Instruments for use with a bone anchor (2) and a bone anchor (2) are provided comprising a shaft (7) having a first end (8) and a second end (9), a channel (11, 12) extending from the first end (8) to the second end (9), and a plug member (30, 40, 41) which is insertable into the channel and guidable through the channel for closing the channel at the second end. The bone anchor is suitable for minimally invasive surgery in such a way a guide wire can be guided through the bone anchor and after the bone anchor has been anchored in the bone the plug member is inserted to close the open end of the bone anchor. A bone cement or a pharmaceutical substance can be introduced into the bone anchor. The instruments allow introduction of the plug member and injection of bone cement.
