Precise Surgical Treatment of Thoracic Ossification of Ligamentum Flavum Assisted by O-Arm Computer Navigation: A Retrospective Study

S8 Navigation system combined with an ultrasonic osteotome for three-dimensional real-time dynamic visualization decompression to reduce postoperative neurological deterioration in thoracic ossification of the ligamentum flavum

BACKGROUND

Posterior laminectomy is a standard treatment for thoracic ossification of the ligamentum flavum (TOLF), but it often leads to neurological deterioration during surgery. This study aimed to reduce iatrogenic neurological deterioration by using an S8 navigation system combined with an ultrasonic osteotome for three-dimensional real-time dynamic visualization decompression.

METHODS

A retrospective analysis was conducted on patients who underwent laminectomy and internal fixation for TOLF in our centre from January 2016 to January 2023. Patients were divided into a visualization group (S8 navigation + ultrasonic bone scalpel) and a control group (ultrasonic bone scalpel) based on the use of three-dimensional real-time dynamic visualization decompression technology. Intraoperative multimodal neuroelectrophysiological monitoring (IONM) was used to collect somatosensory evoked potential and motor evoked potential data. We compared the incidence of intraoperative neurological deterioration indicated by IONM alarms between the two groups. Neurological and motor functions were assessed via the American Spinal Injury Association (ASIA) classification system and the modified Japanese Orthopaedic Association (m-JOA) score for thoracic myelopathy. Follow-ups were conducted at 1, 3, 6, and 12 months postsurgery, and the data from both groups were compared. Other clinical indicators included decompression time per laminectomy segment, intraoperative blood loss, intraoperative dural ossification, hospitalization duration, and drainage tube placement time. We also analysed intraoperative and postoperative complications.

RESULTS

A total of 91 patients with thoracic ossification of the ligamentum flavum were included, with a follow-up period of 12-18 months. The visualization group consisted of 41 patients, and the control group included 50 patients. The incidence of neurological deterioration indicated by IONM in the visualization group (9.8%) was significantly lower than that in the control group (30.0%) (P = 0.014). The immediate postoperative ASIA grade change value ≤ - 1 was lower in the visualization group (9.8%) than in the control group (34.0%) (P = 0.006); A similar trend was observed at the 12 month follow-up (2.4% vs. 20.0%, P = 0.022). The m-JOA scores at 1, 3, 6, and 12 months postsurgery were higher in the visualization group than in the control group (P < 0.05). The visualization group also had shorter lamina decompression times per segment and less intraoperative blood loss (P < 0.05). The incidence of nondural ossification cerebrospinal fluid leakage was lower in the visualization group (2.4%) than in the control group (18.0%) (P = 0.018). Additionally, nerve root injury was lower in the visualization group (0%) than in the control group (10.0%) (P = 0.037). Postoperative CT scans revealed no ossification residue in the visualization group, whereas 7 cases (14.0%) were observed in the control group (P = 0.013).

CONCLUSION

The S8 navigation system combined with an ultrasonic osteotome for three-dimensional real-time dynamic visualization decompression significantly reduces the incidence of intraoperative neurological deterioration, improves postoperative motor function recovery, and reduces decompression time per vertebral segment, intraoperative bleeding, and complications such as cerebrospinal fluid leakage. This technology is safe and reliable and offers a promising option for spinal surgeons in treating thoracic ossification of the ligamentum flavum.

Incremental regression of localization context for automatic segmentation of ossified ligamentum flavum from CT data

PURPOSE

Segmentation of ossified ligamentum flavum (OLF) plays a crucial role in developing computer-assisted, image-guided systems for decompressive thoracic laminectomy. Manual segmentation is time-consuming, tedious, and label-intensive. It also suffers from inter- and intra-observer variability. Automatic segmentation is highly desired.

