Thickness of the ligamentum flavum: correlation with age and its asymmetry-an magnetic resonance imaging study

Analysis of the Thickness of Ligamentum Flavum and Its Relationship With Degenerative Disc Changes at L3-4, L4-5, and L5-S1 Levels in Patients Undergoing Magnetic Resonance Imaging (MRI) of the Lumbosacral Spine

Background Low back pain (LBP) is the leading cause of disability among working-age adults, with its prevalence increasing with age and peaking in the 45-54 age group. It is common practice for clinicians to conduct advanced imaging procedures, such as computed tomography (CT) and magnetic resonance imaging (MRI) when a patient presents with LBP. The objective of this study was to measure and analyze the width of the ligamentum flavum (LF) on each side and the extent of degeneration of the disc at the L3-4, L4-5, and L5-S1 levels. Methods The current investigation was a cross-sectional descriptive-analytical effort carried out in the radiodiagnosis department of Sri Devaraj Urs Medical College, Tamaka, Kolar, from July 2024 to September 2024. The study's inclusion criteria were participants in age groups ranging from 20 to 60 years who were referred for an MRI of the lumbosacral spine and had a prior history of LBP. Results Out of 60 subjects, 26 (43.3%) individuals were females, and 34 (56.7%) individuals were males. Out of the maximum number of patients, 23 (38.3%) were within the age range of 31-40 years. The medial and lateral aspects of the LF measurements showed an increase with age, with lateral values being greater than the medial measurements (p = 0.001). The mean thickness of the ligament and the mean height of the disc showed significant variations at all levels. Statistically significant differences were seen in the thickness of the LF of male patients (4.82, 0.62 mm) compared to female patients (4.89, 0.72 mm). A statistically significant positive Pearson association was observed between the thickening of the LF and Pfirrmann grading of degenerative disc disease (DDD). Conclusion The LF thickness is significantly associated with disc degeneration, especially at the L4-L5 level, contributing to spinal canal stenosis, which is critical for the management of LBP.

Cellular and Molecular Mechanisms of Hypertrophy of Ligamentum Flavum

Hypertrophy of the ligamentum flavum (HLF) is a common contributor to lumbar spinal stenosis (LSS). Fibrosis is a core pathological factor of HLF resulting in degenerative LSS and associated low back pain. Although progress has been made in HLF research, the specific molecular mechanisms that promote HLF remain to be defined. The molecular factors involved in the onset of HLF include increases in inflammatory cytokines such as transforming growth factor (TGF)-β, matrix metalloproteinases, and pro-fibrotic growth factors. In this review, we discuss the current understanding of the mechanisms involved in HLF with a particular emphasis on aging and mechanical stress. We also discuss in detail how several pathomechanisms such as fibrosis, proliferation and apoptosis, macrophage infiltration, and autophagy, in addition to several molecular pathways involving TGF-β1, mitogen-activated protein kinase (MAPKs), and nuclear factor-κB (NF-κB) signaling, PI3K/AKT signaling, Wnt signaling, micro-RNAs, extracellular matrix proteins, reactive oxygen species (ROS), etc. are involved in fibrosis leading to HLF. We also present a summary of the current advancements in preclinical animal models for HLF research. In addition, we update the current and potential therapeutic targets/agents against HLF. An improved understanding of the molecular processes behind HLF and a novel animal model are key to developing effective LSS prevention and treatment strategies.

Prevalence of and factors associated with stenotic thoracic ligamentum flavum hypertrophy

INTRODUCTION

Stenotic thoracic ligamentum flavum hypertrophy can cause leg and/or low back pain similar to that caused by lumbar spinal stenosis. However, the thoracic spine may occasionally be overlooked in patients with leg and/or low back pain. An accurate understanding of the prevalence of stenotic thoracic ligamentum flavum hypertrophy and its associated factors is necessary.

METHODS

In this prevalence study, we reviewed whole-spine MRI scans of patients who visited the pain clinic complaining of leg and/or low back pain between 2010 and 2019. We analyzed the overall prevalence and prevalence according to the age group, sex, grade of lumbar disc degeneration, and thoracic level. In addition, we identified factors independently associated with stenotic thoracic ligamentum flavum hypertrophy occurrence.

RESULTS

Among 1896 patients, the overall prevalence of stenotic thoracic ligamentum flavum hypertrophy was 9.8% (185/1896), with the highest prevalence observed in the ≥80-year-old age group among all age groups (15.9%, 14/88). The region with the highest prevalence was the T10/11 level (3.0%, 57/1896). Multivariable logistic regression analysis revealed that when compared with the <50-year-old age group, all other age groups were significantly associated with stenotic thoracic ligamentum flavum hypertrophy (p<0.01). In addition, grade 5 of lumbar disc degeneration was significantly associated with stenotic thoracic ligamentum flavum hypertrophy (p=0.03).

