A potential mechanism of dural ossification in ossification of ligamentum flavum

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

BACKGROUND CONTEXT

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

PURPOSE

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

STUDY DESIGN

A retrospective observational study.

PATIENT SAMPLE

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

OUTCOME MEASURES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

Background

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

Methods

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

Results

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

Conclusion

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

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

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

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.

Value of Additional Instrumented Fusion in the Treatment of Thoracic Ossification of the Ligamentum Flavum

Objective

The ossification of the ligamentum flavum (OLF) is one of the major causes of thoracic myelopathy. Surgical decompression with or without instrumented fusion is the mainstay of treatment. However, few studies have reported on the added effect of instrumented fusion. The objective of this study was to compare clinical and radiological outcomes between surgical decompression without instrumented fusion (D-group) and that with instrumented fusion (F-group).

Methods

A retrospective review was performed on 28 patients (D-group, n=17; F-group, n=11) with thoracic myelopathy due to OLF. The clinical parameters compared included scores of the Japanese Orthopedic Association (JOA), the Visual analogue scale of the back and leg (VAS-B and VAS-L), and the Korean version of the Oswestry disability index (K-ODI). Radiological parameters included the sagittal vertical axis (SVA), the pelvic tilt (PT), the sacral slope (SS), the thoracic kyphosis angle (TKA), the segmental kyphosis angle (SKA) at the operated level, and the lumbar lordosis angle (LLA; a negative value implying lordosis). These parameters were measured preoperatively, 1 year postoperatively, and 2 years postoperatively, and were compared with a linear mixed model.

Results

After surgery, all clinical parameters were significantly improved in both groups, while VAS-L was more improved in the F-group than in the D-group (-3.4±2.5 vs. -1.3±2.2, p=0.008). Radiological outcomes were significantly different in terms of changes in TKA, SKA, and LLA. Changes in TKA, SKA, and LLA were 2.3°±4.7°, -0.1°±1.4°, and -1.3°±5.6° in the F-group, which were significantly lower than 6.8°±6.1°, 3.0°±2.8°, and 2.2°±5.3° in the D-group, respectively (p=0.013, p<0.0001, and p=0.037). Symptomatic recurrence of OLF occurred in one patient of the D-group at postoperative 24 months.

Conclusion

Clinical improvement was achieved after decompression surgery for OLF regardless of whether instrumented fusion was added. However, adding instrumented fusion resulted in better outcomes in terms of lessening the progression of local and regional kyphosis and improving leg pain. Decompression with instrumented fusion may be a better surgical option for thoracic OLF.

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.

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.

Full-endoscopic decompression for thoracic myelopathy caused by ossification of the ligamentum flavum: patient series

BACKGROUND

This study aimed to describe the least invasive surgical technique of endoscopic decompression for thoracic myelopathy caused by ossification of the ligamentum flavum (OLF) and to review the literature available on the diagnosis and treatment of OLF.

OBSERVATIONS

The mean age of the patients was 51.2 (range, 40–62) years, and the mean preoperative, 2-week postoperative, and last follow-up modified Japanese Orthopaedic Association scores were 6.6 (range, 4–10), 9.6 (range, 7–11), and 13 (range, 10–14), respectively. All patients were discharged within 48 hours after the surgery. The mean follow-up period was 13.2 (range, 7–18) months. No complication was found perioperatively, and none of the patients had postoperative instability during the follow-up period.

LESSONS

Based on this clinical case series and literature review, the authors conclude that endoscopic decompression surgery is feasible and effective for managing thoracic myelopathy caused by OLF while minimizing surrounding tissue damage. Additionally, it enables shorter periods of hospital stay.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Bilateral translaminar osseous-channel assisted percutaneous full-endoscopic ligamentectomy decompression for thoracic myelopathy due to ossification of the ligamentum flavum: a technical note

Introduction

A variety of surgical procedures have been introduced to treat patients with thoracic myelopathy (TM) caused by ossification of the ligamentum flavum (OLF). However, they are accompanied by significant trauma and risk, and their surgical outcomes are not always satisfactory.

Aim

To describe a bilateral translaminar osseous-channel assisted posterior percutaneous full-endoscopic ligamentectomy decompression (p-PELD) technique as a novel minimally invasive procedure for treating patients with TM due to OLF.

Material and methods

A 51-year-old female patient with persistent thoracolumbar back pain and progressive numbness in the bilateral lower extremities for 2 years underwent percutaneous vertebroplasty (PVP) for T11 osteoporotic compression fractures (OCF) in a regional hospital one week prior to hospitalization. TM caused by canal stenosis and dorsal spinal cord compression at T10/11 secondary to OLF and an OCF at T11 were diagnosed based on clinical presentations and radiologic examinations. After bilateral p-PELD for TM was performed at T10/11, the result was confirmed based on postoperative radiographic and clinical results.

Results

The bilateral OLF was completely removed by the p-PELD technique. No complications were encountered, and her symptoms were sufficiently improved after surgery. The VAS score was 6 points preoperatively and decreased to 0 points at the last follow-up (24 months). The modified Japanese Orthopaedic Association (mJOA) score improved from 2 points preoperatively to 10 points at the final follow-up.