METHODS

A two-stage, localization context-aware framework is developed for automatic segmentation of ossified ligamentum flavum. In the first stage, localization heatmaps of OLFs are obtained via incremental regression. In the second stage, the obtained heatmaps are then treated as the localization context for a segmentation U-Net. Our framework can directly map a whole volumetic data to its volume-wise labels.

RESULTS

We designed and conducted comprehensive experiments on datasets of 100 patients to evaluate the performance of the proposed method. Our method achieved an average Dice similarity coefficient of 61.2 ± 7.6%, an average surface distance of 1.1 ± 0.5 mm, and an average positive predictive value of 62.0 ± 12.8%.

CONCLUSION

To the best knowledge of the authors, this is the first study aiming for automatic segmentation of ossified ligamentum flavum. Results from the comprehensive experiments demonstrate the superior performance of the proposed method over the state-of-the-art methods.

Distinctive Characteristics of Thoracolumbar Junction Region Stenosis

STUDY DESIGN

Retrospective case series and systemic literature meta-analysis.

BACKGROUND

Thoracolumbar junction region stenosis produces spinal cord compression just above the conus and may manifest with symptoms that are not typical of either thoracic myelopathy or neurogenic claudication from lumbar stenosis.

OBJECTIVE

As few studies describe its specific pattern of presenting symptoms and neurological deficits, this investigation was designed to improve understanding of this pathology.

METHODS

A retrospective review assessed surgically treated cases of T10-L1 degenerative stenosis. Clinical outcomes were evaluated with the thoracic Japanese Orthopedic Association score. In addition, a systematic review and meta-analysis was performed in accordance with guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

Of 1069 patients undergoing laminectomy at 1477 levels, 31 patients (16M/15F) were treated at T10-L1 a mean age 64.4 (SD=11.8). Patients complained of lower extremity numbness in 29/31 (94%), urinary dysfunction 11/31 (35%), and back pain 11/31 (35%). All complained about gait difficulty and objective motor deficits were detected in 24 of 31 (77%). Weakness was most often seen in foot dorsiflexion 22/31 (71%). Deep tendon reflexes were increased in 10 (32%), decreased in 11 (35%), and normal 10 (32%); the Babinski sign was present 8/31 (26%). Mean thoracic Japanese Orthopedic Association scores improved from 6.4 (SD=1.8) to 8.4 (SD=1.8) ( P <0.00001). Gait subjectively improved in 27/31 (87%) numbness improved in 26/30 (87%); but urinary function improved in only 4/11 (45%).

CONCLUSIONS

Thoracolumbar junction stenosis produces distinctive neurological findings characterized by lower extremity numbness, weakness particularly in foot dorsiflexion, urinary dysfunction, and inconsistent reflex changes, a neurological pattern stemming from epiconus level compression and the myelomeres for the L5 roots. Surgery results in significant clinical improvement, with numbness and gait improving more than urinary dysfunction. Many patients with thoracolumbar junction stenosis are initially misdiagnosed as being symptomatic from lumbar stenosis, thus delaying definitive surgery.

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.

Ossified Ligamentum Flavum: Epidemiology, Treatment, and Outcomes

Ossification of the ligamentum flavum (OLF) is an uncommon but potentially serious spinal condition which can cause progressive compression of the spinal canal with associated devastating neurologic compromise. Although debate exists regarding the exact etiology of OLF, overexpression of genes and transcription factors centered around the Notch and Wnt signaling pathways because of increased mechanical stress seems to be related. There are many clinical and radiographic presentations of OLF; however, progressive myelopathy is the most commonly encountered. Radiographic analysis may reveal isolated OLF or OLF combined with ossification of other areas of the spine, such as disk, posterior longitudinal ligament, and dura. When surgery is necessary for OLF, several surgical strategies exist including open laminectomy with excision, endoscopic decompression, Bridge Crane resection, en block resection, and combined anterior and posterior approaches. Resection may be complicated by dural adhesion or dural ossification, and postoperative neurologic deficits are not uncommon.