A Convolutional Neural Network for Automated Detection of Cervical Ossification of the Posterior Longitudinal Ligament using Magnetic Resonance Imaging

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

We aimed to develop and validate a convolutional neural network (CNN) model to distinguish between cervical ossification of posterior longitudinal ligament (OPLL) and multilevel degenerative spinal stenosis using Magnetic Resonance Imaging (MRI) and to compare the diagnostic ability with spine surgeons.

SUMMARY OF BACKGROUND DATA

Some artificial intelligence models have been applied in spinal image analysis and many of promising results were obtained; however, there was still no study attempted to develop a deep learning model in detecting cervical OPLL using MRI images.

MATERIALS AND METHODS

In this retrospective study, 272 cervical OPLL and 412 degenerative patients underwent surgical treatment were enrolled and divided into the training (513 cases) and test dataset (171 cases). CNN models applying ResNet architecture with 34, 50, and 101 layers of residual blocks were constructed and trained with the sagittal MRI images from the training dataset. To evaluate the performance of CNN, the receiver operating characteristic curves of 3 ResNet models were plotted and the area under the curve were calculated on the test dataset. The accuracy, sensitivity, and specificity of the diagnosis by the CNN were calculated and compared with 3 senior spine surgeons.

RESULTS

The diagnostic accuracies of our ResNet34, ResNet50, and ResNet101 models were 92.98%, 95.32%, and 97.66%, respectively; the area under the curve of receiver operating characteristic curves of these models were 0.914, 0.942, and 0.971, respectively. The accuracies and specificities of ResNet50 and ResNet101 models were significantly higher than all spine surgeons; for the sensitivity, ResNet101 model achieved better values than that of the 2 surgeons.

CONCLUSION

The performance of our ResNet model in differentiating cervical OPLL from degenerative spinal stenosis using MRI is promising, better results were achieved with more layers of residual blocks applied.

Anterior direct decompression significantly relieves spinal cord high signal in patients with ossification of the posterior longitudinal ligament: a case-control study

BACKGROUND

In patients with cervical spondylotic myelopathy caused by ossification of the posterior longitudinal ligament, high cord signal (HCS) is frequently observed. However, limited research has investigated the variations in HCS improvement resulting from different surgical approaches. This study aims to explore the potential relationship between the choice of surgical approach and the postoperative improvement of intramedullary high signal in ossification of the posterior longitudinal ligament (OPLL) patients.

METHODS

We extensively reviewed the patients' medical records, based on which demographic information such as gender, age, and body mass index (BMI) were recorded, and assessed the severity of the patients' neurological status preoperatively and postoperatively by using the Japanese Orthopedic Association score (JOAs), focusing on consecutive preoperative and postoperative Magnetic resonance imaging (MRI) T2WI measurements, to study the statistical correlation between the improvement of HCS and the choice of surgical approach.

RESULTS

There were no significant differences in demographic, imaging parameters, and clinical symptoms between patients undergoing anterior and posterior surgery (p > 0.05, Table 1). However, both improvement in JOAs (Recovery2) and improvement in HCS (CR2) were significantly better in the anterior surgery group two years after surgery (p < 0.05, Table 1). Multifactorial logistic regression analysis revealed that posterior surgery and higher preoperative signal change ratio (SCR) were identified as risk factors for poor HCS improvement at the two-year postoperative period (p < 0.05, Table 2). Table 1 Differences in demographic, imaging parameters, and clinical symptoms in patients with anterior and posterior approach Anterior approach Posterior approach P-Values Demographic data  Sex (male/female) 10/12 6/17 0.175  Age 58.59 ± 5.68 61.43 ± 9.04 0.215  Hypertension 14/8 14/9 0.848  Diabetes 16/6 19/4 0.425  BMI 25.58 ± 4.72 26.95 ± 4.58 0.331  Smoking history 19/3 16/7 0.175 Preoperative measured imaging parameters  Preoperative SCR 1.615 ± 0.369 1.668 ± 0.356 0.623  CR1 0.106 ± 0.125 0.011 ± 0.246 0.08  CNR 0.33 ± 0.073 0.368 ± 0.096 0.15  C2-7 Cobb angle 8.977 ± 10.818 13.862 ± 13.191 0.182  SVA 15.212 ± 8.024 17.46 ± 8.91 0.38  mK-line INT 3.694 ± 3.291 4.527 ± 2.227 0.323 Imaging follow-up  6 months postoperative SCR 1.45 ± 0.44 1.63 ± 0.397 0.149  2 years postoperative SCR 1.26 ± 0.19 1.65 ± 0.35 0.000**  CR2 0.219 ± 0.14 - 0.012 ± 0.237 0.000** Clinical symptoms  Preoperative JOAs 10.64 ± 1.59 10.83 ± 1.47 0.679  6 months postoperative JOAs 11.82 ± 1.37 11.65 ± 1.4 0.69  2 years postoperative JOAs 14.18 ± 1.01 12.52 ± 2.06 0.001**  Recovery1 0.181 ± 0.109 0.128 ± 0.154 0.189  Recovery2 0.536 ± 0.178 0.278 ± 0.307 0.001** *, statistical significance (p < 0.05). **, statistical significance (p < 0.01) BMI = body mass index. SCR = the signal change ratio between the localized high signal and normal spinal cord signal at the C7-T1 levels. CR1 = the regression of high cord signals at 6 months postoperatively (i.e., CR1 = (Preoperative SCR-SCR at 6 months postoperatively)/ Preoperative SCR). CR2 = the regression of high cord signal at 2 years postoperatively (i.e., CR2 = (Preoperative SCR-SCR at 2 years postoperatively)/ Preoperative SCR). CNR = canal narrowing ratio. SVA = sagittal vertical axis. mK-line INT = modified K-line interval. JOAs = Japanese Orthopedic Association score. Recovery1 = degree of JOAs recovery at 6 months postoperatively (i.e., Recover1 = (JOAs at 6 months postoperatively-Preoperative JOAs)/ (17- Preoperative JOAs)). Recovery2 = degree of JOAs recovery at 2 years postoperatively (i.e., Recover2 = (JOAs at 2 years postoperatively-Preoperative JOAs)/ (17-Preoperative JOAs)) Table 2 Linear regression analyses for lower CR2 values 95% CI P value Uni-variable analyses Demographic data  Sex (male/female) - 0.01 0.221 0.924  Age - 0.015 0.003 0.195  Hypertension - 0.071 0.204 0.334  Diabetes - 0.195 0.135 0.716  BMI - 0.375 0.422 0.905  Smoking history - 0.249 0.077 0.295  Surgical approach - 0.349 - 0.113 0.000# Preoperative measured imaging parameters  C2-7 Cobb angle - 0.009 0.002 0.185  SVA - 0.008 0.008 0.995  mK-line INT - 0.043 0.005 0.122  Preoperative SCR 0.092 0.445 0.004#  CR1 0.156 0.784 0.004#  CNR - 0.76 0.844 0.918 Multi-variable analyses  Surgical approach - 0.321 - 0.118 0.000**  Preoperative SCR 0.127 0.41 0.000**  CR1 - 0.018 0.501 0.067 #, variables that achieved a significance level of p < 0.1 in the univariate analysis *statistical significance (p < 0.05). **statistical significance (p < 0.01) BMI = body mass index. SCR = the signal change ratio between the localized high signal and normal spinal cord signal at the C7-T1 levels. CR1 = the regression of high cord signals at 6 months postoperatively (i.e., CR1 = (Preoperative SCR-SCR at 6 months postoperatively)/ Preoperative SCR). CR2 = the regression of high cord signal at 2 years postoperatively (i.e., CR2 = (Preoperative SCR-SCR at 2 years postoperatively)/ Preoperative SCR). CNR = canal narrowing ratio. SVA = sagittal vertical axis. mK-line INT = modified K-line interval CONCLUSIONS: For patients with OPLL-induced cervical spondylotic myelopathy and intramedullary high signal, anterior removal of the ossified posterior longitudinal ligament and direct decompression offer a greater potential for regression of intramedullary high signal. At the same time, this anterior surgical strategy improves clinical neurologic function better than indirect decompression in the posterior approach.

Prevalence and Characteristics of Cervical Ossified Posterior Longitudinal Ligament in the Jewish Population

BACKGROUND

Numerous studies have demonstrated an association between ethnic identity and the prevalence rate of cervical ossified posterior longitudinal ligament (C-OPLL). To date, its prevalence rate in the Jewish population has not been determined. The aim of this historical prospective study is to evaluate the prevalence and characteristics of C-OPLL in the Jewish population.

METHODS

We performed a retrospective evaluation of imaging studies of all adult patients who underwent both cervical computed tomography and magnetic resonance imaging for all clinical indications within a span of 36 months between January 2017 and July 2020 at a single tertiary referral hospital located in central Israel. Identified C-OPLL carriers were interviewed by telephone. All the patients provided informed consent and then were questioned for current symptoms and demographics, including religion, Jewish ethnic identity, birthplace, parental birthplace and ethnic identity, and family history of spinal disorders.

RESULTS

Overall, 440 participants were radiographically evaluated. The prevalence of C-OPLL in the Jewish population was 7.5% (33 of 440). The mean age of the C-OPLL carriers was 65.8 years. All the C-OPLL carriers were symptomatic at analysis. The carriers had an increased proportion with a Sephardic Jewish ethnic identity (65.4%), with a significantly high rate of homogeneous parental Jewish identity (92.4%), suggesting a prominent genetic contribution to the development of this condition.

CONCLUSIONS

The prevalence of C-OPLL in the Jewish population in central Israel was 7.5%. This rate is significantly higher than that in other previously studied populations. To the best of our knowledge, this is the first study to identify the Jewish population as experiencing an increased prevalence of C-OPLL.

