Prevalence, distribution, and morphology of ossification of the ligamentum flavum: a population study of one thousand seven hundred thirty-six magnetic resonance imaging scans

The coexistence of crowned dens sign and calcification of ligamentum flavum in the cervical spine: mere coincidence or meaningful association?

We present a case series of cervical radiculomyelopathy caused by calcification of the ligamentum flavum (CLF), with or without concomitant periodontoid calcification. A brief literature review is presented, highlighting a potential relationship between these 2 conditions. In this retrospective study, we reviewed medical records of 33 patients diagnosed with cervical CLF. And we propose the term "crowned dens sign" (CDSign) to describe the characteristic radiographic finding of circumferential calcification around the odontoid process of the axis. Among the 33 patients, 28 (84.8%) were female and 5 (15.2%) were male, with a mean age of 70.6 years. Based on the cervical computed tomography images, a total of 81 cervical segments of CLF were recorded. The most commonly involved levels were C4-5 and C5-6, demonstrating the characteristic pattern of mid-cervical predominance. The CDsign was identified in 26 cases (79%), demonstrating a high prevalence in this cohort. The patient cohort comprised the following treatment groups: 2 patients received conservative management, twenty-three underwent posterior surgical procedures, and 8 were treated with anterior cervical surgery. The coexistence of CDSign and CLF represents an exceptionally rare clinical occurrence. The correlation between these 2 conditions extends beyond mere coincidence. The coexistence of CLF and CDSign may represent a rare but distinct cervical manifestation of calcium pyrophosphate dihydrate deposition disease.

Comprehensive review of the cervical ligamenta flava

PURPOSE

The current literature contains many data associated with the cervical ligamentum flavum (CLF). The present study is to overview knowledge of CLF.

METHODS

Comprehensive literature review was performed.

RESULTS

Topics include anatomy, embryology, histology, radiology, clinical relevance, and pathological manifestations of the CLF, including ossification, calcification, and hypertrophy. Spine procedures always require extreme precision; spine surgeons and neurosurgeons encounter challenges that put patients' lives at risk.

CONCLUSION

This study can assist clinicians in performing spinal interventions with the fewest possible complications. Because there have been few studies of the CLF, further investigation is suggested.

Predictive factors of poor surgical outcome in thoracic ossified ligamentum flavum: A multivariate analysis

OBJECTIVE

Ossified ligamentum flavum (OLF) of the spine is a rare cause of compressive myelopathy. OLF is prevalent in Asian countries. Surgery is the only treatment option for symptomatic patients. The recovery after surgery depends upon multiple clinical and radiological factors and varies significantly. We report our series of surgically managed thoracic OLF and the factors predicting poor outcomes.

METHODS

A retrospective study was conducted including 52 patients who underwent surgery for thoracic OLF. The pre-operative clinical status, radiology findings, intraoperative observations and complications were analyzed with post-op clinical outcomes. The mean follow-up period was 24 months (range 12-72).

RESULTS

There were 35 males and 17 females with a mean age of 49.5 years (range: 30-75). The mean duration of symptoms was 13 months (range: 1 month to 5 years). The mean modified Japanese Orthopedic Association (mJOA) score was 5.8 preoperatively, 5.5 postoperatively and improved to 7.5 at the last follow-up. A good recovery rate (>50 %) was found in 18 patients, poor recovery (<50 %) in 24 patients, seven remained unchanged and three patients had worsened. In univariate analysis, the statistically significant factors for the recovery rate were the number of OLF levels, CT axial classification (tuberous type), associated OALL and cervical OPLL, T2W cord signal changes, ossification of dura mater, dural tear, and CSF leak. Dural tear and the number of OLF levels were the most predictive factors for the poor outcome on multivariate analysis.

CONCLUSION

Predictors of poor surgical outcomes are the extent of OLF involved and dural tear. The patient improves with rehabilitation despite the immediate postoperative deterioration.

Investigation of the Shared Biomarkers in Heterotopic Ossification Between Ossification of the Ligamentum Flavum and Ankylosing Spondylitis

STUDY DESIGN

Bioinformatics analysis of Gene Expression Omnibus (GEO).

OBJECTIVE

Ossification of the ligamentum flavum (OLF) and ankylosing spondylitis (AS) represent intricate conditions marked by the gradual progression of endochondral ossification. This investigation endeavors to unveil common biomarkers associated with heterotopic ossification and explore the potential molecular regulatory mechanisms.

METHODS

Microarray and RNA-sequencing datasets retrieved from the Gene Expression Omnibus (GEO) repository were harnessed to discern differentially expressed genes (DEGs) within the OLF and AS datasets. Subsequently, Weighted Gene Co-expression Network Analysis (WGCNA) was implemented to pinpoint co-expression modules linked to OLF and AS. Common genes were further subjected to an examination of functional pathway enrichment. Moreover, hub intersection genes were identified using the Least Absolute Shrinkage and Selection Operator (LASSO) regression, followed by an evaluation of diagnostic performance in external OLF and AS cohorts. Lastly, an analysis of immune cell infiltration was conducted to scrutinize the correlation of immune cell presence with shared biomarkers in OLF and AS.

RESULTS

A total of 1353 and 91 Differentially Expressed Genes (DEGs) were identified in OLF and AS, respectively. Using the Weighted Gene Co-expression Network Analysis (WGCNA), 2 modules were found to be notably significant for OLF and AS. The integrative bioinformatic analysis revealed 3 hub genes (MAB21L2, MEGF10, ISLR) as shared risk biomarkers, with MAB21L2 being the central focus. Receiver Operating Characteristic (ROC) analysis exhibited a strong diagnostic potential for these hub genes. Gene Ontology (GO) analysis indicated their involvement in the positive regulation of myoblast proliferation. Notably, MAB21L2 was singled out as the optimal common biomarker for OLF and AS. Furthermore, an analysis of immune infiltration demonstrated a correlation between MAB21L2 expression and changes in immune cells. Activated CD8 T cells were identified as shared differential immune infiltrating cells significantly linked to MAB21L2 in both OLF and AS.

CONCLUSION

This study represents the first instance of identifying MAB21L2 as a prospective diagnostic marker for patients contending with OLF associated with AS. The research results indicate that the ECM-receptor interaction and the cell-cell adhesion may play a role in both disease processes. This newfound knowledge not only enhances our understanding of the pathogenesis behind spinal ligament ossification but also uncovers potential targets for therapeutic interventions.

Open posterior approach versus endoscopic approach for thoracic ligamentum flavum ossification: a systematic review and meta-analysis

BACKGROUND

Thoracic ossification of the ligamentum flavum (TOLF), a rare condition more prevalent in East Asia, is managed through open and endoscopic surgical approaches. Determining the superior surgical option remains unclear. This study assesses the safety and clinical outcomes associated with these approaches in TOLF patients.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a systematic literature search up to August 5, 2023, across PubMed, Scopus, EMBASE, Web of Science, Cochrane, and ClinicalTrials.gov. We included randomized controlled trials and cohort studies reporting complication rates, mJOA (modified Japanese Orthopedic Association) scores, JOA scores, VAS (Visual Analog Scale) scores, or hospitalization duration for both open and endoscopic surgeries in TOLF patients.

RESULTS

We analyzed 37 studies encompassing 1,646 TOLF patients using a random-effects model. Our findings revealed a significant difference in complication rates (overall complication rates: 0.12; 95% CI: 0.07, 0.19; p < 0.01; I2: 69%; quality of evidence: moderate), with lower complication rates in the endoscopy group. However, no significant differences were observed in JOA scores (overall JOA: 8.35; 95% CI: 7.16, 9.54; p = 0.12; I2: 99%; quality of evidence: very low), VAS scores (overall VAS: 1.31; 95% CI: 1.03, 1.59; p = 0.35; I2: 91%; quality of evidence: very low), or hospitalization duration (hospital stay: 10.83 days; 95% CI: 6.86, 14.80; p = 0.35; I2: 91%; quality of evidence: very low) between the open and endoscopic groups.

CONCLUSIONS

This meta-analysis reports lower complication rates and improved postoperative mJOA scores for endoscopic surgery in TOLF patients compared to open surgery. It represents the first comprehensive evaluation of clinical outcomes and safety of different surgical approaches for TOLF patients. Further randomized controlled trials are essential to validate these findings.

CircTMTC1 Mediates Nucleocytoplasmic Translocation of DDX3X to Regulate Osteogenic Differentiation of Human Ligamentum Flavum Cells

OBJECTIVE

This study was aimed to investigate the potential roles of circTMTC1 in the underlying pathophysiological mechanisms of ossification of the ligamentum flavum (OLF).

SUMMARY OF BACKGROUND DATA

OLF is the primary contributor to thoracic spinal stenosis, which may cause severe neurological symptoms. There is a lack of effective medical therapy for OLF available so far because the exact underlying mechanism of OLF has not been fully elucidated. CircRNAs are a special class of noncoding RNAs and have attracted a growing interest of research in various human diseases recently. Therefore, we explored the potential roles of circRNAs in the underlying pathophysiological mechanisms of OLF.

MATERIALS AND METHODS

We performed RNA-seq analysis to investigate the differentially expression profile of circRNAs in osteogenic differentiation of human LF cells, and identified a key circular RNA circTMTC1 functioned in OLF. Subsequently, we performed a series of experiments to investigate the exact molecular and cellular mechanisms in osteogenic differentiation of human ligamentum flavum cells.