CONCLUSIONS

Given the possibility for missed stenotic thoracic ligamentum flavum hypertrophy to potentially result in neurological complications, extending lumbar spine MRI covering the lower thoracic region may be considered for patients over 50 years of age with suspected severe lumbar disc degeneration.

[Red flags of cardiac amyloidosis in patients with spinal stenosis and yellow ligament hypertrophy]

INTRODUCTION

Studies addressing the prevalence of cardiac amyloidosis (CA) among patients with spinal stenosis (SS) are lacking. The identification of the red flags (RF) of CA could lead to early detection of cases of CA. The primary objective of this study was to address the prevalence of RF of CA among patients with SS.

METHODS

Transversal study including consecutive cases with SS and yellow ligament hypertrophy (YLH). A clinical assessment that included electrocardiogram, echocardiogram and urine and blood test was performed. A clinical suspicion of CA was defined by the presence of left ventricular hypertrophy plus any RF.

RESULTS

One hundred and three patients with SS and YLH were assessed. The prevalence of RF was high: heart failure: 18.4%; aortic stenosis: 1.9%; carpal tunnel syndrome: 7.8%; bicipital tendon rupture: 1.9%; arterial hypotension: 17.4%; polyneuropathy symptoms: 51.5%; pseudoinfarction pattern: 3.9%; low voltages: 15.5%; conduction abnormalities: 15.5%; decreased longitudinal strain: 25.3%; apical sparing pattern: 3.9%. The 57.3% of the cohort met the CA suspicion criteria.

CONCLUSION

The prevalence of RF of CA is high among patients with SS and YLH. A high proportion of patients met the CA suspicion criteria.

The cervical ligamentum flavum area: A new sensitive morphological parameter for identifying the cervical spinal stenosis

Thickening of the cervical ligamentum flavum (CLF) has been considered as a main cause of cervical spinal stenosis (CSS). A previous study reported that cervical ligamentum flavum thickness (CLFT) is correlated with CSS. However, the whole hypertrophy is different from focal thickness. Therefore, to analyze hypertrophy of the CLF, we created a new morphological parameter, called the cervical ligamentum flavum area (CLFA). We hypothesized that the CLFA is an important morphological parameter in the diagnosis of CSS. CLF samples were acquired from 83 patients with CSS, and from 84 controls who underwent cervical magnetic resonance imaging (C-MRI). T2-weighted axial C-MRI images were acquired. We measured the CLFA and CLFT at the C6-C7 intervertebral level on C-MRI using appropriate image analysis software. The CLFA was measured as the cross-sectional area of the entire CLF at the level of C6-C7 stenosis. The CLFT was measured by drawing a straight line along the ligament side towards the spinal canal at the C6-C7 level. Mean CLFA was 25.24 ± 6.43 mm2 in the control group and 45.34 ± 9.09 mm2 in the CSS group. The average CLFT was 1.48 ± 0.28 mm in the control group and 2.09 ± 0.35 mm in the CSS group. CSS patients had significantly higher CLFA (P < .01) and CLFT (P < .01). For the validity of both CLFA and CLFT as predictors of CSS, a receiver operating characteristic curve analysis revealed an optimal cutoff point for the CLFA was 31.66 mm2, a sensitivity of 92.8%, specificity of 88.4%, and an area under the curve of 0.97 (95% CI, 0.94-0.99). The optimal cut off-point of the CLFT was 1.79 mm, with a sensitivity of 83.5%, specificity of 84.5%, and an area under the curve of 0.92 (95% CI, 0.87-0.96). Both CLFT and CLFA were significantly related to CSS, but CLFA was the more sensitive measurement parameter. Therefore, to evaluate patients with CSS, treating physicians should test for CLFA.

