Polyaxial bone screw with shank articulation pressure insert and method
OwnerRoger P. Jacksoninventor
Life of this patent
Estimating the term…
Abstract
A polyaxial bone screw assembly includes a threaded shank body having an upper portion, a receiver member or head, a retaining and articulating structure, and a pressure insert disposed between the shank upper portion and a rod. The receiver has a U-shaped cradle defining a channel for receiving a spinal fixation rod and a receiver cavity. The retaining and articulating structure attaches to the shank and rotates with the shank in the cavity during positioning. The pressure insert presses upon the shank upper portion and not the retaining and articulating structure.
Claims20
A bone anchor assembly for securing an elongate rod to a bone, the bone anchor assembly comprising:
- a shank having a proximal capture portion and an anchor portion extending distally from the proximal capture portion for fixation to the bone;
- a receiver having a longitudinal axis, an upper portion defining a U-shaped channel with inner sidewall surfaces configured to receive the elongate rod, and a lower portion defining a cavity communicating with the U-shaped channel and a receiver bottom opening for receiving the proximal capture portion of the shank therethrough, the inner sidewall surfaces including a guide and advancement structure and a discontinuous downward-facing shoulder formed therein between the guide and advancement structure and the cavity;
- a retainer sized and shaped for loading into the cavity to engage and hold the shank proximal capture portion in spaced relation with respect to the receiver while an outer surface of the retainer engages an interior surface of the cavity to allow a pivotal motion between the receiver and the shank;
- and
- a pressure insert sized and shaped to be positioned downwardly within the receiver into a first position, the pressure insert having upward-facing contact surfaces and being rotatable with a tool into a second position that locates the upward-facing contact surfaces under the discontinuous downward-facing shoulder of the receiver to prevent the pressure insert from moving back up within the receiver.
A bone anchor assembly for securing an elongate rod to a bone, the bone anchor assembly comprising:
- a shank having a proximal capture portion with a top surface and an anchor portion extending distally from the proximal capture portion for fixation to the bone;
- a receiver having a longitudinal axis, an upper portion defining a U-shaped channel with inner sidewall surfaces configured to receive the elongate rod, and a lower portion defining a cavity communicating with the U-shaped channel and a receiver bottom opening with the shank anchor portion extending therethrough, the inner sidewall surfaces including a guide and advancement structure formed therein, the receiver having an internal downward-facing surface located between the guide and advancement structure and the receiver bottom opening;
- a retainer sized and shaped for loading into the cavity to engage and hold the shank proximal capture portion within the receiver while an outer surface of the retainer engages an interior surface of the cavity to allow for pivoting motion between the receiver and the shank to provide for a pivotal orientation therebetween;
- and
- a pressure insert sized and shaped to be disposed downwardly into a first position within the receiver adjacent the downward-facing surface, with the shank proximal capture portion top surface frictionally engaging the pressure insert for directly receiving downward pressure from the pressure insert, the pressure insert having an upward-facing surface configured to engage the receiver downward-facing surface,
- wherein the pressure insert is rotatable with a tool about the longitudinal axis into a second position within the receiver, with the upward-facing surface entering into frictional engagement with the downward-facing surface, so as to apply downward pressure to the shank proximal capture portion top surface to frictionally secure the pivotal orientation of the shank with respect to the receiver prior to the elongate rod being received within the receiver.
Dependencies are inferred from the claim text.