Feasibility analysis and clinical validation of iliac screw placement medial to the posterior superior iliac spine in lumbopelvic fixation

English Keywords:Spinopelvic fixation  Imaging characteristics  Medial approach of the posterior superior iliac  Iliac screw placement  Surgical technique  Surgical outcomes

English Abstract:

  【Abstract】 Objectives: To investigate the feasibility and ideal trajectory of medialized entry iliac screws(MEIS) placed in the posterior superior iliac in spinopelvic fixation through imaging and anatomic analyses, and to validate in clinical practice. Methods: The imaging data of 90 patients(45 males, 45 females; 57.5±1.6 years) without spinal or pelvic pathology who underwent pelvic CT scan in the radiology department of our hospital between June 2022 and September 2024 were collected. Three-dimensional pelvic reconstruction was performed using Mimics 21.0 software. The parameters of the bony channels of the iliac were measured and compared between males and females, including short and long axes of teardrop cross-section, the narrowest and widest inter-cortical distances of the iliac corridors, sacroiliac joint angles, and screw-to-sagittal plane angles. The ideal screw trajectory for MEIS was determined based on imaging and anatomical characteristics, and standard surgical procedures were formulated, which were applied in 5 patients. Results: No significant gender differences were observed in the narrowest iliac corridor width(males: 15.19±1.81mm vs. females: 15.01±2.24mm, P>0.05), widest corridor width(males: 24.16±1.66mm vs. females: 24.44±2.92mm, P>0.05), or sacroiliac joint angle(males: 39.63°±4.13° vs. females: 40.76°±2.94°, P>0.05). However, significant gender differences were found in the screw-to-sagittal angle(males: 30.38°±3.15° vs. females: 26.72°±5.64°, P<0.05), as well as in the teardrop short axis(males: 22.00±1.25mm vs. females: 20.47±1.73mm, P<0.05) and long axis(males: 32.92±2.85mm vs. females: 30.80±1.48mm, P<0.05). Notably, the narrowest and widest inter-cortical distances of the iliac corridors, and short and long axes of teardrop cross-section exceeded the diameter(9mm) of a iliac screw(P<0.001). Postoperative imaging examinations of the 5 patients who underwent this surgical procedure showed that all implants were stably positioned, with satisfactory improvement in symptoms and functional outcomes.Conclusions: The MEIS placement in the posterior superior iliac is safe and feasible, which can serve as a new option for iliac screw placement trajectory in spinopelvic fixation.