Is there a relationship between low back pain and ligamentum flavum hypertrophy?

OBJECTIVE: A condition known as ligamentum flavum (LF) hypertrophy occurs when the ligamentum flavum (LF) swells as a result of pressures applied to the spine. Among the elderly population, lumbar spinal stenosis is a major cause of pain and disabilities. Numerous studies indicate that lumbar spinal stenosis etiology involves the ligamentum flavum in a major way. This study looks into the relationship between low back pain and ligamentum flavum thickening. PATIENTS AND METHODS: The imaging tests and case histories of all patients with low back pain who had consecutive magnetic resonance imaging exams performed at the Prince Sattam University and King Khalid hospitals in Al Kharj City will serve as the basis for this retrospective observational study. A radiologist utilized the Pfirrmann grading system, which is based on spinal levels starting from the first lumbar to the first sacral vertebrae, to measure the thickness of the ligamentum flavum in all cases who underwent magnetic resonance imaging (MRI). A correlation between age, hypertrophy of LF, and low back pain was investigated. RESULTS: There were 79 participants in the study, ages ranging from 21 to 82, 49 of which were men. The patients' average age was 54 years, and 62% of them were men. We found no appreciable variations in LF thickness according to gender. At the L4-L5 and L5-S1 levels, the left LF was noticeably thicker than the right. Moreover, there was a significant difference (p < 0.05) in the bilateral LF thicknesses at L5-S1 compared to the comparable sides at L4-L5. CONCLUSIONS: By evaluating the thickness of LF on magnetic resonance images, we discovered that it may be closely associated with the etiology of pain processes in the spine.

Full endoscopic surgery for calcium pyrophosphate deposition disease (CPPD) in the cervical ligamentum flavum: report of two cervical myelopathy cases.

Calcium pyrophosphate deposition disease (CPPD), known as pseudogout, is characterized by the accumulation of calcium pyrophosphate crystals in musculoskeletal structures, primarily joints. While CPPD commonly affects various joints, involvement in the cervical spine leading to myelopathy is rare. Surgical intervention becomes necessary when conservative measures fail, but reports on full endoscopic surgeries are extremely rare. We present two successful cases where full endoscopic systems were used for CPPD removal in the cervical spine. The surgical technique involved a full endoscopic approach, adapting the previously reported technique for unilateral laminotomy bilateral decompression. Full-endoscopic removal of cervical CPPD inducing myelopathy were successfully removed with good clinical and radiologic outcomes. The scarcity of endoscopic cases for cervical ligamentum flavum CPPD is attributed to the condition's rarity. However, our successful cases advocate for endoscopic surgery as a potential primary treatment option for CPPD-induced cervical myelopathy, especially in elderly patients or those with previous cervical operation histories. This experience encourages the consideration of endoscopic surgery for managing cervical ligamentum flavum CPPD as a viable alternative.

Lumbar Spinous Process-Splitting Technique for Ligamentum Flavum Cyst Removal.

BACKGROUND: Laminotomy for lumbar stenosis is a well-defined procedure and represents a routine in every neurosurgical department. It is a common experience that the uni- or bilateral paraspinal muscle detachment, together with injury of the supra- and interspinous ligaments, can lead to postoperative pain. In the literature, the application of a minimally invasive technique, the lumbar spinous process-splitting (LSPS) technique, has been reported. METHODS: In this study, we present a case series of 12 patients who underwent LSPS from September 2019 to April 2020. Two patients had a cyst of the ligamentum flavum, eight a single-level lumbar canal stenosis (LCS), and two a two-level LCS. Moreover, we propose a novel morphological classification of postoperative muscle atrophy and present volumetric analysis of the decompression achieved. RESULTS: There were no complications related to this technique. In all patients, the vertebral canal area was more than doubled by the procedure. The muscle sparing showed grade A, according to our classification. CONCLUSION: To our knowledge, this is the first description of this surgical technique and the first LSPSL case series in Europe. Furthermore, cases of ligamentum flavum cyst removal using this safe and effective technique have not yet been reported.

Quantitative evaluation of the lumbar ligamentum flavum using MRI T2-mapping: Efficacy of its clinical application in patients with lumbar spinal stenosis.

