Novel artificial transverse atlantal ligament reconstruction for atlantoaxial instability: a finite element analysis

The transverse atlantal ligament (TAL) serves as a crucial anatomical structure in maintaining atlantoaxial stability. Currently, fusion surgery remains the primary therapeutic approach for atlantoaxial instability (AAI) resulting from TAL rupture. However, this surgical intervention inevitably leads to the loss of atlantoaxial mobility and may accelerate degeneration of adjacent segments. Reconstruction of the TAL may emerge as a potential solution to address these clinical challenges. The objective of this study is to evaluate the functionality and stability of an artificial transverse atlantal ligament (ATAL) .

A normal C0-C3 finite element analysis (FEA) model was developed and validated. Based on this model, additional models were constructed, including a TAL rupture model, a posterior C1-C2 screw and rod fixation model, and four ATAL reconstruction model with varying preload forces. Each model was subjected to anterior-posterior (AP) displacement and range of motion (ROM) tests under a 100 N AP load and a 1.5 Nm rotational moment. The functionality and stability of the C1-C2 segment were analyzed across the models based on the experimental results.

Under a 100 N AP load, the AP displacement of the TAL rupture group increased significantly compared with the intact group. In contrast, the AP displacement of the ATAL reconstruction group without preload slightly decreased compared with the intact group. Under a 1.5Nm rotational moment, in the ATAL reconstruction group without preload, compared to the intact group, the C1-C2 flexion, extension, and lateral bending increased by 2.43%, 5.32%, and 20.82%, respectively, while rotation decreased by 1.18%, and compared to the TAL rupture group, the C1-C2 flexion and rotation slightly decreased by 0.76% and 2.04%, respectively, with no significant changes in extension and lateral bending. Compared to the posterior C1-C2 screw and rod fixation group, the C1-C2 ROM in all directions significantly increased in the ATAL reconstruction group.

ATAL reconstruction enables the atlantoaxial joint to achieve sufficient stability while effectively preserving its ROM in all directions. This approach represents a paradigm shift from the current reliance on fusion techniques, which severely restrict atlantoaxial mobility, offering a novel therapeutic strategy for addressing AAI caused by TAL rupture.