The Relationship Between Dural Ossification and Spinal Stenosis in Thoracic Ossification of the Ligamentum Flavum

Diagnosis and Management of Thoracic Myelopathy

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

Treatment of cerebrospinal fluid leakage with prolonged use of subfascial epidural drain and antibiotics in patients of thoracic myelopathy after posterior decompression surgery

Background

Cerebrospinal fluid leakage (CSFL) is a prevalent and vexing complication associated with spine surgery. No standard protocol is available guiding CSFL management, especially for thoracic CSFL. The aim of this study was to retrospectively evaluate the efficacy of prolonged use of subfascial epidural drain and antibiotics to treat CSFL after posterior thoracic decompression surgery.

Methods

Fifty-six patients with an average age of 52.3 years (24-76 years), who underwent thoracic decompression with CSFL (group A) and 65 patients with an average age of 54.9 years (25-80 years) without CSFL (group B) were retrospectively reviewed. Patients in group A had prolonged use of subfascial drainage and antibiotics and patients in group B were treated with conventional methods. The surgical results and rate of wound related complications was compared between the two groups.

Results

The average subfascial drainage time was 7.0 ± 2.7 days (2-16 days) and 3.8 ± 1.4 days (2-7 days) in group A and B, respectively. Higher occupation rate (>49%), presence of dural ossification and higher MRI grade (>2) were more likely to presented with CSFL. In group A, four patients (7.1%) presented with deep wound infection and were successfully managed with wound debridement or intravenous antibiotics. In group B, one patient (1.5%) had a superficial wound infection and was treated with antibiotics. No patients presented with wound dehiscence, wound exudation or CSF fistulation.

Conclusion

The occupation rate of ossified mass and presence of dural ossification were the major risk factors of CSFL. No significant difference in infection rates was observed between the patients in group A and B.

Rethinking the Origin of the Primary Respiratory Mechanism

Spheno-occipital synchondrosis (SOS) is the joint regarded as the most important foundation for understanding cranial osteopathy and craniosacral therapy. SOS is the origin of the primary respiratory mechanism (PRM), a movement between the posterior surface of the body of the sphenoid bone and the anterior surface of the base of the occipital bone. From the PRM perspective, an alteration of the position between the two bone surfaces would create cranial and/or craniosacral dysfunction. These positional alterations of the SOS (in adults and children) would determine specific and schematical movements of the bones of the entire skull, whose movements are recognizable by palpation by trained operators. PRM expression is influenced by other elements, such as movement of the cranial bones, inherent movement of the central nervous system, cyclic movement of cerebrospinal fluid (CSF), mechanical tension of the cranial meninges, and passive movement of the sacral bone between the iliac bones. The article reviews the most up-to-date information on the evolution of cranial sutures/joints and meninges in adulthood, the fluctuations of the CSF, brain, and spinal mass movements. Research should reconsider the motivations that induce the operator to discriminate the palpable cranial rhythmic impulse, and probably, to rethink new cranial dysfunctional patterns.

Development and validation of a novel thoracic spinal stenosis surgical invasiveness index: a single-center study based on 989 patients

BACKGROUND CONTEXT

Surgical invasiveness indices have been established for general spine surgery (surgical invasiveness index [SII]), spine deformity, and metastatic spine tumors; however, a specific index for thoracic spinal stenosis (TSS) has not been developed.

PURPOSE

To develop and validate a novel invasiveness index, incorporating TSS-specific factors for open posterior TSS surgery, which may facilitate the prediction of operative duration and intraoperative blood loss, and the stratification of surgical risk.

STUDY DESIGN

A retrospective observational study.

PATIENT SAMPLE

Overall, 989 patients who underwent open posterior TSS surgeries at our institution during the past 5 years were included.

OUTCOME MEASURES

The operation duration, estimated blood loss, transfusion status, major surgical complications, length of hospital stay, and medical expenses.

METHODS

We retrospectively analyzed the data of 989 consecutive patients who underwent posterior surgery for TSS between March 2017 and February 2022. Among them, 70% (n=692) were randomly placed in a training cohort, and the remaining 30% (n=297) automatically constituted the validation cohort. Multivariate linear regression models of operative time and log-transformed estimated blood loss were created using TSS-specific factors. Beta coefficients derived from these models were used to construct a TSS invasiveness index (TII). The ability of the TII to predict surgical invasiveness was compared with that of the SII and assessed in a validation cohort.

RESULTS

The TII was more strongly correlated with operative time and estimated blood loss (p<.05) and explained more variability in operative time and estimated blood loss than the SII (p<.05). The TII explained 64.2% of operative time and 34.6% of estimated blood loss variation, whereas the SII explained 38.7% and 22.5%, respectively. In further verification, the TII was more strongly associated with transfusion rate, drainage time, and length of hospital stay than SII (p<.05).