RESULTS

CircTMTC1 is significantly upregulated during osteogenic differentiation of human LF cells. Mechanistically, we found that circTMTC1 could interact with the RNA binding protein DDX3X and enhance its nucleocytoplasmic translocation. An increased cytoplasmic level of DDX3X activated the NLRP3 inflammasome pathway and thus promoted osteogenic differentiation of human ligamentum flavum cells.

CONCLUSION

Our findings suggested the circTMTC1-DDX3X-NLRP3 inflammasome signaling plays a pivotal role in osteogenic differentiation of human ligamentum flavum cells, which may provide novel diagnostic and therapeutic strategies for OLF.

Pathogenesis of thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is characterized by ectopic ossification of the ligamentum flavum in the thoracic spine and is considered the main cause of thoracic spinal stenosis and spinal cord disease. Osteoblast specific transcription factor Osterix (Osx) is required for bone formation, and there is no bone formation or ossification without Osx. Surgical intervention is recognized as the only effective method for TOLF treatment with set of complications. However, underlying mechanisms of TOLF are not well understood. This paper summarizes the pathogenesis of TOLF. Some relevant factors have been discussed, such as mechanical stress, genetic susceptibility genes, endocrine and trace element metabolism abnormalities, which may associate with TOLF. More recent studies using proteomics technology and RNA sequencing approach have discovered that some new factors participate in TOLF by upregulation of Osx gene expression including inflammatory factors. TOLF is a unique disease involving multiple factors. On the other hand, studies on TOLF pathogenic mechanism may provide new ideas for finding possible upstream regulatory factors of Osx and further developing novel drugs to stimulate new bone formation to treat osteoporosis.

Prevalence, Radiological, and Pathological Findings of Ossification and Calcification of the Lumbar Spinal Ligamentum Flavum: A Comparative Study with Thoracic Lesions

This study aimed to determine the prevalence of lumbar ligamentum flavum lesions and identify correlations between radiological and pathological findings. We conducted an observational cross-sectional study of 349 patients (lumbar: n = 296, thoracic: n = 39, lumbar and thoracic: n = 14, mean age: 69 ± 12 years, male: 74%) who underwent posterior surgery for thoracolumbar spinal canal stenosis between January 2008 and April 2023 at our hospital.Computed tomography (CT) revealed that the prevalence of ligamentum flavum lesions defined as a high-density area with a CT value of 200 Hounsfield Unit or higher in the lumbar and thoracic spine was 47% (147/310) and 85% (45/53), respectively. CT showed that most patients had radiologically suspected ossification in the lumbar (90%) and thoracic spine (98%) than radiologically suspected calcification. Lumbar lesions were thinner than the thoracic lesions (2.5 vs 3.7 mm, p < 0.01). Pathological examinations were performed in specimens collected from 34 cases (lumbar: n = 13, thoracic: n = 21), and ossification was found in 62% (8/13) and 95% (20/21) of lumbar and thoracic lesions (p = 0.02), respectively. Lastly, ossification was confirmed pathologically in 72% (8/11) and 95% (19/20) of lumbar and thoracic lesions that showed ossification on imaging (p = 0.13), respectively. The literature review revealed that the prevalence of the lumbar ligamentum flavum lesions varied from 1.5 to 35% and the patient population was mostly asymptomatic.Collectively, we found that the prevalence of lumbar ligamentum flavum lesions in symptomatic patients was greater than previously reported. Histologically confirmed ossification was less common in lumbar lesions than in thoracic lesions.

Dural Injury During Spinal Surgery and Postoperative Cerebrospinal Fluid Leakage: A Single-Center Experience

BACKGROUND

The incidence of dural injury during spinal surgery and postoperative cerebrospinal fluid leakage varies between studies. We examined these rates in our institution.

METHODS

Among 4014 patients who underwent a spinal operation between January 2012 and February 2020, 176 experienced an intraoperative dural injury (176 of 4014 cases, 4.3%). Among these, 22 (22 of 176 cases, 12.5%) developed postoperative cerebrospinal fluid leakage.

RESULTS

The cause of dural injury was identified in 74 of 176 patients (42%). The rates of dural injury associated with thoracic, cervical, and lumbar operations were 7.8% (25 of 321 cases), 3.2% (19 of 602 cases), and 4.3% (132 of 3091 cases), respectively. Corresponding rates of cerebrospinal fluid leakage were 28% (seven of 25 cases), 5.3% (one of 19 cases), and 11% (14 of 132 cases), respectively. Most patients who experienced cerebrospinal fluid leakage recovered with bed rest; however, cerebral hemorrhage occurred in two patients.

CONCLUSIONS

Although it was difficult to identify the cause of dural injury in more than half of patients, suturing the dura and using polyglycolic acid mesh with fibrin glue was effective. No patients required reoperation, even those who developed cerebrospinal fluid leakage.

Diagnosis and Management of Thoracic Myelopathy

Thoracic myelopathy can be a challenging condition to diagnose and treat. Successful outcomes depend on early recondition of the pathology and appropriate surgical referral in cases of progressive neurologic deterioration. The thoracic cord is tethered in kyphosis by the dentate ligaments and contains a tenuous blood supply. These conditions make the thoracic cord particularly susceptible to external compression and ischemic damage. Careful preoperative planning with specific attention to the location and source of thoracic stenosis is critical to successful decompression and complication avoidance. The purpose of this discussion is to outline the common sources of thoracic myelopathy and current recommendations regarding diagnosis and management. The review concludes with an overview of the most up-to-date literature regarding clinical outcomes.

Revealing the novel metabolism-related genes in the ossification of the ligamentum flavum based on whole transcriptomic data

Backgrounds

The ossification of the ligamentum flavum (OLF) is one of the major causes of thoracic myelopathy. Previous studies indicated there might be a potential link between metabolic disorder and pathogenesis of OLF. The aim of this study was to determine the potential role of metabolic disorder in the pathogenesis of OLF using the strict bioinformatic workflow for metabolism-related genes and experimental validation.

Methods

A series of bioinformatic approaches based on metabolism-related genes were conducted to compare the metabolism score between OLF tissues and normal ligamentum flavum (LF) tissues using the single sample gene set enrichment analysis. The OLF-related and metabolism-related differentially expressed genes (OMDEGs) were screened out, and the biological functions of OMDEGs were explored, including the Gene Ontology enrichment analysis, Kyoto Encyclopedia of Genes and Genomes enrichment analysis, and protein-protein interaction. The competing endogenous RNA (ceRNA) network based on pairs of miRNA-hub OMDEGs was constructed. The correlation analysis was conducted to explore the potential relationship between metabolic disorder and immunity abnormality in OLF. In the end, the cell experiments were performed to validate the roles of GBE1 and TNF-α in the osteogenic differentiation of LF cells.

Results

There was a significant difference of metabolism score between OLF tissues and normal LF tissues. Forty-nine OMDEGs were screened out and their biological functions were determined. The ceRNA network containing three hub OMDEGs and five differentially expressed miRNAs (DEmiRNAs) was built. The correlation analysis between hub OMDEGs and OLF-related infiltrating immune cells indicated that metabolic disorder might contribute to the OLF via altering the local immune status of LF tissues. The cell experiments determined the important roles of GBE1 expression and TNF-α in the osteogenic differentiation of LF cells.

Conclusions

This research, for the first time, preliminarily illustrated the vital role of metabolic disorder in the pathogenesis of OLF using strict bioinformatic algorithms and experimental validation for metabolism-related genes, which could provide new insights for investigating disease mechanism and screening effective therapeutic targets of OLF in the future.

CTSD upregulation as a key driver of spinal ligament abnormalities in spinal stenosis

Spinal stenosis (SS) is frequently caused by spinal ligament abnormalities, such as ossification and hypertrophy, which narrow the spinal canal and compress the spinal cord or nerve roots, leading to myelopathy or sciatic symptoms; however, the underlying pathological mechanism is poorly understood, hampering the development of effective nonsurgical treatments. Our study aims to investigate the role of co-expression hub genes in patients with spinal ligament ossification and hypertrophy. To achieve this, we conducted an integrated analysis by combining RNA-seq data of ossification of the posterior longitudinal ligament (OPLL) and microarray profiles of hypertrophy of the ligamentum flavum (HLF), consistently pinpointing CTSD as an upregulated hub gene in both OPLL and HLF. Subsequent RT-qPCR and IHC assessments confirmed the heightened expression of CTSD in human OPLL, ossification of the ligamentum flavum (OLF), and HLF samples. We observed an increase in CTSD expression in human PLL and LF primary cells during osteogenic differentiation, as indicated by western blotting (WB). To assess CTSD's impact on osteogenic differentiation, we manipulated its expression levels in human PLL and LF primary cells using siRNAs and lentivirus, as demonstrated by WB, ALP staining, and ARS. Our findings showed that suppressing CTSD hindered the osteogenic differentiation potential of PLL and LF cells, while overexpressing CTSD activated osteogenic differentiation. These findings identify CTSD as a potential therapeutic target for treating spinal stenosis associated with spinal ligament abnormalities.

Degenerative Thoracic Myelopathy: A Scoping Review of Epidemiology, Genetics, and Pathogenesis

STUDY DESIGN

Literature Review.

OBJECTIVE

Myelopathy affecting the thoracic spinal cord can arise secondary to several aetiologies which have similar presentation and management. Consequently, there are many uncertainties in this area, including optimal terminology and definitions. Recent collaborative cervical spinal research has led to the proposal and subsequent community adoption of the name degenerative cervical myelopathy(DCM), which has facilitated the establishment of internationally-agreed research priorities for DCM. We put forward the case for the introduction of the term degenerative thoracic myelopathy(DTM) and degenerative spinal myelopathy(DSM) as an umbrella term for both DCM and DTM.

