[Impact of anterior cervical fusion surgeries on adjacent segments: a finite element analysis].

OBJECTIVE: To investigate the changes in the range of motion (ROM) and stress of the intervertebral disc and facet joint of the adjacent segments following anterior cervical corpectomy and fusion (ACCF) and anterior cervical discectomy and fusion (ACDF) using finite element analysis.

METHODS: A three-dimensional finite element model of the lower cervical vertebrae was constructed and validated by comparing the ROM of the finite element model against the published data. After the validation of successful modeling, finite element models of ACDF and ACCF were constructed. The ROM and the stress of the intervertebral disc and facet joint of the adjacent segments were compared between the intact lower cervical vertebrae and the cervical vertebrae after ACDF and ACCF.

RESULTS: The ROM of the finite element model was consistent with the published data. The total ROM and the ROM of the fusion segments with ACDF and ACCF were significantly decreased compared with the intact cervical vertebrae. In the adjacent segments following ACDF and ACCF, the ROM the adjacent segments and the stress peak of the intervertebral disc and facet joint all increased obviously compared with those of intact cervical vertebrae.

CONCLUSION: After fusion surgeries, the total ROM of the cervical vertebrae decreases and the ROM of the adjacent segment increases. The stress peak of the intervertebral disc and facet joint of the adjacent segments also increases to significantly alter the physiological characteristics of the intact cervical vertebrae.