CONCLUSIONS

By incorporating TSS-specific components, the newly developed TII more accurately predicts the invasiveness of open posterior TSS surgery than the previous index.

Learning Curve and Clinical Outcomes of Ultrasonic Osteotome-based En Bloc Laminectomy for Thoracic Ossification of the Ligamentum Flavum

OBJECTIVE

Despite rapid advances in minimally invasive surgery, en bloc laminectomy remains the most common surgical approach for treating thoracic ossification of the ligamentum flavum (TOLF). However, the learning curve of this risky operation is rarely reported. Therefore, we aimed to describe and analyze the learning curve of ultrasonic osteotome-based en bloc laminectomy for TOLF.

METHODS

Among 151 consecutive patients with TOLF who underwent en bloc laminectomy performed by one surgeon between January 2012 and December 2017, we retrospectively analyzed their demographic data, surgical parameters, and neurological function. Neurological outcome was evaluated with the modified Japanese Orthopaedic Association (mJOA) scale, and the Hirabayashi method was used to calculate the neurological recovery rate. The learning curve was assessed with logarithmic curve-fitting regression analysis. Univariate analysis methods were used for statistical analysis, including t-test, rank sum test, and chi-square test.

RESULTS

A total of 50% of learning milestones could be reached in approximately 14 cases, and the asymptote in 76 cases. Therefore, 76 of the 151 enrolled patients were defined as the "early group," and the remaining 75 were delimitated as the "late group" for comparison. There was a significant intergroup difference in the corrected operative time (94.80 ± 27.77 vs 65.93 ± 15.67 min, P < 0.001) and the estimated blood loss (median 240 vs 400 mL, P < 0.001). The overall follow-up was 83.1 ± 18.5 months. The mJOA significantly increased from a median of 5 (IQR: 4-5) before the surgery to 10 (IQR: 9-10) at the last follow-up (P < 0.001). The overall complication rate was 37.1%, and no significant intergroup difference was found, except for the incidence of dural tears (31.6% vs 17.3%, p = 0.042).

CONCLUSION

Initially, mastering the en bloc laminectomy technique using ultrasonic osteotome for TOLF treatment can be challenging, but the surgeon's experience improves as the operative time and blood loss decrease. Improved surgical experience reduced the risk of dural tears but was not associated with the overall complication rate or long-term neurological function. Despite the relatively long learning curve, en bloc laminectomy is a secure and valid technique for TOLF treatment.

Short shaft ratio: A novel predictor for dural ossification in patients with ossification of the ligamentum flavum

Background

Dural ossification (DO) is strongly correlated with an increased incidence of complications during the surgery for the patients with thoracic ossification of the ligamentum flavum (OLF). Some methods for predicting DO have emerged, but the accuracy remains to be improved. We aimed to find a more accurate way to predict the appearance of DO.

Methods

Retrospective study was adopted in this study. According to the intraoperative findings, ninety-one patients with thoracic OLF were ultimately included and divided into two groups based on the presence or absence of DO. Patient characteristics and radiographic data were recorded. The residual area ratio (RAR, residual area/cross-section area of normal spinal canal × 100%) and the short shaft ratio (SSR, the length of short shaft of the ellipse-like shape/the length of the spinal canal × 100%) were measured and calculated by 2 independent observers, followed by statistical analysis. The receiver operating characteristic curve was used to evaluate the accuracy of the SSR and RAR in predicting DO.

Results

No significant differences were found in sex, age and BMI between the DO group and the non-DO group. The mean RAR (and standard deviation) in the Non-DO group (62.6% ± 10.2%) was significantly higher (p < 0.001) than that in the DO group (46.1% ± 10.5%). The mean SSR (and standard deviation) in the Non-DO group (61.6% ± 6.0%) was significantly higher (p < 0.001) than that in the DO group (43.6% ± 9.2%). The receiver operating characteristic curve indicated that the SSR and RAR can be used as the efficient indicators to identify DO, and the SSR has a higher accuracy in indicating the presence of DO, with a cutoff value of ＜48.71% (sensitivity of 100% and specificity of 85.0%).

Conclusion

The SSR can be used as a supplement parameter to traditional methods to predict DO, and it could be a better predictor. And, compared with bilateral and bridged type, unilateral type of OLF was more likely to develop DO with a larger SSR.

Surgical outcomes of percutaneous endoscopic thoracic decompression in the treatment of multi-segment thoracic ossification of the ligamentum flavum

BACKGROUND

Previous studies have demonstrated satisfactory outcomes of percutaneous endoscopic thoracic decompression (PETD) for single-segment thoracic ossification of the ligamentum flavum (TOLF). However, the clinical outcomes of PETD in patients with multi-segment TOLF (mTOLF) remain unclear. The aim of the present study was to evaluate the efficacy and safety of PETD for patients with multi-segment mTOLF.

