Abstract: A pedicle-screw assembly has a screw extending along an axis and having a threaded shaft and a round head, an inner cap part carried on the head and swivelable on the head, and an outer cap part forming with the inner cap part a seat adapted to hold an end of a distraction/stabilizing rod. The outer cap part has formations engageable in a snap fit over the inner cap part, and an element on the outer cap part can be tightened to fix the rod in the seat. The outer cap part is generally U-shaped and formed with a base forming the seat and a pair of legs projecting parallel to the axis, flanking the cap inner part, and having ends engaged in a snap fit around sides of the cap inner part.

Abstract: A pedicle-screw assembly has a screw extending along an axis and having a threaded shaft and a round head, an inner cap part carried on the head and swivelable on the head, and an outer cap part forming with the inner cap part a seat adapted to hold an end of a distraction/stabilizing rod. The outer cap part has formations engageable in a snap fit over the inner cap part, and an element on the outer cap part can be tightened to fix the rod in the seat. The screw head has an inner region with a part-spherical outer surface and an end face lying on a plane substantially perpendicular to the screw axis. The head is formed on the end face with a central part-spherical bump centered on the axis. In addition the outer cap part is generally U-shaped and formed with a base forming the seat and carrying the fixing means and a pair of legs projecting parallel to the axis, flanking the cap inner part, and having ends engaged around sides of the cap inner part.