Surgical treatment of 40 patients with thoracic ossification of the ligamentum flavum

Prevalence, Radiological, and Pathological Findings of Ossification and Calcification of the Lumbar Spinal Ligamentum Flavum: A Comparative Study with Thoracic Lesions

This study aimed to determine the prevalence of lumbar ligamentum flavum lesions and identify correlations between radiological and pathological findings. We conducted an observational cross-sectional study of 349 patients (lumbar: n = 296, thoracic: n = 39, lumbar and thoracic: n = 14, mean age: 69 ± 12 years, male: 74%) who underwent posterior surgery for thoracolumbar spinal canal stenosis between January 2008 and April 2023 at our hospital.Computed tomography (CT) revealed that the prevalence of ligamentum flavum lesions defined as a high-density area with a CT value of 200 Hounsfield Unit or higher in the lumbar and thoracic spine was 47% (147/310) and 85% (45/53), respectively. CT showed that most patients had radiologically suspected ossification in the lumbar (90%) and thoracic spine (98%) than radiologically suspected calcification. Lumbar lesions were thinner than the thoracic lesions (2.5 vs 3.7 mm, p < 0.01). Pathological examinations were performed in specimens collected from 34 cases (lumbar: n = 13, thoracic: n = 21), and ossification was found in 62% (8/13) and 95% (20/21) of lumbar and thoracic lesions (p = 0.02), respectively. Lastly, ossification was confirmed pathologically in 72% (8/11) and 95% (19/20) of lumbar and thoracic lesions that showed ossification on imaging (p = 0.13), respectively. The literature review revealed that the prevalence of the lumbar ligamentum flavum lesions varied from 1.5 to 35% and the patient population was mostly asymptomatic.Collectively, we found that the prevalence of lumbar ligamentum flavum lesions in symptomatic patients was greater than previously reported. Histologically confirmed ossification was less common in lumbar lesions than in thoracic lesions.

PTGR1 is involved in cell proliferation in thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is a heterotopic ossification of spinal ligaments, leading to serious myelopathy. TOLF underlying mechanisms are not well understood. Our iTRAQ analysis have identified ten inflammatory factors related to TOLF, including l. We found that PTGR1 expressions increased in TOLF by RT-PCR and western blot in this study. Both cell proliferation and differentiation are important for the process of bone formation. In our previous study, we demonstrated that TOLF primary cells grew faster than control cells. It was reported that knockdown of PTGR1 inhibited cell proliferation. We hypothesize that PTGR1 may participate in cell proliferation in TOLF. To test this hypothesis, TOLF primary cells were treated for 24h with PTGR1. We observed that PTGR1 increased cell proliferation. The effect of PTGR1 on cell proliferation related genes was examined in TOLF primary cells. Our results showed that PTGR1 was able to activate expressions of c-Myc and CyclinD1. Moreover, blocking JNK pathway by selective JNK inhibitor SP600125 eliminated the positive effect of PTGR1 on c-Myc expression, indicating that PTGR1 activated the expression of c-Myc via JNK pathway. Our new findings suggest that PTGR1 is involved in cell proliferation of TOLF.

Prevalence and distribution of ossification of the ligamenta flava in a 16th-18th century skeletal population sample from Poland

OBJECTIVE

This study aimed to determine the prevalence of the ossification of the ligamenta flava (OLF) among skeletal remains from Poland.

MATERIALS AND METHODS

124 skeletons aged 25 years and older were analyzed. The presence and size of OLF were observed macroscopically. OLF was recorded at the cranial and caudal attachment sites of each vertebra. The following factors were analyzed: age at death, sex, and presence of other spondyloarthropathies.

RESULTS

The crude prevalence of OLF in the analyzed series was 68.55 %. OLF was located most frequently in the lower thoracic spine. A statistically significant relationship was observed between the presence of OLF and age at death. OLF coincided with degenerative spondyloarthropathies of the thoracolumbar spine.

CONCLUSIONS

The results of this study indicate that OLF was not a rare condition in past populations of European ancestry. Analysis of OLF prevalence in skeletal materials can contribute to reconstruction of the conditions and lifestyles of past people.

SIGNIFICANCE

This study shed new light on the prevalence of OLF and provides information on the variability of OLF in past European populations. The evaluation of the prevalence of OLF represents an important contribution to the field of paleopathology in understanding disease changes in prehistoric and historic human populations.

LIMITATIONS

The analyzed material came from unknown populations without demographic data. Sex and age at death were assessed using standard anthropological methods.

SUGGESTIONS FOR FURTHER RESEARCH

It is important to understand the influence of sociocultural factors and physical activity patterns on the development of OLF.

Navigation-Assisted Micro-Window Excision of Thoracic Ossification of Ligamentum Flavum (Mishima Surgery) in Professional Baseball Pitchers: A Case Report and Technical Note

Background and Objectives: Thoracic ossification of the ligamentum flavum (OLF) often causes myelopathy and/or radiculopathy. The disease is frequently observed in East Asian populations. Although thoracic OLF in young athletes who have underwent decompression surgery has been reported, the removal of posterior spinal bony elements and ligamentous complex may often cause postoperative thoracolumbar instability. We established a novel surgical technique that preserves the posterior spinal elements, including the spinous processes, facet joints, and supraspinous and interspinous ligaments for thoracic OLF. This is the first case report to describe a navigation-assisted micro-window excision of thoracic OLF. Case: A 32-year-old male right-handed professional baseball pitcher with significant weakness and numbness in the left leg was referred to our hospital. The patient was diagnosed with thoracic OLF at T10-11 based on radiographic and magnetic resonance images in August 2022. After exposure of the left T10-11 laminae via a small unilateral incision, the location of T10-11 OLF was detected over the lamina by O-arm navigation. Then, the micro-window was made directly above the OLF using a navigated air drill, and the OLF was removed on the ipsilateral side. The contralateral side of OLF was also resected through the same micro-window, achieving complete spinal cord decompression. Results: The next day of the surgery, his leg weakness and numbness were significantly improved. Six weeks after the surgery, he started pitching. Three months after surgery, his symptoms had gone completely, and he pitched from the mound. Approximately 6 months after surgery, he successfully pitched in a professional baseball game. Conclusions: A navigation-assisted micro-window excision of thoracic OLF effectively preserved the spinal posterior bony elements and ligamentous complex. However, long-term clinical outcomes should be evaluated in future studies.

