Distribution of mechanical properties of native human ligamentum flavum depending on histopathological changes.

This study aimed to characterize the mechanical properties of native human ligamentum flavum (LF) and correlate them with histopathological changes. Mechanical property gradients across the cranial, medial, and caudal regions of LF were mapped and compared with histological sections. We also compared lumbar spinal stenosis (LSS) samples with disc herniation (DH) samples as reference material to identify differences in mechanical properties and histopathological features. Our results revealed significant heterogeneity in LF mechanical properties, with local variations correlating with specific histopathological changes such as chondroid metaplasia and loss of elastic fibers. These findings underscore the importance of considering LF heterogeneity in mechanical characterization and provide insights into its behavior under pathological conditions.

Analyses of imaging presentations, full endoscopic and pathological features of a novel interlaminar ligament.

BACKGROUND: To analyze the characteristics of an unnamed interlaminar ligaments(ILL) through magnetic resonance image (MRI), endoscopy and pathological examination. METHOD: A retrospective study was conducted to analyze the clinical data of patients who underwent posterior endoscopic surgery for lumbar disc herniation or lumbar spinal stenosis from January 2021 to February 2022 at our medical center. The height, width and cross-sectional thickness of the ligament was analyzed using T2 weighted MRI. Meanwhile, the morphological and pathological characteristics were also compared with those of the ligamentum flavum to highlight the differences between above mentioned ligaments. RESULT: Forty-three patients were included in this study, including 27 males and 16 females, with an average age of 46.6 ± 12.1y. There were 20 cases of lumbar disc herniation and 23 cases of lumbar spinal stenosis. The width, length, thickness of the ILL, the thickness of LF and surgical time in the lumbar disc group were 17.7 ± 3.5 mm, 4.3 ± 1.3 mm, 18.3 ± 3.5 mm, 5.3 ± 1.9 mm, 53.2 ± 14.5 min, respectively. In the lumbar spinal stenosis group, the corresponding parameters were 16.0 ± 3.1 mm, 4.1 ± 1.6 mm, 17.6 ± 4.8 mm, 6.3 ± 0.8 mm, 61.8 ± 12.4 min, respectively. The intergroup difference in thickness of the ligamentum flavum was statistically significant (P = 0.02). The difference in surgical time was also established(P = 0.04). Endoscopic differences were identified as to the location of the anchor points and appearances among the two ligaments. Significant differences in the density and direction of fibrous structures were also observed under biopsy. Under endoscopy, significant difference as to the grade of ILL thickness was established when compared regarding disease spectrum (P = 0.09.) CONCLUSION: The interlaminar ligament is a structure that has not yet been officially named, which has significant structural differences from those of the ligamentum flavum. For posterior endoscopic procedure, its clinical significance lies in its ability to serve as the endpoint of soft tissue channel establishment. The thickness of the ligamentum flavum in MRI and the thickness of ILL under endoscopy vary according to the disease spectrum.

RMRP accelerates ligamentum flavum hypertrophy by regulating GSDMD-mediated pyroptosis through Gli1 SUMOylation.

Hypertrophy of ligamentum flavum (LF) is a significant contributing factor to lumbar spinal canal stenosis (LSCS). lncRNA plays a vital role in organ fibrosis, but its role in LF fibrosis remains unclear. Our previous findings have demonstrated that Hedgehog-Gli1 signaling is a critical driver leading to LF hypertrophy. Through the RIP experiment, our group found lnc-RMRP was physically associated with Gli1 and exhibited enrichment in Gli1-activated LF cells. Histological studies revealed elevated expression of RMRP in hypertrophic LF. In vitro experiments further confirmed that RMRP promoted Gli1 SUMO modification and nucleus transfer. Mechanistically, RMRP induced GSDMD-mediated pyroptosis, proinflammatory activation, and collagen expression through the Hedgehog pathway. Notably, the mechanical stress-induced hypertrophy of LF in rabbit exhibited analogous pathological changes of LF fibrosis occurred in human and showed enhanced levels of collagen and α-SMA. Knockdown of RMRP resulted in the decreased expression of fibrosis and pyroptosis-related proteins, ultimately ameliorating fibrosis. The above data concluded that RMRP exerts a crucial role in regulating GSDMD-mediated pyroptosis of LF cells via Gli1 SUMOylation, thus indicating that targeting RMRP could serve as a potential and effective therapeutic strategy for LF hypertrophy and fibrosis.

