Low profile spinal fixation system

摘要

There is provided a spinal fixation system (500) for fixing an elongate member (16) in a desired position relative to a patient's spine, the spinal fixation system comprising: a bone anchor member (502) for being secured to a vertebral bone of the spine; a coupling member (512) having an axis and an internal space for receiving the elongate member extending therethrough in a direction transverse to the coupling member axis; a cap member (518) for being turned about the coupling member axis to a locked position thereof and locking the elongate member in the coupling member; a saddle member (520) disposed between the cap member and the elongate member for being tightly engaged against the elongate member with the cap member in the locked position; a connector member (519) distinct from the cap member and the saddle member for keeping the cap member and saddle member assembled together and allowing the saddle member to shift axially along the coupling member axis upon turning of the cap member; and cam surfaces (702, 704) between the cap member and the saddle member configured so that turning of the cap member toward the locked position causes the saddle member to be driven axially toward the elongate member without requiring axial movement of the cap member.