Genetic insights into ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament of the spine (OPLL) is an intractable disease leading to severe neurological deficits. Its etiology and pathogenesis are primarily unknown. The relationship between OPLL and comorbidities, especially type 2 diabetes (T2D) and high body mass index (BMI), has been the focus of attention; however, no trait has been proven to have a causal relationship. We conducted a meta-analysis of genome-wide association studies (GWASs) using 22,016 Japanese individuals and identified 14 significant loci, 8 of which were previously unreported. We then conducted a gene-based association analysis and a transcriptome-wide Mendelian randomization approach and identified three candidate genes for each. Partitioning heritability enrichment analyses observed significant enrichment of the polygenic signals in the active enhancers of the connective/bone cell group, especially H3K27ac in chondrogenic differentiation cells, as well as the immune/hematopoietic cell group. Single-cell RNA sequencing of Achilles tendon cells from a mouse Achilles tendon ossification model confirmed the expression of genes in GWAS and post-GWAS analyses in mesenchymal and immune cells. Genetic correlations with 96 complex traits showed positive correlations with T2D and BMI and a negative correlation with cerebral aneurysm. Mendelian randomization analysis demonstrated a significant causal effect of increased BMI and high bone mineral density on OPLL. We evaluated the clinical images in detail and classified OPLL into cervical, thoracic, and the other types. GWAS subanalyses identified subtype-specific signals. A polygenic risk score for BMI demonstrated that the effect of BMI was particularly strong in thoracic OPLL. Our study provides genetic insight into the etiology and pathogenesis of OPLL and is expected to serve as a basis for future treatment development.

Clinical feasibility of MR-generated synthetic CT images of the cervical spine: Diagnostic performance for detection of OPLL and comparison of CT number

We aimed to determine the incremental value of magnetic resonance generated synthetic computed tomography (MRCT), evaluate cervical ossification of the posterior longitudinal ligament (OPLL), and compare the computed tomography (CT) numbers between MRCT and conventional CT.Twenty-two patients who underwent magnetic resonance imaging (MRI) with MRCT protocols and CT were enrolled. MRCT images were generated from 3D-T2-weighted imaging, 3D-pointwise-encoding time reduction with radial acquisition, 3D-T1-Dixon, and 3D-time-of-flight sequences. Two radiologists independently evaluated the presence of OPLL at each cervical spine level during sessions 1 (MRI alone) and 2 (MRI + MRCT). CT was the reference standard for the presence of OPLL. One reader measured the mean CT number of the vertebral body and spinous process at each cervical spine level in the MRCT and CT images.Sensitivity for the detection of OPLL was markedly higher in session 2 (MRI + MRCT) than in session 1 (MRI alone), as measured by both readers (47% vs. 90%, reader 1; 63% vs. 93%, reader 2). The mean CT number of MRCT and CT showed a moderate to strong positive correlation (ρ = .42-.72, P < .001).The combined use of MRCT and MRI showed improved sensitivity for the evaluation of cervical OPLL. The mean CT number of MRCT and CT showed a positive correlation.

Bone marrow mesenchymal stem cell-derived extracellular vesicles containing miR-497-5p inhibit RSPO2 and accelerate OPLL

AIMS

Muscle and adipose tissue-derived mesenchymal stem cells presented high osteogenic potentials, which modulate osteoblast function through releasing extracellular vesicles (EVs) containing miRNAs. Herein, this study evaluated the function of bone marrow mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) delivering miR-497-5p in ossification of the posterior longitudinal ligament (OPLL).

MAIN METHODS

The expression level of miR-497-5p was validated in ossified posterior longitudinal ligament (PLL) tissues and BMSC-EVs. The uptake of BMSC-EVs by ligament fibroblasts was observed by immunofluorescence. miR-497-5p was overexpressed or downregulated to assess its role in osteogenic differentiation of ligament fibroblasts. Further, an OPLL rat model was established to substantiate the effect of BMSC-EVs enriched with miR-497-5p on OPLL.

KEY FINDINGS

Ossified PLL tissues presented with high miR-497-5p expression. PLL fibroblasts were identified to endocytose BMSC-EVs. BMSC-EVs could upregulate miR-497-5p and shuttle it to ligament fibroblasts to accelerate the osteogenic differentiation. miR-497-5p targeted and inversely regulated RSPO2. Then, RSPO2 overexpression activated Wnt/β-catenin pathway and repressed the osteogenic differentiation of ligament fibroblasts. In vivo experiments further showed that miR-497-5p-containing BMSC-EVs enhanced OPLL through diminishing RSPO2 and inactivating Wnt/β-catenin pathway.

SIGNIFICANCE

BMSC-EVs could deliver miR-497-5p to ligament fibroblasts and modulate RSPO2-mediated Wnt/β-catenin pathway, thereby accelerating OPLL.

MicroRNA-181 regulates the development of Ossification of Posterior longitudinal ligament via Epigenetic Modulation by targeting PBX1

Objectives: Ossification of the posterior longitudinal ligament (OPLL) presents as the development of heterotopic ossification in the posterior longitudinal ligament of the spine. The etiology of OPLL is genetically linked, as shown by its high prevalence in Asian populations. However, the molecular mechanism of the disease remains obscure. In this study, we explored the function and mechanism of OPLL-specific microRNAs. Methods: The expression levels of the ossification-related OPLL-specific miR-181 family were measured in normal or OPLL ligament tissues. The effect of miR-181a on the ossification of normal or pathogenic ligament cells was tested using real-time polymerase chain reaction (PCR), Western blot, alizarin red staining and alkaline phosphatase (ALP) staining. The candidate targets of miR-181 were screened using a dual luciferase reporter assay and functional analysis. The link between miR-181a and its target PBX1 was investigated using chromatin immunoprecipitation, followed by real-time PCR detection. Histological and immunohistochemical analysis as well as micro-CT scanning were used to evaluate the effects of miR-181 and its antagonist using both tip-toe-walking OPLL mice and in vivo bone formation assays. Results: Using bioinformatic analysis, we found that miR-181a-5p is predicted to play important roles in the development of OPLL. Overexpression of miR-181a-5p significantly increased the expression of ossification-related genes, staining level of alizarin red and ALP activity, while the inhibition of miR-181a-5p by treatment with an antagomir had the opposite effects. Functional analysis identified PBX1 as a direct target of miR-181a-5p, and we determined that PBX1 was responsible for miR-181a-5p's osteogenic phenotype. By chromatin immunoprecipitation assay, we found that miR-181a-5p controls ligament cell ossification by regulating PBX1-mediated modulation of histone methylation and acetylation levels in the promoter region of osteogenesis-related genes. Additionally, using an in vivo model, we confirmed that miR-181a-5p can substantially increase the bone formation ability of posterior ligament cells and cause increased osteophyte formation in the cervical spine of tip-toe-walking mice. Conclusions: Our data unveiled the mechanism by which the miR-181a-5p/PBX1 axis functions in the development of OPLL, and it revealed the therapeutic effects of the miR-181a-5p antagomir in preventing OPLL development both in vivo and in vitro. Our work is the first to demonstrate that microRNA perturbation could modulate the development of OPLL through epigenetic regulation.

Integrated miRNA-mRNA network revealing the key molecular characteristics of ossification of the posterior longitudinal ligament

BACKGROUND

Ossification of the posterior longitudinal ligament (OPLL) refers to an ectopic ossification disease originating from the posterior longitudinal ligament of the spine. Pressing on the spinal cord or nerve roots can cause limb sensory and motor disorders, significantly reducing the patient's quality of life. At present, the pathogenesis of OPLL is still unclear. The purpose of this study is to integrate microRNA (miRNA)-mRNA biological information data to further analyze the important molecules in the pathogenesis of OPLL, so as to provide targets for future OPLL molecular therapy.

METHODS

miRNA and mRNA expression profiles of GSE69787 were downloaded from Gene Expression Omnibus database and analyzed by edge R package. Funrich software was used to predict the target genes and transcription factors of de-miRNA. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis of differentially expressed genes (DEGs) were carried out based on CLUEGO plug-in in Cytoscape. Using data collected from a search tool for the retrieval of interacting genes online database, a protein-protein interaction (PPI) network was constructed using Cytoscape. The hub gene selection and module analysis of PPI network were carried out by cytoHubba and molecular complex detection, plug-ins of Cytoscape software respectively.

RESULTS

A total of 346 genes, including 247 up-regulated genes and 99 down-regulated genes were selected as DEGs. SP1 was identified as an upstream transcription factor of de-miRNAs. Notably, gene ontology enrichment analysis shows that up- and down-regulated DEGs are mainly involved in BP, such as skeletal structure morphogenesis, skeletal system development, and animal organ morphogenesis. Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that only WNT signaling pathway was associated with osteogenic differentiation. Lymphoid enhancer binding factor 1 and wingless-type MMTV integration site family member 2 Wingless-Type MMTV Integration site family member 2 were identified as hub genes, miR-520d-3p, miR-4782-3p, miR-6766-3p, and miR-199b-5p were identified as key miRNAs. In addition, 2 important network modules were obtained from PPI network.

CONCLUSIONS

In this study, we established a potential miRNA-mRNA regulatory network associated with OPLL, revealing the key molecular mechanism of OPLL and providing targets for future treatment or prevent its occurrence.

Association between ossification of the posterior longitudinal ligament and ossification of the nuchal ligament in the cervical spine

OBJECTIVES

To investigate the association between ossification of the posterior longitudinal ligament (OPLL) and ossification of the nuchal ligament (ONL) in terms of incidence and size.

METHODS

This retrospective study evaluated 297 patients who underwent CT of the cervical spine (C-spine). Two radiologists worked in consensus. The incidence of OPLL from patients with and without ONL was compared using Chi Square tests. The mean lengths of ONL from patients with and without OPLL were compared using Student t-test. The correlations between the length of ONL and the presence of OPLL and between the length of ONL and the length of OPLL were analyzed with Pearson correlations.

RESULTS

We found that OPLL occurred more frequently in patients with ONL than in patients without ONL (odd ratio = 2.524, p = 0.037); however, the mean length of ONL did not differ significantly patients with and without OPLL (p = 0.874). We found no significant correlation between the length of ONL and the length of OPLL (p = 0.233).

CONCLUSION

The presence of ONL was associated with the presence of OPLL. The length of OPLL and ONL showed no correlation.

