A modified percutaneous transforaminal endoscopic surgery for central calcified thoracic disc herniation at the T11/T12 level using foraminoplasty and decompression - A case report

At a Glance

Metadata	Details
Publication Date	2023-05-09
Journal	Frontiers in Surgery
Authors	Hou Lisheng, Tian Suhuai, Dong Zhang, Qing Zhou
Institutions	Chinese PLA General Hospital
Citations	2
Analysis	Full AI Review Included

Executive Summary

This report analyzes a modified Percutaneous Transforaminal Endoscopic Surgery (PTES) technique developed for the minimally invasive treatment of Central Calcified Thoracic Disc Herniation (CCTDH) at the T11/T12 level.

Core Challenge: CCTDH is rare, and traditional open surgery carries high risks of morbidity and complications (e.g., pneumothorax, severe post-thoracotomy pain).
Technical Innovation: The procedure combines a modified PTES approach with a two-stage foraminoplasty (fluoroscopic and endoscopic) using a hand trephine, followed by decompression using a flexible endoscopic power diamond drill.
Tooling Advancement: The flexible power diamond drill (max 25,000 r/min, 30° articulation) allows for safe, high-speed thinning and degradation of the calcified shell using a “no-touch technique” to protect the fragile dural sac.
Procedural Mechanics: An “inside-out” decompression technique was employed initially, undermining soft disc fragments ventral to the calcified shell to create a protective cavity before fracturing the shell piece by piece.
Outcome Validation: The procedure resulted in complete CCTDH removal, minimal blood loss, and no complications. The patient’s modified Japanese Orthopedic Association (mJOA) score improved significantly from 12 (pre-op) to 18 (2-year follow-up).
Conclusion: Modified PTES offers a viable, less invasive alternative to traditional open surgery for complex CCTDH, though it requires significant surgical expertise due to technical demands and a steep learning curve.

Technical Specifications

Parameter	Value	Unit	Context
Skin Entrance Point Distance	6	cm	Lateral distance from the midline (Gu’s point) for the T11/T12 approach.
Hand Trephine Diameter	7.5	mm	Used during the fluoroscopic foraminoplasty stage.
Protection Cannula Outer Diameter	8.8	mm	Used to dock at the anterolateral edge of the Superior Articular Process (SAP).
Guiding Rod (GD) Diameter	6.3	mm	Used to establish the trajectory after dilating cannulas are removed.
Trephine Penetration Depth	5-8	mm	Depth of rotation into the ventral SAP bone during fluoroscopic foraminoplasty.
Endoscope Angle	30	degrees	Angle of the endoscope used for full endoscopic visualization.
Flexible Drill Maximum Angle	30	degrees	Maximal articulation angle of the flexible endoscopic diamond burr distal end.
Flexible Drill Rotation Speed (Max)	25,000	r/min	Highest rotation speed of the flexible endoscopic diamond burr.
Operation Time	100	min	Total duration of the modified PTES procedure.
Preoperative mJOA Score	12	points	Baseline neurological function score.
Postoperative mJOA Score (2 years)	18	points	Final neurological function score, indicating full recovery.

Key Methodologies

The modified PTES procedure was conducted under local anesthesia and conscious sedation, utilizing a unilateral posterolateral approach.

Targeting and Trajectory:
- Patient placed prone on a radiolucent table.
- Target disc (T11/T12) and skin entrance point (Gu’s point, 6 cm lateral) identified using C-arm fluoroscopy.
- Soft tissue trajectory established using dilating cannulas over a guidewire to the anterolateral edge of the Superior Articular Process (SAP).
Fluoroscopic Foraminoplasty (Early Stage):
- A 6.3 mm guiding rod and 8.8 mm protection cannula were docked at the SAP.
- A 7.5 mm hand trephine was introduced and rotated 5-8 mm into the lateral ventral SAP bone under C-arm confirmation, isolating a bone chunk while preserving the medial cortex.
Endoscopic Foraminoplasty (Later Stage):
- A 30° endoscope was inserted via the trephine’s cavity.
- Soft tissues were stripped to confirm bony landmarks under direct visualization.
- The trephine was rotated deeper until the isolated bone chunk was completely removed, ensuring adequate foramen enlargement without neural structure damage.
Decompression (Inside-Out Technique):
- The trephine and protection cannula were replaced by a working cannula.
- Soft disc fragments ventral to the calcified shell were removed using microforceps (inside-out technique) to create a protective cavity.
Calcified Shell Degradation:
- A flexible endoscopic power diamond drill (max 25,000 r/min, 30° flexible angle) was introduced.
- The calcified shell was thinned using the diamond burr and a “no-touch technique” (using the drill’s articulation to avoid dural sac contact).
- The thinned bony shell was cautiously dissected from the dura using a curved dissector or flexible radiofrequency probe.
Final Removal and Verification:
- The shell was fractured piece by piece within the created cavity.
- Caudal and cephalic bony protrusions were ground off.
- Decompression was confirmed by visualizing the dural sac with visible pulsation.

