INTRODUCTION
Symptomatic thoracic disc herniation is a rare condition, with an estimated incidence of approximately 1 per 1 million people [1]. The anatomy of the thoracolumbar junction, in the clinical setting, usually refers to the region comprising levels from T11 to L2 [2,3]. Thoracolumbar disc herniations frequently present acutely. Although paraparesis and paraplegia may be common manifestations, the presentation may be highly variable.
Given that this region represents a transitional zone between the spinal cord and the cauda equina, neurologic symptoms may be diverse and pronounced. Presentations may include signs of upper and lower neuron involvement, cauda equina, radiculopathy, and even myelopathic features [2].
For patients with symptoms refractory to conservative management, a variety of surgical strategies have been devised. Conventional approaches comprise anterior, posterior, and posterolateral open surgery, which may be associated with significant morbidity [4].
Surgical management at this level may require extensive laminotomies, interlaminectomies, or total facetectomies, sometimes with costotranversectomy, all of which increase the risk of pleural laceration [5,6].
Such approaches may compromise spinal biomechanics and predispose to iatrogenic instability, necessitating secondary fusion procedures. Thoracolumbar junction disc herniations, therefore, present a unique challenge in terms of patient selection, surgical technique, and potential complications. Percutaneous endoscopic transforaminal discectomy (PETD) has emerged as a minimally invasive option, reducing complications while minimizing neural tissue manipulation. Nevertheless, successful outcomes demand advanced technical expertise, meticulous surgical planning, and careful patient selection. In this manuscript, we describe the surgical nuances of PETD for thoracolumbar junction pathologies and share insights into key considerations to optimize patient outcomes.
SURGICAL TECHNIQUE
Preoperative imaging must be thoroughly analyzed to identify the location and type of disc herniation, as well as to assess for calcified components, ossification of the ligamentum flavum, and ossification of the posterior longitudinal ligament (PLL). Magnetic resonance imaging (MRI) is used to plan the surgical approach by determining the optimal entry point, trajectory, and angle of approach. The lateral distance from the midline to the skin entry site is measured on axial MRI by drawing a line from the center of the herniated fragment to the lateral border of the facet joint. At the thoracolumbar junction, this distance typically ranges from 8 to 10 cm.
1. Anesthesia
In our practice, the majority of PETD procedures are performed under intravenous sedation, which is associated with fewer complications than general anesthesia since endotracheal intubation or oral sedatives are not required [7]. Regardless, the final decision on the anesthetic approach is determined by the patient's medical conditions and comorbidities, and by the clinical judgement of the surgical team.
At our institution, procedures are performed using the Stryker endoscopic system, in combination with the Joimax instrument set, with or without an endoscopic high-speed burr. Patients are not routinely monitored with intraoperative neuromonitoring; however, a key advantage of intravenous sedation is the ability of the patient to provide real-time feedback upon nociceptive stimuli or motor dysfunction.
2. Skin Marking and Placement of the Working Cannula
PETD was performed through a transforaminal approach. The incision is guided by fluoroscopy. Local anesthesia is applied under the skin and then along the trajectory of the working cannula. A guide wire is docked at the superior articulating process (SAP) under fluoroscopic confirmation, after which the needle is advanced towards the intervertebral disc [8]. The objective is to avoid injury to the dorsal root ganglion. Discography was performed with injection of a blend of indigo carmine and contrast material, confirmed fluoroscopically. subsequently, a guidewire, dilator, docking port, and a working port are inserted sequentially into the disc space through the intervertebral foramen. Finally, the endoscope was introduced to permit the visualization and treatment of the affected region. This approach provides direct access to the ventral aspect of the dura and PLL, allowing wide resection of herniated discs, dural adhesions, and calcified components while avoiding cord retraction, dorsal root ganglion, or SAP resection [9].
3. Endoscopic Procedure
A T-shaped working cannula was employed, followed by the U-shaped cannula in sequence. The endoscope was then introduced for visualization of the soft tissue inside the intervertebral disc, which was cleaned to expose the anatomical landmarks. The degenerated nucleus pulposus protruding into the spinal canal was removed sequentially in a piecemeal fashion with a standard endoscopic pituitary grasper. A giraffe instrument was used to resect superficial and contralateral disc material. During this step, anteroposterior fluoroscopic guidance was used to assess midline crossing. The calcified portions were debulked by alternating central demassification with a high-speed drill (diamond burr) and dissection of the dura using an endoscopic dissector. A pituitary rongeur was subsequently advanced to extract debris liberated by the drill and any migrated disc remnants. The side-firing holmium:YAG laser proved effective for reducing disc material, performing nucleoplasty, and achieving annuloplasty to reduce recurrence risk.