Long non-coding RNA MALAT1 functions as miR-1 sponge to regulate Connexin 43-mediated ossification of the posterior longitudinal ligament

Ossification of the posterior longitudinal ligament (OPLL) is the major cause for several deteriorate bone and joint diseases. Its development is a highly organized dynamic process as modulated by various physiological and pathophysiological factors. Both long non-coding RNAs (lncRNAs) and small non-coding RNAs (miRNAs) have been postulated to involve into almost all the biological conditions. Here, we applied high through-put transcriptome screening to unveil lncRNAs highly regulated under OPLL condition. siRNA assay in combination with western blot and quantitative PCR deciphered the lncRNA and miRNA functions in OPLL and their underlying mechanism. Here we identified an lncRNA, named Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1) engaged into the development of OPLL by indirectly targeting Connexin 43 (Cx43) gene. As previously reported, Cx43 is one of the main proteins contributing to OPLL partially through enhancing inflammatory signaling. On top of that, we provided another regulatory layer that MALAT1 served as the upstream effector governing the transcription of Cx43 gene. Perturbation of MALAT1 significantly inhibited Cx43 expression, inflammation, and osteogenesis. Mechanistically, in silico analysis and experimental validation both confirmed that microRNA-1 (miR-1) was the mediator connecting MALAT1-Cx43 axis: overexpression of miR-1 diminished Cx43 expression and OPLL process; meanwhile, MALAT1 acted as miR-1 sponge to inhibit its suppressive transcription effect on downstream ossification related genes. Knock-down of MALAT1 released sequestered miR-1, which repressed Cx43 expression and associated OPLL. Likewise, induced OPLL caused by overexpression of MALAT1 can be ameliorated by enhanced miR-1 function, knock-down of Cx43 or inhibition of inflammation. More importantly, further validation using patient ligament samples from non-OPLL and OPLL individuals identified MALAT1-miR-1-Cx43 regulatory axis. Collectively, we found a novel mechanism through lncRNA-miRNA interaction that provides more insights into understanding the development of OPLL.

Ubiquitin-dependent proteolysis of CXCL7 leads to posterior longitudinal ligament ossification

Ossification of the posterior longitudinal ligament (OPLL), a spinal ligament, reduces the range of motion in limbs. No treatment is currently available for OPLL, which is why therapies are urgently needed. OPLL occurs in obesity, is more common in men, and has an onset after 40 years of age. The mechanisms underlying OPLL remain unclear. In this study, we performed a serum proteomic analysis in both OPLL patients and healthy subjects to identify factors potentially involved in the development of OPLL, and found reduced levels of a protein that might underlie the pathology of OPLL. We isolated the protein, determined its amino acid sequence, and identified it as chemokine (C-X-C motif) ligand 7 (CXCL7). Based on these proteomics findings, we generated a CXCL7 knockout mouse model to study the molecular mechanisms underlying OPLL. CXCL7-null mice presented with a phenotype of OPLL, showing motor impairment, heterotopic ossification in the posterior ligament tissue, and osteoporosis in vertebrate tissue. To identify the mechanisms of CXCL7 deficiency in OPLL, we searched for single nucleotide polymorphisms and altered DNA exons, but no abnormalities were found. Although miR-340 levels were found to be high in an miRNA array, they were insufficient to reduce CXCL7 levels. Ubiquitin C-terminal hydrolase1 (UCHL1) was found to be overexpressed in CXCL7-null mice and in the sera of patients with OPLL, and was correlated with OPLL severity. Post-translational modifications of proteins with ubiquitin and ubiquitin-like modifiers, orchestrated by a cascade of specialized ubiquitin activating enzyme (E1), ubiquitin conjugating enzyme (E2), and ubiquitin ligase (E3) enzymes, are thought to control a wide range of cellular processes, and alterations in the ubiquitin–proteasome system have been associated with several degenerative disorders. In addition, the OPLL tissue of CXCL7-null mouse and its primary cells expressed the antibody to ubiquitin (linkage-specific K48). Our data clearly show decreased CXCL7 levels in patients with OPLL, and that OPLL developed in mice lacking CXCL7. Tumor necrosis factor receptor-associated factor (TRAF)6 expression was decreased in CXCL7-null mouse primary cells. Furthermore, K48 polyubiquitination was found in posterior longitudinal ligament ossified tissue and primary cells from CXCL7-null mice. We performed a phosphoproteomics analysis in CXCL7-deficient mice and identified increased phosphorylation of mitogen-activated protein kinase kinase (ME3K)15, ubiquitin protein ligase E3C (UBE3C) and protein kinase C (PKC) alpha, suggesting that ubiquitin-dependent degradation is involved in CXCL7 deficiency. Future studies in the CXCL7-null mouse model are, therefore, warranted to investigate the role of ubiquitination in the onset of OPLL. In conclusion, CXCL7 levels may be useful as a serum marker for the progression of OPLL. This study also suggests that increasing CXCL7 levels in patients can serve as an effective therapeutic strategy for the treatment of OPLL.

Usefulness of multiecho fast field echo MRI in the evaluation of ossification of the posterior longitudinal ligament and dural ossification of the cervical spine

Objectives

The diagnosis of ossification of the posterior longitudinal ligament (OPLL) on magnetic resonance imaging (MRI) is challenging. The purpose of this study is to evaluate the usefulness of the multiecho fast field echo (mFFE) MRI in the detection of ossification of the posterior longitudinal ligament and dural ossification (DO) of the cervical spine.

Methods

Sixty-three patients who underwent MRI with mFFE and CT for cervical spine were retrospectively evaluated. The presence of OPLL and DO on MR images was assessed by two independent readers. The sensitivity, specificity, and accuracy of MRI for detecting OPLL and DO were determined using CT as a reference standard. Image contrast ratios were obtained between the OPLL and perilesional structures on each sequence.

Results

There were 31 patients with OPLL and 13 DO lesions. The mean sensitivity, specificity, and accuracy of both readers were 94%, 81%, 88% for OPLL and 92%, 81%, 86% for DO, respectively. The contrast ratios for OPLL and intervertebral disc, spinal cord and cerebrospinal fluid were significantly superior on mFFE images, whereas those for OPLL and bone marrow were significantly inferior on mFFE images than those of T1-and T2-weighted images (p ≤ 0.016).

Conclusions

MRI with mFFE may be sufficient for the assessment of OPLL and DO, with good contrasts between OPLL and intervertebral disc, spinal cord, and cerebrospinal fluid.

Serum biomarkers in patients with ossification of the posterior longitudinal ligament (OPLL): Inflammation in OPLL

Backgroud

Ossification of the posterior longitudinal ligament (OPLL) is characterized by replacement of ligamentous tissue by ectopic new bone formation. OPLL causes narrowing of the spinal canal, resulting in neurological impairment. However, the pathogenesis of OPLL has not been fully elucidated. We investigated whether inflammation occurs in OPLL or not using high-sensitivity CRP (hs-CRP) in a case-control study.

Methods and findings

This study included 103 patients with OPLL in the patient group and 95 age- and sex-matched volunteers with degenerative spinal disease in the control group. Of the 103 OPLL patients, 88 patients who were available for more than 2 years follow-up were checked for OPLL progression. A blood sample was obtained and Hs-CRP, and other routine data, including total protein (TP), albumin (ALB), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), glucose (Glu), calcium (Ca), inorganic phosphate (Pi), white blood cell count (WBC), hemoglobin (Hb) and platelet (PLT), were analyzed. The data were compared between the patients with OPLL and the controls. The severity of the ossified lesions in the whole spine were evaluated by the ossification index (OS index) in patients with OPLL. The data were also compared between the patients with OPLL progression (the progression group) and the patients without OPLL progression (the non-progression group). In the results, the mean hs-CRP in the OPLL group was higher than that in the controls. The Pi in the OPLL group was lower than that in the control group. A negative correlation was found between the Pi and the OS index. The mean hs-CRP in the progression group was higher than that in the non-progression group. There was a positive correlation between the average length of the OPLL progression per year and the hs-CRP.

Conclusions

The results may suggest the occurrence of local inflammation in OPLL and the inflammation might cause OPLL progression. These facts are important for understanding the pathology of OPLL.

Ossification of the posterior ligament is mediated by osterix via inhibition of the β-catenin signaling pathway

Ossification of the posterior longitudinal ligament (OPLL) involves ectopic calcification of the spinal ligament preferentially at the cervical spine. OPLL is associated with different diseases and occurs by endochondral ossification, which is associated with the activity of different transcription factors. However, the pathogenesis of OPLL remains unclear. Here, we investigated the role of osterix (Osx), a transcription factor that functions downstream of Runx2 and is an important regulator of osteogenesis, in the process of OPLL in a dexamethasone (Dex)-induced model of spinal ligament ossification. Our results showed that Osx is upregulated in patients with OPLL and during the ossification of ligament cells in parallel with the upregulation of osteogenic markers including osteocalcin (OCN), alkaline phosphatase (ALP) and collagen-1 (Col-1). Dex-induced ossification of ligament cells was associated with the downregulation and inactivation of β-catenin, and these effects were offset by Osx knockdown. Activation of β-catenin signaling abolished the effect of Dex on ossification and the upregulation of osteogenic markers. Taken together, our results suggest that OPLL is mediated by Osx via a mechanism involving the Wnt/β-catenin signaling pathway, providing a basis for further research to identify potential targets for the treatment of OPLL.

