Pedicle screws are designed to provide polyaxial coupling to pedicles of a vertebra. Intermediate pieces are attached to the pedicles screws and receive extender shafts. Extenders are inserted in the intermediate piece. The extenders project the anatomic points located in the cage outside the patient's body to facilitate proper contouring of a rod. An alignment linkage is used to ensure that the extenders are parallel to each other. The alignment linkage includes a linkage frame, an articulating linkage and a locking member. The articulating linkage has all rotational degrees of freedom and thereby adapts to any varying trajectories of the extenders and distance between the extenders. The alignment linkage includes a locking member with a pop-up indicator. The pop-up indicator notifies the users when the locking member is tightened with two of the extenders in non-parallel configuration.