Conclusions

As a minimally invasive technique, the bilateral translaminar osseous-channel assisted p-PELD procedure provided precise and sufficient decompression for the treatment of OLF-related TM.

Cranial Osteopathy: Obscurantism and Enlightenment

The application of cranial osteopathic manipulative medicine (OMM) is always controversial in the literature. Primary respiration related to the movement of spheno-basilar synchondrosis in the adult goes against the knowledge of complete ossification that occurs at this articulation after the pubertal phase. The idea that the operator's hands can communicate with the meninges is difficult to accept. The anatomy shows us that the fascial system involves the meninges and that from the microcellular point of view there are no layers that divide one tissue from another. The backing of new sciences, such as quantum physics, suggest that cranial palpation allows the osteopath to come into contact with the meninges. Recent scientific evidence shows that meningeal afferents can affect extracranial areas and that the pericranial musculature itself is able to influence these afferents. The article highlights some reflections in support of cranial osteopathy, based on scientific information that could help the osteopath to improve clinical work.

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.

Clinical relation among dural adhesion, dural ossification, and dural laceration in the removal of ossification of the ligamentum flavum

BACKGROUND CONTEXT

Dural laceration frequently occurs during surgery in patients with ossification of the ligamentum flavum (OLF), mainly because of dural adhesion (DA) and dural ossification (DO) between the ligamentum flavum and the dura mater. However, the radiological predictive factors of DA in OLF have rarely been reported.

PURPOSE

The objective of this study was to determine the preoperative radiological signs for predicting intraoperative DA in OLF by using preoperative magnetic resonance imaging (MRI) and computed tomography (CT).

STUDY DESIGN

This is a retrospective study.

PATIENT SAMPLE

This study included 182 patients who underwent decompressive laminectomy and OLF removal from 2005 to 2014.

OUTCOME MEASURE

Demographic data, preoperative neurologic status, surgical procedure and results, and intraoperative and postoperative complications were analyzed. Clinical outcome was assessed with the Japanese Orthopaedic Association score.

MATERIALS AND METHODS

Depending on the morphologic appearance of OLF in preoperative radiographs, we aimed to investigate the prevalence of intraoperative DA and DO. We used the following factors of representative classifications: (1) surface appearance, (2) "double-layer" or "tram-track" sign, (3) cross-sectional area of the stenosed level, (4) Sato classification as axial classification, (5) Kuh classification as sagittal classification, and (6) high-signal-intensity change on T₂-weighted MRI.

RESULTS

Intraoperative evidence of DA was observed in 52 patients (29%), and DO was observed in 23 patients (13%). Twenty-seven patients (15%) had dural laceration during surgery. Statistically, DA was closely associated with the non-uniform type of surface appearance (odds ratio 5.396, p=.001) and with the presence of either a double-layer sign or a tram-track sign (odds ratio 11.525, p<.001). In the preoperative CT and MRI, 21 out of 23 patients with DO showed a "double-layer sign" or a "tram-track sign."

CONCLUSIONS

This study identified two predictive factors of DA in OLF, which were the non-uniform surface appearance and the presence of a double-layer sign or a tram-track sign. The presence of DO in OLF was closely associated with a double-layer sign or a tram-track sign in the preoperative radiological images.

Risk Factors and Management of Dural Defects in Anterior Surgery for Cervical Ossification of the Posterior Longitudinal Ligament

OBJECTIVE

To investigate risk factors and outcomes and to develop a cogent perioperative management algorithm for dural defects (DDs) in anterior surgery for cervical ossification of the posterior longitudinal ligament (OPLL).

METHODS

Ninety OPLL patients who had undergone anterior cervical decompression between January 2014 and December 2016 were reviewed. DDs occurred in 12 patients. Demographic, clinical, and radiologic data; intraoperative and postoperative management; and complications were analyzed. Risk factors for DDs were assessed with multivariate analysis. A treatment algorithm was identified based on these findings and our experience.

RESULTS

The prevalence of DDs was 13.3% (12/90). Univariate and multivariate analyses showed that the ratio of OPLL base to spinal canal (odds ratio [OR] 1.09, P = 0.012), kyphotic cervical alignment with thick OPLL masses (OR 9.44, P = 0.026), and lateral, curved, and irregular OPLL masses (OR 8.28, P = 0.037) could be risk factors for DDs. DDs were repaired intraoperatively with onlay grafts, and lumbar drains were placed in all DD patients. The treatment was successful in all DD patients, and outcome measures did not differ between the DD and no DD groups. No patient had experienced complications associated with DDs and CSF leaks at the final follow-up visit.

CONCLUSIONS

Patients with broad-based OPLL, kyphotic cervical alignment with thick OPLL masses, and lateral, curved, and irregular OPLL masses have a higher risk of DD in anterior surgery for OPLL. Intraoperative primary repair with onlay grafts combined with early lumbar drains is a simple, safe, and effective strategy for DDs. The outlook for the long-term sequelae of DDs is optimistic if they are managed adequately.

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.

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.