Association between serum leptin and bone metabolic markers, and the development of heterotopic ossification of the spinal ligament in female patients with ossification of the posterior longitudinal ligament

Association between diabetes mellitus and ossification of the spinal ligament: a systematic review and meta-analysis

PURPOSE

Ossification of the spinal ligament (OSL) is a spinal disorder characterized by abnormal bone formation in the spinal ligaments. Although clinical studies suggested that diabetes mellitus (DM) was associated with OSL, no consistent conclusion was drawn about the relationship between DM and the onset of OSL.

METHODS

Studies with data on DM and OSL were retrieved by searching PubMed, Embase, Web of Science, and Cochrane Library from inception to August 23, 2023. Pooled estimates of odds ratios (ORs) with 95% confidence interval (95% CI) were calculated using random-effects models. Statistical analyses were performed by R 4.2.2 software.

RESULTS

A total of 17 studies with 70,945 participants were included. The quantitative findings demonstrated that a higher risk of DM was related to the onset of OSL (OR = 2.19, 95% CI: 1.27-3.79, p = 0.008). Subgroup analysis showed a higher rate of DM in OSL patients from Japan (OR = 3.29, 95% CI: 1.51-7.17, [Formula: see text] = 0.009) than from other regions. Moreover, patients with OSL had a higher rate of DM in age < = 60 group (OR = 3.46, 95% CI: 1.14-10.50, p = 0.035) than age > 60 group (OR = 2.26, 95% CI: 1.07-4.79, p = 0.036).

CONCLUSION

DM is significantly associated with an increased risk of developing OSL, especially in Japanese and people under 60 years old. Further studies with more participants were warranted to confirm the findings and provide new insights into the prevention and treatment of OSL.

Adipokine dysregulation as an underlying pathology for diffuse ectopic ossification of spinal posterior longitudinal ligament in patients with obesity

BACKGROUND CONTEXT

Growing evidence suggests that obesity is implicated in the progression of heterotopic ossification of the posterior longitudinal ligament of the spine (OPLL), a major cause of myelopathy in Asians. However, it remains unclear whether dysregulation of adipokine production due to fat accumulation contributes to OPLL progression.

PURPOSE

To determine whether adipose-derived biochemical signals are associated with OPLL development or severity.

STUDY DESIGN/SETTING

A nationwide, multicenter, case-control study.

PATIENT SAMPLE

Patients with symptomatic thoracic OPLL (T-OPLL) who received treatment between June 2017 and March 2021 and 111 controls without OPLL.

OUTCOME MEASURES

OPLL severity index based on whole-spine computed tomography.

METHODS

Serum concentrations of adipokines, including leptin (Lep), tumor necrosis factor α (TNFα), and adiponectin (Adpn), as well as the Adpn/Lep ratio-an indicator of adipokine production dysregulation-were compared between the multiple-region OPLL and the single-region OPLL groups. Regression analysis was performed to examine the correlation between adipokine concentrations and OPLL severity index, which was calculated using whole-spine computed tomography images of 77 patients with T-OPLL within 3 years of onset. Using propensity score matching, the adipokine profiles of 59 patients with T-OPLL were compared with those of 59 non-OPLL controls.

RESULTS

Patients with multiple-region OPLL exhibited a higher body mass index (BMI), lower serum Adpn/Lep ratio, and higher serum concentration of osteocalcin (OCN) than those with single-region OPLL. The OPLL severity index exhibited a weak positive correlation with BMI and serum Lep levels and a weak negative correlation with the Adpn/Lep ratio. Serum TNFα and OCN concentrations were significantly higher in patients with T-OPLL than in controls with similar age, sex, and BMI.

CONCLUSIONS

Patients with diffuse OPLL over the entire spine are often metabolically obese with low Adpn/Lep ratios. In patients with OPLL, TNFα and OCN serum concentrations were essentially elevated regardless of obesity, suggesting a potential association with OPLL development. Considering the absence of therapeutic drugs for OPLL, the findings presented herein offer valuable insights that can aid in identifying therapeutic targets and formulating strategies to impede its progression.

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.

A rare case of intervertebral disc calcification combined with ossification of the posterior longitudinal ligament in a child: a case report and literature review

BACKGROUND

Intervertebral disc calcification (IDC) combined with calcification in children has been sporadically reported, while ossification of the posterior longitudinal ligament (OPLL) in the cervical spine in pediatric patients is exceedingly rare. The aim of this study is to investigate the potential prognosis and outcomes associated with this condition.

CASE PRESENTATION

We present an unusual case involving a 10-year-old Chinese child diagnosed with calcified cervical disc herniation and ossification of the posterior longitudinal ligament. Conservative treatment measures were implemented, and at the 1-month and 6-month follow-up, the patient's pain exhibited significant improvement. Subsequent cervical MRI and CT scans revealed the complete disappearance of OPLL and substantial absorption of the calcified disc. During the three-month follow-up, CT demonstrated slight residual disc calcification, however, the patient remained asymptomatic with no discernible limitation in cervical motion.

CONCLUSIONS

We conducted a comprehensive review of several cases presenting with the same diagnosis. It is noteworthy that IDC combined with OPLL in children constitutes a rare clinical entity. Despite imaging indications of potential spinal canal occupation, the majority of such cases demonstrate complete absorption following conservative treatment, with OPLL exhibiting a faster absorption rate than calcified discs.

ANGPTL4 binds to the leptin receptor to regulate ectopic bone formation

Leptin protein was thought to be unique to leptin receptor (LepR), but the phenotypes of mice with mutation in LepR [db/db (diabetes)] and leptin [ob/ob (obese)] are not identical, and the cause remains unclear. Here, we show that db/db, but not ob/ob, mice had defect in tenotomy-induced heterotopic ossification (HO), implicating alternative ligand(s) for LepR might be involved. Ligand screening revealed that ANGPTL4 (angiopoietin-like protein 4), a stress and fasting-induced factor, was elicited from brown adipose tissue after tenotomy, bound to LepR on PRRX1+ mesenchymal cells at the HO site, thus promotes chondrogenesis and HO development. Disruption of LepR in PRRX1+ cells, or lineage ablation of LepR+ cells, or deletion of ANGPTL4 impeded chondrogenesis and HO in mice. Together, these findings identify ANGPTL4 as a ligand for LepR to regulate the formation of acquired HO.

A single centre service evaluation of degenerative cervical and thoracic myelopathy

BACKGROUND

Degenerative cervical myelopathy (DCM) and degenerative thoracic myelopathy (DTM) present with leg, bladder and bowel symptoms. If imaging confirms spinal cord compression both conditions are usually managed surgically. Surgical timing is important in patient management as it affects post-operative recovery and long-term outcomes. This service evaluation aims to explore whether that patients with DTM are more likely to be treated urgently than those with DCM and to examine whether any differences in management are justified.

METHODS

A retrospective service evaluation was registered and approved by the Cambridge University Hospitals NHS Foundation Trust (CUH) Clinical Audit Department (Clinical Project ID4455 PRN10455). All patients who had undergone surgery for DTM at CUH from January 2015 until April 2022 were included. Comparison was made to a cohort of DCM patients who underwent surgery at CUH from June 2016 to January 2019. Data analysis was conducted in R.

RESULTS

A total of 130 DCM patients and 78 DTM patients were included. Our DCM and DTM patient cohorts had comparable demographics, but DTM patients had fewer spinal levels affected. Despite equivalent disease severity, DTM patients had a shorter time to diagnosis, shorter wait for surgery and were more likely to be operated on as an emergency case.

