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.