Locking spiral anchoring system
View Patent ↗A bone fixation screw comprises a proximal head being configured to lockingly engage a bone plate hole and a substantially helical shaft extending distally from the head along a substantially helical path. The head and the shaft are rotatably coupled to each other so that the shaft can rotate about a central longitudinal axis thereof with respect to the head.
1. A bone screw, comprising:
a proximal head being configured to lockingly engage a bone plate hole; and
a substantially helical shaft extending distally from the head along a substantially helical path,
wherein the head and the shaft are rotatably coupled to each other so that the shaft can rotate about a central longitudinal axis thereof with respect to the head and wherein the head is rotatably coupled to a circular coupling attached to the shaft.
2. The bone screw according to claim 1 , wherein the head includes a driver engaging structure in the form of a recess formed thereon.
3. The bone screw according to claim 1 , wherein the head comprises an external thread having a pitch P 1 for lockingly engage the bone plate hole, and wherein the shaft is formed in a helical shape having the pitch P 2 .
4. The bone screw according to claim 3 , wherein the pitch P 2 of the shaft is greater than the pitch P 1 of the external thread and wherein the ratio P 2 /P 1 is larger than 7.
5. The bone screw according to claim 4 , wherein the ratio P 2 /P 1 , is larger than 10.
6. The bone screw according to claim 3 , wherein the external thread is a multiple thread.
7. The bone screw according to claim 3 , wherein the external thread is a double thread.
8. The bone screw according to claim 1 , wherein the circular coupling includes a tab extending radially therefrom to engage a respectively sized portion of the bone plate hole.
9. The bone screw according to claim 1 , wherein the circular coupling includes a driver engaging structure formed thereon.
10. The bone screw according to claim 1 , wherein the head and the shaft are coupled to each other in an axially fixed manner.
11. The bone screw according to claim 1 , wherein a coupling between the head and the shaft permits an axial relative movement between 0.5 mm. and 3.0 mm.
12. The bone screw according to claim 1 , wherein the head has a helical through bore configured to slidingly receive the shaft therein.
13. The bone screw according to claim 1 , wherein a cross-sectional shape of the shaft is one of circular, oval, triangular, rectangular and hexagonal.
14. The bone screw according to claim 1 , wherein the shaft has the form of a helically wound thin rod.
15. A bone screw, comprising:
a proximal head being configured to lockingly engage a bone plate hole; and
a substantially helical shaft extending distally from the head along a substantially helical path,
wherein the head and the shaft are rotatably coupled to each other so that the shaft can rotate about a central longitudinal axis thereof with respect to the head and wherein a distal portion of the shaft has a rigidity less than that of a proximal portion thereof to facilitate bending during insertion.
16. The bone screw according to claim 15 , wherein the shaft comprises a notch located in a distal portion.
17. A bone screw, comprising:
a proximal head being configured to lockingly engage a bone plate hole; and
a substantially helical shaft extending distally from head along a substantially helical path,
wherein the head and the shaft are rotatably coupled to each other so that the shaft can rotate about a central longitudinal axis thereof with respect to the head and wherein the head tapers conically towards the shaft at an angle between 2.8° and 20°.