Uniplanar screw assembly and methods of use
View Patent ↗The screw assembly includes a screw, an insert, and a body member. The screw includes a longitudinal axis and a proximal end with a head portion and a distal end with a threaded portion. The insert operably couples with the head portion and is configured to rotate relative to the head portion about the longitudinal axis. The body member operably couples with the insert and is configured to pivot relative to the insert in a single plane parallel to the longitudinal axis. In other features, the body member operably couples with the insert and is configured to pivot relative to the insert about a transverse axis normal to a plane parallel to the longitudinal axis.
1. A screw assembly configured to receive a fixation rod, the screw assembly comprising:
a screw with a longitudinal axis including a proximal end with a head portion and a distal end with a threaded portion;
an insert operably coupled with the head portion and configured to rotate relative to the head portion about the longitudinal axis, the insert having a pair of extensions projecting radially away from the longitudinal axis; and
a body member operably coupled with the insert, the insert being rotatably disposed within the body member, the body member having a threaded portion disposed on an interior side wall of the body member, and a pair of opposed recesses disposed beneath the threaded portion, each of the opposed recesses is configured to receive a respective extension of the pair of extensions, the pair of extensions working in concert with the pair of opposed recesses so as to only pivot the body member relative to the insert along an axis orthogonal to both the longitudinal axis and an axis defined by a line transverse to the pair of extensions.
2. The screw assembly of claim 1 , wherein the insert further comprises at least a partially curved interior surface configured to engage a curved lateral surface of the head portion.
3. The screw assembly of claim 1 , wherein the insert permits 360 degree rotation of the body member relative to the head portion about the longitudinal axis.
4. The screw assembly of claim 1 , wherein the extensions are diametrically opposed to each other.
5. The screw assembly of claim 1 , wherein the each of the extensions include proximal surfaces that angle away from a plane that is normal to the longitudinal axis by a predetermined angle and are configured to limit pivoting of the body member to a predetermined pivot angle.
6. The screw assembly of claim 1 , wherein each of the extensions include distal surfaces that are curved and configured to permit pivoting of the body member.
7. The screw assembly of claim 1 , further comprising a bushing disposed between the body member and the head portion.
8. A screw assembly configured to receive a fixation rod, the screw assembly comprising:
a screw with a longitudinal axis including a proximal end with a head portion having a curved circumferential surface and a distal end with a threaded portion;
an insert including
at least a partially curved interior surface that engages the curved circumferential surface to rotate relative to the head portion about the longitudinal axis, the insert having a pair of extensions projecting radially away from the longitudinal axis; and
a body member, the insert being rotatably disposed within the body member, the body member having a threaded portion disposed on an interior side wall of the body member, and a pair of opposed recesses disposed beneath the threaded portion, the pair of opposed recesses configured to receive the pair of extension, the pair of extensions working in concert with the pair of opposed recesses so as to only pivot the body member relative to the insert along an axis orthogonal to both the longitudinal axis and an axis defined by a line transverse to the pair of extensions.
9. The screw assembly of claim 8 , wherein each of the extensions are diametrically opposed to each other and projecting radially away from the longitudinal axis and into the pair of opposed recesses of the body member.
10. The screw assembly of claim 8 , wherein the head portion includes a cap having a diameter greater than a diameter of a proximal opening of the insert to prevent passage of the head portion distally through the insert and body member.
11. The screw assembly of claim 8 , wherein the extensions include proximal surfaces that angle away from a plane that is normal to the longitudinal axis by a predetermined angle and are configured to limit pivoting of the body member to a predetermined pivot angle; and
a distal surface that is curved and configured to permit pivoting of the body member.