METHODS

Following PRISMA guidelines, a systematic literature search was performed to identify degenerative thoracic myelopathy literature in Embase and MEDLINE.

RESULTS

Conditions encompassed within DTM include thoracic spondylotic myelopathy, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, calcification of ligaments, hypertrophy of ligaments, degenerative disc disease, thoracic osteoarthritis, intervertebral disc herniation, and posterior osteophytosis. The classic presentation includes girdle pain, gait disturbance, leg weakness, sensory disturbance, and bladder or bowel dysfunction, often with associated back pain. Surgical management is typically favoured with post-surgical outcomes dependent on many factors, including the causative pathology, and presence of additional stenosis.

CONCLUSION

The clinical entities encompassed by the term DTM are interrelated, can manifest concurrently, and present similarly. Building on the consensus adoption of DCM in the cervical spine and the recent proposal of degenerative cervical radiculopathy(DCR), extending this common nomenclature framework to the terms degenerative spinal myelopathy and degenerative thoracic myelopathy will help improve recognition and communication.

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.

Distinctive Characteristics of Thoracolumbar Junction Region Stenosis

STUDY DESIGN

Retrospective case series and systemic literature meta-analysis.

BACKGROUND

Thoracolumbar junction region stenosis produces spinal cord compression just above the conus and may manifest with symptoms that are not typical of either thoracic myelopathy or neurogenic claudication from lumbar stenosis.

OBJECTIVE

As few studies describe its specific pattern of presenting symptoms and neurological deficits, this investigation was designed to improve understanding of this pathology.

METHODS

A retrospective review assessed surgically treated cases of T10-L1 degenerative stenosis. Clinical outcomes were evaluated with the thoracic Japanese Orthopedic Association score. In addition, a systematic review and meta-analysis was performed in accordance with guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

Of 1069 patients undergoing laminectomy at 1477 levels, 31 patients (16M/15F) were treated at T10-L1 a mean age 64.4 (SD=11.8). Patients complained of lower extremity numbness in 29/31 (94%), urinary dysfunction 11/31 (35%), and back pain 11/31 (35%). All complained about gait difficulty and objective motor deficits were detected in 24 of 31 (77%). Weakness was most often seen in foot dorsiflexion 22/31 (71%). Deep tendon reflexes were increased in 10 (32%), decreased in 11 (35%), and normal 10 (32%); the Babinski sign was present 8/31 (26%). Mean thoracic Japanese Orthopedic Association scores improved from 6.4 (SD=1.8) to 8.4 (SD=1.8) ( P <0.00001). Gait subjectively improved in 27/31 (87%) numbness improved in 26/30 (87%); but urinary function improved in only 4/11 (45%).

CONCLUSIONS

Thoracolumbar junction stenosis produces distinctive neurological findings characterized by lower extremity numbness, weakness particularly in foot dorsiflexion, urinary dysfunction, and inconsistent reflex changes, a neurological pattern stemming from epiconus level compression and the myelomeres for the L5 roots. Surgery results in significant clinical improvement, with numbness and gait improving more than urinary dysfunction. Many patients with thoracolumbar junction stenosis are initially misdiagnosed as being symptomatic from lumbar stenosis, thus delaying definitive surgery.

Safety and efficacy of one-hole split endoscope technique for surgical treatment of thoracic ossification of the ligamentum flavum

Surgical intervention is typically recommended for thoracic ossification of the ligamentum flavum (TOLF). This study aimed to evaluate the efficacy and safety of a novel non-coaxial one-hole split endoscope (OSE) technique for treating TOLF. We performed OSE procedure on 13 patients with TOLF from June 2022 to July 2023. The mean operative time was 117.5 ± 15.4 min. VAS scores for lower limbs decreased from 6.5 ± 0.8 preoperative to 1.6 ± 0.4 at the last follow-up (P < 0.001). ODI scores improved from 62.4 ± 5.7 preoperative to 18.6 ± 2.2 at the last follow-up (P < 0.001), and mJOA scores increased from 5.1 ± 1.6 preoperative to 8.4 ± 1.5 at the latest follow-up (P < 0.001). All patients achieved ASIA scale grade D or E at the final follow-up, except for two patients remained residual limb numbness. None of the thirteen patients suffered from severe perioperative complications. The OSE technique proves to be a safe and effective procedure for treating TOLF or even with dura mater ossification, characterized by minimal surgical trauma, relatively smooth learning curve and flexible operation.

The Symptomatic Calcification and Ossification of the Ligamentum Flavum in the Spine: Our Experience and Review of the Literature

INTRODUCTION

We report our experience regarding the clinical features and pathological findings of the calcification of the ligamentum flavum (CLF) and ossification of the ligamentum flavum (OLF) in the spine. In addition, we reviewed the previous studies on CLF and OLF to enhance the understanding of these conditions.

MATERIALS AND METHODS

We compared the clinical, radiological, and histopathological features of CLF and OLF.

RESULTS

In CLF, a computed tomography (CT) scan showed egg-shaped or speck-like calcification in the ligamentum flavum. Magnetic resonance (MR) imaging demonstrated spinal cord compression due to a thickened ligamentum flavum, which appeared as a low-intensity mass. Pathological findings demonstrated fused islands of calcification resembling sand-like calcification. In OLF, CT showed beak-like ossification extending into the intervertebral foramen. MR imaging demonstrated spinal cord compression by a low-intensity mass. Pathological findings revealed laminar ossification of LF with chondrocytes near the calcification and laminar hyaline cartilage.

CONCLUSIONS

CLF and OLF appear to be distinct entities based on their clinical, neuroradiological, histopathological, and pathogenetic features. We suggest that the causes of CLF include both metabolic and dystrophic factors, while the pathogenesis of OLF is characterized by enchondral ossification induced by a genetic cascade triggered by shearing/tension stress.

Interleukin-17A Promotes Proliferation and Osteogenic Differentiation of Human Ligamentum Flavum Cells Through Regulation of β-Catenin Signaling

STUDY DESIGN

A basic experimental study.

OBJECTIVE

To elucidate the role and mechanism of interleukin (IL)-17A in thoracic ossification of the ligamentum flavum (TOLF).

SUMMARY OF BACKGROUND DATA

TOLF is characterized by the replacement of the thoracic ligamentum flavum with ossified tissue and is one of the leading causes of thoracic spinal stenosis. IL-17A is an important member of the IL-17 family that has received widespread attention for its key contributions to the regulation of bone metabolism and heterotopic ossification. However, it is unclear whether IL-17A is involved in TOLF.

MATERIALS AND METHODS

Cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine staining were performed to assess the proliferation of ligamentum flavum cells (LFCs). Alkaline phosphatase activity assay, Alizarin red staining, and protein level expression of osteogenic-related genes were used to evaluate the osteogenic differentiation potential of LFCs. The effect of IL-17A on the proliferation and osteogenic differentiation of LFCs was further assessed after silencing β-catenin by transfection with small interfering RNA. In addition, the possible source of IL-17A was further demonstrated by coculture assays of T helper 17 (Th17) cells with LFCs. Student t test was used for comparisons between groups, and the one-way analysis of variance, followed by the Tukey post hoc test, was used for comparison of more than two groups.

RESULTS

IL-17A was elevated in TOLF tissue compared with normal ligamentum flavum. IL-17A stimulation promoted the proliferation and osteogenic differentiation of LFCs derived from patients with TOLF. We found that IL-17A promoted the proliferation and osteogenic differentiation of LFCs by regulating the β-catenin signaling. Coculture of Th17 cells with LFCs enhanced β-catenin signaling-mediated proliferation and osteogenic differentiation of LFCs. However, these effects were markedly attenuated after the neutralization of IL-17A.

CONCLUSIONS

This is the first work we are aware of to highlight the importance of IL-17A in TOLF. IL-17A secreted by Th17 cells in the ligamentum flavum may be involved in the ossification of the microenvironment by regulating β-catenin signaling to promote the proliferation and osteogenic differentiation of LFCs.

The biomechanical effect of different types of ossification of the ligamentum flavum on the spinal cord during cervical dynamic activities

Ossification of the ligamentum flavum (OLF) is thought to be an influential etiology of myelopathy, as thickened ligamentum flavum causes the stenosis of the vertebral canal, which could subsequently compress the spinal cord. Unfortunately, there was little information available on the effects of cervical OLF on spinal cord compression, such as the relationship between the progression of cervical OLF and nervous system symptoms during dynamic cervical spine activities. In this research, a finite element model of C1-C7 including the spinal cord featured by dynamic fluid-structure interaction was reconstructed and utilized to analyze how different types of cervical OLF affect principal strain and stress distribution in spinal cord during spinal activities towards six directions. For patients with cervical OLF, cervical extension induces higher stress within the spinal cord among all directions. From the perspective of biomechanics, extension leads to stress concentration in the lateral corticospinal tracts or the posterior of gray matter. Low energy damage to the spinal cord would be caused by the high and fluctuating stresses during cervical movements to the affected side for patients with unilateral OLF at lower grades.

Prevalence and distribution of ossification of the ligamenta flava in a 16th-18th century skeletal population sample from Poland

OBJECTIVE

This study aimed to determine the prevalence of the ossification of the ligamenta flava (OLF) among skeletal remains from Poland.

MATERIALS AND METHODS

124 skeletons aged 25 years and older were analyzed. The presence and size of OLF were observed macroscopically. OLF was recorded at the cranial and caudal attachment sites of each vertebra. The following factors were analyzed: age at death, sex, and presence of other spondyloarthropathies.

RESULTS

The crude prevalence of OLF in the analyzed series was 68.55 %. OLF was located most frequently in the lower thoracic spine. A statistically significant relationship was observed between the presence of OLF and age at death. OLF coincided with degenerative spondyloarthropathies of the thoracolumbar spine.

CONCLUSIONS

The results of this study indicate that OLF was not a rare condition in past populations of European ancestry. Analysis of OLF prevalence in skeletal materials can contribute to reconstruction of the conditions and lifestyles of past people.

SIGNIFICANCE

This study shed new light on the prevalence of OLF and provides information on the variability of OLF in past European populations. The evaluation of the prevalence of OLF represents an important contribution to the field of paleopathology in understanding disease changes in prehistoric and historic human populations.

LIMITATIONS

The analyzed material came from unknown populations without demographic data. Sex and age at death were assessed using standard anthropological methods.

SUGGESTIONS FOR FURTHER RESEARCH

It is important to understand the influence of sociocultural factors and physical activity patterns on the development of OLF.

Aggravation of Ossified Ligamentum Flavum Lesion Is Associated With the Degree of Obesity

STUDY DESIGN

Retrospective cross-sectional study.

OBJECTIVES

There is insufficient data on the clinical features of ossification of the ligamentum flavum (OLF) of the thoracic spine and the risk of progression of ossified lesions. The link between obesity and ossification of the posterior longitudinal ligament (OPLL), which frequently coexists with OLF, has been demonstrated. However, the link between obesity and OLF has not been recognized. We aimed to determine the prevalence of obesity in thoracic OLF and whether the severity of OLF is associated with the degree of obesity.

METHODS

A total of 204 symptomatic Japanese subjects with thoracic OLF and 136 subjects without spinal ligament ossification as controls were included. OLF subjects were divided into 3 groups: 1) localized OLF (OLF <2-intervertebral regions); 2) multilevel OLF (OLF ≥3-intervertebral regions); and 3) OLF + OPLL. The severity of OLF was quantified using the OLF index using computed tomography imaging of the entire spine.

RESULTS

The proportion of severely obese subjects (BMI ≥ 30 kg/m2) was significantly higher both in the multilevel OLF group (25.5%) and the OLF + OPLL group (44.3%) than in the localized OLF group (3.6%) and the control group (1.4%) (P < 0.01). BMI, age, and coexistence of cervical OPLL and lumbar OLF were associated with thoracic OLF index in the multiple regression analysis.

CONCLUSIONS

Our findings demonstrated that obesity is a distinct feature of multilevel OLF in the thoracic spine and that the severity of OLF is associated with the degree of obesity.

CT-based radiographic measurements and effectiveness estimates of full-endoscopic surgery in thoracic myelopathy caused by ossification of ligamentum flavum

BACKGROUND

Evaluate the effectiveness of posterior percutaneous full-endoscopic technique for patients with thoracic myelopathy caused by ossification of ligamentum flavum (TOLF).

METHODS

A prospective study was conducted for 16 patients with TOLF, who were treated with posterior endoscopic technique from 2017 to 2019. The sagittal and cross-sectional CT images are used to measure the area of ossified ligamentum and evaluate the decompression of surgery, respectively. The effectiveness was evaluated with visual analog scale (VAS), modified Japanese Orthopedic Association scale (mJOA), The Oswestry Disability Index (ODI), and Macnab efficacy evaluation.

RESULTS

The average area of TOLF on sagittal and cross-sectional CT images in the 16 patients was (116.62 ± 32.72) mm² and (141.59 ± 27.25) mm² preoperatively, (15.99 ± 12.54) mm² and (11.72 ± 8.64) mm² at 3 days after the operation, (16.78 ± 11.49) mm² and (10.82 ± 7.57) mm² postoperative 1 year, respectively. The invasive proportion of spinal canal at preoperative sagittal and cross-sectional CT images was (48.10 ± 10.04) % and (57.58 ± 11.37) %, which decreased to (6.83 ± 4.48) % and (4.40 ± 3.01) % at the final follow-up. The average score of mJOA, VAS and ODI improved. The excellent and good rate was 87.50% according to Macnab evaluation. Compared with preoperative, differences in areas of TOLF, proportions of spinal canal, and clinical assessments of postoperative 3 days and 1 year were all statistically significant. Two cases of dural tear were observed.

CONCLUSION

Endoscopic surgery has a good clinical effect on TOLF, which has the advantage of less trauma to the paraspinal muscles and no impact on the spinal structure. The CT-based radiographic measurements can quantitatively evaluate the degree of spinal canal stenosis in TOLF.

Thoracic Myelopathy in Ossified Ligamentum Flavum: Surgical Management and Long-Term Outcome Following 2 Different Techniques of Surgical Decompression

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Thoracic ossified ligamentum flavum (TOLF) has been reported to present with varying degrees of neuro-deficit and multiple factors have been purported to affect its outcome. Purpose of study was to analyze factors affecting outcome and impact of ultrasonic osteotome (UO).

METHODS

We retrospectively reviewed patients treated for thoracic myelopathy secondary to OLF between 2010 and 2017. 77 patients with complete clinico-radiological records and 2 years follow-up were included. Initial 45 patients, conventional high-speed burr (HSB-group A) was used for decompression. In others, UO was used in combination with HSB (group B). Myelopathy was graded using modified Japanese orthopaedic association grading pre-operatively and each postoperative visit. At final follow-up, recovery rate was calculated. Radiological details including location, morphology, dural ossification, signal change and spinal ossifications were recorded.

RESULTS

Mean mJOA at presentation and final follow-up were 4.3±1.8 and 7.6±1.9 respectively (p = 0.001). HRR was 49.9±23 at final follow-up. A significant reduction in dural tear (12.5%; 29%) and surgical time (125.8±49.5; 189.4±52.5) were observed in group B (p = 0.00). However, there was no statistically significant difference (p = 0.18) in recovery rates between groups A (44.8±26.1) and B (52.8±24.3). Symptom duration (p = 0.00), severity of myelopathy (p = 0.04) and cord signal changes on MRI (p = 0.02) were important predictors of outcome.

CONCLUSION

Use of UO significantly reduced operative time and dural tears, although resulted in similar recovery rate as compared with HSB. Pre-operative severity of myelopathy, symptom duration and presence of cord signal change were the most significant predictors of outcome.

Prevalence, diagnosis, and impact on clinical outcomes of dural ossification in the thoracic ossification of the ligamentum flavum: a systematic review

STUDY DESIGN

Systematic review.

BACKGROUND CONTEXT

Thoracic ossification of the ligamentum flavum (TOLF) has become the principal cause of thoracic spinal stenosis. Dural ossification (DO) was a common clinical feature accompanying with TOLF. However, on account of the rarity, we know little about the DO in TOLF so far.

PURPOSE

This study was conducted to elucidate the prevalence, diagnostic measures, and impact on the clinical outcomes of DO in TOLF by integrating the existing evidence.

METHODS

PubMed, Embase, and Cochrane Database were comprehensively searched for studies relevant to the prevalence, diagnostic measures, or impact on the clinical outcomes of DO in TOLF. All retrieved studies meeting the inclusion and criterion were included into this systematic review.

RESULTS

The prevalence of DO in TOLF treated surgically was 27% (281/1046), ranging from 11 to 67%. Eight diagnostic measures have been put forward to predict the DO in TOLF using the CT or MRI modalities, including "tram track sign", "comma sign", "bridge sign", "banner cloud sign", "T2 ring sign", TOLF-DO grading system, CSAOR grading system, and CCAR grading system. DO did not affect the neurological recovery of TOLF patients treated with the laminectomy. The rate of dural tear or CSF leakage in TOLF patients with DO was approximately 83% (149/180).

CONCLUSION

The prevalence of DO in TOLF treated surgically was 27%. Eight diagnostic measures have been put forward to predict the DO in TOLF. DO did not affect the neurological recovery of TOLF treated with laminectomy but was associated with high risk of complications.

Review of Basic Research about Ossification of the Spinal Ligaments Focusing on Animal Models

Ossification of the posterior longitudinal ligament (OPLL) is a heterotopic ossification that may cause spinal cord compression. With the recent development of computed tomography (CT) imaging, it is known that patients with OPLL often have complications related to ossification of other spinal ligaments, and OPLL is now considered part of ossification of the spinal ligaments (OSL). OSL is known to be a multifactorial disease with associated genetic and environmental factors, but its pathophysiology has not been clearly elucidated. To elucidate the pathophysiology of OSL and develop novel therapeutic strategies, clinically relevant and validated animal models are needed. In this review, we focus on animal models that have been reported to date and discuss their pathophysiology and clinical relevance. The purpose of this review is to summarize the usefulness and problems of existing animal models and to help further the development of basic research on OSL.

The Gantry Crane Technique: A Novel Technique for Treating Severe Thoracic Spinal Stenosis and Myelopathy Caused by Ossification of the Ligamentum Flavum and Preliminary Clinical Results

STUDY DESIGN

Retrospective single-arm study.

OBJECTIVE

To propose a novel technique named the gantry crane technique for treating severe thoracic spinal stenosis and myelopathy caused by thoracic ossification of the ligamentum flavum (TOLF) and investigate its clinical results.

