Ossification of the Posterior Longitudinal Ligament: An Update on Its Biology, Epidemiology, and Natural History

Spinal hypermobility accelerates ossification in posterior longitudinal ligaments: insights from an in vivo mouse model

Introduction

Ossification of the posterior longitudinal ligaments (OPLL) is characterized by heterotopic ossification in the posterior longitudinal ligament of spine. Our earlier research found that mechanical stimulation enhances osteogenic differentiation in OPLL-derived ligament cells. Nevertheless, the function of hypermobility of the spine on ligament ossification remain unexplored in vivo.

Methods

We created the novel stimulation device to induce spinal hypermobility in mice with heterotopic ossification of the spine ligaments. The mice were randomly divided into three groups, control, slow hypermobility (SH) group and fast hypermobility (FH) group according to the frequency of spinal movement. Ligament ossification and changes in spinal range of motion (ROM) were assessed using micro-CT and X-rays. Morphological alterations were examined through HE staining. Behavioral evaluation was performed using the Basso Mouse Scale (BMS) score and inclined plane test (IPT). Immunofluorescence was employed to examine the expression of related proteins.

Results

After 8 weeks, it showed increased ligament ossification and chondrocyte proliferation both in SH and FH group. After 16 weeks, The BMS score and IPT were lower both in the SH and FH group compared to the controls. Additionally, the ROM of cervicothoracic and thoracolumbar spine was lower in the FH group than in the controls. Immunofluorescence analysis revealed increased levels of SP7, RUNX2, OCN, DLX5, NOTCH1, and HES1 in the ligament tissues of the FH group compared to controls.

Conclusion

spinal hypermobility promotes the progression of ossification in mice with heterotopic ossification of the spine, shedding new light on the pathogenesis of OPLL.

Cervical motion analysis using wearable inertial sensors to patients with cervical ossification of posterior longitudinal ligament

This study aimed to clarify cervical kinematics during daily activities, including level walking and stair ascending, in patients with cervical ossification of the posterior longitudinal ligament (C-OPLL). Eighteen patients with myelopathy caused by C-OPLL and 18 healthy controls were recruited to participate in the study. The sagittal cervical kinematics during level walking and stair ascent were quantitatively assessed using a motion analysis system based on wearable inertial sensors. The Japanese Orthopaedic Association score, Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire, Neck Disability Index, and deep sensation in the lower extremities were assessed in all participants. Nine of 18 patients with C-OPLL presented with deep sensory disturbances. Patients with C-OPLL with deep sensory disturbances exhibited different sagittal plane cervical motion patterns than healthy controls during level walking and stair ascent. During the first phase of stair ascent, both patients with C-OPLL and healthy controls flexed their necks to the same degree; however, during the middle and final phases of stair ascent and all phases of level walking, the mean cervical flexion angle of patients with C-OPLL with deep sensory disturbances was significantly higher than that of patients with C-OPLL without deep sensory disturbance and healthy controls. Our data suggest that patients with C-OPLL presenting with deep sensory disturbances are likely to walk with their necks flexed and gaze downward to observe their steps throughout their daily lives. This habitual neck posture may lead to a vicious cycle of cervical kyphosis and worsening of compressive myelopathy.

Correlation Between Facet Tropism and Ossification of the Posterior Longitudinal Ligament in the Cervical Spine

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To explore the correlation between Facet Tropism (FT) and OPLL in cervical spine.

METHODS

One-hundred patients with OPLL of cervical spine and one-hundred normal participants without OPLL or cervical disc herniation were included in this study, the patients were matched to the normal participants respectively based on the same sex and similar age (±5). For patients, the cervical levels with and without OPLL were categorized into "OPLL group" and "patient control group," respectively. Bilateral facet joint angles at C2/3-C6/7 were measured on sagittal, coronal, and axial planes on CT.

RESULTS

On every planes at the level of C2/3-C6/7,the mean difference between left and right facet angles and FT incidence in the most levels of the OPLL group were significantly greater than those in the control groups (P < 0.001). At the most cervical levels, there was no significant difference in mean difference of facet angles and FT incidence between the 2 control groups. On the axial plane, the incidence of FT in segmental type OPLL patients was significantly higher than that in continuous type OPLL patients (P = 0.036). On the coronal plane, the incidence of FT in segmental type OPLL was significantly higher than that in the other OPLL types (P < 0.001), and local type OPLL had a higher incidence of FT compared to mixed type OPLL (P = 0.016). On the sagittal plane, the incidence of FT in segmental type OPLL was higher than that in continuous type OPLL (P = 0.019) and mixed type OPLL (P = 0.036).

CONCLUSIONS

There is a significant correlation between OPLL of cervical spine and FT. There are significant differences in the incidence of FT among different cervical OPLL types.

Possible involvement of vitamin K insufficiency in the progression of cervical ossification of the posterior longitudinal ligament

Ossification of the posterior longitudinal ligament of the vertebral column (OPLL) is a disease characterised by ectopic bone formation in the spinal ligament that causes progressive neurological impairment. However, there are no suitable treatments for OPLL. Here, we compared the general characteristics and haemostasis of patients with OPLL and those with cervical spondylotic myelopathy. Those with OPLL had significantly longer prothrombin times and lower plasma protein C concentrations, consistent with vitamin K deficiency. Therefore, we next characterised the effects of vitamin K supplementation on spinal hyperostosis in ttw mice, a model of cervical OPLL, by feeding them standard chow, vitamin K-deficient chow, or standard chow accompanied by biweekly vitamin K2 injections for 6 weeks. We found that vitamin K supplementation resulted in longer stride lengths and superior inter-limb coordination using footprint analysis. Furthermore, supplementation caused a significant reduction in ectopic calcification of the cervical ligaments of the mice, according to microcomputed tomography analysis. Finally, supplementation caused an increase in the number of osteochondrogenic cells expressing Gla-rich protein, an inhibitor of ectopic calcification, and increased the circulating concentration. Thus, vitamin K insufficiency may be involved in the pathogenesis of OPLL and supplementation may represent a novel treatment for this condition.

CDUNeXt: efficient ossification segmentation with large kernel and dual cross gate attention

Ossification of the ligamentum flavum (OLF) is the main causative factor of spinal stenosis, but how to accurately and efficiently identify the ossification region is a clinical pain point and an urgent problem to be solved. Currently, we can only rely on the doctor's subjective experience for identification, with low efficiency and large error. In this study, a deep learning method is introduced for the first time into the diagnosis of ligamentum flavum ossificans, we proposed a lightweight, automatic and efficient method for identifying ossified regions, called CDUNeXt. By designing lightweight module structures, utilizing large-kernel convolutions to extracts the long-distance dependencies of different features of the image, and adopting dual-cross-gate-attention(DCGA) to sequentially capture the channel and spatial dependencies so as to fast and accurate segmentation while maintaining fewer parameters and lower complexity. Experiments show that CDUNeXt achieves the best segmentation performance with an optimal balance of lighter weights and less computational cost compared to existing methods. This work fills the gap in the application of deep learning techniques in the diagnosis of ligamentum flavum ossificans, contributes to the realization of lightweight medical image segmentation networks and lays the foundation for subsequent research.

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.

Malignant character of an ossified posterior longitudinal ligament in a hyperflexion injury: A case report

The present study reports the case of a 50-year-old obese male with ankylosing spondylitis, Scheuermann's kyphosis. The patient was asymptomatic concerning the ectopic ossification of the posterior longitudinal ligament (OPLL) at the cervical spine; he developed quadriparesis and respiratory insufficiency following minor head trauma. Even though trauma to the cervical spine in patients with OPLL is common, to the best of our knowledge, this is the first reported case of an extensive osteophyte with a lethal outcome after syncope. In rare occasions, it may be present with syncope and potentially lethal outcomes, particularly when precipitated by trauma. Therefore, the management of OPLL with significant canal stenosis should not be unnecessarily delayed.

