Synonym: Iliac Cortical Line
Iliac cortical densities (ICD) are the overlap of the true pelvis posterior to the acetabulum which is used as a proxy for the slope of the sacral ala.
Importance:
The entry point should be anterior in S1 and inferior to the iliac cortical density (ICD), which parallels the sacral alar slope, usually slightly caudal and posterior. The ICD thus marks the anterosuperior boundary of the safe zone for an iliosacral screw which may injure the L5 nerve root if it penetrates this cortex.
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