Devices, systems and methods for the treatment of spinal instability and/or stenosis of the spinal canal and neural foramina. In one embodiment, a functional spinal unit (FSU) of a subject is approached through a lateral or antero-lateral corridor, and both an anterior and posterior column of the FSU are manipulated, implanted and/or otherwise surgically treated through the same intra-abdominal surgical corridor. A method is disclosed to reach the posterior aspect of the FSU, wherein the intra-abdominal surgical corridor is extended posterior to the psoas major muscle and through the thoraco-lumbar fascia in order to reach the transverse process and/or facet joint. Multiple trajectories for bone screw fixation of the vertebral bone are additionally disclosed. In another embodiment, the FSU is approached through the above corridor and a second posterior skin incision and corridor. The combination of the corridors provided circumferential access to the FSU.