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.

The Transaxillary Approach as a Direct Route in the Management of Upper Thoracic Spine Pathology: A Technical Note with Case Series

This retrospective case series of prospective data aims to describe the transaxillary approach for the treatment of upper thoracic spine pathology. Various surgical techniques and approaches have been reported across the literature to address upper thoracic spine pathology, including the cervicothoracic approach, anterior transsternal approach, posterolateral approach, supraclavicular approach, and lateral parascapular approaches. These techniques are invasive. A minimally invasive, less morbid, and direct access approach to the pathology of the upper thoracic spine has not been reported in the literature. Patients with pathology affecting the first thoracic vertebra up to the sixth thoracic vertebra were classified into the upper thoracic spine group. Patients with pathology below the sixth thoracic vertebra were excluded. Patients not having a minimum follow-up of 12 months were also excluded. The study analyzed 18 patients. The mean preoperative modified Japanese Orthopedic Association score was 7.2±1.44, which improved to 10.16±1.2 (p<0.05). The majority (14/18) of the patients had an excellent outcome. Three patients had good outcomes, and one patient had a fair outcome. Five cases of intraoperative dural leak were recorded, and one patient had postoperative neurological deficit. The transaxillary approach is a safe, viable, muscle-sparing, and minimally invasive approach for ventral pathologies of the upper thoracic spine.

Automated Detection of the Thoracic Ossification of the Posterior Longitudinal Ligament Using Deep Learning and Plain Radiographs

Ossification of the ligaments progresses slowly in the initial stages, and most patients are unaware of the disease until obvious myelopathy symptoms appear. Consequently, treatment and clinical outcomes are not satisfactory. This study is aimed at developing an automated system for the detection of the thoracic ossification of the posterior longitudinal ligament (OPLL) using deep learning and plain radiography. We retrospectively reviewed the data of 146 patients with thoracic OPLL and 150 control cases without thoracic OPLL. Plain lateral thoracic radiographs were used for object detection, training, and validation. Thereafter, an object detection system was developed, and its accuracy was calculated. The performance of the proposed system was compared with that of two spine surgeons. The accuracy of the proposed object detection model based on plain lateral thoracic radiographs was 83.4%, whereas the accuracies of spine surgeons 1 and 2 were 80.4% and 77.4%, respectively. Our findings indicate that our automated system, which uses a deep learning-based method based on plain radiographs, can accurately detect thoracic OPLL. This system has the potential to improve the diagnostic accuracy of thoracic OPLL.

Deep learning-based prediction model for postoperative complications of cervical posterior longitudinal ligament ossification

PURPOSE

Postoperative complication prediction helps surgeons to inform and manage patient expectations. Deep learning, a model that finds patterns in large samples of data, outperform traditional statistical methods in making predictions. This study aimed to create a deep learning-based model (DLM) to predict postoperative complications in patients with cervical ossification of the posterior longitudinal ligament (OPLL).

METHODS

This prospective multicenter study was conducted by the 28 institutions, and 478 patients were included in the analysis. Deep learning was used to create two predictive models of the overall postoperative complications and neurological complications, one of the major complications. These models were constructed by learning the patient's preoperative background, clinical symptoms, surgical procedures, and imaging findings. These logistic regression models were also created, and these accuracies were compared with those of the DLM.

RESULTS

Overall complications were observed in 127 cases (26.6%). The accuracy of the DLM was 74.6 ± 3.7% for predicting the overall occurrence of complications, which was comparable to that of the logistic regression (74.1%). Neurological complications were observed in 48 cases (10.0%), and the accuracy of the DLM was 91.7 ± 3.5%, which was higher than that of the logistic regression (90.1%).

CONCLUSION

A new algorithm using deep learning was able to predict complications after cervical OPLL surgery. This model was well calibrated, with prediction accuracy comparable to that of regression models. The accuracy remained high even for predicting only neurological complications, for which the case number is limited compared to conventional statistical methods.

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.

Effect of K‑line on posterior cervical surgery versus anterior cervical surgery in patients with multi-level ossification of posterior longitudinal ligament

PURPOSE

To evaluate the influence of K-line on the outcome of open-door laminoplasty versus anterior cervical corpectomy decompression and fusion (ACCF) for patients with more than two levels of ossification of the posterior longitudinal ligament (OPLL).

METHODS

60 patients undergoing open-door laminoplasty and 62 patients undergoing ACCF from January 2013 to January 2020 with more than 2 years of follow-up were included. Eighty-four cases with the ossification mass not beyond the K-line were grouped as K-line (+), while thirty-eight cases were grouped as K-line (-). The operation time, intraoperative blood loss, hospital stay, preoperative, postoperative, and last follow-up JOA scores, and postoperative complications were investigated.

RESULTS

The improvement rate of JOA scores after posterior approaches in cases of group K-line (+) and K-line (-) was 72.4% and 53.1%, respectively, which showed a significant difference (P < 0.01). In group K-line (+), the improvement of JOA scores for open-door laminoplasty was 73.4% and 71.8% for ACCF, which showed no significant difference (P > 0.05). In group K-line (-), the improvement of JOA scores for ACCF was 52.1% and 42.9% for open-door laminoplasty, which showed a significant difference (P < 0.05). The incidence of C5 palsy was significantly lower in cases with ACCF than in cases with open-door laminoplasty (P < 0.05).

CONCLUSION

For patients with more than two levels of OPLL, preoperative K-line (+) predicates a better outcome than K-line (-). For cases with K-line (-), ACCF provides better neurologic function recovery. For patients with K-line (+), open-door laminoplasty provides the same neurologic function recovery of ACCF.

DLX5 regulates the osteogenic differentiation of spinal ligaments cells derived from ossification of the posterior longitudinal ligament patients via NOTCH signaling

Background

Ossification of the posterior longitudinal ligaments (OPLL) is common disorder characterized by heterotopic ossification of the spinal ligaments. Mechanical stimulation (MS) plays an important role in OPLL. DLX5 is an essential transcription factor required for osteoblast differentiation. However, the role of DLX5 during in OPLL is unclear. This study aims to investigate whether DLX5 is associated with OPLL progression under MS.

Methods

Stretch stimulation was applied to spinal ligaments cells derived from OPLL (OPLL cells) and non-OPLL (non-OPLL cells) patients. Expression of DLX5 and osteogenesis-related genes were determined by quantitative real-time polymerase chain reaction and Western blot. The osteogenic differentiation ability of the cells was measured using alkaline phosphatase (ALP) staining and alizarin red staining. The protein expression of DLX5 in the tissues and the nuclear translocation of NOTCH intracellular domain (NICD) was examined by immunofluorescence.

Results

Compared with non-OPLL cells, OPLL cells expressed higher levels of DLX5 in vitro and vivo (p < 0.01). Upregulated expression of DLX5 and osteogenesis-related genes (OSX, RUNX2, and OCN) were observed in OPLL cells induced with stretch stimulation and osteogenic medium, whereas there was no change in the non-OPLL cells (p < 0.01). Cytoplasmic NICD protein translocated from the cytoplasm to the nucleus inducing DLX5 under stretch stimulation, which was reduced by the NOTCH signaling inhibitors (DAPT) (p < 0.01).

Conclusions

These data suggest that DLX5 play a critical role in MS-induced progression of OPLL through NOTCH signaling, which provides a new insight into the pathogenesis of OPLL.

