Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Musculoskeletal System
Bones of the Trunk and Their Joints
Movements of the Spinal Column - Age-Related Features of the Spine

The newborn's spine appears as a gentle, anteriorly concave arch. Spinal curves begin to develop only from the 3rd to 4th month of life, when the infant starts holding up its HEAD. First, the cervical lordosis forms, convex anteriorly. As the baby begins to sit (at 4–6 months of age), the thoracic Kyphosis develops, convex posteriorly. Later, the lumbar lordosis appears, also convex anteriorly, which forms as the child begins to stand and walk (9–12 months after birth). At the same time, a compensatory posteriorly convex sacral kyphosis is formed. The curves of the spinal Column become clearly visible by the age of 5–6, and their final formation is completed by adolescence and early adulthood.

Pathological lateral curves of the spine—Scoliosis—can occur due to uneven Muscle Development on the right or left side of the body, incorrect posture of students at their desks, or in athletes as a consequence of asymmetric muscle exertion.

The length of a newborn's spinal column accounts for 40% of their body length. During the first two years, the length of the spine almost doubles. Different segments of the newborn's spinal column grow unevenly. In the first year of life, the lumbar region grows the fastest, while the cervical, thoracic, and sacral regions grow somewhat slower. The coccygeal region grows the slowest. By the onset of Puberty, the growth of the spinal column slows down. A new acceleration in its growth is observed in girls around 12–13 years of age, and in boys around 13–14 years of age.

Intervertebral discs in children are relatively thicker than in adults. With age, the thickness of the intervertebral discs gradually decreases, they become less elastic, and The Nucleus pulposus diminishes in size. In elderly individuals, due to the reduced thickness of the intervertebral discs and the increased curvature of the thoracic kyphosis, the length of the spinal column decreases by 3–7 cm. There is a generalized loss of bone density in the vertebrae (Osteoporosis), along with calcification of the intervertebral discs and the anterior longitudinal ligament. All of this diminishes the Shock-absorbing Properties of the spinal column, as well as its mobility and strength.