METHODS

From June 2017 to January 2019, 18 patients presenting with severe spinal stenosis and myelopathy caused by TOLF were included in our study. All patients were treated with gantry crane technique, pre-operative JOA score, as well as 3 days-, 3 months-, 6 months-, 12 months-, 24 months after operation, and Hirabayashi recovery rate were reported. Pre- and post-operative image were utilized for the assessment of post-operative effect. Peri-operative complications were recorded to assess the safety of the gantry crane technique.

RESULTS

The JOA score increased from 10.56 ± 3.76 preoperatively to 12.94 ± 3.33, 13.56 ± 3.48, 13.94 ± 3.32, 14.17 ± 3.70 and 14.06 ± 3.54 in 3 days, 3 months, 6 months, 12 months and 24 months after surgery, respectively. The post-operative JOA scores were improved with statistical significance at the level of P < 0.05. The recovery rate was (39.09 ± 33.85) %, (51.35 ± 42.60) %, (55.79 ± 36.10) %, (64.98 ± 29.24) % and (60.98 ± 35.96) % for 3 days, 3 months, 6 months, 12 months and 24 months after surgery, respectively. There were 2 cases of SSI (surgical site infection), 1 case of NI (neurovascular injury) and 1 case of cerebrospinal fluid (CSF) leakage.

CONCLUSIONS

This study highlights a safe and effective technique, the gantry crane technique, for treating severe thoracic spinal stenosis and myelopathy caused by TOLF.

Comparison of Surgical Results of the Bridge Crane Technique Versus Laminectomy for the Treatment of Thoracic Myelopathy Caused by Ossification of the Ligamentum Flavum

STUDY DESIGN

A retrospective study.

OBJECTIVES

This study aimed to evaluate the safety and effectiveness of the bridge crane technique versus laminectomy for the treatment of thoracic myelopathy caused by ossification of the ligamentum flavum (OLF).

METHODS

Totally 41 patients who underwent surgical decompression due to thoracic OLF from May 2017 to June 2018 in our institution were enrolled in this study and were divided into group BG (bridge crane technique, n = 19) and group L (laminoectomy, n = 22). Demographic data was collected from medical records and the modified Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the neurological outcomes during the follow-up. Surgery-related complications were analyzed.

RESULTS

The mean duration of follow-up was comparable between group BG (19.4 ± 1.5 months) and group L (19.6 ± 1.4 months). No statistical differences were observed between two groups in terms of gender, age, duration of symptoms, preoperative occupying rate, involved levels, operation time, intraoperative blood loss, and complications. The JOA score significantly increased at the final follow-up in both groups. However, patients in group BG had higher JOA score and recovery rate (P < 0.05). Four patients in group L experienced complications, including 3 cerebrospinal fluid (CSF) leakage and one postoperative hematoma. Only one patient in group BG had CSF leakage.

CONCLUSION

The results of this study suggested that bridge crane technique may be relatively safe and effective for patients with symptomatic thoracic OLF with more satisfactory clinical improvement. However, high-quality studies are still required to validate the results of this study.

Zoning laminectomy for the treatment of ossification of the thoracic ligamentum flavum

OBJECTIVE

Spinal cord injury is a common occurrence during spinal surgery. In this study, we proposed a zoning laminectomy, which could reduce the incidence of nerve injury. We also discussed the safety and clinical efficacy of the zoning laminectomy for thoracic ossification of the ligamentum flavum (TOLF).

METHODS

Forty-five patients with TOLF who underwent zoning laminectomy from October 2016 to February 2020 were included in the retrospective analysis. The Japan Orthopedic Association (JOA) score was used to evaluate clinical outcomes. Meanwhile, the occurrence of complications was recorded.

RESULTS

All 45 patients underwent the operation successfully, and the mean follow-up period was 25.3 months, the mean operation time was 160.2 min, the average blood loss was 474.2 ml, and the average hospital time was 8.0 days. At the final evaluation, the JOA score was significantly higher than the preoperative JOA score (P < 0.001) and the overall recovery rate of the JOA score averaged 69.6%. Seventeen patients were graded as excellent, twenty-six as good, and two as fair. The complications included dural tears in nine patients (20.0%), cerebrospinal fluid leakage in seven patients (15.6%), deep infection in one patient (2.2%), and epidural hematoma in one patient (2.2%). All patients recovered well after treatment. Besides, there was no neurological deterioration and thoracic kyphosis occurred.

CONCLUSIONS

Zoning laminectomy adopts a phased resection from "safe zone" to "danger zone" and defines the safe removal range of the lamina, which reduces the risks of spinal cord injury caused by instrument manipulation. Therefore, it is a safe and effective surgical option.

Clinical progression of ossification of the ligamentum flavum in thoracic spine: a 10- to 11-year follow-up study

BACKGROUND

Thoracic ossification of ligamentum flavum (TOLF) can be asymptomatic and progress insidiously. But, long-term follow-up results of clinical progression of TOLF are still unknown.

METHODS

The clinical progression of 81 patients with TOLF at our center, followed for 10 to 11 (mean, 10.3) years from May 2010 to November 2021, were analyzed. Among them, 51 patients with thoracic myelopathy were caused by single- or multi-segment TOLF, and received partial TOLF resection (30 patients) or total TOLF resection (21 patients). The remaining 30 patients showed TOLF on imaging examinations, but TOLF was not the responsible compressing factor causing myelopathy and with no TOLF resection. The mJOA score (total 11 scores) and spinal operation were used to evaluate the clinical progression at follow-up.

RESULTS

During the 10- to 11-year follow-up of 81 TOLF patients, 71 (87.7%) had no deterioration of neurological function, and 10 (12.3%) patients had deterioration of neurological function and had another spinal operation, including only 4 (4.9%) suffered thoracic myelopathy caused by the progression of TOLF; 6 (7.4%) for other spinal diseases: 2 (2.5%) had fall damage and acute spinal cord injury at the TOLF level; 2 (2.5%) had thoracic myelopathy caused by ossification of posterior longitudinal ligament (OPLL); 2 (2.5%) had cervical spondylosis and received cervical operation.

CONCLUSIONS

Most TOLF (87.7%) patients had no clinical progression and received no reoperations for TOLF in the ten-year dimension (mean, 10.3 years). Narrow spinal canal for TOLF increases the risk of traumatic paraplegia.

Young thoracic vertebra diffuse idiopathic skeletal hyperostosis with Scheuermann disease: A case report

BACKGROUND

Diffuse idiopathic skeletal hyperostosis (DISH) is a disorder characterised by the calcification and ossification of ligaments and entheses. It is a frequent occurrence in elderly males, but rarely encountered in younger individuals.

CASE SUMMARY

A 24-year-old male was admitted to the hospital due to low back pain accompanied with numbness in both lower limbs for 10 d. Upon clinical examination and imaging tests, the patient was diagnosed with DISH with Scheuermann disease and thoracic spinal stenosis. Before the operation and medical treatment, the patient had hypoesthesia of the skin below the xiphoid process. Afterward, a standard laminectomy was conducted using ultrasonic bone curette and internal fixation was applied. Subsequently, the patient was given corticosteroids, neurotrophic drugs, hyperbaric oxygen and electric stimulation. As a result of the treatment, the patient’s sensory level decreased to the navel level and there was no major change in the muscle strength of the lower limbs. During follow-up, the patient’s skin sensation has returned to normal.

CONCLUSION

This case is a rare instance of DISH co-existing with Scheuermann’s disease in a young adult. This provides a valuable reference point for spine surgeons, as DISH is more commonly observed in middle-aged and elder adults.

Lumbar ossification of the ligamentum flavum reflects a strong ossification tendency of the entire spinal ligament

Patients with ossification of the ligamentum flavum (OLF) in the lumbar spine may be at high risk of developing concomitant ossification of the entire spinal ligament, but the etiology remains unclear. We investigated the propensity for spinal ligament ossification in asymptomatic subjects with lumbar OLF using the data of 595 Japanese individuals receiving medical check-ups, including computed tomography (CT) scanning. The severity of OLF (total number of intervertebral segments with OLF) of the entire spine on CT was quantified using an OLF index. Subjects with OLF were grouped according to this index: localized OLF (n = 138), intermediate OLF (n = 70), and extensive OLF (n = 31). The proportion of subjects with lumbar OLF increased with increasing OLF index (localized 13.7%, intermediate 41.4%, and extensive 70.9%). Multiple regression analysis found that lumbar OLF index was associated with thoracic OLF index, and co-existence of ossification of the posterior longitudinal ligament (OPLL) of the thoracic and lumbar spine. This study showed that subjects with more multilevel lumbar OLF were more likely to develop multilevel thoracic OLF and to have coexisting OPLL. Patients with lumbar OLF may be a distinctive subgroup with a strong tendency to ossification of the entire spinal ligament.

Repeated Recurrence of Ligamentum Flavum Ossification After Posterior Spinal Surgery: A Case Report and Literature Review

CASE

Patients with myelopathy due to narrowing of the spinal canal with ossification of the ligamentum flavum (OLF) generally require surgical intervention, but surgical methods for OLF remain controversial. We discuss our experience regarding posterior fusion surgery with instrumentation for a patient with recurrent OLF at the same level after decompression surgery as well as describe the preoperative and postoperative course of this rare case.

CONCLUSION

Posterior decompression and fusion surgery is recommended as revision surgery for recurrent OLF at the same level after decompression surgery. A detailed surgical planning should be developed before surgery.