Augmented Reality Support for Anterior Decompression and Fusion Using Floating Method for Cervical Ossification of the Posterior Longitudinal Ligament

Anterior decompression and fusion (ADF) using the floating method for cervical ossification of the posterior longitudinal ligament (OPLL) is an ideal surgical technique, but it has a specific risk of insufficient decompression caused by the impingement of residual ossification. Augmented reality (AR) support is a novel technology that enables the superimposition of images onto the view of a surgical field. AR technology was applied to ADF for cervical OPLL to facilitate intraoperative anatomical orientation and OPLL identification. In total, 14 patients with cervical OPLL underwent ADF with microscopic AR support. The outline of the OPLL and the bilateral vertebral arteries was marked after intraoperative CT, and the reconstructed 3D image data were transferred and linked to the microscope. The AR microscopic view enabled us to visualize the ossification outline, which could not be seen directly in the surgical field, and allowed sufficient decompression of the ossification. Neurological disturbances were improved in all patients. No cases of serious complications, such as major intraoperative bleeding or reoperation due to the postoperative impingement of the floating OPLL, were registered. To our knowledge, this is the first report of the introduction of microscopic AR into ADF using the floating method for cervical OPLL with favorable clinical results.

Radiologic risk factors associated with development of myelopathy in patients with ossification of the posterior longitudinal ligament of the cervical spine

STUDY DESIGN

Retrospective Cohort Study OBJECTIVE: Myelopathy following ossification of the posterior longitudinal ligament (OPLL) is one of the devastating clinical features in these patients, while we still know little about which factors are associated with development of myelopathy. We evaluated the difference of radiologic measurements between OPLL patients with or without myelopathy and searched for the clinical significance with emphasis on the impact of dynamic motion.

METHODS

305 patients diagnosed of OPLL were enrolled for retrospective review. They were divided into two groups according to the coexistence of radiographic evidence of myelopathy. Demographic data as well as radiologic measures including the presence of disc degeneration (DD), anterior-posterior diameter (APD) of central canal, canal compromise (CC) ratio, global and segmental range of motion (gROM and sROM), OPLL type (morphologic classification) and K-line were collected.

RESULTS

APD (odds ratio (OR); 0.411), CC ratio (OR; 1.100) and sROM (OR; 1.371) were significantly associated with the presence of myelopathy in the multivariate analysis. While the statistically significant factors were same in OPLLs with CC larger than 50%, presence of DD (OR; 4.509) and sROM (OR; 1.295) were significantly associated with myelopathy but not the CC itself in OPLLs with CC smaller than 50%.

CONCLUSIONS

We discovered that the APD, CC ratio and sROM had significant association with development of myelopathy in OPLLs. And the presence of dynamic factors had significant association with myelopathy in OPLLs with smaller CC ratios. This observation and its clinical significance on development of myelopathy might enhance our understanding of OPLL.

Collagen VI in the Musculoskeletal System

Collagen VI exerts several functions in the tissues in which it is expressed, including mechanical roles, cytoprotective functions with the inhibition of apoptosis and oxidative damage, and the promotion of tumor growth and progression by the regulation of cell differentiation and autophagic mechanisms. Mutations in the genes encoding collagen VI main chains, COL6A1, COL6A2 and COL6A3, are responsible for a spectrum of congenital muscular disorders, namely Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM) and myosclerosis myopathy (MM), which show a variable combination of muscle wasting and weakness, joint contractures, distal laxity, and respiratory compromise. No effective therapeutic strategy is available so far for these diseases; moreover, the effects of collagen VI mutations on other tissues is poorly investigated. The aim of this review is to outline the role of collagen VI in the musculoskeletal system and to give an update about the tissue-specific functions revealed by studies on animal models and from patients' derived samples in order to fill the knowledge gap between scientists and the clinicians who daily manage patients affected by collagen VI-related myopathies.

Regulatory Mechanism between Ferritin and Mitochondrial Reactive Oxygen Species in Spinal Ligament-Derived Cells from Ossification of Posterior Longitudinal Ligament Patient

Primary spinal ligament-derived cells (SLDCs) from cervical herniated nucleus pulposus tissue (control, Ctrl) and ossification of the posterior longitudinal ligament (OPLL) tissue of surgical patients were analyzed for pathogenesis elucidation. Here, we found that decreased levels of ferritin and increased levels of alkaline phosphatase (ALP), a bone formation marker, provoked osteogenesis in SLDCs in OPLL. SLDCs from the Ctrl and OPLL groups satisfied the definition of mesenchymal stem/stromal cells. RNA sequencing revealed that oxidative phosphorylation and the citric acid cycle pathway were upregulated in the OPLL group. SLDCs in the OPLL group showed increased mitochondrial mass, increased mitochondrial reactive oxygen species (ROS) production, decreased levels of ROS scavengers including ferritin. ROS and ferritin levels were upregulated and downregulated in a time-dependent manner, and both types of molecules repressed ALP. Osteogenesis was mitigated by apoferritin addition. We propose that enhancing ferritin levels might alleviate osteogenesis in OPLL.

C2 Dome-Like Expansive Laminoplasty Versus C2 Open-Door Laminoplasty for Treating Multilevel Cervical Ossification of the Posterior Longitudinal Ligament Involving C2

BACKGROUND

There are controversies over the treatment of cervical ossification of the posterior longitudinal ligament (OPLL) involving C2.

OBJECTIVE

To compare the outcomes of C2 dome-like expansive laminoplasty (C2DL) and C2 open-door laminoplasty (C2OL) for treating cervical OPLL involving C2.

METHODS

The data of 36 patients undergoing C2OL and 40 patients treated with C2DL because of cervical OPLL involving C2 were retrospectively analyzed. The functional outcomes of the Japanese Orthopedic Association score, Neck Disability Index, 36-Item Short Form Health Survey score, and visual analog scale score for neck pain were compared between the 2 groups. The C2-C7 Cobb angle, cervical range of motion (ROM), and space available for the spinal cord at C2 were measured.

RESULTS

At the final follow-up, the Japanese Orthopedic Association score, Neck Disability Index, and 36-Item Short Form Health Survey score significantly improved in both groups (all P < .05), but with no significant intergroup differences (all P > .05). The visual analog scale score for neck pain reduced significantly in both groups (P < .05), but the patients in the C2OL group experienced more severe neck axial pain (P < .05). The C2-C7 Cobb angle and cervical ROM reduced greatly in both groups (P < .05), but those in the C2OL group decreased more (P < .05). The spinal cord at C2 significantly improved in both groups (P < .05), with no significant intergroup differences (P > .05).

CONCLUSION

C2DL was superior to C2OL in maintaining the cervical alignment and ROM and reducing neck axial pain for treating OPLL involving C2.

Impact of preoperative cervical sagittal alignment for cervical myelopathy caused by ossification of the posterior longitudinal ligament on surgical treatment

BACKGROUND

Surgical procedures for cervical myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) are often chosen based on OPLL size and cervical spine alignment. Recently, cervical sagittal alignment based on sagittal vertical axis (SVA) has received increased attention as an important determinant of radiological and clinical outcomes after surgery. This study aimed to investigate the impact of SVA-based cervical sagittal alignment on surgical treatment for cervical OPLL by reviewing a previous retrospective cohort in which its concept was not taken into account in the surgical procedure choices.

METHODS

We reviewed a total of 96 consecutive patients who underwent surgery for cervical myelopathy caused by OPLL from 2008 to 2014. We performed anterior decompression with fusion (ADF) or posterior decompression with fusion (PDF) on patients with massive OPLL or kyphotic alignment, and we performed laminoplasty (LAMP) on patients without massive OPLL or kyphotic alignment. CSVA (center of gravity of the head - C7 SVA), CL (C2-7 lordotic angle) and C7 slope were measured in cervical X-ray at standing position. Clinical results were evaluated using C-JOA score. We divided patients into two subgroups based on the preoperative CSVA: the Low-CSVA (CSVA <40 mm) and High-CSVA (CSVA ≥40 mm) subgroups.

