After conservative treatment was ineffective, surgical intervention became the first choice [11]. ACDF is the standard surgery for the treatment of cervical degenerative disc disease, which can restore the physiological radian of cervical vertebra to the maximum extent, have high intervertebral fusion rate, maintain the stability of cervical spine, and have remarkable surgical effect [12]. In our study, the postoperative cervical cobb angle of the two surgery was significantly bigger than the preoperative cervical cobb angle, which indicated that both surgery can correct cervical kyphosis. Therefore, the fusion and biomechanical stability of ROI-C are equal to those of ACDF, and satisfactory surgical results of both surgery have been achieved [13]. The results of this study showed that JOA score and NDI score of both groups were improved, and good operation effect was maintained during the follow-up period, which demonstrated that the two surgery can relieve spinal cord and nerve compression, and improve the quality of life of patients.
This study found that the ROI-C has the following advantages: 1. The operation wound is smaller and less bleeding. Although ROI-C surgery can’t reduce skin incision, it is not necessary to consider the placement of plate fixation and extensive exposure of adjacent vertebral body, only need to expose the target intervertebral space, which is convenient for operation. 2. The operation time is relatively short and the operation is simple. In group A, the cage was directly fixed with self-locking clip, which could save operation time. 3. The incidence of dysphagia was reduced after operation. At present, dysphagia is a common complication after ACDF, whose mechanism has not been explained clearly [14, 15]. It may be related to the following factors: 1. During anesthesia, the stimulation of pharynx and trachea may cause dysphagia. Some scholars suggest that atomization after operation can partly relieve dysphagia symptoms. Dysphagia caused by this reason can be recovered within one month. 2. Postoperative soft tissue adhesion may lead to dysphagia. In order to expose the target position, the soft tissue in front of the vertebral body needs to be stripped. In group A, only the intervertebral space needs to be exposed to facilitate the operation, while in group B, the plate fixation is placed in front of the vertebral body, resulting in a wider range of exposure and more bleeding, which increased the possibility of postoperative adhesion. 3.The incidence of dysphagia will be increased by using anterior cervical plate [16]. A large number of clinical studies have shown that after plate fixation is fixed, the plate will protrude from the surface of cervical body, which cause slight compression on the esophagus [17, 18]. Some scholars reported that the use of thinner plate fixation will reduce the incidence of dysphagia [19]. Previous studies have also shown that the use of zero-profile anchored spacer can significantly reduce the incidence of dysphagia. In this study, we found that the ROI-C was completely implanted in the intervertebral space, and there was no compression on the esophagus. The incidence of dysphagia in group A was lower than that in group B. the difference was statistically significant at one month and three months after operation, which indicated that the use of ROI-C can reduce the incidence of early dysphagia.
The effect of ACDF depends on the degree of decompression, the recovery of cervical lordosis and the stability of fusion. Anterior plate fixation is often used in ACDF to improve the speed of interbody fusion and enhance the stability of cage. Only after bone fusion can kyphosis and spinal canal stenosis be effectively prevented, so as to prevent compression of spinal cord and nerve root [20]. Wang et al. [ 21] and Grasso et al. [ 22] reported a fusion rate of 100% in patients with ROI-C who were followed up for 2 years. Hofstetter et al. [ 12] reported that the fusion rate of ROI-C was 95.2% after an average follow-up of 13.9 months. Our results show that the two groups have achieved satisfactory results of bone fusion, and there is no significant difference between the two methods.
So far, the mechanism of adjacent joint degeneration is not clear. It is not only related to the natural degradation of adjacent joints, but also to the increase of adjacent upper and lower joint activities caused by abnormal fusion [23, 24]. Lee et al. [25] believe that the use of short plates with oblique screw tracks can significantly reduce the incidence and severity of ALOD. Many studies have shown that the shorter the plate length, the lower the incidence of ossification of the adjacent vertebral body, which may be related to the separation of the soft tissue in front of the vertebral body [26, 27]. In group A, 3 patients had adjacent vertebral degeneration, and 5 patients in group B had adjacent vertebral degeneration. In the last follow-up, no patient needed surgical intervention. In the future, we will continue to investigate and further evaluate whether the bridge-type ROI-C interbody fusion cage can help reduce the incidence of adjacent vertebral degeneration and the need for reoperation.
Of course, this study also has some limitations: first of all, this study is a retrospective study, and the level of evidence is limited. Secondly, there may be measurement errors. In order to minimize these errors, three orthopedic surgeons measured the X-ray data separately. Finally, the number of cases in this study is small and the follow-up time is short, which may lead to selective bias. In the future, robust randomized multi-center prospective studies with long-term follow-up are needed to confirm these findings.