Finite element modeling and analysis of effect of preexisting cervical degenerative disease on the spinal cord during flexion and extension

Recent studies have emphasized the importance of dynamic activity in the development of myelopathy. However, current knowledge of how degenerative factors affect the spinal cord during motion is still limited. This study aimed to investigate the effect of various types of preexisting herniated cervical disc and the ligamentum flavum ossification on the spinal cord during cervical flexion and extension. A detailed dynamic fluid-structure interaction finite element model of the cervical spine with the spinal cord was developed and validated. The changes of von Mises stress and maximum principal strain within the spinal cord in the period of normal, hyperflexion, and hyperextension were investigated, considering various types and grades of disc herniation and ossification of the ligamentum flavum. The flexion and extension of the cervical spine with spinal canal encroachment induced high stress and strain inside the spinal cord, and this effect was also amplified by increased canal encroachments and cervical hypermobility. The spinal cord might evade lateral encroachment, leading to a reduction in the maximum stress and principal strain within the spinal cord in local-type herniation. Although the impact was limited in the case of diffuse type, the maximum stress tended to appear in the white matter near the encroachment site while compression from both ventral and dorsal was essential to make maximum stress appear in the grey matter. The existence of canal encroachment can reduce the safe range for spinal cord activities, and hypermobility activities may induce spinal cord injury. Besides, the ligamentum flavum plays an important role in the development of central canal syndrome.Significance. This model will enable researchers to have a better understanding of the influence of cervical degenerative diseases on the spinal cord during extension and flexion.

The Quality of Life of the Patients with Thoracic Ossification of the Ligamentum Flavum after Surgery Using EQ-5D-5L

OBJECTIVE

There is a lack of studies on the quality of life (QoL) after posterior laminectomy in patients with thoracic ossification of the ligamentum flavum (TOLF), and risk factors associated with poor prognosis remain controversial. Therefore, the present study was conducted to illustrate the QoL for TOLF patients after surgery and determine its relationship with their demographic, surgery-related, clinical characteristics and imaging data.

METHODS

One hundred and eighteen patients diagnosed with thoracic myelopathy because of TOLF were enrolled in this retrospective study. They all underwent posterior decompressive laminectomy from August 2010 to January 2022. The QoL was evaluated based on the EQ-5D-5L. Collecting gender, age, number of operations, compressed segments, Frankel grade, complications, body mass index (BMI), symptoms and duration, modified Japanese Orthopaedic Association (mJOA) score (preoperative), follow-up time and type of ossification, increased signal on Sagittal T2-weighted Images (ISST2I), occupancy rate and analyzing by Mann-Whitney U-test, Kruskal-Wallis test, the χ2 -test, and logistic regression tests.

RESULTS

Average follow-up 70.8 months (18-149), the mean age was 59.74 ± 9.81 years and the mean score for the QoL based on the EQ-5D-5 L and visual analogue scale (VAS) score were 0.71 ± 0.28 and 78.88 ± 10.21 at the final follow-up. Moderate and severe problems were found in the pain/discomfort in 22.0% of the patients. These mobility and usual activities numbers were slightly higher (24.6% and 30.4%, respectively). The mean scores for QoL and VAS were significantly higher in patients with mild and moderate neurological impairment, normal BMI, <60 years of age, no dural tears, symptom relief at hospital discharge, unilateral and bilateral ossification on axial CT scan, ≤ 50% spinal canal occupancy on CT and MRI, and none or fuzzy on ISST2I.

CONCLUSION

QoL after posterior laminectomy in TOLF patients is generally satisfactory compared to preoperative levels. Preoperative mJOA score, Age, comorbid diabetes, the major symptom is activity limitation, BMI, ISST2I, Intraoperative dural tears and spinal canal occupancy rate correlate significantly with the corresponding dimensions and are predictive. Age, spinal canal occupancy rate, ISST2I, preoperative mJOA score, BMI are significantly associated with and have predictive value for overall postoperative QoL.