OBEJECTIVE: To perform a magnetic resonance imaging T2-mapping of the ligamentum flavum in healthy individuals and patients with lumbar spinal stenosis scheduled for surgery and compare the T2 relaxation times. SUBJECTS AND METHODS: The T2 relaxation time of the ligamentum flavum was compared among 3 groups, healthy young individuals (H group (age< 50)), healthy middle-aged and older individuals (H group (age≥50)), and patients with lumbar spinal stenosis (L group). Additionally, the thickness of the ligament was measured in the axial image plane, and the occupied area ratio of each fiber was measured by staining the surgically obtained ligament, and each was correlated with the T2 relaxation time. We also evaluated the adhesion of the ligamentum flavum with the dura mater during the surgery. RESULTS: The T2 relaxation times were significantly prolonged in H group (age ≥50) and L group (P < 0.001) compared to H group (age<50). The relationship between collagen fiber and T2 relaxation times was significantly positive (r = 0.720, P < 0.001). Moreover, the relaxation times were significantly prolonged in those with adhesion of the ligamentum flavum with the dura mater (P < 0.05). The cut-off for the relaxation time was 50 ms (sensitivity: 62.50%, false positive rate: 10.8%). CONCLUSION: Healthy middle-aged and older individuals and patients with lumbar spinal stenosis and adhesion of the ligamentum flavum with the dura mater have prolonged T2 relaxation times. Hence, the adhesion between the ligamentum flavum and dura mater should be considered in cases with a relaxation time ≥50 ms.

The cervical ligamentum flavum area: A new sensitive morphological parameter for identifying the cervical spinal stenosis.

Thickening of the cervical ligamentum flavum (CLF) has been considered as a main cause of cervical spinal stenosis (CSS). A previous study reported that cervical ligamentum flavum thickness (CLFT) is correlated with CSS. However, the whole hypertrophy is different from focal thickness. Therefore, to analyze hypertrophy of the CLF, we created a new morphological parameter, called the cervical ligamentum flavum area (CLFA). We hypothesized that the CLFA is an important morphological parameter in the diagnosis of CSS. CLF samples were acquired from 83 patients with CSS, and from 84 controls who underwent cervical magnetic resonance imaging (C-MRI). T2-weighted axial C-MRI images were acquired. We measured the CLFA and CLFT at the C6-C7 intervertebral level on C-MRI using appropriate image analysis software. The CLFA was measured as the cross-sectional area of the entire CLF at the level of C6-C7 stenosis. The CLFT was measured by drawing a straight line along the ligament side towards the spinal canal at the C6-C7 level. Mean CLFA was 25.24 ±â€…6.43 mm2 in the control group and 45.34 ±â€…9.09 mm2 in the CSS group. The average CLFT was 1.48 ±â€…0.28 mm in the control group and 2.09 ±â€…0.35 mm in the CSS group. CSS patients had significantly higher CLFA (P < .01) and CLFT (P < .01). For the validity of both CLFA and CLFT as predictors of CSS, a receiver operating characteristic curve analysis revealed an optimal cutoff point for the CLFA was 31.66 mm2, a sensitivity of 92.8%, specificity of 88.4%, and an area under the curve of 0.97 (95% CI, 0.94-0.99). The optimal cut off-point of the CLFT was 1.79 mm, with a sensitivity of 83.5%, specificity of 84.5%, and an area under the curve of 0.92 (95% CI, 0.87-0.96). Both CLFT and CLFA were significantly related to CSS, but CLFA was the more sensitive measurement parameter. Therefore, to evaluate patients with CSS, treating physicians should test for CLFA.

Comparison of ligamentum flavum thickness between central and lateral lesions in a patient with central lumbar spinal canal stenosis.