Piezo1 involves in intracellular osteogenic transformation signal to promote the ossification of ligamentum flavum

Ectopic osteogenesis refers to the occurrence of osteoblasts in soft tissues other than bone tissue and the formation of bone tissue. The ligamentum flavum is an essential connecting structure between adjacent vertebral lamina, which participates in the formation of the vertebral canal's posterior wall and maintains the vertebral body's stability. Ossification of the ligamentum flavum (OLF) is one of the manifestations of systemic ossification of the spinal ligaments and one of the degenerative diseases related to the spine. However, there is a lack of research on the expression and biological function of Piezo1 in ligamentum flavum. Whether Piezo1 participates in the development of OLF is still unclear. The FX-5000C cell or tissue pressure culture and real-time observation and analysis system was applied to stretch ligamentum flavum cells to detect the expression of mechanical stress channel and osteogenic markers after the effect of different stretching durations. The results showed elevated expression of mechanical stress channel Piezo1 and osteogenic markers with the effect of tensile time duration. In conclusion, Piezo1 involves in intracellular osteogenic transformation signal to promote the ossification of ligamentum flavum. An approved explanatory model and further research will be required in the future.

Thoracic Myelopathy in Ossified Ligamentum Flavum: Surgical Management and Long-Term Outcome Following 2 Different Techniques of Surgical Decompression

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Thoracic ossified ligamentum flavum (TOLF) has been reported to present with varying degrees of neuro-deficit and multiple factors have been purported to affect its outcome. Purpose of study was to analyze factors affecting outcome and impact of ultrasonic osteotome (UO).

METHODS

We retrospectively reviewed patients treated for thoracic myelopathy secondary to OLF between 2010 and 2017. 77 patients with complete clinico-radiological records and 2 years follow-up were included. Initial 45 patients, conventional high-speed burr (HSB-group A) was used for decompression. In others, UO was used in combination with HSB (group B). Myelopathy was graded using modified Japanese orthopaedic association grading pre-operatively and each postoperative visit. At final follow-up, recovery rate was calculated. Radiological details including location, morphology, dural ossification, signal change and spinal ossifications were recorded.

RESULTS

Mean mJOA at presentation and final follow-up were 4.3±1.8 and 7.6±1.9 respectively (p = 0.001). HRR was 49.9±23 at final follow-up. A significant reduction in dural tear (12.5%; 29%) and surgical time (125.8±49.5; 189.4±52.5) were observed in group B (p = 0.00). However, there was no statistically significant difference (p = 0.18) in recovery rates between groups A (44.8±26.1) and B (52.8±24.3). Symptom duration (p = 0.00), severity of myelopathy (p = 0.04) and cord signal changes on MRI (p = 0.02) were important predictors of outcome.

CONCLUSION

Use of UO significantly reduced operative time and dural tears, although resulted in similar recovery rate as compared with HSB. Pre-operative severity of myelopathy, symptom duration and presence of cord signal change were the most significant predictors of outcome.

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 Fgroup 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.

Ossification of the Ligamentum Flavum of the Lumbar Spine

Ossification of the ligamenta flava (OLF) is a rare and likely multifactorial condition that most commonly affects the lower thoracic spine. It can result in chronic pain and neurological deficits and has a higher prevalence in men of Japanese descent. We present the case of OLF of the lumbar spine in a Caucasian man with a history of multiple sports-related injuries. To treat his severe lumbar spinal stenosis, the patient underwent endoscopic intralaminar laminotomy with partial facetectomy and complete resection of OLF with lateral recess decompression, which immediately resolved his symptoms. We noted signs of OLF based on T1 and T2 signal changes upon re-evaluation of MRI.

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.

Comparing Thoracic Extensive Laminoplasty (TELP) and Laminectomy in Treating Severe Thoracic Ligamentum Flavum Ossification: A Proposed Novel Technique and Case-Control Study

Objective

(1) To propose a novel technique named thoracic extensive laminoplasty (TELP) in curing severe thoracic ligamentum flavum ossification (STOLF) and (2) to compare outcomes between TELP and laminectomy in curing STOLF.

Methods

Cases with fused or tuberous STOLF (Sato classification) treated from Jan 2015 to Jan 2017 were reviewed and divided into the TELP group (G1) and laminectomy group (G2) according to their surgical management. Data on demographics, complications, pre- and postoperative symptoms, residual spinal canal area (RSCA-1), residual spinal cord area (RSCA-2), modified Japanese Orthopedic Association score (mJOA), and health-related quality of life (HRQOL, based on the SF-36) were collected.

Results

Fifty-nine G1 and sixty-two G2 patients were enrolled. No significant differences in demographic data or preoperative data of RSCA-1, RSCA-2, mJOA, or HRQOL were observed between the two groups (p > 0.05). Patients in G1 and G2 showed similar postoperative improvements in RSCA-1 and RSCA-2 at the final follow-up (p > 0.05). However, patients in G1 showed higher postoperative improvements in mJOA (OR = 2.706, 95% CI: 1.279~5.727, p = 0.008) at the final follow-up. Patients in G1 also showed higher postoperative improvements in HRQOL than patients in G2 (p < 0.05) at the final follow-up, and patients with more severe STOLF presented with better improvements in HRQOL in G1 (p < 0.05). Dural laceration and cerebrospinal fluid leakage were observed in seven G2 patients, and no complications were found in G1 patients after surgery.

Conclusion

TELP is a novel, effective, and safer surgical technique in treating STOLF and could be a substitute for traditional laminectomy.

Sagittal Alignment in Patients with Thoracic Myelopathy Caused by the Ossification of the Ligamentum Flavum: A Retrospective Matched Case-Control Study

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

The aim of this study was to describe and compare the sagittal spinal alignment between patients with and without the ossification of the ligamentum flavum in the thoracic spine (TOLF).

SUMMARY OF BACKGROUND DATA

Although mechanical factors play an important role in the development of TOLF, limited evidence exists on the association of sagittal spinal alignment and TOLF in the literature.

METHODS

The present study assessed the preoperative sagittal alignment parameters in consecutive patients who underwent posterior decompression for TOLF in a single institution between January 2014 and December 2019. The sagittal parameters of the patients with TOLF were compared to those of the age- and sex-matched control group with lumbar spondylosis.

