Compression screw for a joint endoprosthesis
First Claim
1. A compression bone screw apparatus comprising:
- a) an elongated cylindrical internal shaft member that includes a first smaller diameter portion and an enlarged diameter annular proximate end portion;
b) the internal shaft member having a smooth internal bore extending longitudinally along the length of the internal shaft member;
c) a generally cylindrical external lag screw member with an internal lag screw bore for receiving the internal shaft member, and that is slidably mounted in telescoping fashion upon the shaft member, and the lag screw member being extendable to a position spaced from the enlarged diameter annular proximate end portion thereof;
d) external thread means on the lag screw member defining its maximum diameter for engaging a surgically formed opening in bone tissue;
e) the lag screw bore being elongated so that the internal shaft member can extend into the lag screw bore along substantially the entire length of the lag screw member; and
f) compression loading means for placing the assembly of the lag screw member and internal shaft member in compression when the lag screw member and internal shaft member are fully extended with respect to each other to a maximum overall length.
1 Assignment
0 Petitions
Accused Products
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.
219 Citations
8 Claims
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1. A compression bone screw apparatus comprising:
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a) an elongated cylindrical internal shaft member that includes a first smaller diameter portion and an enlarged diameter annular proximate end portion; b) the internal shaft member having a smooth internal bore extending longitudinally along the length of the internal shaft member; c) a generally cylindrical external lag screw member with an internal lag screw bore for receiving the internal shaft member, and that is slidably mounted in telescoping fashion upon the shaft member, and the lag screw member being extendable to a position spaced from the enlarged diameter annular proximate end portion thereof; d) external thread means on the lag screw member defining its maximum diameter for engaging a surgically formed opening in bone tissue; e) the lag screw bore being elongated so that the internal shaft member can extend into the lag screw bore along substantially the entire length of the lag screw member; and f) compression loading means for placing the assembly of the lag screw member and internal shaft member in compression when the lag screw member and internal shaft member are fully extended with respect to each other to a maximum overall length. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification