Diagnosis and treatment of ossification of the ligamentum flavum associated with dural ossification

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.

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.

Novel therapeutic strategy in the treatment of ossification of the ligamentum flavum associated with dural ossification

PURPOSE

To investigate the imaging characteristics of thoracic ossification of ligamentum flavum (OLF) combined with dural ossification (DO) and the clinical efficacy of zoning laminectomy.

METHOD

The clinical data of 48 patients with thoracic OLF combined with DO who underwent zoning laminectomy between June 2016 and May 2020 were retrospectively analyzed. The modified Japanese Orthopedic Association (mJOA) score was used to evaluate neurological function before and after surgery, and the clinical efficacy was evaluated according to the improvement rate.

RESULTS

The symptoms of all patients significantly improved after the operation, and the average follow-up time was 27.8 (10-47) months. In addition, the average mJOA score had increased from 5.0 (2-8) preoperatively to 8.7 (6-11) postoperatively (t = 18.880, P < 0.05). The average improvement rate was 62.6% (25-100%), with 16 patients graded as excellent, 21 as good, and 11 as fair. Cerebrospinal fluid leakage occurred in 12 cases (25.0%), and all of them healed well after treatment. No postoperative aggravation of neurological dysfunction, wound infection or hematoma occurred. At the last follow-up, there was no recurrence of symptoms and kyphosis.

CONCLUSION

The Zoning laminectomy described here is both safe and effective.

Comparison of Surgical Results of the Bridge Crane Technique Versus Laminectomy for the Treatment of Thoracic Myelopathy Caused by Ossification of the Ligamentum Flavum

STUDY DESIGN

A retrospective study.

OBJECTIVES

This study aimed to evaluate the safety and effectiveness of the bridge crane technique versus laminectomy for the treatment of thoracic myelopathy caused by ossification of the ligamentum flavum (OLF).

METHODS

Totally 41 patients who underwent surgical decompression due to thoracic OLF from May 2017 to June 2018 in our institution were enrolled in this study and were divided into group BG (bridge crane technique, n = 19) and group L (laminoectomy, n = 22). Demographic data was collected from medical records and the modified Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the neurological outcomes during the follow-up. Surgery-related complications were analyzed.

RESULTS

The mean duration of follow-up was comparable between group BG (19.4 ± 1.5 months) and group L (19.6 ± 1.4 months). No statistical differences were observed between two groups in terms of gender, age, duration of symptoms, preoperative occupying rate, involved levels, operation time, intraoperative blood loss, and complications. The JOA score significantly increased at the final follow-up in both groups. However, patients in group BG had higher JOA score and recovery rate (P < 0.05). Four patients in group L experienced complications, including 3 cerebrospinal fluid (CSF) leakage and one postoperative hematoma. Only one patient in group BG had CSF leakage.

CONCLUSION

The results of this study suggested that bridge crane technique may be relatively safe and effective for patients with symptomatic thoracic OLF with more satisfactory clinical improvement. However, high-quality studies are still required to validate the results of this study.

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.

Analysis of the surgical strategy and postoperative clinical effect of thoracic ossification of ligament flavum with dural ossification

Purpose

Our research was designed to analyse the postoperative clinical results of patients suffering from single-segment thoracic ossification of the ligamentum flavum (TOLF) combined with dural ossification (DO) who underwent posterior laminar decompression and internal fixation.

Methods

This retrospective research included thirty-two patients who underwent surgery for ossifying the ligamentum flavum in the thoracic spine between January 2016 and January 2020. Patients were fallen into one group included patients with evidence of DO during surgery, and the other group included patients without evidence of DO. We assessed and compared general clinical characteristics and health-related outcomes before surgery and during follow-up.

Results

The DO group had a longer operation duration, more blood loss, and longer hospital stay (operation time: 94.75 ± 6.78 min vs. 80.00 ± 10.13 min, p < 0.001; blood loss: 331.67 ± 50.06 ml vs. 253.00 ± 48.24 ml, p < 0.001; length of hospital stay: 13.83 ± 2.76 days vs. 10.05 ± 2.33 days, p < 0.001).

Complications

There were 12 cases of cerebrospinal fluid leakage and 1 case of superficial wound infection in the DO group. However, the neurological recovery and health-associated quality of life (HRQOL) scores showed no statistically significant changes between the DO and non-DO groups (p > 0.05).

Conclusions

Posterior laminectomy and internal fixation combined with intraoperative resection of the ossified ligamentum flavum and dura is an efficient and relatively safe method for treating TOLF with DO, which can provide satisfactory results. Moreover, DO had no significant effect on postoperative neurological recovery and health-related quality of life scores.

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.

Thoracic ossification of the ligamentum flavum causing acute myelopathy in a patient with cervical ossification of the posterior longitudinal ligament: illustrative case

BACKGROUND

Ossification of the ligamentum flavum (OLF) has been well characterized as a distinct entity but also in tandem with ossification of the posterior longitudinal ligament (OPLL) in noncontiguous spinal regions. The majority of OLF cases are reported from East Asian countries where prevalent, but such cases are rarely reported in the North American population.

OBSERVATIONS

The authors present a case of a Thai-Cambodian American who presented with symptomatic thoracic OLF in tandem with asymptomatic cervical OPLL. A “floating” thoracic laminectomy, resection of OLF, and partial dural ossification (DO) resection with circumferential release of ossified dura were performed. Radiographic dural reexpansion and spinal cord decompression occurred despite the immediate intraoperative appearance of persistent thecal sac compression from retained DO.

LESSONS

Entire spinal axis imaging should be considered for patients with spinal ligamentous ossification disease, particularly in those of East Asian backgrounds. A floating laminectomy is one of several surgical approaches for OLF, but no consensus approach has been clearly established. High surgical complication rates are associated with thoracic OLF, most commonly dural tears/cerebrospinal fluid (CSF) leaks. DO commonly coexists with OLF, is recognizable on computed tomographic scans, and increases the risk of CSF leaks.

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 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.

CT-Guided Percutaneous Lumbar Ligamentum Flavum Release by Needle Knife for Treatment of Lumbar Spinal Stenosis: A Case Report and Literature Review

Case

The patient was a 62-year-old woman presenting with low-back pain of 3 years’ duration and numbness in the right leg.

Diagnosis

She was diagnosed with lumbar spinal stenosis based on combined magnetic resonance imaging, physical examination, and symptoms.

Interventions

Treatment with computed tomography–guided percutaneous release of the ligamentum flavum was delivered.

Outcomes

Relief of symptoms immediately after treatment and complete resolution of symptoms after 1 month were achieved. At follow-up, there was no recurrence of symptoms after 2, 4, 6, and 12 months.

Conclusion

Lumbar ligamentum flavum hypertrophy is an important cause of degenerative lumbar spinal stenosis. The hypertrophic ligamentum flavum can directly compress the spinal canal, squeeze the cauda equina, and simultaneously lead to a reduction in the anteroposterior diameter of the intervertebral foramen, which compresses the nerve roots and causes numbness and other symptoms of lower extremities. In clinical practice, doctors should combine imaging findings with patient symptoms for diagnosis and an individualized treatment plan for each patient with lumbar spinal stenosis, and conduct gradual stepwise treatment using conservative minimally invasive surgery to prevent excessive surgery.

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Ultrasonic bone scalpel for thoracic spinal decompression: case series and technical note

Background

Thoracic spinal stenosis (TSS) is a rare but intractable disease that fails to respond to conservative treatment. Thoracic spinal decompression, which is traditionally performed using high-speed drills and Kerrison rongeurs, is a time-consuming and technically challenging task. Unfavorable outcomes and high incidence of complications are the major concerns. The development and adaptation of ultrasonic bone scalpel (UBS) have promoted its application in various spinal operations, but its application and standard operating procedure in thoracic decompression have not been fully clarified. Therefore, the purpose of this study is to describe our experience and technique note of using UBS and come up with a standard surgical procedure for thoracic spinal decompression.

Methods

A consecutive of 28 patients with TSS who underwent posterior thoracic spinal decompression surgery with UBS between December 2014 and May 2015 was enrolled in this study. The demographic data, perioperative complications, operation time, estimated blood loss, and pre- and postoperative neurological statuses were recorded and analyzed. Neurological status was evaluated with a modified Japanese Orthopaedic Association (JOA) scale, and the neurological recovery rate was calculated using the Hirabayashi’s Method.

Results

Thoracic spinal decompression surgery was successfully carried out in all cases via a single posterior approach. The average age at surgery was 49.7 ± 8.5 years. The mean operative time of single-segment laminectomy was 3.0 ± 1.4 min, and the blood loss was 108.3 ± 47.3 ml. In circumferential decompression, the average blood loss was 513.8 ± 217.0 ml. Two cases of instrument-related nerve root injury occurred during operation and were cured by conservative treatment. Six patients experienced cerebrospinal fluid (CSF) leakage postoperatively, but no related complications were observed. The mean follow-up period was 39.7 ± 8.9 months, the average JOA score increased from 4.7 before surgery to 10.1 postoperatively, and the average recovery rate was 85.8%.

Conclusions

The UBS is an optimal instrument for thoracic spinal decompression, and its application enables surgeons to decompress the thoracic spinal cord safely and effectively. This standard operating procedure is expected to help achieve favorable outcomes and can be used to treat various pathologies leading to TSS.

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

BACKGROUND

Dural ossification represents a difficult problem in the surgical management of thoracic ossification of the ligamentum flavum. Few studies have focused on this condition because of the relatively low prevalence. We speculated that dural ossification occurs only when spinal stenosis of patients with thoracic ossification of the ligamentum flavum progresses. Herein, we aimed to determine the relationship between dural ossification and spinal stenosis in thoracic ossification of the ligamentum flavum.

METHODS

In this study, 123 consecutive patients with ossification of the ligamentum flavum were retrospectively analyzed. Sixty-seven patients were ultimately included and were divided into a group that had dural ossification and a group that did not have dural ossification. Patient characteristics and radiographic data were recorded. The cross-sectional area occupying ratio ([1 - cross-sectional area of the narrowest level/normal cross-sectional area] × 100%) was measured and was calculated by 3 independent observers, followed by statistical analysis.

RESULTS

The 2 groups were comparable with respect to sex, age, body mass index, and distribution of the segment with maximum compression. The mean cross-sectional area occupying ratio (and standard deviation) in the T9-T12 subgroup in the group with dural ossification (63.4% ± 8.6%) was significantly higher (p < 0.001) than that in the group without dural ossification (30.7% ± 10.4%). The overall interobserver reliability for measurements of the cross-sectional area occupying ratio (interclass correlation coefficient, 0.976) was excellent. Thus, the cross-sectional area occupying ratio could be used as an indicator to distinguish between patients with ossification of the ligamentum flavum who did and did not have dural ossification, with a high diagnostic value, in the T9-T12 subgroup. A cross-sectional area occupying ratio of >55% (sensitivity of 81.5% and specificity of 100%), the "ossification zone," was indicative of dural ossification in patients with ossification of the ligamentum flavum, whereas a value of <45% (sensitivity of 100% and specificity of 89.7%) was considered safe. Moreover, ratios between 45% and 55% were considered to be in the "gray zone."

CONCLUSIONS

The results of this study indicate that the severity of spinal stenosis was significantly associated with dural ossification in ossification of the ligamentum flavum and the cross-sectional area occupying ratio may be used as an indicator of dural ossification in the lower thoracic spine.

