How Does the Lordosis Apex, Lordosis Arcs, and Inflection Point According to Roussouly Predict Outcomes After Adult Spinal Deformity Surgery?

After ASD surgery, most patients showed a cranial lordotic apex shift, with a greater increase in upper than lower arc vertebrae-highlighting the difficulty of restoring lordosis caudally. Cranial apex shift was associated with smaller L4-S1 lordosis and greater two-year back pain, while a preoperative inflection point outside T12/L1 increased the risk of spinopelvic complications. Incorporation of Roussouly principles may help spine surgeons improve outcomes and mitigate complications.