REPRESENTATIVE CASE
A 47-year-old male presented with sacral and inguinal pain, bilateral lower-limb weakness, (grade 4/5 at hips and knees), and gait impairment. Symptoms persisted despite physical therapy and injections. MRI revealed a left T12–L1 disc extrusion with spinal cord compression (Figure 1). The computed tomography (CT) scan revealed calcified elements (Figure 2). After multidisciplinary discussion with the senior author (KSM), the patient was scheduled for a left-sided PETD.
Postoperatively, the patient experienced marked improvement: pain initially decreased to 5/10, then the sacroiliac pain resolved a few hours after surgery. Surgical duration was <1 hour. He was discharged home on postoperative day 3. At outpatient follow-up, he reported improved lower-limb strength, high satisfaction with the procedure, and independent ambulation restored 1 month after surgery. The postoperative MRI revealed complete decompression of the spinal cord (Figure 3).
DISCUSSION
The thoracolumbar junction comprises the T12 and L1 vertebrae in the anatomic definition, but the biomechanical vulnerability is presented from the T11 level, where the free-edged ribs are already present, and patients may present with individual anatomical variations of the location of the caudal end of the spinal cord, making the thoracolumbar junction to be clinically considered from T11 to L2 [2].
The adoption of endoscopic spine surgery has been driven by its advantages, including minimal invasiveness, reduced postoperative pain, and accelerated recovery. Favorable outcomes have been documented even in cervical and thoracic applications. Economically, PETD demonstrates superiority compared with microdiscectomy: direct costs ($6,210 PETD vs. $7,410 MD, p<0.01), indirect costs ($1,200 PETD vs. $1450 MD, p<0.01), and total costs of surgery ($7,520 PETD vs. $8860 MD, p<0.01) [4]. These savings are likely to reflect less operative time, equipment cost, and disposable costs. On the other hand, minimal damage to the surrounding tissues results in faster recovery and less pain, translating into shorter hospital stays [10].
Two principal endoscopic approaches are used to treat thoracolumbar pathologies: transforaminal and Interlaminar [11]. The transforaminal route is the most common method applied in endoscopic spine surgery for discectomy [12]. Within the transforminal approach, various techniques have been developed, including the “inside-out” technique (initiated intradiscally), and methods including additional bone resection to enlarge the foramen, thereby improving visualization post-discectomy by resecting the ventral SAP [9,13-15]. Current consensus emphasizes tailoring the endoscopic trajectory to the pathology through a safe corridor. In this approach, a far lateral incision enables instrument passage through the extraforaminal and lateral foraminal zones of Kambin triangle [16,17].
Endoscopic techniques preserve bony anatomy and facet joints in a more efficient manner than traditional open procedures [12]. In contrast, conventional thoracic approaches often necessitate aggressive rib and soft-tissue resection, with risks of pulmonary/pleural injury and prolonged intensive care stay [18].
A meta-analysis conducted by Silva et al. [19] including 13 studies confirmed that outcomes after full-thoracic endoscopic spine surgery have an acceptable safety profile, with low pooled incidences of dural tear (1.3%), dysesthesia (4.7%), recurrent disc herniation (2.9%), myelopathy (2.1%), epidural hematoma (1.1%), and reoperation (1.7%).
Indications for this approach include recurrence of a herniated disc at the same spinal level or the persistence of radicular symptoms following a previous surgery performed through a different approach. It is also suitable for complex spinal pathologies at the thoracic and upper lumbar levels. PETD is especially effective for treating paramedian and foraminal disc herniations. Central herniations may also be addressed with this approach, but may require a higher level of surgical expertise owing to technical difficulty.
Limitations of the transforaminal approach include central stenosis caused by ligamentum flavum hypertrophy or facet overgrowth, and the anatomical barrier of the iliac crest restricting access to lower levels (L5–S1). At T12–L1, the last floating rib may pose similar constraints. Careful review of preoperative imaging is therefore essential.
This approach should be avoided in severe multilevel deformities, diffuse calcification/ossification not amenable to endoscopic drilling, high-grade spondylolisthesis, severe central stenosis, or suspected systemic/uncontrolled local infection.
Obesity is not an absolute contraindication, but requires tailored planning: an appropriate operating table, larger instruments, and an individualized setup.
We recommend limiting surgical time to < 1 hour to reduce intradural pressure elevation from continuous irrigation. Irrigation is maintained at 30 mmHg with low flow.
Special attention must be given to the anterior radiculomedullary artery (artery of Adamkiewicz), which traverses the neural foramen in ~46% of patients. It is located above L3 in most cases, 88% on the left side, and often at the superior aspect of the foramen [20]. Thorough preoperative planning, judicious patient selection, and surgical expertise are critical ensuring safety.
The advantages of PETD include preservation of spinal stability and avoidance of extensive neural manipulation.
Postoperative pain is reduced, segmental motion is preserved, and recovery is accelerated.
Patients should be counseled regarding the possibility of recurrent herniation.
