![]() ![]() 6 suggested modifying the Anderson classification to consider fracture displacement, obliquity, and comminution. It has been noted that there is relatively poor inter-observer agreement in differentiating Type II and Type III fractures. ![]() Type II fractures denote a fracture through the base of the dens but not involving the body of C2, while Type III fractures extend into the body of C2. Type I fractures represent a fracture of the tip of the odontoid, cephalad to the transverse ligament. 3Īnderson and D’Alonzo 4 described the most commonly used classification system for odontoid fractures ( Fig. However, in the setting of chronic instability due to an odontoid nonunion, late-onset myelopathy has been observed. Because of the capacious nature of the spinal canal in the upper cervical spine, odontoid fractures are rarely associated with an acute neurological deficit. Fractures of the odontoid may result in instability because the C1–odontoid complex can translate relative to the body of C2. Posterior translation is prevented by the odontoid articulation against the anterior arch of C1. 2 Anterior translation of C1 relative to C2 is prevented primarily by the transverse ligament and secondarily by the alar and apical ligaments. 1 The odontoid process of C2 serves as a peg on which the C1 ring rotates: sixty degrees of axial rotation occurs at the C1–C2 articulation. Odontoid fractures are the most common cervical spine fracture in the elderly, and their incidence is increasing. ![]()
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