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

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

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.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

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

Background

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

Methods

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

Results

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

Conclusions

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

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Symptomatic thoracic ossification of the ligamentum flavum in a patient with ankylosing spondylitis: Report of a case and review

Background:

Thoracic spinal cord compression due to both ankylosing spondylitis (AS) and ossification of the ligamentum flavum (OLF) is rare.

Case Description:

A 33-year-old male with AS presented with a paraparesis attributed to MR documented T9-T10 OLF/stenosis. He was successfully managed with a decompressive laminectomy; this resulted in marked improvement of his deficit.

Conclusion:

Thoracic OLF and AS rarely contribute T9-T10 spinal cord compression that may be readily relieved with a decompressive laminectomy.

How i do it: biportal endoscopic thoracic decompression for ossification of the ligamentum flavum

BACKGROUND

Currently, decompressive laminectomy with or without concomitant fusion is a standard treatment for ossification of the ligamentum flavum (OLF). However, conventional thoracic decompressive laminectomy is not free of the inevitable destruction of the posterior ligamentous complex, and facet injury may lead to various sequelae.

METHOD

We used the biportal endoscopic technique for posterior thoracic decompression (BE-PTD) and describe the steps with discussion regarding the indications, advantages, possible complications, and ways to overcome complications.

CONCLUSION

BE-PTD can obtain endoscopic visualizations of all the boundaries of the OLF lesion and achieve direct neural decompression of thoracic OLF.

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.

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.

Idiopathic dorsal spinal cord herniation perforating the lamina: a case report and review of the literature

Spinal cord herniation (SCH) is a rare condition associated with tethering of the spinal cord at the ventral dural defect. Idiopathic dorsal spinal cord herniation (IDSCH) is an extremely rare clinical entity. Here, we report the first case of IDSCH perforating the lamina in a patient with a history of ossification of the ligamentum flavum and diffuse idiopathic skeletal hyperostosis. Untethering of the spinal cord was performed by removing the surrounded ossified dura. Although urological symptoms and impaired proprioception remained, progressive neurological deterioration was prevented. Because this disease condition is extremely rare, it should be differentiated from ventral SCH.

Comparison of Surgical Outcomes Between Staged and Simultaneous Decompression of Discontinuous Thoracic Ossification of the Ligamentum Flavum: A Retrospective Study

BACKGROUND

Discontinuous thoracic ossification of the ligamentum flavum (TOLF) is diagnosed according to the number and distribution of involved segments seen on magnetic resonance images. When TOLF causes thoracic myelopathy, surgical intervention for these lesions becomes unavoidable. However, there are few reports on the outcomes of surgery for discontinuous TOLF.

METHODS

The study included 26 patients of mean age 55.0 years who underwent simultaneous (n = 16) or staged (n = 10) decompression of discontinuous TOLF between July 2006 and June 2016. Final neurologic status was evaluated using the modified Japanese Orthopaedic Association (JOA) score. The surgical data and incidence of complications were compared. The mean follow-up duration was 73.3 months.

RESULTS

There was no between-group difference in number of levels decompressed or the amount of intraoperative blood loss. There was a significant improvement in the JOA score from 4.0 before surgery to 8.0 postoperatively, with an average recovery rate of 58.3%. The JOA recovery rate was significantly better in the staged group than simultaneous group (68.4% vs. 52.0%, P < 0.05). However, the incidence of complications was similar between the staged and simultaneous groups including for dural tear (1 vs. 6, P = 0.19), cerebrospinal fluid leak (4 vs. 6, P = 1.00), and transient neurologic deterioration (0 vs. 2, P = 0.51).

CONCLUSIONS

The surgical outcome of staged decompression for discontinuous TOLF seems to be better than that of simultaneous decompression. The complication rates of these 2 strategies are similar.

Surgical outcomes of the thoracic ossification of ligamentum flavum: a retrospective analysis of 61 cases

Background

Thoracic ossification of ligamentum flavum (T-OLF), as one of the causes of thoracic myelopathy, is often combined with other spinal disorders. Concurrent lumbar spinal canal stenosis (LCS) is often obscured by symptoms due to T-OLF, leading to difficulty in identifying the origin of these neurological findings. It is common to be misdiagnosed or delayed diagnosis due to the complicated nature. We evaluated the prevalence, distribution, and clinical characteristics of OLF, especially in patients with LCS.

