A polyaxial body is selectively removable from a pedicle screw in a spinal fixation system without disruption of the screw's placement in the patient's spine. The polyaxial body according to various embodiments of this invention may be locked relative to the screw head and coupled to the spine rod without deformation of the screw or body components while still allowing for subsequent removal of the body from the screw head. The head of the pedicle screw is threadably engaged with a retainer ring on the polyaxial body thereby permitting selective removal of the body from the screw head without disrupting the placement of the screw in the spine. This allows for the pedicle screw to remain in the spine as the fixation system is adjusted as required by the surgeon for subsequent and reliable reanimation.