RESULTS

The TOLF group (n = 43 [23 men, 20 women]), with a mean age of 69.5 (range: 41-86) years, and the control group (n = 86) were compared. The TOLF group had a significantly smaller sacral slope (27.60 ± 7.49 vs. 30.61 ± 8.15, P = 0.045) and lumbar lordosis (36.84 ± 13.63 vs. 45.08 ± 9.90, P < 0.001) and a larger pelvic incidence minus lumbar lordosis (PI-LL, 8.06 ± 15.05 vs.1.00 ± 11.34, P = 0.004) than the control group. Moreover, the thoracic kyphosis was smaller in the TOLF group, although the difference was not statistically significant (25.73 ± 11.29 vs. 28.22 ± 9.34, P = 0.187). The TOLF group had a significantly smaller slope angle at the inflection point (11.97 ± 5.85 vs. 15.78 ± 5.62, P < 0.001) and a higher tendency to have a Roussouly type 2 morphology (46.5% vs. 36.0%, P = 0.252) than the control group.

CONCLUSION

This is the first study to describe the sagittal alignment in patients with TOLF. The TOLF group showed a hypolordotic spine with a larger PI-LL mismatch compared to the age- and sex-matched control group with lumbar spondylosis.Level of Evidence: 4.

Microendoscopic Posterior Decompression for Treating Thoracic Myelopathy Caused by Ossification of the Ligamentum Flavum: Case Series

Background and Objectives: Ossification of the ligamentum flavum (OLF) is a relatively common cause of thoracic myelopathy. Surgical treatment is recommended for patients with myelopathy. Generally, open posterior decompression, with or without fusion, is selected to treat OLF. We performed minimally invasive posterior decompression using a microendoscope and investigated the efficacy of this approach in treating limited type of thoracic OLF. Materials and Methods: Microendoscopic posterior decompression was performed for 19 patients (15 men and four women) with thoracic OLF with myelopathy aged between 35 to 81 years (mean age, 61.9 years). Neurological examination and preoperative magnetic resonance imaging (MRI) and computed tomography (CT) were used to identify the location and morphology of OLF. The surgery was performed using a midline approach or a unilateral paramedian approach depending on whether the surgeon used a combination of a tubular retractor and endoscope. The numerical rating scale (NRS) and modified Japanese Orthopedic Association (mJOA) scores were compared pre- and postoperatively. Perioperative complications and the presence of other spine surgeries before and after thoracic OLF surgery were also investigated. Results: Four midline and 15 unilateral paramedian approaches were performed. The average operative time per level was 99 min, with minor blood loss. Nine patients had a history of cervical or lumbar spine surgery before or after thoracic spine surgery. The mean pre- and postoperative NRS scores were 6.6 and 5.3, respectively. The mean recovery rate as per the mJOA score was 33.1% (mean follow-up period, 17.8 months), the recovery rates were significantly different between patients who underwent thoracic spine surgery alone (50.5%) and patients who underwent additional spine surgeries (13.7%). Regarding adverse events, one patient experienced dural tear, another experienced postoperative hematoma, and one other underwent reoperation for adjacent thoracic stenosis. Conclusion: Microendoscopic posterior decompression was applicable in limited type of thoracic OLF surgery including beak-shaped type and multi vertebral levels. However, whole spine evaluation is important to avoid missing other combined stenoses that may affect outcomes.

Dynamic changes in longitudinal stretching of the spinal cord in thoracic spine: Focus on the spinal cord occupation rate of dural sac

OBJECTIVES

This study aimed to evaluate the anteroposterior diameters and cross-sectional areas of the dural sac and spinal cord in the thoracic spine, to elucidate the spinal cord occupation rate of the dural sac in these dynamic changes for each level using multidetector-row computed tomography (MDCT).

PATIENTS AND METHODS

Fifty patients with cervical or lumbar spinal disease were prospectively enrolled. After preoperative myelography, MDCT was performed at maximum passive flexion and extension. The anteroposterior diameter and cross-sectional area of the dural sac and spinal cord in the axial plane and the thoracic spinal cord length in the sagittal plane were measured. The spinal cord occupation rate in the dural sac was calculated.

RESULTS

The spinal cord occupation rate of the dural sac in anteroposterior diameter was lower on flexion than on extension, with significant differences from the T1/T2 to T11/T12 levels (p < 0.0001). The spinal cord occupation rate of the dural sac in cross-sectional area was lower on flexion than on extension, with significant differences except from T3/T4 to T6/T7 levels (p < 0.01). There was a bimodal increase in the occupation rate with elevations at the cervicothoracic junction and thoracolumbar junction. The thoracic spinal cord length on flexion was significantly longer than that on extension (p < 0.0001).

CONCLUSIONS

The spinal cord occupation rate of the dural sac was lower on flexion than on extension, despite thoracic spine being considered a rigid region. The dynamic changes in longitudinal stretching and shrinkage of the spinal cord affected the occupation rate.

Genome-wide DNA methylation profile analysis in thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) causes serious spinal canal stenosis. The underlying aetiology may relate to genetic and inflammatory factors. DNA methylation plays a critical role in osteogenesis and inflammation, whereas there is no genome‐wide DNA methylation analysis about TOLF. The two subtypes of TOLF (single‐level and multiple‐level) have distinct clinical features. Using micro‐computed tomography (micro‐CT), we showed the ossification arose from the joint between two vertebrae at one/both sides of ligament flavum. With Illumina Infinium Human Methylation 850 BeadChip arrays, genome‐wide DNA methylation profile was measured in ligament flavum of eight healthy and eight TOLF samples. Only 65 of the differentially methylated cytosine‐phosphate‐guanine dinucleotides were found in both subtype groups. Principal component analysis and heat map analysis showed a different methylation pattern in TOLF samples, and methylation patterns of two subtypes are also distinct. The Gene Ontology enrichment analysis was significantly enriched in differentiation and inflammation. Pyrosequencing analysis and quantitative real‐time polymerase chain reaction were performed to validate the arrays results and expression levels, to test six differentially methylated genes (SLC7A11, HOXA10, HOXA11AS, TNIK, homeobox transcript antisense RNA, IFITM1), using another independent samples (P < 0.05). Our findings first demonstrated an altered Genome‐wide DNA methylation profile in TOLF, and implied distinct methylated features in two subtypes.