Methods

The authors performed a retrospective analysis of the outcomes of 61 patients who underwent thoracic surgeries performed for symptomatic T-OLF. In all the patients, whole spine lesions were evaluated preoperatively. We examined the factors related to poor outcomes (the recovery rate of the Japanese Orthopedic Association score for thoracic myelopathy is less than 40%) following OLF surgeries. We compared the clinical outcomes according to whether there was concurrent LCS, and determined the optimal surgical approach.

Results

The occurrence of T-OLF increased with age. Forty-six cases (75.4%) were considered to be tandem T-OLF and LCS (LCS group). An advanced age, and concurrent LCS were associated with a poor outcome after the surgery. The LCS group significantly included a greater number of elderly, and more light-weighted patients with Modic change in thoracic spine and a greater sagittal vertical axis, resulting in the lower neurological recovery. Additional lumbar surgery (13cases) effectively improved both the T-JOA and L-JOA scores (from 6.5 ± 2.0 points to 8.0 ± 1.8 points, p = 0.0406, and from 14.5 ± 4.7 points to 20.7 ± 2.6 points, p = 0.001, respectively) in OLF patients with LCS.

Conclusions

T-OLF was highly associated with other spinal disorders. Poor outcomes in T-OLF surgery could be associated with age and concurrent LCS, and an additional surgery for another lumbar lesion significantly improved neurological findings in T-OLF patients.

Predictive Risk Factors of Poor Preliminary Postoperative Outcome for Thoracic Ossification of the Ligamentum Flavum

Objective

The aim of the present study was to ascertain the independent risk factors of poor preliminary outcome and to reveal the value of these factors in predicting the postoperative prognosis.

Methods

A total of 165 patients diagnosed with thoracic myelopathy because of thoracic ossification of the ligamentum flavum (TOLF) were enrolled in this retrospective study. All of them underwent posterior decompressive laminectomy surgery in our hospital from May 2016 to June 2019. The postoperative improvement of symptoms was evaluated using the modified Japanese Orthopaedic Association (mJOA) scoring system. Clinical data, such as age, sex, body mass index (BMI), duration of symptoms, history of hypertension and diabetes, tobacco use, history of drinking, symptoms of incontinence, number of compressed segments, and preoperative mJOA score, were respectively recorded. Radiologic features data included sagittal maximum spinal cord compression (MSCC), axial spinal canal occupation ratio (SCOR), grades and extension of increased signal on sagittal T2‐weighted images (ISST2I), types of increased signal on axial T2‐weighted images (ISAT2I), and the classification of ossification on axial CT scan and sagittal MRI. The t‐test, the χ²‐test, Fisher's exact test, binary logistic regression analyses, receiver operating characteristic (ROC) curves, and subgroup analyses were used to evaluate the effects of individual risk predictors on surgical outcomes.

Results

A total of 76 men and 89 women were enrolled in this study. The mean age of all patients was 58.53 years. After comparison between two groups, we found some risk factors that may be associated with postoperative outcomes, such as age, preoperative mJOA score, BMI, history of hypertension, MSCC, SCOR, grade and extension of ISST2I, type of ISAT2I, axial type of ossification, and sagittal type of ossification (P < 0.05, respectively). Binary logistic regression analysis revealed that older age (odds ratio [OR] = 1.062, 95% confidence interval [CI] = 1.006–1.121, P = 0.030), number of compressed segments (OR = 1.916, 95% CI = 1.250–2.937, P = 0.003), bilateral and bridged types of ossification (OR = 4 314, 95% CI = 1.454–8.657, P = 0.019; OR = 6.630, 95% CI = 2.580–17.530, P = 0.004), and grade 1 and 2 ISST2I (OR = 8.986, 95% CI =3.056–20.294, P < 0.001; OR = 7.552, 95% CI = 3.529–16.004, P < 0.001) were independent risk factors for a poor preliminary postoperative outcome. ROC curve analysis showed that the grade of ISST2I had an excellent discriminative power (area under the curve [AUC] = 0.817). In addition, risk factors have different values for predicting the clinical outcome in each subgroup.

