A, Preoperative lateral radiograph of the spine in a 14-year-old boy with symptomatic grade III spondylolisthesis that failed to respond to nonsurgical treatment. Sagittal T2-weighted magnetic resonance image (B) and lateral radiograph (C) of the spine following treatment with a posterior lumbosacral approach with L5-S1 laminectomy, bilateral foraminotomies and nerve-root decompression, osteotomy of the sacral dome with resection of the inferior end plate of L5, partial reduction of slippage, and posterior instrumentation and fusion of L5-S1 with an interbody prosthetic cage and bone grafting.