Nonsurgical therapy for lumbar spinal stenosis caused by ligamentum flavum hypertrophy: A review.

Lumbar spinal stenosis (LSS) can cause a range of cauda equina symptoms, including lower back and leg pain, numbness, and intermittent claudication. This disease affects approximately 103 million people worldwide, particularly the elderly, and can seriously compromise their health and well-being. Ligamentum flavum hypertrophy (LFH) is one of the main contributing factors to this disease. Surgical treatment is currently recommended for LSS caused by LFH. For patients who do not meet the criteria for surgery, symptom relief can be achieved by using oral nonsteroidal anti-inflammatory drugs (NSAIDs) and epidural steroid injections. Exercise therapy and needle knife can also help to reduce the effects of mechanical stress. However, the effectiveness of these methods varies, and targeting the delay in LF hypertrophy is challenging. Therefore, further research and development of new drugs is necessary to address this issue. Several new drugs, including cyclopamine and N-acetyl-l-cysteine, are currently undergoing testing and may serve as new treatments for LSS caused by LFH.

Cysts of the ligamentum flavum are often linked to ischemic conditions: A morphological study.

"Cysts of the ligamentum flavum (cysts-LF)" is the term for non-neoplastic cystic lesion involving LF. The aim of the present study was to elucidate the histopathological characteristics and pathogenesis of "cysts-LF". Herein, we defined cysts-LF as spinal cysts containing degenerative LF components. From archival cases, we investigated 18 symptomatic cysts-LF surgically removed from 18 patients (13 males and five females; median age 68.5 years [range, 42-86 years]). The elastic fibers of LF components in the wall were separated and/or torn, and cyst walls were accompanied by chondroid metaplasia (17 cases), myxoid changes (13 cases), ossification (11 cases), amyloid deposits (14 cases), hemosiderosis (six cases), granular/smudgy calcification (four cases), synovial cell linings (three cases), and severe inflammatory infiltrates (one case). These histologic features of our cysts-LF were shared by previously reported "cysts-LF." Fourteen cysts-LF demonstrated vascular stenosis/occlusion, and eight showed thick hyalinized vessels, suggesting local circulatory insufficiency. Eight cases (44%) exhibited lipomembranous fat necrosis, accompanied by hyalinized vascular changes (p = 0.003). Ischemic conditions were observed in nearly half of the present cysts-LF, and may be one of the main contributing factors for the formation of cysts-LF, via degeneration and cystic changes in the LF.

Evaluation of differences in expression pattern of three isoforms of the transforming growth factor beta in patients with lumbosacral stenosis.

The study investigates molecular changes in the lumbosacral (L/S) spine's yellow ligamentum flavum during degenerative stenosis, focusing on the role of transforming growth factor beta 1-3 (TGF-ß-1-3). Sixty patients with degenerative stenosis and sixty control participants underwent molecular analysis using real-time quantitative reverse transcription reaction technique (RTqPCR), enzyme-linked immunosorbent assay (ELISA), Western blot, and immunohistochemical analysis (IHC). At the mRNA level, study samples showed reduced expression of TGF-ß-1 and TGF-ß-3, while TGF-ß-2 increased by only 4%. Conversely, at the protein level, the study group exhibited significantly higher concentrations of TGF-ß-1, TGF-ß-2, and TGF-ß-3 compared to controls. On the other hand, at the protein level, a statistically significant higher concentration of TGF-ß-1 was observed (2139.33 pg/mL ± 2593.72 pg/mL vs. 252.45 pg/mL ± 83.89 pg/mL; p < 0.0001), TGF-ß-2 (3104.34 pg/mL ± 1192.74 pg/mL vs. 258.86 pg/mL ± 82.98 pg/mL; p < 0.0001), TGF-ß-3 (512.75 pg/mL ± 107.36 pg/mL vs. 55.06 pg/mL ± 9.83 pg/mL, p < 0.0001) in yellow ligaments obtained from patients of the study group compared to control samples. The study did not establish a significant correlation between TGF-ß-1-3 concentrations and pain severity. The findings suggest that molecular therapy aimed at restoring the normal expression pattern of TGF-ß-1-3 could be a promising strategy for treating degenerative stenosis of the L/S spine. The study underscores the potential therapeutic significance of addressing molecular changes at the TGF-ß isoforms level for better understanding and managing degenerative spinal conditions.

