Functional spine surgery
As we all know, ACDF has become the standard procedure for many years for the treatment of CIVDH 2,4,5. However, complications related to intervertebral fusion were also well-known 6,7,9,10. As a functional spine surgery, anterior transcorporeal herniotomy owns some advantages as follows 20–23,25,28. First, it is less invasive to disc because of the different surgical approach; there will be no injury if the lesion locates behind the vertebral body rather than disc space. Second, it can preserve the mobility of cervical spine and decrease the burden of adjacent discs. In this study, we combined these advantages of anterior transcorporeal approach and endoscopic system together to perform PEATCD with channel repair for patients with single-level central or mediolateral soft CIVDH.
Before this study, we have reported the follow-up outcomes of PEATCD without channel repair and acquired excellent clinical efficacy 32. In order to achieve a better surgical vision and further guarantee adequate decompression, especially for some broad-based herniation, we created the bony channel with a diameter about 8 mm, which is relatively larger compared to the previous literatures 21,25,28,32. According to previous study, the stress on the drilled vertebra was positively correlated with the channel diameter. And the risks of bone fracture would increase significantly when the channel’s diameter was over 8 mm (with partial endplate excision) 33. In this study, we repaired the channel with autogenous bone plug harvested by trephine with a view to the risk of collapse, which greatly promoted the healing of channel according to the radiological results and relevant literatures 21,32. Before grafting, properly shortening to the implant was necessary in order to preserve spinal cord from oppressing. And the parallel relationship of the anterior surface of vertebra and repaired bone must be verified visually under endoscopy. The details about how to shorten the bone plug were depended on the sagittal diameter of the drilled vertebral body on preoperative CT images or lateral cervical plain radiographs. In our study, all the bone plugs were shortened by 1/4 to 1/3.
Overall the surgical process, the potential vascular injury, esophageal perforation, or spinal cord injury was worrisome. Two-finger technique was first adopted to pull aside the esophagus and vessels, which could create a safe area for inserting K-wire into the anterior surface of target vertebra. Iohexol contrast agent, which was injected into gastric tube before location, could sufficiently delineate the esophageal tract under C-arm fluoroscopy. Subsequently, we could determine whether the esophagus was impaled by K-wire through observing the relative position of K-wire and esophagus under C-arm. Additionally, ultrasonic examination was also helpful for surgeon to confirm the safety of operating area if the carotid pulsation couldn’t be palpated clearly with two-finger technique. Based on our limited experiences, the channel’s entrance should be as close to the center of the target vertebra, which could avoid damage to the longus colli muscle and reduce intraoperative soft tissue bleeding, potential postoperative heamatoma, and the incidence of cervical sympathetic nerve injury because of the position of the nerve along the lateral border of the longus colli muscle. Besides that, it should be as close to the inferior endplate of the drilled vertebra, which could make less damage to the superior endplate during trephination.
Establishment of an unobstructed bony channel
Intraoperative trephination must be attentive and its depth should be dynamically monitored by C-arm. The posterior border of drilled vertebra was the terminal of trephination. The trephination deeper, the higher risk of spinal cord injury. However, the bone plug would not be taken out together with the trephine if the trephination was not deep enough. If the bone plug fails to come out with the ﬁrst attempt, under no circumstances should the surgeon try to repeat the dislodging procedure, which greatly increased the risk of spinal cord injury. In such cases, endoscopic system was installed and the channel was drilled visually with high-speed diamond at the previous drilling area, which was created with trephine. It was forbidden to take out the bone plug directly and violently with forceps under endoscopy because of the possibility of tearing the dura.
In endoscopic anterior cervical surgery, the medial retraction to soft tissues with substantial pressure is unnecessary, which would greatly decrease the incidence of dysphagia and injury of recurrent laryngeal nerve. In this study, no other surgery-related complications were recorded except for the swollen neck in 5 patients, which disappeared within 2 hours without any sequela. According to our observation, this complication in the 5 cases was attributed to the lengthy operating time under continuous irrigation (>60 min). For patient with swollen neck, close observation was necessary in postanesthesia care unit until the edema was disappeared and the patient was completely awake with autonomous respiration. And during the observation period, close attention must be payed to identify edema or heamatoma through monitoring whether the swell was further exacerbated. Besides that, the drip stand height in all operations was controlled between 60 cm to 70 cm and extra perfusion pressure was forbidden during the process of endoscopic manipulation in case of mediastinal effusion 34.
Strict indications for patients with CIVDH were crucial in PEATCD with channel repair. In this study, all the patients were diagnosed with single-level central or mediolateral soft CIVDH. Patients with lateral CIVDH or foraminal stenosis were more suitable for posterior endoscopic operation 17,29,35,36. Different with anterior endoscopic transdiscal cervical discectomy, limitation from IDH (>4mm) or anterior osteophytes was not applicable for the implementation of PEATCD with channel repair because this technique was conducted through the bony channel rather than disc space. However, posterior osteophytes or calcific herniated disc was excluded because of the possibly unsatisfactory surgical effect 21. Patients with severe obesity and short neck were also excluded for the difficulty palpation of carotid artery. The location of operated level was also important for operation. Intraoperative manipulation may be obstructed by the mandible if the herniation was at C2-C3 segment. As the clavicle may impede the operation at C6-C7 segment. Based on our limited experiences, the best indication for PEATCD with channel repair was the patient with single-level central or mediolateral soft CIVDH at the levels from C3-C4 to C5-C6 and without spinal canal stenosis or posterior osteophytes.