Is the morphology and size of Schmorl's nodes of the lumbar spine related to severity of disc degeneration?

Abstract

INTRODUCTION: We have recently confirmed that the presence of Schmorl's nodes (SN) was highly associated with disk degeneration in a large population-based cohort study in Southern Chinese. Based on our previous proposed classification system of SN, we attempt to further address the association of SN characteristics and the severity of disk degeneration. MATERIALS AND METHODS: Two independent observers assessed sagittal T2-weighted MRIs of the lumbar spine (n = 2449) for the presence and characteristics of SN, and additional radiologic features. The patterns of SN characteristics were assessed by hierarchical clustering methods. Generalized linear models were used to assess the associations of the shape and size of SN with disk degeneration severity. RESULTS: Total 401 subjects with SN (16.4%) were included in the analysis. Hierarchical clustering showed that typical SN were usually smaller in size with shape type I to III (i.e., indented endplate, sharp or rounded shape) whereas atypical SN were larger with shape type IV to V (i.e., rectangular or irregular shape). Total 8.3% of all identified SN (n = 960) were atypical SN. Multivariate ordinal logistic regression adjusted for gender, age, body mass index, smoking status, presence of disk bulge/extrusion, and high intensity zone showed that atypical SN and typical SN, depending on the lumbar levels, were associated with 5- to 13-fold and 2- to 4-fold higher risk of increased severity of disk degeneration, respectively (p < 0.05). CONCLUSION: This was the first study to address the relationships of SN morphology to the severity of disk degeneration. The associations of SN morphology with disk degeneration severity might be clinically relevant.