Clinical Importance of Redundant Nerve Roots in Patients With Symptomatic Lumbar Spinal Stenosis: A Secondary Analysis of NORDSTEN Spinal Stenosis Trial Data

Abstract

Study design: Post hoc analysis of data from a randomized clinical trial.

Objective: To compare preoperative symptoms of patients with lumbar spinal stenosis with and without redundant nerve roots (RNRs), and to compare the change in clinical outcomes between those two groups 2 years after decompression surgery.

Background: RNRs are often seen on magnetic resonance imaging in patients with spinal stenosis. Previous studies have reported that patients with RNR are older and have worse symptoms at baseline. A meta-analysis from 2018 concluded that this radiologic sign could be seen as a negative predictor of outcome. High-quality prospective studies are lacking.

Patients and methods: Patient characteristics and reported pain and function scores were compared between lumbar spinal stenosis groups with (RNR+) and without RNR (RNR-) at baseline and after 2 years of follow-up. The primary outcome was the mean change in the Oswestry Disability Score (Oswestry Disability Index). Secondary outcomes included mean change in scores of the Zurich Claudication Questionnaire and the Numerical Rating Scale for leg and back pains.

Results: Out of 416 patients included in the present analysis, 163 (39%) had RNR at baseline. Both groups were similar in regard to patient age, smoking habits, Body Mass Index, and duration of symptoms. Both groups also showed similar pain and function scores at baseline. The RNR+ group contained a significantly higher proportion of men, patients with severe stenosis and multiple stenotic levels on magnetic resonance imaging. At a 2-year follow-up, the mean change of the Oswestry Disability Index was -22.1 in the RNR+ group and -17.4 in the RNR- group [mean difference: 4.7 (95% CI: 1.3 to 8.2); P = 0.007]. Statistically significant differences were also found for secondary outcomes Zurich Claudication Questionnaire, and Numerical Rating Scale leg and back pains favoring the RNR+ group.

Conclusion: Patients with RNR had similar baseline characteristics and similar symptoms as patients without. RNR before surgery was associated with better clinical improvement 2 years after decompression.

Keywords: Global Perceived Effect Scale; NORDSTEN spinal stenosis trial; Numerical Rating Scale; Oswestry Disability Index; Zurich Claudication Questionnaire; decompression; patient reported outcome measures; redundant nerve roots; spinal stenosis; spinal surgery.