Prevalence and Distribution of Ossified Lesions in the Whole Spine of Patients with Cervical Ossification of the Posterior Longitudinal Ligament A Multicenter Study (JOSL CT study)

Ossification of the posterior longitudinal ligament (OPLL) can cause severe and irreversible paralysis in not only the cervical spine but also the thoracolumbar spine. To date, however, the prevalence and distribution of OPLL in the whole spine has not been precisely evaluated in patients with cervical OPLL. Therefore, we conducted a multi-center study to comprehensively evaluate the prevalence and distribution of OPLL using multi-detector computed tomography (CT) images in the whole spine and to analyze what factors predict the presence of ossified lesions in the thoracolumbar spine in patients who were diagnosed with cervical OPLL by plain X-ray. Three hundred and twenty-two patients with a diagnosis of cervical OPLL underwent CT imaging of the whole spine. The sum of the levels in which OPLL was present in the whole spine was defined as the OP-index and used to evaluate the extent of ossification. The distribution of OPLL in the whole spine was compared between male and female subjects. In addition, a multiple regression model was used to ascertain related factors that affected the OP-index. Among patients with cervical OPLL, women tended to have more ossified lesions in the thoracolumbar spine than did men. A multiple regression model revealed that the OP-index was significantly correlated with the cervical OP-index, sex (female), and body mass index. Furthermore, the prevalence of thoracolumbar OPLL in patients with a cervical OP-index ≥ 10 was 7.8 times greater than that in patients with a cervical OP-index ≤ 5. The results of this study reveal that the extent of OPLL in the whole spine is significantly associated with the extent of cervical OPLL, female sex, and obesity.

Surgical results and prognostic factors of anterior cervical corpectomy and fusion for ossification of the posterior longitudinal ligament

Background

Mechanism of ossification of the posterior longitudinal ligament (OPLL) has not been elucidated clearly. Surgical decompression is usually necessary for the patients with neurological symptoms. Anterior decompression and resection of OPLL seems to be a radical surgical option, because the spinal cord is compressed from the anterior direction.

Methods

Among 229 patients who underwent ACF for OPLL between January 2001 and December 2007 in our hospital, a total of 133 patients responded to the invitation and made return visits, with a follow-up rate of 58.1%. For these patients, clinical data were collected from medical and operative records. Neurological status were evaluated by using the Japanese Orthopedic Association (JOA) scoring system. Radiological evaluations including C2-7 lordotic angle, sagittal vertical axis (SVA), occupying rate of OPLL, double-layer sign and high-intensity zone were obtained from all the patients. Complications and causes of revision surgery were also investigated. Correlations between the long-term surgical outcome and various prognostic factors were statistically analyzed.

Findings

Eighty-four males and forty-nine females completed the follow-up, with a mean age at operation of 56.8 years. The overall average JOA score significantly increased, with a mean recovery rate of 64.1%±14.2%. The mean C2-7 lordotic angle and SVA were also significantly improved, and fusion rate was satisfactory. The incidence of complications was consistent to the previous reports and most of them were controllable by suitable treatments. Multiple regression analysis showed that number of corpectmies and preoperative JOA score were important predictors of surgical outcome.

Conclusions

ACF is a reliable and effective method for treating OPLL patients in terms of neurological recovery, maintenance of radiological parameters, fusion rate and complications. Number of corpectomies and preoperative JOA score are important predictors for the clinical outcome when this procedure is used.

Whole exome sequencing implicates PTCH1 and COL17A1 genes in ossification of the posterior longitudinal ligament of the cervical spine in Chinese patients

Ossification of the posterior longitudinal ligament (OPLL) of the cervical spine is a complex multifactorial disease. Patients with OPLL commonly present with symptoms in their 40s or 50s. The genetic basis of OPLL remains poorly understood. Exome capture combined with massively parallel DNA sequencing has been proposed as an efficient strategy to search for disease-causing genes of both monogenic and multigenic disorders. To identify candidate pathogenic genes associated with OPLL, we performed whole exome sequencing (WES) on two unrelated southern Chinese OPLL patients. The entire DNA coding region of the candidate genes was amplified by PCR and Sanger sequenced. The common single nucleotide polymorphisms were analyzed by association studies. WES revealed p.T265S/PTCH1, p.P1232L/PTCH1, and p.T902S/COL17A1 mutants in the two female cases with mixed OPLL. These were confirmed by Sanger sequencing. p.P1232L/PTCH1, p.N1374D/COL17A1 and p.T902S/COL17A1 were subsequently identified in three males with continuous OPLL and one female with mixed OPLL. The association studies indicated that the SNPs rs805698 and rs4918079 in COL17A1 were significantly associated with OPLL. This study suggests that WES may be a practical approach to revealing significant genetic involvement in OPLL. Variants of the PTCH1 and COL17A1 genes may contribute to the development of OPLL.

Genomic study of ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament of the spine (OPLL) is a common disease after the middle age. OPLL frequently causes serious neurological problems due to compression of the spinal cord and/or nerve roots. OPLL occurs in patients with monogenic metabolic diseases including rickets/osteomalacia and hypoparathyroidism; however most of OPLL is idiopathic and is considered as a multi-factorial (polygenic) disease influenced by genetic and environmental factors. Genomic studies for the genetic factors of OPLL have been conducted, mainly in Japan, including linkage and association studies. This paper reviews the recent progress in the genomic study of OPLL and comments on its future direction.

Clinical results and intramedullary signal changes of posterior decompression with transforaminal interbody fusion for thoracic myelopathy caused by combined ossification of the posterior longitudinal ligament and ligamentum flavum

BACKGROUND

Surgical treatment of thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) is technically demanding, and the results tend to be unfavorable. Various operative approaches and treatment strategies have been attempted, and posterior decompression with transforaminal thoracic interbody fusion (PTTIF) may be the optimal method with which the anterior-posterior compression was removed in one step. It is comparatively less traumatic with fewer serious complications.

METHODS

Sixteen patients with thoracic myelopathy due to concurrent OLF and OPLL at the same level underwent PTTIF. We investigated clinical outcomes and neurological improvements. Magnetic resonance imaging (MRI) was performed on all patients preoperatively and postoperatively, and intramedullary signal changes were evaluated.

RESULTS

The mean operating time was 275 minutes, and the mean operative bleeding amount was 1031 ml. Cerebrospinal fluid leakage occurred in three patients and healed well after repair. Neurological symptom deterioration occurred in one patient, but the patient recovered to nearly the preoperative level after methylprednisolone treatment. The follow-up period ranged from 28 to 47 months. The mean score on the Japanese Orthopedic Association scale improved from 4.3±1.2 preoperatively to 7.3±1.7 at 3 months postoperatively to 8.5±1.5 at the final follow-up (P < 0.01), with a recovery rate of (63.6±20.0)%. Postoperative images showed a significant improvement in local kyphosis (P < 0.01). Eleven patients (68.8%) showed increased signal intensity (ISI) on preoperative T2-weighted MRI. At the final follow-up, the intramedullary ISI totally recovered in five patients. Neurological improvement was worse in patients with persistent ISI than in the other patients (P < 0.05).

CONCLUSIONS

PTTIF is an effective therapeutic option for combined OPLL and OLF and provides satisfactory neurological recovery and stabilized thoracic fusion through a single posterior approach. Intramedullary signal changes do not always indicate a poor prognosis; only irreversible ISI is correlated with a poor clinical result.

[Efficacy of intramedullary and extramedullary decompression on cervical ossification of the posterior longitudinal ligament with spinal cord signal change]

OBJECTIVE

To evaluate the clinical effect of different surgical approaches for treating cervical ossification of the posterior longitudinal ligament (OPLL) with spinal cord signal change.

METHODS

Thirty-eight patients with OPLL with spinal cord signal change were treated from January 2005 to January 2011. Surgical removal via an anterior approach or partial decompression was performed in 10 cases (group A), posterior approach open-door laminoplasty with decompression, bone grafting and internal fixation was performed in 12 cases (group B), and opening the cervical spinal meninges to relieve the pressure was performed in 16 cases (group C) on the basis of the procedures in group B. All the patients were followed up and the pre- and postoperative JOA scores, improvement ratio and inter-body implant fusion were evaluated. Imaging examinations including X-rays, CT and MRI were also performed pre- and postoperatively, and the surgical complications were recorded.

RESULTS

At 12 months postoperatively, the mean improvement rates in groups A, B, and C were 52.39%, 55.15%, and 60.32%, respectively, with the mean JOA scores of 13.54∓0.56, 13.56∓1.26, and 14.70∓1.41, respectively. The JOA scores and improvement rates significantly increased after the surgeries. One patient in group A became paraplegic after the operation with cerebrospinal fluid leakage, and one patient in group B and one in group C reported numbness of the upper limb. Group C showed a shorter postoperative recovery time without severe complications.

CONCLUSION

Posterior open-door laminoplasty, decompression, bone grafting and internal fixation can be an effective approach for treatment of cervical OPLL with spinal cord signal change and requires shorter rehabilitation time after the operation.

Combined ossification of the posterior longitudinal ligament at C2-3 and invagination of the posterior axis resulting in myelopathy

PURPOSE

Spinal stenosis at the C2-3 segment is a rare occurrence, and when it occurs myelopathy infrequently results. Furthermore, only a handful of cases involving congenital abnormalities of the posterior arch of the axis have been described resulting in cervical myelopathy many of which described simultaneous congenital abnormalities at adjacent levels and none of which identified ossification of the posterior longitudinal ligament (OPLL) at the same level. We report a case of a previously undescribed combination of abnormalities at the C2-3 segment resulting in clinical myelopathy.

METHODS

A 49-year-old Chinese male presented with a progressive cervical myelopathy (C-JOA score 11 immediately pre-op). Segmental OPLL at the C2-3 disk space was visible, together with invagination of the bilaterally hypoplastic C2 lamina into the spinal canal. Signal abnormalities of the spinal cord were evident on both T1 and T2 sequences.

RESULTS

The patient underwent a posterior decompression and instrumented fusion at C2-3 using pars screws at C2 and lateral mass screws at C3. Following surgery there was a rapid and significant improvement in the neurological symptoms, with the C-JOA score improving to 14 at final follow-up. A successful fusion was evident.

CONCLUSIONS

Deficiencies in the posterior arch of the axis are rare and have not previously been reported in conjunction with OPLL. Advanced imaging is helpful to define the abnormality and site of compression. In the setting of a progressive neurological dysfunction, surgical decompression and stabilization is a reasonable intervention and can be associated with neurological and symptomatic improvement.

