Fig. 4
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs12893-019-0502-z/MediaObjects/12893_2019_502_Fig4_HTML.png)
Second operation. a The anterior–posterior radiography image at the second operation. b Sagittal radiography image at the second operation. A long fixation from the occipital bone to C4 was performed. The upper atlantodental interval was 2.8 mm. c Anterior–posterior radiography image at 4 years after the second operation. d Sagittal radiography image at 4 years after the second operation