The Efficacy of ACDF Treatment in Traumatic Cervical Disc Herniation
Traumatic cervical disc herniation is an uncommon injury pattern in general. The aim of surgical treatment is to avoid further damage to the spinal cord, remove compression on the nerve roots and spinal cord, reestablish the cervical lordosis and restore spinal stability5. ACDF has become the standard procedure for the treatment of degenerative cervical disc disease due to direct neural decompression and reconstruction of spinal stability19. ACDF with or without posterior fixation has been proven to be a safe and effective procedure for traumatic cervical injury1,6. In this study, ACDF was used in selected patients who had no bony fracture, severe segmental instability, or kyphotic deformity. Satisfactory clinical outcomes were obtained in almost all patients of both groups. Although cage subsidence were observed in Group ZP (3/27) and Group CP (2/23) at 1 month postoperatively, and 2 of these patients were found with osteoporosis. We considered that osteoprosis may influence cage subsidence, then all these patients were asked to wear a Philadelphia collar for another 1–2 months and receive anti-osteoprosis treatment. None of these patients complained of cage subsidence at 3 months postoperatively, the interbody fusion and clinical outcome were not impact by cage subsidence. Thus, ACDF can be used successfully in traumatic cervical disc herniation without bone involvement.
Safety and Efficacy of Zero-Profile Device in ACDF for Traumatic Cervical Disc Herniation
Zero-Profile device is a new type of cervical integrated intervertebral fusion device consisted of a small titanium alloy plate, polyether-ether ketone (PEEK) cage, and 4 screws for fixing into the vertebral body. The safety and efficacy of Zero-Profile device in ACDF have been demonstrated in previous studies13, 20, 21. Zero-Profile device was also used successfully in singl-level ACDF with osteoporosis as we reported before22. Previous studies have demonstrated that Zero-Profile device used in ACDF not only had a similar radiologic fusion rate and clinical outcomes compared with anterior plate and cage, but also decreased complication rate including dysphagia and ASD20, 21, 23. Zero-Profile device has been accepted as a effective fusion method for ACDF in the treatment of single level and multi-level cervical degenerative disc disease11, 22, 24, 25. In the present study, we also found that ACDF with Zero-Profile device can be used as a safe and effective treatment for patients with single-level traumatic cervical disc herniation.
In the present study, the cervical lordosis, JOA, NDI and VAS scores in all patients of the two groups were significantly improved at final follow-up. Meanwhile, solid bony fusion was observed in all patients at final follow-up. Subsidence of the implant is a normal complication in ACDF with stand-alone cage. It was reported that subsidence often happens at 3 months after surgery, and the subsidence rate ranges from 9.3 to 62.5%25–28. In the present study, cage subsidence rate was 11.1% in Group ZP and 8.6% in Group CP, which were within the range of previous studies. No significant difference was found between the two groups. Igarashi H et al. found that a greater cage height had a higher risk of cage subsidence in ACDF29. Park JY et al. reported that cage location is the risk significant factor for cage subsidence in ACDF, and the cage location within 3 mm from the anterior margin of the vertebral body showed lower incidence of subsidence30. Although previous studies confirmed that cage subsidence does not appear to affect clinical outcome26, 31, it still needs to be evaluated in the long-time follow-up. Although we observed 3 case in Group ZP had cage subsidence, these patients still showed a satisfied clinical outcomes and bony fusion at final follow up.
Wu et al. reported that the improvement of cervical lordosis is more important than the impact of cage subsidence in the long-term study31. A number of studies confirmed that maintenance of cervical lordosis is associated with clinical outcomes32,33. The axial load of normal cervical spine is distributed on the posterior column in the upright neutral position34. Axial load shifts anteriorly as the progress of cervical lordosis loss, which will increase the incidence of implant failure, ASD and even cervical kyphosis8,35. In additionally, insufficient recovery of cervical lordosis after ACDF may result in neck pain, shoulder pain, cervical instability, cord compression, and even poor functional recovery 33,35. In the present study, cervical lordosis were significantly improved and maintained over time at final follow-up in all patients. Therefore, ACDF with Zero-Profile device can obtain similar improvment of cervical lordosis compared with cage and plate.
Solid interbody bony fusion is one of the aims of ACDF surgery, and Kaiser MG et al. reported that bony fusion failure is linked to poor clinical outcomes36. Some studies reported that postoperative kyphotic deformity with concomitant foraminal stenosis can be prevented by solid bony fusion37, 38. A systematic literature review reported that bony fusion rate of 3971 ACDF patients who received cage with plate was 91.4% at final follow-up, and bony fusion rate of 499 patients who received a cage with screws attached (no plate) was 96.6%39. According to the result of our study, there was no statistically significan difference in fusion rate between the two groups at 3 month postoperatively. All patients achieved solid fusion at final follow-up. Consequently, Zero-Profile device can obtain similar bone fusion compared with cage and plate in ACDF for single-level traumatic cervical disc herniation.
Advantages of Zero-Profile Device in ACDF for Traumatic Cervical Disc Herniation
Swallowing dysfunction or dysphagia is one of the major complications after ACDF with anterior plate fixation. Previous studies reported that the incidence of dysphagia after anterior cervical fusion with plate vary from 1–62%9, 40, 41. The dysphagia-related symptoms may be explained by postoperative hematoma, esophageal injury, postoperative soft-tissue edema, and adhesive formations around implanted cervical plate8. It has been found that there is a correlation between plate thickness and dysphagia rate42. Zero-Profile device can be inserted into the intervertebral space, avoiding stimulating esophagus and other pre-vertebral soft tissues9, 20. According to the result of present study, the incidence of postoperative dysphagia in Group ZP was lower than that of Group CP at postoperative immediately, 1 week and 1month, but there were not significantly difference. The reason may be the sample size was small and the included cases were all single segment. Therefore, the application of Zero-Profile device in ACDF may reduce the incidence of early postoperative dysphagia, but further confirmation is needed in more cases and multi-segment cases.
ASD is another complication after ACDF with anterior plate fixation, and the exact pathophysiologic mechanism is still unknown8,16,20. Some scholars believed that ACDF may change the natural history of cervical spondylosis and the plate may increase the motion and intradiscal pressure in the untreated levels adjacent to fused levels43. Meanwhile, the anterior plate close to the adjacent disc may cause adjacent level disc degeneration, and the diatance between plate and cage < 5 mm may reduce the incidence of ASD18. In the present study, the incidence of ASD in Group ZP was 3.7% and 8.7% in Group CP, but the difference between the two groups was not statistically significant. However, a long-time study with more patients should be performed to investigate whether or not the Zero-P device can reduce the rate of ASD.
However, this study still has some limitations. First, it is a single-center retrospective cohort study. Moreover, the sample size was small. Further multicenter prospective randomized studies and larger patient samples are needed to confirm the results. Meanwhile, only single-level traumatic cervical disc herniation was erolled in the present study, whether multi-level segment can influence the complations or clinical outcomes still needed further research.