CLINICAL RELEVANCE

The diagnosis of dural ossification was based on the intraoperative evidence, and the results could help spine surgeons to prepare for the surgical procedure.

Imaging grading system for the diagnosis of dural ossification based on 102 segments of TOLF CT bone-window data

Thoracic ossification of the ligamentum flavum (TOLF) complicated with dural ossification (DO) is a severe clinical disease. The diagnosis of DO preoperatively remains challenging. The current study retrospectively analyzed imaging features of 102 segments with TOLF from 39 patients and proposed a grading system for evaluating DO risk. Logistic regression results showed that unilateral spinal canal occupational rate (UCOR), tram track signs, and C-signs were all risk factors for DO (odds ratios of 5.393, 19.734 and 72.594, respectively). In validation analyses for the TOLF-DO grading system, sensitivity was 76.0% (19/25), specificity was 91.0% (70/77), and Youden’s index was 0.66. Thus, implementation of the TOLF-DO grading system has the potential to improve the diagnosis of DO.

Dural ossification associated with ossification of ligamentum flavum in the thoracic spine: a retrospective analysis

OBJECTIVES

To investigate the incidence, distribution and radiological characteristics of dural ossification (DO) associated with ossification of ligamentum flavum (OLF) in the thoracic spine.

DESIGN

A retrospective radiographical analysis.

SETTING

This study was conducted at a single institution in China.

PARTICIPANTS

53 patients with OLF who underwent posterior decompression surgery between January 2011 and July 2015 in a single institution were enrolled in this study. The decompression segments were grouped according to imaging evaluation and intraoperative evidences.

OUTCOME MEASURES

The demographic distribution, radiological data and detailed surgical records were collected. First, preoperative CT images of decompressed segments were evaluated to identify imaging signs of DO. The 'tram tack sign' (TTS), 'comma sign' and 'bridge sign' were considered as characteristic imaging findings of DO in OLF. 4 kinds of confusing signs (false TTS) were identified and excluded. Then detailed surgical records were reviewed to finally identify segments with DO.

RESULTS

The incidence of DO in patients with OLF was 43.4%. The incidence of DO in OLF segments was 21.5%. OLF was more common in the lower thoracic spine, and more than half (53.8%) of the DO was located in T9-T12. TTS was the most common sign, but it might be misdiagnosed. After excluding 4 kinds of false TTS, the sensitivity and specificity of imaging diagnosis were 94.23% and 94.21%, respectively.

CONCLUSIONS

DO was relatively common in thoracic OLF, especially in T9-T12. TTS might be misdiagnosed. After excluding 4 kinds of false TTS, the accuracy of imaging diagnosis was relatively high.

A potential mechanism of dural ossification in ossification of ligamentum flavum

Ossification of the ligamentum flavum (OLF) mostly occurs in the thoracic spine, leading to thoracic spinal stenosis. Surgical treatment is considered as the best option for OLF patients. When the dura mater ossifies, the difficulty of surgery and the risk of complications significantly increase. The cause of dural ossification (DO) is still unknown. Based on the existing research and clinical studies, we propose a potential mechanism of DO in OLF. Firstly, with the progression of OLF, it will compress the dura mater and even the spinal cord. Then, with flexion and extension of spine, relative movement (friction) between the ossified ligamentum flavum and compressed dura mater will lead to local inflammation, subsequently causing dural adhesion. Finally, the adhesion tissue can serve as a pathway for the transportation of osteogenic cytokines (BMP for example) from the ossified ligamentum flavum to the compressed dura mater. Dura will ossify under exposure of these osteogenic cytokines. If this hypothesis is confirmed, it will contribute to the prevention and management of DO. For progressive OLF patients, early surgical treatment before DO should be recommended.

Clinical characteristics and surgical outcome of thoracic myelopathy caused by ossification of the ligamentum flavum: a retrospective analysis of 85 cases

STUDY DESIGN

A retrospective comparative study.

