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Physiological curvatures of the spine
Last reviewed: 04.07.2025
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Normal (or anatomical) posture is the ability of the body to maintain a vertical position in the sagittal and frontal planes with a uniform load on the legs, straightened at the knee joints. In a person standing upright with normal posture, the back of the head, the angles of the shoulder blades, the buttocks and heels should be located in one frontal plane, while the stomach should be pulled in. Normal human posture corresponds to the Forestier pose.
In the frontal plane, with normal posture, the line of the spinous processes of the vertebrae projectively coincides with the conditional plumb line coming from the occipital protuberance. In this case, the levels of the shoulders, the angles of the scapulae, the bispinal and bitrochanteric lines are parallel, and the waist triangles are symmetrical. With normal anatomical posture, there are no curvatures of the spine in the frontal plane.
In the sagittal plane, with normal posture, the conditional plumb line, coinciding with the center of gravity, passes through the middle of the parietal region, the anterior edge of the external auditory canal, the bodies of the C7 and T12 vertebrae, the anterior part of the body of L5 and the middle of the foot. In the sagittal plane, physiological deviations of the spine from the plumb line are in the thoracic and sacral regions to the rear (kyphosis), in the cervical and lumbar regions - to the front (lordosis).
The opinions of different authors regarding physiological curvatures in the sagittal plane coincide in that the apex of physiological kyphosis is at the level of T7-T8 segments, while the kyphosis has a gentle arc formed by 8-10 vertebral segments (from T2-T3, T11-T12). There is no unity in determining the absolute value of physiological kyphosis, while the indicated values of its angle fluctuate in a fairly wide range - from 15° to 50°.
The value of physiological lumbar lordosis in adults is, according to W. P. Bunnell, from 40° to 60°, and its apex is located at the level of L3-L4 vertebrae. We were unable to find data on the absolute values of physiological lordosis in children and adolescents.
Location of the spinal cord cone
The level of the apex of the spinal cord cone relative to the bodies of the lumbar vertebrae is an important anatomical indicator. As a result of different rates of physiological development of the bone structures of the spinal column and the spinal cord contained in the spinal canal, a gradual displacement of the spinal cord cone in the cranial direction occurs in the postnatal period. Thus, in a newborn, its apex is located at the level of the upper edge of the L4 - the lower edge of the L3 vertebra. At the age of one month, the cone "rises" to the middle of the body of L3, and by five years - to the lower edge of L2. By about 8-10 years, the spinal cord cone occupies a position characteristic of adults, which corresponds to the middle of the body of L1 in men and the middle of the body of L2 in women.
The use of magnetic resonance imaging has significantly improved the diagnosis of various pathological conditions of the spinal cord. The location of the spinal cord cone below the physiological level indicates its fixation, which, in the presence of clinical manifestations of tethered (fixed) cord syndrome, requires clarification of the cause of fixation (short terminal thread, tumor, spinal cord malformation, adhesions, etc.) and appropriate neurosurgical correction.
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