The COVID-19 Pandemic and Elective Spine Surgery-A Single Center Experience

Background and objective: The COVID-19 pandemic had a profound impact on medical practice worldwide. In this study, we aimed to investigate the trends of elective spine surgery in our department before and during the pandemic. Materials and methods: Total number of spine procedures due to disc herniation (DH) or spinal stenosis (SS) was collected during 2019-2021 in the Department of Neurosurgery, University Hospital Center Osijek, Croatia. In order to elucidate potential risk factors in the post-pandemic period, demographic data were collected for patients who underwent surgery during 2021. Results: In 2020, there was a 22.1% decrease in the number of surgeries compared to 2019 (205 vs. 263), but during 2021 we observed an increase of 36.1% compared to 2020 (279 vs. 205). The mean age of patients in 2021 was 53.14 years (53.14 ± 13.05) with body mass index of 28.31 kg/m2 (28.31 ± 4.89). There were 179 overweight patients (74%) and 103 smokers (42.6%). Although male and female patients were equally represented (121 each), there was a significant interaction of weight class and sex (p = 0.013). Patients younger than 65 were more likely to undergo surgery due to DH (p < 0.001), whereas older patients were more likely to suffer from SS (p < 0.001). Conclusions: The volume of elective spine surgeries decreased in the first year of the pandemic and increased the following year. Our results suggest that public health policies in the early pandemic period reduced elective surgical procedures, which was followed by a compensatory increase in the following period.

Comparison of ligamentum flavum thickness between central and lateral lesions in a patient with central lumbar spinal canal stenosis

Thickened ligamentum flavum has been considered as a major cause of central lumbar spinal canal stenosis (CLSCS). Previous studies have demonstrated that ligamentum flavum thickness (LFT) is correlated with aging, degenerative spinal stenosis, and disc degeneration. Thus, hypertrophy of the ligamentum flavum is a major cause of CLSCS, and measurement of LFT has been considered a morphologic parameter in the diagnosis of CLSCS. To our knowledge, comparison of LFT between central and lateral lesions has not been reported. In addition, no research has analyzed best clinical cutoff values of central ligament flavum thickness (CLFT) and lateral ligament flavum thickness (LLFT). This study aimed to compare CLFT with LLFT in patients with CLSCS and further compare the CLFT and LLFT findings between the 2 groups to analyze LFT variation. Both CLFT and LLFT samples were collected from 101 participants with CLSCS and from 103 participants in the control group who underwent lumbar magnetic resonance imaging without evidence of CLSCS. Axial T2-weighted lumbar magnetic resonance scans were acquired at the L4 to 5 facet joint level from each participant. Average CLFT value was 2.25 ± 0.51 mm in the control group and 4.02 ± 0.74 mm in the CLSCS group. Average LLFT value was 2.50 ± 0.51 mm in the control group and 3.38 ± 0.66 mm in the CLSCS group. CLSCS patients had significantly higher CLFT and LLFT (both P < .001). Regarding the validity of both CLFT and LLFT as predictors of CLSCS, a receiver operating characteristic estimation revealed that the most suitable cutoff value for CLFT was 3.10 mm, with sensitivity of 95.0%, specificity of 94.2%, and an area under the curve of 0.97. The best cut-off value of LLFT was 2.92 mm, with sensitivity of 78.2%, specificity of 77.7%, and area under the curve of 0.87. We have 4 important new findings: The mean CLFT is significantly lower than that of the mean LLFT in the normal control group; CLFT and LLFT are both significantly associated with CLSCS; Increase rate of CLFT is faster than that of LLFT in the CLSCS group; and CLFT is a more sensitive measurement parameter to predict CLSCS than LLFT.

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.

Ligamentum flavum analysis in patients with lumbar discus hernia and lumbar spinal stenosis

The normal ligamentum flavum (LF) is a well-defined elastic structure with specific innervation. Several studies investigated LF in patients with lumbar spinal stenosis (LSS) and used lumbar discus hernia (LDH) patients as control group, only on the presumed thesis that LF in this patients have normal morphology. In patients with LSS thickening of the LF is the main cause of stenosis, which is most often presented with neurogenic claudication, whose pathophysiological mechanism is not completely understood. We conducted observational cohort study of 60 operated patients divided into two groups. The first group of 30 patients underwent micro-discectomy (LSH group), and second group with 30 patients underwent decompression, after which analysis of harvested LF was performed. Patients from the LDH group and LSS group differed significantly in the frequencies of chief complaints, duration of symptoms, physical examination, and specific morphological/radiological parameters. The LF analysis showed that the groups differed significantly in the amount of collagen and elastic fibers, as well as in the histological appearance/architectonics of elastic fibers. Also, groups differ in the presence of LF nerve fibers. Our findings speak in favor of the recently postulated inflammatory theory in the origin of spinal neurogenic claudication's.

Histological difference in ligament flavum between degenerative lumbar canal stenosis and non-stenotic group: A prospective, comparative study

BACKGROUND

Ligament flavum (LF) hypertropy is the main etiopathogenesis of lumbar canal stenosis (LCS). The purely elastic LF undergoes a morphological adaptation including a reduction in the elastic fibers and a consequent increase in the collagen content, fibrosis, cicatrization, and calcification. However, the morphometric analysis can delineate the LF in patients with LCS from those without LCS, which would help in better understanding LCS pathogenesis.

