Sagittal spinal alignment in adolescent idiopathic scoliosis: a narrative review of pre- and post-treatment characteristics.

Adolescent idiopathic scoliosis (AIS) involves significant sagittal plane abnormalities, most consistently characterized by reduced thoracic kyphosis (TK), with compensatory changes in lumbar lordosis (LL) and cervical lordosis (CL). Brace treatment effectively controls coronal curve progression but commonly reduces TK and LL, potentially leading to a flatback deformity, while global sagittal balance is often maintained through spinal and pelvic compensation. Surgical intervention, particularly posterior spinal fusion, reliably improves sagittal alignment, with the most pronounced restoration of TK and CL observed in patients with preexisting sagittal malalignment. Despite regional alterations, global sagittal balance typically remains stable posttreatment, underscoring the body's inherent compensatory mechanisms to maintain an energy-efficient upright posture. Pelvic parameters exhibit considerable individual variability but adapt to help sustain overall spinal equilibrium, with a tendency toward retroversion when compensating for spinal imbalances. Clinical management of AIS should integrate personalized, three-dimensional assessment and correction strategies, balancing coronal correction with the imperative of achieving optimal sagittal alignment to ensure favorable long-term outcomes.