METHODS

Eighteen consecutive patients (41 segments) with mTOLF were treated with PETD between January 2020 and December 2021. The clinical outcomes were evaluated using the modified Japanese Orthopaedic Association (mJOA) score and Visual Analog Scale (VAS), whereas radiographic parameters were measured by cross-section area of the spinal canal and anteroposterior diameter of the spinal cord.

RESULTS

The follow-up period ranged from 14 to 34 months. The mean operation time and blood loss were 154.06 ± 32.14 min and 61.72 ± 12.72 ml, respectively. Hospital stay after first-stage operation was 10.89 ± 2.42 days. The mJOA score and VAS score significantly improved at the final follow-up, with a mean mJOA recovery rate of 63.3 ± 21.90%. The incidence of complications was 12.2% per level. The radiographic outcomes showed adequate decompression of the spinal cord.

CONCLUSIONS

The present study demonstrates that PETD is effective and safe as a minimally invasive procedure to treat patients with mTOLF. All patients showed relief of their symptoms and improvement in neurological function.

Thoracic spondylotic myelopathy in diffuse idiopathic skeletal hyperostosis: a comparative study

BACKGROUND

To explore the characteristics and clinical management of thoracic spinal stenosis with diffuse idiopathic skeletal hyperostosis (DISH).

METHODS

The patients diagnosed with thoracic spondylotic myelopathy who underwent spinal decompression and fusion surgery in a single center between 2012 and 2020 were retrospectively analyzed. All the patients were followed up for at least 2 years. Patients were classified into DISH and non-DISH groups. Demographic, radiographic and clinical parameters were compared between the two groups.

RESULTS

A total of 100 thoracic spondylotic myelopathy patients were included in the study. 22 patients were diagnosed with DISH. The proportion of male patients in the DISH group was higher, and the average BMI was larger. The incidence of upper thoracic vertebrae with ossification of posterior longitudinal ligament (OPLL) (P < 0.05) and lumbar spine with ossification of ligamentum flavum (OLF) was higher (P < 0.05) in DISH the group. The proportion of patients received staged surgery is higher in the DISH group (P < 0.1). There were no significant differences between the two groups in the amount of surgical bleeding, the ratio of cerebrospinal fluid leakage, the time duration of drainage tube placement and the JOA scores.

CONCLUSION

Thoracic spinal stenosis with DISH occurred more in male patients with larger BMI. The posterior decompression and fusion surgery could achieve comparable satisfying clinical outcomes between DISH and non-DISH patients. More proportion of patients received staged surgery in the DISH group; the underline mechanism may be DISH caused more OPLL in the upper thoracic spine and more OLF in the lumbar spine because of mechanical stress.

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

STUDY DESIGN

Systematic review.

BACKGROUND CONTEXT

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Application of Single-Cell and Spatial Omics in Musculoskeletal Disorder Research

Musculoskeletal disorders, including fractures, scoliosis, heterotopic ossification, osteoporosis, osteoarthritis, disc degeneration, and muscular injury, etc., can occur at any stage of human life. Understanding the occurrence and development mechanism of musculoskeletal disorders, as well as the changes in tissues and cells during therapy, might help us find targeted treatment methods. Single-cell techniques provide excellent tools for studying alterations at the cellular level of disorders. However, the application of these techniques in research on musculoskeletal disorders is still limited. This review summarizes the current single-cell and spatial omics used in musculoskeletal disorders. Cell isolation, experimental methods, and feasible experimental designs for single-cell studies of musculoskeletal system diseases have been reviewed based on tissue characteristics. Then, the paper summarizes the latest findings of single-cell studies in musculoskeletal disorders from three aspects: bone and ossification, joint, and muscle and tendon disorders. Recent discoveries about the cell populations involved in these diseases are highlighted. Furthermore, the therapeutic responses of musculoskeletal disorders, especially single-cell changes after the treatments of implants, stem cell therapies, and drugs are described. Finally, the application potential and future development directions of single-cell and spatial omics in research on musculoskeletal diseases are discussed.

Incidence and risk factors of dural ossification in patients with thoracic ossification of the ligamentum flavum

OBJECTIVE

Dural ossification (DO) is a common clinical feature in patients with thoracic ossification of the ligamentum flavum (OLF) and associated with the increased risk of perioperative complications. However, few studies have been conducted to determine the incidence and independent risk factors of DO in patients with thoracic OLF. The aim of this retrospective study was to determine the incidence and independent risk factors of DO in patients with thoracic OLF.

