Anderson and D’Alonzo recognized three types of odontoid fractures. ![]() C2 fractures can be categorized using either the Anderson and D’Alonzo classification or the Roy-Camille classification. This type of fracture is not usually associated with neurological deficits due to the tendency of the fragments to spread out away from the spinal canal.Ītlas fractures may often involve trauma to the axis as well. The Jefferson burst fracture, named after British neurosurgeon Sir Geoffrey Jefferson, was first reported in 1920 and typically presents as four bony fractures of the anterior and posterior arches of C1 following hyperextension or excessive axial loading of the atlas. Atlanto-occipital dislocations (AOD), commonly called internal decapitations, are another fracture pattern with C1 involvement. Single fractures involving the ring are highly unlikely, and a ring disruption typically accompanies any fracture. Burst, lateral mass, and laminar fractures are all recognized injuries. No monitoring is required unless indicated based on the injury pattern and comorbidities.Ītlas fractures can involve various and multiple structures and follow a number of patterns. Therefore, aspirin is preferred at our institution. While these therapies appear to be effective, many trauma patients have multiple organ system injuries and anticoagulation would increase the risk of hemorrhagic complications. Heparin and antiplatelet agents have been used for patients with asymptomatic BVAI as well. Typically, these cases are managed with 3 months of acetylsalicylic acid. If there is concern for vertebral artery injury, it is the authors’ practice to obtain CT angiogram and treatment is based on patient comorbidities with neurosurgery follow-up. The traditional diagnostic tool for vertebral injury is digital subtraction angiography however, CT angiography has also been demonstrated as a viable means of identifying symptomatic BVAI in the upper cervical spine. Nevertheless, occlusion of bilateral or dominant vertebral arteries can be devastating and the mortality rate in patients with BVAI without a neurological event is around 7 %. Most cases of BVAI remain asymptomatic and are often overlooked. They are subject to blunt vertebral arterial injury (BVAI) in cases of traumatic subluxation or fractures of the C1/C2 foramina. The vertebral arteries pass through the transverse foramina of the atlas. The dens articulates with the atlas via a facet on the posterior aspect of the anterior ring of the atlas, retained by the transverse ligament, providing the head with approximately 50 % of its lateral rotation. Posteriorly, the ring of the atlas is connected to the C2 by the posterior atlantoaxial ligament. At the anterior aspect of the ring, the joint is secured by the anterior atlantoaxial ligament. The C1-2 joint is highly mobile, with the dens of the axis secured to the anterior arch of the atlas by the transverse odontoid ligament. The atlas has two lateral masses with concavities that match the condyles of the occiput, forming the occipito-cervical articulations and allowing for movement of the skull. ![]() C1 lacks a vertebral body, consisting instead of a posterior and anterior arch that encircles the spinal cord, mostly posterior to the dens. This allows for lateral and vertical mobility of the head and upper spine. The atlas, or C1 vertebra, sits just inferior to the occiput and through its articulations with C2 and the occipital condyles joins the skull to the spine. Overall, a bimodal distribution is seen, with individuals aged in their mid-twenties and between 80–84 most at-risk for C1 fractures however, the mean age of diagnosis is 64 years and nearly three-quarters of cases occur in patients over 50 years of age. Pediatric patients with C1 fractures are rare, although the mortality rate among infants with this injury is approximately 16 %. This imbalance is reversed in the elderly where 52 % of patients are female, while in younger patients males account for upwards of 70 % of cases. There appears to be a male preponderance, with men accounting for 57–69 % of all cases. Classically, patients presenting with fractures of the atlas have sustained an injury due to diving into shallow water, falling, or a motor vehicle accident. In addition, violent rotational forces on the head and neck may infrequently cause atlas fractures. ![]() Atlas injuries occur due to a traumatic axial load and are typically associated with other damage to the upper cervical spine. Atlas fractures account for 2–13 % of acute injuries of the cervical spine and 1–2 % of all spinal injuries.
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