AIM

To compare the histopathological changes in LF between the degenerative LCS and non-stenotic (non-LCS) group.

METHODS

The present prospective study was conducted in 82 patients who were divided into two groups, namely LCS and non-LCS. Demographic details of the patients such as duration of symptoms, level of involvement, and number of segments were recorded. The LF obtained from both groups was histopathologically examined for the fibrosis score, elastic fiber degeneration, calcification, and chondroid metaplasia. Morphometrical details included a change in elastin and collagen percentages, elastin/collagen ratio, elastic fiber fragmentation, and ligamentocyte numbers. All parameters were compared between the two groups by using the independent t test, Chi-square test, and Pearson’s correlation test.

RESULTS

Out of 82 cases, 74 were analysed, 34 in LCS and 40 in non-LCS group. The mean ± SD age of presentation in LCS and non- LCS group was 49.2 ± 8.9 and 43.1 ± 14.3 respectively. The LCS group (n = 34) exhibited significant differences in fibrosis (P = 0.002), elastic fiber degeneration (P = 0.01), % elastic fragmentation (66.5 ± 16.3 vs 29.5 ± 16.9), % elastic, content (26.9 ± 6.7 vs 34.7 ± 8.4), % collagen content (63.6 ± 10.4 vs 54.9 ± 6.4), reduction of elastic/collagen (0.4 ± 0.1 vs 0.6 ± 0.1), and ligamentocyte number (39.1 ± 19.1 vs 53.5 ± 26.9) as compared to non-LCS group (n = 40). The calcification (P = 0.08) and Pearson’s correlation between duration and loss of elastin was not significant. The difference in LF morphology is consistent in patient’s ≥ 40 years of age among the groups as found in subgroup analysis. Similarly in the patents < 40 and > 40 in the non-LCS group.

CONCLUSION

LF is vital in the pathogenesis of LCS. The purely elastic LF undergoes a morphological adaptation that includes a reduction in the elastic fibers with a consequent increase in the collagen content, fibrosis, cicatrization, and calcification. The present study provides a detailed morphometric analysis to semiquantitatively delineate the LF changes in patients with LCS from those in patients without LCS.

Selective Nerve Root Block in Treatment of Lumbar Radiculopathy: A Narrative Review

Selective Nerve Root Block (SNRB) is a precise local injection technique that can be utilised to target a particular inflamed nerve root causing lumbar radiculopathy for both diagnostic and therapeutic purposes. Usually, for SNRB to be therapeutic, a combination of a local anaesthetic agent and a steroid is injected under imaging guidance, whereas for diagnostic purposes, just the local anaesthetic agent is injected. While the ideal treatment strategy is to relieve the nerve root from its compressing pathology, local injection of steroids targeted at the affected nerve root can also be attempted to reduce inflammation and thus achieve pain relief. Although the general principle for administering an SNRB remains largely the same across the field, there are differences in techniques depending on the region and level of the spine that is targeted. Moreover, drug combinations utilised by clinicians vary based on preference. The proven benefits of SNRBs largely outweigh their risks, and the procedure is deemed safe and well tolerated in a majority of patients. In this narrative, we explore the existing literature and seek to provide a comprehensive understanding of SNRB as a treatment for lumbar radiculopathy, its indications, techniques, outcomes, and complications.

EGF Contributes to Hypertrophy of Human Ligamentum Flavum via the TGF-β1/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-β1 (TGF-β1), 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-β1-neutralizing antibody. Results: The results showed that EGF, pEGFR, TGF-β1, 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-β1, 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-β1-neutralizing antibody. Conclusions: EGF promotes the synthesis of collagen I and collagen III via the TGF-β1/Smad3 signaling pathway, which eventually contributes to LFH.

Inclination of the small laminar slope angle leads to lumbar spinal stenosis due to hypertrophy of the ligamentum flavum

OBJECTIVE

This study was designed to investigate the relationship between the laminar slope angle (LSA) and the lumbar disc degenerative grade, the cross-section area (CSA) of multifidus muscle, the muscle-fat index, and the thickness of the ligamentum flavum.