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.

Outcomes of Surgery for Thoracic Myelopathy Owing to Thoracic Ossification of The Ligamentum Flavum in a Nationwide Multicenter Prospectively Collected Study in 223 Patients: Is Instrumented Fusion Necessary?

STUDY DESIGN

Prospectively collected, multicenter, nationwide study.

OBJECTIVE

The aim of this study was to investigate recent surgical methods and trends, outcomes, and perioperative complications in surgery for thoracic ossification of the ligamentum flavum (T-OLF).

SUMMARY OF BACKGROUND DATA

A prospective multicenter study of surgical complications and risk factors for T-OLF has not been performed, and previous multicenter retrospective studies have lacked details for these items.

METHODS

Surgical methods, pre- and postoperative thoracic myelopathy (Japanese Orthopedic Association [JOA] score), symptoms, and intraoperative neurophysiological monitoring were investigated prospectively in 223 cases. Differences in these factors between fusion and nonfusion procedures for T-OLF were examined. The minimum follow-up period was 2 years after surgery RESULTS.: The mean JOA score was 6.2 points preoperatively, and 7.9, 8.2, and 8.2 points at 6 months, 1, and 2 year postoperatively, giving mean recovery rates of 35.0%, 40.9%, and 41.4% respectively. Posterior decompression and fusion with instrumentation was performed in 109 cases (48.9%). There were 45 perioperative complications in 30 cases (13.5%), with aggravation of motor disturbance in the lower extremities being most common (4.0%, n = 9). Patients treated with fusion had a significantly higher BMI, rate of gait disturbance, ossification occupation rate of OLF at computed tomography, and intramedullary high intensity area at magnetic resonance imaging (P < 0.01). The preoperative JOA score was lower (P < 0.05) and the JOA recovery rate at 1 year after surgery was significantly higher in cases treated without fusion (44.9% vs. 37.1%, P < 0.05).

CONCLUSION

The high rate of surgery with instrumentation of 48.9% reflects the current major trend toward posterior instrumented fusion surgery for T-OLF. Fusion surgery with instrumentation may be appropriate for patients with severe OLF and preoperative myelopathy. A further prospective study of long-term outcomes is required with a focus on optimal surgical timing and the surgical procedure for T-OPLL.

LEVEL OF EVIDENCE

3.

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.

Benefits and Risks of Subsection Laminectomy with Pedicle Screw Fixation for Ossification of the Ligamentum Flavum of the Thoracic Spine: A Retrospective Study of 30 Patients

BACKGROUND This study aimed to evaluate the effectiveness of subsection laminectomy with pedicle screw fixation (SLPF) for the treatment of ossification of the ligamentum flavum of the thoracic spine. MATERIAL AND METHODS Thirty patients (age, 40-71 years) with ossification of the ligamentum flavum of the thoracic spine underwent SLPF (13 men, 17 women). Operative time, intraoperative blood loss, preoperative and postoperative change in thoracic kyphosis, and perioperative complications were recorded. The Japanese Orthopedic Association (JOA) score for severity of myelopathy and the American Spinal Injury Association (ASIA) motor and sensory impairment scale were used before and after surgery. RESULTS Mean operative time for SLPF was 208.4±38.3 min and mean intraoperative blood loss was 689.3±171.7 ml. The mean JOA score significantly increased from 5.7±1.9 before surgery to 8.8±2.2 at one month after surgery and 9.3±2.7 at the last follow-up (P<0.01). Postoperative improvement in neurological function increased by 68.3±14.4%. The postoperative ASIA grades significantly improved compared with the preoperative grades (P<0.01). The mean local Cobb angle significantly decreased from 17.8±4.3° before surgery to 15.4±3.6° at one month after surgery and 15.8±3.8° at the last follow-up (P<0.01). Three patients (10%) had operative cerebrospinal fluid (CSF) leak. Postoperatively, one patient had neurological deterioration, two patients had deep venous thrombosis (DVT), and one patient developed a wound infection. CONCLUSIONS SLPF was an effective procedure for the treatment of ossification of the ligamentum flavum of the thoracic spine.

Acute Presentation of Lumbar Spinal Stenosis Due to Ossified Ligamentum Flavum: The Possible Role of Spondylolisthesis: A Case Report

CASE

A 64-year-old woman with a history of low back pain, presented with acute gait impairment and lower limbs numbness without any history of trauma. Imaging studies revealed ossification of the ligamentum flavum (OLF) at L4-L5 and concomitant spondylolisthesis. Decompression surgery with en-bloc removal including the laminae, the ossified ligamentum flavum, and the medial facet and posterior stabilization was performed resulting in complete immediate recovery.

CONCLUSIONS

This report is the first to describe a case of an acute nontraumatic presentation of OLF associated with spondylolisthesis. OLF pathogenesis in still unknown, although several factors have been considered. According to the literature, operative treatment has demonstrated to be effective.

Ossification of the yellow ligament in the cervical spine - an unusual location

Ossification of the yellow ligament (OYL) or ligamentum flavum, usually occurs in the thoracic spine. Focal OYL occurring in the cervical spine is considered rare and is sparsely reported in the literature. We came across a 30-year-old male patient with progressive left upper limb and bilateral lower limb weakness over a period of 3 months, associated with an unsteady gait. Clinical examination revealed bilateral generalized hyper-reflexia in both upper and lower limbs, inverted supinator jerk, Hoffman’s sign and clonus. Myelopathy due to cord compression was suspected and further investigations were done. MRI and CT scans revealed a bony mass in relation to the C6 spinous process projecting anterosuperiorly and narrowing the cervical spinal canal causing cord signal changes from C4 to C6 levels. In view of the deteriorating neurological status, immediate surgery in the form of decompression and posterior stabilization from C4-C6 was performed. Patient gradually recovered after surgery and attained full functional status. We report this case considering the unusual location of OYL and its successful management.

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.

