US Patent 7270665 Variable offset spinal fixation system

A bone fixation system for locking a longitudinal member, such as a spinal rod, to a bone anchor element allowing a variable orientation of the axis of the longitudinal member relative to the axis of the bone anchor. A one-piece body element split along a substantially horizontal plane into upper and lower portions by a slot includes a ball element through which a longitudinal member, such as a spinal rod, may pass. A portion of a bone anchor element passes through an aperture having portions on each of the upper and lower portions of the body element. Tightening a set screw draws the upper and lower portions of the body element together and locks the bone anchor and spinal rod into the desired position.