Tavares MCM, et al. - In this observational, retrospective, analytical descriptive study, authors estimated the insertion as well as positioning parameters of the S2-alar-iliac and iliac screw techniques in 25 adult subjects without spinal deformities. They recorded the mean length of the iliac screw greater than that of the S2-alar-iliac screw, and the S2-alar-iliac screw sat 20.5 mm deeper as compared to the iliac screw. They also noted 20.72 mm, the mean of the greatest bone thickness for the iliac screw whereas that of the S2-alar-iliac screw was 23.24 mm. The mean distance from the iliac screw entry point to the skin was reported, 32.46 mm; and 52.87 mm, the mean distance from the S2-alar-iliac screw entry point to the skin. They noticed the desirable clinical advantages of S2-alar-iliac technique in terms of the diameter of screws and decreased protrusion when practiced in adults.