Thickened ligamentum flavum has been considered as a major cause of central lumbar spinal canal stenosis (CLSCS). Previous studies have demonstrated that ligamentum flavum thickness (LFT) is correlated with aging, degenerative spinal stenosis, and disc degeneration. Thus, hypertrophy of the ligamentum flavum is a major cause of CLSCS, and measurement of LFT has been considered a morphologic parameter in the diagnosis of CLSCS. To our knowledge, comparison of LFT between central and lateral lesions has not been reported. In addition, no research has analyzed best clinical cutoff values of central ligament flavum thickness (CLFT) and lateral ligament flavum thickness (LLFT). This study aimed to compare CLFT with LLFT in patients with CLSCS and further compare the CLFT and LLFT findings between the 2 groups to analyze LFT variation. Both CLFT and LLFT samples were collected from 101 participants with CLSCS and from 103 participants in the control group who underwent lumbar magnetic resonance imaging without evidence of CLSCS. Axial T2-weighted lumbar magnetic resonance scans were acquired at the L4 to 5 facet joint level from each participant. Average CLFT value was 2.25 ± 0.51 mm in the control group and 4.02 ± 0.74 mm in the CLSCS group. Average LLFT value was 2.50 ± 0.51 mm in the control group and 3.38 ± 0.66 mm in the CLSCS group. CLSCS patients had significantly higher CLFT and LLFT (both P < .001). Regarding the validity of both CLFT and LLFT as predictors of CLSCS, a receiver operating characteristic estimation revealed that the most suitable cutoff value for CLFT was 3.10 mm, with sensitivity of 95.0%, specificity of 94.2%, and an area under the curve of 0.97. The best cut-off value of LLFT was 2.92 mm, with sensitivity of 78.2%, specificity of 77.7%, and area under the curve of 0.87. We have 4 important new findings: The mean CLFT is significantly lower than that of the mean LLFT in the normal control group; CLFT and LLFT are both significantly associated with CLSCS; Increase rate of CLFT is faster than that of LLFT in the CLSCS group; and CLFT is a more sensitive measurement parameter to predict CLSCS than LLFT.

How I do it: the biportal endoscopic inclined-ipsilateral technique to decompress the lumbar lateral recess.

BACKGROUND: Various full-endoscopic techniques have been developed to reach the lateral recess of the lumbar spine. However, specialized surgical tools, including expensive spinal endoscopic systems, and a steeper learning curve to mastering the technique are required. METHOD: We present a novel target-addressed unilateral biportal endoscopic technique to reach directly the lumbar lateral recess, particularly useful at L4-L5 and L5-S1. The technique follows an inclined-ipsilateral trajectory to preserve the lateral extension of ligamentum flavum and the facet joint as much as possible. CONCLUSION: This technique was associated with all the advantages of minimally invasive decompressive procedures and outstanding outcomes.

Prevalence of amyloid in ligamentum flavum of patients with lumbar spinal stenosis.

BACKGROUND: Transthyretin (ATTR) amyloidosis is often diagnosed in an advanced stage, when irreversible cardiac damage has occurred. Lumbar spinal stenosis (LSS) may precede cardiac ATTR amyloidosis by many years, offering the opportunity to detect ATTR already at the time of LSS surgery. We prospectively assessed the prevalence of ATTR in the ligamentum flavum by tissue biopsy in patients aged >50 years undergoing surgery for LSS. METHODS: Ligamentum flavum thickness was assessed pre-operatively on axial T2 magnetic resonance imaging (MRI) slices. Tissue samples from ligamentum flavum were screened centrally by Congo red staining and immunohistochemistry (IHC). RESULTS: Amyloid in the ligamentum flavum was detected in 74/94 patients (78.7%). IHC revealed ATTR in 61 (64.9%), whereas amyloid subtyping was inconclusive in 13 (13.8%). Mean thickness of ligamentum flavum was significantly higher at all levels in patients with amyloid (p < .05). Patients with amyloid deposits were older (73.1 ± 9.2 vs. 64.6 ± 10.1 years, p = .01). No differences in sex, comorbidities, previous surgery for carpal tunnel syndrome or LSS were observed. CONCLUSIONS: Amyloid, mostly of the ATTR subtype, was found in four out of five patients with LSS and is associated with age and ligamentum flavum thickness. Histopathological work-up of ligamentum flavum might inform future decision making.

Endoscopic treatment of lumbar ligamentum flavum cyst by interlaminar approach: a minimally invasive and effective alternative to open surgery.

BACKGROUND AND OBJECTIVES: Lumbar ligamentum flavum cyst is a rare spinal condition that can cause significant morbidity and neurological deficits. Traditional surgical treatment involves open surgery, which can be associated with prolonged recovery time and significant morbidity. In recent years, endoscopic treatment of lumbar ligamentum flavum cyst has emerged as a minimally invasive and effective alternative to open surgery, but only a few cases have been reported in the literature. This paper describes our experience with endoscopic resection of an L4/5 ligamentum flavum cyst through an interlaminar approach and reviews the literature on the treatment of lumbar ligamentum flavum cyst. METHODS: An 87-year-old man presented with lameness in the left leg, and magnetic resonance imaging (MRI) showed nerve compression by a ligamentum flavum cyst at the L4/5 intervertebral plane. The patient underwent endoscopic resection of the ligamentum flavum cyst through a left interlaminar approach with the facet joint preserved. The present study was approved by the Ethics Committee of our hospital. The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request. Text regarding patient consent is not applicable for this case. RESULTS: Postoperative clinical results improved significantly, and postoperative MRI showed complete cyst resection. CONCLUSION: Total endoscopic resection via an interlaminar approach provides a new minimally invasive approach for the surgical treatment of lumbar ligamentum flavum cyst, which can be used as a reference by clinicians.

