"Rod introduction from cephalad to caudad." The rod is being introduced cephalad to caudad. Notice the open-ended MIS connector at the proximal and distal incisions. These serve as posts against which the rod can be manipulated and also enable easy visualization of the rod.
Sarwahi et al. Scoliosis 2011 6:16 doi:10.1186/1748-7161-6-16