[Clinical study of percutaneous endoscopic thoracic spine surgery via trench technique for thoracic spinal cord ventral decompression]

Objective: To evaluate the feasibility, safety, and early effectiveness of percutaneous endoscopic thoracic spine surgery via the trench technique for ventral decompression in central calcified thoracic disc herniation (CCTDH) and thoracic ossification of the posterior longitudinal ligament (T-OPLL).

Methods: Seven patients with single-segment CCTDH or T-OPLL admitted between June 2017 and May 2020 and meeting the selection criteria were retrospectively analyzed. There were 3 males and 4 females with an average age of 51.7 years ranging from 41 to 62 years. There were 2 patients with T-OPLL (T _{1, 2} in 2 cases) and 5 patients with CCTDH (T _{1, 2} in 1 case, T _{7, 8} in 1 case, T _{10, 11} in 2 cases, T _{11, 12} in 1 case). Five patients with thoracic axial pain and intercostal neuralgia had a preoperative visual analogue scale (VAS) score of 6.0 (5.0, 6.5), and 7 patients had a preoperative Japanese Orthopaedic Association (JOA) score of 21 (21.0, 22.0). Transforaminal approach was used in 4 cases and transpedicular approach in 3 cases. Ventral decompression of thoracic spinal cord was performed by thoracic endoscopy combined with trench technique. The operation time, intraoperative blood loss, postoperative hospital stay, and postoperative complications were recorded. Thoracic spine CT and MRI were performed preoperatively and postoperatively to evaluate the surgical decompression, VAS score was used to evaluate the pain of thoracic back and lower limbs, and JOA score was used to evaluate the functional recovery. Modified MacNab criteria was used to evaluate the effectiveness.

Results: All surgeries were successfully completed. The operation time ranged from 60 to 100 minutes, with an average of 80.4 minutes; the intraoperative blood loss ranged from 40 to 75 mL, with an average of 57.1 mL; the postoperative hospital stay ranged from 4 to 7 days, with an average of 5.4 days. CT and MRI examinations indicated that the decompression was adequate. All 7 patients were followed up 3-22 months, with an average of 13.3 months. One case developed postoperative wound infection, and 1 case developed pneumonia; the remaining patients did not have any complications such as wound infection or cerebrospinal fluid leakage. Five patients with thoracic axial pain and intercostal neuralgia had VAS scores of 2.0 (1.5, 2.5) at 1 day after operation and 2.0 (1.0, 2.0) at last follow-up, both of which were significantly lower than the preoperative scores ( P<0.05). At 1 day after operation, the JOA scores for all 7 patients were 22.0 (21.0, 24.0), which showed no significant difference compared to the preoperative score ( P>0.05); however, at last follow-up, the score improved to 24.0 (24.0, 26.0), which was significant compared to the preoperative scores ( P<0.05). At last follow-up, the effectiveness was assessed using the modified MacNab criteria, the results were excellent in 2 cases, good in 3 cases, fair in 2 cases, and the excellent and good rate was 71.4%.

Conclusion: Using the trench technique, percutaneous endoscopic thoracic spine surgery can achieve the ventral decompression in CCTDH and T-OPLL, providing a new approach for surgical treatment of CCTDH and T-OPLL.