Abstract: A minimally invasive system and method for coupling a spinal rod to a plurality of bone anchors implanted into a plurality of vertebral bodies. A plurality of bottom-loading polyaxial anchor seat assemblies having different vertical heights are chosen to pop over the heads of the implanted bone anchors and a spinal rod is more easily introduced and secured to the bone anchors. The variety of different heights that characterize the plurality of polyaxial anchor seat assemblies allows a surgeon to intraoperatively choose the appropriate offset for a particular spinal level during spinal corrections.