OBJECTIVES

To describe the clinical features and radiological findings, to assess the safety and effectiveness of posterior decompressive laminectomy and resection of the ossification of the ligamentum flavum (OLF), and to determine which presurgical and surgical variables were most closely related to postsurgical prognosis of thoracic myelopathy (TM) caused by OLF in China.

METHODS

Eighty-five patients with the diagnosis of TM caused by OLF received surgical treatment from July 1998 to May 2012. Clinical data were collected from medical and operative records. Correlations between the surgical outcome and various factors were also analyzed.

RESULTS

All cases were followed up for a mean of 49.2 months (range, 24-190 months) postoperatively. The mean Japanese Orthopaedic Association score was 3.8 points preoperatively and 8.2 points at the final follow-up, yielding a mean recovery rate of 63.0%. Postoperative complications included transient neurological deficits (9 cases), persistent neurological deficits (4 cases), dural tears (17 cases), cerebrospinal fluid leakage (9 cases), wound dehiscence (2 cases) and wound infection (3 cases). The OLF level (middle thoracic), preoperative duration of symptoms, intramedullary signal change on T2WI and preoperative severity of myelopathy were important predictors of surgical outcome.

CONCLUSIONS

Biomechanical and anatomical factors may have a key role in thoracic OLF progression. Posterior decompressive laminectomy and resection of the OLF can be considered an effective, reliable and safe alternative procedure. The OLF level, preoperative duration of symptoms, intramedullary signal change on T2WI and preoperative severity of myelopathy were confirmed and significantly correlated with the surgical outcome.

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.

Ossification of the ligamentum flavum

Ossification of the ligamentum flavum is a rare cause of thoracic myelopathy. It develops in East Asians more frequently than in people from other areas. The exact pathophysiology has not been elucidated yet; however, it largely depends on biomechanical alterations, especially changes in the tensile force. Because the spinal cord is compressed from the posterior side, the first and most common clinical manifestation is usually loss of functional gait and spastic paralysis, which develop as the spinal cord compression progresses. The choice of diagnostic imaging is T2 sagittal magnetic resonance imaging scanning. Whole spine scanning is mandatory to identify multiple areas of compression and any associated distal lumbar diseases. Fine computed tomography imaging is necessary to make a differential diagnosis and set up a precise surgical plan. Conservative treatment does not work in this disorder. Decompression surgery is the only option and prognosis after surgical treatment is better with this disorder than with other causes of thoracic myelopathy. The severity of preoperative symptoms and the time interval before surgical treatment are the most important prognostic factors.

Spinal dural ossification causing neurological signs in a cat

A six-year-old Ragdoll cat underwent examination due to a six-month history of slowly progressive gait abnormalities. The cat presented with an ambulatory tetraparesis with a neurological examination indicating a C1-T2 myelopathy. Radiographs of the spine showed a radiopaque irregular line ventrally in the vertebral canal dorsal to vertebral bodies C3-C5. In this area, magnetic resonance imaging revealed an intradural extramedullary/extradural lesion compressing the spinal cord. The spinal cord was surgically decompressed. The cause of the spinal cord compression was dural ossification, a diagnosis confirmed by histopathological examination of the surgically dissected sample of dura mater. The cat gradually improved after the procedure and was ambulating better than prior to the surgery. The cat’s locomotion later worsened again due to ossified plaques in the dura causing spinal cord compression on the same cervical area as before. Oral prednisolone treatment provided temporary remission. Ten months after surgery, the cat was euthanized due to severe worsening of gait abnormalities, non-ambulatory tetraparesis. Necropsy confirmed spinal cord compression and secondary degenerative changes in the spinal cord on cervical and lumbar areas caused by dural ossification. To our knowledge, this is the first report of spinal dural ossification in a cat. The reported cat showed neurological signs associated with these dural changes. Dural ossification should be considered in the differential diagnosis of compressive spinal cord disorders in cats.