Title

Neurovascular Relationships of S2AI Screw Placement: Anatomic Study.

Document Type

Article

Publication Date

8-1-2018

Keywords

Anatomy; Complications; Pelvis; S2AI; Spine; Spinopelvic fixation; Surgery

Abstract

INTRODUCTION: The S2 alar-iliac (S2AI) screw is a modification of the traditional iliac fixation technique and has surgical and biomechanical benefits. However, there are significant regional neurovascular structures along the path of such screws. Therefore the current anatomic study was performed to better elucidate these relationships.

METHODS: Using fluoroscopy, S2AI screws were placed in 2 adult cadavers through a standard posterior midline exposure. The screw insertion point was placed 10 mm lateral to a line bisecting the S1 and S2 foramina, adjacent to the sacroiliac joint. Using 30- to 40-degree lateral angulation from the midline and 20- to 30-degree caudal angulation, a pedicle probe was directed toward the anterior inferior iliac spine. The final trajectory was positioned to sit 1-2 cm superior to the greater sciatic foramen. Lastly, the screws and surrounding bone were drilled in order to visualize both lateral and medial neurovascular relationships.

RESULTS: Removing the bone around the S2AI-screw illustrated the close relationship to the medial (internal) neurovascular structures including the obturator nerve, lumbosacral trunk, sacral plexus and, specifically, the S1 ventral ramus and iliac vein and artery. By removing the outer cortex of the ilium, the close relationship to the superior gluteal artery, vein, and nerve was observed. In addition, we were able to identify the proximity to the iliopsoas muscle and internal iliac vessels.

CONCLUSIONS: A comprehensive knowledge of the surrounding neurovascular anatomy relevant to S2AI screw placement can decrease patient morbidity and allow spine surgeons to better diagnose potential postoperative complications.

Clinical Institute

Neurosciences (Brain & Spine)

Clinical Institute

Orthopedics & Sports Medicine

Department

Orthopedics

Department

Neurosciences

Department

Surgery

Volume

116

First Page

108

Last Page

108

PubMed ID

29689397

Journal Title

World Neurosurg

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