18. The improvement of claim 1 wherein a) the receiver engaging portions of the insert opposed arms are outwardly extending flange portions.
1. In a medical implant assembly having at least one polyaxial bone screw attached to a longitudinal connecting member, the bone screw having a receiver with a channel, the improvement wherein: a) at least a portion of the longitudinal connecting member is sized and shaped to be received in the receiver channel; and further comprising: b) a compression insert directly engaging both the longitudinal connecting member and a shank of the polyaxial bone screw, the insert having a base, a pair of opposed arms with outer receiver engaging portions, and the opposed arms defining a through channel with a lower connecting member seating surface; wherein c) the compression insert is top-loadable in the receiver in a first orientation, wherein, when in the first orientation, the compression insert through channel is substantially perpendicular to the receiver channel, and then rotated to a second orientation, such that the compression insert through channel is substantially parallel to the receiver channel and cooperating receiver portions snap into the receiver engaging portions.