Extradural spinal tumors arise from soft or bony tissues in the spine, and account for 60% of all spinal tumors (1). Extradural tumors can cause clinical symptoms related to axial destruction of the bony structure, as well as myelopathy and radiculopathy caused by spinal cord and nerve compression (2). To manage this disease entity, physicians should achieve three goals for diagnosis and treatment: pathologic confirmation, neural decompression, and structural reconstruction (3). With the development of endoscopic techniques and instruments, interest in the unilateral biportal endoscopic (UBE) technique is also growing, because it can easily decompress the bony spinal canal and accommodate all open surgical instruments under endoscopic guidance. However, indications and reports of this technique have been limited to degenerative (4) and infectious diseases (5). In this technical note, we describe a step-by-step procedure of how we biopsied the affected tissue and performed tumor removal, spinal canal decompression, and stabilization using the UBE and percutaneous screw placement techniques in a 72-year-old female patient with dramatic symptom improvement.

After the surgery, imaging showed that the thecal sac was decompressed bilaterally (Figure 5A), and that the retropulsed tumor was subtotally removed (Figure 5B). The patient's bilateral leg numbness improved to a VAS score of 1, and weakness improved on postoperative day 1. The biopsy results showed chondroid material with a blood clot, and the final diagnosis was aneurysmal bone cyst (Figures 5C,D). Following the oncologist's opinion, treatment was completed without adjuvant radiotherapy or chemotherapy. Follow-up radiographs were obtained after 1, 3, 6, and 12 months, and computed tomography (Figure 5E) and magnetic resonance imaging were performed 12 months postoperatively. At the 12-month follow-up, the tumor had not recurred, the spinal alignment was stable, and the patient was asymptomatic.

To the best of our knowledge, this study was the first to apply the UBE and percutaneous screw fixation techniques for extradural tumor treatment. Our goals were pathologic confirmation, spinal cord decompression, and stabilization of the spinal column; all of which were achieved. The patient was satisfied with her dramatically improved clinical symptoms.

A solitary spinal mass with or without symptoms is usually suspected as a primary spinal tumor or metastasis from another organ. Primary non-lymphoproliferative spinal tumors account for <5% of all bony tumors; therefore, spinal metastases are more frequent [60% of all spinal tumors (8)] than primary masses. However, pathologic confirmation is necessary for a solitary mass in the spine without symptoms related to other organs, and surgical treatment should be chosen based on clinical and radiologic findings.

Fine-needle biopsy is recommended for pathologic confirmation when diagnosing a solitary spinal mass without instability (9). However, for a symptomatic spinal canal mass, treatment should be based on clinical symptoms and radiologic instability. For a solitary mass with possible malignancy, total removal with en bloc resection is recommended (10). Because of the invasiveness of this operation, other surgical options such as subtotal resection, intracystic injection, and embolization are recommended in cases of benign pathology, especially for aneurysmal bone cysts (11). Intracystic injection and embolization cannot decompress the spinal canal and may lead to leakage, and symptoms can consequently worsen. Therefore, less invasive procedures with spinal decompression should be pursued for benign masses involving the spinal canal.

The literature on the biportal technique is still limited to treatments for degenerative disease entities, including spinal stenosis decompression, herniated disc removal, and interbody fusion for instability (12). The advantages of the biportal technique compared with other techniques include shorter hospital stay and less postoperative back pain based on preservation of the back muscle (13). This technique has strengths in bilateral decompressive laminotomy and flavectomy, because free movement of the scope is easy and possible on the contralateral side of the thecal sac. Compared with the uniportal technique, the biportal technique allows for insertion of various surgical instruments without limitations of the cannula, and bone and tissue removal is easy. With extradural tumors, the UBE technique allows for decompression of the spinal canal with various surgical instruments and safe removal of a tumor by utilizing a high-definition imaging system.

Percutaneous screw stabilization for metastatic spinal tumors involves a short operative time, minor intraoperative bleeding, and a short hospital stay (14). Without muscle dissection, accurate placement of the pedicular screw is possible with a small incision. A recent system can insert rods without needing additional incisions; therefore, this technique has become easier. Placement is not limited to tumors and areas of trauma in degenerative spinal diseases (15). Extradural tumors or trauma injuries with spinal cord compression are possible indications for this procedure. Hospital stay was only 2 days with both endoscopic techniques, and postoperative opioids were not administered. Accordingly, medical costs can also decrease. However, there are reports of percutaneous screw fixation without fusion material showing low fusion rate compared with the fusion technique (16). Therefore, indications for percutaneous screw fixation should be considered elderly and short level involvement only (17).

There are certain points that surgeons should consider. The incision should be wider than that in degenerative surgery. The authors recommend that each hole be 1 cm and that the rod insertion site be at least 2 cm. A relatively larger incision can help surgeons identify bleeding and allow for more efficient tumor removal and screw and rod insertion. Unclear vision can prolong the operation time and water retention in the soft tissue. If bleeding occurs during the procedure, bone bleeding should be controlled using an RF coagulator or bone wax. If bleeding focus is not clear, prothrombin hemostatic matrix and compression are useful options for solving the problem (18).

Our technique has some limitations in terms of its broader application. First, a mass suspected to be malignant in radiology should be totally removed. Second, the endoscopic technique cannot expose a wide range like the microscopic technique, and tissues can be lost due to continuous water irrigation. More case evaluations involving this technique are needed, even with its limited indications. Additionally, prospective, multicenter case studies are essential for evaluating outcomes associated with this technique. With the continuous development of new techniques and comparisons with other techniques, it is necessary to evaluate outcomes further.

In conclusion, we described a biportal technique for spinal canal decompression, tumor removal, and biopsy, as well as a percutaneous stabilization technique. With the development of instruments and surgical techniques, our combined technique will play a role in spinal oncology.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by University Hospital Sharjah Institutional Review Board. The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

S-kK: conceptualization, resources, writing (original draft preparation), writing (review and editing), visualization, and project administration. H-aK: methodology. E-jH: software and investigation. RB, S-kK, and S-cL: validation. MA: formal analysis. S-cL: data curation and supervision. All authors have read and agreed to the published version of the manuscript. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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