Incremental regression of localization context for automatic segmentation of ossified ligamentum flavum from CT data.

PURPOSE: Segmentation of ossified ligamentum flavum (OLF) plays a crucial role in developing computer-assisted, image-guided systems for decompressive thoracic laminectomy. Manual segmentation is time-consuming, tedious, and label-intensive. It also suffers from inter- and intra-observer variability. Automatic segmentation is highly desired. METHODS: A two-stage, localization context-aware framework is developed for automatic segmentation of ossified ligamentum flavum. In the first stage, localization heatmaps of OLFs are obtained via incremental regression. In the second stage, the obtained heatmaps are then treated as the localization context for a segmentation U-Net. Our framework can directly map a whole volumetic data to its volume-wise labels. RESULTS: We designed and conducted comprehensive experiments on datasets of 100 patients to evaluate the performance of the proposed method. Our method achieved an average Dice similarity coefficient of 61.2 ± 7.6%, an average surface distance of 1.1 ± 0.5 mm, and an average positive predictive value of 62.0 ± 12.8%. CONCLUSION: To the best knowledge of the authors, this is the first study aiming for automatic segmentation of ossified ligamentum flavum. Results from the comprehensive experiments demonstrate the superior performance of the proposed method over the state-of-the-art methods.

Increased matrix metalloproteinase-2 in ligamentum flavum hypertrophy and the regulation of MMP-2/TIMPs by elastin-derived peptides.

The study aimed to examine matrix metalloproteinase-2 (MMP-2) expression in a rat ligamentum flavum (LF) hypertrophy model in vivo, and the effect of elastin-derived peptides (EDPs) on MMP-2 and tissue inhibitors of metalloproteinases (TIMPs) in rat LF cells in vitro. Surgical destabilization was performed at the rat spinal L3/4 level to induce increased mechanical stress. Rats were killed at 6- and 12-weeks postsurgery for histological staining, immunohistochemical staining, RT-qPCR and western blot. 100 µg/mL EDPs were applied to isolated normal rat LF cells, with or without pretreatment of elastin receptor complex (ERC) inhibitors, to assess the expression of MMP-2, TIMP-1, and TIMP-2. Spinal destabilization led to LF hypertrophy, observed through increased LF thickness and area, along with histological changes of chondrometaplasia and elastic fiber degradation. LF was also stained positively for Col I and Col II, where elastic fiber has broken down. MMP-2 expression was notably elevated in the hypertrophied LF, accompanied by increased TIMP-2 and TIMP-3 levels. EDPs were found to suppress MMP-2 expression and reduce TIMP-1 and TIMP-2 levels in rat LF cells. Interestingly, exposure to EDPs led to a significant rise in MMP-2/TIMP-1 and MMP-2/TIMP-2 ratios, dependent on the ERC. Collectively, the study suggests that increased MMP-2 activity contributes to elastic fiber degradation in hypertrophied LF, generating EDPs that further enhance the MMP-2/TIMPs ratio in LF cells in an ERC-dependent manner. Further research is essential to delve into the mechanisms of EDPs in LF hypertrophy.

Differences in the Demographics and Clinical Characteristics between the Ossification of the Posterior Longitudinal Ligament and Ossification of the Ligamentum Flavum in Patients Who Underwent Thoracic Spinal Surgery for Compressive Myelopathy.

Ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) are related diseases associated with the ossification of spinal ligaments that can occasionally lead to thoracic myelopathy. We retrospectively analyzed the clinical data of 34 consecutive patients who underwent thoracic spinal surgeries for OPLL and/or OLF at our hospital between July 2010 and June 2022, and statistically compared data between patients with thoracic OPLL (TOPLL; n = 12) and those with thoracic OLF (TOLF; n = 22). The mean age of the TOPLL group was significantly lower than that of the TOLF group (53.7 vs. 68.4 years). The TOPLL group exhibited a greater female predominance than the TOLF group (58.3% vs. 18.2%). The median body mass index of the TOPLL group was significantly higher than that of the TOLF group (33.0 vs. 26.0 kg/m2). Patients with TOPLL significantly required instrumented fusion and repetitive surgical intervention more than those with TOLF (83.3% vs. 9.1%; 50.0% vs. 0.0%). Although neurological deterioration just after the intervention was more common in patients with TOPLL (41.7% vs. 4.6%), no difference was observed in thoracic Japanese Orthopaedic Association score and recovery rate in the chronic phase between TOPLL and TOLF. The TOPLL group had a younger onset, female dominance, and a greater degree of obesity when compared with the TOLF group. The surgery for TOPLL is challenging, considering that it requires long-range decompression and fusion, subsequent operations, careful management, and long-term follow-up, when compared to TOLF, which necessitates only simple decompression.

