| 摘要 |
A bone screw (10) is provided having a head (12) and a shank (14) with oppos ed first and second (16, 18) helical threads extending there around. In one embodiment, the shank (14) has a proximal portion (14p) with a constant mino r diameter (d1), and a distal portion (14d) with a minor diameter (d2) that decreases in a proximal-to-distal direction to form a taper. The opposed fir st and second helical threads (16, 18) preferably define a thread depth (dt) th at remains constant along the length of the shank (14). In an exemplary embodiment, a major diameter (D2) of the shank (14) at a distal tip of the shank (14) is equal to or less than the minor diameter (d1) of the proximal portion of the shank (14).
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