Proline/arginine-rich end leucine-rich repeat protein converts stem cells to ligament tissue and Zn(II) influences its nuclear expression

Our objective was to facilitate ligament tissue reconstruction by characterizing the mechanism of expression of ligament tissue. To accomplish this, we searched for proteins specific to the tissue and introduced them into mesenchymal stem cells. In the two-dimensional phosphorescent gel electrophoresis, the spots in common with the normal human ligament tissue were selected after removing the spots of the normal bone tissue from those of the ossified tissue in the spinal ligament. Proline/arginine-rich end leucine-rich repeat protein (PRELP) was identified in ligament-specific locations by liquid chromatography-tandem mass spectrometry. Transfection of PRELP into mouse mesenchymal stem cells yielded ligament-like connective tissue comprised of parallel fibers. Thus, expression of the PRELP protein could reconstruct the ligament tissue. Since zinc-related proteins were found with high incidence as a result of an array analysis of PRELP's ProtoArray, it was considered that there is a relationship to the zinc metabolism. Tissue induction was mediated by the tumor necrosis factor (TNF)-α via the zinc pathway. PRELP may be a useful gene in syndesmoplasty, provided zinc is present for tissue reconstruction. Chromosome division becomes active with the addition of zinc, and rapid tissue induction takes place in the presence of zinc and TNF-α. Currently, the reconstruction of a ruptured ligament tissue is difficult, but we expect that the PRELP protein expression may facilitate this process. This study describes the discovery of the gene responsible for the differentiation of stem cells into ligament tissue. This important finding may lead to treatments for gonarthrosis, cruciate ligament, and periodontal ligament ruptures, and ossification of the posterior longitudinal ligament.

Inhibitory effect of YQHYRJ recipe on osteoblast differentiation induced by BMP-2 in fibroblasts from posterior longitudinal ligament of mice

Ossification of posterior longitudinal ligament (OPLL) is a common disease in Asian countries. Osteoblast differentiation in posterior longitudinal ligamentous fibroblast is a pathologic basis of OPLL. Nowadays, an effective pharmacotherapy for OPLL is still hunted for. YQHYRJ Recipe (YQHYRJ) is designed based on traditional Chinese medicine (TCM) theories, and previous clinic trials reported its effect on relieving syndromes of cervical spondylopathy. To clarify the YQHYRJ effect of OPLL on a cellular level, we induced mice fibroblasts from posterior longitudinal ligaments to differentiate into osteoblasts by human recombinant BMP-2, and treated them with YQHYRJ and its three sub-compounds: YQ, HY and RJ. YQHYRJ and the sub-compounds reduced the increase of fibroblast proliferation, mineralization, type I collagen secretion induced by BMP-2 via MTT, alizarin red staining and immunochemical examination. Moreover, these agents inhibited BMP-2 induced upregulation of ossification-related genes ALP, Col I and OC as well as BMP signal molecules Smad1, Smad 5 and Runx2 mRNA expression. These results suggested YQHYRJ to be effective in inhibiting osteoblast differentiation induced by BMP-2 in fibroblasts from posterior longitudinal ligament. YQHYRJ might be a promising medicine for preventing OPLL disease.

P2Y1 transient overexpression induced mineralization in spinal ligament cells derived from patients with ossification of the posterior longitudinal ligament of the cervical spine

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments. We previously reported that P2 purinoceptor Y1 (P2Y1) expression is elevated in the spinal ligament cells of OPLL patients, but the role of P2Y1 in the spinal ligament calcification process is unknown. To verify the hypothesis that P2Y1 expression causes ossification of the spinal ligaments, we forced expression of P2Y1 in spinal ligament cells obtained from OPLL and non-OPLL patients using a cytomegaloviral vector. The expression of mRNA and protein was investigated by quantitative real-time polymerase chain reaction and immunofluorescence staining, respectively. After transfection, bone morphogenetic protein-2 (BMP-2) and Sox9 mRNA expression was significantly increased in spinal ligament cells derived from OPLL patients (4.36- and 6.44-fold, respectively) compared with cells from non-OPLL patients (0.57- and 3.64-fold, respectively) 2 days after P2Y1 transient transfection. Furthermore, a statistically significant correlation was observed between BMP-2 and P2Y1 mRNA expression levels in cells obtained from OPLL patients but not from non-OPLL patients. Immunofluorescence analysis showed that BMP-2 and P2Y1 expression was increased in OPLL patients only, while Sox9 expression was increased in OPLL and non-OPLL patients. MRS2279, a selective P2Y1 antagonist, blocked the upregulation of Sox9 and BMP-2 after forced expression of P2Y1. Furthermore, 4 days after transient transfection of P2Y1, mineralization was observed only in spinal ligament cells from OPLL patients. These results suggest that P2Y1 expression plays an important role in ectopic bone formation in the spinal ligaments of OPLL patients.

[Morphologic and apoptotic changes of cervical posterior longitudinal ligament fibroblasts in response to in vitro mechanical stretch]

OBJECTIVE

To investigate the effect of mechanical stretch force on the morphologic and apoptotic changes of fibroblasts derived from the OPLL (ossification of posterior longitudinal ligaments) patients.

METHODS

The third passage cells were collected and subjected to 10% elongations cyclic mechanical stretching for 6 h and 24 h with Flexercell 4000(TM) strain unit. Their morphologic changes were observed and the post-stretching apoptotic rates quantified by flow cytometer. The gene expressions of alkaline phosphatase (ALP), collagen types I (COL I) and osteocalcin (OC) were examined.

RESULTS

The treated cells were arranged along the vertical direction of force. Stretch force led to a slight increase of apoptosis rate at 6 h and a significant increase of apoptosis rate at 24 h. No significant difference in cellular senescence was observed between control group and treated group. The mRNA expressions of ALP, COL I and OC were positively up-regulated by cyclic stretch at 24 h.

CONCLUSION

Stretching force can affect the cellular morphology, promote the osteogenic differentiation and enhance the cellular apoptosis.

[Effectiveness of transarticular approach in treating thoracic spinal stenosis of calcified ligament]

OBJECTIVE

To investigate the effectiveness of transarticular approach in treating thoracic spinal stenosis due to ossification of ligamentum flavum (OLF) and ossification of posterior longitudinal ligament (OPLL) at the same level.

METHODS

A retrospective analysis was performed in 35 patients with single-level thoracic spinal stenosis of calcified ligament who accepted transarticular approaching operation between January 2006 and March 2008. There were 12 males and 23 females with an age range of 40-67 years (mean, 58.6 years), including 16 cases of thoracic OLF, 11 cases of thoracic OPLL, and 8 cases of thoracic OPLL and OLF. The disease duration was 8-48 months (mean, 16 months). The affected segments included T2, 3 in 4 cases, T3, 4 in 3 cases, T4, 5 in 1 case, T6, 7 in 3 cases, T7, 8 in 1 case, T8, 9 in 2 cases, T9, 10 in 5 cases, T10, 11 in 9 cases, and T11, 12 in 7 cases. CT and MRI were taken to definite the ossification position and the condition of thoracic spinal stenosis. The Japanese Orthopaedic Association (JOA) score was 6.1 +/- 1.3 before operation. According to Otani scoring system, the results were excellent in 3 cases, good in 16 cases, fair in 11 cases, and poor in 5 cases.

RESULTS

All operations were successful, and no nerve injury occurred. All incisions healed at stage I. Cerebrospinal fluid leakage occurred in 5 cases, and recovered after symptomatic treatment. One case had epidural hematoma 6 hours after operation, and the muscle strength recovered after symptomatic treatment. All cases were followed up 1.5-2.6 years (mean, 2.1 years) and the symptoms were improved in different degrees; no neurological symptoms deteriorated and spinal instability occurred. The JOA score had a significant recovery at 3 months (9.2 +/- 1.8) and at last follow-up (9.6 +/- 2.3) when compared with preoperative value (P < 0.05). At last follow-up, the rate of the clinical improvement was 71.43% +/- 18.20%. According to Otani scoring system at last follow-up, the results were excellent in 12 cases, good in 15 cases, fair in 6 cases, and poor in 2 cases with an excellent and good rate of 77.14%, showing significant difference when compared with preoperative value (u = 2.711, P = 0.007).

CONCLUSION

The transarticular approach in treating thoracic spinal stenosis of calcified ligament can obtain good clinical results. Moreover, extra attention should be paid to during operation so as to avoid catastrophic spinal cord injury.

[Animal models for bone and joint disease. ttw (tiptoe walking), a model mouse of OPLL (ossification of the posterior longitudinal ligament of the spine)]

ttw (tiptoe walking), a known model mouse of OPLL (ossification of the posterior longitudinal ligament of the spine) is reviewed. ttw is a natural mutant which shows generalized ectopic calcification followed by ossification in the Achiles tendon, ear and spinal ligaments, etc. The trait is caused by a homozygous nonsense mutation in the gene for NPPS (nucleotide pyrophosphatase) , a cell-membrane enzyme that produces pyrophosphate. Its pathomechanism is the decrease of extracellular pyrophosphate due to insufficiency of NPPS. ttw is a excellent model for ectopic calcification and ossification. Several interesting genes related to ectopic calicification have been identified by studies using this mouse.

Treatment of cervical OPLL by cervical anterior fusion using autologous vertebral bone grafts

BACKGROUND

In anterior fusion, we use autologous bone grafts from cervical vertebral bodies and bioabsorptive screws to prevent graft extrusion (Williams-Isu method). We report the application of and indication for the Williams-Isu method for OPLL and present our clinical and radiological results.

METHODS

Using the Williams-Isu method, we treated 17 patients with cervical OPLL; 15 had segmental- and 2 had continuous-type OPLL. The median follow-up term was 24 months. The patients underwent anterior decompression and fusion at a single level (n = 8) or at two levels (n = 9). As a control, 17 patients with cervical spondylosis underwent anterior single-level decompression and fusion using the Williams-Isu method. Pre- and postoperative radiographs of the cervical spine were obtained in all patients, and the alignment of the whole cervical and fused segment and the height of the fused segment were compared.

RESULTS

All but one patient experienced alleviation of clinical symptoms without deterioration during the follow-up period. The recovery rate on the JOA score was 71.7%. The patient with continuous-type OPLL suffered postoperative neurological deterioration because of a remnant of the upper-level OPLL. Radiological studies confirmed the absence of bone graft dislocation and fracture, and of satisfactory bone fusion in all patients. There was no significant difference between the two patient groups with respect to whole spine alignment and the alignment and height of the fused segment.

