Optimal trajectory and insertion accuracy of sacral alar iliac screws

Abstract

Objective: The aim of this study was to analyse the optimal trajectories for sacral alar iliac screws (SAISs)in a Japanese patient population and the clinical assessment of insertion accuracies.Methods: The ideal trajectories of SAISs, starting from 2 mm medial to the apex of the lateral sacral creston the midline between S1 and S2 dorsal foramina, were measured in 80 consecutive spinal diseasepatients (40 males and 40 females; average age: 67.4± 8.1 years) using three-dimensional computedtomographic image software. Following these anatomic analyses, accuracies of 32 inserted SAISs inconsecutive patients, who underwent long spinal posterior fusion, were investigated clinically.Results: Lateral angulations of optimal SAIS trajectories in males (left: 37.9; right: 37.7) were signiŞcantlylarger than those than in females (left: 32.8; right: 32.4). Caudal SAIS angulations for females (left: 33.4;right: 33.9) were signiŞcantly larger than those in males (left: 27.5; right: 28.0). The 32 SAISs (100 mmlong and 9 mm in diameter) assessed clinically were accurately inserted on optimal trajectories.Conclusion: The optimal trajectories of SAISs in a Japanese patient population are more lateral in malesand more caudal in females. This study examines the clinical safety and accuracy of SAIS insertion onthese optimal trajectories.