Safety and Efficacy Outcomes Following Spinal Endoscopic Procedures for Thoracic Ligamentous Ossification: A Systematic Review and Meta-Analysis.

STUDY DESIGN: A systematic review and meta-analysis. OBJECTIVE: This study systematically reviewed and evaluated the safety and efficacy of spinal endoscopic techniques as a treatment for thoracic ligamentum flavum ossification (TOLF). SUMMARY OF BACKGROUND DATA: The use of spinal endoscopic techniques for the treatment of TOLF has increased in recent years. The present study is the first comprehensive systematic review and meta-analysis focused on the use of spinal endoscopic techniques for TOLF. MATERIALS AND METHODS: The Cochrane Central, PubMed, Web of Science, and Embase databases were systematically searched for studies focused on patients undergoing spinal endoscopic techniques to treat symptomatic TOLF. RESULTS: This meta-analysis included 23 studies. We included 323 patients (177 males, 146 females) with a mean age of 58.40±10.06 years, with 304 total recorded lesion locations of which 245 were located in the lower thoracic spine. Complications affected 35/323 patients, and the mean operative duration for 305 patients was 108.15±47.34 minutes. For 187 patients, the mean operative bleeding was 25.13±12.54 mL, while for 87 patients the mean duration of hospitalization was 4.59±1.93 days. At last follow-up, functional assessment was performed for 260 patients, of whom 200 were in excellent condition, visual analog scale (VAS) scores were assessed for 160 patients, with a mean improvement of 4.40 (3.95, 4.86) Japanese Orthopedic Association (JOA) scores were recorded for 115 patients, with a mean improvement of 3.49 (2.79,4.18), and modified Japanese Orthopedic Association (mJOA) scores were recorded for 208 patients, with a mean improvement of 3.62 (2.89,4.35). CONCLUSIONS: These results support several advantages of spinal endoscopic techniques for the treatment of symptomatic TOLF. These include low complication rates, rapid postoperative recovery, and good functional recovery when used for single-segment, non-nodular ossification and no combined dural ossification.

Quantitative evaluation of the lumbar ligamentum flavum using MRI T2-mapping: Efficacy of its clinical application in patients with lumbar spinal stenosis.

OBEJECTIVE: To perform a magnetic resonance imaging T2-mapping of the ligamentum flavum in healthy individuals and patients with lumbar spinal stenosis scheduled for surgery and compare the T2 relaxation times. SUBJECTS AND METHODS: The T2 relaxation time of the ligamentum flavum was compared among 3 groups, healthy young individuals (H group (age< 50)), healthy middle-aged and older individuals (H group (age≥50)), and patients with lumbar spinal stenosis (L group). Additionally, the thickness of the ligament was measured in the axial image plane, and the occupied area ratio of each fiber was measured by staining the surgically obtained ligament, and each was correlated with the T2 relaxation time. We also evaluated the adhesion of the ligamentum flavum with the dura mater during the surgery. RESULTS: The T2 relaxation times were significantly prolonged in H group (age ≥50) and L group (P < 0.001) compared to H group (age<50). The relationship between collagen fiber and T2 relaxation times was significantly positive (r = 0.720, P < 0.001). Moreover, the relaxation times were significantly prolonged in those with adhesion of the ligamentum flavum with the dura mater (P < 0.05). The cut-off for the relaxation time was 50 ms (sensitivity: 62.50%, false positive rate: 10.8%). CONCLUSION: Healthy middle-aged and older individuals and patients with lumbar spinal stenosis and adhesion of the ligamentum flavum with the dura mater have prolonged T2 relaxation times. Hence, the adhesion between the ligamentum flavum and dura mater should be considered in cases with a relaxation time ≥50 ms.

Manipulation of osteogenic and adipogenic differentiation of human degenerative disc and ligamentum flavum derived progenitor cells using IL-1ß, IL-19, and IL-20.

