Uniplanar bone anchor system

1. A uniplanar bone anchor system for a fixation procedure comprising:

a bone fastener having a head and a shaft adapted to engage an anatomy, the head defining at least one bearing surface and further having a first planar head surface opposite a second planar head surface;

a saddle extending along a longitudinal axis and having a proximal end and a distal end, the distal end including a central bore formed about the longitudinal axis that receives the head of the bone fastener,

a cap located in the central bore of the saddle, the cap having a first planar cap surface, a second planar cap surface, and at least one triangular shaped protrusion;

wherein the bone fastener is received within the central bore such that the engagement between the first planar head surface and the first planar cap surface and engagement between the second planar head surface, and the second planar cap surface enables the bone fastener to articulate relative to the saddle in a single plane.

2. The system of claim 1 , wherein the bone fastener is a pedicle screw.

3. The system of claim 1 , wherein the saddle includes a plurality of sidewalls for articulating relative to the at least one bearing surface of the bone fastener, each sidewall of the plurality of sidewalls includes a planar portion proximate the cap and an arcuate portion proximate the at least one bearing surface of the head.

4. The system of claim 3 , wherein each sidewall of the plurality of sidewalls defines a slot, the system further comprising a ring received in each slot.

5. The system of claim 1 , wherein an upper side of the cap defines a receiver surface for receiving a portion of a cylindrical rod.

6. The system of claim 1 , wherein the cap defines a slot comprising the at least one triangular protrusion and a second triangular protrusion for receiving a protrusion on the fastener.

7. The system of claim 6 , wherein the protrusion on the fastener is arcuate in shape.

8. The system of claim 1 , wherein the head of the fastener defines a slot for receiving the at least one protrusion in the cap.

9. The system of claim 8 , wherein the slot is defined between the first and second planar head surfaces.

10. The system of claim 9 , wherein the slot is defined between the first and second planar cap surfaces.

11. The system of claim 1 , wherein the head of the fastener defines a protrusion and the cap defines a slot for receiving the protrusion.

12. The system of claim 1 , further comprising a support surrounding a circumference of the head and supporting the remainder of the head in the saddle.

13. A uniplanar bone anchor system for a fixation procedure comprising:

a bone fastener having a head and a shaft adapted to engage an anatomy, the head defining at least one bearing surface and further having a first planar head surface opposite a second planar head surface, a slot defined between the first and second planar head surfaces;

a saddle extending along a longitudinal axis and having a proximal end and a distal end, the distal end including a central bore formed about the longitudinal axis that receives the head of the bone fastener;

a cap located in the central bore of the saddle, the cap having a first planar cap surface, a second planar cap surface and a triangular shaped protrusion defined between the first planar cap surface and the second planar cap surface, the triangular shaped protrusion received by the slot;

wherein the bone fastener is received within the central bore such that the engagement between the first planar head surface and the first planar cap surface and engagement between the second planar head surface, and the second planar cap surface enables the bone fastener to articulate relative to the saddle in a single plane.

14. The system of claim 13 , wherein the bone fastener is a pedicle screw.

15. The system of claim 13 , wherein the saddle includes a plurality of sidewalls for articulating relative to the at least one bearing surface of the bone fastener, each sidewall of the plurality of sidewalls includes a planar portion proximate the cap and an arcuate portion proximate the at least one bearing surface of the head.

16. The system of claim 15 , wherein each sidewall of the plurality of sidewalls defines a slot, the system further comprising a ring received in each slot.

17. The system of claim 13 , further comprising a support surrounding a circumference of the head and supporting the remainder of the head in the saddle.

18. A uniplanar bone anchor system for a fixation procedure comprising:

a bone fastener having a head and a shaft adapted to engage an anatomy, the head defining at least one bearing surface and further having a first planar head surface opposite a second planar head surface, a slot defined between the first and second planar head surfaces;

a saddle extending along a longitudinal axis and having a proximal end and a distal end, the distal end including a central bore formed about the longitudinal axis that receives the head of the bone fastener;

a cap located in a rectangular portion of the central bore of the saddle, the cap having a first planar cap surface, a second planar cap surface and a protrusion defined between the first planar cap surface and the second planar cap surface, the protrusion received by the slot;

wherein the bone fastener is received within the central bore such that the engagement between the first planar head surface and the first planar cap surface and engagement between the second planar head surface, and the second planar cap surface enables the bone fastener to articulate relative to the saddle in a single plane.

19. The system of claim 18 , wherein the bone fastener is a pedicle screw.