CONCLUSIONS

Despite comparable demographics and pathophysiology, DTM was diagnosed and managed more quickly than DCM. Better defined diagnostic pathways for degenerative spinal myelopathy may hold opportunities to optimise diagnosis and management, ensuring consistent high quality, efficient and equitable care.

Comparative Study of the Cytokine Profiles of Serum and Tissues from Patients with the Ossification of the Posterior Longitudinal Ligament

BACKGROUND

The ossification of the posterior longitudinal ligament (OPLL) is one of the contributing factors leading to severe cervical spondylotic myelopathy (CSM). The mechanism causing ossification is still unclear. The current study was designed to analyze the specimens of patients with or without OPLL.

METHODS

The study collected 51 patients with cervical spondylosis. There were six serum samples in both the non-OPLL (NOPLL) and OPLL groups. For tissue analysis, there were seven samples in the NOPLL group and five samples in the OPLL group. The specimens of serum and tissue were analyzed by using Human Cytokine Antibody Arrays to differentiate biomarkers between the OPLL and NOPLL groups, as well as between serum and OPLL tissue. Immunohistochemical staining of the ligament tissue was undertaken for both groups.

RESULTS

For OPLL vs. NOPLL, the serum leptin levels are higher in the OPLL group, corroborating others' observations that it may serve as a disease marker. In the tissue, angiogenin (ANG), osteopontin (OPN), and osteopro-tegerin (OPG) are higher than they are in the OPLL group (p < 0.05). For serum vs. OPLL tissue, many chemotactic cytokines demonstrated elevated levels of MIP1 delta, MCP-1, and RANTES in the serum, while many cytokines promoting or regulating bone genesis were up-regulated in tissue (oncostatin M, FGF-9, LIF, osteopontin, osteoprotegerin, TGF-beta2), as well as the factor that inhibits osteoclastogenesis (IL-10), with very few cytokines responsible for osteoclastogenesis. Molecules promoting angiogenesis, including angiotensin, vEGF, and osteoprotegerin, are abundant in the OPLL tissue, which paves the way for robust bone growth.

To infer the probability of cervical ossification of the posterior longitudinal ligament and explore its impact on cervical surgery

The ossification of the posterior longitudinal ligament (OPLL) in the cervical spine is commonly observed in degenerative changes of the cervical spine. Early detection of cervical OPLL and prevention of postoperative complications are of utmost importance. We gathered data from 775 patients who underwent cervical spine surgery at the First Affiliated Hospital of Guangxi Medical University, collecting a total of 84 variables. Among these patients, 144 had cervical OPLL, while 631 did not. They were randomly divided into a training cohort and a validation cohort. Multiple machine learning (ML) methods were employed to screen the variables and ultimately develop a diagnostic model. Subsequently, we compared the postoperative outcomes of patients with positive and negative cervical OPLL. Initially, we compared the advantages and disadvantages of various ML methods. Seven variables, namely Age, Gender, OPLL, AST, UA, BMI, and CHD, exhibited significant differences and were used to construct a diagnostic nomogram model. The area under the curve (AUC) values of this model in the training and validation groups were 0.76 and 0.728, respectively. Our findings revealed that 69.2% of patients who underwent cervical OPLL surgery eventually required elective anterior surgery, in contrast to 86.8% of patients who did not have cervical OPLL. Patients with cervical OPLL had significantly longer operation times and higher postoperative drainage volumes compared to those without cervical OPLL. Interestingly, preoperative cervical OPLL patients demonstrated significant increases in mean UA, age, and BMI. Furthermore, 27.1% of patients with cervical anterior longitudinal ligament ossification (OALL) also exhibited cervical OPLL, whereas this occurrence was only observed in 6.9% of patients without cervical OALL. We developed a diagnostic model for cervical OPLL using the ML method. Our findings indicate that patients with cervical OPLL are more likely to undergo posterior cervical surgery, and they exhibit elevated UA levels, higher BMI, and increased age. The prevalence of cervical anterior longitudinal ligament ossification was also significantly higher among patients with cervical OPLL.

Diffuse Idiopathic Skeletal Hyperostosis (DISH): New evidence from micro-XCT scanning

OBJECTIVE

To observe and describe the development and underlying structure of the spinal manifestations of individuals osteologically diagnosed with DISH (Diffuse Idiopathic Skeletal Hyperostosis), using micro-XCT imaging.

MATERIALS

A total of 72 individuals with DISH were identified in two modern skeletal collections in South Africa.

METHODS

Vertebral columns affected by DISH were scanned at the micro-focus x-ray computed tomography facility at the Nuclear Energy Corporation of South Africa. Four features were macroscopically examined: (1) the origin of the new bone growth; (2) retention of the original vertebral cortex at the site of the new bone formation associated with DISH; (3) evidence of trabecular bone with or without sclerosis on the anterolateral surface of affected vertebrae; and (4) abnormal areas of osteosclerosis beyond features associated with DISH.

RESULTS

Considerable variation across and between the four recorded features was found. Of note, 81% (n = 58) of individuals had both developed trabecular bone within the flowing new bone formation (feature 3), without retention of the original vertebral cortex (feature 2).

CONCLUSIONS

Possible localised erosive/inflammatory processes destroyed the original cortex of the vertebral body and resulted in the expansion of trabeculae with new bone formation.

SIGNIFICANCE

Micro-XCT imaging shed new light on the development of DISH, adding to literature suggesting that it could be an inflammatory disease.

LIMITATIONS

Clinical histories of the individuals were not known.

SUGGESTIONS FOR FURTHER RESEARCH

The role of chronic inflammatory disease in the development of DISH should be further explored including both the extra-spinal and spinal manifestations.

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.

Evidence for a genetic contribution to the ossification of spinal ligaments in Ossification of Posterior Longitudinal Ligament and Diffuse idiopathic skeletal hyperostosis: A narrative review

Diffuse Idiopathic Skeletal Hyperostosis (DISH) and Ossification of the Posterior Longitudinal Ligament (OPLL) are common disorders characterized by the ossification of spinal ligaments. The cause for this ossification is currently unknown but a genetic contribution has been hypothesized. Over the last decade, many studies on the genetics of ectopic calcification disorders have been performed, mainly on OPLL. Most of these studies were based on linkage analysis and case control association studies. Animal models have provided some clues but so far, the involvement of the identified genes has not been confirmed in human cases. In the last few years, many common variants in several genes have been associated with OPLL. However, these associations have not been at definitive levels of significance and evidence of functional significance is generally modest. The current evidence suggests a multifactorial aetiopathogenesis for DISH and OPLL with a subset of cases showing a stronger genetic component.

K-line in patients with cervical ossification of the posterior longitudinal ligament: relationship with change in sagittal cervical curvature and laminoplasty outcomes

INTRODUCTION

To analyze how K-line is related to change in sagittal cervical curvature and laminoplasty outcomes in patients with cervical ossification of the posterior longitudinal ligament (OPLL).

MATERIALS AND METHODS

The study retrospectively analyzed 81 patients with OPLL who had undergone posterior cervical single-door laminoplasty and arch plate fixation between June 2011 and June 2017. Fifty-five were K-line positive (K[+]) and 26 were K-line negative (K[-]). Clinical and radiological results were compared between the groups. Patients were followed up for at least 2 years.