Conclusion

Age, duration of symptoms, number of compressed segments, SCOR, grade, and extension of ISST2I and classification of ossification were associated with the preliminary prognosis, and the intramedullary increased signal on sagittal T2‐weighted MRI was highly predictive of poor postoperative outcome.

Full-Endoscopic Spine Surgery for the Treatment of Lumbar Ossification of the Ligamentum Flavum: Technical Report

BACKGROUND

Ossification of the ligamentum flavum (OLF) is a relatively common disease in East Asia. Although surgical decompression using a posterior approach is commonly used to treat OLF, there are several different treatment strategies. The purpose of this study is to clarify the technically important points for the treatment of OLF using full-endoscopic spine surgery (FESS).

METHODS

FESS was performed on 7 patients with lumbar OLF. Patients had a mean age of 62.3 years and single-level involvement. Computed tomography and magnetic resonance imaging were used to classify the OLF. Two different types of spinal endoscope were used for posterior decompression. Interlaminal and translaminal approaches were performed in 6 and 1 patient, respectively. Preoperative and postoperative pain was evaluated using the numeric rating scale score.

RESULTS

The mean operation time was 84.1 minutes. Unilateral round-type OLF was treated using a 4.1-mm working channel endoscope. The bilateral type was treated using a 6.4-mm working channel endoscope. A dural tear occurred in 1 patient with beak-type OLF, but no symptoms resulting from the tear were observed. The mean preoperative and postoperative numeric rating scale scores were 7.7 and 1.6, respectively.

CONCLUSIONS

Posterior decompression using FESS can be used to treat patients with lumbar OLF. Unilateral round-type OLF with ipsilateral radiculopathy can be treated using a 4.1-mm working channel endoscope. Bilateral-type OLF with cauda equina symptoms should be treated using a 6.4-mm working channel endoscope.

Identification of the molecular mechanism and diagnostic biomarkers in the thoracic ossification of the ligamentum flavum using metabolomics and transcriptomics

Background

To establish a metabolite fingerprint of ossification of the thoracic ligamentum flavum (OTLF) patients using liquid chromatography-mass spectrometry (LC-MS) in combination with transcriptomic data and explore the potential molecular mechanism of pathogenesis.

Results

The study cohort was composed of 25 patients with OTLF and 23 healthy volunteers as a control group. Thirty-seven metabolites were identified out by UPLC-MS including uric acid and hypoxanthine. Nine metabolites, including uric acid and hypoxanthine, were found with a Variable Importance in Projection (VIP) score over 1 (p < 0.05). Pathway enrichment indicated that purine metabolism pathways and the other four metabolism pathways were enriched. Transcriptomic data revealed that purine metabolism have a substantial change in gene expression of OTLF and that xanthine dehydrogenase (XDH) is the key regulatory factor. Receiver operating characteristic (ROC) analysis indicated that 17 metabolites, including uric acid, were found with an AUC value of over 0.7.

Conclusion

Uric acid might be the potential biomarker for OTLF and play an important role within the detailed pathway. XDH could affect purine metabolism by suppressing the expression of hypoxanthine and xanthine leading to low serum levels of uric acid in OTLF, which could be a focal point in developing new therapeutic methods for OTLF.

Clinical efficacy of single intraoperative 500 mg methylprednisolone management therapy for thoracic myelopathy caused by ossification of the ligamentum flavum

Background

The objective of our study was to compare clinical outcome and postoperative complications between patients with thoracic myelopathy caused by ossification of the ligamentum flavum (OLF) treated with and without intraoperative methylprednisolone (MP).

Methods

This retrospective study enrolled 101 patients who underwent posterior approach surgery for OLF and were followed up at least 1 year. Patients were divided into two groups according to MP use in the operation: MP group (n = 47) and non-MP group (n = 54). Clinical outcomes and complications were evaluated before and after operation and at the last follow-up.

