Dual S2 Alar-Iliac Screw Technique With a Multirod Construct Across the Lumbosacral Junction: Obtaining Adequate Stability at the Lumbosacral Junction in Spinal Deformity Surgery

Abstract

To illustrate the safe placement of a 5-screw/5-rod construct across the spinopelvic junction in a complex revision case utilizing 4 S2 alar-iliac (S2AI) screws as well as an iliac screw for a kickstand rod. The S2AI screws are often used for lumbosacral fixation at the base of long spinal deformity constructs. In severe spinal deformities, additional pelvic fixation beyond the standard 2 screws may help achieve and maintain correction, and also increase the rigidity of the construct. With a thorough understanding of pelvic anatomy, multiple pelvic screws, such as bilateral dual S2AI screws, may be placed safely to achieve stability and accommodate additional rods to perform powerful correction techniques. We illustrate the safe use of multiple rods across the lumbosacral junction in this case, by using both a hook rod construct and domino connectors - ultimately though these additional rods rely on the integrity of the pelvic fixation to provide their support. We recommend at least 3 rods across the lumbosacral junction in any adult spinal deformity case requiring pelvic fixation, and would recommend considering more than 3 rods, especially across 3-column osteotomy sites. For long spinal constructs in patients with significant adult spinal deformity, we believe the use of multiple pelvic screws to a multirod construct is a safe and effective way to provide long-term correction and clinical success.

Keywords: Pelvic fixation; Spine deformity; Spine surgery.

Fig. 1.

Preoperative computed tomography 3-dimensional reconstruction. Solid fusion mass from previous Harrington rod instrumentation resulting in a fixed deformity is visualized from T5–L1, necessitating an L5 pedicle subtraction osteotomy to achieve correction.

Fig. 2.

Pre- and postoperative imaging of a 61-year-old woman presenting with a flatback syndrome and severe coronal and sagittal imbalance. Preoperative imaging (A, B) illustrating a right trunk shift with positive sagittal alignment and postoperative imaging (C, D) following revision instrumentation and fusion with a kickstand rod and multirod construct across the lumbosacral junction. Detailed postoperative imaging of the multirod construct across the lumbosacral junction (E, F).

Fig. 3.

Dual bilateral S2 alar-iliac (S2AI) screw placement. (A-D) The superior and inferior S2AI screws seen here in patient A from proximal to distal, demonstrating nearly identical intraosseous screw trajectory. (A-C) The kickstand screw can be seen passing orthogonally anterior to the superior S2AI screw on the right.