RESULTS

Before the operation, Japanese Orthopedic Association (JOA) score, visual analogue scale (VAS) score, neck disability index (NDI), and short-form-36 (SF-36) quality of life score did not differ significantly between the groups. Neurological function was improved in both groups after the procedure. At last follow-up, JOA score, VAS score, NDI, SF-36 score, and JOA score improvement rate differed significantly between the groups. Before the operation, at the 3-month and final follow-ups, C2-7 Cobb angle, T1 slope, and C2-7 SVA differed significantly between the groups. The changes were more marked in the K(-) group than in the K(+) group. The incidence of cervical kyphosis differed significantly between the groups (P < 0.05), as well as between patients with lordosis < 7° and those with lordosis ≥ 7°.

CONCLUSIONS

K-line negativity and lordosis < 7° may predict kyphosis after laminoplasty in patients with OPLL. The cervical curvature in patients with OPLL tends towards kyphosis and anteversion after laminoplasty, which contributes to the reduced clinical effect of the procedure.

High Body Mass Index Is Associated with an Increased Risk of the Onset and Severity of Ossification of Spinal Ligaments

Background

Ossification of the posterior longitudinal ligament (OPLL) and that of ligamentum flavum (OLF) are the main types of the ossification of spinal ligaments (OSL) that cause the thoracic myelopathy. Although several studies have investigated the relationship of body mass index (BMI) with the onset or severity of OSL, it remains unverified due to the contradictory results of existing evidence. A systematic review and meta-analysis were performed in this work to determine the relationship of BMI with the onset and severity of OSL.

Methods

PubMed, EMBASE, Web of Science, and Cochrane Library were comprehensively searched online for relevant studies focusing on the relationship of BMI with the onset or severity of the OSL. The difference in BMI of OSL (or severe OSL group) and non-OSL (or nonsevere OSL group) groups was evaluated using the mean difference (MD) with a corresponding 95% confidence interval (CI).

Results

Fifteen studies were included in this systematic review and meta-analysis. The BMI of the OSL group was significantly higher than that of the non-OSL group (MD = 1.70 kg/m², 95% CI = 1.02–2.39 kg/m², and P < 0.01). Similar results were observed in the subgroup analysis of female (P < 0.01), OPLL (P < 0.01), and OLF (P < 0.01) populations. Three studies reported a significant association of BMI with the ossification index of OSL and the standardized regression coefficient ranging from 0.11 to 0.43 (P < 0.05). Moreover, a significantly higher BMI was observed in the severe OSL group compared with that in the nonsevere OSL group (MD = 3.09, 95% CI, 0.22–5.97 kg/m², and P = 0.04).

Conclusion

The significant association of high BMI with the onset and severity of OSL may provide new evidence and insights into the mechanism research and management of OSL.

Clinical Characteristics of Patients with Ossification of the Posterior Longitudinal Ligament and a High OP Index: A Multicenter Cross-Sectional Study (JOSL Study)

Background: The purpose of this study was to clarify the clinical features of ossification of the posterior longitudinal ligament (OPLL) and extreme ossification at multiple sites. Methods: This prospective study involved patients with a diagnosis of cervical OPLL at 16 institutions in Japan. Patient-reported outcome measures, including responses on the Japanese Orthopaedic Association (JOA) Cervical Myelopathy Evaluation Questionnaire (JOA-CMEQ), JOA Back Pain Evaluation Questionnaire (JOA-BPEQ), and visual analog scale pain score, were collected to investigate clinical status. In each patient, the sum of the levels at which OPLL was located (OP index) was evaluated on whole-spine computed tomography, along with ossification of other spinal ligaments including the anterior longitudinal ligament (OALL), ligament flavum (OLF), supra- and intraspinous ligaments (SSL), and diffuse idiopathic skeletal hyperostosis (DISH). The distribution of OP index values in the study population was investigated, and the clinical and radiologic characteristics of patients in the top 10% were assessed. Results: In total, 236 patients (163 male, 73 female; mean age 63.5 years) were enrolled. Twenty-five patients with OP index ≥ 17 were categorized into a high OP index group and the remainder into a moderate/low OP index group. There were significantly more women in the high OP index group. Patients in the high OP index group also had significantly poorer scores for lower extremity function and quality of life on the JOA-CMEQ and in each domain but not for body pain on the JOA-BPEQ compared with those in the moderate/low OP index group. Patients in the high OP index group had more OALL in the cervical spine and more OLF and SSL in the thoracic spine. The prevalence of DISH was also significantly higher in the high OP index group. In the high OP index group, interestingly, OPLL was likely to be present adjacent to DISH in the cervicothoracic and thoracolumbar spine, especially in men, and often coexisted with DISH in the thoracic spine in women. Conclusion: This prospective cohort registry study is the first to demonstrate the clinical and radiologic features of patients with OPLL and a high OP index. In this study, patients with a high OP index had poorer physical function in the lumbar spine and lower extremities and were also predisposed to extreme ossification of spinal ligaments other than the OPLL.

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.

Cervical Ossification of the Posterior Longitudinal Ligament (OPLL) in Native Hawaiians and/or Polynesians: A 3-year Retrospective Demographic and Descriptive Pilot Study

Ossification of the posterior longitudinal ligament (OPLL) is a disease characterized by the replacement of the posterior longitudinal ligament with ectopic bone and cartilage. Historically, the disease was described as highly prevalent in Japanese and other Asian populations. However, recent studies suggest OPLL may have a higher prevalence in non-Asian communities than previously believed. To date, there are no demographic or epidemiologic studies examining OPLL in Native Hawaiian or Polynesian communities. The purpose of this study was to review the demographics and comorbidities of a cohort of patients with OPLL from the author's institution, designated as either Native Hawaiian and/or Polynesian (NHP) or Non-Native Hawaiian and/or Polynesian (NNHP). Demographic findings from this study were similar to previous literature demonstrating higher rates of OPLL in men and older patients with an average age of 56 years in the NHP group and 65 years in the NNHP group. There were no statistically significant differences in the rates of type II diabetes mellitus, coronary vascular disease, chronic kidney disease, or hypertension between NHP and NNHP groups. The NHP group exhibited statistically higher rates of obesity when compared to the NNHP group. Obesity's risk in the development or progression of OPLL in the NHP population has not been examined and requires additional investigation. This study serves as a beginning for further demographic and epidemiologic investigations into OPLL in Native Hawaiian and Polynesian communities to facilitate improved identification of those at risk and guide diagnosis and treatment of these patients.

Severity of Myelopathy is Closely Associated With Advanced Age and Signal Intensity Change in Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective Nationwide Investigation

STUDY DESIGN

Prospective, nationwide case series.

OBJECTIVE

To identify preoperative factors associated with myelopathy and neurological impairment in patients with cervical ossification of the posterior longitudinal ligament (OPLL).

SUMMARY OF BACKGROUND DATA

Various studies have reported clinical outcomes following the surgical treatment of OPLL. However, there has been no large-scale study of preoperative clinical features in patients with cervical OPLL.

MATERIALS AND METHODS

Data were prospectively collected from 28 institutions nationwide in Japan. In total, 512 patients with neurological impairment caused by cervical OPLL requiring surgery were enrolled. Basic demographic and clinical data, including age, sex, diabetes status, body mass index, smoking history, and disease duration were collected. C2-7 lordotic angle, canal narrowing ratio, range of motion in flexion-extension at C2-7, and type of OPLL were evaluated on lateral radiographs to identify factors influencing the clinical features of patients with OPLL in whom surgery was planned.