RESULTS

In the Low-CSVA subgroup, none of the three operations had an effect on the CL. In contrast, in the High-CSVA subgroup, while ADF and PDF had no effect on the CL, LAMP worsened the CL postoperatively. The recovery rates of the C-JOA scores in the Low-CSVA subgroup showed no significant differences among the three operations; however in the High-CSVA subgroup, LAMP resulted in worse recovery rate of the C-JOA score than ADF or PDF.

CONCLUSIONS

LAMP is not suitable for patients with cervical myelopathy caused by OPLL who have high CSVA alignment, even in cases without massive OPLL or kyphotic alignment.

Exosomal miR-140-5p inhibits osteogenesis by targeting IGF1R and regulating the mTOR pathway in ossification of the posterior longitudinal ligament

Background

Ossification of the posterior longitudinal ligament (OPLL) is a disabling disease whose pathogenesis is still unclear, and there are no effective cures or prevention methods. Exosomal miRNA plays an important role in the osteogenesis of ectopic bone. Therefore, we focused on the downregulation of miR-140-5p in OPLL cell-derived exosomes to explore the mechanism by which exosomal miR-140-5p inhibits osteogenesis in OPLL.

Results

Exosomes were isolated by differential centrifugation and identified by transmission electron microscopy, nanoparticle tracking analysis, and exosomal markers. Exosomal RNA was extracted to perform miRNA sequencing and disclose the differentially expressed miRNAs, among which miR-140-5p was significantly downregulated. Confocal microscopy was used to trace the exosomal miR-140-5p delivered from OPLL cells to human mesenchymal stem cells (hMSCs). In vitro, we verified that exosomal miR-140-5p inhibited the osteoblast differentiation of hMSCs by targeting IGF1R and suppressing the phosphorylation of the IRS1/PI3K/Akt/mTOR pathway. In vivo, we verified that exosomal miR-140-5p inhibited ectopic bone formation in mice as assessed by micro-CT and immunohistochemistry.

Conclusions

We found that exosomal miR-140-5p could inhibit the osteogenic differentiation of hMSCs by targeting IGF1R and regulating the mTOR pathway, prompting a further potential means of drug treatment and a possible target for molecular therapy of OPLL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01655-8.

Investigation of the biomarkers involved in ectopic ossification: The shared mechanism in ossification of the spinal ligament

Background: Ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) are multifactor diseases characterized by progressively ectopic ossification in the spinal ligament. However, the shared ossification mechanism of OPLL and OLF remains to be elucidated. The study aims to investigate the common biomarkers related to ectopic ossification and the potential molecular regulatory mechanism.

Methods: Microarray and RNA-seq datasets were obtained from Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) from OPLL and OLF were identified to construct the protein-protein interaction (PPI) network. Furthermore, the hub intersection genes were screened and the diagnostic performance was assessed in the external OLF and OPLL cohorts. We also depicted the landscape of immune cell infiltration and m6A modification meanwhile further estimating the relationship with BMP4.

Results: A total of nine up-regulated DEGs and 11 down-regulated DEGs were identified to construct the PPI networks. The integrative bioinformatic analysis defined five hub genes (BMP4, ADAMTS4, HBEGF, IL11, and HAS2) as the common risk biomarkers. Among them, BMP4 was the core target. ROC analysis demonstrated a high diagnostic value of the hub genes. Moreover, activated B cells were recognized as shared differential immune infiltrating cells and significantly associated with BMP4 in OPLL and OLF. Meanwhile, a strong correlation was detected between the expression pattern of the m6A regulator METTL3 and BMP4.

Conclusion: This study first identified BMP4 as the shared core biomarker in the development of OPLL and OLF. Activated B cells and m6A writer METTL3 might be involved in the osteogenesis process mediated by BMP4. Our findings provide insights into the pathogenesis in the ossification of the spinal ligament and unveil the potential therapeutic targets.

Incidence and risk factors of postoperative symptomatic spinal epidural hematoma in cervical spine surgery: a single center, retrospective study of 18,220 patients

PURPOSE

The goal of this research is to explore the incidence and risk factors of symptomatic spinal epidural hematoma (SSEH) following cervical spine surgery.

METHODS

Patients with SSEH from January 2009 to February 2019 were identified as hematoma group. Two control subjects without SSEH were randomly selected for each patient in SSEH group as control group. We collected gender, age, body mass index (BMI), ossification of the posterior ligament (OPLL), comorbidities, anti-platelet or anti-coagulate treatment, coagulation function, segments, instrumental fixation, surgical approach, surgical procedure, duration of surgery and estimated blood loss, which might affect the occurrence of symptomatic epidural hematoma. T-test and Chi-square test were used to univariable test. Multifactor logistic regression analysis was used to investigate the correlation with symptomatic epidural hematoma, furthermore its causes were explored.

RESULTS

Among 18,220 patients, 43 subjects developed SSEH, the incidence was 0.24%. The median time from the end of index surgery to SSEH was 150  min (25 and 75 percentile: 85  min to 290  min). The neurologic function before evacuation by modified Frankel scale is grade B in 5 patients, C in 32 patients, grade D in 6 patients. All patients' symptoms relieved partially or completely after evacuation. All patients with neurologic deficit worse than grade C pre-evacuation had at least one-grade improvement except for one patient. Multifactor logistic regression revealed OPLL involved segments are significantly correlated to the incidence of postoperative symptomatic epidural hematoma (P < 0.05), with a cut-off value of 1.5 levels.

CONCLUSION

OPLL involved segments are significantly correlated to the incidence of postoperative symptomatic epidural hematoma.

Burosumab Treatment for Autosomal Recessive Hypophosphatemic Rickets Type 1 (ARHR1)

CONTEXT

Autosomal recessive hypophosphatemic rickets (ARHR) are rare, heritable renal phosphate-wasting disorders that arise from overexpression of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23) leading to impaired bone mineralization (rickets and osteomalacia). Inactivating mutations of Dentin matrix protein 1 (DMP1) give rise to ARHR type 1 (ARHR1). Short stature, prominent bowing of the legs, fractures/pseudofractures, and severe enthesopathy are prominent in this patient population. Traditionally, treatment consists of oral phosphate replacement and the addition of calcitriol but this approach is limited by modest efficacy and potential renal and gastrointestinal side effects.

OBJECTIVE

The advent of burosumab (Crysvita), a fully humanized monoclonal antibody to FGF23 for the treatment of X-linked hypophosphatemia and tumor-induced osteomalacia, offers a unique opportunity to evaluate its safety and efficacy in patients with ARHR1.

RESULTS

Monthly administration of burosumab to 2 brothers afflicted with the disorder resulted in normalization of serum phosphate, healing of pseudofracture, diminished fatigue, less bone pain, and reduced incapacity arising from the extensive enthesopathy and soft tissue fibrosis/calcification that characterizes this disorder. No adverse effects were reported following burosumab administration.

CONCLUSION

The present report highlights the beneficial biochemical and clinical outcomes associated with the use of burosumab in patients with ARHR1.

Comparison of surgical outcomes of posterior surgeries between cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament

STUDY DESIGN

Retrospective multicenter study.

OBJECTIVE

To compare the surgical outcomes and complications of posterior decompression between individuals with cervical spondylotic myelopathy (CSM) and those with ossification of the posterior longitudinal ligament (OPLL).

SETTING

Seventeen medical institutions in Japan.

METHODS

This study included 814 individuals with CSM (n = 636) and OPLL (n = 178) who underwent posterior decompression. Propensity score matching of the baseline characteristics was performed to compare surgical outcomes and perioperative complications between the CSM and OPLL groups.

