14. A bone anchor for supporting one of an elongate member and a tensioned cord in a U-shaped channel, the bone anchor comprising: a receiver having a U-shaped channel adapted to receive one of an elongate member and a tensioned cord; a pressure insert positioned in the receiver and having upward extending arms, with each of the arms having upper contact surfaces; a sleeve positioned in the U-shaped channel above the pressure insert and having a circular bore extending therethrough to slidingly receive and surround the one of an elongated member and a tensioned cord; and a closure that is positioned in the receiver above the sleeve, wherein the sleeve includes a sleeve body constructed of a deformable polymer and a transfer structure constructed of a rigid metal, the transfer structure having depending legs with lower surfaces that align and mate with the upper contact surfaces on the pressure insert arms in an overlapping relationship for transferring force from the closure through the transfer structure to the pressure insert without transferring pressure directly through the deformable body of the sleeve to the insert.
15. The anchor according to claim 14 , wherein the transfer structure includes projections extending therefrom and into the sleeve body to resist torque of the transfer structure relative to the sleeve body.