A bone screw is provided including a tubular body and a head as separate parts. The tubular body has a first end, a second end, a tubular wall defining a cavity and a plurality of openings extending through the tubular wall into the cavity. The tubular body also includes a continuous exterior bone thread on an exterior tubular surface of the tubular wall. The continuous exterior bone thread extends for at least one full revolution about the tubular surface. The head defines an inner bore and includes an engagement structure to engage with a driver to advance the bone screw in the bone when a rotating force from the driver is applied to the engagement structure in a first direction, and a connection structure to connect to the tubular body at the first end. The head is connected to the tubular body by the connection structure in such a way that the head is locked against disconnection from the tubular body when a rotating force from a driver is applied to the engagement structure in a second direction opposite to the first direction.
