This invention relates to a transdiscal screw capable of following a non-linear trajectory. The screw assembly includes a first screw and second screw coupled at a poly-axial joint. The first screw and the second screw capable of rotating independently of each other. The screw can also include a third screw coupled to the second screw at a poly-axial joint such that the first screw, second screw and third screw can rotate independently of each other.