Anatomical Study of a Novel Iliosacral Screw Placement for Sacrum-pelvis in Adult via Computed Tomography Reconstruction

This is a cross-sectional study. To investigate the feasibility and safety of a novel iliosacral screw placement for sacrum-pelvis in adult pelvis by computed tomography (CT) reconstruction. The optimal technique of spino-pelvic fixation is still being developed and redefined. However, neither the relevant anatomic parameters nor the potential spinal canal involvement for a novel iliosacral screw placement have been clearly analyzed. A total of 60 adults with normal pelvis, with the age ranging from 24 to 79 years old, were included in this study. Based on three-dimensional (3D) CT reconstruction of each pelvis, virtual iliosacral screw channel was identified bilaterally, the trajectory of which was characterized with the optimal width and length from the ilium to the sacrum. The virtual iliosacral screw channel that holding the greatest width and length of osseous channel was measured by rotating the 3D pelvis. Measurements of the determined channel on either side included iliosacral-screw-related and connector-related parameters. There was a virtual iliosacral screw channel passing through the ilium, the iliosacral joint and then into the sacrum on either side of each pelvis. The caudal angle, convergent angle, and maximal length were 16.3 ± 3.0°, 61.3 ± 5.9°, 97.0 ± 5.6 mm in male, respectively. In female, they were 16.4 ± 3.9°, 63.0 ± 5.5° and 96.2 ± 6.0 mm, respectively. The ideal direction of the connector was from posteromedial to anterolateral. The cephalad angle, divergent angle, and embedding depth of the connector were 28.0 ± 5.7°, 28.7 ± 5.9° and 19.0 ± 2.9 mm in male, respectively. In female, they were 26.7 ± 6.1°, 27.0 ± 5.5° and 16.4 ± 2.6 mm, respectively. It is safe and feasible to place the iliosacral screw when performing this novel instrumentation. Preoperative CT imaging and 3D reconstructions may help to determine the correct entry point and the trajectory of iliosacral screw. Level of Evidence: 5