# Risk factors for early-onset adjacent segment degeneration after one-segment posterior lumbar interbody fusion

## TL;DR

This study identifies risk factors for early-onset degeneration at the spinal segment above a fused lumbar segment after surgery.

## Contribution

The study identifies preoperative bone marrow edema and surgical disc space distraction as novel risk factors for early-onset adjacent segment degeneration.

## Key findings

- Preoperative vertebral bone marrow edema at the cranial segment is a strong risk factor for early-onset ASD (odds ratio 16.8).
- Surgical disc space distraction of more than 4.0 mm is a significant independent risk factor for early-onset ASD.
- Bone marrow edema at the cranial segment is associated with a 57.1% rate of early-onset ASD.

## Abstract

Adjacent segment degeneration (ASD) is a major postoperative complication associated with posterior lumbar interbody fusion (PLIF). Early-onset ASD may differ pathologically from late-onset ASD. The aim of this study was to identify risk factors for early-onset ASD at the cranial segment occurring within 2 years after surgery. A retrospective study was performed for 170 patients with L4 degenerative spondylolisthesis who underwent one-segment PLIF. Of these patients, 20.6% had early-onset ASD at L3-4. In multivariate logistic regression analysis, preoperative larger % slip, vertebral bone marrow edema at the cranial segment on preoperative MRI (odds ratio 16.8), and surgical disc space distraction (cut-off 4.0 mm) were significant independent risk factors for early-onset ASD. Patients with preoperative imaging findings of bone marrow edema at the cranial segment had a 57.1% rate of early-onset ASD. A vacuum phenomenon and/or concomitant decompression at the cranial segment, the degree of surgical reduction of slippage, and lumbosacral spinal alignment were not risk factors for early-onset ASD. The need for fusion surgery requires careful consideration if vertebral bone marrow edema at the cranial segment adjacent to the fusion segment is detected on preoperative MRI, due to the negative impact of this edema on the incidence of early-onset ASD.