Type III odontoid fracture
Type III fractures account for 39% of all odontoid fractures 1).
Type III odontoid fractures occur secondary to hyperextension or hyperflexion of the cervical spine in a similar manner to type II odontoid fractures. The difference is where the fracture line occurs.
In clinical practice, the Type III fracture encompasses a heterogeneous collection of morphologically different fractures of varying etiologies and patient demographics. At trauma centers, a complex, high-energy subtype exists that radiographically fits the definition of Type III odontoid fracture but of unknown clinical context.
Fractures with >50% comminution of the lateral mass or secondary fracture lines extending into the vertebral body or pars interarticularis were classified as complex by Niemeier et al. Biomechanically, complex fractures exhibit the same deforming forces as all odontoid fractures with additional instability in the rotatory or coronal plane 2).
In general, the Type III fracture is believed to have high healing potential due to the large fracture surface area through cancellous bone 3).
Imaging pearl. A type III odontoid fracture may be misinterpreted as odontoid fracture type II on sagittal CT because the fracture may appear to lie above the vertebral body (VB). Always check the coronal view, which more readily demonstrates the relationship of the fracture to the VB.
Acute Type III odontoid fractures were identified at a single institution from 2008 to 2015. Fractures were categorized as high- or low-energy fracture with high-energy fractures defined as those with lateral mass comminution (>50%) or secondary fracture lines into the pars interarticularis or vertebral body. Patients were treated in either a hard collar orthosis or halo vest and were followed for fracture union and stability.
One hundred and twenty-five Type III odontoid fractures were identified with 51% classified as complex fractures. Thirty-three patients met the inclusion and exclusion criteria including 15 patients treated in a halo vest and 18 in a hard collar orthosis. Mean follow-up was 32 (±44) weeks. Seven patients demonstrated progressive displacement of either 2 mm of translation or 5° of angulation and underwent delayed surgical stabilization. Two additional patients required delayed surgery for nonunion and myelopathy. Initial fracture displacement and angulation were not correlative with final outcome. No statistical advantage of halo vest versus hard collar orthosis was observed.
Complex Type III odontoid fractures are distinctly different from low-energy injuries. In the current study, 21% of patients were unsuccessfully treated nonoperatively with external immobilization and required surgery. For complex Type III fractures, they recommended initial conservative treatment, while maintaining close monitoring throughout patient recovery and fracture union 4).
A young woman who suffered a severe polytrauma secondary to a motor vehicle collision was diagnosed with a sagittal plane atlantoaxial joint dislocation associated with a type III odontoid fracture, despite adequate initial polytrauma management, the neurological damage was too critical, ultimately the decease of the patient.
The atlantoaxial joint dislocation is a rare condition of the upper cervical spine and is usually secondary to a high-energy traumatism. The disruption of the atlantoaxial ligaments originates the considered most unstable cervical spine lesion and with the highest mortality. Attributable to the kinetic the bone fracture of the Atlas and Axis are commonly related, especially the odontoid process. Early immobilization followed by surgical decompression and stabilization is primordial. Typically, these injuries have an ominous prognosis, that is aggravated if added a polytrauma affecting adjacent neurological structures and other vital organs 5).