CONCLUSION
Successful outcomes require meticulous surgical planning and advanced technical skills, heightening the need for expertise in this innovative field. The use of endoscopic techniques, as demonstrated in this case, offers a viable, minimally invasive, motion sparing and efficient alternative to traditional open surgeries for anatomically challenging regions. The later highlights the importance of younger generations of spine surgeons to undergo specialized training in advanced endoscopic spine surgery.
WRITTEN TRANSCRIPT
00:00 Introduction
In this video, we will present the surgical technique for a thoracolumbar junction disc herniation in a myelopathic patient.
00:09 Case Presentation
This is the case of a 47-year-old male who presented with both severe inguinal and sacral pain, weakness in both legs, and gait impairment.
00:19 Preoperative MRI
The MRI revealed the presence of a T12–L1 herniated disc on the left side that compressed the spinal cord. A slightly upmigrated portion of the ruptured disc is also visualized.
00:32 Preoperative CT Scan
Further assessment with the CT scan documented a significant calcified portion of the herniated disc, adjacent to the superior L1 endplate. A transforaminal endoscopic approach was considered for this patient's treatment.
00:49 Preoperative Planning
Using the preoperative MRI, the preoperative planning was done, drawing a tangential line from the foramen that intersected a line drawn 10 cm lateral to the midline.
01:02 Rationale of the Procedure
The rationale of the procedure included less need for drilling work, a direct approach to the ventral region’s central lesion, and consequently, no manipulation of the spinal cord was needed, no necessity of injury to the facet joints, thus decreasing the risk of instability and avoiding the need for instrumentation.
01:25 Description of the Setup
The setup used in this case comprehended a 30° endoscope, standard spine endoscopic instruments, the camera, an endoscopic surgical drill, as well as a C-arm fluoroscope. The patient was placed in a supine position, under sedation.
01:43 Key Surgical Steps
The key surgical steps for this procedures are achieving an optimal positioning of the working cannula, establishing an adequate workflow, employing and in-and-out technique maintaining a half and half view to secure a safe working route, drilling the endplate, if necessary to obtain a wider exposure of the ventral epidural space, and finally resection of the osteophyte and discectomy.
02:14 Cannula Insertion – Contact with the Superior Articular Process, Anterior Posterior View
The initial part of the procedure consists of cannula insertion, which must be assessed with a C-arm fluoroscope. Initially, insert the needle from the previously described insertion point, then direct it towards the L1 SAP.
02:32 Cannula Insertion – Contact with the SAP, Lateral View
Then, a lateral view is obtained to ensure the needle tip is in contact with the SAP.
02:41 Insertion of the Needle Into the T12–L1 Disc
Once verified, the needle’s bevel is turned downwards, and the needle is inserted into the disc. A transoperative discography is routinely performed at our institution using an indigo carmine dye.
02:47 Insertion of the Working Cannula Into the T12–L1 Disc
The needle is then replaced by a guidewire, which is employed to sequentially insert the obturator into the disc space, followed by the half cannula.
03:04 Optimal Positioning of the Working Cannula – Anterior Posterior View
The optimal positioning of the cannula should allow visualization of the intradiscal space in one half and the epidural space on the other.
03:24 Division of the PLL
The cannula may be reaccommodated as needed, and then a partial division of the PLL is done to free more disc material.
03:52 Dissection and Resection of the Extruded Disc
The extruded disc is further dissected away from the dural sac with a probe and then resected.
04:06 Endplate Drilling
Partial drilling of the endplate can be performed, as in this case, to reach migrated portions of the ruptured disc.
05:03 Dissection and Resection of the Osteophyte
The calcified portions of the herniated disc are identified and may be removed with the assistance of the surgical drill and the endoscopic forceps.
05:13 Ventral Dura Fluctuations
When adequate decompression is achieved, the ventral dura fluctuations can be properly visualized.
05:21 Drainage Insertion
After removal of the endoscope, a drain is placed through the working cannula, which is then carefully removed.
05:39 Postoperative Period
The patient's symptoms improved immediately after surgery, with the pain decreasing abruptly and then gradually, resolving completely in the medium postoperative period. He was discharged on the postoperative day 3, and was able to ambulate independently 1 month after surgery.
05:59 Key Points
Lastly, the key points for the endoscopic treatment of a thoracolumbar junction disc herniation are:
To be familiar with the anatomy of this specific region, including the assessment of the location of the artery of Adamkiewicz, the end of the spinal cord, and the floating ribs, for preoperative planning.
Elaborate a careful preoperative plan to achieve optimal outcomes.
The use of endoscopic techniques limits the need for dissection, preserves spinal stability, minimizes postoperative pain, and enhances early recovery.
And, like any surgical procedure, it has its limitations, which include severe central stenosis, spinal deformities, or massive calcifications.
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