<h3>BACKGROUND CONTEXT</h3> ASD is a complex pathology that benefits greatly from surgical treatment despite being associated with high rates of complications. Despite continuous innovation, little is known regarding the association between changes in surgical techniques and complications. <h3>PURPOSE</h3> To investigate the evolution of patient profiles and surgical complications across a single prospective multicenter database. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of prospective data. <h3>PATIENT SAMPLE</h3> This study included 947 adult spinal deformity patients surgically treated between 2008 and 2018. <h3>OUTCOME MEASURES</h3> Complication types and rates. <h3>METHODS</h3> Surgical ASD patients (TK >60°, SVA >5cm, PT >25° or Cobb angle >20°) with minimum 2-year follow-up were included and stratified into 3 equal groups by date of surgery. Demographic, preoperative data, surgical information, and complications were compared across time using a moving average of 316 patients to delineate those enrolled at the beginning of the study (Early) from the most recent one (Late). <h3>RESULTS</h3> Among the total, 947/1260 (67%) patients completed their 2-year follow-up with an enrollment rate of 7.7±4.1 patients per month. Compared to the Early phase (Oct 2008 and Nov 2012), patients enrolled more recently (Jan 2016 to Jan 2018) were older (Age: 56.7±15yovs 64.3±12.3), sicker (CCI: 1.46±1.6 vs 2.08±1.78), more disabled (ODI: 42.6±19.4 vs 45.7±15.3; PCS: 32.8±10.4 vs 29.7±8.5), with more pronounced sagittal deformity (SRS-Schwab type N: 26.3% vs 50.9%: PI-LL modifier ++: 37.1% vs 46.8%) (all p<0.05). Changes in surgical treatment included an increase use of IBF (61% vs 69.9%), more ACR/3CO use (21% vs 37%) and a decrease in 3CO rate (21% vs 12%), shorter fusion (11.2±4 vs 9.8±5), more supplemental rods (0.3% vs 26.9%) and BMP use (64.1% vs 80.1%) (all p<0.05), but no significant difference in invasiveness (91.2±37.1 vs 86.0±36.9 p=0.06). LOS decrease by 1 day, EBL by 500 cc and rate of ICU stay decrease from 71% to 53% (all p <0.001). There was no significant difference in overall complication rate (73% vs 67.4% p=0.14) despite a significant decrease in major complications requiring a reoperation (27.6% vs17.4% p=0.002) driven by a decrease in implant (8.3% vs 4.1% p=0.032) and radiographic failures (12.7% vs 5.7% p=0.002). Rate of major operative complication decreased (11.8% vs 6.7% p=0.028) while rate of major radiographic complication increased (0.6% vs 5.7% p<0.001) leading to a stable rate of major complications without reoperation (28.3% vs 27.9% p=0.92). No significant difference in minor complication rate (38.7% vs 34.2% p=0.24) The moving average analysis revealed a steady decrease in major complications associated to a reoperation (from 28% to 17%). The lowest peak of major complications (21%) occurred between Feb 2014 and Oct 2016, and the lowest overall complication rate (62%) occurred between July 2014 and Feb 2017. <h3>CONCLUSIONS</h3> Despite an increase in patient complexity including older, more medical morbidities and larger deformities, complication rates did not increase and the rate of complications requiring surgery decreased over time. These findings likely reflect evolutions in practice improvement including use of supplemental rods, PJK prophylaxis, BMP use, and targeting age-appropriate deformity corrections. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.