Independent predictors of a clinically significant improvement after lumbar fusion surgery.

Abstract

Multiple studies have determined minimum clinically important difference (MCID) thresholds for EuroQOL-5 Dimensions (EQ-5D) scores in lumbar fusion patients. However, a comprehensive understanding of predictors for a clinically significant improvement (CSI) postoperatively does not exist. To determine medical, radiographic, and surgical predictors for obtaining a CSI following lumbar fusion surgery. This is a retrospective review of patients who underwent instrumented lumbar fusion. We included patients who underwent lumbar fusion for any indication between 2008 and 2013. Outcome measures included preoperative and postoperative EQ-5D Index scores. The medical records of patients who received a lumbar fusion for any indication were retrospectively reviewed to identify patient medical and surgical characteristics. A blinded reviewer assessed radiographs for each patient to examine sagittal alignment following fusion. Multivariable logistic regression was used to model the achievement of a CSI based on two commonly cited MCID values. A total of 231 patients fit the inclusion criteria; 58% exceeded an MCID value for an EQ-5D score of 0.100, and 16% exceeded an MCID value of 0.390. Statistically significant independent predictors of not obtaining a CSI for an MCID threshold of 0.100 included a higher preoperative EQ-5D score (odds ratio [OR]=44.8) and L5-S1 fusion (OR=3.3). For an MCID value of 0.390, a higher preoperative EQ-5D score (OR=2,080.8) and a diagnosis of depression (OR=7.1) were predictive of not achieving a CSI, whereas spondylolisthesis (OR=4.1) was predictive of obtaining a CSI postoperatively. For both MCID values, patients who achieved a CSI had better postoperative quality of life (QOL) scores for all metrics measured, despite worse QOL scores preoperatively. This study is the first to use a combination of medical, surgical, and postoperative sagittal balance variables as determinants for the achievement of a CSI after lumbar fusion. The awareness of these predictors may allow for better patient selection and surgical approach to decrease the probability of acquiring a poor outcome postoperatively.