Original article
Finite element analysis of posterior cervical fixation

https://doi.org/10.1016/j.otsr.2014.11.007Get rights and content
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Abstract

Background context

Despite largely, used in the past, biomechanical test, to investigate the fixation techniques of subaxial cervical spine, information is lacking about the internal structural response to external loading. It is not yet clear which technique represents the best choice and whether stabilization devices can be efficient and beneficial for three-column injuries (TCI).

Hypothesis

The different posterior cervical fixation techniques (pedicle screw PS, lateral mass screw LS, and transarticular screw TS) have respective indications.

Materials and methods

A detailed, geometrically accurate, nonlinear C3–C7 finite element model (FEM) had been successfully developed and validated. Then three FEMs were reconstructed from different fixation techniques after C4–C6 TCI. A compressive preload of 74 N combined with a pure moment of 1.8 Nm in flexion, extension, left–right lateral bending, and left–right axial rotation was applied to the FEMs.

Results

The ROM results showed that there were obvious significant differences when comparing the different fixation techniques. PS and TS techniques can provide better immediate stabilization, compared to LS technique. The stress results showed that the variability of von Mises stress in the TS fixation device was minimum and LS fixation device was maximum. Furthermore, the screws inserted by TS technique had high stress concentration at the middle part of the screws. Screw inserted by PS and LS techniques had higher stress concentration at the actual cap–rod–screw interface.

Conclusions

The research considers that spinal surgeon should first consider using the TS technique to treat cervical TCI. If PS technique is used, we should eventually prolong the need for external bracing in order to reduce the higher risk of fracture on fixation devices. If LS technique is used, we should add anterior cervical operation for acquire a better immediate stabilization.

Keywords

Three-column injuries
Finite element model
Posterior cervical fixation technique

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1

Yang Duan and Hehui Wang contributed equally to this work. Yang Duan and Hehui Wang are co-first authors.