## 5 Conclusions  
In the present study, dynamic cervical spinal loading pattern after spinal fusion, including CF, SF, and FJF, was computed by an established cervical spine MSK MBD model with C5-C6 fusion. The spinal load sharing ratios and joint internal motion at adjacent segments were also obtained. The main conclusions can be summarized as follows:  
1. The spinal loading pattern after fusion presents a distinctly level-dependent feature, where differences in joint loading between the FS and the NS were found.
2. Based on the predicted results, the maximum CF of the FS was about 25% greater than that of the NS in the head extension phase. This phenomenon indicates that the disc would bear more loads during the head extension after spinal fusion.
3. In the head flexion phase, the same magnitudes and trends of the CFs were found, while the increments of the average CFs of the FS were mostly greater than those of the NS at the superior adjacent segments.
4. At the superior adjacent segments, there were minor variations in the A-P SFs between the FS and the NS, in addition to an obvious increase at C4-C5. At the inferior adjacent segment, the spinal fusion altered the direction of the A-P SFs.
5. Larger increases in FJF s at adjacent segments were found after fusion. The results indicated that the facet joint after fusion would share more spinal loading and even lead to facet joint degeneration.
6. Regarding the translations of ICRs, the predicted results showed that the joint internal motion during the head F/E movement might not be affected by single-level cervical spinal fusion surgery. These differences after spinal fusion could contribute to an understanding of the etiology of postoperative ASDs after spinal fusion, from a purely biomechanical perspective.  
Conceptualization, H.D. and Z.J.; methodology, H.D.; software, H.D.; validation, H.D. and H.X.; formal analysis, H.D.; investigation, H.D.; data curation, H.D.; writing--original draft preparation, H.D.; writing--review and editing, H.D., H.X., and Z.J.; visualization, H.D.; supervision, H.X. and Z.J. All authors have read and agreed to the published version of the manuscript. This research was supported by the Hebei Natural Science Foundation, grant number E2023210095.  
Not applicable.  
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