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

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. 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. 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.