A 76-year-old female initially presented to a primary clinic with bilateral lower leg paresthesia and motor weakness. She received medication and supportive care, but her symptoms did not improve. Despite 6 months of conservative treatment, she developed progressive paraparesis. Neurological examination revealed grade 4 motor weakness on manual muscle testing in hip extension, knee flexion and extension, ankle dorsiflexion and plantarflexion, as well as great toe dorsiflexion. Additionally, the patellar deep tendon reflex was hyperactive. Whole-spine magnetic resonance imaging (MRI) revealed an upwardly migrated thoracic disc herniation at the T10–11 level, predominantly on the left side. Due to worsening gait disturbance and neurological deficit, surgical intervention was planned using a unilateral biportal endoscopic (UBE) approach.

Under general anesthesia, the patient was positioned prone on a radiolucent surgical table. Using C-arm fluoroscopic guidance, the target point was identified at the caudolateral margin of the left T10 pedicle. Viewing and working portals were created approximately 1.5 cm lateral to the target point. Following skin incisions for both portals, serial dilation was performed, and the endoscope and instruments were triangulated at the target site. Bone work was initiated along the isthmus area of the T10 lamina. Following resection of the isthmus and part of the lamina, the caudomedial wall of the T10 pedicle could be exposed. Further removal of the caudomedial pedicle using a high-speed diamond burr provided adequate working space and allowed clear visualization of the lateral and ventral aspects of the spinal cord, corresponding to the region of the upwardly migrated disc fragment. The fragment was carefully removed using a blunt elevator and pituitary forceps. In select cases, particularly when the herniated disc occupied a central portion of the thoracic canal, a 30° endoscope was employed to enhance visualization of the ventral spinal cord, thereby facilitating safe removal of central disc material without the need for direct cord manipulation. After disc removal, meticulous hemostasis was achieved. A drainage catheter was inserted via the working portal, and layered wound closure was performed to complete the procedure. Postoperatively, the patient's neurological symptoms improved significantly (Table 1). Follow-up MRI confirmed complete removal of the herniated disc and adequate spinal cord decompression. Postoperative computed tomography (CT) demonstrated preservation of the facet joint, with no evidence of iatrogenic damage. At both 3- and 6-month follow-ups, the patient's paresthesia continued to improve. Dynamic flexion-extension radiographs showed no signs of postoperative segmental instability.

Thoracic disc herniation is estimated to affect approximately 11%–14% of the general population, although reported prevalence varies widely across studies, ranging from 6% to 40% [1-3]. While the lower thoracic spine is more frequently involved, the majority of cases are asymptomatic and rarely necessitate surgical treatment. In symptomatic cases, however, surgical treatment may be indicated, with the primary objective being adequate neural decompression while minimizing manipulation of the spinal cord. The surgical approach for thoracic disc herniation can vary depending on the location and morphology of the lesion [4,5]. Representative approaches include the posterolateral, lateral, and anterior transthoracic techniques [6]. With advances in minimally invasive spine surgery, a variety of alternative approaches have also been reported [7-9]. An important principle in the surgical approach to thoracic disc herniation is to access and remove the ventral compressive lesion without manipulating the spinal cord. Additionally, preserving the facet joint as much as possible is crucial to avoid the need for stabilization surgery. Historically, thoracic discectomy has been performed via open thoracotomy, which allowed direct ventral access to the herniated disc and facilitated complete decompression without retraction of the spinal cord [10]. Despite its advantages, this approach carries a high risk of pulmonary complications, contributing significant morbidity [11].

To mitigate these risks, posterolateral approaches have been developed, offering an oblique angle of access to the spinal canal while avoiding thoracotomy-related complications [12]. However, these approaches may require extensive muscle dissection and, in some cases, partial rib resection depending on anatomical considerations [13]. As surgical strategies evolve to further reduce soft tissue disruption, the posterior transpedicular approach has gained popularity as a less invasive alternative for addressing thoracic disc pathology [14].

The advent of minimally invasive techniques, particularly spinal endoscopy, has further refined conventional surgical approaches. The traditional transpedicular approach can be effectively modified using UBE. The previously reported transpedicular approach involves partial resection of the inferior and superior articular processes of the facet joint, along with removal of the cranial aspect of the pedicle located below the disc level to gain access [14,15]. However, the facet-preserving modified transpedicular approach spares the facet joint and instead involves partial removal of the pedicle cranial to the disc level.

This technique offers a magnified operative field and enhanced surgical flexibility. By limiting the extent of pedicle resection and ensuring sufficient working space for disc fragment removal, UBE also reduces the risk of iatrogenic instability.

Nonetheless, the UBE approach presents several technical challenges. It requires a high level of endoscopic proficiency, including the ability to maintain a clear visual field and perform precise bimanual instrumentation. Accurate anatomical orientation under endoscopic visualization is critical, particularly for initiating bone work at the correct location and limiting resection to only what is necessary. These challenges are particularly pronounced in upwardly migrated disc fragments, which are rare and technically demanding because of their ventral position and close proximity to the spinal cord. To overcome these limitations, preoperative 3-dimensional-CT scans are used to evaluate the target point and surrounding anatomical structures, particularly the isthmus and any facet joint degeneration or hypertrophy. Axial CT views further assist in determining the optimal lateral distance for portal placement, thereby facilitating precise and safe access during the procedure.

Further studies are warranted to establish the safety, efficacy, and long-term outcomes of this technique, particularly in atypical cases such as upwardly migrated thoracic disc herniations. With continued advances in endoscopic technology and growing surgical expertise, the indications for this technique may broaden and long-term outcomes may further improve in these challenging pathologies.