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

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.

Keywords: case report; central calcified thoracic disc herniation; endoscopic foraminoplasty; flexible endoscopic power drill; fluoroscopic foraminoplasty; minimally invasive decompression; modified PTES (percutaneous transforaminal endoscopic surgery).

Figure 1

Preoperative image examinations (A–G). MR examination done on October 25, 2019, showed a giant TDH at the T11–12 levels: (A) Right sagittal T2WI, (B) middle sagittal T2WI, and (C) left sagittal T2WI. (D–G) CT examination recorded on November 14, 2019, confirmed CCTDH at T11/12: sagittal CT images [(D) soft tissue window; (E) bone window]. Transverse CT images [(F) soft tissue window; (G) bone window]. (H,I) Digital radiograph obtained on November 20, 2019, showed a normal thoracic sequence with no scoliosis. TDH, thoracic disc herniation; T2WI, T2-weighted image; CCTDH, central calcified TDH.

Figure 2

Modified PTES (PTED) to decompress CCTDH on November 22, 2019 (A–I). (A) Skin mark of the index disc's center guided under C-arm fluoroscopy and skin entrance point determination (Gu's point, the point on the marked transverse line where the flat back turns to the lateral side). (B) Subsequently, dilator cannulas were advanced to the anterolateral side of the SAP over the guidewire, which was finally confirmed under AP C-arm fluoroscopy. (C) The protection cannula was inserted over the guide rod (which had replaced the dilator cannulas) to kiss the anterolateral side of the SAP which was confirmed under AP C-arm fluoroscopy. (D) The beveled end of the protection cannula touched closely to the anterior side of the SAP, which was confirmed under lateral C-arm fluoroscopy. (E) The hand trephine firmly caught the lateral portion of the ventral bone from the SAP at the fluoroscopic foraminoplasty step. (F) The bone chunk isolated from the ventral portion of the SAP by the trephine. (G) The trephine's saw teeth under endoscopic visualization when performing endoscopic foraminoplasty. (H) Soft herniated disc fragments ventral to the calcified shell were removed using forceps. (I) Calcified shell was thinned using an electric diamond drill at the flexible position. (J) Ventral surface of the dural sac on the left side was exposed after the removal of the bony disc shell. (K) Dural sac with visible pulsation following complete decompression. (L) Isolated disc fragments with scattered calcification. Pentagram, soft fragments of the herniated disc; Triangle, calcified disc shell; Polyhedrosis, hinge of an electric diamond drill; Arrow, dural sac. PTED, percutaneous transforaminal endoscopic decompression; PTES, posterolateral transforaminal endoscopic surgery; CCTDH, central calcified TDH; AP, anteroposterior; SAP, superior articular process.

Figure 3

Illustration of the manipulation of a flexible power drill (A–D). (A) Calcified disc on the left side was removed using a power diamond drill, while the control handle was in the straight position. (B) Control handle approached anteromedially in a straight position avoiding dural sac disturbance. (C) The distal end of the control handle angled dorsally to remove the calcified shell on the right side (the no-touch technique). (D) Endoscope-assisted resection of CCTDH using a curved dissector from another trajectory (not performed in our patient). CCTDH, central calcified TDH.

Figure 4

Postoperative CT scans taken on November 23, 2019, revealed that the calcified herniated disc was completely removed with some normal bone excessively removed (A,B). (A,B) Transverse CT images of T11/12.