A study on MRI findings and outcome in lumbar spinal stenosis patients from the NORDSTEN cohort

Abstract

Background: LSS is a clinical condition congruent with a narrowing of the spinal canal and consequently compression of neural and vascular structures at the affected level. The condition is estimated to be symptomatic in 103 million people worldwide (1). The regular symptoms includes neurogenic claudication, radiating pain and flection relief. Earlier studies proclaim good to excellent outcomes after surgery for LSS in the 60-80 % range, measured with commonly used PROMs (2, 3). Methods: We investigated preoperative MRI findings, patient symptoms and outcomes in patients with LSS. The included patients are from the NORwegian Degenerative spondylolisthesis and spinal STENosis (NORDSTEN) study, a large multicentre study evaluating clinical outcomes of different surgical treatment options for LSS. The NORDSTEN study consists of 3 arms: 1. Spinal stenosis trail (SST) 2. The degenerative spondylolisthesis trail (DST) 3. The observational trail (OC) The investigated cohort is from the NORDSTEN Spinal Stenosis Trial (SST), which included 437 LSS patients without spondylolisthesis eligible for surgery (4). In order to identify potential radiological predictors, we used multivariable regression models adjusted for patients’ gender, age, smoking status and weight/BMI. Patient reported outcome measures (PROMs) i.e. Oswestry Disability Index (ODI), Zurich Claudication Questionnaire (ZCQ) and Numeric rating scale (NRS) for back and leg pain were collected both before surgery and at 2-year follow-up. We dichotomised each radiological parameter into a non-to moderate/moderate or severe category. In the first paper, we investigated a broad range of MRI findings and potential associations with preoperative symptom severity in a crosssectional study design. In the second paper, we investigated MRI findings and their potential predicative effect on improving PROMs after surgery. In the third paper, we investigated the association between additional foraminal stenosis at level of LSS and outcome. Both paper 2 and 3 are observational cohort studies. Results: We detected no clinically relevant associations between preoperative MRI findings and symptom severity. When dichotomizing the ODI score with a cut-off value of minimum 30 % postoperative improvement, severe disc degeneration was associated with approximately half the chance of achieving the improvement goal. We also detected a sixfold chance of failing to achieve the targeted goal of ≥ 30 % improvement on ODI if severe foraminal stenosis was observed preoperatively. Conclusion: In the investigated cohort consisting of patients with symptomatic LSS there were no relevant association between MRI findings and symptom severity. Severe disc degeneration and severe foraminal stenosis were associated with less improvement after surgery.