Dynamic effects of eifferent nail placement strategies on LenkeC scoliosis.

Background: Although the internal fixation technique for scoliosis is effective, there is a great risk of nail placement in actual operation.

Objective: To compare the effects of three different nail placement strategies on LenkeC patients with scoliosis under cyclic loading.

Methods: Firstly, the finite element model was established by using CT scanning images and X-ray images of patients with LenkeC scoliosis. Secondly, the validity of the model was verified. Finally, the harmonic response analysis and transient dynamic analysis were carried out.

Results: The results showed that the maximum amplitude of each vertebral body appeared in the Z direction at the third natural frequency and the amplitudes of each corresponding vertebral body were very close under three kinds of nail placement. Under different nail placement methods, the uneven distribution of nails would make the model produce obvious stress concentration, but the principal stress of vertebral body and nail rod was far lower than its own yield strength. This showed that under the axial cyclic load, the vertebral bodies of scoliosis tended to have larger impact in Z direction. From the point of view of dynamics, it was feasible to reduce a certain number of nails in operation.

Conclusion: This paper revealed that it was feasible to reduce a certain number of nails during surgery.