RESULTS

Complete documentation was available for 490 patients (362 male, 128 female). In total, 34 patients had the localized type, 181 had the segmental type, 64 had the continuous type, and 211 had the mixed type. Although there were no significant differences in age, body mass index, disease duration, Japanese Orthopedic Association (JOA) score, and lordotic angle at C2-7 according to the type of OPLL, significant differences were observed in a range of motion at C2-7 and the canal narrowing ratio among the 4 types. Multiple regression analysis revealed that the JOA score was significantly associated with age and signal intensity change on magnetic resonance imaging.

CONCLUSIONS

This is the first large-scale, prospective, multicenter case series study to investigate factors influencing preoperative neurological status in patients with OPLL. Age and signal intensity change on magnetic resonance images were significantly associated with JOA score in patients requiring surgery.

LEVEL OF EVIDENCE

Level II.

Serum Periostin Level Reflects Progression of Ossification of the Posterior Longitudinal Ligament

Background:

Ossification of the posterior longitudinal ligament (OPLL), characterized by ectopic new bone formation in the spinal ligament, causes neurological impairment due to narrowing of the spinal canal. However, the etiology has not been fully elucidated yet. Several biomarkers may be related to the pathogenesis of OPLL. The present study focused on the serum level of periostin, which is recognized as an important bone formation regulator.

Methods:

This study included 92 patients with OPLL and 54 control patients without OPLL. For the case-control analysis, 54 age and sex-matched patients were randomly included in the OPLL group. The serum fibroblast growth factor-23 (FGF-23), creatinine, inorganic phosphate, calcium, alkaline phosphatase, and periostin levels were assessed. Furthermore, the calcium, creatinine, and inorganic phosphate levels in urine and the percentage of tubular reabsorption of phosphate were also analyzed. Moreover, the relationship between the biomarkers and the extent of OPLL was analyzed. The data were compared between patients with OPLL progression (the progression group) and without OPLL progression (the non-progression group).

Results:

The mean serum FGF-23 and periostin levels in the OPLL group were higher than that in the control group. The serum inorganic phosphate level in the OPLL group was lower than that in the control group. No correlation was found between any of the biomarkers and the extent of ossification. The serum periostin level in the progression group was higher than that in the non-progression group. No significant difference in the serum FGF-23 level was noted between the progression and non-progression groups. Moreover, no correlation was found between serum periostin and FGF-23 levels.

Conclusions:

The serum periostin level is related to OPLL progression.

Level of Evidence:

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Close association between non-alcoholic fatty liver disease and ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament (OPLL) of the spine is a disease of unknown etiology occurring frequently in individuals with metabolic disturbances. Obesity has been suggested as a potential risk factor for the severity of OPLL. We aimed to investigate whether non-alcoholic fatty liver disease (NAFLD) is associated with OPLL severity. We assessed the severity of NAFLD by a liver-to-spleen (L/S) ratio on computed tomography (CT) scans of 85 symptomatic OPLL patients at a single institution in Japan. We also assessed the severity of OPLL by CT reconstruction sagittal and axial images. The prevalence of NAFLD in middle-aged patients (age < 70 years, n = 50) was 80.3%, which was 2.5-8 times higher than that in the general Japanese population (9-30%). The ossification index of the spinal ligaments increased in proportion to the severity of fatty liver. The L/S ratio was revealed as a significant risk factor associated with the total ossification index (standardized β: -0.40, 95% confidence interval - 54.34 to - 4.22). This study suggests the potential contribution of NAFLD to the progression of OPLL. The close association between NAFLD and OPLL demonstrated in this study warrants further study to elucidate the causal nature of this relationship.

Potential Link between Ossification of Nuchal Ligament and the Risk of Cervical Ossification of Posterior Longitudinal Ligament: Evidence and Clinical Implication from a Meta-Analysis of 8429 Participants

OBJECTIVE

The aim of the present paper was to evaluate the strength and the magnitude of the association between ossification of the nuchal ligament (ONL) and the risk of cervical ossification of the posterior longitudinal ligament (COPLL) and to determine whether there is a direct association or whether COPLL is a consequence of shared risk factors.

METHODS

Medline, Web of Science, Cochrane Library, and Embase databases were searched for studies evaluating the association of COPLL-ONL published before July 2020. Eligible studies were selected based on certain inclusion and exclusion criteria. Two investigators independently conducted the quality assessment and extracted the data, including study designs, countries, patients' age, gender, body mass index (BMI), and the risk of COPLL between individuals with and without ONL. A meta-analysis of homogenous data, a sensitivity analysis, a publication bias assessment, and a subgroup analysis were performed using Stata 12.0 software.

RESULTS

A total of 10 cohort studies involving 8429 participants were incorporated into this analysis. Pooled results demonstrated a statistically significant association between the presence of ONL and the increased COPLL risk (odds ratio [OR] 3.84; 95% confidence interval [CI] 2.68-5.52, P < 0.001). Furthermore, subgroup analyses indicated that this association was independent of study design (6.36-fold in case-control studies vs 3.22-fold in cross-sectional studies), sex (6.33-fold in male-female ratio >2.5 vs 2.91-fold in male-female ratio <2.5), age (4.28-fold in age ≥55 years vs 3.45-fold in age <55 years), and BMI (3.88-fold in BMI ≥ 25 kg/m² vs 2.43-fold in BMI < 25 kg/m² ), which also indicated that obese, older male patients with ONL had a higher risk of OPLL. Moreover, combined two articles revealed that patients with larger-type ONL had a significantly higher risk of long-segment COPLL compared with controls (OR 1.86; 95% CI 1.41-2.47, P < 0.001).

CONCLUSION

This is the first meta-analysis to demonstrate a strong and steady association between ONL and higher risk of COPLL. This association was independent of sex, age, and BMI. Considering that ONL is generally asymptomatic and easily detectable on X-ray, our findings implied that ONL might serve as an early warning sign of the onset of COPLL and provide clinicians an opportunity for early detection and early intervention.

The integrated analysis of circRNAs, miRNAs and mRNAs revealed the potential role in the TGF-β and TNF-α signaling pathways of OPLL

Ossification of the posterior longitudinal ligament (OPLL), one of spinal disease causing myelopathy, is characterized by the ectopic ossification and narrowing of the spinal cord. However, the pathogenesis of OPLL is largely unclear. In this study, transcriptome expression profiles (circRNAs, lncRNAs, and mRNAs) were identified via high-throughput sequencing using peripheral blood mononuclear cells (PBMCs) from OPLL and non-OPLL patients. We found that 1150 mRNAs, 331 circRNAs, and 1429 lncRNAs were significantly differentially expressed in the PBMCs of OPLL patients. GO and KEGG enrichment analyses revealed that most mRNAs were associated with inflammation. The co-expression networks indicated that circRNAs and lncRNAs could regulate the mRNAs through influencing the inflammation of OPLL. The circRNA-miRNA-mRNA integrated network showed that circRNA-regulated mRNAs associated with TGF-β and TNF-α signaling pathways. These analyses indicate that circRNAs, lncRNAs, and mRNAs from PBMCs might contribute to inflammation in OPLL.

Is There a Relationship Between Bony Fusion After Anterior Cervical Discectomy and Fusion and Heterotopic Ossification After Cervical Disc Arthroplasty in Hybrid Surgery?

