Importance

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Abstract

A locking tool is described for connecting a bone screw with a rod having a predetermined diameter. The bone screw includes a screw member having a threaded portion and a head with spherical segment-shaped portion, and a cylindrical seat part for receiving the head and the rod. The seat part has two ends with a first bore at one end through which the threaded portion passes. An inner hollow spherical portion corresponding to the head is adjacent to the first bore. A second bore opens toward the opposite end for inserting the threaded portion and the head. A substantially U-shaped portion is provided with two free leg members for receiving the rod, the leg members having an internal screw thread. The locking tool has a handle part with a casing having two ends. An external screw thread on the first end engages the internal screw thread of the bone screw leg members. A pressure piece acts upon the head when screwing the external screw thread into the bone screw. A bolt for supporting the pressure piece on the first end provides rotation relative to the first end about a central axis of the handle part. The pressure piece has at least one projection for acting upon the head. The projection is spaced from the central axis by a distance which is at least equal to half of the predetermined diameter of the rod.

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First Claim