened or coated in order to improve the in-growth of bone. 
   
   
       13 . The bone anchoring element according to  claim 1 , wherein the shaft comprises a shape memory alloy. 
   
   
       14 . The bone anchoring element according to  claim 1 , wherein the head section comprises a receiving member for connecting to a rod. 
   
   
       15 . The bone anchoring element according to  claim 1 , wherein the head section is fixedly connected to the shaft. 
   
   
       16 . The bone anchoring element according to  claim 1 , wherein the head section is connected to the shaft in an articulated arrangement. 
   
   
       17 - 22 . (canceled) 
   
   
       23 . A bone anchoring element comprising a shaft to be anchored in the bone, the shaft having a longitudinal axis; wherein the shaft comprises a bone thread on a predetermined section of the shaft, the bone thread having a crest and a first end and a second end spaced apart longitudinally along the shaft, and
 at least one bone thread free surface that extends along the direction of the shaft axis from the first end to the second end of the bone thread.   
   
   
       24 . The bone anchoring element of  claim 23 , wherein the bone anchoring element is formed as a pin. 
   
   
       25 . The bone anchoring element of  claim 23 , wherein the bone anchoring element is formed as a marrow nail.