METHODS

A total of 107 patients with thoracic OLF who were admitted to the authors' hospital from December 2020 to December 2021 were included in this study. The independent risk factors of DO in patients with thoracic OLF were determined through univariate analysis followed by multivariate logistic regression analysis with p < 0.05. The diagnostic efficacy of the DO in OLF (DO-OLF) risk classification model was determined on the basis of independent risk factors and evaluated on the basis of sensitivity, specificity, and agreement rate.

RESULTS

The incidence of DO in patients with thoracic OLF was 35% (37/107 patients). The tuberous type according to the Sato classification (OR 9.75, p < 0.01) and larger (≥ 9°) supine local kyphosis angle (LKA) (OR 8.13, p < 0.01) were two independent risk factors of DO in thoracic OLF. The DO-OLF risk classification, a novel approach for the diagnosis of DO in patients with thoracic OLF, was established on the basis of the combination of the tuberous type according to the Sato classification and larger supine LKA. The sensitivity, specificity, and agreement rate of this approach for distinguishing between patients with thoracic OLF at high and low risk of DO were 87%, 93%, and 91%, respectively.

CONCLUSIONS

The incidence of DO in patients with thoracic OLF was 35%. The tuberous type according to the Sato classification and larger supine LKA (≥ 9°) were independent risk factors of DO in patients with thoracic OLF. The novel DO-OLF risk classification approach could serve as an efficient method for predicting DO in patients with thoracic OLF.

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.

Incidence and Risk Factors for Symptomatic Spinal Epidural Hematoma Following Posterior Thoracic Spinal Surgery in a Single Institute

STUDY DESIGN

Case-control study.

OBJECTIVES

To investigate the incidence of symptomatic spinal epidural hematoma (SSEH) and recognize its risk factors in a cohort of patients undergoing posterior thoracic surgery in isolation.

METHODS

From January 2010 to December 2019, patients who developed SSEH after posterior thoracic surgery and underwent hematoma evacuation were enrolled. For each SSEH patient, 2 or 3 controls who did not develop SSEH and underwent the same procedures with similar complexity at the same section of the thoracic spine in the same period were collected. The preoperative and intraoperative factors, blood pressure-related factors and radiographic parameters were collected to identify possible risk factors by comparing between the 2 groups.

RESULTS

A total of 24 of 1612 patients (1.49%) were identified as having SSEH after thoracic spinal surgery. Compared to the control group (53 patients), SSEH patients had significant differences in the APTT (p = 0.028), INR (p = 0.009), ratio of previous spinal surgery (p = 0.012), ratio of cerebrospinal fluid leakage (p = 0.004), thoracic kyphosis (p<0.05), local kyphosis angle (p<0.05), epidural fat ratio at T7 (p = 0.003), occupying ratio of the cross-sectional area (p<0.05) and spinal epidural venous plexus grade (p<0.05). Multiple logistic regression analysis revealed 3 risk factors for SSEH: cerebrospinal fluid leakage, the local kyphosis angle (>8.77°) and the occupying ratio of the cross-sectional area (>49.58%).

CONCLUSIONS

The incidence of SSEH was 1.49% in posterior thoracic spinal surgeries. Large local kyphosis angle (>8.77°), high occupying ratio of cross-sectional area (>49.58%) and cerebrospinal fluid leakage were identified as risk factors for SSEH.

Ossified Ligamentum Flavum: Epidemiology, Treatment, and Outcomes

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

Banner cloud sign: a novel method for the diagnosis of dural ossification in patients with thoracic ossification of the ligamentum flavum

PURPOSE

Dural ossification (DO) is common in patients with ossification of the ligamentum flavum (OLF) and is the leading cause of dural tears. However, the methods used for DO diagnosis are limited. The purpose of this study was to propose a novel CT-based imaging sign, Banner cloud sign (BCs), and clarify its clinical characteristics and correlations with DO.

METHODS

57 OLF patients who underwent thoracic spine decompression surgery in our single-center between January- and October-2018 were recruited and divided into two groups based on the presence of DO. Patient demographics and radiographic data were analyzed. Hematoxylin-eosin staining and micro-CT were used to detect the micro-morphological changes of DO. The diagnostic value of BCs for DO was assessed by sensitivity and specificity.

RESULTS

12 patients with a total of 19 segments were diagnosed as DO. The incidence of DO was 21.1% (12/57) in OLF patients and 9.5% (19/200) in OLF segments. Patients with DO had a shorter disease duration and a higher incidence of cerebrospinal fluid leakage than those without DO. Hematoxylin-eosin staining and micro-CT showed that the dura mater was ossified and fused with ossified ligamentum flavum, and diffusion along the dura mater, like a banner cloud flying on the mountain. The sensitivity and specificity of BCs in DO diagnosis were 78.9 and 90.6%, respectively.

