Like adults, the spinal column in children has 7 cervical, 12 thoracic and 5 lumbar vertebrae, followed by the sacral and coccygeal vertebrae, which are fused into the pelvis. Picture all the in-vitro images of fetuses you’ve seen. In each of these the fetus is curved, not flat. Beginning at development the spine takes on a curved form, as curves provide greater strength than straight lines. However, unlike with adults, the fetal spinal column is one smooth arch; with adults, the cervical and lumbar spine are concave in relation to the convex thoracic vertebrae. At birth the newborn’s spine is one smooth convex arch. The cervical spine’s concave formation develops in the first months after birth when children begin gaining the strength to pick their heads up. The concave c-spine becomes more defined as the child gains strength. Later in development, the lumbar spine slowly begins transitioning to its adult concave formation when an infant begins to walk. In the absence of spine malformations, the thoracic column remains convex for an individual’s entire life. This alternating concave/convex/concave spinal curving provides strength and stability for both the spine and the body. These curves also cause gaps between the patient and a longboard during the immobilization process. Padding along the cervical and lumbar spines improves patient comfort and helps maintain natural spine alignment.
Each vertebra has several structures. The anterior and largest region is the spinal body, which is also the weight-bearing structure. Extending posteriorly at an angle off the vertebral body are two pedicles. The pedicles connect to two laminae to form the vertebral canal for the spinal cord. The spinous process protrudes posteriorly from the junction of the laminae, while a transverse process extends from each pedicle-lamina junction (Figure 1). Between each vertebral body is a cartilage disk, and longitudinal ligaments on the anterior and posterior sides of the spinal column hold the vertebrae together.
The spinal cord originates at the medulla oblongata and exits the skull through the foramen magnum. Traversing through the vertebral foramen of the spinal column, the cord ends in the lumbar spine. By adulthood this terminal end occurs around the L1–L2 junction; however, in children the spinal cord extends lower to the L3 region.
The incomplete spinal column ossification in children 8 and younger results in a weak spinal column. This weakness is particularly pronounced in the cervical spine and contributes to the high potential for spinal cord injury. This incomplete growth also leads to an increased frequency of multisite injury, which in children is at a rate of 22%.2 Such a high frequency of multiple-site injury highlights the need for stabilization of the total spine, not just the cervical, when column and cord injury are suspected in pediatric patients.
Children have much larger heads than adults in comparison to the rest of their bodies. Increased head mass, particularly on a developing and weak cervical spine, puts children, particularly under age 8, at risk for craniocervical disruption.4 Fortunately, craniocervical disruption is not that common. Its other name is internal decapitation, and it occurs when the cervical spine is completely separated from the brain.
Additionally, a larger head increases the forces against the neck when the child is exposed to sudden acceleration and deceleration. Until at least age 8 or 9, the child’s cranium sticks out posteriorly past the back. When these children are placed on a spine board, the head’s posterior extension will cause the neck to be flexed forward unless proper padding is placed under the patient’s shoulders and back.
Mechanisms of Injury
Injuring the pediatric patient’s spine takes significantly less force than injuring an adult spine. Recall that the child’s large head puts the neck at risk for whipping-force injuries, particularly when speeds change suddenly. Maintain a higher index of suspicion for column injury with children. A fall that for an adult is unlikely to produce a column injury may cause one in a child.
Motor vehicle accidents are the leading cause of spinal cord injuries for children under 10, and cause as many injuries as sporting accidents for children 10–14.5 Overall mechanisms for pediatric spine injuries are summarized in Figure 2.
There are three primary forces that lead to spinal injury. Longitudinal compression forces, also known as axial loading, literally compress the vertebrae against one another. These are typically seen in falls from heights and often cause vertebral body fractures. When extreme bending occurs, the patient experiences hinging forces, and transverse fractures become common. Hinging forces are common in whiplash, from bending over seat belts and when the body is exposed to sudden direction changes. Finally, shearing forces combine longitudinal and hinging forces, such as when a patient is twisted/thrown in a sporting accident or when a child is struck by a car.4
Completing an accurate spine assessment of pediatric patients with potential spine injury is important for many reasons. First, it may identify the presence of column or cord injury at the beginning of patient care. Second, a thorough exam allows for changes in the patient’s neurological condition to be monitored over time. Third, it may allow for the presence of spinal column and cord injury to be ruled out.