Amir Abdul-Jabbar1, Emre Yilmaz2, Joe Iwanaga3, Tamir Tawfik1, Thomas M O'Lynnger1, Thomas Armin Schildhauer4, Jens Chapman1, Rod J Oskouian5, R Shane Tubbs6. 1. Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA. 2. Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA; Seattle Science Foundation, Seattle, Washington, USA; Department of Trauma Surgery, BG University Hospital Bergmannsheil, Ruhr University, Bochum, Germany. Electronic address: emre.yilmaz@gmx.de. 3. Seattle Science Foundation, Seattle, Washington, USA. 4. Department of Trauma Surgery, BG University Hospital Bergmannsheil, Ruhr University, Bochum, Germany. 5. Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA; Seattle Science Foundation, Seattle, Washington, USA. 6. Seattle Science Foundation, Seattle, Washington, USA; Department of Anatomical Sciences, St. George's University, Grenada.
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.
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.
Authors: Bradley J Vivace; Joseph L Laratta; Jeffrey L Gum; Jamal N Shillingford; John R Dimar Ii; Steven D Glassman; Lee A Tan; Nana O Sarpong; James D Lin; Ronald A Lehman; Yongjung J Kim; Lawrence G Lenke Journal: N Am Spine Soc J Date: 2020-07-12