Strong relationship between dyslipidemia and the ectopic ossification of the spinal ligaments

Obesity and metabolic disturbances are prevalent in ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF); however, the involvement of dyslipidemia (DL) in OPLL/OLF remains uncertain. We investigated the association between dyslipidemia and OPLL/OLF using a dataset of 458 individuals receiving health screening tests, including computed tomography. Subjects were grouped according to the presence or location of OPLL/OLF: controls (no OPLL/OLF, n = 230), OLF (n = 167), cervical OPLL (n = 28), and thoracic OPLL (n = 33). They were also grouped according to the presence of dyslipidemia (DL[+], n = 215; DL[-], n = 243). The proportion of dyslipidemia in the OLF and OPLL groups was 1.6-2.2 times higher than that in the control group. The proportion of OLF and OPLL in the DL(+) group was significantly higher than that in the DL(-) group (OLF, 43% vs. 29%; cervical OPLL, 14.4% vs. 3.2%; thoracic OPLL, 11.1% vs. 3.7%). Multivariate logistic regression analysis showed an association between all ossification types and dyslipidemia. This study demonstrated an association of dyslipidemia with OPLL/OLF; further investigation on the causal relationship between dyslipidemia and ectopic spinal ligament ossification is warranted to develop a therapeutic intervention for OPLL/OLF.

Significance of body mass index on thoracic ossification of the ligamentum flavum in Chinese population

PURPOSE

To investigate the risk factors for thoracic ossification of the ligamentum flavum (TOLF), especially the relationship between BMI and TOLF.

METHODS

A total of 856 individuals consisting of 326 controls without ossification of spinal ligaments and 530 TOLF inpatients who underwent thoracic spine decompression surgery at our hospital between January 2013 and September 2020 were included. All subjects were classified into 4 grades: Grade 0) control; Grade 1) single-segment TOLF; Grade 2) multi-segment TOLF; and Grade 3) TOLF combined thoracic ossification of the posterior longitudinal ligament (T-OPLL). Logistic regression analysis was performed to identify the risk factors for TOLF. The TOLF index was calculated to assess the severity of TOLF, and its relationship with BMI was investigated by correlation analysis.

RESULTS

Overall, TOLF patients are most numerous in the 50-59 age group. Age and gender were considered as independent risk factors for Grades 1 and 2. BMI was identified as an independent risk factor for TOLF. Furthermore, BMI was significantly higher in Grade 1 (26.1 VS 24.5 kg/m², P = 0.0001), Grade 2 (28.2 VS 24.5 kg/m², P < 0.0001), and Grade 3 (29.1 VS 24.5 kg/m², P < 0.0001) than Grade 0. Notably, in TOLF patients without combined T-OPLL, BMI was positively correlated with TOLF index, while BMI was negatively correlated with age in younger individuals.

CONCLUSION

BMI is a crucial risk factor for TOLF. It highlights the necessity of close follow-up of asymptomatic TOLF patients with high BMI to detect and treat their TOLF progression promptly.

Fibrotic and inflammatory characteristics of epidural fat adjacent to the ossification area in patients with ossification of the ligament flavum

Objectives

To observe histological and inflammatory characteristics of epidural fat (EF) adjacent to the ossification area in patients with ossification of the thoracic ligament flavum (TOLF) and provide a preliminary research basis for investigating the impact of the EF on OLF.

Methods

Samples of EF and autologous subcutaneous adipose tissue (SCAT) from TOLF patients (n = 26) and non-TOLF patients (n = 23) were harvested during posterior thoracic spine surgery. Adipocyte size and fibrosis were measured by histology. Vascularization and inflammatory cell infiltration were evaluated by immunohistochemical staining. Adipogenesis-related genes were assessed by real-time quantitative PCR. Conditioned media from cultured EF were evaluated via enzyme-linked immunosorbent assay to detect the secretion of inflammatory cytokines, including interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and leptin. The phosphorylated STAT3 protein level in ligament flavum (LF) was examined using Western blot.

Results

Adipocytes size in EF was similar between in the TOLF and non-TOLF groups, but significantly smaller than that from autologous SCAT. Adipogenesis-related mRNA expression in EF was lower than that in SCAT. More fibrosis and vascularization were found in TOLF than in non-TOLF. EF in the TOLF group exhibited more macrophages and B lymphocytes infiltrated. The levels of cytokines such as IL-6, TNF-α, and leptin secreted by EF were significantly higher in the TOLF group than non-TOLF. The level of phosphorylated STAT3 in LF was significantly upregulated in the TOLF group.

Conclusions

Morphologically, EF adjacent to the ossification area is smaller and more uniform than autologous SCAT, exhibiting a characteristic similarity to visceral fat. EF in the TOLF group shows a more fibrotic, vascularized, and inflammatory phenotype, which secretes multiple cytokines. The phosphorylated STAT3 protein was significantly upregulated in the TOLF group. Whether these properties of EF directly affect the process of OLF needs to be further explored.

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.

IL-6 is involved in thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is a heterotopic ossification of spinal ligaments. TOLF is the major cause of thoracic spinal canal stenosis and myelopathy, and its underlying mechanisms are not clear. Bone formation is a complex developmental process involving the differentiation of mesenchymal stem cells to osteoblasts, and regulated by BMP2, RUNX2, Osterix (OSX), etc. In this study, we continue to further characterize properties of TOLF. Our immunohistochemistry experiments showed that expressions of osteoblastic factors such as BMP2 and RUNX2 increased in TOLF. According to flow cytometry analysis the proportion of S phase of cell cycle in primary TOLF cells was 9% higher than the control. Alizarin red staining and ALP staining observations were consistent with immunohistochemistry results. It was also observed that inflammatory cytokine IL-6 level dramatically increased in the culture supernatant of primary TOLF cells. We propose the hypothesis that IL-6 is involved in TOLF. To testify the hypothesis, we examined the effect of IL-6. Our results showed that IL-6 was able to activate expressions of osteoblastic factors such as BMP2, RUNX2, OSX, OCN and ALP, and that expressions of cell proliferation factors cyclin D1 and cyclin C increased in the presence of IL-6. Moreover, IL-6-induced BMP2 expression was inhibited by p38 inhibitor SB203580, indicating that IL-6 regulated the osteogenic BMP2 activation through p38 MAPK pathway. These data suggest that IL-6 is involved in TOLF.

Progression of Spinal Ligament Ossification in Patients with Thoracic Myelopathy

Objective

To evaluate the rate of increase in thickness and cross‐section area (CSA) of the ossification in thoracic myelopathy with or without cervical and lumbar spinal ligament ossification.

Methods

A total of 24 patients with 170 segments (47 ligamentum flavum [OLF] and 123 cases of ossification of the posterior longitudinal ligament [OPLL]) of spinal ligament ossification between January 2012 and March 2019 at a single institution were retrospectively reviewed. Demographic data, classification of OPLL, Sato classification of OLF, pre‐ and postoperative neurological function and complications were recorded. The thickness and CSA at the segment of maximum compression were measured with Image J software on the axial CT image.

Results

Twelve female and 12 male patients with thoracic myelopathy and spinal ligament ossification were enrolled in the study. The mean age of the patients was 54.0 ± 11.9 years with an average follow‐up of 22.2 ± 23.5 months. Overall, the mean rate of progression in thickness and CSA was 1.2 ± 1.6 and 18.4 ± 50.6 mm²/year, respectively. Being female, aging (≥45 years), and lower BMI (<28 kg/m²) predisposed patients to have faster ossification growth in thickness and CSA. The difference between the rate of OPLL and OLF progression in thickness and CSA was not significant. However, the rate of OPLL progression in the thoracic spine was significantly higher than that in the cervical spine regarding thickness (1.4 ± 1.9 vs. 0.6 ± 0.7 mm/year) and CSA (27.7 ± 72.0 vs. 7.3 ± 10.3 mm²/year).

Conclusion

This is the first study to investigate ligament ossification progression in patients with thoracic myelopathy. The difference between the rate of OPLL and OLF progression in thickness and CSA was not significant. However, the rate of thoracic OPLL progression in thickness and CSA was significantly higher than that in the cervical spine.

Ossified Ligamentum Flavum: Epidemiology, Treatment, and Outcomes

Ossification of the ligamentum flavum (OLF) is an uncommon but potentially serious spinal condition which can cause progressive compression of the spinal canal with associated devastating neurologic compromise. Although debate exists regarding the exact etiology of OLF, overexpression of genes and transcription factors centered around the Notch and Wnt signaling pathways because of increased mechanical stress seems to be related. There are many clinical and radiographic presentations of OLF; however, progressive myelopathy is the most commonly encountered. Radiographic analysis may reveal isolated OLF or OLF combined with ossification of other areas of the spine, such as disk, posterior longitudinal ligament, and dura. When surgery is necessary for OLF, several surgical strategies exist including open laminectomy with excision, endoscopic decompression, Bridge Crane resection, en block resection, and combined anterior and posterior approaches. Resection may be complicated by dural adhesion or dural ossification, and postoperative neurologic deficits are not uncommon.

Clinical Risk Factors for Thoracic Ossification of the Ligamentum Flavum: A Cross-Sectional Study Based on Spinal Thoracic Three-Dimensional Computerized Tomography

Background

Inconsistent results of the clinical risk factors associated with thoracic ossification of the ligamentum flavum (TOLF) have been reported in limited previous studies.

Purpose

This retrospective study aimed to investigate the potential risk factors for TOLF by a retrospective cross-sectional study, which may provide valuable experience for further clinical and pathophysiological research.

