Frailty, Bone Health, and Radiographic Predictors of Complications After Long-Segment Fusion for Adult Spinal Deformity

BACKGROUND: Surgery for adult spinal deformity (ASD) can result in complications such as proximal junctional kyphosis (PJK), pseudoarthrosis, hardware failure, and surgical site infection. This study sought to identify specific risk factors for these complications in ASD patients. METHODS: Patients undergoing long-segment thoracolumbar fusion (>4 levels) for ASD between 2016-2021 were included. Univariate and multivariable analyses assessed pre-operative risk factors for complications. A subgroup analysis of patients undergoing ≥7-level fusion constructs was also performed. RESULTS: Among 235 patients (66% female; mean age 70 years; mean BMI 28), higher BMI was associated with hardware failure (OR 1.087, 95% CI 1.023-1.157, p=0.007). Frailty measured by MFI-11 and DXA-defined bone health were not significantly associated with the studied complications. Lower preoperative sagittal vertical axis (SVA) was associated with higher pseudoarthrosis risk (OR 0.841, 95% CI 0.716-0.977, p=0.023). Smaller L3 vertebral surface area (OR 0.997, 95% CI 0.993-0.999, p=0.023), left L4 psoas area (OR 0.998, 95% CI 0.995-1.000, p=0.043), and L4 total psoas area (OR 0.998, 95% CI 0.997-1.000, p=0.015) were associated with increased PJK risk. Other radiographic measures were not significantly associated with complications. Findings were generally consistent in the ≥7-level fusion subgroup. CONCLUSION: In this single-center cohort, frailty, DXA-defined osteoporosis, and most radiographic alignment parameters were not significantly associated with postoperative complications, although these findings should be interpreted cautiously given limitations in frailty measurement, incomplete bone health assessment, and cohort power. BMI, sagittal alignment, and paraspinal muscle mass showed more consistent associations with adverse outcomes.