The anatomical bone corridor study of schanz screw placement in adolescent pelvic ring fractures via three-dimensional CT

Purpose To define the anatomical boundaries of potential safe corridors for the placement of Schanz screws during external fixation of unstable pelvic fractures in normally developed adolescents aged 11–14 years. Patients and methods Pelvic CT scans of 34 patients (18 males, 16 females; mean age 12 years) were reconstructed into 3D models using Mimics 21.0. A supine coordinate system was defined using anatomical landmarks, including the anterior superior iliac spine (ASIS), posterior superior iliac spine (PSIS), and anterior inferior iliac spine (AIIS). Cross-sectional measurements of the iliac wing and supra-acetabular corridors were performed, simulating 4 mm Schanz screw trajectories and documenting entry points, angles, and corridor dimensions. Results Iliac Wing Corridor: The morphology transitioned from proximal rectangular to mid-corridor dumbbell-shaped, with distal funnel-like narrowing. Anterior/posterior corridor lengths measured 54.2–58.6 mm and 68.1–73.1 mm (95% CI), respectively. Screw I1 entry (16.9–18.7 mm posterior to ASIS; 95% CI) required horizontal/sagittal angles of 22.5–25.8° and 53.7–61.2° (95% CI). Screw I2 entry (49.4–53.6 mm posterior to ASIS; 95% CI) necessitated horizontal/sagittal angles of 21.5–25.1° and 61.3–66.1° (95% CI). Supra-acetabular corridor S-shaped with mid-corridor constriction. The longest trajectory (116.7–125.3 mm; 95% CI) aligned with the AIIS-PSIS central plane, while the shortest (95.9–105.9 mm; 95% CI) occurred in the periacetabular region. Screw A insertion via the AIIS-PSIS plane required horizontal/sagittal angles of 58.2–61.3° and 23.0–25.6° (95% CI), respectively. Conclusion Both iliac wing and supra-acetabular corridors demonstrated safe accommodation of 4 mm Schanz screws in this age group. Adherence to predefined entry points and angles is critical to minimize perforation risk and optimize fixation stability. Patient-specific computer-assisted preoperative surgical planning is particularly well-suited for adolescents in enhancing surgical safety.