Defining clinically-relevant values for developmental spinal stenosis: a large scale MRI study

Abstract

INTRODUCTION: Developmental spinal stenosis is a precipitating factor in patients presenting with lumbar canal stenosis. Yet due to a lack of agreement on definitions and methods of assessment, as well as ethnic‐specific normative values, its prevalence and significance is not known. The aim of this study was to define lumbar spinal stenosis in a cohort of 100 surgical cases and 100 asymptomatic controls. METHODS: This was a case‐control study comparing 100 age and sex‐matched asymptomatic, volunteers to that of 100 patients who underwent surgery for spinal stenosis. All patients were of Chinese ethnicity and their details were blinded to two observers. Spinal stenosis parameters were measured based on axial (pedicle level) and sagittal (mid‐sagittal) MRI scans. RESULTS: Anteroposterior (AP) spinal canal diameters changes with levels. At each level, patients were found to have significantly narrower AP canal diameters compared with controls. By use of receiver operating characteristic (ROC) curve, we defined developmental spinal stenosis if the AP canal diameter at L1<20mm, L2<19mm, L3<19mm, L4<17mm, L5<16mm and at S1<16mm based on a value including 50% of controls and demonstrated best sensitivity and specificity. Furthermore, for L4, L5 and S1, critical stenosis values could be defined, below which almost all subjects needed surgery, these were 14mm for L4, 14mm for L5 and 12mm for S1. DISCUSSION: This is the largest MRI‐based study with standardized measurements and comparable groups to determine clinically-relevant radiographic criteria for lumbar spinal stenosis. The findings strongly suggest that developmental stenosis plays an important role in the pathogenesis of symptomatic spinal stenosis. Critical values of stenosis below which symptoms were highly likely were defined. These will need to be validated by longitudinal studies in future. However, they may possess clinical utility in determining the appropriate levels requiring canal‐widening surgery.