RESULTS

Before propensity score matching, the OPLL group had higher percentage of male individuals, body mass index, and number of stenosis levels and longer duration of symptoms (P < 0.01, P < 0.01, P < 0.01, and P < 0.01, respectively). After matching, the baseline characteristics were comparable between the CSM (n = 98) and OPLL (n = 98) groups. The postoperative Japanese Orthopaedic Association (JOA) scores, preoperative-to-postoperative changes in the JOA scores, and JOA score recovery rates were not significantly different between the groups (P = 0.42, P = 0.47, and P = 0.09, respectively). The postoperative visual analog scale (VAS) score for neck pain and preoperative-to-postoperative changes in the VAS score for neck pain were not significantly different between the groups (P = 0.25 and P = 0.50, respectively). The incidence of perioperative complications was comparable between groups.

CONCLUSION

Neurological improvement and complication rates after surgery were comparable between individuals with CSM and those with OPLL, suggesting similar effectiveness and safety of posterior decompression for both conditions.

Current understanding of tandem spinal stenosis: epidemiology, diagnosis, and surgical strategy

Tandem spinal stenosis (TSS) is defined as the concomitant occurrence of stenosis in at least two or more distinct regions (cervical, thoracic, or lumbar) of the spine and may present with a constellation of signs and symptoms. It has four subtypes, including cervico-lumbar, cervico-thoracic, thoraco-lumbar, and cervico-thoraco-lumbar TSS. The prevalence of TSS varies depending on the different subtypes and cohorts.

The main aetiologies of TSS are spinal degenerative changes and heterotopic ossification, and patients with developmental spinal stenosis, ligament ossification, and spinal stenosis at any region are at an increased risk of developing TSS.

The diagnosis of TSS is challenging. The clinical presentation of TSS could be complex, concealed, or severe, and these features may be confusing to clinicians, resulting in an incomplete or delayed diagnosis. Additionally, a consolidated diagnostic criterion for TSS is urgently required to improve consistency across studies and form a basis for establishing treatment guidelines.

The optimal treatment option for TSS is still under debate; areas of controversies include choice of the decompression range, choice between simultaneous or staged surgical patterns, and the order of the surgeries.

The present study reviews publications on TSS, consolidates current awareness on prevalence, aetiologies, potential risk factors, diagnostic dilemmas and criteria, and surgical strategies based on TSS subtypes. This is the first review to include thoracic spinal stenosis as a candidate disorder in TSS and aims at providing the readers with a comprehensive overview of TSS.

Progression of Spinal Ligament Ossification in Patients with Thoracic Myelopathy

Objective

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

Methods

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

Results

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

Conclusion

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

Genetic Odyssey to Ossification of the Posterior Longitudinal Ligament in the Cervical Spine: A Systematic Review

Despite numerous studies, the pathogenesis of ossification of the posterior longitudinal ligament (OPLL) is still unclear. Previous genetic studies proposed variations in genes related to bone and collagen as a cause of OPLL. It is unclear whether the upregulations of those genes are the cause of OPLL or an intermediate result of endochondral ossification process. Causal variations may be in the inflammation-related genes supported by clinical and updated genomic studies. OPLL demonstrates features of genetic diseases but can also be induced by mechanical stress by itself. OPLL may be a combination of various diseases that share ossification as a common pathway and can be divided into genetic and idiopathic. The phenotype of OPLL can be divided into continuous (including mixed) and segmental (including localized) based on the histopathology, prognosis, and appearance. Continuous OPLL shows substantial overexpression of osteoblast-specific genes, frequent upper cervical involvement, common progression, and need for surgery, whereas segmental OPLL shows moderate-to-high expression of these genes and is often clinically silent. Genetic OPLL seems to share clinical features with the continuous type, while idiopathic OPLL shares features with the segmental type. Further genomic studies are needed to elucidate the relationship between genetic OPLL and phenotype of OPLL.

Could Machine Learning Better Predict Postoperative C5 Palsy of Cervical Ossification of the Posterior Longitudinal Ligament?

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

The objective of this study was to investigate whether machine learning (ML) can perform better than a conventional logistic regression in predicting postoperative C5 palsy of cervical ossification of the posterior longitudinal ligament (OPLL) patients.

SUMMARY OF BACKGROUND DATA

C5 palsy is one of the most common postoperative complications after surgical treatment of OPLL, with an incidence rate of 1.4%-18.4%. ML has recently been used to predict the outcomes of neurosurgery. To our knowledge there has not been a study to predict postoperative C5 palsy of cervical OPLL patient with ML.

METHODS

Four sampling methods were used for data balancing. Six ML algorithms and conventional logistic regression were used for model development. A total of 35 ML prediction model and 5 conventional logistic prediction models were generated. The performances of each model were compared with the area under the curve (AUC). Patients who underwent surgery for cervical OPLL at our institute from January 1998 to January 2012 were reviewed. Twenty-five variables of each patient were used to make a prediction model.

RESULTS

In total, 901 patients were included [651 male and 250 female, median age: 55 (49-63), mean±SD: 55.9±9.802]. Twenty-six (2.8%) patients developed postoperative C5 palsy. Age (P=0.043), surgical method (P=0.0112), involvement of OPLL at C1-3 (P=0.0359), and postoperative shoulder pain (P≤0.001) were significantly associated with C5 palsy. Among all ML models, a model using an adaptive reinforcement learning algorithm and downsampling showed the largest AUC (0.88; 95% confidence interval: 0.79-0.96), better than that of logistic regression (0.69; 95% confidence interval: 0.43-0.94).

CONCLUSIONS

The ML algorithm seems to be superior to logistic regression for predicting postoperative C5 palsy of OPLL patient after surgery with respect to AUC. Age, surgical method, and involvement of OPLL at C1-C3 were significantly associated with C5 palsy. This study demonstrates that shoulder pain immediately after surgery is closely associated with postoperative C5 palsy of OPLL patient.

Diabetes Mellitus-A Risk Factor for the Development of Lumbar Disc Degeneration: A Retrospective Study of an Indian Population

STUDY DESIGN

A retrospective study.

OBJECTIVES

To determine the association between type-2 diabetes mellitus (T2DM) and the severity of lumbar disc degeneration disease (LDDD).

METHODS

We included 199 patients with low back pain (LBP) who visited our hospital from 2016 to 2018. All patients were divided into 3 groups as per inclusion criteria. Group A, patients without DM (n = 75); group B, patients with controlled DM (n = 72); and group C, patients with uncontrolled DM (n = 52). The patients were further subdivided into group B1, DM duration ≤10 years (n = 38); group B2, DM duration >10 years (n = 34); group C1 DM duration ≤10 years (n = 28); and group C2, DM duration >10 years (n = 24). Sex, age, body mass index, occupation, smoking history, alcohol use, and duration of T2DM were recorded. The severity of LDDD was evaluated using the 5-level Pfirrmann grading system. Operated patients' disc materials were sent for histological examination.

RESULTS

Demographic data showed no difference among groups (P > 0.5), except age. Patients with DM showed more severe disc degeneration compared with patients without DM. The average Pfirrmann scores between groups A and B1 had no difference; groups B2, C1, and C2 showed higher average Pfirrmann scores than group A (P < 0.05). Groups B2 and C2 showed higher average Pfirrmann scores than groups B1 and C1 (P < 0.05). Groups C1 and C2 showed higher average Pfirrmann scores than groups B1 and B2 (P < 0.05). The severity of LDDD was significantly related to DM duration in both groups B and C (P < 0.05). DM groups showed increased disc apoptosis and matrix aggrecan fragmentation, disc glycosaminoglycan content and histological analysis were significantly different; the results are similar to Pfirrmann score results.

