Spinal Fixation System
The present disclosure is directed to a polyaxial pedicle screw including a housing, an anvil, a bone screw member, and a compression ring or cap. The housing includes opposing arms, a collar at a bottom portion of the housing, a cutout, and a passage. The anvil is positioned in the passage. The bone screw member includes a head and a threaded shaft extending from the head along a shaft axis, wherein the head is configured to be positioned in the passage. The anvil includes a spring element positioned within an inner surface of the anvil, wherein the anvil is configured to be positioned in the passage adjacent the head, and the spring element is configured to apply a force to the head.
1 . A polyaxial pedicle screw comprising: a housing including opposing arms and a passage extending through the housing; a bone screw member including a head and a threaded shaft extending from the head, wherein the head is configured to be positioned at least partially within the passage; and an anvil including a spring element positioned within an inner surface of the anvil, wherein the anvil is configured to be positioned in the passage adjacent the head, and the spring element is configured to apply a force to the head.
2 . The polyaxial pedicle screw of claim 1 , wherein the spring element is positioned along a circumference of the inner surface of anvil.
3 . The polyaxial pedicle screw of claim 1 , wherein the spring element includes a plurality of spring elements radially positioned within the inner surface of the anvil.
4 . The polyaxial pedicle screw of claim 3 , wherein the plurality of spring elements includes a first, second, third and fourth spring element radially positioned within the inner surface of the anvil.
5 . The polyaxial pedicle screw of claim 4 , wherein the first, second, third, and fourth spring element are each radially positioned 90 degrees within the inner surface of the anvil.
6 . The polyaxial pedicle screw of claim 1 , wherein the spring element is a bilateral cantilevered spring.
7 . The polyaxial pedicle screw of claim 1 , wherein the spring element is configured to flex upward in a direction opposite the head.
8 . The polyaxial pedicle screw of claim 1 , wherein the force is a constant downward force.
9 . The polyaxial pedicle screw of claim 1 , wherein the force is further configured to restrict movement of the bone screw member within the housing.
10 . The polyaxial pedicle screw of claim 1 , wherein the anvil further includes a protrubeance on an outer surface of the anvil, the protuberance configured to be positioned within a slot formed in the housing adjacent to the passage.
11 . The polyaxial pedicle screw of claim 1 , wherein the head includes a surface texture configured to engage the anvil.
12 . The polyaxial pedicle screw of claim 1 , further comprising a collar at a bottom portion of the housing, and a cap positioned over the collar.
13 . A polyaxial pedicle screw comprising: a housing including opposing arms and a passage extending through the housing; a bone screw member including a head and a threaded shaft extending from the head along a shaft axis, wherein the head is configured to be positioned at least partially within the passage; and an anvil including a spring element extending from an inner surface of the anvil, wherein the anvil is configured to be positioned in the passage adjacent the head, and the spring element is configured to restrict movement of the bone screw member within the housing.
14 . The polyaxial pedicle screw of claim 13 , wherein the spring element engages the head of the bone screw member and the spring element restricts movement of the head within the passage.
15 . The polyaxial pedicle screw of claim 14 , the spring element restricts polyaxial movement of the shaft relative to the housing.
16 . The polyaxial pedicle screw of claim 13 , wherein the spring element is a bilateral cantilevered spring.
17 . A polyaxial pedicle screw comprising: a housing including opposing arms, a collar at a bottom portion of the housing, and a passage extending through the housing; a bone screw member including a head and a threaded shaft extending from the head, wherein the head is configured to be positioned at least partially within the passage; an anvil including a spring element positioned within an inner surface of the anvil, the spring element configured to engage the head; and a cap positioned over the collar, wherein the cap is configured to at least partially retain the head within the housing.
18 . The polyaxial pedicle screw of claim 17 , wherein the spring element is configured to frictionally engage the head to provide a constant force.
19 . The polyaxial pedicle screw of claim 17 , wherein the spring element is configured to restrict moment of the bone screw member within the housing.
20 . The polyaxial pedicle screw of claim 17 , wherein the spring element is a bilateral cantilevered spring.