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STUDY DESIGN Sequencing and experimental analysis of the expression profile of circular RNAs (circRNAs) in hypertrophic ligamentum flavum (LFH). OBJECTIVES The aim of this study was to identify differentially expressed circRNAs between LFH and nonhypertrophic ligamentum flavum tissues from lumbar spinal stenosis (LSS) patients. SUMMARY OF BACKGROUND DATA Hypertrophy of the ligamentum flavum (LF) can cause LSS. circRNAs are important in various diseases. However, no circRNA expression patterns related to LF hypertrophy have been reported. METHODS A total of 33 patients with LSS participated in this study. LF tissue samples were obtained when patients underwent decompressive laminectomy during surgery. The expression profile of circRNAs was analyzed by transcriptome high-throughput sequencing and validated with quantitative real-time polymerase chain reaction (PCR). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed for the differentially expressed circRNA-associated genes and related pathways. The connections between circRNAs and microRNAs were explored using Cytoscape. The role of hsa_circ_0052318 on LF cell fibrosis was assessed by analyzing the expression of collagen I and collagen III. RESULTS The results showed that 2439 circRNAs of 4025 were differentially expressed between the LFH and nonhypertrophic ligamentum flavum tissues, including 1276 upregulated and 1163 downregulated circRNAs. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that these differentially expressed circRNAs functioned in biological processes, cellular components, and molecular functions. Autophagy and mammalian target of rapamycin were the top two signaling pathways affected by these circRNAs. Five circRNAs (hsa_circ_0021604, hsa_circ_0025489, hsa_circ_0002599, hsa_circ_0052318, and hsa_circ_0003609) were confirmed by quantitative real-time PCR. The network indicated a strong relationship between circRNAs and miRNAs. Furthermore, hsa_circ_0052318 overexpression decreased mRNA and protein expression of collagen I and III in LF cells from LFH tissues. CONCLUSION This study identified circRNA expression profiles characteristic of hypertrophied LF in LSS patients, and demonstrated that hsa_circ_0052318 may play an important role in the pathogenesis of LF hypertrophy.Level of Evidence: N/A.

Study design Numerical techniques were used to study the vibration response of idiopathic scoliosis patients with single thoracic curve. Objective To analyze the dynamic characteristics of the idiopathic scoliotic spine under the whole-body vibration condition. The influence of the upper body mass was also studied. Summary of background data The relationship between the whole-body vibration and the spinal disorders has been investigated using finite element method. However, the dynamic response features of the scoliotic spine to the vibration were poorly understood. Methods The resonant frequencies of the scoliotic spine and the effects of the body weight were studied using a finite element model described previously. Modal and harmonic analysis was conducted. The amplitudes of 6 fundamental vertebral movements around the long, coronal and sagittal axis were quantified in the frequency range of 1 to 35 Hz. Results The vibration-induced rotation amplitudes of the apex of the thoracic deformity were higher than that of the lumbar segments. The apical vertebrae had the greatest rotation amplitudes at 2 and 8 Hz, and the largest lateral translation amplitudes at 16 Hz. Vibration could cause large lateral flexion amplitudes in the apex of the thoracic deformity. The apical vertebrae had the largest side flexion amplitudes at 6 Hz. Increasing upper body mass could not change resonant frequency of vibration-induced lateral translation and rotation around the long axis of the apical vertebrae. Conclusion The scoliotic spine is more sensitive to vibration than the normal spine. For a patient with single thoracic curve, long-term whole-body vibration may do more harm to the thoracic deformity than to the lower lumbar segments. Axial cyclic loads applied to an already deformed spine may cause further rotational and scoliotic deformity. The patients with idiopathic scoliosis are more likely to suffer from vibration-induced spinal disorders than those by normal persons.

STUDY DESIGN Retrospective radiographical study. OBJECTIVE To define the relationship between the grade of disc degeneration and the motion of the lumbar spine by using kinetic magnetic resonance imaging. SUMMARY OF BACKGROUND DATA Disc degeneration is common after middle age. Lumbar instability has generally been recognized as a potential risk factor of low back pain. However, correlations between the grade of disc degeneration and the motion of the lumbar spine need more investigation. METHODS Kinetic magnetic resonance imaging was performed in 162 patients with symptomatic low back pain without prior history of surgery. The lumbar intervertebral discs were graded by spine surgeons according to the degenerative grading system (grades I-V). Translational motion and angular variation were measured at each segment from L1-L2 through L5-S1. The relationship between the degree of lumbar disc degeneration and extent of lumbar spine mobility was analyzed. RESULTS The translational motion in discs with grade I through IV increased gradually, but decreased with grade V. Compared with other less degenerative grades, grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). The angular variation in discs with grade I through IV was fairly constant, but decreased with grade V. Compared with other degenerative grades (I-IV), grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). For less degenerative grades I and II discs, the L2-L3 and L3-L4 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, grade V discs, the contributions of the L2-L3 and L3-L4 significantly decreased (P < 0.01). CONCLUSION As disc degeneration developed from the normal to an increasingly severe stage, the motion of lumbar spine progressed from the normal stage to an unstable phase with higher mobility and finally to an ankylosed stage where stability was increased. LEVEL OF EVIDENCE 3.

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.