US Patent 7942911 Polyaxial bone screw

A fastening system for bone screws used in spinal fixation systems for reshaping the spine of a patient. The bone screw has threads on one end for anchoring in the spine. The other end has a spherical head with a multi sided recess formed therein for engagement with an appropriate driving tool. The system includes a stabilizing rod, a saddle member, a cap member and a set screw with at least one bone screw having a outer diameter that exceeds the diameter of a cavity formed in the saddle, wherein placement of the bone screw is made possible by matching the threads of the set screw to the threads of the bone screw. The head of the bone screw providing proper positioning of the stabilization rod within the patient.