Commercial Applications

This modified surgical technique and the specialized instrumentation required are highly relevant to the following commercial sectors:

Minimally Invasive Spine Device Manufacturing: Development and refinement of specialized endoscopic tools, including flexible, high-speed diamond burrs (e.g., Chongqing Xishan Technology Co., Ltd, Chongqing, China) and articulating dissectors designed for calcified tissue removal.
Orthopedic Surgical Tooling: Production of specialized hand trephines and cannulas optimized for precise, two-stage foraminoplasty in the thoracic spine region.
Surgical Navigation and Imaging Systems: Integration of C-arm fluoroscopy and high-resolution endoscopic visualization systems to support the complex trajectory and depth control required for PTES.
Medical Training and Simulation: Creation of high-fidelity simulators and training modules to help surgeons master the “joystick technique” and manage the steep learning curve associated with complex endoscopic thoracic procedures.
Biomaterials and Implants: Research into materials used in spinal stabilization and fusion, particularly concerning potential unintended bone removal (as noted in the case) and maintaining spinal stability post-decompression.

View Original Abstract

Background Thoracic disc herniation (TDH) is uncommon. Central calcified TDH (CCTDH) is even rare. Traditional open surgery was considered a gold standard to treat CCTDH, but it was accompanied by a high risk of complications. Recently, a technique called percutaneous transforaminal endoscopic decompression (PTED) was adopted to treat TDH. Gu et al. designed a simplified PTED technique and named it percutaneous transforaminal endoscopic surgery (PTES) to treat various types of lumbar disc herniation; it offered the advantages of simple orientation, easy puncture, reduced steps, and little x-ray exposure. However, PTES to treat CCTDH has not been reported in the literature. Methods Here, we describe the case of a patient with CCTDH treated with a modified PTES through the unilateral posterolateral approach under local anesthesia and conscious sedation by using a flexible power diamond drill. First, we report that the patient was treated with PTES with later-stage endoscopic foraminoplasty, with an inside-out technique employed at the initial endoscopic decompression stage. Results A 50-year-old male with progressive gait disturbance and bilateral leg rigidity with paresis and numbness was diagnosed with CCTDH at the T11/T12 level on MRI and CT examinations. A modified PTES was performed on November 22, 2019. The total mJOA (modified Japanese Orthopedic Association) score preoperatively was 12. The method of the determination of incision and the soft tissue trajectory establishment process were the same as those in the original PTES technique. The foraminoplasty process was divided into initial fluoroscopic and final endoscopic stages. At the fluoroscopic stage, the hand trephine’s saw teeth were just rotated into the lateral portion of the ventral bone from the superior articular process (SAP) to seize the SAP firmly, while at the endoscopic stage, in order to remove the ventral bone from the SAP safely under direct endoscopic visualization, adequate foramen enlargement was achieved without causing any risk of damage to the neural structures in the spinal canal. During the endoscopic decompression process, the soft disc fragments ventral to the calcified shell were undermined to form a cavity using an inside-out technique. Then, a flexible endoscopic diamond burr was introduced to degrade the calcified shell, and a curved dissector or a flexible radiofrequency probe was used to dissect the thin bony shell from the dural sac. Eventually, the shell was fractured within the cavity piece by piece to remove the whole CCTDH and achieve adequate dural sac decompression, resulting in minimal blood loss and no complications. The symptoms were gradually alleviated and the patient almost completely recovered at the 3-month follow-up, with no symptom recurrence found at the 2-year follow-up. The mJOA score improved to 17 at the 3-month follow-up and to 18 at the 2-year follow-up compared with 12 points preoperatively. Conclusions A modified PTES may be an alternative minimally invasive technique for the treatment of CCTDH and provide similar or better outcomes over traditional open surgery. However, this procedure requires good endoscopic experience on the part of the surgeon and is beset with technical challenges and therefore should be performed with utmost care.

Tech Support

Original Source

DOI: https://doi.org/10.3389/fsurg.2023.1084485

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