P42. CT measurement of pelvic incidence in the evaluation of spondylolisthesis

Abstract

<h3>BACKGROUND CONTEXT</h3> Pelvic incidence (PI) has been described as a parameter that may be a risk factor for lumbar spondylolisthesis. Studies have reported PI measurement is more precise in CT scans. Very limited studies have evaluated PI using CT scans in spondylolisthesis patients. <h3>PURPOSE</h3> Analyze the reliability of CT scans to measure PI in patients with spondylolisthesis compared to patients without spondylolistheses. <h3>STUDY DESIGN/SETTING</h3> Retrospective study from a single, academic center between 2013 and 2016 <h3>PATIENT SAMPLE</h3> A total of 361 patients who had pelvic/abdominal CT scans during an emergency room visit. <h3>OUTCOME MEASURES</h3> Analyze the reliability of CT scans to measure PI in patients with and without spondylolisthesis. <h3>METHODS</h3> The study included patients > 18 years and had no lumbar or pelvis fracture. We documented: age, average PI (right and left) and spondylolisthesis (type, grading and location). Left and right PI were determined on sagittal CT scans measuring the angle between the hip axis to an orthogonal line originating at the center of the superior end plate axis of the first sacral vertebra. Spondylolisthesis grading was determined on sagittal CT scans using Myerding Classification. An average PI (right and left) was calculated using both sides. We categorized patients with spondylolisthesis (n=45) and those without spondylolisthesis (n=316). Subgroups were comprised based on the location of the spondylolisthesis (L4/L5 and L5/S1) and the type of spondylolisthesis (isthmic or degenerative). An ANOVA test was used for continuous variables and Chi-square test for the categorical variables. P≤0.05 was considered as statistically significant. <h3>RESULTS</h3> There was no statistical difference in PI: between patients with and without spondylolisthesis (p=0.29); between subgroups of patients with spondylolisthesis at L4/L5 and without spondylolisthesis (p=0.52); between subgroups with type of spondylolisthesis at L4/L5 and without spondylolisthesis (p=0.47); and between spondylolisthesis patients at L5/S1 and without spondylolisthesis (p=0.40). Patients with isthmic spondylolisthesis at L5/S1 had nearly significant higher PI (p=0.06) compared to without spondylolisthesis and with degenerative spondylolisthesis at L5/S1. There was a trend towards higher PI in Grade 2 spondylolisthesis patients (L5/S1), p=0.18. <h3>CONCLUSIONS</h3> PI was significantly higher in patients with isthmic spondylolisthesis at L5/S1 and a trend toward increased PI with Grade 2 isthmic spondylolisthesis at L5/S1. Our reported PI correlated with PI reported in literature measured using standard radiographs in patients with spondylolisthesis. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.