Kinetic characterization of adolescent scoliosis patients with Lenke 1B

Purpose: The purpose of this study was to investigate dynamic responses of Lenke1B+ spines of adolescent scoliosis patients to different frequencies. Methods: Modal analysis, harmonic response analysis and transient dynamics of a full spine model inverted by the finite element method using Abaqus. Results: The first-order axial resonance frequency of 4.51 Hz produced a maximum axial displacement of 30.15 mm. Comparison of the five frequencies indicated that the 10 Hz frequency response curve was smoothest, while the amplitude-frequency curve at 4 Hz showed the greatest fluctuations accompanied by resonance phenomena. At the resonance frequency, the maximum axial displacement of the thoracic spine was at T1, being 31.17 mm, while that of the lumbar spine was at L1, with 0.56 mm. The maximum stress of the intervertebral discs was located between T4 and T5, representing 3.496 MPa, the maximum stress in the small joints was located in the concavity between T7 and T8, with 19.97 MPa and the maximum axial displacement was 54.31 mm, located in the convexity between T6 and T7. Conclusions: The first-order axial resonance frequency was the most harmful to the patient. The uneven stress distribution in the spine was closely related to the degree of spinal deformity, with the thoracic spine being more sensitive to low frequencies than the lumbar spine. The concave side of the spinal deformity was more prone to stress concentrations while the convex side was more prone to deformity, indicating that disc degeneration and small-joint disease are more likely to occur at the most deformed part of the spine.