A spinal stabilization system includes an implant and instrumentation for stabilizing the spine. In one embodiment, the system includes a plate having a side rail and a channel extending adjacent the side rail. A pedicle screw assembly is positioned in the channel in releasable engagement with the side rail. The pedicle screw assembly includes a polyaxial screw seated in a lower housing having a lower locking flange. An upper housing having an upper locking flange secures the plate to the lower housing. The side rail of the plate is releasably engaged between the upper locking flange and the lower locking flange. The upper and lower housings include on-board locking mechanisms for fixing components in the screw assembly. The screw assembly and plate are inserted and oriented by remote manipulation. Minimally invasive techniques for inserting the implant are performed with the instrumentation, and cause minimal disturbance to surrounding tissue.