Importance

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Abstract

A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in a receiver and retained within the receiver by a retaining structure in the form of an open ring. The retaining structure is compressible, having an opening with two ends that may be pressed toward one another. The receiver has a U-shaped cradle defining a channel for receiving a spinal fixation rod. The receiver channel communicates with a cavity partially defined by an upper spherical surface and a substantially cylindrical surface communicating with a bottom opening of the receiver that allows for bottom loading the shank upper portion and the compressed retaining structure into the receiver, but prevents passage of the retaining structure out of the receiver once the retaining structure expands to an original form thereof and thus retains the shank upper portion within the cavity. In some embodiments, the shank upper portion is designed to directly frictionally engage the spinal fixation rod when a closure structure operably urges the rod toward the upper portion, fixing the bone screw shank body in a selected angular orientation with respect to the receiver.

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First Claim