PURPOSE: To elucidate whether pro-inflammatory cytokines might influence the commitment of intervertebral disc (IVD)- and ligamentum flavum (LF)-derived progenitor cells toward either osteogenesis or adipogenesis, specifically Interleukin-1ß (IL-1ß), IL-19, and IL-20. METHODS: Sixty patients with degenerative spondylolisthesis and lumbar or lumbosacral spinal stenosis were included in the study. Injuries to the spine, infections, and benign or malignant tumors were excluded. From nine patient samples, IVD- and LF-derived cells were isolated after primary culture, and two clinical samples were excluded due to mycoplasma infection. The effects of IL-1ß, IL-19, as well as IL-20 in regulating osteogenic and adipogenic differentiation in vitro were investigated. RESULTS: Primary IVD- and LF-derived cells were found to have a similar cell morphology and profile of surface markers (CD44, CD90, and CD105) as placenta-derived mesenchymal stem cells (MSCs). Primary IVD/LF cells have a high capacity to differentiate into osteocytes and adipocytes. IL-19 had a tendency to promote adipogenesis. IL-20 inhibited osteogenesis and promoted adipogenesis; IL-1ß promoted osteogenesis but inhibited adipogenesis. CONCLUSION: IL-1ß, IL-19, and IL-20 impact the adipogenic and osteogenic differentiation of IVD-derived and LF-derived cells. Modulating the expression of IL-1ß, IL-19, and IL-20 provides a potential avenue for controlling cell differentiation of IVD- and LF-derived cells, which might have beneficial effect for degenerative spondylolisthesis and spinal stenosis.

GSK-3ß and ß-Catenin Signaling Pathway is Involved in Myofibroblast Transition of Ligamentum Flavum in Lumbar Spinal Stenosis Patients.

STUDY DESIGN: Histologic analysis of the ligamentum flavum (LF) in the lumbar spine. OBJECTIVE: The objective of this study is to investigate the levels of glycogen synthase kinase-3ß (GSK-3ß) and ß-catenin in the LF tissue of patients with lumbar spinal stenosis (LSS). SUMMARY OF BACKGROUND DATA: The hypertrophy of the LF is the primary cause of the progression of LSS. Recently, Wnt signaling has been proposed as one of the molecular processes contributing to LF hypertrophy. GSK-3ß and ß-catenin are recognized to play a crucial part in the control of this signaling pathway. MATERIALS AND METHODS: From May 2020 to July 2022, LF from 51 LSS patients (LSS group) and 18 lumbar disc herniation patients (control group) were prospectively collected during surgery. Histologic analysis was investigated to confirm the progression of LF fibrosis. The levels of α-smooth muscle actin, phosphorylation of GSK-3ß (p-GSK-3ß; inactive form), and ß-catenin were analyzed in LF with Western blot analysis to reveal the GSK-3ß/ß-catenin signaling pathway. Continuous variables are expressed as mean±SD and compared using the student t test. Categorical variables are compared using the χ 2 test or Fisher exact test, as appropriate. To determine the association between p-GSK-3ß and LF thickness, the Pearson correlation coefficient was calculated based on the results of Western blot analysis. RESULTS: The LSS group was older and had thicker LF than the controls. The LSS group showed increased collagen fiber and cellularity than the controls. The levels of α-smooth muscle actin, p-GSK-3ß, and ß-catenin in the LF of the LSS group were significantly higher than that of the control group. There was a strong positive correlation between p-GSK-3ß (Ser9) level and LF thickness in LSS patients ( r =0.69, P =0.01). CONCLUSION: This research proposes a molecular mechanism for the pathogenesis of LF hypertrophy in LSS. Specifically, GSK-3ß/ß-catenin signaling appears to be related to LF hypertrophy in LSS and a positive correlation exists between p-GSK-3ß level and LF thickness. LEVEL OF EVIDENCE: Level 3.

Navigation-Assisted Micro-Window Excision of Thoracic Ossification of Ligamentum Flavum (Mishima Surgery) in Professional Baseball Pitchers: A Case Report and Technical Note.

