Abstract: BACKGROUND: Recent clinical studies have found that during the implantation of biomaterials, the internal environment of the body will change to a certain extent, and different levels of immunity and stress responses will occur. There are also obvious differences in the immune and stress responses of different biological materials. 
OBJECTIVE: To investigate the effect of 3D printed interbody fusion cage on patients with cervical spondylosis of spinal cord type and its effect on serum cortisol and norepinephrine levels. 
METHODS: Sixty-three patients with cervical spondylotic myelopathy who were admitted to the Affiliated Hospital of Chengde Medical University from July 2015 to July 2018 were selected, including 40 males and 23 females, aged 30-78 years old. The patients were randomly divided into a research group (n=31) and a control group (n=32) according to a random number table. All patients received anterior cervical decompression and bone graft fusion and internal fixation. Patients in the research group were implanted with 3D printed intervertebral fusion cage during operation. The patients in the control group were implanted with polyetheretherketone interbody fusion cage and allogeneic bone. The operation and complications of the two groups were compared. Serum cortisol and norepinephrine levels were detected before and 1 and 3 days after operation. Cervical curvature and intervertebral height were measured before surgery, 1 week, and 6 months after surgery. Axial symptoms were counted at 6 months after surgery. The trial was approved by the Ethics Committee of the Affiliated Hospital of Chengde Medical University. 
RESULTS AND CONCLUSION: (1) Operation time, intraoperative blood loss and hospitalization time were not significantly different between the two groups (P > 0.05). (2) Among 31 cases, there were 1 case of screw loosening and 1 case of implant movement in the research group. Among 32 cases, there were 3 cases of screw loosening, 3 cases of immune rejection, 2 cases of implant movement, and 1 case of implant collapse in the control group. The incidence of complications was lower in the research group than that in the control group (P < 0.05). (3) At 1 and 3 days after operation, the levels of cortisol and norepinephrine were higher in both groups than those before surgery (P < 0.05), but above levels were lower in the research group than in the control group (P < 0.001). (4) The cervical curvature and intervertebral height at 1 week and 6 months after operation in both groups were higher than those before surgery (P < 0.05), and above indexes were higher in the research group than in the control group (P < 0.05). (5) The axial symptom in the research group was lighter than that in the control group at 6 months after operation (P < 0.05). (6) The results show that the application of 3D printed interbody fusion cage to cervical spondylotic myelopathy can reduce complications, promote the recovery of cervical curvature and intervertebral height, and improve the stability of cervical spine, and the body’s stress response and axial symptoms are mild.

Key words: bone, implant, cervical spondylotic myelopathy, 3D printing, interbody fusion cage, cervical curvature, intervertebral height, cortisol, norepinephrine