# Comparison of Three Evaluation Methods for the Lumbar Intervertebral Disc Vacuum Phenomenon in Predicting Postoperative Residual Lower Back Pain

## TL;DR

This study compares three methods for evaluating the lumbar disc vacuum phenomenon to see which best predicts ongoing back pain after spine surgery.

## Contribution

The study introduces a modified classification for vacuum phenomenon severity and compares its predictive value with existing methods.

## Key findings

- All three VP evaluation methods showed significant differences in predicting residual back pain.
- The modified Willhuber’s classification (SVP2) had the highest predictive accuracy, though not significantly different from others.
- All VP scores remained significant predictors of residual LBP in multivariable analyses.

## Abstract

Introduction: The lumbar intervertebral disc vacuum phenomenon (VP) is an important imaging finding commonly seen in patients with lumbar degenerative disease (LDD). It is closely associated with low back pain (LBP) and surgical outcomes after spine surgery. This study aims to compare different evaluation methods of VP to determine which method best predicts postoperative residual LBP after single-level transforaminal lumbar interbody fusion (TLIF) for LDD.

Methods: Overall, 66 patients (67.8 ± 10.2 years; 36 male/30 female) with LDD treated by single-level TLIF, who showed preoperative LBP, were enrolled in this study. The severity of VP (SVP) score was evaluated by three methods: SVP1 score, Willhuber’s classification; SVP2 score, a modified classification excluding subchondral sclerosis; and SVP3 score, presence/absence of VP. Clinical outcomes were assessed. Patients were divided into the residual LBP group (R group) and the control group (C group) by postoperative visual analogue scale (VAS) for LBP. Logistic regression analyses (both univariate and multivariable adjusted for age, sex, body mass index, lumbar lordosis, and pelvic incidence minus lumbar lordosis) were performed with the presence of residual LBP as the dependent variable and each SVP score as an independent variable. Receiver operating characteristic (ROC) curves and the area under the curve (AUC) were used to evaluate predictive ability, and DeLong’s test was used to compare AUCs.

Results: Each SVP score was significantly greater in the R group than in the C group. There were no significant differences in preoperative clinical outcomes. The AUCs of SVP1, SVP2, and SVP3 were 0.789, 0.802, and 0.788, respectively. Although SVP2 had the largest AUC, DeLong’s test showed no statistically significant differences among the three methods. In multivariable analyses, all SVP scores remained significant predictors of residual LBP.

Conclusion: Evaluation of VP severity based on VP size (modified Willhuber’s classification, SVP2) demonstrated the highest numerical predictive accuracy for postoperative residual LBP, but differences compared with other methods were not statistically significant. SVP scoring may serve as a useful preoperative tool.