Figure 7a. Posterior spinal fusion. Anteroposterior (a) and lateral (b) radiographs of the lumbar spine show posterior spinal fusion of L4-S1 with a pedicle-screw fixation spinal system with two transverse connectors (Moss Miami system polyaxial screws; DePuy AcroMed, Raynham, Mass). In addition, metallic cage devices (BAK; Zimmer Spine, Minneapolis, Minn) are placed at the L4–5 disk space level, right back to front/correct (arrowhead) and left front to back/upside down (arrow).