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

The aim of this study was to investigate the relationship between bony fusion after anterior cervical discectomy and fusion (ACDF) and heterotopic ossification (HO) after cervical disc arthroplasty (CDA) in hybrid surgery (HS).

SUMMARY OF BACKGROUND DATA

The mechanism of postoperative bone formation still remains unknown. It is considered a risk factor in CDA but is essential for a solid union in ACDF. With HS, we could directly study the mechanism and relationship of different forms of postoperative bone formation.

METHODS

Clinical data of 91 patients who had undergone consecutive two-level HS between January 2011 and January 2018 and with a minimum of 2-year follow-up was analyzed. HO was assessed based on McAfee's classifications, whereas fusion success was evaluated according the Food and Drug Administration approved criteria. Clinical outcomes and radiographic parameters were collected and used for the relevant comparisons.

RESULTS

HO was identified in 48.4% of patients (44/91). The fusion rates of patients in the HO group and the non-HO group at 3, 6, and 12 months postoperatively, and the final follow-up were 81.8% and 19.1%, 95.4% and 74.5%, 95.4% and 85.1%, and 97.7% and 93.6%, respectively. The fusion rates were significantly higher at 3 and 6 months after operation in the HO group than in the non-HO group (P < 0.05). Patients in both groups had significant improvements across all clinical outcomes at final follow-up.

CONCLUSION

There was a significant relationship between bony fusion and occurrence of HO after HS, suggesting that both bony fusion and HO are reflections of individual osteogenic capacity. However, a reliable predictor of postoperative bone formation is needed in the future to guarantee a solid bony fusion after ACDF and to further take full advantage of the motion-preserving from CDA.

LEVEL OF EVIDENCE

3.

The characteristics of the patients with radiologically severe cervical ossification of the posterior longitudinal ligament of the spine: A CT-based multicenter cross-sectional study

BACKGROUND

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by heterotopic bone formation in the posterior longitudinal ligament of the spine. We know that the size and distribution of the ossified lesions in patients with OPLL are different in each case. However, the characteristics of the patients with radiologically severe cervical OPLL remain unknown.

METHODS

The participants of our study were symptomatic patients with cervical OPLL who were diagnosed by standard radiographs of the cervical spine. Whole-spine CT data and demographic data such as age and sex were obtained from 20 institutions belonging to the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament. According to the number of the levels involved by OPLL, we stratified the patients into two subgroups: severe group (S-group) and non-severe group (NS-group) to delineate the characteristics of radiologically severe patients with cervical OPLL. We also evaluated the most compressed level and the degree of occupying ratio of cervical spinal canal by OPLL at the most compressed level.

RESULTS

A total of 234 patients with a mean age of 65 years were recruited. The S-group consisted of 48 patients (21%, 12 females and 36 males) and the NS-group consisted of 92 patients (79%, 22 females and 70 males). The mean age of males in the S-group (68 years old) was significantly higher than that of males in the NS-group (64 years old); however there was no significant difference in the mean age in females between the S-group (69 years old) and the NS-group (66 years old). No significant difference of body mass index, ossification of the nuchal ligament-positivity and presence of diabetes mellitus were found between the S- and the NS-group.

CONCLUSIONS

It is likely that the manner of extension of cervical OPLL is different between male and female patients.

The roles of autophagy in osteogenic differentiation in rat ligamentum fibroblasts: Evidence and possible implications

Autophagy, a macromolecular degradation process, plays a pivotal role in cell differentiation and survival. This study was designed to investigate the role of autophagy in the osteogenic differentiation in ligamentum fibroblasts. Rat ligamentum fibroblasts were isolated from the posterior longitudinal ligament and cultured in osteogenic induction medium. Ultrastructural analysis, immunofluorescence assay, western blot, flow cytometry, and lysosomal activity assessment were performed to determine the presence and activity of autophagy in the cells. The mineralization deposit and osteogenic gene expressions were evaluated to classify the association between autophagy activity and the bone formation ability of the spinal ligament cells. The influence of leptin and endothelin-1 on the autophagy activity was also evaluated. Our study demonstrated that autophagy was present and increased in the ligament cells under osteogenic induction. Inhibition of autophagy with either pharmacologic inhibitors (Bafilomycin A and 3-methyladenine) or Belcin1 (BECN1) knocking down weakened the mineralization capacity, decreased the gene expressions of COL1A1, osteocalcin (Ocn), and runt-related transcription factor 2 (Runx2) in the ligamentum fibroblasts and increased cell apoptosis. The Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-BECN1 autophagic pathway was activated in the osteogenic differentiating ligamentum fibroblasts. Leptin significantly increased the autophagy activity in the ligament cells under osteogenic induction. These discoveries might improve our understanding for the mechanism of ossification of the posterior longitudinal ligament (OPLL) and provide new approaches on the prevention and treatment of this not uncommon disease.

Trabecular bone score and bone turnover markers in men with DISH: Data from the Camargo Cohort study

OBJECTIVE

Diffuse idiopathic skeletal hyperostosis (DISH) has been associated with an increased risk of vertebral fracture. To date, no studies have investigated the relationship between DISH and bone microstructure assessed by the trabecular bone score (TBS).

METHODS

Cross-sectional study, nested in a prospective population-based cohort. All men (968) aged≥50 years were included. Clinical covariates, DISH, TBS, serum bone turnover markers and bone mineral density (BMD) were analyzed.

RESULTS

Mean age of participants was 65 ± 9 years. 207 (21.6%) had DISH. DISH subjects were older, had higher body mass index (BMI) and abdominal perimeter, lower glomerular filtration rate (GFR), and higher prevalence of metabolic syndrome (MetS) than non-DISH (NDISH) subjects. Bone mineral density at the lumbar spine (LS-BMD) was significantly higher in the DISH group. TBS values were 1.317 [1.303-1.331] for DISH and 1.334 [1.327-1.341] for NDISH subjects, after adjusting by age, BMI, abdominal perimeter, arterial hypertension, diabetes mellitus, MetS, GFR, serum alkaline phosphatase (ALP), LS and femoral neck BMD (p = 0.03). Serum ALP levels were higher in DISH subjects, showing an inverse correlation with TBS that remained significant after adjusting by age and BMI.

CONCLUSIONS

TBS values were significantly lower in men with DISH irrespective of age, BMI and BMD, suggesting that the presence of DISH might be related to a worse trabecular microstructure.

Biomarkers of Ossification of the Spinal Ligament

STUDY DESIGN

Literature review.

OBJECTIVES

To review biomarkers in patients with ossification of the spinal ligament (OSL), including ossification of the posterior longitudinal ligament and ossification of the ligamentum flavum and to raise the present issues.

METHODS

A literature search was performed using PubMed and MEDLINE databases. The biomarkers were classified according to category. The number of the subjects and reproducibility were assessed.

RESULTS

Eleven articles were included in this review. There were 9 articles from Japan, 1 article from Taiwan, and 1 article from China. The biomarkers were classified into calcium-phosphate metabolism markers, bone turnover markers, sclerostin, dickkopf-1, secreted frizzled-related protein-1, fibroblast growth factor-23, fibronectin, menatetrenone, leptin, pentosidine, and hypersensitive C-reactive protein. However, there were several limitations in the research studies, such as small research field, small number of subjects, and a lack of reproducibility.

CONCLUSIONS

Although there have been several studies that have analyzed biomarkers for OSL, there are no definitive conclusions to date. Numerous issues will need to be resolved in the future. It is imperative to continue this research because the results might prove beneficial to elucidate the pathology of OSL and the measures to prevent the initiation and progression of the disease.

