# Influence of Posterior Decompression for Lumbar Spinal Canal Stenosis on Intervertebral Disc Degeneration on Magnetic Resonance Imaging

## TL;DR

This study shows that lumbar spinal surgery causes short-term disc degeneration but does not lead to the need for further surgery.

## Contribution

The study provides new evidence that postoperative disc degeneration does not correlate with revision surgery needs.

## Key findings

- Posterior decompression surgery leads to significant short-term disc degeneration as shown by MRI parameters.
- Younger male patients were more likely to require revision surgery, but disc degeneration was not a contributing factor.
- Age and sex were identified as independent predictors for the need of revision surgery.

## Abstract

Introduction

Posterior decompression surgery for lumbar spinal canal stenosis (LSCS) is minimally invasive but may cause intervertebral instability and disc degeneration due to the removal of posterior support structures. This study aimed to evaluate the impact of decompression surgery on intervertebral disc degeneration using magnetic resonance imaging (MRI)-based signal ratio (SR) and disc ratio (DR) parameters.

Methods

Patients who underwent MRI three months to two years after decompression surgery for LSCS were included. Exclusion criteria included decompression at three or more levels, infections, and epidural hematomas. Sixty-three intervertebral discs from 51 patients were analyzed. SR was calculated as the ratio of the T2 signal intensity of the disc to that of the spinal cord, while DR compared the decompressed disc to the T12-L1 disc. Pre and postoperative SR and DR values were compared, and their associations with revision surgery were analyzed using multiple regression.

Results

Postoperative SR (0.402±0.225) and DR (0.642±0.299) were significantly lower than preoperative values (SR: 0.461±0.223, DR: 0.695±0.276; both p<0.05), indicating disc degeneration. Revision surgery occurred in 16 patients (31%), predominantly younger males. However, no significant association was found between MRI parameters and revision surgery. Regression analysis identified age (odds ratio: 0.889, p=0.014) and sex (female, odds ratio: 0.071, p=0.005) as independent factors for revision surgery. The revision surgery group had a younger mean age (67.2 ± 10.6 years) as compared to the control group (74.5 ± 7.4 years). Additionally, the proportion of males was higher in the revision surgery group (81.3%) than in the control group (45.7%).

Conclusions

Decompression surgery for LSCS resulted in short-term disc degeneration. Despite this progression, disc degeneration was not associated with the need for revision surgery. These findings suggest that early postoperative disc degeneration does not adversely affect the clinical course and therefore should not be regarded as a reason to avoid decompression surgery.