Background and Objectives: Thoracic ossification of the ligamentum flavum (OLF) often causes myelopathy and/or radiculopathy. The disease is frequently observed in East Asian populations. Although thoracic OLF in young athletes who have underwent decompression surgery has been reported, the removal of posterior spinal bony elements and ligamentous complex may often cause postoperative thoracolumbar instability. We established a novel surgical technique that preserves the posterior spinal elements, including the spinous processes, facet joints, and supraspinous and interspinous ligaments for thoracic OLF. This is the first case report to describe a navigation-assisted micro-window excision of thoracic OLF. Case: A 32-year-old male right-handed professional baseball pitcher with significant weakness and numbness in the left leg was referred to our hospital. The patient was diagnosed with thoracic OLF at T10-11 based on radiographic and magnetic resonance images in August 2022. After exposure of the left T10-11 laminae via a small unilateral incision, the location of T10-11 OLF was detected over the lamina by O-arm navigation. Then, the micro-window was made directly above the OLF using a navigated air drill, and the OLF was removed on the ipsilateral side. The contralateral side of OLF was also resected through the same micro-window, achieving complete spinal cord decompression. Results: The next day of the surgery, his leg weakness and numbness were significantly improved. Six weeks after the surgery, he started pitching. Three months after surgery, his symptoms had gone completely, and he pitched from the mound. Approximately 6 months after surgery, he successfully pitched in a professional baseball game. Conclusions: A navigation-assisted micro-window excision of thoracic OLF effectively preserved the spinal posterior bony elements and ligamentous complex. However, long-term clinical outcomes should be evaluated in future studies.

A muscle-preserving, spinous process-splitting approach for ossification of the ligamentum flavum in the thoracic spine in professional athletes: a report of three cases.

A muscle-preserving, spinous process-splitting approach may be a less invasive approach to conventional laminectomy in patients with thoracic ossification of the ligamentum flavum. Few reports have discussed the usefulness of this procedure for thoracic lesions in professional athletes who need highly active thoracic spinal function after surgery. The treatment of thoracic ossification of the ligamentum flavum using a spinous process-splitting approach in 3 professional athletes is presented. In all three cases the patients could return to play within 3 months after surgery without complications, and in two of the cases, there was no spinal deformity or local recurrence of ossification of the ligamentum flavum at the final follow-up at least 8 years after surgery. The spinous process-splitting approach could be a safe procedure for multi-level and all other forms of ossification of the ligamentum flavum and is less invasive to the paraspinal muscles, relieves back symptoms, and restores function for athletes.

Transcriptomic alterations in hypertrophy of the ligamentum flavum: interactions of Rho GTPases, RTK, PIK3, and FGF.

PURPOSE: To analyze the differential transcriptome expression in hypertrophic ligaments flavum (HLF) compared to normal ligaments. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Impact of oxidized LDL/LOX-1 system on ligamentum flavum hypertrophy.

BACKGROUND: Patients with lumbar spinal canal stenosis (LSS) often have peripheral arterial disease and aortic disease based on atherosclerosis. Oxidized LDL, which is clinically involved in the development of atherosclerosis, may also influence LF hypertrophy, but the function of the oxidized low-density lipoprotein (LDL)/lectin-type oxidized LDL receptor 1 (LOX-1) system in LF hypertrophy is unknown. We aimed to elucidate the potential involvement of oxidized LDL/LOX-1 system in ligamentum flavum (LF) hypertrophy. METHODS: A total of 43 samples were collected from LF tissues of the patients who underwent posterior lumbar spinal surgery. Immunohistochemistry for LOX-1 was performed using human LF samples. We treated the cells in vitro with inflammatory cytokines TNF-α and IL-1ß, oxidized LDL, and simvastatin. The expressions of LOX-1 and LF hypertrophy markers including type I collagen, Type III collagen, and COX-2 were assessed by real-time RT-PCR and immunocytochemistry. Phosphorylation of MAPKs and NF-κb was evaluated by Western blot after treatment with TNF-α, IL-1ß, oxidized LDL, and simvastatin. RESULTS: A significant weak correlation was observed between the number of positive cells of LOX-1 and cross-sectional area of LF on preoperative axial magnetic resonance imaging. In functional analysis, simvastatin treatment neutralized the oxidized LDL-mediated induction of mRNA expressions of LF hypertrophy markers. Western blot analysis showed that oxidized LDL as well as TNF-α and IL-1ß activated the signaling of MAPKs and NF-κb in LF cells, and that simvastatin treatment reduced the phosphorylation of all signaling. The TNF-α and IL-1ß treatments increased both mRNA and protein expression of LOX-1 in LF cells. CONCLUSION: We found a link between the oxidized LDL/LOX-1 system and LF hypertrophy. In addition, our in vitro analysis indicate that oxidized LDL may affect LF hypertrophy through signaling of MAPKs. Our results suggest that the oxidized LDL/LOX-1 system may be a potential therapeutic target for LSS.