Molecular Pathophysiology of Ossification of the Posterior Longitudinal Ligament (OPLL)

Ossification of the posterior longitudinal ligament (OPLL) can be defined as an ectopic ossification in the tissues of spinal ligament showing a hyperostotic condition. OPLL is developed mostly in the cervical spine and clinical presentations of OPLL are majorly myelopathy and/or radiculopathy, with serious neurological pathology resulting in paralysis of extremities and disturbances of motility lowering the quality of life. OPLL is known to be an idiopathic and multifactorial disease, which genetic factors and non-genetic factors including diet, obesity, physical strain on the posterior longitudinal ligament, age, and diabetes mellitus, are involved into the pathogenesis. Up to now, surgical management by decompressing the spinal cord is regarded as standard treatment for OPLL, although there might be the risk of development of reprogression of ossification. The molecular pathogenesis and efficient therapeutic strategy, especially pharmacotherapy and/or preventive intervention, of OPLL has not been clearly elucidated and suggested. Therefore, in this review, we tried to give an overview to the present research results on OPLL, in order to shed light on the potential pharmacotherapy based on molecular pathophysiologic aspect of OPLL, especially on the genetic/genomic factors involved into the etiology of OPLL.

MicroRNA-10a, -210, and -563 as circulating biomarkers for ossification of the posterior longitudinal ligament

BACKGROUND CONTEXT

The presence of ossification of posterior longitudinal ligament (OPLL) can lead to symptomatic spinal cord compression and myelopathy. The surgical approach in patients with myelopathy is influenced by the presence of OPLL. Diagnose of OPLL currently requires computed tomography which incurs a large dose of radiation. Circulating disease-specific microRNAs (miRNAs) may serve as promising diagnostic markers with no radiation and easy accessibility for OPLL patients.

PURPOSE

The purpose of this study is to evaluate the accuracy and significance of OPLL-specific microRNAs in discriminating OPLL from normal and intervertebral disc degenerated (IDD) patients by detecting the microRNAs' plasma level.

STUDY DESIGN/PATIENT SAMPLES

The level of microRNAs in OPLL patients' plasma or serum were detected and compared to that of normal and IDD patients to evaluate the accuracy and significance of diagnosing OPLL.

METHODS

Taking advantage of the high through-put microRNA sequencing data, we selectively tested the ten most differentially regulated microRNAs in patients with: (1) radiologically diagnosed OPLL (n = 68), (2) radiologically diagnosed disc herniated patients with no evidence of OPLL (n = 45), (3) non-OPLL and nonmyelopathy patients (n = 53).The feasibility of the biomarkers in identifying OPLL was assessed through analysis of sensitivity, specificity, accuracy, negative predictive value, positive predictive value, and area under the curve (AUC) values.

RESULTS

Of the ten miRNAs validated, miR-10a-3p, miR-10a-5p, miR-563, miR-210-3p, and miR-218-3p showed significance between OPLL and non-OPLL blood samples. While miR-10a-5p, miR-563, and miR-210-3p showed high accuracy and significance in identifying OPLL from other groups individually, and an index that combines these miRNAs achieved the highest accuracy and AUC among these individual miRNAs.

CONCLUSIONS

Analysis of miR-10a-5p, miR-563, and miR-210-3p may be of important value in diagnosing OPLL. These markers maybe useful in a clinical setting in the early detection of OPLL patients by blood testing.

Metabolite profiling of plasma in patients with ossification of the posterior longitudinal ligament

BACKGROUND

Metabolomics is one of the "omics" technologies, and is a comprehensive analysis of small molecule metabolites which include amino acid, nucleotides, carbohydrates and fatty acid. The purpose of the present study was to compare the differences of metabolite profiling between patients with ossification of the posterior longitudinal ligament (OPLL) and control subjects.

METHODS

We analyzed plasma metabolites in patients with cervical OPLL (n = 10) and in control subjects (n = 10). Ionic metabolites were analyzed using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) and lipophilic metabolites were analyzed using liquid chromatograph time-of-flight mass spectrometry (LC-TOFMS).

RESULTS

A total of 259 metabolites (144 metabolites in CE-TOFMS and 115 metabolites in LC-TOFMS) were detected. Among the 259 metabolites, six metabolites, namely acylcarnitine (AC) (14:0), palmitoylcarnitine, AC (18:2), fatty acid (FA) (24:2), thyroxine, thiaproline were significantly larger in OPLL group, even in analyzes excluding patients with diabetes mellitus and hyperlipidemia.

CONCLUSIONS

We examined the metabolite profiling in patients with OPLL for the first time and detected six metabolites showing suggestive association with disease. These results of the present study could lead to new insights into clarifying the molecular pathomechanisms of OPLL.

Two-Staged Circumferential Decompression and Fusion Surgery for Upper Thoracic Myelopathy Caused by Concurrent Beak-Type Ossification of the Posterior Longitudinal Ligament and Ligamentum Flavum at T1-T2 Level: A Case Report

BACKGROUND

Upper thoracic myelopathy caused by combined ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) is relatively rare. This clinical condition is difficult to treat, and a surgical method has not been fully established. We report an extremely rare case of severe thoracic myelopathy caused by concurrent beak-type OPLL and OLF at T1-T2.

CASE DESCRIPTION

A 53-year-old woman with paresthesia of both legs and an inability to hold a standing position presented to our hospital. Radiological images showed a large beak-type OPLL at T1-T2 and an OLF at T1-T7. The spinal cord was severely compressed at T1-T2. First, posterior decompression and instrumentation fusion at C6-T4 was performed, with a T1-T2 bilateral parallel gutter along the dural tube into the vertebral bodies covering the extent of the OPLL. Second, anterior decompression of the OPLL with corpectomy of T1-T2 and fusion using iliac bone grafting was performed after the sternal manubrium splitting approach. In the deep operating field of the second surgery, the gutters created during the first surgery were helpful for judging the width and thickness of the OPLL during the anterior decompression procedure. Postoperatively, her neurological symptoms greatly improved, the patient could walk independently, and the Japanese Orthopaedic Association score had improved from 3 preoperatively to 8 at the final follow-up examination at 16 months postoperatively.

CONCLUSIONS

Two-stage circumferential decompression and fusion surgery can be considered an effective surgical method for upper thoracic concurrent OPLL and OLF. The bilateral gutters created during the first surgery improved the safety and feasibility of this difficult operation.

Roles and mechanisms of leptin in osteogenic stimulation in cervical ossification of the posterior longitudinal ligament

Background

Hyperleptinemia is a common feature of obese people, and leptin, an adipocyte-derived cytokine, is believed to be an important factor in the pathogenesis of cervical ossification of the posterior longitudinal ligament(C-OPLL). So this research was to identify the relation between the serum leptin and bone metabolic markers and how the leptin induced osteogenic effect in C-OPLL.

Methods

Sixty-four samples were selected to determine the concentration of leptin, insulin, and alkaline phosphatase. And the association of leptin with these factors was also examined. We also evaluate the effect of leptin on the development of C-OPLL and further explored the possible underlying mechanism in vitro.

Results

We found that serum leptin concentrations were higher in females than in males. Serum leptin and ALP concentrations were increased significantly in C-OPLL females compared to non-OPLL females. In OPLL subjects, the serum leptin concentration corrected for body mass index correlated negatively with the ALP concentrations. In C-OPLL cells, leptin treatment led to a significant increase in mRNA expressions of ALP and OCN and formation of mineralized nodule. Our experiments reported here that osteogenic effect of leptin in C-OPLL cells could be mediated via ERK1/2, p38 MAPK, and/or JNK signaling pathways.