CONCLUSIONS

The Williams-Isu method is useful for treating not only cervical spondylosis but also cervical segmental OPLL at one or two levels.

[Updates on ossification of posterior longitudinal ligament. Conservative treatments for OPLL]

Since the main pathology of OPLL in cervical spine is the myelopathy due to mechanical compression, any conservative treatment is not generally indicated for this pathology. However, some of the cases with slight extent of myelopathy show no aggravation after the conservative treatments. Therefore, conservative treatments are indicated through considering the various aspects of the each case's conditions, such as the severity of myelopathy, spinal cord deformity, the presence of dynamic factors, and others (age, duration of myelopathy, patient's motivation, patient's social life-style, and the general conditions) . Furthermore, the decision making or the differential diagnosis with pathologies with the similar symptoms to cervical spine is performed with the analysis of the effectiveness by the conservative treatments.

[Updates on ossification of posterior longitudinal ligament. Ossification front of posterior longitudinal ligament and cellular biological assessment of chronic mechanical compressed spinal cord]

Mechanisms of ossification processes, pathological changes, and treatment/assessment of myelopathy symptoms because of ossification of the posterior longitudinal ligament (OPLL) remain obscure. Enchondral ossification process of OPLL was closely associated with degenerative changes of elastic fibers and cartilage formation, together with the appearance of metaplastic hypertrophic cartilage cells and neovascularization. There are differences in expression degrees of cytokines and transcription factors between mixed and localized OPLL. While the chronic compressed spinal cord may have plasticity ; the use of stem cell implants, supplementation of neurotrophic factors, in addition to surgical treatment, may bring a better clinical outcome,encouraging the development of these basic research studies. Assessment using new imaging techniques needs to determine the affected level and judge the severity of symptoms.

[Anterior multilevel corpectomy for the treatment of severe ossification of posterior longitudinal ligament in the cervical spine]

OBJECTIVE

To discuss the surgical indications, outcomes and complications of anterior multilevel corpectomy for the treatment of severe ossification of posterior longitudinal ligament (OPLL) in the cervical spine.

METHODS

Between April 2006 and March 2008, a total of 25 patients (20 males and 5 females, age range: 42 - 75 yr, mean: 53. 2 yr) underwent anterior multilevel corpectomy for severe ossification of posterior longitudinal ligament in the cervical spine. Radiological studies showed that the type of OPLL was distributed as follows: 7 local, 5 segmental, 8 continuous and 5 mixed. The OPLL extended an average of 2. 8 vertebrae (2 - 4) and the stenotic rate of spinal canal was 68.4% (50% - 97%). After corpectomy and removal of OPLL, titanium mesh cage and anterior plate were employed to restore cervical stability in all patients.

RESULTS

Among these patients, 16 underwent two-level corpectomy and 9 three-level corpectomy. After a follow-up of 2 - 18 months, the mean JOA score increased from 9. 3 (5 - 12) points pre-operation to 14.2 (11 - 16) points post-operation. The mean improvement rate of neurological status was 63.2% (22.2% - 87.5%). The complications included CSF leakage in 6 cases (intermittent CSF pseudocyst in 4), nerve root palsy in 2, hematoma in 1 and transient neurological deterioration in 1.

CONCLUSION

Anterior multilevel corpextomy can achieve a better clinical outcome in the treatment of severe cervical ossification of posterior longitudinal ligament. But it is technically demanding and carries a higher risk.

Anterior cervical pedicle screw and plate fixation using fluoroscope-assisted pedicle axis view imaging: a preliminary report of a new cervical reconstruction technique

Anterior procedures in the cervical spine are feasible in cases having anterior aetiologies such as anterior neural compression and/or severe kyphosis. Halo vests or anterior plates are used concurrently for cases with long segmental fixation. Halo vests are bothersome and anterior plate fixation is not adequately durable. We developed a new anterior pedicle screw (APS) and plate fixation procedure that can be used with fluoroscope-assisted pedicle axis view imaging. Six patients (3 men and 3 women; mean age, 54 years) with anterior multisegmental aetiology were included in this study. Their original diagnoses comprised cervical myelopathy and/or radiculopathy (n = 4), posterior longitudinal ligament ossification (n = 1) and post-traumatic kyphosis (n = 1). All patients underwent anterior decompression and strut grafting with APS and plate fixation. Mean operative time was 192 min and average blood loss was 73 ml. Patients were permitted to ambulate the next day with a cervical collar. Local sagittal alignment was characterised by 3.5 degrees of kyphosis preoperatively, which improved to 6.8 degrees of lordosis postoperatively and 5.2 degrees of lordosis at final follow-up. Postoperative improvement and early bony union were observed in all cases. There was no serious complication except for two cases of dysphagia. Postoperative imaging demonstrated screw exposure in one screw, but no pedicle perforation. APS and plate fixation is useful in selected cases of multisegmental anterior reconstruction of cervical spine. However, the adequate familiarity and experience with both cervical pedicle screw fixation and the imaging technique used for visualising the pedicle during surgery are crucial for this procedure.

Classification and management of the tandem ossification of the posterior longitudinal ligament and flaval ligament

OBJECTIVE

To provide appropriate guidelines for treatment of tandem ossification of the posterior longitudinal ligament (OPLL) and flaval ligament (OFL). Data sources Published articles about OPLL and OFL were selected using Medline and Embase electronic databases. Study selection An English literature search from January 1980 to December 2006 was conducted. Because many reported cases were incorporated in OFL studies, the key words for search were OFL or OFL and OPLL. The first step revealed 93 studies of which 13 reports of tandem OPLL and OFL (tandem ossification) were selected.

RESULTS

All studies were case series or case report and advocated that the primary therapy for tandem ossification should be operative. The clinical outcomes of surgery were evaluated in most reports, predominantly using the JOA scores. Gender is the only factor which has prognostic value. A higher proportion of women was found in the failure group. A two-stage classification of tandem ossification was developed to relate diagnosis to outcome.

CONCLUSIONS

All patients with suspected ossification of the spinal ligaments should undergo routine MRI screening of the whole spine. The correlation of the classification with surgical treatments needs further studies to validate its usefulness.

[The strategy of posterior decompression and re-establishing the insertion of extensor for ossification of posterior longitudinal ligament involved in C(2)]

OBJECTIVE

To investigate an approach of posterior cervical spinal canal decompression and re-establishing the insertion of extensor, aim at the ossification of the posterior longitudinal ligament (OPLL) involved in C(2).

METHODS

From 2002 to 2006, 10 patients with OPLL involved in C(2) underwent open-door laminoplasty, with the posterior cervical ligamentous complex and the insertion of extensor reconstructed on C(2), were reviewed retrospectively. The range of decompression was from C(2) to C(7). The sagittal diameter of C(2) vertebral canal, alignment of the cervical spine (C(2)-C(7) angle), and JOA score before and after operation were contrasted respectively.

RESULTS

All patients were followed up, average 14 months. Before the operation, the average sagittal diameter of C(2) vertebral canal was 5.6 mm (4 - 8.8 mm), JOA score was 9.6 scores (6 - 12 scores), C(2)-C(7) angle was 6.5 degrees (-2 degrees - 12 degrees ). After the operation, the average sagittal diameter of C(2) vertebral canal was 13.4 mm (10 - 18.2 mm, P < 0.01), JOA score was 10.9 scores (8 - 14 scores) and the C(2)-C(7) angle was 7.4 degrees (3 degrees - 14 degrees ) in earlier. Finally, the JOA score was 13.2 scores (10 - 17 scores, P < 0.05), and the C(2)-C(7) angle was 7.0 degrees (2 degrees - 15 degrees , P > 0.05) at last.

CONCLUSIONS

The open-door laminoplasty, with an approach of the posterior cervical ligamentous complex and the insertion of extensor reconstructed, is an appropriate method for treating OPLL involved in C(2). This process keeps the cervical curve in a better way, and decompresses the spinal canal effectively.

Hypertrophic change of facet joint in the cervical spine

BACKGROUND

There have been few studies on degenerative changes of the cervical facet joint. This study was conducted to examine the image and clinical characteristics of patients with cervical facet hypertrophy and the significance of such characteristics.

MATERIALS AND METHODS

The subjects were 215 patients with degenerative disease of the cervical spine, and they were divided into a hypertrophic change (+) group (32 patients) and a hypertrophic change (-) group (183 patients). We defined that if the distance between the tangential line on the posterior border of the vertebral body and the tip of the superior articular process was 7 mm or over by CT, it was regarded as hypertrophic change (+). Data was analyzed using Fisher's exact test, and differences were considered significant at p<0.05.

RESULTS

The level at which hypertrophic change of the facet joint was observed was C3/4 in eight patients, C4/5 in 14, C5/6 in six, C6/7 in one, C3/4 + C4/5 in one, and C4/5 + C5/6 in two. Of the 32 patients in the hypertrophic change (+) group, 30 had an unilateral hypertrophic change. There was a significantly (p<0.05) greater proportion (28 of 32 patients, 87.5%) of males in the hypertrophic change (+) group than in the hypertrophic change (-) group, and neck pain was observed significantly more frequently in the hypertrophic change (+) group (25 of 32 patients, 78.1%).

CONCLUSION

The results showed that hypertrophic change of the facet joint occurred at mid-level of the cervical spine, usually unilaterally, was more frequent in males, and was associated with neck pain.

