Paradis et al( 2) reviewed 29 patients who had odontoid nonunion plus Atlanto-Axial Instability( AAI). Subluxation can cause spinal cord compression( 2, 6, 7).
Nonunion of the odontoid can lead to subluxation of the Atlanto-Axial joints. Odontoid nonunion, whether stable or not, is a potential threat to the spinal cord and the life of the patient. Stable (fibrous) nonunion needs minimal force to cause instability and neurological damage. The natural history of untreated injury is not known( 5). Nonunion of the odontoid is a hazardous situation( 4). The purpose of this article is to review the approach to the management of odontoid nonunion. Essentially, almost half of conservatively treated odontoid fractures ( especially type II) will develop nonunion. Other authors have identified the following risk factors for nonunion fracture gap of more than 1mm, posterior displacement of more than 5mm, and delayed treatment of more than four days. He considered these two factors as the most important. There must be alternative explanations for the high nonunion rate in Type II odontoid fractures.Ĭholavech Chavasiri ( 3) identified risk factors associated with nonunion in conservatively treated odontoid fractures (those treated with Halo vest) : initial displacement and distraction. Additionally, histological examinations of odontoids removed during surgery failed to demonstrate the presence of avascular necrosis as the cause of nonunion. The blood supply of the mongrels' odontoids is similar to that of humans'. Schatzker et al ( 2) showed in experiments using mongrels that interruption of blood supply to the odontoid is not the cause of nonunion. Many authors believe that the major cause of high nonunion rate in Type II is interruption of blood supply to the proximal part of the odontoid. Type II has a high rate of nonunion: 40%-75% in conservatively treated cases. Types II and III are therapeutically very important. Type 1 fracture is an avulsion type and is managed non-surgically. Odontoid fractures are classified according to Anderson and D'Alonso. The fracture can follow minimal force, especially in elderly patients. Odontoid fractures account for 10%-16% of all cervical spine fractures( 1).
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