Osteochondrosis of the disc usually begins with the pulpous nucleus. Ya. L. Tsivyan and V.E. Raikhinshtein (1973) established that the pulp nucleus has its own pressure (up to 3 kg / cm2). Such pressure, due to the hydrostatic properties of the nucleus, outside the load, the lower, the more pronounced the degenerative changes in the nucleus. Under the action of the load on the spine, the internal pressure increases, and between the intradiscal and external pressure per unit disk area there is a relationship: Pm = 1.5P.
As the load increases , the Pvp value approaches R. Such dynamics indicate that small and medium loads are perceived mainly by the pulpous nucleus, which converts them into tangential forces. As the compressive forces increase, vertical loads begin to act on the fibrous ring, to the perception of which the ring is not adapted.
When studying intradiscal pressure, collagen structures of the disc, and biochemical changes in the composition of the polysaccharides of the nucleus, Naylor (1962) found that depolymerization of polysaccharides of the collagen-polysaccharide complex of the nucleus of the intervertebral disc leads to an increase in fluid absorption and an increase in intradiscal pressure. Subsequently, the collagen structure of the pulp nucleus is replaced by fibrous tissue, which reduces its elasticity. Due to the loss of the depreciation function of the pulpous nucleus, hyaline plates and adjacent areas of the vertebral bodies are subject to permanent injuries.
This leads to degeneration of the hyaline plates and sclerosis of the end plates of the vertebral bodies. In some sections of the plates, the hyaline cartilage is replaced by fibrous, cracks and tears appear in them (N. S. Kosinskaya, 1961).
The pulpous core turns into a dry curd mass. In the fibrous ring, tears and crevices can be seen. The dead tissue of the disk is replaced by fibrous tissue, some parts of the necrotic disk are calcified.
Reducing the height of the intervertebral disc leads to disruption of normal anatomical relationships in the posterior spinal segment. The articular processes are displaced one relative to another, their congruence is violated, articular capsules are pulled.
The incongruity of the articular processes is the cause of the development of deforming arthrosis in the joints. The displacement of the articular processes along the axis of the spine leads to a decrease in the diameter of the intervertebral foramina, which negatively affects the spinal roots and vessels accompanying them (I.F. Purinsh, 1978).
If the fixative abilities of the discs are disturbed as a result of osteochondrosis, the possibility of some displacement of the vertebrae relative to each other appears, which is regarded as segmental instability. Yu. A. Tselishchev (1975) defines instability as a peculiar form of anatomical and radiological changes in the spine, as a result of which the relationship between adjacent vertebrae is disturbed. It should be noted that the instability of a certain segment of the spine is an early sign of intervertebral osteochondrosis.
Chronic pathology of the spine is often found in representatives of such sports as athletics, skiing, gymnastics, acrobatics, various types of wrestling, weightlifting. It is noted that 57.1% of athletes with osteochondrosis of the spine were under 25 years old, of which 11.4% were athletes under the age of 15 years.