Results

Significant differences were found in modified Japanese Orthopedics Association (mJOA) scores and proportion of Frankel grade (A-C) between the two groups immediately after surgery and at 2-week follow-up. No significant differences were found between the two groups in mJOA score before operation and at the final follow-up. Moreover, no significant differences were observed in recovery rate according to mJOA score at any time points, and there was no significant difference in the proportion of Frankel grade (A-C) between the two groups at final follow-up. There were 13 documented infections: 10 in the MP group and 3 in the non-MP group (P = 0.034).

Conclusion

Management therapy with intraoperative 500 mg MP showed better recovery of nerve function within 2 weeks in patients with thoracic myelopathy caused by OLF compared with those did not receive MP. However, long-term follow-up results showed that there was no significant difference in neurological recovery between patients with intraoperative MP or not. Moreover, intraoperative MP increased the rate of wound infection.

Posterior Percutaneous Endoscopic Technique Through Bilateral Translaminar Osseous Channels for Thoracic Spinal Stenosis Caused by Ossification of the Ligamentum Flavum Combined with Disk Herniation at the T10-11 Level: A Technical Note

BACKGROUND

The occurrence rate of thoracic spinal stenosis caused by ossification of the ligamentum flavum combined with disk herniation is lower than that of ossified ligamentum flavum in the thoracic spine, and the treatment method has rarely been reported. In this paper, we applied an endoscopic technique to a patient with thoracic spinal stenosis caused by ossification of the ligamentum flavum combined with disk herniation at the T10-11 level.

METHODS

We performed surgical decompression of the thoracic spinal cord for a patient diagnosed with thoracic spinal stenosis at the T10-11 level caused by ossification of the ligamentum flavum combined with disk herniation using percutaneous endoscopic surgery via the bilateral translaminar osseous channel approach. Pre- and postoperative computed tomography (CT) scan and magnetic resonance imaging (MRI) examinations were performed, and pre- and postoperative neurologic status was evaluated using the Modified Japanese Orthopaedic Association and visual analog scale scores.

RESULTS

The ossified ligamentum flavum and herniated disk material were removed through this osseous channel. Postoperative CT and MRI scanning revealed adequate decompression of the spinal cord at the T10-11 level. The patient was discharged home on postoperative day 3. At 6-month postoperative follow-up, the patient experienced complete resolution of T12 dermatomal numbness. The strength in her bilateral lower extremities improved slightly to grade 5.

CONCLUSIONS

We have applied percutaneous endoscopic surgery via bilateral translaminar osseous channels for the treatment of thoracic spinal stenosis caused by ossification of the ligamentum flavum combined with disk herniation. This surgery could provide sufficient decompression for thoracic spinal cord with minimum trauma.

Percutaneous full endoscopic posterior decompression of thoracic myelopathy caused by ossification of the ligamentum flavum

PURPOSE

Ossification of ligamentum flavum (OLF) is the leading cause of progressive thoracic myelopathy (TM) in East Asian countries. Surgical decompression is the general treatment for TM. This study investigated the application of percutaneous full endoscopic posterior decompression (PEPD) for the treatment of thoracic OLF.

METHODS

Eighteen patients with TM were treated by PEPD under local anaesthesia. Patients had an average age of 59.1 years and single-level lesions mostly at the lower thoracic vertebrae. Computed tomography and magnetic resonance imaging were used to classify the OLF. The pre- and postoperative neurological statuses were evaluated using the American Spinal Injury Association (ASIA) sensory and motor score, modified Japanese Orthopaedic Association (mJOA) score and Frankel grade.

RESULTS

OLF for all patients was classed as lateral, extended, and enlarged types without comma and tram track signs. Decompression was completed, and a dome-shaped laminotomy was performed through limited laminectomy and flavectomy. Dural tears in 2 patients were the only observed complication. The average score of ASIA sensory and motor, mJOA, as well as the Frankel grade improved significantly after surgery at an average follow-up time of 17.4 months. The average recovery rate (RR) was 47.5% as calculated from the mJOA scores. According to RR, 10 cases were classified as good, 4 cases fair, and 4 cases unchanged.

CONCLUSIONS

For patients with thoracic OLF at a single level and lateral, extended, and enlarged types without comma and tram track signs, it is safe and reliable to perform PEPD, which has satisfactory clinical results. These slides can be retrieved under Electronic Supplementary Material.

