Dynamic stabilization member

Abstract

A dynamic fixation medical implant having at least two bone anchors includes a longitudinal connecting member assembly having at least one transition portion and cooperating outer sleeve, both the transition portion and sleeve being disposed between the two bone anchors. The transition portion includes a rigid length or rod having apertures therein and a molded plastic length that extends through the apertures, thus attaching the plastic length to the rigid length. The sleeve surrounds the transition portion and extends between the pair of bone anchors, the sleeve being compressible in a longitudinal direction between the bone anchors.

1 . A medical implant assembly comprising:
 a first pivotal bone anchor and a second pivotal bone anchor, each of the first and second pivotal bone anchors having a receiver, a shank, a retainer to hold the shank in the receiver, and an insert above the retainer, the retainer having a top, a bottom, and an outer surface with a decreasing diameter extending from the top toward the bottom of the retainer;   a first segment configured to attach to at least one of the first and second pivotal bone anchors;   a second segment configured to be affixed to the first segment within a transition segment, the second segment being elongate and configured to be stretched during use; and   the transition segment being at least partially disposed between the first pivotal bone anchor and the second pivotal bone anchor, the transition segment having a central bore opening at an outer end of the transition segment of the first segment, the second segment at least partially positioned within the central bore.