CONCLUSIONS

DM duration >10 years and uncontrolled DM were risk factors for LDDD.

Retrospective comparison of the surgical results for patients with thoracic myelopathy caused by ossification of the posterior longitudinal ligament: Posterior decompression with instrumented spinal fusion versus modified anterior decompression through a posterior approach

BACKGROUND

In Japan, approximately 75% of patients with thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) are treated by posterior decompression with instrumented spinal fusion (PDF) because of its efficacy and safety. To achieve more effective decompression of the spinal cord using a posterior approach, anterior decompression through a posterior approach was developed. However, this technique has a high risk of postoperative paralysis. We have added a couple of ingenuities to this procedure (modified Ohtsuka procedure). This study was performed to report the surgical results of our modified Ohtsuka procedure and to compare them with the results of PDF.

METHODS

This was a retrospective case series. From 2008 to 2018, we surgically treated 32 patients: 20 patients treated by PDF (PDF group) and 12 patients by our modified Ohtsuka procedure (modified Ohtsuka group) as the initial surgery. All patients were followed up for at least 12 months. The degree of surgical invasion and patients' neurological condition were assessed.

RESULTS

The operative duration and intraoperative blood loss indicated no significant differences (PDF vs. Ohtuska: 507 ± 103 vs. 534 ± 99 min, 1022 ± 675 vs. 1160 ± 685 ml, respectively). The preoperative Japanese Orthopaedic Association (JOA) score was 4.5 ± 2.0 in the PDF group and 3.3 ± 1.4 in the modified Ohtsuka group (p < 0.05). However, the latest JOA score and recovery rate were significantly better in the modified Ohtsuka group than in the PDF group (8.9 ± 1.2 vs. 7.4 ± 2.5 and 70.8 ± 17.6% vs. 44.5 ± 40.2%, respectively). Postoperative paralysis did not occur in the modified Ohtsuka group while four patients had it in the PDF group.

CONCLUSIONS

The present study clearly indicated the modified Ohtsuka group showed significantly better surgical outcomes than the PDF group with the recovery rate ≥70%.

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.

Degenerative Cervical Myelopathy: Development and Natural History [AO Spine RECODE-DCM Research Priority Number 2]

STUDY DESIGN

Narrative review.

OBJECTIVES

To discuss the current understanding of the natural history of degenerative cervical myelopathy (DCM).

METHODS

Literature review summarizing current evidence pertaining to the natural history and risk factors of DCM.

RESULTS

DCM is a common condition in which progressive arthritic disease of the cervical spine leads to spinal cord compression resulting in a constellation of neurological symptoms, in particular upper extremity dysfunction and gait impairment. Anatomical factors including cord-canal mismatch, congenitally fused vertebrae and genetic factors may increase individuals' risk for DCM development. Non-myelopathic spinal cord compression (NMSCC) is a common phenomenon with a prevalence of 24.2% in the healthy population, and 35.3% among individuals >60 years of age. Clinical radiculopathy and/or electrophysiological signs of cervical cord dysfunction appear to be risk factors for myelopathy development. Radiological progression of incidental Ossification of the Posterior Longitudinal Ligament (OPLL) is estimated at 18.3% over 81-months and development of myelopathy ranges between 0-61.5% (follow-up ranging from 40 to 124 months between studies) among studies. In patients with symptomatic DCM undergoing non-operative treatment, 20-62% will experience neurological deterioration within 3-6 years.

CONCLUSION

Current estimates surrounding the natural history of DCM, particularly those individuals with mild or minimal impairment, lack precision. Clear predictors of clinical deterioration for those treated with non-operative care are yet to be identified. Future studies are needed on this topic to help improve treatment counseling and clinical prognostication.

High incidence of venous thromboembolism after acute cervical spinal cord injury in patients with ossification of the posterior longitudinal ligament

Objective: To determine the incidence of venous thromboembolism (VTE) in patients with acute cervical spinal cord injury (SCI) and ossification of the posterior longitudinal ligament (OPLL).Design: Prospective cohort study.Setting: A department of a university hospital in Japan.Participants: This study included 57 patients (OPLL, n = 10; non-OPLL, n = 47) treated for acute cervical SCI between January 2011 and April 2017. Patients were classified according to motor complete paralysis (MC), motor incomplete paralysis (MIC), or normal motor function, based on American Spinal Injury Association (ASIA) Impairment Scale results.Interventions: N/A.Outcome Measures: All patients were screened for VTE by D-dimer monitoring, and some underwent ultrasonography. If ultrasonography indicated deep venous thrombosis (DVT) or if the D-dimers increased to ≥10 µg/mL, patients underwent contrast venography to detect VTE, including DVT or pulmonary embolism. We compared blood coagulability and VTE incidence in the OPLL and non-OPLL groups.Results: VTE occurred in 11 (19.3%) of 57 patients. The incidence of VTE was higher in the OPLL group than in the non-OPLL group (50% vs. 12.8%; P = 0.017) and higher in the MC group (57.1%) than in the MIC (8.3%; P = 0.002) or normal group (5.3%; P = 0.002). In the MC group, VTE occurred in 50% of OPLL patients and in 62.5% of non-OPLL patients (P = 0.529). In the MIC group, VTE occurred in 50% of OPLL patients and in none of the non-OPLL patients (P = 0.022).Conclusions: Patients with OPLL tended to develop VTE after SCI with motor complete and incomplete paralysis.

Autosomal recessive hypophosphatemic rickets type 2 (ARHR2) due to ENPP1-deficiency

Awareness for hypophosphatemic rickets has increased in the last years, based on the availability of specific medical treatments. Autosomal recessive hypophosphatemic rickets type 2 (ARHR2) is a rare form of hypophosphatemic rickets, which is known to develop in survivors of generalized arterial calcification of infancy (GACI). Both disorders are based on a deficiency of ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) and present with a high clinical variability and a lack of a phenotype-genotype association. ARHR2 is characterized by phosphate wasting due to elevated fibroblast growth factor 23 (FGF23) levels and might represent a response of the organism to minimize ectopic calcification in individuals with ENPP1-deficiency. This report reviews the recent clinical and preclinical data on this ultra-rare disease in childhood.

Degenerative Cervical Myelopathy: Towards a Personalized Approach

Degenerative cervical myelopathy (DCM) is a recently coined term encompassing a variety of age-related and genetically associated pathologies, including cervical spondylotic myelopathy, degenerative disc disease, and ligamentous aberrations such as ossification of the posterior longitudinal ligament. All of these pathologies produce chronic compression of the spinal cord causing a clinical syndrome characterized by decreased hand dexterity, gait imbalance, and potential genitourinary or sensorimotor disturbances. Substantial variability in the underlying etiology of DCM and its natural history has generated heterogeneity in practice patterns. Ongoing debates in DCM management most commonly center around clinical decision-making, timing of intervention, and the ideal surgical approach. Pivotal basic science studies during the past two decades have deepened our understanding of the pathophysiologic mechanisms surrounding DCM. Growing knowledge of the key pathophysiologic processes will help us tailor personalized approaches in an increasingly heterogeneous patient population. This article focuses on summarizing the most exciting approaches in personalizing DCM patient treatments including biomarkers, factors affecting clinical decision-making, and choice of the optimal surgical approach. Throughout we provide a concise review on the conditions encompassing DCM and discuss the underlying pathophysiology of chronic spinal cord compression. We also provide an overview on clinical-radiologic diagnostic modalities as well as operative and nonoperative treatment strategies, thereby addressing knowledge gaps and controversies in the field of DCM.