METHODS

Retrospective analysis of 122 patients who were scheduled to undergo a lumbar operation for diagnoses associated with degenerative lumbar disease between January and December 2017. The L4-L5 disc grade was evaluated from preoperative sagittal T2-weighed magnetic resonance imaging of the lumber region; the CSA of the multifidus and muscle-fat index were measured at the L4 level, while the thickness of the ligamentum flavum was measured at the L4-L5 facet level from axis T2-weighed magnetic resonance imaging. The slope of the laminar was evaluated from preoperative three-dimensional computer tomography at the tip level of the facet joints and selected by the axis plane. Independent-sample T-tests were used to assess the association between age and measurement indices.

RESULTS

Our results showed that age was positively connected with the LSA of L4 and L5 in different patients, although there was no significant difference between age and the difference of the two segment LSA. Partial correlation analysis, excluding the interference of age, revealed a strong negative relationship between the LSA of L4 and the thickness of the ligamentum flavum, irrespective of whether we considered the left or right. However, there was no correlation with lumbar disc degenerative grade, the CSA of the multifidus, and the muscle-fat index.

CONCLUSION

The thickness of the ligamentum flavum showed changes with anatomical differences in the LSA, but not the lumbar disc degenerative grade, the CSA of the multifidus, and the muscle-fat index. A small change in LSA may cause large mechanical stress; this may be one of the causative factors responsible for lumbar spinal stenosis.

Increased thickness of lumbar spine ligamentum flavum in wild-type transthyretin amyloidosis

BACKGROUND

Wild-type transthyretin (ATTRwt) amyloid deposits have been found in the ligamentum flavum of patients undergoing surgery for spinal stenosis. The relationship between ATTRwt and ligamentum flavum thickness is unclear. We used pre-operative magnetic resonance imaging (MRI) to analyze ligamentum flavum thickness in lumbar spinal stenosis patients with and without ATTRwt amyloid.

METHODS

We retrospectively identified 178 patients who underwent lumbar spine surgery. Ligamentum flavum thickness of 253 specimens was measured on T2-weighted axial MRI. Amyloid presence was confirmed through Congo red staining of specimens, and ATTRwt was confirmed using mass-spectrometry and gene sequencing.

RESULTS

Twenty four of the 178 patients (13.5%) were found to have ATTRwt in the ligamentum flavum. Forty ATTRwt specimens and 213 non-ATTRwt specimens were measured. Mean ligamentum flavum thickness was 4.92 (±1.27) mm in the ATTRwt group and 4.00 (±1.21) mm in the non-ATTRwt group (p < 0.01). The ligamentum flavum was thickest at L4-L5, with a thickness of 5.15 (±1.27) mm and 4.23 (±1.29) mm in the ATTRwt and non-ATTRwt group, respectively (p = 0.007). There was a significant difference in ligamentum flavum thickness between ATTRwt and non-ATTRwt case for both patients younger than 70 years (p = 0.016) and those older than 70 years (p = 0.004). ATTRwt patients had greater ligamentum flavum thickness by 0.83 mm (95% confidence interval (CI): 0.41-1.25 mm, p < 0.001) when controlled for age and lumbar level.

CONCLUSION

Patients with ATTRwt had thicker ligamentum flavum compared to patients without ATTRwt. Further studies are needed to investigate the pathophysiology of ATTRwt in ligamentum flavum thickening.

Advanced Quantitative Spine Imaging

Although advanced quantitative imaging may not be currently used to any degree in the routine reporting of spinal examinations, this situation will change in the not too distant future. Advanced quantitative imaging has already allowed us to understand a great deal more regarding spinal development, marrow physiology, and disease pathogenesis. Radiologists are ideally suited to drive this research forward. To speed up this process and optimize the impact of studies reporting spine quantitative data, we should work toward universal standards on the acquisition of spine data that will allow quantitative studies to be more easily compared, contrasted, and amalgamated.

CRLF1 Is a Key Regulator in the Ligamentum Flavum Hypertrophy

Hypertrophy of the ligamentum flavum (HLF) is one of the common causes of lumbar spinal stenosis (LSS). The key molecules and mechanisms responsible for HLF remain unclear. Here, we used an integrated transcriptome and proteomics analysis of human ligamentum flavum (LF), and subsequent immunohistochemistry and real-time PCR assays, to show upregulation of CRLF1 to be the dominant response to HLF. TGF-β1 significantly increased mRNA expression of CRLF1 through SMAD3 pathway. CRLF1 enhanced LF fibrosis via ERK signaling pathway at the post-transcriptional level and was required for the pro-fibrotic effect of TGF-β1. Knockdown of CRLF1 was shown here to reduce fibrosis caused by inflammatory cytokines and mechanical stress. Furthermore, we found that bipedal standing posture can cause HLF and upregulation of CRLF1 expression in mice LF. Overexpression of CRLF1 was indicated to cause HLF in vivo, whereas CRLF1 knockdown impeded the formation of HLF in bipedal standing mice. These results revealed a crucial role of CRLF1 in LF hypertrophy. We propose that inhibition of CRLF1 is a potential therapeutic strategy to treat HLF.

