A reinforcement cap for use with pedicle screws and rod receptacles (“tulips”) in spinal support systems. The unitary reinforcement cap engages both the internal and the external surfaces of the wall segments of the rod receptacle. In some embodiments, both the internal and the external surfaces are threadably engaged. By doubling the number of threads that are engaged, additional strength and structural integrity are realized over conventional set screw arrangements. Also, because of the unitary construction, wherein an internal set screw portion and an external skirt portion are integral to the reinforcement cap, lateral movement between the set screw portion and the skirt portion is limited. In some embodiments, the threads are of a canted cantilever construction, wherein the interfaces of threadably engaged components are tailored to generate reaction force vectors that mitigate slippage at the threaded interfaces.