CONCLUSION

BCs can vividly and intuitively describe the imaging features of DO and has high diagnostic accuracy. It could be a promising and valuable method for the diagnosis of DO.

Diffuse Idiopathic Skeletal Hyperostosis Combined with Thoracic Spinal Stenosis Treated by Endoscopic Surgery: A Case Report

CASE

A 48-year-old man presented to our facility with debilitating motor and sensory symptoms due to advanced T10-11 thoracic spinal stenosis secondary to diffuse idiopathic skeletal hyperostosis (DISH). The patient's condition was addressed with endoscopic spine surgery through a yet-to-be-reported interlaminar approach, and at the 12-month follow-up, his neurologic function was significantly improved.

CONCLUSION

Select patients with symptomatic thoracic spinal stenosis secondary to DISH can be effectively managed with endoscopic spine surgery through an interlaminar approach by clinicians with extensive endoscopic spine experience.

The role of cerebrospinal fluid cross-section area ratio in the prediction of dural ossification and clinical outcomes in patients with thoracic ossification of ligamentum flavum

Background

It is imperative to preoperatively distinguish dural ossification (DO) and thus anticipate the risks and outcome of the surgery for patients with ossification of ligamentum flavum (OLF). However, studies have disagreed as to the efficacy of the radiographic signs or factors to predict DO and surgical outcome. In additon, the association between the cerebrospinal fluid cross-section area ratio (CCAR) and DO or clinical outcome had not been reported. The purpose of this study was to analyse CCAR and its role in prediction of DO and neurological function recovery rate in patients with OLF.

Methods

Fifty-two consecutive patients with OLF, who underwent posterior thoracic decompression and fusion between September 2012 and March 2019 at a single institution, were retrospectively reviewed. Demographic data, radiographic signs of DO, CCAR, pre- and postoperative modified Japanese Orthopedic Association (mJOA) score were recorded.

Results

There were 27 patients in the DO group and 25 patients in the non-DO group, with a mean age at surgery of 57.4 years and 53.9 years, respectively. No significant differences were found in sex, age, segment of maximum compression and preoperative mJOA score between the two groups. The receiver operating characteristic curve showed that the value of CCAR had a relatively high value for diagnosis of DO and prediction of neurological function recovery rate (P = .000). According to the value of CCAR, three zones were defined as DO zone (≤14.3%), non-DO zone (≥44.5%), and gray zone (14.3 to 44.5%). When the value of CCAR≤14.3%, the recovery rate was poor or fair, while it had good or excellent recovery when CCAR≥45.2%.

Conclusion

The value of CCAR had a high diagnostic value for prediction of DO and neurological function recovery rate in patients with OLF.

The clinical value of three-dimensional measurement in the diagnosis of thoracic myelopathy caused by ossification of the ligamentum flavum

Background

Thoracic ossification of the ligamentum flavum (OLF) is a major cause of thoracic myelopathy, which is often accompanied by multiple segmental stenosis or other degenerative spinal diseases. However, in the above situations, it is difficult to determine the exact segment responsible. The objective of this study was to analyze three-dimensional (3D) radiological parameters in order to establish a novel diagnostic method for discriminating the responsible segment in OLF-induced thoracic myelopathy, and to evaluate its superiority compared to the conventional diagnostic methods.

Methods

Eighty-one patients who underwent surgery for thoracic myelopathy caused by OLF from 2016 to 2020 were enrolled in this study as the myelopathy group, and 79 patients who had thoracic OLF but displayed no definite neurological signs from 2018 to 2020 were enrolled as the non-myelopathy group. We measured the one-dimensional (1D), two-dimensional (2D), and 3D radiological parameters, calculated their optimal cutoff values, and compared their diagnostic values.

Results

Significant differences were observed in the 1D, 2D, and 3D radiological parameters between the myelopathy and non-myelopathy groups (P<0.01). As a 3D radiological parameter, the OLF volume (OLFV) ratio (OLFV ratio = OLFV/normal canal volume × 100%) was the most accurate parameter for diagnosing OLF-induced thoracic myelopathy, with a diagnostic coincidence rate of 88.1%. We also found that an OLFV ratio of 26.3% could be used as the optimal cutoff value, with a sensitivity of 87.7% and a specificity of 88.6%. Moreover, the OLFV ratio [area under the curve (AUC): 0.92, 95% confidence interval (CI): 0.86-0.95] showed a statistically higher diagnostic value than the 1D and 2D parameters (AUC: 0.75, 95% CI: 0.67-0.81; AUC: 0.84, 95% CI: 0.77-0.89, respectively) (P<0.05). Pearson correlation analysis illustrated that the OLFV ratio was significantly negatively correlated with preoperative modified Japanese Orthopedic Association (mJOA) score (r=-0.73, 95% CI: -0.81 to -0.60, P<0.01).

