Patent ID: 8388660

Claim:
An orthopedic bone anchor assembly, comprising: an elongated outer shank member having external threads, an internal bore aligned along a long axis of the outer shank member, and at least one slot on a distal region of the outer shank member that permits radial expansion of the distal region of the outer shank member; an elongated inner shank member having a threaded distal segment and a proximal segment joined at an intersection, wherein the diameter of the distal segment is greater than the diameter of the proximal segment, and wherein, when the inner shank member is coupled to the outer shank member, at least a portion of the proximal segment is contained within the internal bore of the outer shank member, wherein at least a portion of the distal segment is threaded and positioned distally outside of the internal bore of the outer shank member; and a proximal head member having a threaded bore that engage a threaded proximal portion of the inner shank member, the head member further having a distal abutment surface that abuts a proximal portion of the outer shank member, wherein the head member is at least partially seated within a housing member, wherein the housing member is adapted to receive an interconnecting rod member, wherein the housing member is movable relative to the threaded shank member in at least one plane, and wherein the housing member contains a locking feature that is adapted to secure the interconnecting rod member to the housing member; wherein, a distance between the intersection and the distal abutment surface of the proximal head member varies with rotation of the proximal head member relative to the inner shank member; and wherein rotation of the proximal head member relative to the inner shank member produces (a) longitudinal movement of the inner shank member relative to the outer shank member, (b) advancement of the intersection against the distal region of the outer shank member, and (c) radial expansion of the distal region of the outer shank member.