Stabilizing Bone Using Spinal Fixation Devices and Systems
In one embodiment, the present invention includes a bone fixation assembly comprising a coupling element and a bone anchor. The coupling element has an upper surface with a first diameter defining a first bore extending along a first axis, a lower surface with a second diameter defining a second bore extending along a second axis, and an internal surface area defining a seating portion adjacent to the lower surface. The bone anchor has an insertion end opposite of a head. The head may be curved for receipt within the seating portion. The first diameter of the first bore is greater than the second diameter of the second bore. Likewise, the first and second axes may intersect such that the first and second bores are in communication with one another. Related elements and systems of this assembly are also disclosed.
1 . (canceled)
2 . A bone fixation assembly, comprising:
a coupling element having an upper end, a lower end and an inner surface defining first and second bores, the first bore being coaxial with a first axis and the second bore being coaxial with a second axis different than the first axis; and
a monolithic anchoring element having a head and a shaft, a portion of the head being disposed within the second bore of the coupling element and a portion of the shaft projecting from the lower end of the coupling element.
3 . The assembly of claim 2 , wherein the inner surface forms a seat for the head of the anchoring element.
4 . The assembly of claim 3 , wherein the seat is substantially conical, tapers toward the second axis and prevents the head of the anchoring element from passing through the lower end of the coupling element.
5 . The assembly of claim 2 , wherein the first bore extends from the upper end toward the lower end and the second bore extends from the lower end toward the upper end.
6 . The assembly of claim 2 , wherein the first and second bores are in communication with one another between the upper and lower ends of the coupling element.
7 . The assembly of claim 2 , wherein the head of the anchoring element has a substantially spherical surface.
8 . The assembly of claim 7 , wherein the anchoring element includes a neck at the junction of the head and the shaft, the neck having a diameter less than a greatest diameter of the shaft for facilitating pivotal movement of the anchoring element relative to the coupling element.
9 . The assembly of claim 2 , further comprising a locking element engagable with the coupling element for locking an angular position of the anchoring element relative to the coupling element.
10 . The assembly of claim 2 , wherein the inner surface is chamfered and facilitates insertion of the anchoring element through the first bore and into the second bore.
11 . The assembly of claim 2 , wherein the coupling element further defines a U-shaped channel.
12 . The assembly of claim 2 , further comprising a stabilizing rod positioned within the U-shaped channel.
13 . The assembly of claim 12 , further comprising a locking element engagable with the coupling element to secure the stabilizing rod within the coupling element.
14 . The assembly of 13 , wherein the locking element is a set screw and is threadably engaged to threading on the inner surface of the coupling element.
15 . A bone fixation assembly, comprising:
a coupling element having an upper end, a lower end and an inner surface defining a first bore and a second bore, the first bore extending along a first axis and the second bore extending along a second axis, the first and second axes forming an angle of greater than 0 degrees and less than 90 degrees with respect to each other; and
an anchoring element having a head and a shaft, a portion of the head being disposed within the second bore of the coupling element and a portion of the shaft projecting from the lower end of the coupling element.
16 . The assembly of claim 15 , wherein the angle between the first and second axes is between approximately 20 degrees and approximately 30 degrees.
17 . The assembly of claim 15 , wherein the angle between the first and second axes is between approximately 23 degrees and approximately 27 degrees.
18 . The assembly of claim 15 , wherein the angle between the first and second axes is approximately 24 degrees.
19 . The assembly of claim 15 , wherein the inner surface of the second bore defines a conically shaped seat adapted to prevent the head of the anchoring element from passing through the lower end of the coupling element.
20 . The assembly of claim 19 , wherein a portion of the head of the anchoring element is substantially spherical in shape and adapted to engage the conical seat of the coupling element to allow the anchoring element to rotate about the second longitudinal axis.
21 . The assembly of claim 15 , wherein the head of the screw has a depression adapted to receive a driver for driving the shaft of the anchoring element into bone.