Independent predictors of a clinically significant improvement after lumbar fusion surgery

Background Context

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.

Purpose

To determine medical, radiographic, and surgical predictors for obtaining a CSI following lumbar fusion surgery.

Study Design

This is a retrospective review of patients who underwent instrumented lumbar fusion.

Patient Sample

We included patients who underwent lumbar fusion for any indication between 2008 and 2013.

Outcome Measures

Outcome measures included preoperative and postoperative EQ-5D Index scores.

Materials and Methods

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.

Results

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.

Conclusions

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.