Provided is a modular pedicle screw assembly which includes various components that may be configured in various manners so as to provide different functionalities to the pedicle screw assembly. This advantageously decreases surgery time, reduces repetitive and tedious surgical steps, and allows for streamlining inventory of expensive medical equipment. In one embodiment, a pedicle screw assembly includes a pedicle screw, a rod holding element, an insert, a rod, and a set screw. The insert may have a uniplanar configuration which allows movement of the insert, prior to final attachment, in a plane of motion. The insert may optionally have a monoaxial configuration which prevents movement of the insert. A method is also provided for securing a rod to a pedicle screw assembly. Also provided is an assembly tool for use in assembling a pedicle screw assembly.