S3 sacral-alar iliac screws application in partial sacral resection for an aneurysmal bone cyst: illustrative case

Abstract

Background: Sacropelvic fixation is used in the management of deformity, neoplasms, and fractures. S2-alar-iliac (S2AI) screws have evolved as a technique for sacropelvic fixation to address disadvantages associated with traditional iliac screws. In select patients, S2AI screw placement is not feasible due to patient anatomy, trauma, or osteolytic lesions.

Observations: A 15-year-old girl presented with a 3-month history of right S1-2 radicular pain and right dorsiflexion and plantar flexion weakness. Imaging revealed a right sacral alar aneurysmal bone cyst. The patient underwent right S1-3 hemilaminectomies and partial resection of the S2 and S3 vertebral bodies. Following adequate bony decompression, tumor debulking was performed. Bilateral L4-S1 pedicle screws and left S2AI screws were then placed using neuronavigation guidance. Due to right S1-2 sacral resection, S2AI screw placement was unfeasible. Right-S3 alar-iliac (S3AI) screw placement was performed, and good sacropelvic fixation was demonstrated. Herein, the authors describe the first clinical application of S3AI screw placement in a pediatric patient. After surgery, the patient experienced an improvement in symptoms before later tumor recurrence, which required adjuvant therapy. Long term follow-up revealed solid fusion with stable spinal alignment.

Lessons: In select patients in whom S2AI screw placement is not an option, S3AI screw placement is a feasible, safe, alternative for sacropelvic fixation. https://thejns.org/doi/10.3171/CASE25267.

Keywords: pelvic deformity; sacral alar iliac screws; sacropelvic fixation.

FIG. 1.

Coronal (A), axial (B), and sagittal (C) preoperative T2-weighted MR images demonstrating a 6.8-cm right sacral ala aneurysmal bone cyst with multiple fluid-fluid levels extending into the S1–3 foramen. Axial (D) and sagittal (E) preoperative CT scans redemonstrating a large osteolytic aneurysmal bone cyst centered in the right sacral ala with associated bony erosion and alar remodeling.

FIG. 2.

Anteroposterior (A) and lateral (B) postoperative radiographs demonstrating appropriate instrumentation placement and good alignment. Sagittal (C) and axial (D) T2-weighted MR images demonstrating interval debulking of the aneurysmal bone cyst.

FIG. 3.

Axial (A), sagittal (B), and coronal (C) 3-month postoperative T2-weighted MR images demonstrating interval recurrence of partially resected aneurysmal bone cyst.