Cervical myelopathy caused by soft-tissue mass in diffuse idiopathic skeletal hyperostosis

A rare case of cervical spinal cord compression in diffuse idiopathic skeletal hyperostosis (DISH or Forestier's Disease) caused by a craniocervical mass of soft-tissue is reported. The objective is to describe an uncommon mechanism of spinal cord compression in DISH. Three weeks after a cardiac infarction a 69-year-old man slowly developed spastic tetraparesis. Magnetic resonance tomography showed a craniocervical tumor compressing the spinal cord and a massive DISH of the cervical spine. An extended mass of yellowish amorphous material was removed from between the dura, the posterior odontoid process and the posterior aspect of vertebral body C2 reaching to the upper part of C3.The histologic appearance indicated connective tissue and cell-degenerated cartilaginous tissue. There was no inflammatory component and no evidence of neoplasia. No ossification of the posterior longitudinal ligament (OPLL) was found. After removal and craniocervical stabilization the patient's neurologic function improved remarkably. The increase of mechanical stress on the atlantoaxial segment and enhanced proliferation reaction of the connective tissue in DISH are suggested as the underlying pathomechanisms in the formation of this soft-tissue mass.

Multilevel cervical oblique corpectomy in the treatment of ossified posterior longitudinal ligament in the presence of ossified anterior longitudinal ligament

STUDY DESIGN

Clinical study.

OBJECTIVE

To highlight the value of the oblique corpectomy in managing patients with cervical myelopathy caused by extensive ossified posterior longitudinal ligament (OPLL) who also have a coexisting ossified anterior longitudinal ligament (OALL).

SUMMARY OF BACKGROUND DATA

OPLL, OALL, and diffuse idiopathic skeletal hyperostosis (DISH) may coexist, and the surgical treatment is varied. Patients with cervical myelopathy who are asymptomatic for the OALL may be managed by either anterior or posterior approaches, while those with dysphagia are best managed by an anterior approach that can deal with both pathologies simultaneously. The OALL resection is indicated only if symptomatic. The central corpectomy, while a good option for anterior decompression, requires complex reconstruction procedures. The oblique corpectomy preserves the ventral half of the vertebral body and does not require stabilization.

METHODS

In a series of 135 patients undergoing multilevel oblique corpectomy for cervical myelopathy, 3 had OPLL with massive OALL that was asymptomatic. The OPLL was removed using microdrills while preserving the OALL. Preoperative and postoperative MR imaging assessed cord compression and spinal alignment, whereas dynamic plain roentgenography assessed stability. Patients were assessed clinically for signs of dysphagia and dysphonia.

RESULTS

The cervical myelopathy improved in all 3 patients at a follow-up of 3 years, 1 year, and 6 months, respectively, with no development of dysphagia. One patient had a Horner's syndrome that improved by 6 months and another had a C5 radiculopathy that was improving by 6 months. Imaging showed good decompression of the spinal cord, with no kyphosis or instability.

CONCLUSION

The oblique corpectomy is a surgical option in patients with asymptomatic OALL in the setting of progressive myelopathy due to OPLL with intrinsic stability as a result of their OALL. This technique avoids a multilevel central corpectomy that is associated with significant instability often requiring reconstructive procedures.

Ossification of the posterior longitudinal ligament of the cervical spine: histopathological findings around the calcification and ossification front

OBJECT

The authors studied the histological and immunohistochemical features of ossified posterior longitudinal ligament (PLL) of the cervical spine, especially in the calcification and ossification front.

METHODS

Samples of en bloc ossified PLL plaque obtained in 31 patients were stained with H & E and immunohistochemically prepared for collagens (types I and II), vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-beta, and bone morphogenetic protein (BMP)-2, and by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method for apoptosis.

RESULTS

Enchondral ossification was evident between the ligamentous enthesis and deep layer of the ligament, with irregularly disorganized arrangement of elastic fibers in association with advancement of the degenerative process. In the ossification front, many hypertrophic metaplastic chondrocytes were noted in the ossifying plaque immediately contiguous to the ligament fibers, together with a considerable degree of neovascularization. Both TGFbeta and BMP-2 were highly expressed in metaplastic hypertrophic chondrocytes in the ossification front, and BMP-2 was also expressed in fibroblastic cells near the ossified PLL plaque. Expression of type I collagen was significant in the matrix of the ossified PLL lesion, whereas that of type II was marked in metaplastic chondrocytes in the ossification front. Apoptotic hypertrophic chondrocytes were observed mainly in the fibrocartilaginous area near the calcification front.

CONCLUSIONS

The enchondral ossification process in the ossified PLL was closely associated with degenerative changes of elastic fibers and cartilaginous cartilage formation, together with the appearance of metaplastic hypertrophic cartilage cells and neovascularization. The authors also found that VEGF-positive metaplastic chondrocytes in the ossification front and different expression patterns of collagens probably play some role in the extension of the ossified PLL from the ossification front.

Immunohistochemical demonstration of advanced glycation end products and the effects of advanced glycation end products in ossified ligament tissues in vitro

STUDY DESIGN

This study correlates advanced glycation end products with ossified ligament tissues of the cervical spine in vitro.

OBJECTIVE

To investigate the effect of advanced glycation end products on ossification of the spinal ligaments in vitro.

SUMMARY OF BACKGROUND DATA

We have hypothesized that an accumulation of advanced glycation end products in the spinal ligament might result in some observable change in specific growth factors responsible for ossification in the spinal ligaments.

METHODS

Samples of the posterior longitudinal and yellow ligaments were harvested from patients (n = 5) with ossification of the posterior longitudinal ligament, and analyzed for the presence of advanced glycation end products and their receptor advanced glycation end product receptor by immunohistochemistry. Real-time polymerase chain reaction (PCR) was used to quantify the messenger ribonucleic acid (mRNA) levels of bone morphogenetic protein (BMP)-2, BMP-7, alkaline phosphatase, an osteoblast-specific transcription factor 1 (Cbfa1), and osteocalcin from yellow ligament cells treated with advanced glycation end products.

RESULTS

Immunohistochemical analysis revealed that advanced glycation end products and advanced glycation end product receptor were localized to within the posterior longitudinal and yellow ligaments. Advanced glycation end products were found to increase significantly the expression of BMP-2, BMP-7, Cbfa1, and osteocalcin at the mRNA levels after treatment with advanced glycation end products (1 microg/mL).

CONCLUSIONS

This is the first report to investigate the correlation, if any, between the ossified spinal ligament and advanced glycation end products. These results suggested that accumulation in advanced glycation end products and their interaction with advanced glycation end product receptor were 1 of the important risk factors in the process of ossification in the spinal ligaments.

[Effect of modified unilaterally-open expansive laminoplasty using bridge grafting and restructing posterior ligamentous complex methods on axial symptoms and cervical curvature change]

OBJECTIVE

To explore if the modified unilaterally-open expansive laminoplasty using bridge grafting and reconstructing posterior ligamentous complex methods is effective in preventing persisting axial symptoms, restriction of neck motion, and loss of cervical curvature.

METHODS

From June 2000 to October 2005, 138 patients with cervical spondylotic myelopathy underwent this procedure. Of them, 78 who were followed for more than 2 years (group A) were included in this study. Another 69 patients who underwent conventional unilaterally open-door laminoplasty served as controls (group B). The JOA scores and the incidence of newly developed or deteriorated axial symptoms were recorded. Preoperative and postoperative ranges of neck motion were measured on lateral flexion and extension radiographs. Preoperative and postoperative cervical curvature indices were calculated according to Ishihara's method.

RESULTS

The patients of group A were followed 24-44 months (mean 33 months), and the patients of group B were followed 24-53 months(mean 35 months). The operative time was 114+/-20 min in group A and 70+/-25 min in group B, showing statistically significant difference (P<0.05). The operative blood loss was 280+/-72 ml in group A and 210+/-80 ml in group B (P>0.05). According to JOA scoring, the average recovery rates were 67.0%+/-17.3% in group A and 65.0%+/-21.4% in group B (P>0.05). Postoperative development or deterioration of axial symptoms occurred in 12% of patients in group A and 51% of patients in group B, showing statistically significant difference (P<0. 05). Postoperative range of neck motion was 88.0%+/-10.1% of the preoperative one in group A and 64.0%+/-16.3% in group B (P< 0.05). There was no significant difference between preoperative (15.3+/-8.2) and postoperative (13.5+/-9.3) cervical curvature index in group A, whereas the mean value of postoperative index (11.1+/-5.7) was significantly smaller than that of preoperative one (17.2+/-13.5) in group B (P<0.05).

CONCLUSION

This new procedure was less invasive to the posterior extensor mechanism than the conventional unilaterally-open laminoplasty and was effective in preventing postoperative morbidities.

Disorders of Tumoral Calcification of the Spine

Tumoral calcium pyrophosphate dihydrate crystal deposition disease and tumoral calcinosis (TC) are rare non-neoplastic conditions which may cause symptoms of spinal cord compression when they manifest in the perispinal tissues. There is little information available to compare these conditions with each other. We report a case of a patient with such a calcified mass impinging on the spinal cord. A 39-year-old woman on hemodialysis presents with progressive quadriparesis and monoplegia and is found to have a large calcified mass impinging on the spinal cord at the level of C3-4. The mass is excised by an anterior approach with corpectomy and fusion. Pathology was tumoral calcium pyrophosphate dihydrate crystal deposition disease versus TC. Both conditions are very rare in the perispinal tissues with 21 reported cases of tumoral calcium pyrophosphate dihydrate deposition disease and 39 cases of TC. Both cause compressive symptoms depending on the site of occurrence. Tumoral calcium pyrophosphate deposition disease is characterized by smaller, round, masses typically in ligamentous structures which may erode into adjacent bone. Tumoral calcinosis displays larger, lobulated, irregular lesions which do not erode into bone. Either lesion may contain calcium pyrophosphate dihydrate or hydroxyapatite. Treatment is surgical decompression, though lesions may recur.

Thoracic myelopathy in Japan: epidemiological retrospective study in Miyagi Prefecture during 15 years

Thoracic myelopathy is defined as spinal cord compression in the thoracic region, leading to sensory and motor dysfunctions in the trunk and lower extremities, and can be caused by various degenerative processes of the spine. Thoracic myelopathy is rare, and there are many unsolved problems including its epidemiological and clinical features. We have established a registration system of spinal surgeries, which covered almost all surgeries in Miyagi Prefecture, and enrolled the data of 265 patients with thoracic myelopathy from 1988 to 2002. The annual rate of surgery gradually increased and averaged 0.9 per 100,000 inhabitants, which was less than 1/10 of that for cervical myelopathy. About 20 patients with thoracic myelopathy are operated on in Miyagi Prefecture each year. It frequently develops in middle-aged males. About half of the cases were caused by ossification of the ligamentum flavum, followed by ossification of the posterior longitudinal ligament, intervertebral disc herniation and posterior spur. Patients usually noticed numbness or pain in the legs and the preoperative duration was long, averaging 2 years. Its symptomatic similarities to lumbar disorders might cause difficulty in making a correct diagnosis. Since thoracic myelopathy can markedly restrict the activities of daily life, even general physicians should recognize this entity.

