An embodiment of the invention provides for a pedicle screw system including a bone anchor, linkage rod, tulip, set screw, and detent plate. When the set screw is fully tightened against the detent plate, pluralities of ridges on opposing faces of the detent plate and set screw cooperate by providing catches to prevent unwanted loosening of the set screw, which could lead to unwanted rod slippage and instability in the orthopedic fixation unit.