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The gross anatomical features of the thoracolumbar spine are shown in Figures 30-1, 30-2, 30-3, 30-4, 30-5, and 30-6.
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Developmental Anatomy
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The three ossification centers of each vertebra (one for the centrum and two for each neural arch) typically fuse between the age 2 and 6 years. Each vertebra assumes adult characteristics by approximately age 8 years and oblique pattern is achieved by age 15 years. The vertebral body physes can be seen on x-ray by 8 years of age when they begin to ossify peripherally and are relatively thicker at the periphery (ring apophysis). Ossification is completed by 12 years of age. The physis begins to fuse with the vertebral body at approximately 14 years of age and the fusion is complete between the age 21 and 25 years. The physis contributes to the growth in height of the vertebral body whereas the ring apophysis contributes to the growth in breadth of the vertebral body.
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The basic structure of the immature vertebral body and associated disk is depicted in Figure 30-7. The intervertebral disk is composed of a centrally located nucleus pulposus and peripheral annulus fibrosus, and the adjacent vertebral endplate. The nucleus pulposus in the immature spine is more resilient and elastic because of relatively higher water content compared to the mature spine.
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