Patent ID: 8828060

Claim:
A bone anchor comprising: a shank portion; a holding portion configured to hold a rod; and a locking element to lock the rod in the holding portion; wherein the holding portion comprises a recess on one end having a U-shaped cross-section and two open legs for receiving the rod, and an inner thread on the open legs; wherein the locking element comprises an outer thread having two flanks, the outer thread cooperating with the inner thread, one of the two flanks of the outer thread facing the one end of the holding portion, the other of the two flanks of the outer thread facing away from the one end of the holding portion and each of the two flanks of the outer thread enclosing an angle of 90° with a central axis (M) of the holding portion when the locking element is tightened; and wherein the inner thread comprises two flanks, one of the two flanks of the inner thread facing the one end of the holding portion and the other of the two flanks of the inner thread facing away from the one end of the holding portion, each of the two flanks of the inner thread enclosing an angle of 90° with the central axis (M) of the holding portion; wherein the thread cross-sections of the inner thread and the outer thread, respectively, are substantially rectangular; wherein the inner thread of the open legs comprises a rounded root; and wherein a crest of the outer thread of the locking element is spaced from a root of the inner thread when the locking element is tightened.