**8. Conclusion**

Overall, there were only minor differences between devices in terms of overall clinical and radiographic outcome. Significant improvements in clinical outcomes were seen with all evaluated devices, regardless of make or design. An average maintenance of motion postoperatively was described, along with relatively low rates of revision. Differences between devices were mostly apparent in complication types: one potential complication for devices with keels was vertebral body split, while devices with metal-on-metal designs could cause metallosis and ion release in the serum. As for metal-on-poly devices, degradation of the polymer core was also mentioned as a potential complication, albeit one that is not relevant for the current metal-on-poly devices. Specific emphasis was found in most of all publications on proper technique and patient selection, regardless of implant design. Finally, arthroplasty was found to be less costly than fusion.
