Polyaxial bone anchor with pop-on shank, shank, friction fit retainer, winged insert and low profile edge lock
A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in an integral receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A down-loadable compression insert, a down-loadable friction fit split retaining ring having inner and outer tangs and an up-loadable shank upper portion cooperate to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra. The shank and receiver once assembled cannot be disassembled.
1. In a polyaxial pedicle screw including a shank having a body for fixation to a bone and an integral upper portion, an U-shaped receiver having a top portion and an integral base, the receiver top portion defining an open rod-receiving channel, the base defining a cavity communicating with a bottom opening, the upper portion of the shank positionable within the cavity, and the channel communicating with the cavity, the improvement comprising:
a) a retainer positioned within the cavity prior to the shank being loaded and capturing the shank upper portion once loaded, the retainer being in a non-pivotal relationship with respect to the receiver; and wherein
b) the retainer further includes a cut-out surface being sized and shaped to provide for increased polyaxial motion in at least one direction for the shank with respect to the receiver.