Introduction
Evidence & Methods
The authors aimed to assess whether some Type II odontoid fractures seen acutely are actually acute-on-chronic injuries representing old nonunions.
Using their defined CT and MRI criteria, the authors found that 30% of acutely diagnosed fractures might actually be acute-on-chronic injuries.
Assuming the radiographic criteria are accurate, the findings are quite interesting. It is unclear, however, whether the conclusion can be drawn that surgery should be recommended for all presenting Type II fractures in order to avoid the risk of neurological injury due to secondary trauma. There may be a very high prevalence of individuals with nonunions who may never have a problem after subsequent falls. The study design does not lend itself to answering this question. That said, the findings might be useful during shared decision-making in acute presentations.
—The Editors
Odontoid fractures have been reported to represent between 9% and 19% of cervical spine fractures [1], [2], [3] and are most common in the elderly. According to the classification developed by Anderson and D'Alonzo [4] and modified by Grauer et al. [5], Type II fractures are the most common type, representing between 56% and 85% of odontoid fractures [1], [4], [6], [7], [8], [9]. Despite the location of the fracture in the proximal cervical spine, where a spinal cord injury can be devastating, neurologic deficit after odontoid fracture is uncommon, although the overall complication rate remains high [10]. The incidence of neurologic deficit after odontoid fracture has been reported to range from 13% to 25% [1], [2], [8], [9], [11], [12], with tetraparesis seen in only 2% to 8.5% [1], [2], [8], [9], [11], likely because of the relatively capacious spinal canal in the upper cervical region adjacent to the odontoid process.
Management of Type II odontoid fractures is controversial, and high rates of fracture nonunion after conservative treatment using an orthosis are well documented, exceeding 75% in some hard collar series [7], [11], [13]. Similarly, treatment with halo-vest immobilization results in nonunion rates reported as high as 54% [14]. Although high rates of nonunion occur after conservative treatment and immobilization, the long-term clinical significance of odontoid nonunion is not well characterized and has rarely been investigated in a systematic manner.
In this study, we sought to identify previously unrecognized odontoid fracture nonunions to document the rate of nonacute injuries in patients presenting with Type II odontoid fractures and report the incidence of new neurologic injury after secondary trauma in patients with odontoid nonunions. We hypothesize that a substantial proportion of odontoid fractures assumed to be acute are actually chronic injuries and that these chronic injuries have a significant rate of later displacement resulting in neurologic injury.