A spinal rod extension system includes a rod portion of a spinal rod extension and a connector portion connected to the rod portion. The connector portion is configured for insertion through a screw head of an existing pedicle screw that is used to secure an existing spinal rod. The spinal rod extension system also includes a screw head connector configured to mount to the screw head of the existing pedicle screw to secure the connector portion to the existing spinal rod. The screw head connector includes a first end wall and a second end wall that are connected to one another by a pair of cross connectors.