Bone anchors, especially bone screws

Abstract

The invention relates to a bone anchor (2) with an instrument shaft (20), wherein the bone anchor (2) comprises a forked head (6) for receiving a correction rod. The instrument shaft (20) is detachably fixed to the forked head (6), and a coupling part (40) can be slid onto the instrument shaft (20) and is slidable within the access opening (10). The coupling part (40) has a longitudinally extending through-opening (42) for sliding onto the instrument shaft (20), which deviates from an internally cylindrical shape and is bounded by differently shaped areas (64, 66, 68) on a wall (70) of the coupling part (40) that defines the through-opening (42). In the transition between differently shaped areas (64, 66, 68) clamping edges (72) are formed on the wall (70) of the coupling part (40).The through-opening (42) is designed to have play relative to an outer circumference (74) of the instrument shaft (20) in such a way that the instrument shaft (20) is rotatable in the through-opening (42) and the coupling part (40) is tiltable relative to the instrument shaft (20) in the longitudinal direction (30), so that a clamping contact is formed between the clamping edges (72) at the wall (70) of the coupling part (40) and the instrument shaft (20) and the coupling part (40) is thereby prevented from further displacement relative to the instrument shaft (20).