Patent ID: 9615855
Date: 2017-04-11
CPC Classifications: A61B

Claim:
1. A positioning casing of a bone screw used to fit a screw body, comprising a securing base and an alignment casing, both of which are integrally configured and a screw body passage is formed therethrough, wherein: a through hole is formed at a bottom of the securing base and along the screw body passage with its diameter smaller than that of a spherical head of the screw body; a wall of the securing base has two openings opposite to each other and open to a top of the securing base such that a first passage passing through the securing base is formed between the openings and laterally passes through the securing base; the alignment casing has a wall portion and a volume reduced portion; an elongated opening is formed on the wall portion and communicates with one of the openings; said volume reduced portion is a portion with part of the wall portion removed and thus receding from an outer surface of the securing base and a guide opening formed in the volume reduced portion which communicates with another one of the openings; a first easy breaking portion is formed between the alignment casing and the securing base to facilitate the removal of the alignment casing from the securing base; a plurality of alignment openings are formed at the wall portion of the alignment casing at a distal end from the securing base; in the volume reduced portion, the entire wall is removed to form the guide opening, and the distal end of the alignment casing relative to the screw body passage has a receding area that gradually increases from an end adjacent to the securing base toward the distal end far from the securing base; and the wall portion includes two walls symmetrical about a longitudinal center axis of the screw body passage, and the receding area of the cross-section in the volume reduced portion at the distal end of the alignment casing is equal to or more than half of an area of the cross-section of the top of the securing base.