Offset multiaxial or polyaxial screw, system and assembly
A capless multiaxial screw fixation assembly, including a screw having a threaded portion and a screw head portion positioned at one end thereof and a retainer having a first end, a second end opposite the first end, and a bore for receiving the screw threaded portion so that the screw head portion is seated therein. At least one of the screw and the retainer is configured such that the retainer is able to pivot about the screw head portion in a non-symmetrical manner.
1. A multiaxial screw fixation system, comprising:
(a) a screw having a threaded portion and a screw head portion positioned at one end thereof; and
(b) a retainer having a first end, a second end opposite said first end, and a bore for receiving said threaded portion so that said screw head portion may be seated therein, said retainer further comprising a retainer rod-receiving channel and having a retainer centerline axis;
wherein said threaded portion comprises a screw centerline axis, said screw centerline axis being offset from said retainer centerline axis when said screw centerline axis and said retainer centerline axis are parallel;
wherein said retainer can pivot about said screw head portion a greater degree in a first direction compared to a second direction so that a maximum amount of pivoting in said first direction is greater than in said second direction.
2. The multiaxial screw fixation system of claim 1 , wherein a tool has an offset for driving said screw.
3. The multiaxial screw fixation system of claim 2 , wherein said screw head has a partial opening formed therein for receiving a tool.
4. The multiaxial screw fixation system of claim 3 , wherein said partial opening is a hex opening.
5. The multiaxial screw fixation system of claim 3 wherein a centerpoint of said partial opening is offset from a second centerline axis of said threaded portion.
6. The multiaxial screw fixation system of claim 1 , wherein a centerpoint of a partial opening is aligned with a first centerline axis of said screw head portion.
7. The multiaxial screw fixation system of claim 1 , wherein said screw head has a partial shape formed therein for receiving a tool.
8. The multiaxial screw fixation system of claim 7 wherein said partial shape is a Y-shape.
9. The multiaxial screw fixation system of claim 7 wherein a centerpoint of said partial shape is offset from a centerline axis of said threaded portion.
10. The multiaxial screw fixation system of claim 7 , wherein a centerpoint of said partial shape is aligned with a centerline axis of said screw head portion.
11. The multiaxial screw fixation system of claim 1 , wherein said screw head portion comprises at least one of a partial opening or partial shape that interfaces or connects with a tool, wherein said at least one of said partial opening or said partial shape is offset from an axis of said threaded portion.