Development of an In Vitro 3D Model for Investigating Ligamentum Flavum Hypertrophy

Background

Ligamentum flavum hypertrophy (LFH) is among the most crucial factors in degenerative lumbar spinal stenosis, which can cause back pain, lower extremity pain, cauda equina syndrome and neurogenic claudication. The exact pathogenesis of LFH remains elusive despite extensive research. Most in vitro studies investigating LFH have been carried out using conventional two-dimensional (2D) cell cultures, which do not resemble in vivo conditions, as they lack crucial pathophysiological factors found in three-dimensional (3D) LFH tissue, such as enhanced cell proliferation and cell cluster formation. In this study, we generated ligamentum flavum (LF) clusters using spheroid cultures derived from primary LFH tissue.

Results

The cultured LF spheroids exhibited good viability and growth on an ultra-low attachment 96-well plate (ULA 96-plate) platform according to live/dead staining. Our results showed that the 100-cell culture continued to grow in size, while the 1000-cell culture maintained its size, and the 5000-cell culture exhibited a decreasing trend in size as the culture time increased; long-term culture was validated for at least 28 days. The LF spheroids also maintained the extracellular matrix (ECM) phenotype, i.e., fibronectin, elastin, and collagen I and III. The 2D culture and 3D culture were further compared by cell cycle and Western blot analyses. Finally, we utilized hematoxylin and eosin (H&E) staining to demonstrate that the 3D spheroids resembled part of the cell arrangement in LF hypertrophic tissue.

Conclusions

The developed LF spheroid model has great potential, as it provides a stable culture platform in a 3D model that can further improve our understanding of the pathogenesis of LFH and has applications in future studies.

Wild-Type Transthyretin Amyloidosis Occurring in the Ligamentum Flavum of the Cervicothoracic Spine

BACKGROUND

Wild-type transthyretin amyloid (ATTRwt) has been noted to deposit in the ligamentum flavum of the spine. Prior studies have focused on ATTRwt in the lumbar region, but studies discussing its presence in other levels of the spine are lacking. We report on the presentation of patients with confirmed amyloid in the cervicothoracic regions and discuss the literature to date.

METHODS

We retrospectively identified patients at a single institution who underwent surgery for spinal stenosis and had pathologic specimens sent for amyloidosis testing with Congo red staining. ATTRwt was confirmed by the presence of transthyretin amyloid by typing and the absence of mutations in the TTR gene sequence. A final study group of patients with ATTRwt and spinal involvement was established (n = 27).

RESULTS

Of 27 patients with amyloid in the spine, 24 (89%) had amyloid present in the lumbar region, 2 (7%) had amyloid in the cervical region, and 1 (4%) had amyloid in the thoracic region. The median age at which patients in the study underwent surgery was 71 years (interquartile range: 9). Spinal stenosis was the indication for surgery in 26 of 27 (96%) patients. Surgery involved 1 or 2 spinal levels in 24 of 27 (89%) patients.

CONCLUSIONS

ATTRwt amyloid predominantly deposits in the lumbar region, but it can also be present in the cervical and thoracic regions. While the lumbar regions should remain a focus for evaluation of ATTRwt amyloidosis, the cervicothoracic region should not be ignored.

Ligamentum flavum fibrosis and hypertrophy: Molecular pathways, cellular mechanisms, and future directions

Hypertrophy of ligamentum flavum (LF), along with disk protrusion and facet joints degeneration, is associated with the development of lumbar spinal canal stenosis (LSCS). Of note, LF hypertrophy is deemed as an important cause of LSCS. Histologically, fibrosis is proved to be the main pathology of LF hypertrophy. Despite the numerous studies explored the mechanisms of LF fibrosis at the molecular and cellular levels, the exact mechanism remains unknown. It is suggested that pathophysiologic stimuli such as mechanical stress, aging, obesity, and some diseases are the causative factors. Then, many cytokines and growth factors secreted by LF cells and its surrounding tissues play different roles in activating the fibrotic response. Here, we summarize the current status of detailed knowledge available regarding the causative factors, pathology, molecular and cellular mechanisms implicated in LF fibrosis and hypertrophy, also focusing on the possible avenues for anti-fibrotic strategies.