Conclusions

Our results demonstrate the superiority of the OLFV ratio over the conventional 1D and 2D computed tomography (CT)-based radiological parameters for the diagnosis of OLF-induced thoracic myelopathy. The novel diagnostic method based on the OLFV ratio will help to determine the responsible segment in multi-segmental thoracic OLF or when thoracic OLF coexists with other degenerative spinal diseases. The OLFV ratio also accurately reflects the clinical state of symptomatic patients with thoracic OLF.

The short-term outcomes of minimally invasive decompression surgery in patients with lumbar ossification or calcification of the ligamentum flavum

OBJECTIVE

Although minimally invasive endoscopic surgery techniques are established standard treatment choices for various degenerative conditions of the lumbar spine, the surgical indications of such techniques for specific cases, such as segments with ossification of the ligamentum flavum (OLF) or calcification of the ligamentum flavum (CLF), remain under investigation. Therefore, the authors aimed to demonstrate the short-term outcomes of minimally invasive endoscopic surgery in patients with degenerative lumbar disease with CLF or OLF.

METHODS

This is a retrospective cohort study including consecutive patients who underwent microendoscopic posterior decompression at the authors' institution, where the presence of OLF and CLF did not influence the surgical indication. Fifty-nine patients with OLF and 39 patients with CLF on preoperative CT were identified from the database. Subsequently, two matched control groups (one each matched to the OLF and CLF groups) were created using propensity scores to adjust for age, sex, preoperative Japanese Orthopaedic Association (JOA) score and Oswestry Disability Index, and diagnosis. The background, surgical outcomes, and changes in clinical scores were compared between the matched groups. If there was a significant difference in the improvement of clinical scores, a multivariate linear regression model was applied.

RESULTS

On performing univariate analysis, patients with OLF were found to have a higher body mass index (Mann-Whitney U-test, p = 0.001), higher incidence of preoperative motor weakness (chi-square test, p = 0.019), longer operative time (Mann-Whitney U-test, p < 0.001), and lower improvement in the JOA score (mixed-effects model, p = 0.023) than the matched controls. On performing multivariate analysis, the presence of OLF was identified as an independent variable associated with a poor recovery rate based on the JOA score (multivariate linear regression, p < 0.001). In contrast, there were no significant differences between patients with CLF and their matched controls in terms of preoperative and surgical data and postoperative improvements in clinical scores.

CONCLUSIONS

Although the perioperative surgical outcomes, including the surgical complications, and the in-hospital period did not significantly differ, the short-term improvement in the JOA score was significantly lower in patients with degenerative lumbar disease accompanied by OLF than in the patients from the matched control group. In contrast, there were no significant differences in the short-term improvement in clinical scores and perioperative outcomes between patients with CLF and their matched control group. Thus, the surgical indications of minimally invasive posterior decompression for patients with CLF can be the same as those for patients without CLF; however, the indications for patients with OLF should be further investigated in future studies, including the other surgical methods.

How much space of the spinal canal should be restored by hoisting the vertebrae-OPLL complex for sufficient decompression in anterior controllable antedisplacement and fusion? A multicenter clinical radiological study

BACKGROUND CONTEXT

Anterior controllable antedisplacement and fusion (ACAF) is a novel surgical technique for the treatment of ossification of the posterior longitudinal ligament (OPLL). Its prognostic factors for decompression have not been well studied. Additionally, no detailed radiological standard has been set for hoisting the vertebrae-OPLL complex (VOC) in ACAF.

PURPOSE

To identify the possible prognostic factors for decompression outcomes after ACAF for cervical OPLL, to determine the critical value of radiological parameters for predicting good outcomes, and to establish a radiological standard for hoisting the VOC in ACAF.

STUDY DESIGN

This was a retrospective multicenter study.

PATIENT SAMPLE

A total of 121 consecutive patients with OPLL who underwent ACAF at a point between January 2017 and June 2018 at any one of seven facilities and were monitored for at least 1 year afterward were enrolled in a multicenter study.

OUTCOME MEASURES

Japanese Orthopedic Association (JOA) scores, recovery rate (RR) of neurologic function, and surgical complications were used to determine the effectiveness of ACAF.

METHODS

Patients were divided into two groups according to their RR for neurologic function. Patients with an RR of ≥50% and an RR of <50% were designated as having good and poor decompression outcomes, respectively. The relationship between various possible prognostic factors and decompression outcomes was assessed by univariate and multivariate analysis. The receiver operating characteristic curve was used to determine the optimal cutoff value of the radiological parameters for prediction of good decompression outcomes. Next, the patients were redivided into three groups according to the cutoff value of the selected radiological parameter (postoperative anteroposterior canal diameter [APD] ratio). Patients with postoperative APD ratios of ≤80.7%, 80.7%-100%, and ≥100% were defined as members of the incomplete, optimal, and excessive antedisplacement groups, respectively. Differences in decompression outcomes among the three groups were compared to verify the reliability of the postoperative APD ratio and assess the necessity of excessive antedisplacement.