Cervical Myelopathy Secondary to Combined Ossification of Ligamentum Flavum and Posterior Longitudinal Ligament-A Case Report

In the cervical spine, the combined ossification of the ligamentum flavum (OLF) and posterior longitudinal ligament is rarely seen. Patients are usually treated with cervical laminectomy or laminoplasty with OLF resection. In most of the cases, OLF is adhered to the dura and there is a risk of dural tear or cerebrospinal fluid (CSF) leakage during its resection. In this case report, the authors present results of laminectomy with debulking instead of complete excision of OLF for spinal cord decompression in a cervical myelopathy case in which OLF was adhered to the dura. A 69-year-old man presented with insidious onset weakness in bilateral lower limbs and unsteady gait, which he had experienced 1 month. He has a history of neck pain with left upper limb radiation for the last 2 years. Magnetic resonance imaging showed C5-6 severe central canal stenosis with underlying myelomalacia. Computed tomography showed ossification posterior longitudinal ligament and OLF contributing to severe central canal stenosis at the C5-6 level. The patient underwent C4-C6 laminectomy, debulking of OLF, posterior instrumentation, and fusion with autogenous bone graft from C3 to C6. A histological specimen showed osseous tissue within the ligamentum flavum. After surgery the patient's symptoms improved and no recurrence was observed at 4 years after surgery. The symptoms of myelopathy were successfully treated with debulking instead of complete excision of OLF, thus reducing the risk of dural tear or CSF leakage.

Ossification of the Ligamentum Flavum in a Nineteenth-Century Skeletal Population Sample from Ireland: Using Bioarchaeology to Reveal a Neglected Spine Pathology

Ossification of the ligamentum flavum of the spine (OLF) is rarely reported in individuals of European ancestry. It has, however, been observed in archaeological skeletons from Europe. The aim of this study was to revisit OLF rates, utilising a mid-nineteenth-century skeletal sample from Ireland. The hypothesis was that the OLF prevalence rate was similar to studies on non-Europeans. Spines from 345 individuals were analysed, and the extent of OLF recorded on the cranial and caudal attachment sites of each vertebra using the following classification system: Grade 0 (no change); Grade 1 (<2 mm); Grade 2 (2–4 mm); Grade 3 (≥4 mm). OLF was observed at prevalence rates of 83.6%. There was no disparity in prevalence based on sex, except for individuals aged 36–45 years at death in which the male rate was higher. Advancing age was a determining factor in the OLF occurrence with an onset in young adulthood (18–25 years), and most severe grades occurring over the age of 25 years. OLF coincides with spinal osteoarthritis, spondylosis deformans and Schmorl’s nodes in both sexes, and with intervertebral osteochondrosis in females. The results of this study indicate that OLF is likely to be an understudied rather than rare condition in European populations.

Clinical and radiological features of spinal extradural arachnoid cysts: Valve-like mechanism involving the nerve root fiber as a possible cause of cyst expansion

BACKGROUND

Although a valve-like mechanism has been proposed for expansion of spinal extradural arachnoid cysts (SEACs), the detailed mechanism remains unclear. Moreover, closure of the communication site is essential during surgery, but the method to identify the communication site remains unclear. The aim of this study was to determine the detailed mechanism of expanding SEACs through retrospective analysis of SEAC cases undergoing surgery and to elucidate the characteristics of the communication sites.

METHODS

The authors retrospectively evaluated 12 patients with SEACs who underwent surgery between 2000 and 2014 and analyzed their perioperative findings.

RESULTS

Dural defects were detected in 11 out of 12 patients, and a valve-like mechanism was observed in 7 patients, wherein a nerve root fiber moved back and forth through the dural defect along with the flow of cerebrospinal fluid (CSF) between the intradural space and the extradural arachnoid cysts. The dural defect was located at the thoracolumbar junction in 7 patients, below the distal end of the bridging ossification in 2, at the level of vertebral wedge deformity in 2, and at the level of disc herniation in 1.

CONCLUSIONS

A valve-like mechanism was observed in 7 of the 12 patients, which suggests that it could serve as a mechanism of SEAC formation. The communication sites were variously located at the end of ossification in patients with diffuse idiopathic skeletal hyperostosis (DISH), wedge deformity of the vertebral body, or disc herniation, indicating the contribution of mechanical stress to SEAC formation.

Prevalence and related clinical factors of thoracic ossification of the ligamentum flavum-a computed tomography-based cross-sectional study

BACKGROUND TEXT

Thoracic ossification of the ligamentum flavum (TOLF) is an uncommon pathology, but it may sometimes grow and cause serious neurologic manifestations. Little has been demonstrated yet about the epidemiology and etiology of TOLF.

PURPOSE

This study aimed to estimate the prevalence and clinical characteristics of TOLF.

DESIGN

A cross-sectional study was carried out.

PATIENT SAMPLE

All individuals who had undergone chest computed tomography (CT) for the evaluation of pulmonary disease or for medical examination for 1 year at our institute comprised the patient sample.

OUTCOME MEASURES

Presence of TOLF and the association of these findings with thoracic kyphosis (TK), ossification of posterior longitudinal ligament (OPLL), space available for cord (SAC), age, gender, body mass index (BMI), and diabetes were the outcome measures.

METHODS

Prevalence and distribution of TOLF, TK, and concurrent OPLL were analyzed on CT scans. Through reviews of their medical records, clinical characteristics including age, gender, BMI, and diabetes were investigated. Logistic regression analysis was performed to determine the risk factors of TOLF.

RESULTS

A total of 4,999 individuals (2,929 men and 2,070 women) were included for the analysis. Thoracic ossification of the ligamentum flavum was found in 1,090 individuals (674 men and 416 women. A single TOLF lesion was noted in 592 individuals and multiple lesions were noted in 498 individuals. The most commonly involved level was T10-T11. Distribution of TOLF showed two peaks: and the highest peak was at the lower thoracic spine (T10-12) and the second highest peak was at T3-T5. Thoracic kyphosis was 31.5°±9.5° in the TOLF group and 29.7°±8.9° in the non-TOLF group (p<.001). Space available for cord/anteroposterior canal diameter ratio in TOLF level was 0.882. Logistic regression analysis showed that gender and TK were significantly associated with TOLF.

CONCLUSIONS

Incidental TOLF was found in 21.8% of the study cohort. Gender and TK were related to TOLF.

High thoracic ossification of ligamentum flavum causing partial Horner syndrome

We report a case of high thoracic ossification of the ligamentum flavum (OLF) causing a partial Horner's syndrome. A 57-year-old man developed a walking disorder, as well as right-sided miosis and anhidrosis. Magnetic resonance imaging demonstrated a spinal cord compressing T2-T3 OLF. The patient improved after surgery.

