Asymmetric Safety Corridors for Free-Hand S2-Alar-Iliac Screw Placement: Quantifying Direction-Specific Tolerance Around Patient-Specific Optimal Trajectories. - Park, Se Jun; Kim, Dong Kyu; Yoo, Sun Joon; Jang, Hyun Jun; Moon, Bong Ju; Park, Jeong Yoon; Shin, Jun Jae; Kuh, Sung Uk; Chin, Dong Kyu; Kim, Keun Su; Kim, Kyung Hyun (Journal of Clinical Medicine, 2026)