67. Relationship of PI-LL mismatch and early reoperation for adjacent segment disease after lumbar fusion

Abstract

<h3>BACKGROUND CONTEXT</h3> The incidence of symptomatic adjacent segment disease (ASD) following lumbar fusion surgery ranges from 0.6% to 3.9% per year. Sagittal malalignment may contribute to the development of ASD, particularly PI-LL mismatch, the difference between the pelvic incidence (PI) and lumbar lordosis (LL). Patients with a high degree of PI-LL mismatch (over 10°) have higher incidences of ASD following lumbar fusion. Previous studies have shown that high PI-LL results in more complex surgery and is associated with higher rates of ASD. However, the clinical impact of PI-LL mismatch requires further study. <h3>PURPOSE</h3> The purpose of this study is to compare the 2-year reoperation rates between patients with PI-LL mismatch postoperatively to patients with normal PI-LL measurements. We hypothesize that PI-LL mismatch causes sagittal imbalance leading to early ASD and reoperation. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study at a large, tertiary academic center. <h3>PATIENT SAMPLE</h3> This study included 219 patients undergoing elective 1- to 2-level lumbar fusion for degenerative conditions between 2016-2018. <h3>OUTCOME MEASURES</h3> Rates of early reoperation for ASD. <h3>METHODS</h3> Consecutive patients undergoing elective 1- to 2-level lumbar fusion for degenerative conditions between 2016-2018 were retrospectively reviewed. PI-LL mismatch was determined by age-adjusted thresholds defined by Lafage et al measured from immediate postoperative radiographs. Early reoperation rates were compared between the PI-LL mismatch cohort and normal PI-LL cohort. Early reoperation was defined as ASD requiring operative treatment within two years of the index lumbar fusion surgery. <h3>RESULTS</h3> Of the 219 patients enrolled, the average age was 59 years-old (59.8% female), and 76.7% underwent a single-level lumbar fusion. The mean follow-up was 3.21 years. The PI-LL mismatch (N=161) and normal PI-LL (N=58) cohorts were comparable over most demographics. However, the normal PI-LL cohort was older (p 65 years); sex, race, BMI >30, and smoking status did not significantly increase a patient's odds of early reoperation. <h3>CONCLUSIONS</h3> PI-LL mismatch was not associated with increased early reoperation rates for ASD in patients undergoing 1 -to 2-level lumbar fusions for degenerative conditions. Older age and higher BMI may be associated with early reoperation for ASD. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.