Imaging profile of subjects with lumbar developmental spinal stenosis in a population-based cohort

Abstract

Introduction: Developmental spinal stenosis (DSS) occurs when there is narrowing of spinal canal due to maldevelopment of posterior elements relating to genetic disturbance during fetal and postnatal period. Lumbar DSS is of clinical significance as the pre-existing narrowed vertebral canal predisposes patients to experiencing neural compression at a lower threshold, as well as symptoms being presented even with milder degree of degenerative changes of the lumbosacral spine. Current knowledge of DSS mainly lies at the level-specific radiographic definition of the smaller canal size, the relationships between the presence of DSS and different spinal tissues remain unknown. This study aims to determine the differences of spinal imagining phenotypes between subjects with lumbar DSS and those without DSS in a population-based cohort. Materials and Methods: This was a radiological analysis of 2387 subjects who underwent L1-S1 magnetic resonance imaging (MRI) in the population-based disc degeneration cohort. Data collection included patient’s age, gender, body mass index and MRI measurements. Differentiation of cases of lumbar DSS from non-DSS was based on the anteroposterior (AP) vertebral canal diameters. The measurement of other imaging parameters included the vertebral body dimensions, spinal canal dimensions, disc degeneration scores and facet joint orientation. Mann-Whitney U and chi-square tests were used to assess for any differences of these parameters between DSS and non-DSS subjects. To identify possible associations between the presence of DSS and various MRI parameters, univariate and multivariate regression analyses were conducted with adjustment for subject demographics. Results: Axial AP vertebral canal diameter, interpedicular distance, AP dural sac diameter, lamina angle and sagittal mid-vertebral body height were significantly different between lumbar DSS and non-DSS subjects (all at P < .05). Lamina angle (OR: 1.127; P = .002) was associated with the presence of lumbar DSS. Narrower interpedicular distance (OR: 0.745, P = .002) and AP dural sac diameter (OR: 0.506, P < .001) as well as right facet joint angulation (OR: 0.022; P = .002) were also associated with lumbar DSS. No association was observed between disc parameters and DSS. Conclusion: In this large-scale cohort, the vertebral canal size is found to be independent of subject body habitus and vertebral body dimensions. A more obtuse lamina angle and smaller dural sac are found associated with the presence of DSS at the lumbosacral spine, whereas no associations between DSS and disc and endplate parameters such as disc herniation, disc degeneration, Schmorl’s notes, endplate irregularity. Other than spinal canal dimensions, abnormal orientations of lamina angle and facet joint angulation may be a result of developmental variations, leading to increased likelihood of DSS. Other skeletal parameters are spared. The lack of relationship between DSS and soft tissue changes of the spinal column suggested DSS is purely a result of bony maldevelopment.