Methods

A total of 2247 asymptomatic participants, who underwent spinal thoracic three-dimensional computerized tomography (3D-CT) scans at our institution from January 2016 to December 2019, were enrolled in this study according to the screening criteria. Demographic information such as age, sex, height, weight, body mass index (BMI), smoking and drinking history, diastolic blood pressure (DBP), systolic blood pressure (SBP), and pulse pressure (PP) were recorded. Laboratory results included serum low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), triglyceride (TG), uric acid (UA), creatinine (Cr), calcium, and phosphorus. Participants were divided into TOLF group and non-TOLF group in accordance with the thoracic 3D-CT manifestation.

Results

TOLF was observed in 153 (6.81%) asymptomatic participants. Comparison of demographic data and laboratory examinations between the two groups showed that participants in the TOLF group were older, had a higher BMI, as well as higher levels of DBP. In addition, there was no significant difference in sex, drinking, tobacco use, SBP, TC, TG, PP, and levels of LDL-C, HDL-C, sUA, sCr, calcium, and phosphorus between the two groups. Furthermore, dichotomous logistic regression analyses revealed that age (OR = 1.018, p = 0.041) and BMI (OR = 1.090, p < 0.001) were risk factors for TOLF.

Conclusion

Our study reveals that age and BMI are clinical risk factors for the development of TOLF, while age cannot be identified as an independent risk factor for female in subgroup analysis.

The influence of ossification morphology on surgery outcomes in patients with thoracic ossification of ligamentum flavum (TOLF)

Background

To determine whether there is a correlation between the type of ossification and radiological parameters, modified thoracic JOA scores, and complications in patients with thoracic ossification of ligamentum flavum treated by posterior thoracic surgery.

Methods

This retrospective cohort study included 48 patients with thoracic myelopathy caused by single-level thoracic ossification of ligamentum flavum who underwent thoracic posterior approach surgery in our Hospital o between December 2013 to December 2018. Patients were divided into unilateral, bilateral, and bridged groups in axial position, and beak and round groups in sagittal position. The differences were analyzed according to the ossification morphology.

Results

In axial myelopathy, there was no significant difference in preop and postop JOA scores and RR among the three groups in axial position (P = 0.884). In sagittal view, there was no significant difference in preoperative JOA score between the two groups (P = 0.710), while the postop JOA score and the recovery rate in the beak group were significantly lower than that of the round group (P = 0.010, P = 0.034). Two-way ANOVA showed that sagittal morphology had a significant effect on postop JOA score (P = 0.028), but axial morphology don’t (P = 0.431); there was no interaction between them (P = 0.444). For the recovery rate, sagittal morphology also had a significant effect (P = 0.043), but axial ossification don’t (P = 0.998); there was no interaction between them (P = 0.479).

Conclusion

Sagittal morphology had a significant adverse effect on postop JOA score and surgical outcome, while axial morphology had no effect on surgical outcome, and there was no interaction between sagittal morphology and axial morphology.

Comparison of percutaneous endoscopic thoracic decompression and posterior thoracic laminectomy for treating thoracic ossification of the ligamentum flavum: a retrospective study

Background

Thoracic spinal stenosis (TSS) caused by ossification of the ligamentum flavum (OLF) is generally treated by surgical decompression. In this study, we compared the efficacy and safety of percutaneous endoscopic thoracic decompression (PETD) and posterior thoracic laminectomy (PTL) for treating thoracic ossification of the ligamentum flavum (TOLF).

Methods

Twenty consecutive patients with TSS caused by TOLF who were treated between April 2016 and May 2020 were included in this retrospective study. They were divided into the PETD (n = 11) and PTL (n = 9) groups. The mean follow-up period was 19.6 months. The visual analogue scale (VAS) score, the modified Japanese Orthopedic Association (mJOA) score and the recovery rate (RR) were used to evaluate the clinical outcomes.

Results

There were significant differences between PETD group and PTL group in operative time (min) (95.0 ± 18.8 vs 131.1 ± 19.0), postoperative drainage (mL) (20.2 ± 7.9 vs 586.1 ± 284.2), hospital stay (days) (4.4 ± 1.2 vs 10.4 ± 2.6) (P < 0.05 for all). However, both groups had similar and significant improvement in VAS and mJOA scores. The RR of two groups achieved the same improvement (81.8% VS 77.8%, P > 0.05).

Conclusions

The use of PETD and PTL for treating TOLF both achieved favorable outcomes. PETD is both minimally invasive and achieves similar postoperative symptom relief to PTL. Therefore, PETD could be considered as an effective alternative to traditional open surgery for TOLF in single-segment lower thoracic spine.

Association between obesity and ossification of spinal ligaments in 622 asymptomatic subjects: a cross-sectional study

INTRODUCTION

Previous studies on patients with symptoms of spinal ligament ossification, including ossification of the posterior longitudinal ligament (OPLL) and ligamentum flavum (OLF), have not clarified whether obesity is a cause or consequence of these diseases and were limited by selection bias. Thus, we investigated the association between obesity and the prevalence of spinal ligament ossification in randomly selected asymptomatic subjects.

MATERIALS AND METHODS

Between April 2020 and March 2021, 622 asymptomatic Japanese subjects who underwent computed tomography of neck to pelvis for medical check-up purposes were included. All subjects were divided into the following three groups: normal weight (body mass index [BMI] < 25 kg/m²), obese I (25 ≤ BMI < 30 kg/m²), and obese II (BMI ≥ 30 kg/m²). The relationship between factors affecting the presence of each spinal ligament ossification was evaluated using multivariate logistic regression analysis.

RESULTS

The proportion of subjects with thoracic OPLL was significantly higher in the obese II group than in the other two groups (vs. normal weight, P < 0.001; vs. obese I, P < 0.001). BMI was associated with the prevalence of OLF, cervical OPLL, thoracic OPLL, and ossification of the anterior longitudinal ligament (OALL). BMI was most significantly associated with the prevalence of thoracic OPLL (β, 0.28; 95% confidence interval, 0.17-0.39).

CONCLUSION

BMI was associated with the prevalence of OALL, cervical OPLL, thoracic OPLL, and OLF in asymptomatic subjects, suggesting that obesity is associated with the development of heterotopic ossification of the spinal ligaments.

Dissatisfaction Risk Factors of Patients after Laminectomy for Thoracic Ossification of Ligamentum Flavum: A Retrospective Cohort Study of Different Follow-Up Periods

Objectives

To explore the influencing factors of satisfaction with postoperative treatment in patients diagnosed with thoracic ossification of the ligamentum flavum during different follow-up periods.

Methods

This was a retrospective study of 57 patients who were diagnosed with thoracic ossification of ligamentum flavum (TOLF) and treated with laminectomy in the Spine Surgery Department of the Third Hospital of Hebei Medical University from January 2010 to January 2017. The Patient Satisfaction Index (PSI) was collected at discharge and at 6-month, 1-year, and the last follow-up. According to the evaluation results, the patients could be divided into a satisfied group and a dissatisfied group. The patient's Japanese Orthopaedic Association (JOA) score improvement rate was evaluated at the last follow-up. Possible influencing factors of the two groups of patients were compared and the related influencing factors of satisfaction with postoperative treatment in patients during different follow-up periods were summarized.

Results

At the time of discharge, the dissatisfied and satisfied groups had significant differences in variables of diabetes mellitus, duration of preoperative symptoms, urination disorder, intramedullary signal change on MRI, dural ossification, residual rate of cross-sectional spinal canal area on CT, shape on the sagittal MRI, hospital stay, hospitalization expenses, postoperative pain in LE VAS, delayed wound healing, postoperative depression, and intercostal pain (P < 0.05). There were also significant differences in urination disorder, postoperative pain according to the LE VAS, JOA score, and postoperative depression during the 6-month follow-up (P < 0.05). There were no significant differences in other variables between the two groups (P > 0.05). One year after the operation, there were significant differences between the dissatisfied group and the satisfied group in urination disorder, JOA score, and symptom recurrence (P < 0.05). There were also significant differences in the JOA score and symptom recurrence at the final follow-up (P < 0.05). For further analysis, the duration of preoperative symptoms in the satisfied group was less than 24 months and the duration of preoperative symptoms in the dissatisfied group was more than 24 months. The JOA scores of patients in the satisfied group and the dissatisfied group increased gradually with the improvement of neurological function in different follow-up periods, but, at the last follow-up, the JOA scores of patients in the satisfied group were significantly higher than those in the dissatisfied group.

Conclusions

In conclusion, for thoracic ossification of ligamentum flavum patients who received laminectomy, dissatisfaction with the early and medium-term postoperative results may be related to diabetes, the duration of preoperative symptoms, hospitalization expenses, delayed wound healing, intercostal pain, and urination disorder, and dissatisfaction with the long-term postoperative results might be related to the low JOA score improvement rate and symptom recurrence.

Postoperative progression of ligamentum flavum ossification after posterior instrumented surgery for thoracic posterior longitudinal ligament ossification: long-term outcomes during a minimum 10-year follow-up

OBJECTIVE

The authors sought to investigate clinical and radiological outcomes after thoracic posterior fusion surgery during a minimum of 10 years of follow-up, including postoperative progression of ossification, in patients with thoracic ossification of the posterior longitudinal ligament (T-OPLL).

