Study design: A kinematic magnetic resonance imaging study.
Objective: To investigate the distribution of Schmorl nodes (SNs) in the lumbar spine in healthy adults, and determine the association with lumbar disk degeneration and lumbar spine motion.
Summary of background data: SNs have been associated with several pathologies of the lumbar spine, although it has been demonstrated that they also occur in the healthy adult population without a clearly identified cause. A thorough understanding of SN distribution may help reveal reasons for their formation. How disk degeneration and lumbar spine motion relate to SNs is poorly understood.
Methods: Kinematic magnetic resonance images (0.6 T) were available for 1179 healthy individuals from 15 to 85 years of age. Spine specialists performed computer-based measurements. All parameters were measured and calculated automatically using the eRAD PACS Viewer (eRAD Inc., version 6.2.1.1). Lumbar disk degeneration was documented according to the Pfirrmann classification system. Lumbar spine lordosis was quantified as the angle between the inferior endplate of L1 and superior endplate of S1. The level of significance was defined as P ≤ 0.05. The distribution of SNs along the lumbar spine and their relationship with age and sex was investigated using the single factor analysis of variance χ test. The relationship between SNs, age group, disk location, and overall grades of lumbar disk degeneration were investigated by multiple logistic regression analysis. Lumbar spine motion was compared between patients with and without SNs via independent t test among 585 individuals with qualified kinematic images. Multiple logistic regression analysis was performed on associations of lumbar motion range among the SN population.
Results: The prevalence of SNs in our study population was 28.4%, and SNs were observed to be present more frequently in males (34.6%) than in females (20.2%) (ρ< 0.01). There was no significant difference in the incidence of SNs between age groups (ρ= 0.18). SNs were more common at the L2 and L3 vertebral bodies (14.3% and 14.4%), whereas SNs were least common at S1 vertebral bodies (1.5%). The highest incidences of SNs presentation was on disks with degeneration grade III (41.9%) and grade IV (45.3%). SN occurrence, aging, and disk location were positively correlated with lumbar disk degeneration grade. The lumbar spine range of motion was significantly different between individuals with and without SNs (31.4° vs. 37.9°, ρ< 0.01). The frequency of SNs was associated with decreased lumbar range of motion in all age groups except 51 to 60 years and 61 to 70 years.
Conclusion: SNs have a high incidence in individuals without persistent lumbar disorders and were found in disks at all degrees of degeneration. SNs occurrence were positively associated with lumbar disk degeneration In addition, the presence of SNs was correlated with decreased overall lumbar motion across all age groups.