Radiography

This article illustrates the typical clinical and radiographic findings of patients with injuries to the cervical spine and discusses basic treatment guidelines. Cervical spine injuries are frequently seen in multitrauma patients and can be devastating injuries, particularly if not identified in a timely manner. The initial evaluation is both clinical (questioning about neck pain, palpating the neck, and neurologic examination) and radiographic, if indicated. All trauma patients should be effectively immobilized until a cervical spine injury is ruled out.
The initial radiographic work-up consists of anteroposterior, lateral, and open-mouth odontoid views. If the C7-T1 junction is not seen on plain radiographs, a swimmer’s view of the cervical spine should be obtained. If this view remains inadequate, a computed tomography (CT) scan through the nonvisualized vertebral bodies should be obtained. Depending on the type of injury, additional radiographic studies may be indicated. Early recognition of cervical spine injury and consultation of a spine specialist is imperative for a good neurologic outcome.
Atlanto-occipital dislocation
Frequency/incidence
Atlanto-occipital dislocation (AOD) is present in up to 1% of patients with cervical spine injuries. AOD has been found in 19% to 35% of autopsies of fatal cervical spine injuries. There is a higher incidence of AOD among children [1].
Signs and symptoms
AOD is typically fatal [1,2]. Mortality is most frequently from anoxia caused by respiratory arrest. Among survivors, more than 70% have an associated head injury [3]. Cranial nerve palsies (especially types VI, IX and XII) are seen in 50% of cases. Complete quadriplegia or brain-stem injury typically results in death. Brown-Sequard or central cord syndrome may also be observed. Patients will frequently deteriorate when placed in cervical traction. The patient may be completely neurologically intact and have a good outcome [1].
Etiology/pathophysiology
AOD is caused by violent trauma (typically, motor vehicle collision or pedestrian struck by car) and may be related to hyperextension with distraction [1,3]. In fatal cases, there is transection of the spinal cord; however, in cases in which the patient survived, there was angio-graphic evidence of vertebral artery injury at the C1 level where the artery penetrates the dura to become intracranial. From a mechanical view, the distal vertebral artery as well as the head is
freely moveable in AOD, causing the artery to be injured at the C1 level as the vertebral artery then becomes anchored to the spine within the transverse foramen. At autopsy, none of these patients had evidence for mechanical injury or transection of the cord [4].
Image of choice for diagnosis
Radiographic diagnosis is difficult, which frequently delays diagnosis. Plain lateral radiographs are typically the first test ordered. Plain radiographic techniques for diagnosing this entity include the Power’s ratio, and the X-line method [5]. The opisthion and basion are often difficult to identify on plain films, making thin-slice CT (3-mm cuts) with sagittal reconstruction a more accurate way of identifying AOD (see Power’s ratio in the Image hallmarks section). If suspicion is high, reformatted CT is the test of choice.
Image hallmarks
There is typically massive retropharyngeal soft tissue swelling (Fig. 1). On plain lateral radiographs, the Power’s ratio is frequently employed. The distance from the basion to the posterior arch of the atlas divided by the distance from the opisthion to anterior arch of atlas is greater than 1.0 in all cases of AOD. A Power’s ratio of less than 0.9 is normal, whereas ratios of 0.9 to 1.0 are borderline, representing 7% of the normal population and no cases of AOD [2].
Management
Initial treatment involves strict immobilization of the cervical spine. Patients are typically reduced and placed in a halo vest. It is typically recommended that the patient subsequently undergo posterior occipital to cervical fusion [1,3].


















Atlantoaxial rotatory subluxation/dislocation
Frequency/incidence
Rotatory subluxation at the C1-2 joint is relatively uncommon. Signs and symptoms
Patients will frequently have torticollis, inability to rotate their head, facial flattening (if chronic), and upper cervical pain. The head position is sometimes described as ‘‘cock robin’’ (20° lateral tilt to one side, 20° rotation to the other side, and a slight flexion) [6].
Etiology/pathophysiology
Rotatory subluxation typically occurs in children because the facet joints are smaller and more steeply inclined, and children have a larger head-to-body ratio, making the joint prone to rotational damage [7]. It can be seen spontaneously, with minor or major trauma, and can occur in association with upper respiratory infections [6].