Construction of an Affordable Lumbar Neuraxial Block Model Using 3D Printed Materials

Access to affordable 3D printing technology has resulted in increased interest in the creation of medical phantom task trainers. Recent research has validated the use of these trainers in simulation education. However, task trainers remain expensive, limiting their availability to medical training programs. We describe the construction of a low-cost task trainer using fused filament fabrication (FFF) printed spinal vertebrae placed in a synthetic gelatin matrix. Additionally, our model contains a realistic simulated ligamentum flavum, a removable silicone skin, as well as spinal fluid reservoir that provides a positive endpoint for intrathecal blocks. The total cost of this model was less than $400 USD. The time to 3D print the bony anatomic parts was approximately 26 hours. While we have not formally validated our model, initial impressions of tactile feel and realism were deemed positive by experienced anesthesia providers. Future work will focus on continued refinement of the model features and construction.

Optimal cut-off points of lumbar pedicle thickness as a morphological parameter to predict lumbar spinal stenosis syndrome: a retrospective study

Purpose

Lumbar spinal stenosis syndrome (LSSS) is induced by factors such as ligamentum flavum hypertrophy, facet joint hypertrophy and disc degeneration. However, the role of lumbar pedicle (LP) in LSSS has yet to be evaluated. We devised a new morphological parameter called the lumbar pedicle thickness (LPT) to evaluate the connection between LSSS and the LP. We hypothesized that the LPT is a major morphological parameter in the diagnosis of LSSS.

Patients and methods

The LPT data were collected from 136 patients diagnosed with LSSS. A total of 99 control subjects underwent lumbar spine magnetic resonance imaging (MRI) as part of a detailed medical assessment. Axial T2-weighted magnetic resonance (MR) images were acquired from all the participants. Using our picture archiving and communication system, we analyzed the thickness of the LP at the level of L5 vertebra on MRI.

Results

The average LPT was 9.46±1.81 mm in the control group and 13.26±1.98 mm in the LSSS group. LSSS patients showed a significantly greater LPT (P<0.001) than the control group. The receiver operating characteristic (ROC) curve analysis showed an optimal cutoff point of 11.33 mm for the LPT, with 83.8% sensitivity, 83.8% specificity and area under the curve of 0.92 (95% confidence interval [CI], 0.89-0.96).

Conclusion

A higher LPT was associated with a higher possibility of LSSS, suggesting its importance in the evaluation of patients with LSSS.

Clinically significant radiographic parameter for thoracic myelopathy caused by ossification of the ligamentum flavum

PURPOSE

To investigate radiographic parameters to improve the accuracy of radiologic diagnosis for ossification of ligamentum flavum (OLF)-induced thoracic myelopathy and thereby establish a useful diagnostic method for identifying the responsible segment.

METHODS

We classified 101 patients who underwent surgical treatment for OLF-induced thoracic myelopathy as the myelopathy group and 102 patients who had incidental OLF and were hospitalized with compression fracture as the non-myelopathy group between January 2009 and December 2016. We measured the thickness of OLF (TOLF), cross-sectional area of OLF (AOLF), anteroposterior canal diameter, and the ratio of each of these parameters.

RESULTS

Most OLF cases with lateral-type axial morphology were in the non-myelopathy group and most with fused and tuberous type in the myelopathy group. Most grade-I and grade-II cases were also in the non-myelopathy group, whereas grade-IV cases were mostly observed in the myelopathy group. The AOLF ratio was found to be the best radiologic parameter. The optimal cutoff point of the AOLF ratio was 33.00%, with 87.1% sensitivity and 87.3% specificity. The AOLF ratio was significantly correlated with preoperative neurological status.

CONCLUSIONS

An AOLF ratio greater than 33% is the most accurate diagnostic indicator of OLF-induced thoracic myelopathy. In cases of multiple-segment OLF, confirmation of cord signal change on MRI and an AOLF measurement will help determine the responsible segment. AOLF measurement will also improve the accuracy of diagnosis of OLF-induced thoracic myelopathy in cases of grade III or extended-type axial morphology. These slides can be retrieved under Electronic Supplementary Material.

Dorsal Spinal Ligamentum Flavum Thickening: A Magnetic Resonance Imaging Study

Study Design

A retrospective radiological study of the ligamentum flavum (LF).

Purpose

We determined the relationship of dorsal spinal LF thickening with age and sex using magnetic resonance imaging (MRI). We also determined whether LF thickening has a predominant tendency to occur at a specific dorsal level and on a specific side.

Overview of Literature

Many researchers have studied LF thickness at dorsal levels in patients with compressive myelopathy. However, there is a dearth of literature pertaining to the study of dorsal LF thickness in patients without myelopathy.