Conclusions

From this research, we got that leptin treatment led to a significant increase in mRNA expressions of ALP and OCN and formation of mineralized nodule. And the osteogenic effect of leptin in C-OPLL cells could be mediated via ERK1/2, p38 MAPK, and/or JNK signaling pathways.

The Influence of Obesity on Total Elbow Arthroplasty

Total elbow arthroplasty (TEA) has undergone a significant evolution in indications and outcomes in the past decade. Although rheumatoid patients once had the overwhelming number of TEAs, now TEAs for the sequelae of trauma predominate. Furthermore, as obesity has mirrored the increase in the posttraumatic population, TEA complications have increased whereas the durability of implants under these loads has decreased. Solutions are urgently needed to address the complications and revision burden related to posttraumatic deformity and obesity.

Combined use of leptin and mechanical stress has osteogenic effects on ossification of the posterior longitudinal ligament

PURPOSE

To evaluate the effects of leptin/leptin receptor (LepR) combined with mechanical stress on the development of ossification of the posterior longitudinal ligament (OPLL), which is a disease characterized by ectopic bone formation of the posterior longitudinal ligament (PLL) and can lead to radiculopathy and myelopathy.

METHODS

Six human samples of the PLL were analyzed for the expression of leptin and LepR by RT-PCR and western blotting. PLL cells were stimulated with leptin and mechanical stress delivered via a Flexcell tension system, and osteogenic differentiation was evaluated by RT-PCR and western blotting analysis of osteogenic marker expression as well as by alkaline phosphatase (ALP) staining and alizarin red S staining. Activation of mitogen-activated protein kinase (MAPK), Janus kinase (JAK) 2-signal transducer, activator of transcription (STAT) 3 and phosphatidylinositol 3-kinase (PI3K)-Akt was evaluated by western blotting.

RESULTS

Samples from the OPLL group had higher LepR mRNA and protein levels and lower leptin levels than those from healthy controls. Exposure to leptin and Flexcell increased the number of ALP-positive cells and calcium nodules in a dose-dependent manner; this effect was accompanied by upregulation of the osteogenic markers osteocalcin, runt-related transcription factor 2 (RUNX2) and osteopontin. Extracellular signal-regulated kinase, P38 MAPK, JAK2, STAT3, PI3K and Akt signaling, was also activated by the combined effects of leptin and mechanical stress.

CONCLUSIONS

Leptin and LepR are differentially expressed in OPLL tissues, and the combined use of leptin/LepR and mechanical stress promotes osteogenic differentiation of PLL cells via MAPK, JAK2-STAT3 and PI3K/Akt signaling. These slides can be retrieved under Electronic Supplementary Material.

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.

Serum levels of leptin, adiponectin and resistin in patients with ankylosing spondylitis: A systematic review and meta-analysis

OBJECTIVES

Various studies have researched the serum levels of leptin, adiponectin and resistin in patients with ankylosing spondylitis (AS), but the results were inconclusive. The purpose of this study was to systematically evaluate the correlations between serum levels of these adipokines and AS.

METHODS

Electronic databases were retrieved to search relevant publications. Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by the random-effect model. Cochrane Q test and I² statistic were used to test heterogeneity. Subgroup analysis and meta-regression were applied to assess possible sources of heterogeneity.

RESULTS

A total of sixteen articles were included. Meta-analysis results indicated no statistical differences between AS patients and normal controls in serum leptin and adiponectin levels (leptin, SMD=0.829, 95% CI=-0.116 to 1.774, p=0.085; adiponectin, SMD=0.460, 95% CI=-0.004 to 0.924, p=0.052). However, AS patients had higher serum resistin levels than controls (SMD=1.413, 95% CI=0.294 to 2.531, p=0.013). Subgroup analyses suggested that Asian and African AS patients as well as patients aged <40years had higher serum leptin and resistin levels when compared to controls. Serum adiponectin levels were higher in AS patients compared to controls in subgroup of age ≥40, and serum resistin levels in subgroup of BMI ≥25. Measurement method was a source of heterogeneity for resistin. Publication bias was not observed and the robustness of study results was confirmed by sensitivity analysis.

CONCLUSION

Serum resistin, but not leptin or adiponectin levels may be closely associated with the development of AS.

The Pathogenesis of Ossification of the Posterior Longitudinal Ligament

Ossification of the posterior longitudinal ligament (OPLL) is a multi-factorial disease involving an ectopic bone formation of spinal ligaments. It affects 0.8-3.0% aging Asian and 0.1-1.7% aging European Caucasian. The ossified ligament compresses nerve roots in the spinal cord and causes serious neurological problems such as myelopathy and radiculopathy. Research in understanding pathogenesis of OPLL over the past several decades have revealed many genetic and non-genetic factors contributing to the development and progress of OPLL. The characterizations of aberrant signaling of bone morphogenetic protein (BMP) and mitogen-activated protein kinases (MAPK), and the pathological phenotypes of OPLL-derived mesenchymal stem cells (MSCs) have provided new insights on the molecular mechanisms underlying OPLL. This paper reviews the recent progress in understanding the pathophysiology of OPLL and proposes future research directions on OPLL.

Leptin accelerates the pathogenesis of heterotopic ossification in rat tendon tissues via mTORC1 signaling

Leptin, an adipocyte-derived cytokine associated with bone metabolism, is believed to play a critical role in the pathogenesis of heterotopic ossification (HO). The effect and underlying action mechanism of leptin were investigated on osteogenic differentiation of tendon-derived stem cells (TDSCs) in vitro and the HO formation in rat tendons. Isolated rat TDSCs were treated with various concentrations of leptin in the presence or absence of mTORC1 signaling specific inhibitor rapamycin in vitro. A rat model with Achilles tenotomy was employed to evaluate the effect of leptin on HO formation together with or without rapamycin treatment. In vitro studies with TDSCs showed that leptin increased the expression of osteogenic biomarkers (alkaline phosphatase, runt-related transcription factor 2, osterix, osteocalcin) and enhanced mineralization of TDSCs via activating the mTORC1 signal pathway (as indicated by phosphorylation of p70 ribosomal S6 kinase 1 and p70 ribosomal S6). However, mTORC1 signaling blockade with rapamycin treatment suppressed leptin-induced osteogenic differentiation and mineralization. In vivo studies showed that leptin promoted HO formation in the Achilles tendon after tenotomy, and rapamycin treatment blocked leptin-induced HO formation. In conclusion, leptin can promote TDSC osteogenic differentiation and heterotopic bone formation via mTORC1 signaling in both vitro and vivo model, which provides a new potential therapeutic target for HO prevention.

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.

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.

