INTRODUCTION: The importance of alignment on postoperative outcomes and mechanical complications has been well established. However, the impact of alignment parameters relative to thoracolumbar inflection point remains unclear. METHODS: ASD patients with 2-year data, fused in the lower-thoracic (T7-T12) to sacrum were included. Thoracolumbar inflection-point(IP), IP differences from UIV, LLA, and theoretical-IP based on Roussouly morphology were assessed. Cases were stratified based on IP changes from baseline (BL) into Caudal(L), Same(S), or Cranial(H). Analysis controlled for invasiveness, baseline deformity, frailty, and PJK prophylaxis. RESULTS: 650 patients met inclusion. PJF or PJK with reoperation was associated with a more caudal BL-IP (L2 inferior end plate (EP) vs L1-body, p < .001). In adjusted analysis, a more caudal BL IP had 25% higher odds of developing PJF by 2Y (OR:1.26, p=0.003). Postoperative normalization to theoretical Roussouly IP was associated with decreased rates of rod breakage (p = .049), but had higher rates of PJF (p = .044). Stratifying groups based on IP change from BL, rates of PJK and PJF by 2Y were higher in H (p < .003), with no difference in meeting Roussouly target IP. There was 4.4x lower odds of developing PJF in L and 2.0x in S compared to H (p < .05). Increased distance of UIV to IP was associated with mechanical-complications (MC) (p < .05). Decreased distance between LLA-IP at BL was associated with MC (p = .04). CONCLUSIONS: Despite lower frailty and baseline deformity in the cohort with a more cranially adjusted postoperative inflection point, there were higher rates of PJK and PJF. Increased distance between lumbar lordosis apex and inflection point was associated with higher rates of PJK, PJF, and thoracic decompensation. Correspondingly, a greater distance between the upper instrumented vertebra and inflection point was predictive of development of regional decompensation. The target inflection point can be an important parameter to minimize complications associated with ASD surgery.