Surgical outcome of thoracic myelopathy caused by ossification of ligamentum flavum

Ossification of the ligamentum flavum (OLF) may result in thoracic myelopathy (TM) because of the spinal canal narrowing. The aim of this study was to investigate clinical outcomes of symptomatic thoracic OLF treated using posterior decompressive laminectomy. We made a retrospective review of patients who underwent posterior decompressive laminectomy from 2007 through 2016 for symptomatic TM caused by OLF. Thirty-three patients who had surgery for TM caused by OLF that was diagnosed based on clinical, radiologic, and pathologic evaluations. All patients had undergone decompressive laminectomy and excision of the OLF. The clinical course was evaluated according to modified JOA scores. Magnetic resonance imaging was used to determine the number of vertebral segments demonstrating OLF, the level of thoracic cord involvement, and spine lesions coexisting with OLF. Results showed the neurological status improved at follow up (70.82±32.22months) from a preoperative mean Japanese Orthopaedic Association score of 7.03±1.29 points to 9.52±0.83 points at the last follow up (p<0.01). Recovery outcomes were excellent in 8 patients, good in 22 patients, fair in 2 patients and poor in 1 patient. Surgical complications, which resolved after appropriate and prompt treatment, including cerebrospinal fluid leakage in 4 patient, immediate postoperative neurologic deterioration in 2 patient, and wound infection in 4 patient. Our findings suggest that posterior decompressive laminectomy with or without instrumented fusion is an effective treatment for symptomatic thoracic OLF, which provides satisfactory clinical improvement.

Design of mulitlevel OLF approach ("V"-shaped decompressive laminoplasty) based on 3D printing technology

PURPOSE

To introduce a new surgical approach to the multilevel ossification of the ligamentum flavum (OLF) aided by three-dimensional (3D) printing technology.

METHODS

A multilevel OLF patient (male, 66 years) was scanned using computed tomography (CT). His saved DICOM format data were inputted to the Mimics14.0 3D reconstruction software (Materialise, Belgium). The resulting 3D model was used to observe the anatomical features of the multilevel OLF area and to design the surgical approach. At the base of the spinous process, two channels were created using an osteotomy bilaterally to create a "V" shape to remove the bone ligamentous complex (BLC). The decompressive laminoplasty using mini-plate fixation was simulated with the computer. The physical model was manufactured using 3D printing technology. The patient was subsequently treated using the designed surgery.

RESULT

The operation was completed successfully without any complications. The operative time was 90 min, and blood loss was 200 ml. One month after the operation, neurologic function was recovered well, and the JOA score was improved from 6 preoperatively to 10. Postoperative CT scanning showed that the OLF was totally removed, and the replanted BLC had not subsided.

CONCLUSION

3D printing technology is an effective, reliable, and minimally invasive method to design operations. The technique can be an option for multilevel OLF surgical treatment. This can provide sufficient decompression with minimum damage to the spine and other intact anatomical structures.

Clinical outcomes after decompressive laminectomy for symptomatic ossification of ligamentum flavum at the thoracic spine

Ossification of the ligamentum flavum (OLF) is a rare disease that causes acquired thoracic spinal canal stenosis and thoracic myelopathy. The aim of this study was to investigate clinical outcomes of symptomatic thoracic OLF treated using posterior decompressive laminectomy. We retrospectively analyzed the medical records of 22 patients who underwent posterior decompressive laminectomy for symptomatic thoracic OLF. The surgical results were evaluated using the modified Japanese Orthopaedic Association (JOA) scoring system and Hirabayashi recovery rate. The intensity of pain was evaluated using a visual analog scale (VAS). The mean duration of follow-up was 35.6months. The mean JOA score was significantly improved at final follow-up (9.18±standard deviation of 1.53 points [range, 6-11 points]) compared with before surgery (5.64±2.04 points [range, 3-9 points]) (P<0.001). The mean Hirabayashi recovery rate was 65.49% (range, 20-100%). Recovery outcomes were excellent in nine patients, good in eight patients, fair in four patients and unchanged in one patient. No patient was classified as deteriorated. The VAS scores were 2.82±3.08 before surgery and 0.59±1.05 at final follow-up (P=0.001). Surgical complications, which resolved after appropriate and prompt treatment, included dural tear in five patients, cerebrospinal fluid leakage in one patient, immediate postoperative neurologic deterioration in one patient, epidural hematoma in one patient, and wound infection in one patient. Our findings suggest that posterior decompressive laminectomy is an effective treatment for symptomatic thoracic OLF and provides satisfactory clinical improvement, but surgery for thoracic OLF is associated with a relatively high incidence of complications.