Methods

LF thickness was measured at dorsal levels from T1 to T12 on both sides using MRI in 100 individuals. The patients were divided into three groups based on age: 20 to 40, 41 to 60, and >60 years. On axial T2-weighted imaging at the mid-disc level, LF thickness was measured perpendicular to the lamina border, either at half the length of LF or at maximum thickness, whichever was greater.

Results

We found that LF thickness does not increase significantly with increasing age and there was no significant disparity in LF thickness between the sides and sexes. We also found that there was a significant increase in LF thickness at the T10–T11 level (mean value, 3.27±0.94 mm).

Conclusions

LF thickness does not appear to have any side/sex dominance. LF thickening has a predominant tendency to occur specifically at the T10–T11 level. This may be due to maximum tensile strength and mobility at this level. Because there is an increased tendency for LF thickening at the T10–T11 level, this may be used as a reference point for counting the vertebral levels.

MicroRNA transcriptome analysis on hypertrophy of ligamentum flavum in patients with lumbar spinal stenosis

Introduction

Molecular pathways involved in ligamentum flavum (LF) hypertrophy are still unclarified. The purpose of this study was to characterize LF hypertrophy by microRNA (miRNA) profiling according to the classification of lumbar spinal stenosis (LSS).

Methods

Classification of patients with LSS into ligamentous and non-ligamentous cases was conducted by clinical observation and the morphometric parameter adopting the LF/spinal canal area ratio (LSAR) from measurements of magnetic resonance imaging (MRI) T2 weighed images. LF from patients with ligamentous stenosis (n=10) were considered as the degenerative hypertrophied samples, and those from patients with non-ligamentous LSS (n=7) and lumbar disc herniation (LDH, n=3) were used as non-hypertrophied controls. Profiling of miRNA from all samples was conducted by Agilent microarray. Microarray data analysis was performed with GeneSpring GX, and pathway analysis was performed using Ingenuity Pathway Analysis.

Results

The mean LSAR in the ligamentous group was significantly higher than that in the control group (0.662±0.154 vs 0.301±0.068, p=0.0000171). Ten significantly differentially expressed miRNA were identified and taken as a signature of LF hypertrophy: nine miRNA showed down-regulated expression, and one showed up-regulated expression in the ligamentous LF. Among those, miR-423-5p (r_s=-0.473, p<0.05), miR-4306 (r_s=-0.628, p<0.01), miR-516b-5p (r_s=-0.629, p<0.01), and miR-497-5p (r_s=0.461, p<0.05) were correlated to the LSAR. Pathway analysis predicted aryl hydrocarbon receptor signaling (p<0.01), Wnt/β-catenin signaling (p<0.01), and insulin receptor signaling (p<0.05) as canonical pathways associated with the miRNA signature.

Conclusions

Classification based on quantification of the MRI axial image is useful for studying hypertrophy of the LF. Aryl hydrocarbon receptor and Wnt/β-catenin signaling may be involved in LF hypertrophy.

Anatomical analysis of the relation between human ligamentum flavum and posterior spinal bony prominence

BACKGROUND

Posterior spinal bony prominences are commonly used as landmarks during posterior spinal surgery; however, the exact relationship of these structures with ligamentum flavum (LF) borders and attachments has not been clarified.

MATERIALS AND METHODS

Whole spines were removed en bloc from 20 embalmed human cadavers. Plain radiographs and computed tomography (CT) scans of each whole spine were taken, and then the spine was divided in two parts along the pedicle bases. The LFs were painted with contrast dye, and second radiographs and CT scans were taken again. Radiographic data were analyzed using CT image analyzer.

RESULTS

The craniolateral border of LF at four upper lumbar levels (from L1/2 to L4/5) located cranial to isthmus in both sides (3.5 mm), meanwhile, it located at or below isthmus in both sides at L5-S1 level (0.5 mm). In the midline, LF attached below the isthmus levels at four upper lumbar levels (4 mm), though it located in the same level of isthmus at L5-S1 (1 mm). The mean distance between medial border of pedicles and lateral border of LF increased from upper to the lower lumbar levels (6.5 mm at L1/2 - 11.4 mm at L5-S1). Distance between interlaminar space and cranial border of LF at the midline gradually increased from 8.2 mm at L1 toward 11.1 mm at L4, it was 9.3 mm in L5.

CONCLUSIONS

From the data of new analytical method using contrasted LF and reconstructed CT, the detailed relations between bony prominence and the border of LF were uncovered. Based on these findings and reconstructed LF images superimposed on lamina, surgeons would design safe and adequate lumbar spinal decompression with imagination of overall pictures of the LF from the dorsal side.