Circulating sclerostin and dickkopf-1 levels in ossification of the posterior longitudinal ligament of the spine

Sclerostin and dickkopf-1(DKK1) are Wnt/β-catenin signal antagonists that play an important role in bone formation. Ossification of the posterior longitudinal ligament (OPLL) of the spine is characterized by pathological ectopic ossification of the posterior longitudinal ligament and ankylosing spinal hyperostosis. The aims of this study were to evaluate serum sclerostin and DKK1 levels in persons with OPLL and to identify its relationship with bone metabolism and bone mass in persons with OPLL. This was a case-control study, and 78 patients with OPLL were compared with 39 age- and sex-matched volunteers without OPLL. We analyzed the relationship with calciotropic hormones, bone turnover markers, OPLL localization, number of ossified vertebrae, and bone mineral density of total hip (TH-BMD). Serum sclerostin levels in men with OPLL were significantly higher than in men in the control group (control group: mean = 45.3 pmol/L; OPLL group: mean = 75.7 pmol/L; P = 0.002). Age and sclerostin levels were positively correlated in men with OPLL (r = 0.43; P = 0.002). Serum sclerostin levels in men with OPLL had a positive correlation with TH-BMD Z-score (r = 0.511; P = 0.011, n = 30). There was a strong negative correlation between serum sclerostin levels and serum DKK1 levels in men with OPLL (r = -0.506; P < 0.001). Bone and mineral metabolism in OPLL differs between men and women. In men with OPLL, systemic secretion of sclerostin increases with advancing age and with higher bone mass. These two Wnt/β-catenin signal antagonists have the opposite effect in persons with OPLL, and higher serum sclerostin levels are counterbalanced by underproduction of DKK1.

Diffuse idiopathic skeletal hyperostosis: Diagnostic, clinical, and paleopathological considerations

Diffuse idiopathic skeletal hyperostosis (DISH) is a disease primarily affecting the spine. However, it is also associated with the ossification/calcification of tendon, ligament, and capsule insertions (entheses) occurring at multiple peripheral sites. The etiology of the condition is unknown, as the name suggests (diffuse idiopathic skeletal hyperostosis), although some correlations with diabetes mellitus, obesity, and age have been noted. Clinical diagnostic criteria have been adapted for paleopathological assessment of archeological skeletal remains, revealing some interesting patterns between monastic and lay populations; showing a higher incidence of DISH among individuals buried in monastic cemeteries. Although fascinating, the mechanisms behind this difference in prevalence are still not fully understood and have been attributed to the relatively richer diets of the monks and priests. The development of diagnostic criteria, where early stage cases of DISH can be identified as well as a better understanding of its causes, is paramount to the prevention of this potentially debilitating condition and perhaps this is where paleopathologists can assist. The use of dry bone rather than living patients for detailed assessment means that paleopathologists are less restricted by the techniques they can use in their investigations and the condition's occurrence in various archeological assemblages can provide interesting insights into its etiology. Clin. Anat. 29:870-877, 2016. © 2016 Wiley Periodicals, Inc.

Roles of leptin in bone metabolism and bone diseases

Adipose tissue has been more accepted as an active contributor to whole body homeostasis, rather than just a fat depot, since leptin, a 16 kDa protein, was discovered as the product of the obese gene in 1994. With more and more studies conducted on this hormone, it has been shown that there is a close relationship between adipose tissue and bone, which have important effects on each other. Bone is the source of many hormones, such as osteocalcin, that can affect energy metabolism and then the anabolism or catabolism of fat tissue. In contrast, the adipose tissue synthesizes and releases a series of adipokines, which are involved in bone metabolism through direct or indirect effects on bone formation and resorption. Interestingly, leptin, one of the most important cytokines derived from fat tissue, seems to account for the largest part of effects on bone, through direct or indirect involvement in bone remodeling and by playing a significant role in many bone diseases, such as osteoporosis, osteoarthritis, rheumatic arthritis, bone tumors and even fractures. In this review, we will discuss the progress in leptin research, particularly focusing on the roles of leptin in bone diseases.

Proteomic profiling of posterior longitudinal ligament of cervical spine

OBJECTIVE

To identify putative biomarkers for ossification of posterior longitudinal ligament (OPLL).

MATERIAL AND METHODS

Proteomic analysis was performed in 4 ligament samples from OPLL patients and healthy controls. RT-PCR was used to further verify the proteomic analysis results.

RESULTS

A total of 50 differentially expressed spots were detected in 2-D electrophoresis between the two groups. In protein/peptide analysis, 21 proteins or peptides were finally identified. Besides 13 hematic proteins and 2 unknown proteins, 6 other proteins were differentially expressed. Among them, carbonic anhydrase I, NAD(P) dependent steroid dehydrogenase-like, billiverdin reductase B and alpha-1 collagen VI were down-regulated, while osteoglycin and nebulin-related anchoring protein were up-regulated. The results of NAD(P) dependent steroid dehydrogenase-like, alpha-1 collagen VI and nebulin-related anchoring protein were validated by RT-PCR.

CONCLUSION

These differentially expressed proteins could play a role in the onset and progression of OPLL.

Metabolic factors in diffuse idiopathic skeletal hyperostosis - a review of clinical data

OBJECTIVES

We aimed to review the literature linking metabolic factors to Diffuse Idiopathic Skeletal Hyperostosis (DISH), in order to assess associations between growth factors and DISH.

METHOD

We identified studies in our personal database and PubMed using the following keywords in various combinations: "diffuse idiopathic skeletal hyperostosis", "ankylosing hyperostosis", "Forestier's disease", "diabetes", "insulin", "obesity", "metabolic", "growth factors", "adipokines", "glucose tolerance" and "chondrocytes".

RESULTS

We were not able to do a systematic review due to variability in methodology of studies. We found positive associations between obesity (especially abdominal obesity), Type 2 diabetes mellitus, glucose intolerance, hyperinsulinemia and DISH.

CONCLUSION

Current research indicates that certain metabolic factors associate with DISH. More precise studies deriving from these findings on these and other newly identified bone-growth factors are needed.

The predisposing factors for the heterotopic ossification after cervical artificial disc replacement

BACKGROUND CONTEXT

Heterotopic ossification (HO) is defined as a formation of bone outside the skeletal system. The reported HO occurrence rate in cervical artificial disc replacement (ADR) is unexpectedly high and is known to vary. However, the predisposing factors for HO in cervical ADR have not yet been elucidated.

PURPOSE

Investigation of the predisposing factors of HO in cervical arthroplasty and the relationship between degeneration of the cervical spine and HO occurrence.

STUDY DESIGN

Retrospective study to discover predisposing factors of HO in cervical arthroplasty.

PATIENT SAMPLE

A total of 170 patients who underwent cervical ADR were enrolled including full follow-up clinical and radiologic data.

OUTCOME MEASURES

Radiologic outcomes were assessed by identification of HOs according to McAfee's classifications.

METHODS

This study enrolled a total of 170 patients who underwent cervical ADR. Pre-existing degenerative change included anterior or posterior osteophytes, ossification of the anterior longitudinal ligament, posterior longitudinal ligament, or ligamentum nuchae. The relationships between basic patient data, pre-existing degenerative change, and HO were investigated using linear logistic regression analysis.

RESULTS

Among all 170 patients, HO was found in 69 patients (40.6%). Among the postulated predisposing factors, only male gender and artificial disc device type were shown to be statistically significant. Unexpectedly, preoperative degenerative changes in the cervical spine exerted no significant influence on the occurrence of HOs. The odds ratio of male gender compared with female gender was 2.117. With regard to device type, the odds ratios of Mobi-C (LDR medical, Troyes, France) and ProDisc-C (Synthes, Inc., West Chester, PA, USA) were 5.262 and 7.449, respectively, compared with the Bryan disc.

CONCLUSIONS

Definite differences in occurrence rate according to the gender of patients and the prosthesis type were identified in this study. Moreover, factors indefinably expected to influence HO in the past were not shown to be risk factors thereof, the results of which may be meaningful to future studies.