The aim of this study is to describe a surgical procedure proposed for high-grade isthmic spondylolisthesis, with intraoperative reduction using Jackson's intrasacral fixation. The procedure is performed using a single posterior approach. The intraoperative correction of the deformity is obtained by sacral dome resection and reduction of the lumbosacral kyphosis using Jackson's fixation to rotate the sacrum. After sagittal balance restoration, L4-S1 circumferential fusion is performed with interbody cages. The technique is effective in the restoration of spinal and pelvic parameters of sagittal balance, and optimal conditions for fusion are obtained. The use of Jackson's intrasacral fixation provides the strong stability needed to correct the lumbosacral deformity, with little neurological risk during intraoperative reduction.