Biomechanical Characteristics of First Coronal Reverse Vertebrae in Lenke Type V Adolescent Idiopathic Scoliosis: A Study Using Finite Element Analysis.

Objective: Whether first coronal reverse vertebrae (FCRV) can directly cause biomechanical changes in adjacent segments remains unclear. The objective of this study was to explore the biomechanical changes in adjacent discs of the FCRV to better understand the stress distribution of adolescent idiopathic scoliosis (AIS).

Methods: According to the plain CT scan data of T8-T10 segment of an AIS patient, T9 was the FCRV, and a three-dimensional FE model was established accurately. The T8-T9 segment disc was defined as the adjacent upper disc (UD), axial section as half of the upper disc (HUD). Similarly, T9-T10 segment disc was the adjacent lower disc (LD), axial section as half of the lower disc (HLD). The biomechanical changes in adjacent discs of the FCRV under different loads were assessed.

Results: The maximum Von-Mises stress values of the LD were greater under various loads than those of the HLD, UD, and HUD. The average stress on the LD was greater than that of the other discs under the left lateral bending (LLB) or right lateral bending (RLB) load. It was noted that the concave side of the LD was subjected to greater stress under the neutral standing or LLB load compared with convex side. Additionally, the concave side of the LD was subjected to greater stress under the LLB or RLB load compared with that of other discs. Interestingly, the same trends were observed for the convex side of the LD.

Conclusions: FCRV caused LD to take on greater stress magnitudes. The stress showed a trend of local concentration, which was in the concave side of the scoliosis. These findings could contribute to further treatment planning for the patient and aid physicians' management decision-making.