1. In a medical implant assembly having first and second bone attachment structures cooperating with a longitudinal connecting member having a tensioned cord and a spacer, the spacer located between the first and second bone attachment structures, the tensioned cord extending through the spacer, the first bone attachment structure having a first pair of opposed upstanding arms, the improvement wherein: a) the first bone attachment structure being a pivotal bone anchor and having: i) a shank pivotable with respect to a receiver; and ii) a compression insert within the receiver engaging the shank, the compression insert having a second pair of opposed upstanding arms forming a channel, each second pair of opposed upstanding arms of the compression insert having top surfaces; b) a sleeve for attachment to the pivotal bone anchor, the sleeve having: i) a first through bore sized and shaped for slidably receiving the tensioned cord, and ii) first and second body portions, the first body portion sized and shaped for being closely received within the insert and the second body portion being sized and shaped to be received between the first pair of opposed upstanding arms of the pivotal bone anchor, the second body portion also engaging the top surfaces of the second pair of upstanding arms of the compression insert.
8. The improvement of claim 1 , wherein a portion of the spacer overlaps an upper portion of the sleeve.