140. C2 pelvic angle (C2PA) is a useful intraoperative radiographic parameter that correlates with the risk of developing proximal junctional kyphosis postoperatively

BACKGROUND CONTEXT We established the first intraoperative parameter that directly correlates with postoperative proximal junctional kyphosis (PJK). C2 pelvic angle (C2PA) is a novel, intraoperative radiographic parameter used to assess for potential development of PJK. Intraoperative C2PA >15° is a critical angle with 2.5 times the relative risk for developing PJK. No patient with intraoperative C2PA PURPOSE PJK is a postoperative complication of adult spinal deformity surgery that leads to poorer patient clinical outcomes. There is no literature on intraoperative assessment of sagittal alignment to prevent PJK. Intraoperative C2PA is a novel, radiographic parameter derived from the difference between global spinal alignment and the alignment proximal to the uninstrumented spine. The goal of this study is to demonstrate a positive relationship between the intraoperative C2PA and PJK. STUDY DESIGN/SETTING Prospectively collected cohorts. PATIENT SAMPLE Sixty deformity patients from 2015- 2018 who had preop, intraop, immediate postop and 2-year postop full length spine films. OUTCOME MEASURES Logistic regression and Chi-square analyses evaluated the relationship between the postop PJA and intraop C2PA/PJA. Methods We performed radiographic analysis on 60 deformity patients from 2015- 2018. Of the 60 patients, 35 were fused to the sacrum/pelvis. C2PA is defined as the angle between the posterior superior sacrum, C2 centroid and upper instrumented vertebrae (UIV) centroid and measured in the pre-, intra-, and postop setting (immediate and 2 years or prior to return to OR). PJK was defined as postop PJA >15°. Logistic regression and Chi-square analyses evaluated the relationship between the postop PJA and intraop C2PA/PJA. Results Of the 60 patients, 20 had PJK at the 2-year postop X-ray or prior to return to OR films. The intraop C2PA for the non-PJK and PJK group were 12.5° and 21.2°, respectively (p 15° was 2.43, and no one with intraop C2PA Conclusions This is the first intraoperative measurement that demonstrates a direct correlation with PJK. Intraoperative C2PA >15° is a critical angle with 2.5 times the relative risk for developing PJK. No patient with intraoperative C2PA FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.