The present disclosure includes fixation devices that comprise one or more porous elements or fenestrations to aid in osteo-integration of the fixation device. These fixation devices may be additively manufactured using biocompatible materials such that the solid and porous aspects of the screw are fused together into a single construct. Spinal stabilization systems are also disclosed having spanning portions extending between and securable to pedicle screw assemblies, the spanning portions have stiffness characteristics that may be variable or selectively adjustable, and/or have non-linear behavior with respect to force versus distortion. Additionally, the systems may utilize a plurality of spanning portions in which two or more of the spanning portions have different stiffness characteristics. Methods for fabricating and using the foregoing devices are also described herein.
