Neurovascular Relations in Modified Iliac Screws and Traditional Iliac Screw: Anatomic Study

This study describes a modified iliac screw technique and compares it with the traditional iliac screw in regard to neurovascular structures at risk. Few studies have detailed the insertion point's surrounding anatomy and its relationship to vulnerable neurovascular structures when this modified technique is used. Therefore we describe our modified iliac screw entry and trajectory and detail the surrounding anatomy and neurovascular structures at risk with this technique in comparison with the "gold standard" trajectory.

The traditional iliac screw (TS) and modified iliac screw (MS) were placed into 12 fresh-frozen adult cadavers (3 female, 9 male). We measured the screw-to-supragluteal artery, vein, and nerve (SGANV) bundle and screw-to-sciatic notch distances. Further, we dissected the medial cortical border of the iliac screw to identify its final position with respect to the surrounding anatomy.

No medial or lateral cortical breaches were visualized after screw placement. The MS was 18.31 mm from the greater sciatic foramen compared with 18.65 mm with the TS. The smallest distance from the MS to the greater sciatic foramen was 13.9 mm compared with 14.8 mm with the TS, an insignificant difference. The SGANV bundle-to-MS distance was 20.6 mm, and SGANV bundle-to-TS distance was 20.77 mm, again an insignificant difference.

Using the modified iliac screw technique does not change the intraosseous pathway (and thus bone purchase) with respect to the distance between the screw and neurovascular structures at risk.