Design and mechanical evaluation of a novel dynamic growth rod to improve the surgical treatment of early-onset scoliosis.

Aims: Growth rods are the gold standard for treating early-onset scoliosis (EOS), but current treatments often fail to optimally promote spinal growth and require frequent distraction surgeries, leading to complications and significant burdens on patients.

Methods: We designed a novel growth rod (NGR) with unidirectional sliding and external regulation capabilities. Using a 3D model, we simulated the implantation of traditional growth rod (TGR) and NGR, applying a 400 N compressive load and a 1 Nm moment to test stiffness. We assessed spinal joint range of motion and growth rod stress distribution, and calculated axial force, moment, and fatigue life.

Results: The axial compressive and torsional stiffness of the NGR were higher than those of the TGR and the intact group. The Von Mises stress values of the NGR under all conditions were higher than those of the TGR. Additionally, the fatigue life of the NGR met basic daily living requirements. Overall, the NGR demonstrated superior stiffness and stress distribution, with stress primarily concentrated near the screw fixation points and distributed along the titanium rods.

Conclusion: The NGR, based on a distraction implant, includes a unidirectional sliding component and a spring-driven component, providing dynamic correction functionality. Additionally, it features a novel non-invasive lengthening mechanism that reduces the risk of infection. Compared to the current market-leading EOS implants, it offers enhanced stability. The novel device can potentially improve clinical outcomes in the surgical treatment of EOS.