Transsacral Screws in Combination With an Expandable Cage for High-Grade Spondylolisthesis: A Novel Technique Involving Transsacral/Transforaminal Lumbar Interbody Fusion.

High-grade spondylolisthesis at the L5/S1 level presents significant surgical challenges due to marked instability and neural compression. Traditional fusion techniques often need to extend beyond the index level to achieve stable fixation. Moreover, a second surgery is sometimes required to restore mobility at the additionally instrumented segments. We present a case of a 19-year-old female with severe lumbar and bilateral sciatic pain caused by a Meyerding grade III L5/S1 spondylolisthesis. The patient underwent a laminectomy and bilateral L5 nerve root decompression, followed by transsacral screw fixation combined with an expandable interbody cage. Postoperatively, she achieved marked pain relief, restoration of lumbosacral alignment, and radiographic evidence of solid fusion at six months. No neurological deficits or implant-related complications were observed. This technical note describes a novel single-stage approach for the treatment of high-grade L5/S1 spondylolisthesis. The key advantage of this technique lies in its biomechanical stability, achieved by combining transsacral screw fixation with an interbody cage, unlike previous methods that used either longer-segment instrumentation with a cage or transsacral screws without a cage. These findings are limited by the single-case nature and short follow-up period, but the technique may represent a promising option for enhanced stabilization in high-grade slips.