Transforaminal en bloc resection for the treatment of thoracic ossification of the ligamentum flavum: Retrospective cohort study

BACKGROUND

Our purpose is to introduce transforaminal en bloc resection for the treatment of thoracic ossification of ligamentum flavum, and report outcomes of the procedure.

PATIENTS AND METHODS

The record of patients with symptomatic thoracic ossification of the ligamentum flavum who received transforaminal en block resection from October 2010 to September 2014 were retrospectively reviewed. Outcomes were Japanese Orthopaedic Association (JOA) lower extremity motor dysfunction and sphincter dysfunction scores.

RESULTS

Seventeen patients (10 males, 7 females) with a median age of 60 years were included in the analysis. Surgery was performed as planned without complications in all patients. One segment decompression was performed in 1 case, 2 segment in 9 cases, 3 segment in 3 cases, and 4 segment in 4 cases. The median lower extremity motor dysfunction score was significantly higher at 2 weeks, 3 months, and 6 months postoperatively, and the end of follow-up, than before surgery (median score: 2, 2, 3, 3, respective, vs. 1, all, p ≤ 0.008). There were no significant differences in JOA sphincter dysfunction score between the different time points.

CONCLUSION

Transforaminal en bloc resection is a safe and effective method for the treatment of thoracic ossification of the ligamentum flavum.

Fifty top-cited spine articles from mainland China: A citation analysis

Objective To identify the 50 top-cited spine articles from mainland China and to analyze their main characteristics. Methods Web of Science was used to identify the 50 top-cited spine articles from mainland China in 27 spine-related journals. The title, year of publication, number of citations, journal, anatomic focus, subspecialty, evidence level, city, institution and author were recorded. Results The top 50 articles had 29-122 citations and were published in 11 English-language journals; most (32) were published in the 2000s. The journal Spine had the largest number of articles and The Lancet had the highest impact factor. The lumber spine was the most discussed anatomic area (18). Degenerative spine disease was the most common subspecialty topic (22). Most articles were clinical studies (29); the others were basic research (21). Level IV was the most common evidence level (17). Conclusions This list indicates the most influential articles from mainland China in the global spine research community. Identification of these articles provides insights into the trends in spine care in mainland China and the historical contributions of researchers from mainland China to the international spine research field.

A systematic review of complications in thoracic spine surgery for ossification of ligamentum flavum

STUDY DESIGN

Systematic review.

OBJECTIVES

The aim of this systematic review is to summarize the incidence of complications, to relate complication incidence to procedures performed, to assess the impact of the year of study publication and follow-up duration on complication incidence.

METHODS

The authors conducted the Cochrane Central Register of Controlled Trials, PubMed, and EMBASE searches for relevant literatures. The incidence of complications was summarized. Correlation of the incidence with year of study publications, follow-up duration, and the surgical outcome was statistically evaluated.

RESULTS

A total of 16 studies met our inclusion criteria, including 475 patients. All of these studies were retrospective case series. The mean age of patients ranged from 55 to 64 years. Average follow-up duration ranged from 26 to 65 months. Partial patients in four studies underwent surgeries and reserved posterior structure of the spinal canal. The others underwent operations removing posterior structure of spinal canal. The mean recovery rate from each individual study varied between 31 and 68% and the pooled neurologic function recovery rate was 53% (95% CI: 43-62%). The mean complication rate was 24%. Cerebrospinal fluid leakage was the most reported postoperative complication (19%), then neurologic deterioration (5%). Other complications included local infections, wound dehiscence, increased kyphotic deformity, an hematoma.

CONCLUSIONS

Operations removing posterior structure of spinal canal are the main technique to decompress spinal cord. Cerebrospinal fluid leakage and postoperative neurologic deterioration were the most reported complications.

iTRAQ quantitative proteomic study in patients with thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is a unique disease with ectopic ossification, and is a major cause of thoracic spinal stenosis and myelopathy. However, the underlying etiology remains largely unknown. In this study, the ligamentum flavum was systematically analyzed in TOLF patients by using comprehensive iTRAQ labeled quantitative proteomics. Among 1285 detected proteins, there were 282 proteins identified to be differentially expressed. The Gene Ontology (GO) analysis regarding functional annotation of proteins consists of the following three aspects: the biological process, the molecular function, and the cellular components. The function clustering analysis revealed that ten of the above proteins are related to inflammation, such as tumor necrosis factor (TNF). This finding was subsequently validated by ELISA, which indicated that serum TNF-α of TOLF patients was significantly higher compared with the control group. To address the effect of TNF-α on ossification-related gene expression, we purified and cultured primary cells from thoracic ligamentum flavum of patients with TOLF. TNF-α was then used to stimulate cells. RNA was isolated and analyzed by RT-PCR. Our results showed that TNF-α was able to induce the expressions of osteoblast-specific transcription factor Osterix (Osx) in ligamentum flavum cells, suggesting that it can promote osteoblast differentiation. In addition, as the Osx downstream osteoblast genes OCN and ALP were also activated by TNF-α. This is the first proteomic study to identify inflammation factors such as TNF-α involved in ossified ligamentum flavum in TOLF, which may contribute to a better understanding of the cause of TOLF.

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.

The involvement and possible mechanism of pro-inflammatory tumor necrosis factor alpha (TNF-α) in thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF) is characterized by ectopic bone formation in the ligamentum flavum and is considered to be a leading cause of thoracic spinal canal stenosis and myelopathy. However, the underlying etiology is not well understood. An iTRAQ proteomics was used to reveal the involvement of inflammation factors in TOLF. TNF-α is a pro-inflammatory cytokine implicated in the pathogenesis of many human diseases. Protein profiling analysis showed that the protein level of TNF-α increased in the ossified ligamentum flavum of TOLF, which was confirmed by western blot. The effects of TNF-α on primary ligamentum flavum cells was examined. Cell proliferation assay demonstrated that primary cells from the ossified ligamentum flavum of TOLF grew faster than the control. Flow cytometry assay indicated that the proportions of cells in S phase of cell cycle of primary cells increased after TNF-α stimulation. To address the effect of TNF-α on gene expression, primary cells were derived from ligamentum flavum of TOLF patients. Culture cells were stimulated by TNF-α. RNA was isolated and analyzed by quantitative RT-PCR. G1/S-specific proteins cyclin D1 and c-Myc were upregulated after TNF-α stimulation. On the other hand, osteoblast differentiation related genes such as Bmp2 and Osterix (Osx) were upregulated in the presence of TNF-α. TNF-α activated Osx expression in a dose-dependent manner. Interestingly, a specific mitogen-activated protein kinase ERK inhibitor U0126, but not JNK kinase inhibitor SP600125, abrogated TNF-α activation of Osx expression. This suggests that TNF-α activates Osx expression through the mitogen-activated protein kinase ERK pathway. Taken together, we provide the evidence to support that TNF-α involves in TOLF probably through regulating cell proliferation via cyclin D1 and c-Myc, and promoting osteoblast differentiation via Osx.

