Nerve Root Sedimentation Sign: Can It Predict the Success for Surgical Intervention in Patients With Symptomatic Lumbar Spinal Stenosis?

INTRODUCTION: The use of interspinous process devices are less invasive surgical methods designed to manage mild to moderate lumbar spinal stenosis symptoms. Symptomatic relief may not be seen in all patients undergoing this procedure. Magnetic resonance imaging (MRI) parameters have been used to predict the success of clinical outcomes in patients with symptomatic lumbar spinal stenosis for decompressive surgeries. The purpose of this study was to determine the feasibility of using nerve root sedimentation sign to predict mid- to long-term clinical outcomes of patients treated with interspinous spacers for lumbar spinal stenosis. METHODS: This was a retrospective study using prospective multicenter Food and Drug Administration Investigational Device Exemption (FDA IDE) trial (Superion™ and X-STOP®) data. Inclusion criteria were patients treated with interspinous spacers, aged 45 or older with lumbar spinal stenosis at one or more contiguous levels from L1 to L5 and symptoms of neurogenic claudication. Preoperative axial T2 weighted MRI images were used to determine nerve root sedimentation sign. Preoperative, six-week, one- and two-year postoperative clinical outcomes were measured using Oswestry Disability Index (ODI) scores. Clinical outcomes were compared between positive and negative nerve root sedimentation sign groups; p ≤0.05 was considered significant. RESULTS: This study included n=374 patients; 40 excluded; 334 included (113=positive nerve root sedimentation sign (NRSS) (34%) and 221=negative NRSS (66%)). At six weeks, significant postoperative ODI correction was noted in both groups (p<0.001). No significant differences in ODI scores were identified between groups. A subgroup analysis with MRI image quality grade 3 and certainty determination grade 5, six-week postoperative ODI correction was significant in both groups. Six-week, one- and two-year postoperative ODI scores were greater by 6 points in the positive nerve root sedimentation sign group compared to the negative nerve root sedimentation sign group. CONCLUSIONS: Although satisfactory postoperative improvement occurred in both groups, there were statistically significant differences noted in certain sub-categories. The subgroup analysis indicated MRI image quality and nerve root sedimentation sign certainty of determination may be factors that may aid with planning the surgical management of lumbar spinal stenosis.