A bone anchor which has thread characteristics on the distal shaft adjacent the tip suitable for engaging bone cement and different thread characteristics on the proximal shaft adjacent the head suitable to engage and secure the anchor to natural cancellous and cortical bone. The thread on the distal shaft is designed to engage and secure the anchor to bone cement embedded within the bone without fracture of the bone cement. In particular embodiments, the distal shaft bears two threads which merge to form a single proximal thread on the proximal shaft, the distal threads having half the pitch of the proximal thread.