A 28-year-old male presents to the emergency department following a diving accident with axial loading injury to the cervical spine. An open-mouth odontoid radiograph is obtained. The structure marked **A** in the diagram appears centered and symmetric beneath the C1 atlas, with no lateral mass offset noted. Which of the following fracture patterns would be MOST LIKELY to show bilateral lateral mass overhang of C1 on this same view, representing the pathognomonic sign of instability?