# Force-limited distance-measurable nerve root retractor plus intraoperative neurophysiological monitoring reduces L5 radiculitis in posterior lumbar interbody fusion

## TL;DR

Using a special nerve retractor and monitoring system during spine surgery reduced nerve inflammation and improved short-term recovery.

## Contribution

A force-limited nerve retractor combined with real-time monitoring reduces L5 radiculitis after lumbar fusion surgery.

## Key findings

- FLDM-NRR with IONM reduced 3-month L5 radiculitis incidence (7.29% vs 18.12%).
- The system showed better short-term functional outcomes and higher complication prediction accuracy.

## Abstract

To evaluate the incidence of L5 radiculitis in patients undergoing posterior lumbar interbody fusion (PLIF) using a force-limited distance-measurable nerve root retractor (FLDM-NRR) combined with intraoperative neurophysiological monitoring (IONM), compared with conventional nerve root retraction.

This retrospective cohort study examined 234 patients with L4-L5 lumbar spinal stenosis (LSS) undergoing single-level PLIF from January 2022 to March 2024. Patients were categorized into the FLDM-NRR plus IONM group (n = 96) with force limitation ≤ 3.5 N, and the conventional nerve root retraction group (n = 138). The primary outcome was 3-month L5 radiculitis; Secondary outcomes included 1-year persistent neurological impairment, Japanese Orthopedic Association (JOA) scores, Oswestry Disability Index (ODI), Visual Analog Scale (VAS) pain scores, and achievement of minimal clinically important difference (MCID). Multivariable logistic regression, mixed-effects models, and hierarchical testing were applied.

FLDM-NRR with IONM reduced the 3-month L5 radiculitis incidence (7.29% vs 18.12%, adjusted OR = 0.31, 95% CI 0.11–0.78; P = 0.017; absolute risk reduction (ARR) = 10.83%; number needed to treat (NNT) = 9), with greatest protection in the first postoperative week (3.13% vs 13.04%, P = 0.020). No significant difference was observed in 1-year persistent neurological impairment (3.13% vs 7.25% P = 0.200). The FLDM-NRR group showed superior ODI (18.43 ± 7.85% vs 21.17 ± 8.42%, P = 0.018) and higher MCID rates in VAS leg pain (95.8% vs 93.5%, P = 0.028). IONM demonstrated 85.71% sensitivity and 96.63% specificity in predicting postoperative complications. The FLDM-NRR system consistently upheld the predetermined force threshold in all instances without any device-related problems.

FLDM-NRR combined with IONM significantly reduces early L5 radiculitis after PLIF and provides short-term functional benefits. Long-term neuroprotection remains unproven and requires validation in prospective randomized trials.

The online version contains supplementary material available at 10.1186/s13018-025-06429-0.