A case report of atypical long segmental thoracic hypertrophic pachymeningitis with ossification of ligamentum flavum and literature review

BACKGROUND

Thoracic spinal stenosis caused by ossification of ligamentum flavum (OLF) is frequently seen, but long segmental thoracic spinal cord compressed by consequent thickened ligament posteriorly was rarely reported.

OBJECT

To report a case of thoracic spinal cord compression caused by atypical long segmental thoracic hypertrophic pachymeningitis (HP) with OLF.

METHODS

A 55-year-old woman presenting with weakness and numbness in lower extremities was admitted to our department. Combined with physical examination and MRI results, diagnosis of HP with OLF was considered. Due to progressive neurological symptoms, thoracic decompression with internal fixation was performed.

RESULTS

The patient felt a reduced numbness and improvement in motor functions 5 days after surgery. Pathological examination suggested the diagnosis of HP with OLF.

CONCLUSIONS

HP is a rare condition characterized as thickening and enhancement of the dura mater on contrast-enhanced MRI and chronic inflammatory hyperplasia changes on biopsy. A case of atypical HP complicated with OLF is described. Chondrocytes infiltration in histological examination indicates the potential of ossification in HP.

Surgical Technique for Decompression of Severe Thoracic Myelopathy due to Tuberous Ossification of Ligamentum Flavum

STUDY DESIGN

Retrospective review.

OBJECTIVE

To describe a safe surgical procedure, en bloc resection of the posterior wall of the thoracic canal, for the decompression of severe thoracic myelopathy caused by tuberous ossification of the ligamentum flavum (OLF).

SUMMARY OF BACKGROUND DATA

OLF has been widely recognized as a cause of thoracic myelopathy in East Asia. Surgical decompression of thoracic myelopathy caused by OLF is technically demanding. Although several surgical decompression procedures have been described, acute neurological deterioration is common.

MATERIALS AND METHODS

Eighteen patients with severe thoracic myelopathy caused by tuberous OLF underwent posterior decompression via segmental en bloc resection of the posterior wall of the thoracic canal. The ossified ligamentum flavum, laminae, and partial facet joints of each segment were resected en bloc. Ossified dura mater was removed if present. Posterior fixation with pedicle screws was followed by lateral bone graft fusion.

RESULTS

The mean preoperative modified Japanese Orthopaedic Association score (total score, 11) was 4.1 (range, 2-5). Postoperatively, no neurological deterioration occurred, and all patients improved clinically. With an average follow-up of 31.2 months (range, 24-42 mo), the average modified Japanese Orthopaedic Association score was 7.8 (range, 6-10), representing a 2- to 5-point improvement. The average improvement rate was 55.2% (range, 33.3%-83.3%). Most patients were functionally independent at the last follow-up. Forty ossified segments were resected. The average time required for the resection of 1 segment was 77 minutes. Intraoperatively, dural ossification was noted in 11 patients. Complete resection was performed in all patients. Cerebrospinal fluid leakage occurred in 5 patients.

CONCLUSION

Segmental en bloc resection of the posterior wall of the thoracic canal is a safe and effective alternative for OLF-related severe thoracic myelopathy.

Genetic differences in osteogenic differentiation potency in the thoracic ossification of the ligamentum flavum under cyclic mechanical stress

Mechanical stress and genetic factors play important roles in the occurrence of thoracic ossification of ligament flavum (TOLF), which can occur at one, two, or multiple levels of the spine. It is unclear whether single- and multiple-level TOLF differ in terms of osteogenic differentiation potency and osteogenesis-related gene expression under cyclic mechanical stress. This was addressed in the present study using patients with non‑TOLF and single‑ and multiple‑level TOLF (n=8 per group). Primary ligament cells were cultured and osteogenesis was induced by application of cyclic mechanical stress. Osteogenic differentiation was assessed by evaluating alkaline phosphatase (ALP) activity and the mRNA and protein expression of osteogenesis‑related genes, including ALP, bone morphogenetic protein 2 (BMP2), Runt‑related transcription factor‑2 (Runx‑2), osterix, osteopontin (OPN) and osteocalcin. The application of cyclic mechanical stress resulted in higher ALP activity in the multiple‑level than in the single‑level TOLF group, whereas no changes were observed in the non‑TOLF group. The ALP, BMP2, OPN and osterix mRNA levels were higher in the multiple‑level as compared to the single‑level TOLF group, and the levels of all osteogenesis-related genes, apart from Runx2, were higher in the multiple‑level as compared to the non‑TOLF group. The osterix and ALP protein levels were higher in the multiple‑level TOLF group than in the other 2 groups, and were increased with the longer duration of stress. These results highlight the differences in osteogenic differentiation potency between single‑ and multiple‑level TOLF that may be related to the different pathogenesis and genetic background.

Extensive calcification of the ligamentum flavum causing cervical myelopathy in a Caucasian woman

Calcification of the ligamentum flavum (CLF) can cause myelopathy due to spinal cord compression. Only several cases in Caucasian patients have been described. Neurological deterioration can only be stopped by surgical decompression. We report a 63-year-old Caucasian woman presenting with progressive pins-and-needles sensations in both hands, worsened by painful paresthesia in both lower extremities. MRI showed a dorsal compressive mass extending from C2 to Th3 vertebrae with myelopathy at the level of C6. A laminectomy was performed, which improved clinical symptoms. Histological examination showed CLF. Early recognition of CLF and early spinal cord decompression are needed to improve neurological outcome.

