US Patent 7186255 Polyaxial screw

A polyaxial screw is used to secure orthopedic appliances to bone, particularly the spine. The polyaxial screw has a shaft including a helical screw thread for securing the screw to bone. One end of the shaft has a reverse tapered head tapering toward and away from the shaft from an enlarged median. A spherical shaped swivel, having an opening smaller than the median, is snapped over the head to rotatably engage the shaft. A connector with a dome shaped cavity on one end and bifurcated tabs on the other is connected with the swivel and tightened in place with a set screw and guide ring. An appliance is held between the bifurcated tabs. The tabs are frangible to reduce the profile above the appliance.