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

BACKGROUND: Previous studies have demonstrated satisfactory outcomes of percutaneous endoscopic thoracic decompression (PETD) for single-segment thoracic ossification of the ligamentum flavum (TOLF). However, the clinical outcomes of PETD in patients with multi-segment TOLF (mTOLF) remain unclear. The aim of the present study was to evaluate the efficacy and safety of PETD for patients with multi-segment mTOLF. METHODS: Eighteen consecutive patients (41 segments) with mTOLF were treated with PETD between January 2020 and December 2021. The clinical outcomes were evaluated using the modified Japanese Orthopaedic Association (mJOA) score and Visual Analog Scale (VAS), whereas radiographic parameters were measured by cross-section area of the spinal canal and anteroposterior diameter of the spinal cord. RESULTS: The follow-up period ranged from 14 to 34 months. The mean operation time and blood loss were 154.06 ± 32.14 min and 61.72 ± 12.72 ml, respectively. Hospital stay after first-stage operation was 10.89 ± 2.42 days. The mJOA score and VAS score significantly improved at the final follow-up, with a mean mJOA recovery rate of 63.3 ± 21.90%. The incidence of complications was 12.2% per level. The radiographic outcomes showed adequate decompression of the spinal cord. CONCLUSIONS: The present study demonstrates that PETD is effective and safe as a minimally invasive procedure to treat patients with mTOLF. All patients showed relief of their symptoms and improvement in neurological function.

Laminectomy for the Removal of Thoracic Ossification of the Ligamentum Flavum (TOLF) Using Ultrasonic and Conventional Osteotomes.

Thoracic ossification of the ligamentum flavum (TOLF) is a common cause of progressive thoracic myelopathy. TOLF is typically treated with surgical decompression. A variety of surgical techniques, including laminoplasty, laminectomy, and lamina fenestration, are used for the effective treatment of TOLF. However, traditional methods are associated with a substantial risk of perioperative complications, including dural laceration and/or iatrogenic spinal cord injury. Therefore, it is important to develop an efficient and secure surgical technique for TOLF. Herein, we describe a method for laminectomyperformed at the thoracic spine using an ultrasonic osteotome combined with a conventional osteotome. This technique can reduce intraoperative complications. This is a relatively safe and easy-to-learn method that should be recommended for the treatment of TOLF.

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

STUDY DESIGN: Systematic review. BACKGROUND CONTEXT: Thoracic ossification of the ligamentum flavum (TOLF) has become the principal cause of thoracic spinal stenosis. Dural ossification (DO) was a common clinical feature accompanying with TOLF. However, on account of the rarity, we know little about the DO in TOLF so far. PURPOSE: This study was conducted to elucidate the prevalence, diagnostic measures, and impact on the clinical outcomes of DO in TOLF by integrating the existing evidence. METHODS: PubMed, Embase, and Cochrane Database were comprehensively searched for studies relevant to the prevalence, diagnostic measures, or impact on the clinical outcomes of DO in TOLF. All retrieved studies meeting the inclusion and criterion were included into this systematic review. RESULTS: The prevalence of DO in TOLF treated surgically was 27% (281/1046), ranging from 11 to 67%. Eight diagnostic measures have been put forward to predict the DO in TOLF using the CT or MRI modalities, including "tram track sign", "comma sign", "bridge sign", "banner cloud sign", "T2 ring sign", TOLF-DO grading system, CSAOR grading system, and CCAR grading system. DO did not affect the neurological recovery of TOLF patients treated with the laminectomy. The rate of dural tear or CSF leakage in TOLF patients with DO was approximately 83% (149/180). CONCLUSION: The prevalence of DO in TOLF treated surgically was 27%. Eight diagnostic measures have been put forward to predict the DO in TOLF. DO did not affect the neurological recovery of TOLF treated with laminectomy but was associated with high risk of complications.

