2024, Vol. 28 ›› Issue (24): 3783-3788

Mechanical analysis of cortical bone trajectory screw placement in lumbar revision

Zhang Lianpeng1, Julaiti•Maitirouzi1, Zhang Zhihao1, Zhang Rui2, Abulikemu·Maimaiti2, Paerhati·Rexiti2   

Abstract: BACKGROUND: At present, there are shortcomings and risks in the surgical revision of vertebral bodies that failed to be fixed in clinical practice. To avoid the risks of conventional revision surgery, the cortical bone trajectory technique is used to perform revision surgery on vertebral bodies that failed to be fixed. However, the mechanical properties of cortical bone trajectory technique screws in revision surgery are not clear.
OBJECTIVE: The mechanical properties of cortical bone trajectory in lumbar revision surgery were analyzed by the finite element method to provide a theoretical basis for the clinical application of cortical bone trajectory in revision surgery.
METHODS: CT scan data of the osteoporotic vertebral body were obtained and the L4 vertebral body model was established. The initial cortical bone trajectory placement and traditional pedicle screw in the L4 vertebral body model were completed, respectively, and their mechanical data were taken as the baseline standard for later evaluation of revision surgical performance. The traditional pedicle screw was removed and the screw path was retained. The cortical bone trajectory screw was used for secondary screw placement on the vertebral body to achieve lumbar refixation. The axial pull-out force, stability, and lumbar motion range of the revised screw were analyzed by the finite element method.
RESULTS AND CONCLUSION: (1) The screw axial pull-out force of the cortical bone trajectory revision group was 25.6% higher than that of the traditional pedicle initial group. (2) In the lower, left, and right working conditions, the load-displacement ratio of screws in the cortical bone trajectory revision group increased by 18.5%, 41.3%, and 35.0%, respectively, compared with the traditional pedicle initial group. The load-displacement ratio of screws in the cortical bone trajectory revision group was slightly higher than that in the traditional pedicle initial group under the above condition, but there was no statistically significant difference (P > 0.05). (3) In anterior and posterior flexion conditions, lumbar motion range in the cortical bone trajectory revision group was increased by 45.5% and 36.1% compared with the traditional pedicle initial group, but there was no statistically significant difference in left bend, right bend, and axial rotation conditions (P > 0.05). (4) There were no statistically significant differences in screw axial pull-out force, screw load-displacement ratio, and lumbar motion range between the cortical bone trajectory revision group and cortical bone trajectory initial group (P > 0.05). (5) The mechanical data exhibited that although the revised nail track bone was damaged or lost to a certain extent, the mechanical properties of the cortical bone trajectory revision group were still better than those of the traditional pedicle initial group to a certain extent. Moreover, there was no significant difference in the mechanical properties between the cortical bone trajectory revision group and the cortical bone trajectory initial group. It provides a reference for revision surgery of lumbar internal fixation with cortical bone trajectory technique in patients with failed traditional pedicle fixation.  

Key words: osteoporosis, lumbar spine, finite element analysis, cortical bone trajectory, revision surgery