S1 Pedicle Subtraction Osteotomy for Fixed Sagittal Imbalance and Lumbosacral Kyphosis.

S1 pedicle subtraction osteotomies (PSOs) are indicated in patients with fixed, high-grade L5-S1 spondylolisthesis or kyphosis secondary to a sacral fracture, who present with severe sagittal imbalance. Unlike lumbar PSOs, sacral osteotomies are rare, and there is a paucity of literature outlining techniques. Here, we present the indications, planning, technique, and outcomes for S1 PSOs.