Bone anchoring element with thread that can be unscrewed
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 method for using a bone anchoring element for anchoring an external device in a bone, the method comprising:
providing a bone anchoring element comprising:
a head section that can be connected to the external device; and
a shaft, which 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,
wherein the bone anchoring element comprises a first cross-sectional shape; forming a hole in the bone having a second cross-section with a shape corresponding to that of the first cross-section and with dimensions equal to or slightly less than the dimensions of the first cross-sectional shape;
inserting the bone anchoring element into the hole without screwing the bone anchoring element into the hole; and
rotating the bone anchoring element around its longitudinal axis to a predetermined angle to engage the bone thread in the bone.
2. The method according to claim 1 , wherein the step of forming a hole comprises drilling a hole and removing bone material with a rasp to obtain the desired cross-sectional shape.
3. The method according to claim 1 , wherein the step of forming a hole comprises cuffing the bone with a transverse cutter or with a profile-forming cutter.
4. The method according to claim 1 , wherein the head section comprises a receiving member for connecting to a rod and the method further comprises connecting the receiving member to a rod.
5. The method of claim 4 , wherein the method further comprises repeating the steps for a plurality of bone anchoring elements and connecting the plurality of bone anchoring elements with the rod.
6. The method of claim 1 , further comprising a step of removing the bone anchoring element by unscrewing it.