Fig. 1

a The spinous process and lamina and bilateral articular process in affected segment were removed so as to expose the dural sac and intervertebral disc. b The intervertebral space was hollowed out to form an “eggshell,” after the removal of disc tissue within the intervertebral space. c The adhesion between the herniated calcified disc and dura mater was separated by nerve retractor crook or hook knife, and the hardening disc tissue was pushed to the anterior intervertebral space by the reverse angled curette. d Autologous bone graft and a cage were implanted into the interbody for fusion purpose. The pedicle screw-rod system was fixed in situ in order to prevent a slight curvature change after decompression, thereby reducing damage to the spinal cord