Accessory atlantoaxial ligament avulsion fracture of the axis: Are there any clinical implications?

Injuries to the craniocervical support structures are frequently observed in neurotrauma cases. Stability of this region is of vital importance. Literature has mainly focused on three major ligaments of the craniocervical junction: The tectorial membrane, the transverse ligament, and the alar ligaments. However, the accessory atlantoaxial ligament (ALL) also seems to be involved in craniocervical stability as shown in cadaveric specimens. Still, the biomechanical importance of this structure needs to be determined, especially in trauma settings. Here, we describe a case of isolated traumatic injury to this structure and discuss the clinical outcome. A 64-year-old polytrauma patient with a remarkable avulsion fracture at the site of the insertion of the ALL was admitted to our center. We evaluated the patient both clinical and radiological at admission, after 3 months and after 1 year. We clinically assessed the upper cervical rotational stability using the cervical flexion-rotation test. We observed no rotational instability or any other clinical repercussions at the long-term after an isolated ALL injury. This case shows that isolated traumatic damage to the ALL is possible. Unilateral damage to the ALL probably does not cause rotational instability of the craniocervical junction. In case a similar avulsion fracture is observed, we recommend performing a magnetic resonance imaging of the craniovertebral region to assess for any ligamentous lesions.