Immediate postoperative change in the UIV screw-vertebra angle is a predictor for PJK/PJF

BACKGROUND CONTEXT: Patients with posterior fusion of ≥3 vertebra levels and UIV at or distal to T8, and minimum 2-year follow-up were identified from a single center database (2018-2021). Primary outcomes were radiographic PJK/PJF or revision for PJK/PJF. Demographic, surgical and radiographic variables, including intraoperative screw-vertebra (SV) angle, change in SV angle, direction of UIV screw (cranial-neutral-caudal) and rod-vertebra (RV) angle were collected. Negative SV angles indicated cranially directed screws. PURPOSE: To determine if change in position of upper instrumented vertebral screw between intraoperative supine and immediate postoperative standing radiograph is a predictor for PJK/PJF. STUDY DESIGN/SETTING: Retrospective review. PATIENT SAMPLE: Patients with posterior fusion of ≥3 vertebra levels and UIV at or distal to T8, and minimum 2-year follow-up from a single center database. OUTCOME MEASURES: Proximal junctional kyphosis or failure. METHODS: Patients with posterior fusion of ≥3 vertebra levels and UIV at or distal to T8, and minimum 2-year follow-up were identified from a single center database (2018-2021). Primary outcomes were radiographic PJK/PJF or revision for PJK/PJF. Demographic, surgical and radiographic variables, including intraoperative screw-vertebra (SV) angle, change in SV angle, direction of UIV screw (cranial-neutral-caudal) and rod-vertebra (RV) angle were collected. Negative SV angles indicated cranially directed screws. RESULTS: A total of 143 patients were included with a mean age of 62.9 years and a follow-up of 3.5 years. Of these, 54 (38%) patients had developed PJK/PJF during follow-up, of whom 30 required a revision for PJK/PJF. Overall, 89 (62%) patients required revision (30 PJK/PJFs, 32 adjacent segment degenerations, 16 pseudarthroses, 5 infections, and 6 other reasons). Mean intraoperative SV angle was -0.8°±5.5° and postoperative was -3.0°±5.5°. Patients with PJK/PJF had a mean SV angle change of -2.5°±2.4 while the rest had a change of -1.0°±1.6 (p=0.010). When the change in SV angle was <5°, 33% of the patients developed PJK, but this dramatically increased to 80% when it was ≥5° (p=0.001). Revision for PJK/PJF also increased from 16% to 60% when SV angle changed ≥5° (p=0.001). Multivariate regression analysis showed only SV angle change as a significant risk factor for PJK/PJF (p=0.047, OR=1.58, 95%CI=1.00-2.47). It was also a risk factor for revision due to PJK/PJF (p=0.009, OR=2.21, 95%CI= 1.22-4.01). CONCLUSIONS: Change in the SV angle from intraop supine to immediate postop standing radiograph is a strong predictor for PJK/PJF and for revision. For each degree of SV angle change, odds of revision for PJK/PJF increases by 2.2x. A change of 5° should alert the surgeon to the likely development of PJK/PJF requiring revision. FDA Device/Drug Status: This abstract does not discuss or include any applicable devices or drugs.