An ultrastructural study on the ligamentum flavum of the cervical spine in patients with ossification of the posterior longitudinal ligament

Some histological analyses of the ossification of the posterior longitudinal ligament (OPLL) have been reported, but no ultrastructural studies of the ligamentum flavum (LF) in patients with OPLL have been published to date. To understand the pathology of the ossification of the spinal ligament, we examined, by electron microscopy, ultrastructural changes in the LF in cases of OPLL and made a comparison with the LF in cervical spondylotic myelopathy (CSM). Subjects were three men and two women with cervical OPLL who underwent longitudinal spinous process-splitting laminoplasty. During surgery, a small piece of the LF was collected from C2-C3 to C7-T1 and was then analyzed by light and electron microscopy. We observed atrophic elastic bundles with a two-layer structure and disarrangement, a partially torn area, the disappearance of microfibrils, and an enlarged interstitium with an irregular alignment of collagen fibrils. We observed some properties of a cell preceding its death: the initial phase may be the disappearance of the plasma-membrane, followed by the scattering of many organellae around its degenerated nucleus. Finally, many extracellular plasma membrane-invested particles that resemble matrix vesicles remain there without phagocytosis. These results suggest that ultrastructural abnormalities exist in the spinal ligament in cases of ossification of the spinal ligament.

How does the ossification area of the posterior longitudinal ligament progress after cervical laminoplasty?

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To investigate the progression pattern of ossification of the posterior longitudinal ligament (OPLL) after cervical laminoplasty.

SUMMARY OF BACKGROUND DATA

OPLL is a progressive disease, and an increased area of ossification affects the surgical results after laminoplasty. However, it is uncertain how the ossification area progresses with time after surgery.

METHODS

Fifty-five patients who were available for serial radiographs of more than 5 years were included. The extent of ossification in the longitudinal axis was assessed using computer software. The associations between the progression of OPLL and the clinical and radiologic data were analyzed.

RESULTS

Forty-one patients had OPLL progression. The patients were divided into three groups according to the pattern of progression. Group 1 consisted of patients 40 to 49 years of age with continuous or mixed type, showing slow progression at the beginning, then fast. Group 2 consisted of patients older than 50 years with continuous or mixed type, showing rapid progression at the beginning and then slow. The patients in Group 3 had segmental type with no or slight progression.

CONCLUSIONS

We speculated that the progression of OPLL decreases as the patient ages. These findings will be important for the management of patients with OPLL after surgery.

A review of factors predictive of surgical outcome for ossification of the ligamentum flavum of the thoracic spine

OBJECT

Ossification of the ligamentum flavum (OLF) is a pathological condition that affects the ligament and causes slowly progressive myeloradiculopathy in adults. Although OLF has been regarded as endemic to East Asian countries, studies from outside these areas have increasingly been reported. Because of long-standing compression of the spinal cord by OLF, a patient's functional prognosis may not always be favorable, and attempts have been made in recent studies to identify clinical factors that are predictive of the surgical outcome of patients with thoracic OLF.

METHODS

The authors conducted a review of the literature published in the English, Japanese, and Korean languages. They examined studies in which correlation between clinical factors and outcome was statistically evaluated. The clinical factors included sex, age, level of the ossified ligamentum flavum, number of segments affected by OLF, coexisting ossification of the posterior longitudinal ligament (OPLL) or other spinal disorders, preoperative duration of symptoms, preoperative neurological score, computed tomography (CT)-based classification, and the presence of intramedullary high signal intensity on T2-weighted magnetic resonance images.

CONCLUSIONS

The clinical factors that are unlikely to be predictive of outcome include sex, age, level of the ossified lesion, number of OLF-affected segments, coexisting OPLL, CT classification, and the presence of high signal intensity. It is unclear whether the preoperative duration of symptoms or neurological score is predictive of outcome because the results have been inconsistent among the studies. Analysis of the more recent literature, however, suggests that these two factors are predictive of outcome. The use of a neurological score should be standardized so that compilation and comparison of data can be facilitated.

Repetitive tensile stress to rat caudal vertebrae inducing cartilage formation in the spinal ligaments: a possible role of mechanical stress in the development of ossification of the spinal ligaments

Object

Mechanical stress has been considered one of the important factors in ossification of the spinal ligaments. According to previous clinical and in vitro studies, the accumulation of tensile stress to these ligaments may be responsible for ligament ossification. To elucidate the relationship between such mechanical stress and the development of ossification of the spinal ligaments, the authors established an animal experimental model in which the in vivo response of the spinal ligaments to direct repetitive tensile loading could be observed.

Methods

The caudal vertebrae of adult Wistar rats were studied. After creating a novel stimulating apparatus, cyclic tensile force was loaded to rat caudal spinal ligaments at 10 N in 600 to 1800 cycles per day for up to 2 weeks. The morphological responses were then evaluated histologically and immunohistochemically.

After the loadings, ectopic cartilaginous formations surrounded by proliferating round cells were observed near the insertion of the spinal ligaments. Several areas of the cartilaginous tissue were accompanied by woven bone. Bone morphogenetic protein–2 expression was clearly observed in the cytoplasm of the proliferating round cells. The histological features of the rat spinal ligaments induced by the tensile loadings resembled those of spinal ligament ossification observed in humans.

Conclusions

The findings obtained in the present study strongly suggest that repetitive tensile stress to the spinal ligaments is one of the important causes of ligament ossification in the spine.

Postoperative Changes at the Lower End of Cervical Laminoplasty

INTRODUCTION

C3-C7 laminoplasty has been the standard treatment for cervical myelopathy, although several recent reports described C3-C6 laminoplasty for preserving the muscles inserting in C7 and reducing postoperative axial symptoms. However, postoperative changes at C6/C7 of the lower end of C3-C6 laminoplasty, especially regarding a possibility of postoperative spinal canal narrowing have not been measured. The purpose of this study was to clarify postoperative changes at the lower end of laminoplasty.

METHODS

Pre and postoperative spinal dura diameter at the lower end of conventional C3-C7 laminoplasty using MRI, and the related factors for spinal dura diameter and the causes of postoperative dura narrowing were investigated.

RESULTS

At the last follow-up after C3-C7 laminoplasty, dura diameter at C7/T1 was significantly wider after operation than before operation, and postoperative narrowing of dura diameter, which was found in 20% of patients, was a maximum amount of one millimeter. No pre and postoperative factor significantly correlated with dura diameter at C7/T1. The causes of postoperative narrowing at the lower end of laminoplasty were disc protrusion and/or posterior scar, or segmental angulation of the spinal cord.

CONCLUSION

In conclusion, the presence of preoperative subarachnoid space over one millimeter at C6/C7 may be able to be one of the radiological indications for C3-C6 laminoplasty.

Current Topics in Pharmacological Research on Bone Metabolism: Molecular Basis of Ectopic Bone Formation Induced by Mechanical Stress

Ectopic bone formation (EBF) is frequently found in various tissues and affects the prognosis of diseases accompanied by EBF. Although the mechanism of EBF remains unclear, several local factors that influence the progression of EBF have been proposed. We have been focusing on the role of mechanical stress as a local factor in EBF in spinal ligament tissues, that is, ossification of the posterior longitudinal ligament (OPLL), which causes serious neurological deficiencies. Transcriptome analyses revealed that the expressions of several marker genes related to bone remodeling were enhanced after exposure of ligament cells derived from OPLL patients (OPLL cells) to cyclic stretching as a type of mechanical stress. However, no significant alterations in gene expressions were detected after cyclic stretching of ligament cells derived from non-OPLL patients. OPLL cells exposed to cyclic stretching released several autocrine/paracrine factors that are known to mediate bone remodeling. These results suggest that OPLL cells have been transformed into cells that are highly sensitive to mechanical stress, which may induce the progression of OPLL. These observations provide information regarding the role of mechanical stress in the process of EBF.

Current Topics in Pharmacological Research on Bone Metabolism: Promyelotic Leukemia Zinc Finger (PLZF) and Tumor Necrosis Factor-α-Stimulated Gene 6 (TSG-6) Identified by Gene Expression Analysis Play Roles in the Pathogenesis of Ossification of the Posterior Longitudinal Ligament

To understand the molecular pathogenesis of ossification of the posterior longitudinal ligament of the spine (OPLL), an ectopic bone formation disease, we performed cDNA microarray analysis on cultured ligament cells from OPLL patients to understand the molecular pathogenesis of OPLL. We identified promyelotic leukemia zinc finger (PLZF) as one of up-regulated genes and tumor necrosis factor-alpha-stimulated gene 6 (TSG-6) as one of down-regulated gene during osteoblastic differentiation. We investigated the roles of PLZF in the regulation of osteoblastic differentiation of human mesenchymal stem cells (hMSCs) and C2C12 cells. siRNA-mediated gene-silencing of PLZF resulted in a reduction of the expression of osteoblast-specific genes such as the alkaline phosphatase, collagen 1A1, Runx2/CBFA1, and osteocalcin genes in the presence of osteogenic differentiation medium (OS) in hMSCs. The overexpression of PLZF induced CBFA1 induction, suggesting that PLZF is an upstream regulator of CBFA1 and thereby participates in promoting the ossification of spinal ligament cells in OPLL patients. Adenovirus-mediated TSG-6 overexpression in hMSCs resulted in suppression of osteoblastic differentiation induced by either BMP-2 or OS. TSG-6 can bind to BMP-2 directly and thereby could inhibit BMP-2 signaling. Taken together, these findings indicate that PLZF and TSG-6 play important roles in early osteoblastic differentiation.