properties of the procedure, ACR may increase the risk of MF, including proximal junctional kyphosis (PJK) and rod fracture (RF). However, this issue has been poorly documented in the literature. Methods. We included patients aged ≥60 years with severe DSI radiographically defined by pelvic incidence (PI)-lumbar lordosis (LL) ≥20° undergoing ≥5-level fusion, including the sacrum. PJK was defined radiographically as a proximal junctional angle (PJA) >28° plus Δ PJA of >22°. RF was evaluated at ACR levels performed. Clinical and radiographic variables were compared with identify the risk factors for PJK and RF, then multivariate analysis was performed by combining PJK and RF into a single composite outcome of MF. Results. We included a total of 147 patients in the final study cohort. The mean age was 70.3 years, and there were 126 women (90.6%). The median fusion length was 8 levels. After surgery, PI-LL was corrected from 48.1° to 4.3°. MF developed in 49 patients (33.3%); PJK in 41 (27