Percutaneous Endoscopic Posterior Decompression for Therapy of Spinal Cord Compression Due to Ossification of the Ligamentum Flavum: A Long-Term Follow-up

BACKGROUND

Thoracic ossification of the ligamentum flavum (OLF) is a pathologic condition that affects ligamentation of the OLF and causes slowly progressive myeloradiculopathy. There is a trend toward performing minimally invasive surgery. In this study, we assess the long-term efficacy of percutaneous endoscopic surgical management of thoracic OLF.

METHODS

Twenty patients with thoracic myelopathy due to thoracic OLF underwent percutaneous endoscopic surgical management. We investigated clinical outcomes and neurologic improvements. Magnetic resonance imaging was performed on all patients preoperatively and postoperatively, and intramedullary signal changes were evaluated.

RESULTS

The operation time averaged at 170.4 minutes (range 110-320 minutes). The mean intraoperative blood loss was 29.6 mL (range 5-100 mL). Cerebrospinal fluid leakage occurred in 1 patient and healed well. The follow-up period ranged from 60 to 72 months. The mean score on the Japanese Orthopedic Association scale improved from (6.0 ± 1.41) preoperatively to (7.83 ± 1.40) at 1 month postoperatively to (9.67 ± 1.30) at the final follow-up (P < 0.05). At the final follow-up stage, 11 patients had excellent outcomes, 6 good, 2 fair, and 1 unchanged, according to the Hirabayashi recovery rate. No patient had postoperative deterioration in neurologic status.

CONCLUSIONS

Percutaneous endoscopic surgical management of thoracic OLF has proven to be both safe and effective for the resection of the OLF in the thoracic spine.

Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire as an outcome measure for ossification of posterior longitudinal ligament patients in East Asia: an investigation of reliability, validity, and responsiveness

Background

The surgical outcomes of individual patient with ossification of the posterior longitudinal ligament (OPLL) can vary depending on various patient-related factors. Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) is a well-developed tool for outcome measurement and considers both disease-specific and general health aspects. This study aimed to investigate the reliability, validity, and responsiveness of the JOACMEQ in patients with OPLL in mainland China and to compare post-operative outcomes of OPLL patients between mainland China and Japan.

Methods

This multicenter trial was performed between July 2009 and June 2019. The procedure for the JOACMEQ translation followed Beaton’s guidelines. All patients enrolled were diagnosed with OPLL and had completed the JOACMEQ, the modified Japanese Orthopaedic Association (mJOA) scale, and the 36-Item Short Form Health Survey (SF-36) before and after surgery. The reliability (Cronbach’s α and Pearson’s correlation), construct validity (factor analysis), concurrent validity (Spearman’s correlation with SF-36) and responsiveness (effect sizes) of JOACMEQ were evaluated. A mixed-model analytic approach was used to analyze differences in postoperative outcomes between the 2 countries.

Results

Ninety-one patients from mainland China and ninety-one patients from Japan were recruited. JOACMEQ showed satisfactory internal consistency (Cronbach’s α=0.75). In test-retest reliability evaluation, except for the bladder function domain, the JOACMEQ domains had good test-retest reliability (0.89–0.96). In factor analysis, most of the items (19/24) were well clustered. Regarding clinical validity, all 5 domains were found to have moderate correlations with the physical component summary (PCS) of SF-36 (r=0.25–0.50), and the bladder function and quality of life domains also had moderate correlations (r=0.25–0.50) with the mental component summary (MCS) of SF-36. JOACMEQ showed a variable responsiveness in different domains (effect size =0.17–0.84; standardized response means =0.15–0.85). Regarding postoperative improvements in the JOACMEQ score, mixed-model analysis revealed a significant difference in the quality of life domain between Chinese and Japanese patients (16.0±18.7 vs. 7.8±17.7, P<0.05).

Conclusions

JOACMEQ generally shows good reliability, good validity and mild responsiveness, and can identify the post-operative improvements in patients with OPLL in mainland China. Chinese OPLL patients showed a significantly larger improvement in postoperative quality of life compared to their Japanese counterparts.

Automated detection of cervical ossification of the posterior longitudinal ligament in plain lateral radiographs of the cervical spine using a convolutional neural network

Cervical ossification of the posterior longitudinal ligament (OPLL) is a contributing factor to spinal cord injury or trauma-induced myelopathy in the elderly. To reduce the incidence of these traumas, it is essential to diagnose OPLL at an early stage and to educate patients how to prevent falls. We thus evaluated the ability of our convolutional neural network (CNN) to differentially diagnose cervical spondylosis and cervical OPLL. We enrolled 250 patients with cervical spondylosis, 250 patients with cervical OPLL, and 180 radiographically normal controls. We evaluated the ability of our CNN model to distinguish cervical spondylosis, cervical OPLL, and controls, and the diagnostic accuracy was compared to that of 5 board-certified spine surgeons. The accuracy, average recall, precision, and F1 score of the CNN for classification of lateral cervical spine radiographs were 0.86, 0.86, 0.87, and 0.87, respectively. The accuracy was higher for CNN compared to any expert spine surgeon, and was statistically equal to 4 of the 5 experts and significantly higher than that of 1 expert. We demonstrated that the performance of the CNN was equal or superior to that of spine surgeons.

Degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) frequently leads to severe neurologic disability but is still frequently underdiagnosed. One explanation may be the variability of the symptoms presented by the patients, from paresthesia to quadriplegia, making it another great masquerader. What do we know? How can we manage better these patients? We will review the keys points concerning its challenging diagnosis (clinical and radiologic), some of the recent discoveries about DCM, notably the underlying genetic mutations identified, linked to its pathophysiology, before addressing the consensual points concerning its management and the major evolutive risk: acute decompensation.

Epidemiology of Spinal Cord Injury: Changes to Its Cause Amid Aging Population, a Single Center Study

OBJECTIVE

To investigate the epidemiologic and demographic characteristics of patients with spinal cord injury (SCI) who were admitted to a department of rehabilitation of a university hospital.

METHODS

This was a descriptive cross-sectional study. Medical records including sex, age at injury, type of disability, traumatic or non-traumatic etiology and presence of ossification of posterior longitudinal ligament (OPLL) of patients with SCI who were admitted to the department of rehabilitation between 2012 and 2018 were reviewed.

RESULTS

Of the 221 cases of SCI, 161 were traumatic and 60 were non-traumatic. The mean age at injury was 52.8 years. People aged 40-49 years showed highest proportion among overall SCI patients (19.0%). The proportion of male patients was higher in traumatic SCI at 4.96:1 than in non-traumatic SCI at 1.30:1. The most common cause of traumatic SCI was falling off (37.3%), followed by motor vehicle crash (35.4%) and tripping over (19.3%). Meanwhile, the most common cause of non-traumatic SCI was neoplasm (35.0%). Tripping over was the leading cause of traumatic SCI in patients aged ≥60 years (42.6%). A high proportion of traumatic SCI patients were found to have underlying OPLL (26.1%), particularly those who were injured by tripping over (64.5%).

CONCLUSION

The mean age of SCI patients was higher than that of previous studies. Falls was the single most common cause of traumatic SCI, and tripping over was the most common cause of injury in the elderly patients. OPLL was prevalent in patients who were injured from tripping over.

