P107. Impact of upper instrumented vertebra and lordosis morphology on acute proximal junctional fracture following adult spinal deformity surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> Acute proximal junctional Fracture (PJF) is a challenging complication of adult spinal deformity (ASD) surgery. Upper instrumented vertebra (UIV) orientation has been proposed as a risk factor of acute PJF. Adjust UIV orientation by lordosis morphology during ASD surgery could reduce the occurrence of acute PJF. <h3>PURPOSE</h3> The purpose of this study is to analysis the effect of UIV orientation on acute PJF. And we tried to find out the relationship between UIV orientation and lordosis morphology. This strategy is thought to reduce acute PJF by adjusting lordosis morphology during surgery. <h3>STUDY DESIGN/SETTING</h3> A retrospective study. <h3>PATIENT SAMPLE</h3> A total of 187 patients (mean age 71.7 years) ASD patients underwent long-segment fusion from thoracolumbar vertebra to pelvis and followed up for more than 1 year. <h3>OUTCOME MEASURES</h3> Description and analysis of X-ray changes. <h3>METHODS</h3> Comparative analysis was performed on spinopelvic parameters including UIV parameters (UIV slope angle and horizontal distance from UIV center to C7 plumb line[C7PL]) between PJF and non-PJF group. And correlation analysis between UIV parameters and lordosis morphologic parameters (postoperative lumbar lordosis, lordosis correction degree, lordosis apical vertebra level and lordosis distribution index [LDI]) were performed. <h3>RESULTS</h3> Acute PJF incidence was 17.2% (32/187). PJF group had more UIV slope (20.6° vs 18.6°, p=0.045) and PJF group's UIV was located more posteriorly (-5.6mm vs +11.4mm, p<0.001). In condition that UIV slope was above 18.6° and UIV was located behind C7PL, acute PJF incidence was 75.0% (15/20). In condition that UIV slope was less than 18.6° and UIV was located in front of C7PL, acute PJF incidence was 1.9% (1/54). In correlation analysis, UIV slope had significant correlation with postoperative lumbar lordosis (r=0.422, p<0.01) and lordosis correction degree (r=0.239, p<0.05). And UIV-C7PL distance had significant negative correlation with apical vertebra level (r=-0.243, p<0.01) and LDI (r=-0.260, p<0.01). <h3>CONCLUSIONS</h3> UIV with large slope and located behind C7PL increases the risk of acute PJF occurrence. To avoid this situation while preserving sufficient lordosis correction, proper proximal rod contouring is needed to reduce UIV slope. And proper apical vertebra positioning and LDI lowering is needed to place UIV anteriorly. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.