Abstract: BACKGROUND: At present, fusion surgery must be performed to reconstruct the stability of the cervical spine after anterior cervical corpectomy. However, fusion sacrifices the mobility of the surgical segment of the cervical spine. Simultaneously, many articles report the potential long-term problems such as adjacent segment degeneration in fusion surgery. We have done some research and exploration on the preservation of cervical segmental motor function after anterior cervical corpectomy. Combined with three-dimensional printing technology, we have developed “artificial cervical vertebrae-intervertebral disc complex”, referred to as the motion-preserving cervical joint system.  
OBJECTIVE: To explore the short-term clinical effect of three-dimensional printing motion-preserving cervical joint system implantation in the treatment of two patients with cervical spondylotic myelopathy.
METHODS:  In view of the loss of motor function of cervical spine segments and the degeneration of adjacent segments after traditional anterior cervical corpectomy operation, in December 2020, a self-developed three-dimensional printing motion-preserving cervical joint system implantation technology was used to treat two patients with cervical spondylotic myelopathy. The patients were followed up for 16 weeks at the time of submission (april 2021). Visual analogue scale score and JOA score were used to evaluate the patient’s pain and neurological recovery at 1, 6, 12, and 16 weeks after the operation. Imaging techniques such as dynamic position X-rays and three-dimensional CT were used to evaluate the position of prosthesis and the preservation of cervical spine motion function. The occurrence of surgery-related complications was observed and recorded during the patient follow-up period. This study was approved by the Ethics Committee of Xi’an International Medical Center Hospital (approval No. 202012).  
RESULTS AND CONCLUSION: (1) The pain and numbness of the two patients were significantly reduced the next day after the operation, and the muscle strength of the limbs was partially restored. (2) At 1, 6, 12, and 16 weeks postoperative follow-up, the patient’s limb muscle strength, visual analogue scale score, and JOA score were significantly improved compared with preoperatively, and the head and neck movement function was good. During the follow-up, no intra-incision hematoma, recurrent laryngeal nerve injury, esophageal injury, cerebrospinal fluid leakage, incision infection, or screw loosening occurred. (3) At 1, 6, 12, and 16 weeks postoperative follow-up, X-ray examination showed that the cervical spine physiological curvature was well restored, and the intervertebral height was maintained well. 3D-CT showed that the prosthesis components and the cervical spine bones were in good fit. The dynamic position X-ray showed that the prosthesis endplate component had a certain angle of opening and closing changes during flexion, extension and lateral flexion, and there was no cervical spine instability, indicating that the prosthesis retained part of the cervical spine motion function. (4) It is concluded that motion-preserving cervical joint system can retain the function of intervertebral movement on the basis of reconstructing the stability of the cervical spine.

Key words: motion-preserving cervical joint system, cervical spondylotic myelopathy, anterior cervical corpectomy, cervical fusion, non-fusion, 3D printing, ceramic surface, adjacent segment degeneration