RESULTS

Multivariate logistic regression analysis showed that patients' age at surgery (odds ratio [OR]=1.18; 95% confidence interval [CI]=1.08-1.29; p<.01) and postoperative APD ratio (OR=0.83; 95% CI=0.77-0.90; p<.01) were independently associated with decompression outcomes. The optimal cutoff point of the postoperative APD ratio was calculated at 80.7%, with 86.2% sensitivity and 73.5% specificity. There were no significant differences in the postoperative JOA scores and RRs between the excessive antedisplacement group and optimal antedisplacement group (p>.05). However, a lower incidence of cerebrospinal fluid leakage and screw slippage was observed in the optimal antedisplacement group (p<.05).

CONCLUSIONS

Patients' age at surgery and their postoperative APD ratio are the two prognostic factors of decompression outcomes after ACAF. The postoperative APD ratio is also the most accurate radiological parameter for predicting good outcomes. Our findings suggest that it is essential for neurologic recovery to restore the spinal canal to more than 80.7% of its original size (postoperative APD ratio >80.7%), and restoration to less than its original size (postoperative APD ratio <100%) will help reduce the incidence of surgical complications. This may serve as a valuable reference for establishment of a radiological standard for hoisting the VOC in ACAF.

The diagnostic accuracy of CT-based "Banner cloud sign" for dural ossification in patients with thoracic ossification of the ligamentum flavum: a prospective, blinded, diagnostic accuracy study protocol

Background

Ossification of the ligamentum flavum (OLF) is the most common cause of thoracic spinal stenosis, which responds poorly to conservative treatment. Thus, surgery is the only effective treatment for OLF. The existence of dural ossification (DO) makes surgery challenging and increases the risk of intra-/post-operative complications. To date, several methods have been proposed to identify DO, but either the diagnostic accuracy is low or the feasibility is poor. Therefore, the aim of this study was to propose a new imaging sign (Banner cloud sign, BCs), evaluate the accuracy of BCs in the diagnosis of DO, and provide reliable evidence-based data for its application in clinical practice.

Methods

A prospective, blinded, diagnostic accuracy study will be conducted to assess and compare the accuracy of BCs in the diagnosis of DO with other radiological signs [Tram track sign (TTs) and Comma sign (Cs)]. A total of 120 patients diagnosed with OLF who underwent decompression at the Peking University Third Hospital between January 2018 and June 2019 will be enrolled. Patients' medical records and imaging data will be retrieved from the hospital database server. An observational group consisting of six spine surgeons (with different seniority levels) and two epidemiological researchers will read the patients' images to identify typical imaging signs and determine the presence of DO. Surgical records will be reviewed to confirm the presence of DO, and the results will serve as the reference standard for estimating accuracy. The primary outcome of the study is to determine the accuracy of BCs for DO diagnosis, and the secondary outcome is to compare the sensitivity, specificity, area under the receiver operating characteristic (ROC) curve and inter-observer reliability of each imaging sign. The time taken and level of confidence in DO diagnosis of each observer will also be compared.

Discussion

This study represents the first large-scale investigation of the diagnostic value of BCs, TTs and Cs in the diagnosis of DO, and will provide convincing evidence about their clinical application.

Trial registration

Registered on 29 February 2020. Trial number is ChiCTR2000030380.

miR-29a-5p Targets SATB2 and Regulates the SIRT1/Smad3 Deacetylation Pathway to Inhibit Thoracic Ligamentum Flavum Cell Osteogenesis

STUDY DESIGN

Experimental analysis of the thoracic ligamentum flavum cell osteogenic differentiation process.

OBJECTIVE

This study aimed to explore the role of miR-29a-5p and special AT-rich sequence-binding protein 2 (SATB2) in a pathological osteogenic process.

SUMMARY OF BACKGROUND DATA

Thoracic ossification of the ligamentum flavum (TOLF) is an uncommon disease wherein ligaments within the spine undergo progressive ossification, resulting in stenosis of the spinal canal and myelopathy. MiR-29a-5p was found to be downregulated in ligament cells from ossified ligament tissue in a previous study. However, whether miR-29a-5p is involved in the process of TOLF has not been investigated.

