CSM pathogenesis originates from degenerative disc diseases that lead to increased facet stress, followed by osteophyte formation4. The mechanism of osteophyte formation remains elusive. Continuous abnormal movement also causes local inflammation and may lead to osteophyte formation[18]. CSM is usually caused by the backward protrusion of osteophyte and disc, which reduces the sagittal diameter of the spinal canal. Thus, the spinal cord or its blood vessels become directly compressed, resulting in compression or ischemia of corresponding segments of the spinal cord, followed by spinal cord dysfunction, and corresponding clinical signs and symptoms[19]. CSM symptoms are mostly related to the disc-osteophyte complex compressing the spinal cord[5, 20]. Surgical treatment aims to completely remove the compression of the disc-osteophyte complex on the spinal cord and restore normal physiological curvature, which ultimately helps in restoring spinal cord function and preventing disease development or deterioration[21, 22].
Completion of protruding disc-osteophyte complex resection is an essential reference index for evaluating the curative effect of the operation. In sagittal MRI images, some scholars suggested that the connecting line from the midpoint of the posterior edge of the upper vertebral body to the midpoint of the posterior edge of the lower vertebral body at the diseased segment represents the standard line, and the distance between the standard line and the disc-osteophyte complex is the size of the disc-osteophyte complex[20, 23]. Nevertheless, the disc-osteophyte complex is a three-dimensional structure and a single dimension cannot accurately evaluate its size. Based on the measured height, width, and depth of the disc-osteophyte complex, we should estimate its size relatively accurately. MRI can directly reveal the location and severity of spinal cord lesions, but it is not sensitive to bone cortex[3, 24]. Yu et al.[25] indicated that CT images can fully identify osteophyte and calcified disc. Using the most apparent CT sagittal plane of disc-osteophyte complex, the distance between the connecting line from the posterior upper edge of the upper vertebral body to the posterior lower edge of the lower vertebral body at the diseased segment and the upper and lower intersection of disc osteophyte complex can be determined as its height. MRI clearly reveals the protruding morphology of the disc and its relationship with the dural sac, nerve root and other surrounding tissues[26], thereby making this the most accurate method for clinically evaluating the integrity of the disc[27]. In terms of CSM patients, the spinal cord is usually most compressed at the protruding disc. In this paper, we measured the width and depth of the disc-osteophyte complex using MRI images. The size of the disc-osteophyte complex removed during operation was similar to that measured before operation. Therefore, the height, width, and depth of the disc-osteophyte complex measured by imaging accurately reflected its size and compression degree, providing a vital reference for the surgery.
Although the disc-osteophyte complex sizes in this study were different, most were within 10.5 mm in width and 10.6 mm in height, based on imaging. The diameter of the bony passage designed prior to the operation was about 6.9 mm, and it was directed toward the anterior lower edge of the lower vertebral body of the diseased segment oblique to the center position of the disc-osteophyte complex. 28 patients successfully completed the operation in this study. This involved the complete removal of the disc-osteophyte complex. Although the size of the bony passage was only 6.9 mm, its decompression range height and width reached 10.5 and 11.7 mm, respectively. Thus, the disc-osteophyte complex in patients with common CSM can be removed. This is because the direction of the designed bony passage is inclined, and the decompression range is expanded and the damage to disc is reduced by rotating and adjusting the position during operation. At the last follow-up, the clinical effect was valid, without any surgery-related complications. The clinical outcome was similar to that reported in the treatment of CSM patients using anterior disc resection and fusion[6]. The results indicated that this operation offered the advantages of short hospital stay, less trauma, less bleeding, rapid postoperative recovery, and less influence on patients’ cervical mobility.
With the continuous improvement of endoscopic and surgical instruments, the indications of a fully-endoscopic surgery are ever expanding[16, 28]. Chen et al.[29]performed fully-endoscopic anterior transcorporeal cervical discectomy to treat cervical disc herniation. During the postoperative follow-up, the bony passage healed completely and the spinal cord was fully decompressed. Du et al.[30]also performed fully-endoscopic transcorporeal procedure to treat cervical disc discectomy. All patient symptoms were significantly improved and the bony passage healed well, without any surgery-related complications. Similarly, there were no signs of hematoma, nerve root injury, or incision infection in the 28 CSM patients treated with APFETDS in this study. Postoperative reexamination of the cervical MRI revealed that the spinal cord was basically decompressed. CT scans from one year after the operation showed that the bony passage healed well and X-ray images showed regular cervical spine activity. The bony passage was obliquely directed from the lower edge of the lower vertebrae of the diseased segment to the center of the disc-osteophyte complex. In terms of the sufficient removal of proliferative osteophyte and sufficient decompression of the spinal cord, damages to local tissues were markedly reduced, decreasing the possibility of postoperative cervical instability.
In case of CSM patients who are treated with the fully-endoscopic anterior transcorporeal cervical approach, spinal cord decompression using this system causes less damage to the vertebral body and disc. Moreover, patients received better clinical curative outcomes and damages to normal tissues are greatly minimized. The fully-endoscopic anterior transcorporeal cervical approach reduces the impact on cervical spine mobility and related surgical complications, thereby making this a minimally invasive technique holding significant value. However, this study only conducted this technology to treat single segment CSM patients. Therefore, our relevant surgical indications were limited. With the comprehensive future development of full-endoscopies, we hope that the application of this technology can be further extended to 2–3 segment CSM patients.