CHAPTER 13 Unique Anatomic Features of the Pediatric Spine
IMPORTANCE OF THE PEDIATRIC SPINE
Understanding the spines of children is important for a number of reasons. Contrary to common belief, a fairly high number of children, particularly adolescents, suffer from back pain, and the pain is recurrent in many (Burton et al., 1996). A study of children in Finland, conducted by Taimela et al. (1997), showed the following prevalence of back pain among children:
No difference was found in the incidence of low back pain between males and females in the study. However, pain was identified as being chronic or recurrent in 26% of boys with low back pain and in 33% of girls with low back pain (Taimela et al., 1997). Perhaps surprisingly, intervertebral disc (IVD) degeneration has been identified in with magnetic resonance imaging (MRI) in 15-year-old children, and an unexpectedly high number of young people in their twenties have bulging IVDs that are thought to be the cause of their back pain (Kraemer, 1995; Salminen et al., 1995). IVD protrusion is more prevalent in taller adolescents who have less ability to forward flex than in those of average height with better mobility in forward flexion (Salminen, Erkintalo-Tertti, and Paajanen, 1993). As might be expected, the incidence of low back pain among children who are less physically active is higher than in children who engage in the average level of physical activity (Salminen et al., 1995). Fortunately low back pain in childhood and adolescence does not seem to be related to disabling back pain in adulthood (Burton et al., 1996).
The purpose of this chapter is to identify unique anatomic features related to the pediatric spine. A separate chapter on this topic is important because the spines of children are not just miniature versions of the spines of adults. For example, many of the differences related to the pediatric spine can be mistaken for fractures on the x-rays of children (Fesmire and Luten, 1989). Because normally children are not x-rayed unless the chief complaint is related to trauma, or suspected trauma or other serious pathology, the identification of fractures is a primary focus when viewing these x-ray films. Knowing the precise locations of the ossification centers and the locations of closure, or final union, of the primary and secondary centers of ossification is important because these sites are the regions that can be mistaken for fractures most easily.
AGE-RELATED ANATOMIC CHANGES OF THE PEDIATRIC SPINE
The age-related changes to key anatomic structures of the spine are covered in several ways in this chapter. First, Table 13-1 describes the changes of key anatomic structures for several pediatric age groups. Notice that the key anatomic structures included in Table 13-1 are the curves of the spine, vertebral bodies, IVDs, intervertebral foramina (IVFs), Z joints, and neurologic elements in the vertebral canal. The age groups of Table 13-1 are newborn, 3 months, 2 years, and 10 years. Next, the following sections briefly summarize the most important anatomic changes for the age groups just listed. Finally, age-related changes of the Z joints and the IVFs are described. These two anatomic structures are featured because they undergo unique and clinically important changes with age.
The Newborn Spine
Newborn IVFs are relatively huge (Fig. 13-2). The term capacious is used sometimes to describe the size of the IVFs with respect to the relatively small foraminal contents of young children. Occasionally authors incorrectly apply the term capacious to the IVFs of adults (Crelin, 1973), whereas others have shown that this clearly is not the case (Hewitt, 1970; Giles, 1994). The main reason for the relatively large size of the IVFs in newborns is that the Z joints, which form the posterior border of the IVFs, are underdeveloped in young children (see Fig. 13-2). Both the superior and inferior articular processes are extremely small and the distal ends of both are primarily cartilaginous. The spines of newborns should be handled with extreme care for this reason.
The 3-Month-Old Spine
The IVFs of 3-month-old spines remain large, and the articular processes of the Z joints remain relatively underdeveloped (Fig. 13-4). The distal ends of the superior and inferior articular processes are still primarily composed of cartilage (see Fig. 13-4).
The 2-Year-Old Spine
The IVFs of the 2-year-old spine remain capacious; however, they begin to slightly narrow at their inferior aspect, particularly in the lumbar region (Fig. 13-6). The superior and inferior articular processes, which form the Z joints, begin to grow into the posterior and inferior aspect of the IVFs and then become more fully ossified during this stage of development. Even with this added growth and ossification, the Z joints are still relatively underdeveloped, leaving the IVFs comparatively large (see Fig. 13-6).
The 10-Year-Old Spine
The neurocentral synchondrosis persists as a plate of growth cartilage until it completes its fusion and is completely replaced with bone at 3 to 6 years of age. This cartilage plate, and later bony plate, which is located within the posterolateral aspect of the fully developed vertebral body, extends from the superior to inferior anular apophyses. This bony plate persists throughout life (Maat, Matricali, and van Persijn van Meerten, 1996). These plates are thought to be the reason that burst fractures of the vertebral body usually do not enter the posterolateral aspect of the anatomic vertebral body, and why during such fractures a central segment of the vertebral body frequently protrudes directly posteriorly, between the “wedge shape” formed by the left and right bony plates found at the neurocentral junction (Maat, Matricali, and van Persijn van Meerten, 1996).
Ligamentous laxity typically exists in the cervical spines of children, especially those less than 8 years of age. Such laxity can create a pseudosubluxation (i.e., the appearance of dislocation) during forward flexion (Kasai et al., 1996) as seen on lateral x-rays. This phenomenon is found in 46% of children 1 to 8 years old. The pseudosubluxation usually is most marked between the second and third cervical vertebrae (Fesmire and Luten, 1989).
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