Microendoscopic posterior decompression for the treatment of thoracic myelopathy caused by ossification of the ligamentum flavum: a technical report

PURPOSE

Ossification of the ligamentum flavum (OLF) is a common cause of progressive thoracic myelopathy in East Asia. Good surgical results are expected for patients who already show myelopathy. Surgical decompression using a posterior approach is commonly used to treat OLF. This study investigated the use of microendoscopic posterior decompression for the treatment of thoracic OLF.

METHODS

Microendoscopic posterior decompression was performed on 9 patients with myelopathy. Patients had a mean age of 59.8 years and single-level involvement, mostly at the T10-11 and T11-12 vertebrae. Computed tomography and magnetic resonance imaging were used to classify the OLF. A tubular retractor and endoscopic system were used for microendoscopic posterior decompression. Midline and unilateral paramedian approaches were performed in 2 and 7 patients, respectively. Intraoperative motor evoked potentials (MEPs) of 7 patients were monitored. Pre- and postoperative neurological status was evaluated using the modified Japanese Orthopaedic Association (mJOA) score.

RESULTS

Thoracic OLF for all patients were classed as bilateral type with a round morphology. Improvement of MEPs at least one muscle area was recorded in all patients following posterior decompression. A dural tear in one patient was the only observed complication. The mean recovery rate was 44.9 %, as calculated from mJOA scores at a mean follow-up period of 20 months.

CONCLUSIONS

Microendoscopic posterior decompression combined with MEP monitoring can be used to treat patients with thoracic OLF. The optimal surgical indication is OLF at a single vertebral level and of a unilateral or bilateral nature, without comma and tram track signs, and a round morphology.

Surgical strategies for ossified ligamentum flavum associated with dural ossification in thoracic spinal stenosis

We describe two surgical strategies for treating thoracic spinal stenosis (TSS) with ossification of the ligamentum flavum (OLF) and dural ossification (DO), and discuss their postoperative efficacy. From January 2004 to June 2008, 147 patients underwent TSS surgery. Thirty three of those with intraoperative evidence of OLF and DO were included in the present study. Based on the different intraoperative treatment of the dura, these 33 patients were divided into two groups: Group A, 17 patients who had their dura slit and the ossification excised, and Group B, 16 patients treated by floating the ossified dura by thinning it with a drill. All patients underwent outpatient follow-up. Pre- and postoperative Japanese Orthopaedic Association (JOA) scores and recovery rates were evaluated. The mean follow-up period was 42 months. The incidence of DO with OLF in TSS was 22%. At 1 year follow-up, the mean JOA score improved from 5.12 ± 1.17 to 6.94 ± 0.90 in Group A and from 5.25 ± 1.34 to 7.13 ± 1.41 in Group B. Additionally, the mean JOA score improved from 5.18 ± 1.24 to 7.03 ± 1.16 in TSS patients with DO and from 5.52 ± 1.21 to 7.21 ± 1.18 in TSS patients without DO. The increased cross-sectional area of the pre- and postoperative dural sac at the level of stenosis suggested that decompression was complete. Both decompression methods are feasible for curing TSS with OLF and DO. Moreover, slitting the dura for ossified dura and ligamentum flavum removal to relax the spinal cord is a safe and reliable method. Even though it increased the surgical difficulties and risks, DO did not affect postoperative neurological recovery.