Predictors of surgical outcome in thoracic ossification of the ligamentum flavum: focusing on the quantitative signal intensity

The association between intramedullary increased signal intensity (ISI) on T2-weighted magnetic resonance imaging (MRI) and surgical outcome in thoracic ossification of the ligamentum flavum (OLF) remains controversial. We aimed to determine the impact of signal change ratio (SCR) on thoracic OLF surgical outcomes. We retrospectively reviewed 96 cases of thoracic OLF surgery and investigated myelopathy severity, symptom duration, MRI and computed tomographic findings, surgical technique and postoperative recoveries. Surgical outcomes were evaluated according to the modified Japanese Orthopaedic Association (JOA) score and recovery rate. JOA recovery rate <50% was defined as a poor surgical outcome. By multivariate logistic regression analysis, we identified risk factors associated with surgical outcomes. Forty patients (41.7%) had a recovery rate of <50%. In receiver operating characteristic (ROC) curves, the optimal preoperative SCR cutoff value as a predictor of poor surgical outcome was 1.54. Multivariate logistic regression analysis revealed that a preoperative SCR ≥1.54 and symptom duration >12 months were significant risk factors for a poor surgical outcome. These findings suggest that preoperative SCR and duration of symptoms were significant risk factors of surgical outcome for patients with thoracic OLF. Patients with preoperative SCR ≥1.54 can experience poor postoperative recovery.

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.

Spinal Cord Kinking in Thoracic Myelopathy Caused by Ossification of the Ligamentum Flavum

Background:

Ossification of the ligamentum flavum (OLF) is being increasingly recognized as a cause of thoracic myelopathy. This study was to describe a rare clinical entity of spinal cord kinking (SK) in thoracic myelopathy secondary to OLF.

Methods:

The data of 95 patients with thoracic myelopathy secondary to OLF were analyzed retrospectively. The incidence and location of SK were determined using preoperative magnetic resonance imaging (MRI). The clinical presentation and radiological characteristics in patients with SK were analyzed. Posterior en bloc laminectomy with OLF was performed, and the surgical results were evaluated.

Results:

SK was found in seven patients (7.4%) based on preoperative MRI. The patients included one male and six females with an average age of 55.6 years (range, 48–64 years). Five patients presented with radiculomyelopathy and two presented with typical thoracic myelopathy of spastic paraparesis. In all cases, the kinking was located just above the end of the spinal cord where the conus medullaris (CM) was compressed by the OLF. The degree of SK varied from mild to severe. The tip of the CM was located between the upper third of T11 to the lower third of L1, above the lower edge of L1. With an average follow-up of 30.4 months, the modified Japanese Orthopedic Association score significantly improved from 5.7 ± 1.8 preoperatively to 8.9 ± 1.4 postoperatively (t = 12.05; P < 0.0001) with an improvement rate of 63.1 ± 12.3%.

Conclusions:

SK is a rare radiological phenomenon. It is typically located at the thoracolumbar junction, where the CM is compressed by the OLF. Our findings indicate that these patients may benefit from a posterior decompressive procedure.

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.

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.

Symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with ossification of the ligamentum flavum: a case report

STUDY DESIGN

A case report.

OBJECTIVE

To describe a rare case of symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with ossification of the ligamentum flavum (OLF).

SUMMARY OF BACKGROUND DATA

Spinal cord kinking without spinal surgery is rare, and symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with OLF is even rarer.

METHODS

A 66-year-old female presented with numbness of the lower extremities and subsequently experienced gait disturbance due to motor weakness. Magnetic resonance imaging of the thoracic spine showed anterior displacement and kinking of the spinal cord from T11 to T12. Laminectomy and OLF resection were performed. The arachnoid membrane at the affected part was markedly thick and seemed cloudy. Adhesiolysis for arachnoid adhesion and release of spinal kinking were performed.

RESULTS

She could walk with a cane 6 months postoperatively. One year postoperatively, thoracic computed tomography-myelography showed that the cord was repositioned in the dural sac, and that release of the spinal cord kink was maintained.

CONCLUSION

Symptomatic spinal cord kinking due to focal adhesive arachnoiditis, with OLF is a rare clinical condition. It was difficult to diagnose the precise pathology of the spinal cord before surgery. Microsurgical arachnoidolysis resolved the spinal cord kinking, and no recurrence was noted within the follow-up period.

LEVEL OF EVIDENCE

N/A.

Prevalence, distribution, and morphology of thoracic ossification of the posterior longitudinal ligament in Japanese: results of CT-based cross-sectional study

STUDY DESIGN

A cross-sectional study.

OBJECTIVE

To gain an insight into the prevalence, morphology, and distribution of thoracic ossification of the posterior longitudinal ligament of the spine (T-OPLL) by computed tomography (CT) and review of the literature.

SUMMARY OF BACKGROUND DATA

The epidemiology and cause of T-OPLL remains obscure. To date, to the best of our knowledge, there is no study that has comprehensively evaluated the thoracic spine by CT to assess the prevalence, distribution, and morphology of T-OPLL in a sufficiently large size of sample with wide distribution of age.

METHODS

The participants of this study were the patients who have undergone chest CT for the examination of pulmonary diseases in our institute. The patients with previous thoracic spine surgery and younger than 15 years were excluded. Prevalence, distribution, and morphology of T-OPLL were reviewed.

RESULTS

A total of 3013 patients (1261 females and 1752 males) with the mean age of 65 years were recruited. The CT-based evidence of T-OPLL was noted in 56 (38 females and 18 males) individuals (1.9%). Most frequently encountered type was liner type, followed by continuous cylindrical type and mixed type. Continuous waveform and beaked type were less frequently encountered. Statistical analyses revealed that T-OPLL was noted at a significantly higher rate among the females. The mean age of T-OPLL-positive males was significantly higher than that of T-OPLL-negative males. Furthermore, there was significant difference of body mass index between T-OPLL-positive and T-OPLL-negative individuals. Most of T-OPLLs were confirmed in higher or middle thoracic regions and the highest peak was found at T3-T4. T-OPLL was noted after the age of 40 years with the peak distribution found at the age of 60 years.

CONCLUSION

The prevalence of T-OPLL in Japanese was 1.9%. Further studies that characterize definitive subtypes of T-OPLL on CT are warranted so as to establish possible association between clinical manifestations and size and/or subtypes of T-OPLL.

LEVEL OF EVIDENCE

N/A.