Normal Radiographic Variants Simulating Injury

There are several common variations in the pediatric Cervical spine radiograph that may simulate injury. This section will describe the pattern of variation and describe how to distinguish it from pathology.

Pseudosubluxation. Anterior displacement of [C.sub.2] on [C.sub.3] of up to 4 mm is common in children younger than 7 years, but frequently can be noted in children up to 16 years of age. A line drawn from the anterior cortex of the spinous process of [C.sub.1], to [C.sub.3] should come within 1.5 mm of the anterior spinous process of [C.sub.2]. This misalignment may improve with FE views, but certainly isn't exaggerated by FE study. Pseudosubluxation also can occur at the level of [C.sub.3]-[C.sub.4].

Apparent Anterior Vertebral Wedging. Anterior wedging of the vertebral body may be seen on pediatric radiographs. This wedging represents non-uniform calcification of the vertebral body, not an asymmetric shape. Wedging is most common at C3 and may account for up to 3 mm difference between the anterior and Posterior height of the vertebral body. The vertebral bodies should assume an adult shape by age 8. This variant can be noted in Figure 8 at [C.sub.3] and [C.sub.4].

[FIGURE 8 OMITTED]

Overriding Anterior Arch of [C.sub.1]. Up to two-thirds of the anterior arch of [C.sub.1] may override the tip of the dens. This occurs in up to 20% of children younger than 7 years. (75)

Increased Predental Space. The predental space in children can be up to 5 mm. Ligamentous laxity (of the transverse and anterior atlanto-axial ligaments) may allow for an increased gap compared to the adult measurement of 3 mm.

Apical Odontoid Epiphysis. The odontoid tip has an epiphysis that usually is present at age 7, but may persist through age 16. (75,76)

Persistent Synchondrosis of the Dens. The growth plate at the base of the dens persists beyond age 7. This linear scarring may be confused with a fracture. This line is typically linear, occurs in a predictable location, and may have associated sclerosis. A fracture more commonly presents in an unpredictable location without sclerosis and with irregular edges.

Non-uniform Angulation During Flexion. There may be angulation between adjacent vertebral bodies during flexion. This may appear as marked flexion at a single joint. Although this can be a normal variant, it is difficult to distinguish from acute trauma in the correct clinical setting. (75)

Asymmetric Odontoid. The odontoid may be centered asymmetrically between the lateral masses of [C.sub.1]. Ligamentous laxity may cause this variant. While this can be a normal variant, it may be difficult to distinguish from an acute fracture in the correct clinical setting. (77)

Delayed Calcification of Anterior Arch of Axis. The anterior arch of [C.sub.1] frequently is not visible on plain film radiographs until 6 months of age. Before this, the axis is calcified insufficiently to be visible radiographically.

Treatment and Disposition