Importance

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Abstract

A compression bone screw apparatus includes an elongated cylindrical shaft member with a first smaller diameter portion that is of generally uniform cylindrical configuration, and a second enlarged diameter annular proximate end portion. An internal bore extends longitudinally along the length of the shaft member, being open ended so that a driver tool can extend through the elongated cylindrical shaft member during installation of the compression bone screw apparatus. A generally cylindrical lag screw member is slidably mounted in telescoping fashion upon the shaft member and at a position spaced from the annular proximate end portion thereof. Splines prevent rotation of the shaft with respect to the lag as the lag slides upon the shaft to increase the overall combined length of the assembled shaft and lag screw. Stops, preferably in the form of abutting shoulders of the respective shaft and lag screw members abut when the apparatus is fully extended so that continued threading of the lag into a surgical opening in bone causes a compression load across a fracture. The small compression load discourages disassembly of the apparatus when subsidence occurs.

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First Claim