Enhanced Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells in Ossification of the Posterior Longitudinal Ligament Through Activation of the BMP2-Smad1/5/8 Pathway

Ossification of the posterior longitudinal ligament (OPLL) is characterized by ectopic OPLL. To date, the specific molecular pathogenesis of OPLL has not been clearly elucidated. In this study, bone marrow-derived mesenchymal stem cells obtained from healthy donors (HD-MSCs) and patients with OPLL (OPLL-MSCs) were cultured in osteogenic differentiation medium for 21 days. The osteogenic differentiation capacity was determined by alizarin red S (ARS) and alkaline phosphatase (ALP) assays. Gene expression levels of osteoblastic markers were measured by quantitative reverse transcription-polymerase chain reaction. Protein levels of related genes and the activation of related signaling pathways were measured by western blotting. LDN193189 was used to inhibit the Smad1/5/8 pathway, and small interfering RNA was used to regulate BMP2 expression. Our results showed that the OPLL-MSCs had stronger ARS staining and ALP activity and higher expression of RUNX2, Osterix, and OCN than the HD-MSCs. During osteogenic differentiation, the Smad1/5/8 pathway was overactivated in the OPLL-MSCs, and LDN193189 inhibition reversed the enhanced osteogenic ability of these cells. Besides, BMP2 was upregulated in the OPLL-MSCs. After BMP2 knockdown, the abnormal osteogenic differentiation of OPLL-MSCs was rescued. Thus, abnormal activation of the BMP2-Smad1/5/8 pathway induces enhanced osteogenic differentiation of OPLL-MSCs compared with HD-MSCs. These findings reveal a mechanism of pathological osteogenesis in OPLL and provide a new perspective on inhibiting pathological osteogenesis by regulating BMP2.

A New Classification for Cervical Ossification of the Posterior Longitudinal Ligament Based on the Coexistence of Segmental Disc Degeneration

Objective

Classification systems for cervical ossification of the posterior longitudinal ligament (OPLL) have traditionally focused on the morphological characteristics of ossification. Although the classification describes many clinical features associated with the shape of the ossification, including the concept of spondylosis seems necessary because of the similarity in age distribution.

Methods

Patients diagnosed with OPLL who presented with increase signal intensity (ISI) on magnetic resonance imaging were surgically treated in our department. The patients were divided into two groups (pure versus degenerative) according to the presence of disc degeneration.

Results

Of 141 patients enrolled in this study, more than half (61%) were classified into the degenerative group. The pure group showed a profound male predominance, early presentation of myelopathy, and a different predilection for ISI compared to the degenerative group. The mean canal compromise ratio (CC) of the ISI was 47% in the degenerative group versus 61% in the pure group (p<0.0000). On the contrary, the global and segment motions were significantly larger in the degenerative group (p<0.0000 and p=0.003, respectively). The canal diameters and global angles did not differ between groups.

Conclusion

Classifying cervical OPLL based on the presence of combined disc degeneration is beneficial for understanding the disorder’s behavior. CC appears to be the main factor in the development of myelopathy in the pure group, whereas additional dynamic factors appear to affect its development in the degenerative group.

Effect of teriparatide on ligamentum flavum mesenchymal stem cells isolated from patients with ossification of the posterior longitudinal ligament

Ossification of the posterior longitudinal ligament (OPLL) within the spinal canal sometimes leads to severe myelopathy. Teriparatide (TPD) is a recombinant human parathyroid hormone (PTH) (1-34), which promotes osteogenesis of mesenchymal stem cells (MSCs) via PTH 1 receptor (PTH1R). Although ligamentum flavum (LF)-MSCs from patients with OPLL have a high osteogenic potency, the effect of TPD on them remains unknown. In this study, we determined PTH1R expression in LF-MSCs from patients with OPLL and investigated whether TPD promotes osteogenic differentiation in them. First, LF-MSCs were isolated from patients with OPLL and cervical spondylotic myelopathy (CSM) (controls). Cultured LF-MSCs were treated with different concentrations of TPD on days 0, 7, and 14. On day 21, osteogenic gene expression was quantified. Mineralization was measured based on optical density after Alizarin Red S staining. LF-MSCs from both groups expressed PTH1R at the same level. TPD did not enhance osteogenic gene expression and mineralization in LF-MSCs from both groups. TPD did not promote the osteogenic differentiation of LF-MSCs from patients with OPLL. Thus, it may be safe for patients with OPLL. However, further confirmation of our results with in vivo studies is necessary.

Comparison of Anterior Controllable Antedisplacement and Fusion With Posterior Laminoplasty in the Treatment of Multilevel Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective, Randomized, and Control Study With at Least 1-Year Follow Up

STUDY DESIGN

A prospective, randomized, controlled study.

OBJECTIVE

To compare anterior controllable antidisplacement and fusion (ACAF) with laminoplasty in the treatment of multilevel ossification of the posterior longitudinal ligament (OPLL), and evaluate the efficacy and safety of this procedure.

SUMMARY OF BACKGROUND DATA

The optimal approach for the treatment of OPLL still remains controversial. Both anterior and posterior approaches have their advantages and disadvantages.

METHODS

Between September 2016 and April 2018, a total of 80 patients with multilevel OPLL were randomized in a 1:1 ratio to ACAF group and laminoplasty group. All patients were followed up at least 1 year. Clinical and radiological results were compared between ACAF group and laminoplasty group.

RESULTS

ACAF took a longer operation time. C5 palsy and axial pain occurred more commonly in laminoplasty group, whereas dysphagia and hoarseness appeared easily in ACAF group. At 1-year follow-up, the final Japanese Orthopedic Association (JOA) score and recovery rate were significant higher in ACAF group than those in laminoplasty group, when occupying rate (OR) was not less than 60%, or K-line was negative. ACAF was also good at preservation of cervical lordosis and sagittal balance, but range of movement of cervical spine in both groups decreased significantly.

CONCLUSION

Generally speaking, ACAF is a safe and effective alternative for multilevel OPLL. Compared with laminoplasty, ACAF is more effective in the cases when OR is not less than 60%, or K-line is negative.

LEVEL OF EVIDENCE

2.

Aberrantly Expressed lncRNAs and mRNAs of Osteogenically Differentiated Mesenchymal Stem Cells in Ossification of the Posterior Longitudinal Ligament

Ectopic bone formation is the chief characteristic of ossification of the posterior longitudinal ligament (OPLL). Emerging evidence has revealed that long non-coding RNAs (lncRNAs) can regulate the osteogenic differentiation of mesenchymal stem cells (MSCs), which are the main cells responsible for bone formation. However, the role of lncRNAs in the pathogenesis of OPLL remains unclear. In this study, 725 aberrantly expressed lncRNAs and 664 mRNAs in osteogenically differentiated MSCs from OPLL patients (OPLL MSCs) were identified by microarrays and confirmed by qRT-PCR assays. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that the most enriched pathways included the p53, JAK-STAT, and PI3K-Akt signaling pathways. The co-expression network showed the interactions between the aberrantly expressed lncRNAs and mRNAs in OPLL MSCs, and the potential targets and transcription factors of the lncRNAs were predicted. Our research demonstrated the aberrantly expressed lncRNA and mRNA and the potential regulatory networks involved in the ectopic bone formation of OPLL. These findings imply that lncRNAs may play a vital role in OPLL, which provides a new perspective on the pathogenesis of OPLL.

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.

Diabetes and Collagen: Interrelations

This review summarizes information on interrelations between diabetes development and collagen metabolism and structure. The growing global problem of diabetes requires the search for new strategies of its complications correction. Among them collagen structure violations and/or its impaired metabolism most often lead to profound disability. Even after several decades of intense studies, pathophysiological mechanisms underlying collagen changes in diabetes mellitus are still not well clear. The main complication is that not only diabetes cause changes in collagen metabolism and structure. Collagens via some mechanisms also may regulate glucose homeostasis, both directly and indirectly. The author also presented the results of own studies on bone and skin type I collagen amino acid composition changes with diabetes. Deepening our understanding of collagen metabolism and diabetes interrelations allows us to optimize approaches to overcome the collagen-mediated consequences of this disease. Recently, it has been clearly demonstrated that use of only antidiabetic agents cannot fully correct such violations. Preparations on the base of flavonoids, collagens and amino acids could be considered as perspective directions in this area of drug development.