Criteria to restore the sagittal balance in deformity and degenerative spondylolisthesis

Purpose To present in a single source the relevant information needed to assess spinopelvic balance and alignment, and to estimate the amount of correction needed in a patient during surgical treatment.Methods Narrative literature reviewResults Sagittal balance can be evaluated by global balance estimates (sagittal vertical axis and T1 tilt). Other important parameters are the relationship between pelvic incidence and lumbar lordosis (spinopelvic harmony), between pelvic incidence and difference of thoracic kyphosis and lumbar lordosis (spinopelvic balance), excess of pelvic tilt, knee flexion and thoracic compensatory hypokyphosis. Different methods to calculate the amount of surgical correction needed in patients with sagittal imbalance have been based on combinations of these parameters.Conclusions Relevant parameters of sagittal imbalance have been identified and correlated with clinical outcomes. Methods for calculation of surgical correction of imbalance have been proposed, but not validated in patients with midterm follow-up.