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 disc 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 disc degeneration. METHODS: Two independent observers assessed sagittal T2-weighted MRIs of the lumbar spine (N=2,449) 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 disc degeneration severity. RESULTS: Total 401 subjects with SN (16.4%) were included in the analysis. Hierarchical clustering showed Typical SN were usually smaller in size with shape Type 1 to 3 (i.e. indented endplate, sharp or rounded shape) whereas Atypical SN were larger with shape Type 4 to 5 (i.e. rectangular or irregular shape). 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 disc 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 disc degeneration, respectively (p < 0.05). CONCLUSIONS: This was the first study to address the relationships of SN morphology to the severity of disc degeneration. The associations of SN morphology with disc degeneration severity might be clinically relevant.