METHODS

The study participants were 34 consecutive patients (15 men, 19 women) with an average age at surgery of 53.6 years (range 36-80 years) who underwent posterior decompression and fusion surgery with instrumentation at the authors' hospital. The minimum follow-up period was 10 years. Estimated blood loss, operative time, pre- and postoperative Japanese Orthopaedic Association (JOA) scores, and JOA score recovery rates were investigated. Dekyphotic changes were evaluated on plain radiographs of thoracic kyphotic angles and fusion levels pre- and postoperatively and 10 years after surgery. The distal junctional angle (DJA) was measured preoperatively and at 10 years after surgery to evaluate distal junctional kyphosis (DJK). Ossification progression at distal intervertebrae was investigated on CT.

RESULTS

The Cobb angles at T1-12 were 46.8°, 38.7°, and 42.6°, and those at the fusion level were 39.6°, 31.1°, and 34.1° pre- and postoperatively and at 10 years after surgery, respectively. The changes in the kyphotic angles from pre- to postoperatively and to 10 years after surgery were 8.0° and 7.2° at T1-12 and 8.4° and 7.9° at the fusion level, respectively. The DJA changed from 4.5° postoperatively to 10.9° at 10 years after surgery. There were 11 patients (32.3%) with DJK during follow-up, including 4 (11.8%) with vertebral compression fractures at lower instrumented vertebrae or adjacent vertebrae. Progression of ossification of the ligamentum flavum (OLF) on the caudal side occurred in 8 cases (23.6%), but none had ossification of the posterior longitudinal ligament (OPLL) progression. Cases with OLF progression had a significantly lower rate of DJK (0% vs 38.5%, p < 0.01), a lower DJA (3.4° vs 13.2°, p < 0.01), and a smaller change in DJA at 10 years after surgery (0.8° vs 8.1°, p < 0.01).

CONCLUSIONS

Posterior decompression and fusion surgery with instrumentation for T-OPLL was found to be a relatively safe and stable surgical procedure based on the long-term outcomes. Progression of OLF on the caudal side occurred in 23.6% of cases, but cases with OLF progression did not have DJK. Progression of DJK shifts the load in the spinal canal forward and the load on the ligamentum flavum is decreased. This may explain the lack of ossification in cases with DJK.

Risk factors for the development of degenerative cervical myelopathy: a review of the literature

Degenerative cervical myelopathy (DCM) encompasses various pathological conditions causing spinal cord (SC) impairment, including spondylosis (multiple level degeneration), degenerative disc disease (DDD), ossification of the posterior longitudinal ligament (OPLL), and ossification of the ligamentum flavum (OLF). It is considered the most common cause of SC dysfunction among the adult population. The degenerative phenomena of DDD, spondylosis, OPLL and OLF, is likely due to both inter-related and distinct factors. Age, cervical alignment, and range of motion, as well as congenital factors such as cervical cord-canal mismatch due to congenital stenosis, Klippel-Feil, Ehler-Danlos, and Down syndromes have been previously reported as potential factors of risk for DCM. The correlation between some comorbidities, such as rheumatoid arthritis and movement disorders (Parkinson disease and cervical dystonia) and DCM, has also been reported; however, the literature remains scare. Other patient-specific factors including smoking, participation in contact sports, regular heavy load carrying on the head, and occupation (e.g. astronauts) have also been suggested as potential risk of myelopathy development. Most of the identified DCM risk factors remain poorly studied however. Further researches will be necessary to strengthen the current knowledge on the subject, especially concerning physical labors in order to identify patients at risk and to develop an effective treatment strategy for preventing this increasing prevalent disorder.

Cervical Single-Level Pincer Stenosis Causing Myelopathy: A Technical Note and Medium-term Results of a One-Session Microsurgical 360-Degree Treatment

BACKGROUND AND STUDY AIMS

 Single-level circumferential or pincer stenosis (PS) affects few patients with degenerative cervical myelopathy (DCM). The surgical technique and medium-term results of a one-session microsurgical 360-degree (m360°) procedure are presented.

PATIENTS

 Between 2013 and 2018, the data of 23 patients were prospectively collected out of 371 patients with DCM. The m360° procedure comprised a microsurgical anterior cervical decompression and fusion (ACDF), with additional plate fixation, followed by flipping the patient and performing a microsurgical posterior bilateral decompression via a unilateral approach in crossover technique.

RESULTS

 The mean age of the patients was 72 years (range: 50-84); 17 patients were males. The mean follow-up time was 12 months (range: 6-31). The patients filled in the patient-derived modified Japanese Orthopaedic Association (P-mJOA) questionnaire on average 53 months after surgery. One patient received a two-level ACDF. Lesions were mostly (92%) located at the C3/C4 (8/24), C4/C5 (7/24), and C5/C6 (7/24) levels. Functional X-rays showed segmental instability in 10 of 23 patients (44%). All preoperative T2-weighted magnetic resonance imaging (MRI) showed an intramedullary hyperintensity. The median preoperative mJOA score was 13 (range 3), and it improved to 16 (range 3) postoperatively. The mean improvement rate in the mJOA score was 73%. When available, postoperative MRI confirmed good circumferential decompression with persistent intramedullary hyperintensity. There were two complications: a long-lasting radicular paresthesia at C6 and a transient C5 palsy. No revision surgery was required.

CONCLUSION

 The one-session m360° procedure was found to be a safe surgical procedure for the treatment of PS, and the medium-term clinical outcome was satisfactory.

Lumbar radiculopathy due to foraminal stenosis with ossification of the ligamentum flavum: a case report

The patient was an 82-year-old woman with a diagnosis of lumbar radiculopathy due to foraminal stenosis accompanied by ossification of the ligamentum flavum (OLF). Computed tomography scans of the lumbar spine revealed ossification in the capsular portion of the ligamentum flavum around the L2–L3 facet joint. In addition, computed tomography images acquired a few months before the onset of radiculopathy had shown that the ossification site had gradually expanded to include the superior articular process. The patient’s symptoms disappeared immediately after excision of the OLF. Histopathological examination of the resected specimen indicated replacement of degenerated ligamentum flavum with ossified tissue via a gradual endochondral ossification process. It is important to be aware that foraminal stenosis can in rare cases occur due to OLF, even in the lumbar spine.

Thoracic ossification of the ligamentum flavum causing acute myelopathy in a patient with cervical ossification of the posterior longitudinal ligament: illustrative case

BACKGROUND

Ossification of the ligamentum flavum (OLF) has been well characterized as a distinct entity but also in tandem with ossification of the posterior longitudinal ligament (OPLL) in noncontiguous spinal regions. The majority of OLF cases are reported from East Asian countries where prevalent, but such cases are rarely reported in the North American population.

OBSERVATIONS

The authors present a case of a Thai-Cambodian American who presented with symptomatic thoracic OLF in tandem with asymptomatic cervical OPLL. A “floating” thoracic laminectomy, resection of OLF, and partial dural ossification (DO) resection with circumferential release of ossified dura were performed. Radiographic dural reexpansion and spinal cord decompression occurred despite the immediate intraoperative appearance of persistent thecal sac compression from retained DO.

LESSONS

Entire spinal axis imaging should be considered for patients with spinal ligamentous ossification disease, particularly in those of East Asian backgrounds. A floating laminectomy is one of several surgical approaches for OLF, but no consensus approach has been clearly established. High surgical complication rates are associated with thoracic OLF, most commonly dural tears/cerebrospinal fluid (CSF) leaks. DO commonly coexists with OLF, is recognizable on computed tomographic scans, and increases the risk of CSF leaks.

Comparison of Intraoperative Neuromonitoring Outcome in Treating Thoracic Ossification of the Ligamentum Flavum Through En Bloc Versus Piecemeal Laminectomy

STUDY DESIGN

A retrospective cohort analysis.

OBJECTIVE

The aim of this study was to investigate the impact of piecemeal versus en bloc laminectomies on spinal cord in thoracic ossification of ligamentum flavum (TOLF) through intraoperative changes of motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SEPs).

SUMMARY OF BACKGROUND DATA

Surgical treatment is indicated for symptomatic TOLF, and both piecemeal and en bloc laminectomies are commonly used methods. However, few studies compared both intraoperative interference and prognostic impact of these two laminectomies on spinal cord in TOLF patients.

METHODS

MEPs were recorded from abductor hallucis (AH) and tibialis anterior, and SEPs were performed on tibial nerve in 55 TOLF patients (piecemeal vs. en bloc: 23 vs. 32). Patients were categorized based on MEP/SEP improvement, deterioration, and no change, and MEP/SEP improvement rates were measured in the improvement group. Additionally, all patients were assessed by American Spinal Injury Association (ASIA) scores, Ashworth scores, and modified Japanese Orthopedic association (mJOA) scores before and after operation.

RESULTS

The incidences of both MEP/SEP improvement and deterioration were similar between the two laminectomy groups (P > 0.05), and no significant difference is noted in both MEP and SEP amplitudes between the baseline and different critical manipulations in both laminectomy groups (P > 0.05). In the improvement group, patients receiving en bloc laminectomy exhibited increased improvement rates of both MEPs in bilateral AH and left-side SEPs compared to piecemeal laminectomy (P < 0.05). Clinically, all functional scales clearly improved in both laminectomy groups after operation (P < 0.05), and postoperative 1-year mJOA improvement rates were highly correlated with MEP improvement rates (P < 0.05).

CONCLUSION

Intraoperative changes of MEPs and SEPs potentially provide a valid method for quantitatively evaluating the safety of different intraoperative manipulations and their prognostic impacts on spinal cord. Both laminectomies are safe and effective methods to treat TOLF, and en bloc laminectomy may cause relatively better spinal cord functional recovery.Level of Evidence: 3.