![]() ![]() The blood supply of C2 is sparse at the base of the dens because of the presence of a true synovial joint. Type II odontoid fractures present a management challenge because of the confluence of several factors. In the setting of anterior displacement, management with internal fixation should be considered. However, Type III fractures with anterior displacement may be biomechanically unstable and are at risk for repeat displacement with closed management. Type III fractures occur through the C2 body, which has a relatively robust blood supply and healing potential following closed reduction, these injuries will usually heal with immobilization in a hard cervical orthosis or halo vest. In the absence of dislocation or instability, these injuries can be managed with a collar until symptoms subside. In the setting of a Type I fracture, upper cervical instability and occipitocervical (OC) dislocation must be excluded. The management of Type I and Type III odontoid fractures has little controversy. An MRI should also be considered if a ligamentous injury is suspected. The presence of a neurological deficit is an absolute indication to obtain MR imaging (MRI). If the fracture involves the foramen transversarium, magnetic resonance (MR) angiography should be considered to assess the vertebral artery. Odontoid fractures are associated with other cervical fractures, such as C1 arch fractures, and the clinician must carefully evaluate the entire cervical spine on CT scan. If a fracture is identified or cannot be excluded, a computed tomography (CT) scan with sagittal and coronal reconstructions should be obtained to aid with fracture classification and treatment planning. When evaluating an elderly patient with a history of repeated falls, one must consider the possibility of a chronic fracture.Īnteroposterior (AP), lateral, and open-mouth odontoid views should be routinely obtained in the setting of a suspected fracture. The incidence of odontoid fractures has a bimodal age distribution: younger patients have predominantly high-energy mechanisms, whereas older patients generally present with low-energy mechanisms, such as falls from standing. (From Stannard et al., Surgical Treatment of Orthopaedic Trauma. Note the subset (D) IIA added by Haley, which denotes comminution. 4.1 Anderson and D’Alonzo classification system illustrating (A) Type I, (B) Type II, and (C) Type III odontoid fractures. ![]() This modification also further distinguishes between Type II and III fractures, with Type III fractures defined as those involving the C2 superior articular facet.įig. 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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