Plough Fracture (Anterior Arch Fracture Type Traumatic Posterior Atlantoaxial Dislocation, TPAD-AOT Type III): A Retrospective Study of Nine Clinical Cases With Complete Imaging Data.

Fracture of the anterior arch of the atlas, accompanied by posterior atlantoaxial dislocation, typically presents on CT imaging as the odontoid process penetrating through and causing a high-energy shear fracture of the anterior arch. This injury may occur with or without retained fracture fragments. Its characteristic appearance resembles that of a plough traversing the earth, and it has historically been termed the plough fracture. Published case reports documenting this specific fracture pattern remain extremely rare in the literature. In our research group's earlier study on traumatic posterior atlantoaxial dislocation (TPAD), this fracture pattern was categorized as anterior arch fracture type TPAD (TPAD-AOT Type III). It was further subclassified based on transverse ligament integrity into: (1) Anterior arch fracture type TPAD with intact transverse ligament, and (2) Anterior arch fracture type TPAD with transverse ligament injury, reflecting a progressive increase in instability severity across these subtypes. Hyperflexion and hyperextension injury mechanisms play significant roles in the pathogenesis of this fracture pattern, with definitive diagnosis typically established via CT imaging. The integrity of the transverse ligament is critical for atlantoaxial stability. For patients with an intact transverse ligament, rigid external fixation or internal fixation may be indicated based on fracture displacement and reducibility. However, in cases with transverse ligament injury, posterior C1-C2 fusion typically achieves favourable functional outcomes.