| 摘要 |
An improved set screw, for use in an osteosynthesis apparatus to secure and fix a spinal rod in the bore of the head of a bone screw, hook, connector or the like from translational or rotational motion, which comprises a head of hexagonal external cross-section and a lower portion having a threaded outer surface. The lower threaded portion includes a feature which facilitates subsequent removal of the lower threaded portion from the threaded bore in which it is secured. In a first embodiment, the feature facilitating removal, comprises a bore which extends completely through the screw, from top to bottom. The bore may be cylindrical and adapted to receive an easy out tool for removal of the lower threaded portion, or of a geometry which corresponds to the shape of an allen type wrench which may be inserted in the section of the bore extending into the lower threaded portion of the screw for use in removal of the lower threaded portion. In another embodiment, a flange is formed on the lower threaded portion of the screw at an upper end thereof, adjacent the peripheral notch. The flange is preferably hexagonal or otherwise shaped for cooperative engagement by a wrench or the like, for gripping the lower portion for removing it from a threaded bore.
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