Is the Iliac Cortical Density Similarly Positioned in the Developing Pediatric Pelvis?

The iliac cortical density (ICD) is a critical fluoroscopic landmark for pelvic percutaneous screw placement. Our purpose was to evaluate the ICD as a landmark in pediatrics and quantify the diameter of osseous pathways for 3 screw trajectories: iliosacral (IS) at S1 and transiliac-transsacral (TSTI) at S1 and S2.

Two hundred sixty-seven consecutive pelvic CT scans in children 0-16 years of age were analyzed. ICD and S1 vertebral heights were measured at multiple regions along S1. Their height and corresponding ratios, as well as osseous screw corridor dimensions were compared between age groups and by the dysmorphic status.

In the nondysmorphic pelvises, S1 height, ICD height, and the ICD to S1 height ratio increased across age groups for all locations (P < 0.001). All 3 screw pathway diameters increased with age (P < 0.001). In the dysmorphic group, there was no increase in ICD to S1 height ratio with age. Except for the age 0-2 group, the ICD to S1 height ratios were significantly larger in the nondysmorphic group. In the dysmorphic group, S1 TSTI pathway remained narrow with age, whereas IS at S1 and TSTI at S2 had a significant increased diameter with age (P < 0.001).

The ICD is a useful fluoroscopic landmark for percutaneous screw placement in the pediatric pelvis. For nondysmorphic pelvises, the ICD to S1 height ratio, as well as osseous corridors for IS, TSTI at S1, and TSTI at S2 screw trajectories increase significantly with age. The margin for safe screw placement in S1 is smaller for younger and dysmorphic pelvises.