• Michael E Steinhaus, Renaud Lafage, Ram K Alluri, Francis Lovecchio, Nicholas J Clark, Ahilan Sivaganesan, Frank Schwab, Virginie Lafage, and Han Jo Kim.
• Spine Service, Department of Orthopedic Surgery, Hospital for Special Surgery, New York, NY.
• Spine. 2022 Jun 1; 47 (11): 800-807.

Study DesignRetrospective cohort study.ObjectivesThe aim of this study was to examine sagittal alignment over time in adult spinal deformity (ASD) and to understand whether these changes vary by choice of upper instrumented vertebra (UIV).Summary Of Background DataRecent ASD literature has focused on specific alignment goals. Less is known about how sagittal parameters evolve over time after surgical correction and whether these changes differ by choice of UIV.MethodsThis was a retrospective review of ASD patients from a single institution. Routine 36″ sagittal x-rays were obtained preoperatively, before hospital discharge, and at 6 months, 1 year, and 2 years and sagittal parameters were measured. Patients with UIV T6 and above were classified as upper thoracic (UT) and T7 and below as lower thoracic (LT).ResultsA total of 102 patients with mean age 66.0 years (±7.7) were included in the analysis (49 UT, 53 LT). All sagittal and coronal alignment parameters demonstrated significant improvement from preoperatively to any postoperative time point. Although multiple parameters maintained correction over time, others (TK, TPA, and PT) demonstrated significant increase from discharge to 2 years postoperatively, with changes occurring relatively early after surgery, whereas overall global alignment was maintained. Both UT/LT groups demonstrated significantly greater TK from preoperatively to discharge to 6 months (P  < 0.05), stabilizing at that time point out to 2 years, whereas TLK preferentially increased in the LT group. There was significant improvement in sagittal vertical axis after surgery, which was maintained out to 2years of follow-up (P > 0.05).ConclusionsOur data suggest that although several key parameters are maintained over time out to 2years postopera- tively, TK tends to worsen over time for all patients, whereas TLK preferentially increases in the LT group. Nevertheless, despite these trends, compensatory changes are seen in PT such that global alignment is relatively maintained.Level of Evidence: 3.Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

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