Abstract:Objective Cervical disc herniation (CDH) is one of the common orthopaedic diseases. With the in-depth study of it and the development of cervical implants, the establishment of cervical fusion animal models has become an indispensable part. At present, there are few reported researches about the establishment and evaluation of cervical fusion animal models in China. The aim of this study is to provide a good animal model and evaluation scheme of implants for cervical spine-related research. Methods Small tailed Han sheep were chosen for anterior cervical discectomy fusion (ACDF) after modified operation and polyetheretherketone (PEEK) interbody fusion cage (Cage) (control group), 3D-printed Ti6Al4V Cage (experimental group 1) and new method Ti6Al4V Cage (experimental group 2) were implanted in different cervical segments (C2/3-C4/5) of each sheep respectively. After surgery, hematology and histopathological analysis were performed to evaluate the recovery of sheep and the biosafety of the materials. X-ray, CT, Micro-CT and quantitative analysis, hard tissue section staining and biomechanical tests were executed to assess the conditions of bone in-growth and bone fusion. Results The modified ACDF ovine model was established successfully. There was no significant difference in the important indexes of hematology (P< 0.05), and histopathological analysis showed there were no pathological changes such as inflammatory cell infiltration. The implants had a good biosafety..Furthermore, X-ray and CT showed the position of internal fixation and the interbody fusion were good. The results of Micro-CT and quantitative analysis at 3 and 6 months after operation showed that compared with PEEK Cage group, the bone volume/total volume and trabecular number in the new method Ti6Al4V Cage group and 3D-printed Ti6Al4V Cage group were significantly increased (all P < 0.01), while the trabecular spacing decreased significantly (all P < 0.01). Moreover, the new method Ti6Al4V Cage group had more bone growth (P < 0.01). Hard tissue section staining demonstrated that the pores of the new method Ti6Al4V Cage and 3D-printed Ti6Al4V Cage had obvious bone growth and were relatively dense, and the combination was slightly better than that of PEEK Cage. Biomechanical evaluation indicated that compared with PEEK Cage, the new method Ti6Al4V Cage and 3D-printed Ti6Al4V Cage reduced the range of cervical flexion-extention , lateral bending and axial rotation to a certain extent (all P < 0.05), at the same time enhanced the stability of cervical vertebra, and the new method Ti6Al4V Cage was more advantageous (all P < 0.05). Conclusions After the establishment of the modified ACDF ovine model, reasonable and effective assessment methods were used to demonstrate the rationality and effectiveness of the model, and good biosecurity of the Cages of the three materials. Compared with PEEK Cage, the new method Ti6Al4V Cage and 3D-printed Ti6Al4V Cage had better performance in bone growth and bone fusion, which could enhance the stability of cervical vertebrae, and the new method Ti6Al4V Cage had more advantages.