Patent ID: 8771320

Claim:
A locking assembly for securing a rod in a rod receiving channel of a polyaxial bone anchoring device for use in spinal or trauma surgery, the locking assembly comprising: a first locking element having a first end, a second end, and a longitudinal axis, an outer surface with an external advancement structure, an inner wall defining a coaxial bore extending through the first locking element along the longitudinal axis, an internal advancement structure on a portion of the inner wall, and an engagement portion for a tool for advancing the first locking element; and a second locking element configured to be arranged at least partially in the first locking element, the second locking element having a first end configured to be oriented towards the first end of the first locking element, and an opposite second end, an outer surface with an external advancement structure configured to cooperate with the internal advancement structure of the first locking element, and a portion at the second end having a width greater than a greatest width of the external advancement structure of the second locking element to prevent the second locking element from rotating when the locking assembly is inserted into a bone anchoring device; wherein, when the second locking element is in the first locking element and the first locking element is advanced axially in a bone anchoring device at a first speed, the second locking element is configured to move axially relative to the bone anchoring device at a speed different than the first speed.