Effect of ACDF combined with different degrees of partial resection of uncovertebral joints on cervical stability and degeneration: a three-dimensional finite element analysis

BACKGROUND: To evaluate the influence of the resection of different amounts of the uncovertebral joints on the stability of the cervical spine by comparing and analyzing the stress distribution and peak displacement characteristics of the internal fixation structures and endplates. METHODS: After obtaining the CT data of a 34-year-old male healthy cervical spine, a three-dimensional finite element model was established and verified. The three-dimensional finite element method was used to establish the models of anterior cervical compression fusion and internal fixation surgical implants and anterior cervical compression fusion and internal fixation combined with the partial resection of different amounts of the unilateral or bilateral uncovertebral joints. The models were tested under six working conditions: flexion, extension, left bending, right bending, left rotation, and right rotation. The surgical models were compared regarding the stress distribution of the titanium mesh, titanium plate and screw, and endplate, and the peak displacement of the vertebral body. RESULTS: There were no significant differences in the stress distribution and peak displacement of the vertebral body of ACDF combined with different amounts of uncovertebral joint resection in the states of flexion and extension. However, there were significant increases in the stress distribution and peak displacement of the vertebral body in the states of left and right bending and rotation. In the states of left and right bending and rotation, the stress distribution and peak displacement of the vertebral body were significantly greater in the models with bilateral partial resection of the uncovertebral joints than in the models with unilateral partial resection of the uncovertebral joints. Bilateral resection of the uncovertebral joints by 30–40% and unilateral resection of the uncovertebral joints by 40–50% resulted in the greatest increases in the maximum stress distribution of the titanium plate and screw and the peak displacement of the vertebral body. CONCLUSION: Finite element analysis of the biomechanical changes in the cervical spine showed that anterior cervical compression fusion and internal fixation combined with bilateral resection of less than 30% of the uncovertebral joints or unilateral resection of less than 40% of the uncovertebral joints had little effect on the stability of the cervical spine.