BACKGROUND: Flat back deformity is a disabling adverse outcome following instrumented lumbar fusion. As patients are often fused in this non-physiologic alignment, correction is complex and has conventionally required fracture of the preexisting fusion mass. Sacral osteotomy may be one effective means of correcting the positive sagittal balance in these patients. Here we report a case of flat back deformity corrected using a 3-column sacral osteotomy, and systematically review the available literature on the effectiveness of 3-column sacral osteotomy for correcting flat back deformity. METHODS: A systematic review was performed using the results of a search of the PubMed, EMBASE, Web of Science, and Cochrane databases according to PRISMA guidelines. We also include our patient as an example of the technique. RESULTS: Eight studies-all case reports or small case series-were identified describing 37 patients, including our case example. The variety of techniques was too heterogeneous for meta-analysis, but all studies reported good correction of sagittal deformity. Transient L5 palsy was the most common side effect of this technique, being reported in 21 patients (56.8%) across all studies. CONCLUSIONS: Sacral osteotomy is potentially an effective means of correcting positive sagittal balance in patients with flat back deformity secondary to high pelvic incidence.