Movement of the spine

Due to the peculiar arrangement of the two joints - behind the articulationes inter-vertebrales and the main joint articulatio intersomatica in front between the vertebral bodies, movements are possible in all directions, although they are unevenly distributed in various parts of it.

The volume of movement of the spine depends on:

• the spatial arrangement of the planes of the joints formed by the processes of the spines of the vertebrae;
• height and elasticity of intervertebral discs.

The magnitude of the slope of vertebral bodies is directly proportional to the square of the height of the intervertebral disc and inversely proportional to the square of the cross-sectional area of the vertebral body.

The height of intervertebral discs is variable and depends on various factors.

ATTENTION! The decisive influence on the height of the intervertebral disc is the state of the gelatinous (pulpous) nucleus, which in turn depends on the level of the liquid content in the nucleus.

The cross-sectional area of vertebral bodies in numerical terms (in mm ² ) in the cervical, thoracic and lumbar spine is 225: 640: 784, respectively.

In the cervical spine:

• intervertebral discs have a large height;
• the cross-sectional area of vertebral bodies is insignificant;
• Individual vertebrae have a significant angle of inclination relative to each other;
• profitable configuration of intervertebral joints;
• large diameter of the spinal canal and intervertebral foramen.

All these circumstances provide greater mobility of the cervical spine as in:

• sagittal (flexion and extension);
• Frontal (slopes in the sides), and in
• horizontal (rotational motion) plane.

In the thoracic spine:

• the ratio of the height of the intervertebral discs to the cross-sectional area of vertebral bodies is less favorable than in the cervical region;
• the surfaces of the vertebral bodies are flat, and not convex, which greatly limits the mobility of the vertebral bodies relative to each other;
• the location of articular surfaces of the shoots of the arches in the frontal plane complicates, in addition, rotational movements.

In the thoracic spine, only small movements in the sagittal plane (flexion and extension) are possible.

ATTENTION! At the site of the transition of the thoracic region into the lumbar articular processes change their location: the articular surfaces of them pass from the frontal plane to the sagittal one.

In the lumbar spine:

• the ratio of the height of the intervertebral discs to the diameter of vertebral bodies in this department is less favorable than in the thoracic region, which provides a relatively larger volume of movements;
• The joints formed by the outgrowths of the arches are located in the sagittal plane; therefore the greatest volume of movements is observed at bending and extension;
• the amplitude of rotational movements and slopes to the sides is not so great.

In the sagittal plane, the volume of flexion and extension of the spine depends on the ratio of the height of the intervertebral disc to the diameter of the vertebral body.

In the frontal plane, the amplitude of the slopes to the sides depends both on the above factors and on the direction of the plane in which the surfaces of the joints formed by the processes of the arches of the vertebrae are located.

On the vertical axis, the volume of rotational movements depends on the location of articular surfaces of the outgrowths of the arch.

ATTENTION! Joints, whose surfaces are located in a plane representing a segment of the circle, provide a large volume of rotational movements.

The direction of movement is limited by the shape of articular surfaces, and their volume is limited by joint capsules and ligamentous apparatus.

Bending is limited:

• yellow;
• inter-active;
• bothersome;
• intertransverse ligaments;
• posterior longitudinal ligament;
• posterior semicircle of the fibrous ring.

Extension is limited:

• anterior longitudinal ligament;
• anterior semicircle of the fibrous ring;
• convergence of articular, spinous processes and arches.

Slopes aside are limited:

• longitudinal ligaments (anterior and posterior);
• lateral sections of the fibrous ring;
• yellow bunch (on the convex side);
• intertransverse ligaments;
• articular capsules.

ATTENTION! Tilts to the side are limited in the thoracic region, in addition, and the ribs.

Rotational movements are limited:

• fibrous ring;
•   capsules of the intervertebral joints.

Intervertebral disc:

• when ventral flexion, the disc undergoes the greatest deformations in its posterior part, which extends considerably into the lumen of the spinal canal;
• with the opposite movement, the disk deforms in the anterior part, protruding below the anterior longitudinal ligament;
• Ventral flexion is accompanied by an increase in the diameter of the intervertebral openings;
• dorsal flexion reduces the diameter of the intervertebral openings, increasing pressure on the spinal roots. Therefore, with discoid deposition, ventral flexion increases pains, and dorsal flexion reduces them (with radicular syndromes, these movements have the opposite effect).

[1], [2], [3], [4]