To analyze the differential transcriptome expression in hypertrophic ligaments flavum (HLF) compared to normal ligaments.
A case-control study was conducted that included 15 patients with hypertrophy of LF and 15 controls. Samples of LF were obtained through a lumbar laminectomy and analyzed by DNA microarrays and histology. The dysregulated biological processes, signaling pathways, and pathological markers in the HLF were identified using bioinformatics tools.
The HLF had notable histological alterations, including hyalinosis, leukocyte infiltration, and disarrangement of collagen fibers. Transcriptomic analysis showed that up-regulated genes were associated with the signaling pathways of Rho GTPases, receptor tyrosine kinases (RTK), fibroblast growth factors (FGF), WNT, vascular endothelial growth factor, phosphoinositide 3-kinase (PIK3), mitogen-activated protein kinases, and immune system. The genes PIK3R1, RHOA, RPS27A, CDC42, VAV1, and FGF5, 9, 18, and 19 were highlighted as crucial markers in HLF. The down-expressed genes in the HLF had associations with the metabolism of RNA and proteins.
Our results suggest that abnormal processes in hypertrophied LF are mediated by the interaction of the Rho GTPase, RTK, and PI3K pathways, which have not been previously described in the HLF, but for which there are currently therapeutic proposals. More studies are required to confirm the therapeutic potential of the pathways and mediators described in our results.

OBJECTIVE: Oblique lumbar interbody fusion (OLIF) involves inserting large cages into the interbody disc space. This expands the spinal canal and neural foramen by stretching the ligament flavum and releasing the facet joint, resulting in indirect neural decompression. Our objective was to investigate the changes in the spinal canal and ligament flavum over time after OLIF.
METHODS: This was a prospective observational study involving 30 patients who underwent OLIF L4-5 between 2015 and 2018. In total, 27 of the 30 patients underwent preoperative, early follow-up ( < 5 days), and late follow-up (10-14 months) magnetic resonance imaging to measure the area of the spinal canal and ligament flavum. Based on the results, the patients were divided into subsidence and nonsubsidence groups for further analysis.
RESULTS: After OLIF, the spinal canal area gradually increased during the preoperative, early postoperative, and late postoperative periods (p < 0.001). The thickness and area of the ligament flavum decreased gradually over the same periods (p < 0.001). Low-grade subsidence (2-4.4 mm) did not influence the effects on the spinal canal and ligament.
CONCLUSIONS: After OLIF, the spinal canal and ligament flavum gradually change, which is effective for indirect neural decompression. In addition, the effects of low-grade subsidence on the remodeling of the spinal canal and ligament flavum are insignificant.

Ligamentum flavum (LF) hypertrophy plays a dominant role in lumbar spinal stenosis (LSS). A previous study found that fibroblast growth factor 9 (FGF9) was upregulated with mechanical stress in rabbit LF. However, the expression and function of FGF9 are not well understood in human LF.
To evaluate FGF9 expression and function in human LF with and without hypertrophy.
This study employed a basic research study design utilizing human LF tissue for histological analyses.
Hypertrophied LF tissue sample from patients with LSS, and nonhypertrophied (control) LFs from patients with lumbar disc herniation or other diseases were obtained during surgery.
LF specimens were histologically analyzed for FGF9 and vascular endothelial growth factor A (VEGF-A) by immunohistochemistry. The number of total and FGF9 immuno-positive cells and blood vessels were counted and compared between LF with and without hypertrophy. For functional analysis, the effect of FGF9 on cell proliferation and migration was examined using a primary cell culture of human LF.
Histological studies revealed that the total cell number was significantly higher in the LF of patients with LSS than in the LF of control patients. Immunohistochemistry showed that the percentage of FGF9-positive cells was significantly higher in the LF of patients with LSS than in the controls, and it positively correlated with patients\' age, regardless of disease. Double immune-positive cells for FGF9 and VEGF-A were often observed in vascular endothelial cells and fibroblasts in the fibrotic area of hypertrophied LF, and the number of double positive vessels was significantly higher in LF of LSS patients than in the LF of controls. Primary cell culture of human LF revealed that FGF9 promoted the proliferation and migration of LF cells.
The present study demonstrated that FGF9 expression is highly upregulated in hypertrophied human LF. FGF9 potentially plays a pivotal role in the process of hypertrophy of LF, which is associated with mechanical stress, through cell proliferation and migration.
The results from this study partially reveal the molecular mechanisms of LF hypertrophy and suggest that FGF9 may be involved in the process of LF degeneration in elderly patients.

OBJECTIVE: A prospective, randomized, controlled clinical study was conducted with surgery performed by the same surgeon. The aim was to present a new technique for preserving the ligament flavum during lumbar microdiscectomy, and to evaluate whether this helps prevent postoperative fibrosis and improve outcome.
METHODS: From January to December 2017, 251 patients with indication for microdiscectomy were randomly divided into test group using ligament flavum preservation technique and control group using conventional procedures. Visual analogue scale (VAS) scores and Oswestry Disability Index (ODI) were assessed before the surgery, and 3 days, 1 month, 6 months, 1 year and 2 years after the operation respectively. The grade of epidural fibrosis on MRI after 6 months was evaluated by two radiologists independently and double-blindly.
RESULTS: Both groups\' VAS and ODI were significantly improved after surgery, but there was no significant difference between two groups at 3d and 1 month after operation. The grade of epidural fibrosis in test group was significantly lower than that in control group at 6 months postoperative. The VAS and ODI were significantly lower in test group than that in control group at 6 months,1 year and 2 years after operation.
CONCLUSIONS: Preservation of more ligament flavum is practicable during the procedure of microdiscectomy. It can prevent postoperative epidural fibrosis, and is helpful to achieve a better clinical outcome.