Hypertrophied posterior longitudinal ligament and ligamentum flavum causing myelopathy: a case report and literature review.

INTRODUCTION: The occurrence of concurrent hypertrophied posterior longitudinal ligament (HPLL) and hypertrophied ligamentum flavum (HLF) in the thoracic spine is a very rare presentation. This case report describes a young female who developed thoracic myelopathy secondary to a combination of both thoracic HPLL and HLF. CASE PRESENTATION: A 30-year-old previously well female was referred for an MRI scan of the thoraco-lumbar spine. She was having lower limb weakness and difficulty in walking, which had progressed over 3 months. On examination, she was found to have spastic lower limbs with associated motor weakness. Her biochemical investigations were unremarkable. The MRI scan showed HPLL, which was uniformly hypointense on T2W images and was isointense on T1W images. The hypertrophied segment was extending from T2 level to T7 level. Similarly, the ligamentum flavum was hypertrophied from T1 level to T8 level. The thoracic spinal cord was seen compressed between the hypertrophied ligaments. The compressed cord showed central hyperintense signal pattern in T2W images. CT scan of the thoracic spine did not show any calcifications or ossifications along the ligaments. Patient underwent posterior decompressive surgery and she had an uneventful recovery. DISCUSSION: Although few cases of HPLL and HLF were reported in older patients in literature, both these conditions were found in this patient at a younger age. HPLL and HLF are thought to be precursors of ossification of these ligaments and these patients need long-term follow-up.

Ligamentum Flavum Rupture by Epidural Injection Using Ultrasound with SMI Method.

The loss of resistance (LOR) method has been used exclusively to identify epidural space. It is difficult to find the epidural space without the risk of dural puncture. Various devices have been developed to improve the accuracy of the LOR method; however, no method has overcome the problems completely. Therefore, we devised a ligamentum flavum rupture method (LFRM) in which the needle tip is placed only on the ligamentum flavum during the epidural injection, and the injection pressure is used to rupture the ligamentum flavum and spread the drug into the epidural space. We confirmed the accuracy of this method using ultrasound with superb microvascular imaging (SMI) to visualize the epidural space. Here, we report two cases of 63-year-old and 90-year-old males. The 63-year-old patient presented with severe pain in his right buttock that extended to the posterior lower leg. The 90-year-old patient presented with intermittent claudication every 10 min. LFRM was performed, and SMI was used to confirm that the parenteral solution had spread into the epidural space. Our results indicate that LFRM can be used for interlaminar lumbar epidural steroid injections.

Lumbar ossification of the ligamentum flavum reflects a strong ossification tendency of the entire spinal ligament.

Patients with ossification of the ligamentum flavum (OLF) in the lumbar spine may be at high risk of developing concomitant ossification of the entire spinal ligament, but the etiology remains unclear. We investigated the propensity for spinal ligament ossification in asymptomatic subjects with lumbar OLF using the data of 595 Japanese individuals receiving medical check-ups, including computed tomography (CT) scanning. The severity of OLF (total number of intervertebral segments with OLF) of the entire spine on CT was quantified using an OLF index. Subjects with OLF were grouped according to this index: localized OLF (n = 138), intermediate OLF (n = 70), and extensive OLF (n = 31). The proportion of subjects with lumbar OLF increased with increasing OLF index (localized 13.7%, intermediate 41.4%, and extensive 70.9%). Multiple regression analysis found that lumbar OLF index was associated with thoracic OLF index, and co-existence of ossification of the posterior longitudinal ligament (OPLL) of the thoracic and lumbar spine. This study showed that subjects with more multilevel lumbar OLF were more likely to develop multilevel thoracic OLF and to have coexisting OPLL. Patients with lumbar OLF may be a distinctive subgroup with a strong tendency to ossification of the entire spinal ligament.

En bloc resection of ligamentum flavum with laminotomy of the caudal lamina in the minimally invasive laminectomy: surgical anatomy and technique.

