This retrospective cohort study reveals that N-TLIF does not have better accuracy or clinical outcomes than does NM-TLIF. In this study, the clinical results of 54 patients and the accuracy of 206 pedicle screws were retrospectively analyzed, and it was found that the two different surgical methods could yield excellent screw placement accuracy with the assistance of navigation, and there was no significant difference between them. Both of them can effectively alleviate the symptoms of patients and yield similar clinical outcomes. It is worth noting that the advantages of minimally invasive surgery in NM-TLIF cannot be ignored.
Lumbar degenerative disease is a common disease among elderly individuals. For patients who fail to respond to regular conservative treatment, TLIF is an effective treatment method. It can achieve bilateral intervertebral fusion by entering the spinal canal from one side, and the central canal is not affected in the operation, reducing the occurrence of cerebrospinal fluid leakage. There is no need to pull the nerve root or dural sac to reduce the probability of nerve injury. The contralateral vertebral plate and facet joints are retained, and the upper edge of the vertebral plate, spinous process, superior spinous ligament and interspinous ligament are retained, and these structures have little influence on the stability of the spine 15. MIS-TLIF is a minimally invasive version of TLIF. Compared with TLIF, MIS-TLIF yields the same surgical effect and has the advantages of a smaller incision, less blood loss, less severe soft tissue injury, a quick recovery and a short hospital stay 16.
Computer-assisted navigation can provide a holistic anatomical image of the surgical area through a single scan, prevent repeated fluoroscopy during the operation, and locate and track the relative position of surgical instruments and anatomical structures in real time, thus allowing more accurate fusion cage and pedicle screw placement 17. Intraoperative navigation can reduce the surgical difficulty caused by the small visual field and the difficulty in recognizing anatomical structures during MIS-TLIF surgery, reduce the radiation exposure and health risks caused by repeated fluoroscopic positioning during traditional minimally invasive surgery, and significantly improve the learning curve 18, 19. As with TLIF, intraoperative navigation significantly improves the accuracy of MIS-TLIF pedicle screw placement and reduces intraoperative complications 10, 20, 21. Compared with freehand instrumentation, intraoperative navigation can also significantly improve the one-time accuracy of the insertion of pedicle screws and can be used to prevent injury to the pedicle and surrounding structures from screw reinsertion 22, 23. The purpose of this study was to discuss the effects of two different navigation-assisted surgical procedures, TLIF and MIS-TLIF, especially regarding the accuracy of pedicle screw implantation and clinical outcomes.
With O-arm navigation, the intraoperative screw trajectory image can be seen in real time, thus making the implantation process more accurate and safer in the NM-TLIF group 24, 25. In our study, two methods of surgery involving intraoperative O-arm navigation assistance yielded high accuracy, with no statistically significant difference between the methods (97.3% vs. 96.2%, p > 0.05). The results showed that the accuracy of NM-TLIF was not inferior to that of N-TLIF due to insufficient anatomical standard exposure or other reasons, which was consistent with previous research results 18, 26. Significantly, the absolute accuracy results showed that both axial and sagittal translational errors were greater in the NM-TLIF group than in the N-TLIF group, which verifies our hypothesis at the beginning of the article. However, despite the larger absolute accuracy error at the entry point in the NM-TLIF group, there was no statistically significant difference in the final accuracy of pedicle screw placement between the two groups. This result suggests that there is no direct correlation between pedicle screw placement accuracy and absolute accuracy of the entry point deflection, which is consistent with the results of previous study13. We believe that this finding is because the visualization of navigation can not only be used for planning when using the NDG to find the entry point, but also be used to adjust the trajectory direction when an electric drill is used to obtain the trajectory. Even when the entry point slips slightly because the NDG is not firmly fixed on the bone surface, the surgeon can adjust the trajectory through the screen after the drill bit enters the bone cortex to achieve good placement of the pedicle screws. In view of the fact that the NM-TLIF screw entry point is more likely to be deflected, we suggest that more attention should be paid to the entire NM-TLIF screw setting process, rather than just following the entry point and trajectory of the intraoperative plan, and the screw orientation should be adjusted at any time during screw setting.
According to our results, the advantages of minimally invasive surgery were revealed in this study. In the NM group, the incision length, intraoperative blood loss, postoperative drainage volume, time before ambulation, blood transfusion rate, postoperative analgesia rate and hospital stay time were significantly reduced. For the clinical outcomes, within at least 12 months of follow-up, the postoperative lumbar pain VAS, lower extremity pain VAS and ODI scores improved significantly in the two groups of patients. There were no significant differences in the intraoperative or postoperative complications between the two groups. Both open and minimally invasive procedures, with the assistance of navigation, can yield consistently good results. However, the use of intraoperative navigation increased the duration of the operation compared with that reported in our previous studies at the same institution 27, which is consistent with the results of previous research 28. According to findings reported by other authors, extra time required for the operation is mainly required for the preparation of the navigation equipment, whereas the screw implant time is dramatically reduced, so the operation process is improved with navigation 29, 30.
In this study, N-TLIF did not yield better screw placement accuracy or better clinical outcomes; in contrast, NM-TLIF seemed to have more advantages. NM-TLIF not only has the above advantages of minimally invasive surgery but also causes significantly less damage to the surrounding spinal muscle tissues than does N-TLIF, and NM-TLIF is superior to N-TLIF regarding long-term muscle tissue recovery. Serban, D. et al. 31 divided patients into a standard TLIF group and MIS-TLIF group. The results showed that the magnitude of improvement in the ODI score from before to after surgery was statistically significant in both groups and similar between groups. The two techniques provided similar clinical and radiological outcomes at 1 year. The patients undergoing MIS-TLIF had a shorter hospital stay. Their results are similar to ours. This finding also demonstrates the advantages of MIS-TLIF.
Radiation exposure during surgery has always been the focus of spinal surgeons. The use of intraoperative navigation can reduce the radiation exposure of patients and surgeons, as has been reported in previous articles. Araiza E.T. et al found that screw placement with the C-arm exposed the surgeon to a significantly greater amount of radiation (3.87 × 10 rads vs. 0.32 × 10, P < 0.001), while the O-arm exposed the cadaver to a significantly greater amount of radiation (0.03 vs. 2.76 rads, P < 0.001) 11. In our study, the levels of radiation exposure to the patients, surgeons, and operating room staff members were not specifically discussed because all patients underwent a complete O-arm CT scan. All patients strictly followed the same procedure for pedicle screw implantation, and no patients underwent a second CT scan due to navigation accuracy problems, so we assumed that the radiation dose was approximately the same between the two groups. The surgeon and the operating room staff members leave the operating room during CT or X-ray scans, so in our opinion, the level of radiation they are exposed to is negligible, but the patient might be exposed to more radiation 32, 33.
The main limitations of this study are as follows: this study was a retrospective study, with a low level of evidence and the possibility of selection bias. No previous studies have compared the levels of radiation exposure specifically across different methods, and only a general assessment of the differences in relative radiation between the prescribed procedures was reported, but the absolute value could not be obtained or compared with those of other methods. Prospective randomized controlled studies with larger sample sizes should be carried out in the future to overcome the limitations of existing studies.
Advancements in both minimally invasive surgery and navigation technology will lead to improvements in lumbar fusion surgery in the future. In the future, navigation technologies should have improved accuracy and lower levels of image drift, and severe complications caused by imaging errors should not occur. Furthermore, the operation process should be optimized, the efficiency of navigation surgery should be improved, the operation time should be shortened, the cost to use the navigation system should be reduced, and the method should be used more widely. In addition, it is also necessary to carry out multicenter, large-sample prospective research studies to obtain a high level of evidence.