Variables affecting postsurgical prognosis of thoracic myelopathy caused by ossification of the ligamentum flavum

BACKGROUND CONTEXT

Ossification of the ligamentum flavum (OLF) may result in thoracic myelopathy (TM) because of narrowing of the spinal canal. Because symptoms vary and are subjective, diagnosis of TM caused by OLF is sometimes difficult when based on symptoms and physical examination. Posterior decompression is indicated in patients with TM caused by OLF because it is believed that surgery is the most effective treatment. However, surgical outcomes vary. We are unaware of reports of objective presurgical diagnostic parameters, such as neurologic and radiologic findings, relating to the postsurgical prognosis in patients with TM caused by OLF.

PURPOSE

To determine which presurgical and surgical variables were most closely related to postsurgical prognosis of TM caused by OLF.

STUDY DESIGN

Retrospective review of the records of the cohort of patients who had undergone surgery from 1988 through 2008 at the University of Toyama Hospital for TM caused by OLF.

PATIENT SAMPLE

Forty-one patients who had surgery for TM caused by OLF that was progressive, severe, or both and for which the diagnosis was based on clinical, radiologic, and pathologic evaluations.

OUTCOME MEASURES

Relationship between the highest follow-up Japanese Orthopaedic Association (JOA) score for neurologic evaluation and of Hirabayashi's formula to indicate the extent of normalization after surgery with respect to the following 10 variables: age at surgery; sex; duration of presurgical symptoms; complications of diabetes mellitus; complications of hypertension; presence of presurgical hyperreflexia in either or both of the patellar tendon reflex and the Achilles tendon reflex; presurgical impairment of joint position sense in the big toes; number of levels affected by OLF; concurrent spinal lesions including ossification of the posterior longitudinal ligament; and intramedullary change of the spinal cord seen on magnetic resonance imaging (MRI).

METHODS

Multiple linear analyses were used to evaluate the variables related to postsurgical recovery.

RESULTS

Presurgical impairment of joint position sense in the big toe was the most important predictor of the highest postsurgical JOA score and of the highest percentage recovery rate. The number of affected OLF levels also predicted the postsurgical highest JOA score, but not statistically significantly so. Age at surgery, sex, and duration of symptoms presurgically did not affect postsurgical recovery. Complications of diabetes mellitus or of hypertension did not affect percentage recovery rate. The difference between recovery rate in patients with or without concurrent spinal lesions was not significant. Presurgical hyperreflexia was not correlated with recovery. Postsurgical JOA scores and percentage recovery rates of scores in patients whose presurgical MRIs had shown intramedullary signal change were not statistically significantly different from those whose MRIs had not shown signal change.

CONCLUSIONS

An excellent postoperative prognosis is not always possible in patients with TM caused by OLF. It may be important to check for impairment of joint position sense in the big toe, the number of levels affected by OLF, and presurgical intramedullary signal change on MRI before continuing to surgery.

Spontaneous reduction of a floated ossification of the ligamentum flavum after posterior thoracic decompression (floating method); report of a case (abridged translation of a primary publication)

BACKGROUND CONTEXT

Although complete resection is the preferred surgical treatment for ossification of the ligamentum flavum (OLF), it sometimes results in the floating method because of adhesion to, or ossification of, the dura mater. It is difficult to anticipate the degree of floating, and if the floated ossification is large, decompression of the spinal cord may not be sufficient.

PURPOSE

To describe a case of spontaneous reduction of a floated OLF after posterior decompression.

STUDY DESIGN

Case report and review of the literature.

METHODS

A 70-year-old woman with OLF of the thoracic spine presented with gait disturbance. A computed tomographic myelogram showed a large ossification and severe spinal canal stenosis at T10-T11. It also showed slight spinal cord compression by ossification at T9-T10.

RESULTS

We performed a laminectomy with floating ossification at T9-T11 and posterior fusion with a pedicle screw system at T10-T11. After the operation, the patient's neurologic improvement was excellent. Five weeks after the operation, a computed tomogram showed reduction of the floated ossification. Improvement progressed up to 3 months after the operation, bringing a sufficient decompression of the spinal cord, whereas it was insufficient immediately after the operation.

CONCLUSIONS

Our present study is the first report that showed OLF was reduced after the floating method. Reduction of the floated ossification was observed 5 weeks after the operation.