OBJECTIVE: A CSF leak is a potential complication in a lumbar laminectomy. An analysis of the author's surgical experience identified inadvertent durotomies that occurred when resecting the ligamentum flavum at its insertion into the superior aspect of the caudal lamina. Anatomical analyses of the lumbar canal diameter demonstrate that the insertion point of the caudal ligamentum flavum is the most constrained area of the canal. The surgical technique was modified to eliminate the need for direct action in that anatomical region after the author compared the efficacy of piecemeal resection of the ligamentum flavum with en bloc resection with a laminotomy of the caudal lamina beyond the insertion point of the ligamentum flavum in the lumbar laminectomy. METHODS: An analysis of a single surgeon's experience managing 147 consecutive patients with lumbar stenosis who underwent single-level lumbar hemilaminectomies over a 4-year period was performed. Patients were managed with either piecemeal resection (cohort 1) or en bloc resection with a laminotomy beyond the caudal insertion (cohort 2) of the ligamentum flavum. RESULTS: Seventy-seven patients underwent piecemeal resection (cohort 1), and 70 underwent en bloc resection (cohort 2). There were 5 CSF leaks (6.4%) in cohort 1. There were no CSF leaks in cohort 2. There was a statistically significant difference in operative times between the two groups (p = 0.04), but there was no statistically significant difference in patient-reported outcomes at 6 months between the groups. CONCLUSIONS: En bloc resection of the ligamentum flavum with a laminotomy below the caudal insertion point appears to decrease the risk of a CSF leak by working beyond the most constrained diameter of the lumbar canal to release the caudal insertion of the ligamentum flavum.

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.

Human lumbosacral root and ligamentum flavum thicknesses: a magnetic resonance study.

BACKGROUND: This study investigated the lumbosacral plexus (LSP) nerve root thickness and ligamentum flavum (LF) thickness and correlated them with age and sex. These findings provided a useful data for spinal nerve root micro-anastomosis surgery and lumbar decompression surgery. MATERIALS AND METHODS: This retrospective study was conducted with 350 individuals with ages ranging from 21 to 80 years under magnetic resonance imaging to evaluate the possible cause of a lower back pain. RESULTS: According to the morphometric measurements of the LSP root thickness, the diameter gradually increased from L1 to S1. L1 has the thinnest root (3.9 ± 0.81 mm) while S1 has the thickest root (5.45 ± 0.8 mm). The measurements revealed inconsiderable differences in the LSP thickness in relation to age, sex in the study population. Regarding the LF, the thickness of the LF was found to insignificantly increase with age. Besides, the LF thickness was inconsequentially higher in female. The mean thickness of the right LF at different spinal levels was measured (L2-L3 = 3.19 ± 0.27, L3-L4 = 3.38 ± 0.11 mm, L4-L5 = 3.71 ± 0.29 mm, and L5-S1 = 3.64 ± 0.21 mm). The mean thickness of the left LF was non-significantly higher. CONCLUSIONS: The LSP root and LF thicknesses not related to age or sex.

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

OBJECTIVE: Dural ossification (DO) is a common clinical feature in patients with thoracic ossification of the ligamentum flavum (OLF) and associated with the increased risk of perioperative complications. However, few studies have been conducted to determine the incidence and independent risk factors of DO in patients with thoracic OLF. The aim of this retrospective study was to determine the incidence and independent risk factors of DO in patients with thoracic OLF. METHODS: A total of 107 patients with thoracic OLF who were admitted to the authors' hospital from December 2020 to December 2021 were included in this study. The independent risk factors of DO in patients with thoracic OLF were determined through univariate analysis followed by multivariate logistic regression analysis with p < 0.05. The diagnostic efficacy of the DO in OLF (DO-OLF) risk classification model was determined on the basis of independent risk factors and evaluated on the basis of sensitivity, specificity, and agreement rate. RESULTS: The incidence of DO in patients with thoracic OLF was 35% (37/107 patients). The tuberous type according to the Sato classification (OR 9.75, p < 0.01) and larger (≥ 9°) supine local kyphosis angle (LKA) (OR 8.13, p < 0.01) were two independent risk factors of DO in thoracic OLF. The DO-OLF risk classification, a novel approach for the diagnosis of DO in patients with thoracic OLF, was established on the basis of the combination of the tuberous type according to the Sato classification and larger supine LKA. The sensitivity, specificity, and agreement rate of this approach for distinguishing between patients with thoracic OLF at high and low risk of DO were 87%, 93%, and 91%, respectively. CONCLUSIONS: The incidence of DO in patients with thoracic OLF was 35%. The tuberous type according to the Sato classification and larger supine LKA (≥ 9°) were independent risk factors of DO in patients with thoracic OLF. The novel DO-OLF risk classification approach could serve as an efficient method for predicting DO in patients with thoracic OLF.