The stability of the spine and the exposure of the mass are a delicate balance for surgeons. Total single and/or multi-level laminectomy/laminotomy has been widely used for the resection of spinal lesions, since full exposure of the cord and tumors could be achieved. However, the disadvantages of laminectomy/laminotomy are related to the destruction of the bilateral paraspinal muscle and removal of the posterior spinal elements, which may cause more postoperative complications and spinal instabilities [8].
Recently, hemi-laminectomy with microsurgery has become a promising technique for the treatment of a number of spinal tumors. This approach preserves the spinous process and its base, as well as the contralateral lamina, including ligamentum flavum and muscle [9]. Nevertheless, surgical reports demonstrated its preferred use for small and laterally located masses. Several previous studies have attempted to improve various aspects of bone work required during hemi-laminectomy to gain more exposure for the tumor resection [3, 9, 10].
With emerging state-of-the-art technologies, at the current era, endoscopic surgery is considered to have a higher resolution and definition view than previous decades [11]. These advances accompanied with the flexible placement through surgical corridor allow surgeons to have more direct angles and clearer display to identify the important structure and the nerve-tumor interfaces. These changes may not only improve the tumor resection, but also reduce the residual tumor [12, 13].
In this consecutive endoscopic surgery for ventrolaterally and ventrally located tumors, with a limited removal of the articular process, the tumor exposure is facile. By using a 45-degree angle endoscope, the contralateral side of the spinal canal could be visualized with little hindrance, as well as removing the ventral tumor from one side to the other under a wide and direct view. Hence, the manipulation or traction of the spinal cord could be reduced as much as possible. Moreover, by adjusting the placement angle of the endoscope under an open surgical field, the lesion could be closely observed from different orientations (Figure. 3). This might be helpful to find nerve-tumor interface under a more direct angle and avoid unnecessary damage to the nerve. A widely open endoscopic view using bimanual technique would also help surgeons reach the ventral dura mater, where meningiomas originate.
For large tumors located posteriorly to the spinal cord, laminectomy was taken as an appropriate choice into account compared with hemi-laminectomy, because operations under the latter approach might not have a favorable view to the contralateral part of the canal, which might cause damage to the nerve during the tumor dissection. In our procedure, with partial resection of the base of spinous process, the wide-angle view of the endoscope can be placed directly up to the tumor that is posterior to the spinal cord and provides a full-view (Figure. 2A).
In terms of decreasing residual tumor, Al-mefty et al. reported that the subsequent use of an endoscope could effectively help to find out the tumor remnant and increase the total resection rate in brain tumor surgery [13]. In surgeries of the present study, after tumor removal, we observed the canal from multiple directions by adjusting the placement angle of the endoscope as we performed in the tumor resection procedure to indicate whether there is residual tumor. As a result, in our short-term follow up, no tumor recurrence was noted.
According to the postoperative MRIs, in the current research, all the patients had gross total resection of their tumors. In addition, all the patients had a favorable improvement of their pain on the day of discharge. Not only in the perioperative period, while in the late postoperative period, the patients sensed a decrease in pain.
Numerous studies have confirmed the spinal stability of hemi-laminectomy surgery [14-16]. However, some authors have reported their experience in partially or totally removing the articular process for ventral masses, which may threaten the stability of the spine [17, 18]. In our series, with a panoramic view and close-up observation using the endoscope, the resection of the facet joint could be utmost reduced or avoided for a ventral or ventrolateral tumor. A laminectomy for a total dorsal meningioma was also avoided due to the favorable view obtained by the endoscope. The postoperative CT scan images and MRI findings showed that all the patients had neither malformation nor deformity in a short-term follow-up.
In addition, in the current research, we did not use a conventional metal retractor in our procedure due to its stiffness and thickness, which may cause resistance for the endoscope. Alternatively, we used a spring hook fastened to an external fixed mount. With the help of this technique, the endoscope rod can lean directly on the incision margin, allowing a wider angle of inclination for the endoscope to reach the tumor.
The present study contains a number of limitations. This is a retrospective study of a single surgeon’s experience. Meanwhile, we did not set the control groups and compare the postoperatively outcomes and clinical data with hemi-laminectomy under microsurgery or tubular retractor surgery. The length of our surgical incision was not different from general microsurgery, and that was remarkably longer than tubular retractor surgery. Acctually, Our procedure was just a preliminary attempt to use endoscope in removing IDEM tumors in our center. We were trying to find the feasibility of this technique in spinal tumors and not seeking to declare an absolute predominance of this technique comparing with the traditional surgeries under microscope.
For spinal tumor surgery, an adequate exposure is of great important for tumor resection and nerve protection4. Researches in microsurgery through hemilaminectomy have concerned about the exposure of spinal canal by focusing on the points including degrees of lateral bone resection, dentate ligament division, and degree of cord rotation. Although, in general, the traditional microscopic surgeries may be adequate for the exposure of surgical field in dealing with tumors occupying both side of dura sac and/or tumor ventrally located to the spinal cord. Surgeons may extend the bone resection, slope of operation bed, rotate the cord or even use the laminectomy instead to solved the problem of inadequate exposure. These may influence the outcome of the surgery and cause potential risks to functional protection. Our procedure takes the advantage of endoscopic close-up and panoramic visualization to promote the exposure of surgical field. Moreover, the tumor can be observed from different orientations by adjusting the placement angle of the endoscope under an open surgical field (figure 3). Our preliminary attempt was to combine the advantages of endoscopic surgery with better visualization, flexibility of endoscope placement angle, and sufficient space of open surgery to achieve a superior tumor observation, nerve protection, and reduction of residual tumor. This technique may provide a reliable option for such situations when dealing with tumors expending to the contralateral spinal canal, and lesions are involved in multiple levels or a case that requires enough space for surgical manipulations.