INTRODUCTION: Radiological stenosis is assessed commonly by measuring dural sac cross sectional area (DSCA). Great variation is observed though in surfaces recorded between symptomatic and symptomatic individuals. Our aim was to devise a qualitative grading of lumbar spinal stenosis (LSS), study its reliability and clinical relevance.
METHODS: This was a retrospective radiological study on a prospective patient cohort. We describe a seven grade classification based on the morphology of the dural sac as observed on T2 axial MRI images based on the rootlet / cerebrospinal fluid (CSF) ratio. Grades A and B show CSF presence while grades C and D show none at all. The grading was applied to MRIs of 95 subjects divided in three groups: 37 symptomatic LSS surgically treated patients; 31 symptomatic LSS conservatively treated patients (average follow up 2.5 and 3.1 years) and 27 low back pain (LBP) sufferers. DSCA was also digitally measured. We studied intra‐ and inter‐observer reliability, distribution of grades, relation between morphological grading and DSCA, as well relation between grades, DSCA and Oswestry Disability Index (ODI).
RESULTS: Average intra‐and inter observer agreement were substantial and moderate respectively (k = 0.65. and 0.44) whereas they were substantial for physicians working in the study originating unit. Surgical patients had the smallest DSCA. A larger proportion of C and D grades were observed in the surgical group. Surface measurements resulted in over‐diagnosis of stenosis in 35 patients and under diagnosis in 12. No relation could be found between stenosis grade or DSCA and baseline ODI or surgical result. Patients with C and D grades were more likely to fail conservative treatment.
DISCUSSION: The grading defines stenosis in different subjects than surface measurements alone. Since it mainly considers impingement of neural tissue it might be a more appropriate clinical and research tool than surface measurements alone.