Modified S1 Pedicle Subtraction Osteotomy

Study Design: Surgical technique video. Objective: To report a surgical technique to revise patients with previous fusions at L4–S1 leading to an iatrogenic flat back and sagittal imbalance using L5–S1 transforaminal interbody fusion combined with a small S1 corner osteotomy. Background: This is a case of a woman (51 y old) with a history of multiple lumbar surgeries, severe back pain, sagittal imbalance, and loss of lordosis. Methods: We describe a feasible revision technique in a complex patient with the goal of attaining optimal distribution of lumbar lordosis and sagittal balance through a modified S1 pedicle subtraction osteotomy, and the use of an interbody cage to enhance the fusion rate and facilitate closure of the 3-column osteotomy. Results: The preoperative patient lordosis angle of 31 degrees at L1–L4 and 16 degrees at L4–S1 became 12 degrees at L1–L4 and 44 degrees at L4–S1 postoperatively. Conclusion: The combination of L5–S1 transforaminal interbody fusion and S1 corner osteotomy is a feasible technique for the restoration of lumbar lordosis in patients with previous fusion and consequent loss of lordosis.