A bone anchor is driven into the pedicle portion of the vertebral body until a shoulder protrusion within the proximal aspect of the anchor abuts the bone surface and prevents further anchor travel into the bone. A feature within the distal aspect of the anchor is actuated producing the emergence of a distal shoulder protrusion. The latter directly abuts the distal aspect of the pedicle at the pedicle/vertebral body interface. Using this method, the anchor captures the pedicle portion of bone and contains it between the proximal and distal shoulder abutments.