METHODS

The expression of miR-29a-5p in ligament tissues or in the context of TOLF osteogenic cell differentiation was measured via qRT-PCR. Alkaline phosphatase activity assay and Alizarin red staining were used to analyze cellular osteogenesis. The protein-level expression of SATB2, SIRT1, and Smad3 were measured via immunohistochemistry or western blotting. Dual luciferase reporter assays and western blotting were used to confirm that miR-29a targets SATB2.

RESULTS

SATB2 was found to be upregulated and miR-29a-5p was downregulated in TOLF tissue. We additionally observed decreased miR-29a-5p expression during the process of TOLF osteogenic cell differentiation, and there was a marked reduction in the expression of key mediators of osteogenesis when miR-29a-5p was overexpressed. Consistent with this, when miR-29a-5p was inhibited this led to enhanced osteogenic cell differentiation of these cells. We further found miR-29a-5p to directly target and suppress the expression of SATB2. Knock-down of SATB2 was sufficient to reduce the ability of miR-29a-5p to inhibit osteogenesis, and this also led to decreased SIRT1 expression and Smad3 acetylation.

CONCLUSION

Together our findings indicate that miR-29a-5p is able to prevent thoracic ligamentum flavum cell osteogenesis at least in part via targeting SATB2 and thereby suppressing the SIRT1/Smad3 deacetylation pathway.

LEVEL OF EVIDENCE

N/A.

Precise Surgical Treatment of Thoracic Ossification of Ligamentum Flavum Assisted by O-Arm Computer Navigation: A Retrospective Study

OBJECTIVE

O-arm computer navigation-assisted technology (OACNAT) has been widely used in the treatment of thoracic ossification of ligamentum flavum (TOLF) in recent years, but there are few in-depth studies on the safety and effectiveness of this approach. The purpose of this study was to investigate the clinical effect of accurate surgical treatment for TOLF with OACNAT.

METHODS

From January 2010 to January 2018, the clinical data of 64 patients with TOLF who underwent laminectomy and internal fixation in the Third Hospital of Hebei Medical University were retrospectively reviewed. The patients were divided into group A (with OACNAT, n = 33) and group B (without OACNAT, n = 31) according to the application of OACNAT during the operation. The possible operation-related variables, imaging results, and clinical effects were compared between the 2 groups.

RESULTS

In terms of demographics, there were no significant differences between group A and group B in age, sex, body mass index, smoking, drinking, heart disease, hypertension and diabetes (P > 0.05). In terms of operation-related variables, imaging results, and clinical efficacy, there were significant differences in operation time, wound length, postoperative modified Japanese Orthopaedic Association (JOA) score, JOA score improvement rate, accuracy of screw placement, number of intraoperative fluoroscopy procedures, and cerebrospinal fluid leakage between group A and group B (P < 0.05). There were no significant differences in other variables between the 2 groups (P > 0.05). In contrast to group A, in group B, 2 patients had incorrect segmental localization, 3 patients had residual ossified ligamentum flavum after the operation, and 1 patient had postoperative neurologic impairment. On further analysis, compared with group B, group A had a shorter operation time, more accurate screw placement, fewer fluoroscopy procedures, higher JOA score improvement rate, and lower incidence of complications.

CONCLUSIONS

The use of OACNAT accurately located the position, size, shape, and boundary of ossification of the ligamentum flavum during the operation, which could guide accurate decompression and improve the accuracy of pedicle screw placement. This approach not only reduced the incidence of incorrect segmental localization and incomplete or excessive decompression but also reduced the risk of related complications and improved the accuracy, safety, and effectiveness of the operation.

Population-based design and 3D finite element analysis of transforaminal thoracic interbody fusion cages

OBJECTIVE

To compare the biomechanical characteristics of two transforaminal thoracic interbody fusion cages based on the Chinese population thoracic anatomy.

METHOD

Computed tomography scans of the thoracic spine of 150 patients from our institution were collected and analysed. Two cages were designed based on the anatomical parameters of these patients. Further, we used 3D finite element analysis models to compare the stability of two cages by using Mimics 17.0 and ANSYS 15.0 software.

RESULT

Two kinds of thoracic cages (box and kidney-shaped) were designed. Under the displacement working condition, the two new fusion cages could achieve immediate postoperative stability, but the kidney-shaped cage was better than the box-shaped cage. Under the stress working condition, no highly focused stress area was found in either cages, but the kidney-shaped cage experienced less stress than the box-shaped cage.

CONCLUSION

The kidney-shaped cage is more stable and experiences lesser stress than the box-shaped cage after thoracic intervertebral fusion, and it is more suitable for Chinese transforaminal thoracic interbody fusion.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This article is about thoracic fusion cage design and finite element analysis (FEA) analysis based on the thoracic anatomy parameters. For there is currently no suitable thoracic fusion cage for transforaminal thoracic interbody fusion, the results in this article may have the potential of transferring the two designed cages into clinical use.