Bone anchor

A method of attaching a bone anchor to a bone, the bone anchor comprising an anchor member comprising a first material, the anchor member having a first end, a second end, a tubular section extending along a longitudinal axis between the first end and the second end and having an expandable region configured to expand radially outwards from the longitudinal axis by reducing a distance between the first end and the second end, and a bone engagement structure projecting from at least a portion of the expandable region of the tubular section for facilitating insertion of the anchor member into the bone, and a core member having a first end and a second end, and comprising a second material that exhibits less flexibility than the first material, wherein a portion of the core member is configured to be inserted into the first end of the anchor member and advanced past the expandable region for connecting the second end of the core member to the second end of the anchor member, the method comprising:

• inserting the anchor member into the bone;
• inserting the core member into the first end of the anchor member and advancing the core member past the expandable region to a first position where the second end of the core member and the second end of the anchor member are connected to one another, and where the expandable region of the tubular section has a first maximum diameter while a first end and a second end of the expandable region are separated by a first distance;
• and
• actuating the core member relative to the anchor member to move the core member to a second position in the anchor member while the second end of the core member and the second end of the anchor member remain connected to one another, and where the expandable region of the tubular section has a maximum diameter greater than the first maximum diameter while the first end and the second end of the expandable region are separated by a distance shorter than the first distance.

A bone anchor comprising:

• an anchor member comprising a first material, the anchor member having a first end having an opening, a second end having a connection portion, a tubular section extending along a longitudinal axis between the first end and the second end and having an expandable region positioned axially between the opening and the connection portion, the expandable region configured to expand radially outwards from the longitudinal axis by reducing a distance between the first end and the second end, and a bone engagement structure projecting from at least a portion of the expandable region of the tubular section for facilitating insertion of the anchor member into a bone;
• and
• a monolithic core member having a first end and a second end, and comprising a second material that exhibits less flexibility than the first material, wherein the core member is insertable into the opening at the first end of the anchor member, and wherein the core member is connectable to the connection portion at the second end of the anchor member;
• wherein the core member is configured to cooperate with the anchor member, such that when the core member is in the anchor member and the second end of the core member and the connection portion of the anchor member remain connected to one another, the core member is configured to be actuated relative to the anchor member to adjust the tubular section from a first position where the expandable region of the tubular section has a first maximum diameter while a first end and a second end of the expandable region are separated by a first distance, to a second position where the expandable region of the tubular section has a maximum diameter greater than the first maximum diameter while the first end and the second end of the expandable region are separated by a distance shorter than the first distance.