Patent ID: 7291153

Claim:
A bone screw assembly comprising: a screw having a head with a convex portion, the screw comprising an elongated shank having bone threads thereon and the head located at one end thereof; a receiver having a U-shaped portion for receiving a spinal fixation rod and a concave portion for receiving the head, the concave portion having a radius of curvature which is less than a radius of curvature of the convex portion of the head, the receiver comprising a body having an aperture therethrough for receiving the shank and having the concave portion located at the aperture, the U-shaped portion of the receiver further comprising a channel therethrough opposite the aperture, the channel receiving the spinal fixation rod; and a compression member between the spinal fixation rod and the head; the head having a second convex portion facing the compression member and the compression member having a second concave portion facing the head, the second concave portion having a radius of curvature less than a radius of curvature of the second convex portion.