Sagittal alignment of the spine: What do you need to know?

• Sagittal analysis of the spine is not a deformity specific exercise.
• Pelvic morphology is the foundation for spinal alignment.
• SRS-Schwab sagittal modifiers are established targets for spinal realignment.
• Realignment procedures should respect age-adjusted alignment targets.

Sagittal alignment, often misrepresented as sagittal balance, describes the ideal and “normal” alignment in the sagittal plane, resulting from the interplay between various organic factors. Any pathology that alters this equilibrium instigates sagittal malalignment and its compensatory mechanisms. As a result, sagittal malalignment is not limited to adult spinal deformity; its pervasiveness extends through most spinal disorders. While further research is developing, the literature reports clinically relevant radiographic parameters that have significant relationships with patient-reported outcomes. This article aims to provide a pragmatic review of sagittal plane analysis. At the end of this review, the reader should be able to analyze the sagittal plane of the spine, identify compensatory mechanisms, and choose patient-specific alignment targets.