EGF Contributes to Hypertrophy of Human Ligamentum Flavum via the TGF-ß1/Smad3 Signaling Pathway.

Background: The most common spinal disorder in elderly is lumbar spinal canal stenosis (LSCS). Previous studies showed that ligamentum flavum hypertrophy (LFH) with fibrosis as the main pathological change is one of the pathogenic factors leading to LSCS. Epidermal Growth Factor (EGF) is known to have an intimate relationship with fibrosis in various tissues. Nevertheless, currently, there are few studies regarding EGF in LFH. The effect of EGF on the development of LFH is unknown, and the underlying pathomechanism remains unclear. In this study, we investigated the role of EGF in LFH and its potential molecular mechanism. Methods: First, the expression levels of EGF, phosphorylation of EGF receptor (pEGFR), Transforming growth factor-ß1 (TGF-ß1), Phosphorylated Smad3 (pSmad3), collagen I and collagen III were examined via immunohistochemistry and Western blot in LF tissues from patients with LSCS or Non-LSCS. Second, primary LF cells were isolated from adults with normal LF thickness and were cultured with different concentrations of exogenous EGF with or without erlotinib/TGF-ß1-neutralizing antibody. Results: The results showed that EGF, pEGFR, TGF-ß1, pSmad3, collagen I and collagen III protein expression in the LSCS group was significantly higher than that in the Non-LSCS group. Meanwhile, pEGFR, TGF-ß1, pSmad3, collagen I and collagen III protein expression was significantly enhanced in LF cells after exogenous EGF exposure, which can be notably blocked by erlotinib. In addition, pSmad3, collagen I and collagen III protein expression was blocked by TGF-ß1-neutralizing antibody. Conclusions: EGF promotes the synthesis of collagen I and collagen III via the TGF-ß1/Smad3 signaling pathway, which eventually contributes to LFH.

Coexistence of flavum ligament ossification with diffuse idiopathic skeletal hyperostosis in the cervical spine: Review of literature and technical note starting from a rare case.

BACKGROUND: Cervical flavum ligament ossification (C-OLF) is very rare source of myeloradiculopathy. Less than 100 cases have been reported in modern English literature up to 2020. Association between C-OLF and Diffuse Idiopathic Skeletal Hyperostosis (DISH) at cervical level has never been described. METHODS: In this article we performed a systematic review about epidemiology, physiopathology, clinical and surgical management of C-OLF. Moreover, we research its possible association with other cervical spine ligament ossification and in particular with anterior longitudinal ligament ossification. We report a case of 73 years-old woman experiencing mild cervical myeloradiculopathy caused by C6-C7 C-OLF compression and coexistence of DISH at cervico-thoracic level. A brief technical note about intraoperative management of C-OLF has also been described. RESULT: Our research found 81 previous reported case of C-OLF. The coexistence of Posterior longitudinal ligament ossification has been reported in 21.3% of C-OLF case. Conversely, we reported the first case describing the association between DISH and C-OLF. Posterior surgical decompression is the only useful treatment providing good long-term functional outcome. Instrumentation should be tailored according to pre-operative findings. CONCLUSIONS: C-OLF is a rare source of myeloradiculopathy and it may coexists with DISH probably due to alteration in the cervical mechanical stress and tendency of bone formation in patients harboring coexistent ligament ossifications. According to our result, skip en-bloc microsurgical laminectomy is safe and less invasive method to avoid complication and to provide optimal cervical spinal cord and nerve decompression avoiding CSF-leak.

Thoracic ossification of the ligamentum flavum causing Brown-Séquard syndrome: a case report and literature review.

Brown-Séquard syndrome (BSS) has many etiologies, including penetrating trauma, extramedullary tumors, and disc herniation. However, thoracic ossification of the ligamentum flavum (OLF) is an extremely rare cause of this syndrome. A 46-year-old woman with motor weakness in her right lower extremity and urinary retention was admitted to our department. Based on the results of physical examination, computed tomography, and magnetic resonance imaging, a diagnosis of BSS with OLF was considered. The patient underwent urgent conservative treatment. BSS is a rare condition characterized by hemisection or hemicompression of the spinal marrow. The herein-described case of incomplete BSS due to OLF responded to conservative treatment. However, the successful nonoperative management of this case is insufficient evidence to consider it as the standard of care. Therefore, emergency laminectomy decompression remains the standard of care for BSS.