Abstract Background Context The incidence of proximal junctional kyphosis (PJK) ranges from 5-46% following adult spinal deformity (ASD) surgery. Approximately 66-76% of PJK occurs within 3 months of surgery. A subset of these patients, reportedly 26-47%, develop proximal junctional failure (PJF) within 6 months postoperatively. To date, there are no studies evaluating the impact of prophylactic vertebroplasty on PJK/PJF incidence at long term follow-up. Purpose The purpose of this study is to evaluate the long term radiographic and clinical outcomes, and incidence of PJK and PJF, after prophylactic vertebroplasty for long segment thoracolumbar posterior spinal fusion. Study Design Prospective cohort study. Patient Sample 39 patients, of whom 87 % were female, who underwent two level prophylactic vertebroplasty at the upper instrumented and supra-adjacent vertebrae at the time of index PSF were included in this study. Outcome Measures Clinical outcomes were assessed using the Scoliosis Research Society-22, Short-Form (SF) 36, and ODI questionnaire. Radiographic parameters including PJK angle, and coronal and sagittal alignment, were calculated, along with relevant perioperative complications, and revision rates. Methods Of the 41 patients who received 2 level prophylactic vertebroplasty at the upper instrumented and supra-adjacent vertebrae at the time of index PSF, and compromised a cohort with previously published two year follow up data, 39 (95%) completed 5 yr follow-up (average 67.6 months). PJK was defined as a change in the PJK angle ≥10° between the immediate post-operative and final follow-up radiograph. PJF was defined as acute proximal junctional fracture, fixation failure, or kyphosis requiring extension of fusion within the first 6 months postoperatively. Results 39 patients with a mean age of 65.6 (41-87) years were included in this study. Of the 39 patients, 28.2% developed PJK (11: 7.7% at 2 yrs, 20.5% between 2 to 5 yrs), and 5.1% developed acute PJF. Two of the 11 PJK patients required revision for progressive worsening of the PJK. There were no proximal junctional fractures. There was no significant difference in preoperative, immediate postoperative, and final follow-up measurements of thoracic kyphosis, lumbar lordosis, coronal, or sagittal alignment between patients who developed PJK, PJF, or neither (P>0.05). There was no significant difference in ODI, SRS-22, or SF-36 scores between those with and without PJK or PJF (P>0.05). Conclusions This long term follow up demonstrates that prophylactic vertebroplasty may minimize the risk for junctional failure in the early postoperative period. However, it did not appear to decrease the incidence of PJK at 5 years.