Sagittal Plane – Definition and Quiz

Medical diagnoses often include a definition of the sagittal size of the spinal canal. Most patients do not understand this definition, which causes them natural concern. What is sagittal size, how does it affect human health, what are the physiological indicators, what causes the deviations and what are their consequences? These questions will be answered in this article.

Sagittal size of the spinal canal

What is a canal in the spine

You should know this in order to more easily understand further, more complex information. The spinal canal is a longitudinal cavity located along the vertebra. It is formed on one side by the posterior wall of the vertebrae, and on the other by flexible discs and vertebrae. Thus, it is limited on all sides by bone tissue, and the diameter of the spinal canal changes depending on the parameters of the vertebrae. The bases of the arches of each vertebra have special connecting slots, with the help of which they are connected into a single spinal column. When connected, these arches leave openings that house the spinal cord.

The spinal canal is a container for the spinal cord, its roots and vessels

Strong ligaments are placed in a circle, they ensure stability of the body position and are able to absorb loads on the spine. Flexibility is ensured by elastic, strong ligaments that line the canal along its overall length. Due to the structural features of the vertebrae, the canal in the vertebra has different sizes depending on its specific location. Normally, the canal has an average area of ​​2.5 cm2, the maximum value is 3.2 cm2.

The canal has different sizes depending on the structure of the vertebrae

To ensure normal functionality, the volume of the canal must be greater than the volume of the brain membrane. The space free from the brain is filled with plexuses of capillaries and fiber. This space is called the epidural, and it is where pain medications are injected during anesthesia. The canal contains the spinal cord with its specific membranes and branches. Physiologically normal blood supply to the bone bodies of the vertebrae and their other parts is provided by three arteries.

Layout of the epidural space

Content

• 1 Terms used 1.1 Position relative to the center of mass and the longitudinal axis of the body or body extension
• 1.2 Position relative to the main parts of the body
• 1.3 Basic planes and sections
• 1.4 Methods of drug administration

What is sagittal size

To characterize the state of the canal, the definition of sagittal size is used. The sagittal size characterizes the size of the spinal canal in the anteroposterior direction, from the uppermost section of the canal to the lowest. The dimensions on both sides of the conventional plane of the imaginary anatomical section are taken into account. Such definitions allow us to have a more complete understanding of the state of the spinal canal and enable physicians to specifically classify detected pathological changes in tissue alignment.

Sagittal plane

Literature[ | ]

• Ventral // Great Soviet Encyclopedia: in 66 volumes (65 volumes and 1 additional) / ch. ed. O. Yu. Schmidt. - M.: Soviet Encyclopedia, 1926-1947.
• Aboral // Great Soviet Encyclopedia: in 66 volumes (65 volumes and 1 additional) / ch. ed. O. Yu. Schmidt. - M.: Soviet Encyclopedia, 1926-1947.

Geometric shapes of sagittal size

The so-called sagittal section changes depending on age, up to 20 years it increases, up to 50 years the parameters are stable, and later due to degenerative and dystrophic processes they decrease. These are normally occurring physiological processes; medical science cannot currently influence them. The sagittal size in the lower lumbar region decreases most with age, hence the frequent back pain in older people.

Normal dimensions of the spinal canal

Normal cross-sectional values ​​in the area of ​​3–4 vertebrae are ≈ 17 mm and remain the same throughout life. If the size decreases to 13 mm or less, then this is a clear sign of pathological changes in the spinal canal. But for the normal functionality of the spinal cord, not only the area, but also the configuration of the canal is important.

X-ray – spinal canal stenosis

Anatomical characteristics of sagittal size

The canal begins at the point where the spinal nerve departs from the entrance (dual sac). In the area of ​​the vertebrae of the neck, it is directed forward and outward. The posterior wall is the plate of the arch, limited by the upper process. This arrangement affects the formation of shapes and sagittal dimensions. The absolute parameters of the channel and nerve indicate the capabilities of the body's protective reserves. Between both anatomical formations there is a free space that can, to a certain extent, compensate for degradation or physical damage to the vertebrae and adjacent tissues.

Sagittal and frontal diameters of the spinal canal

The difference in these sizes shows the protective function capabilities of the body, and their ratio, taking into account the contents, characterizes the reserve space of the spine. In normal condition, the central spinal canal has a space of no more than 5 mm. It is greatest in the upper spine, where the reserve reaches a maximum of 7 mm. The reserve is least in the latinal recess; in this place the free space does not exceed one millimeter, but in practice it is often completely absent. It is in this place that the risks of impaired nerve functionality as a result of degradation or damage to the vertebral discs are greatest.

If you want to learn in more detail the structure of the human spine, its sections and functions, and also consider the causes of diseases, you can read an article about this on our portal.

Terms used[ | ]

Position relative to the center of mass and the longitudinal axis of the body or body outgrowth[ | ]

Position relative to the main parts of the body[ | ]

• Aboral
  (lat. aboralis) (antonym:
  adoral
  ) - located on the pole of the body opposite the mouth.
• Adoral
  (lat. adoralis) (oral; antonym:
  aboral
  ) - located near the mouth.
• Abdominal
  (lat. abdominalis) - related to the stomach.
• Ventral
  (lat. ventralis) (antonym:
  dorsal
  ) - abdominal (anterior).
• Dorsal
  (lat. dorsalis) (antonym:
  ventral
  ) - dorsal (posterior).
• Caudal
  (lat. caudalis) (antonym:
  cranial
  ) - caudal, located closer to the tail or to the posterior end of the body.
• Cranial
  (lat. cranialis) (antonym:
  caudal
  ) - head, located closer to the head or to the anterior end of the body.
• Rostral
  - nasal, lit. “located closer to the beak”; located closer to the head or to the anterior end of the body.

Basic planes and sections[ | ]

Anatomical planes. Green indicates the axial plane, blue indicates the frontal plane, red indicates the sagittal plane, yellow indicates one of the parasagittal planes (parallel to the sagittal)

• Sagittal
  - a section running in the plane of bilateral symmetry of the body.
• Parasagittal
  - an incision running parallel to the plane of bilateral symmetry of the body.
• Frontal
  (lat. frontalis) - an incision running along the anterior-posterior axis of the body perpendicular to the sagittal.
• Axial
  - a cut running in the transverse plane of the body

Methods of drug administration[ | ]

Main article: Route of administration

• orally
  - through the mouth;
• intradermal
  ,
  intradermal
  (eng. intracutaneous or intradermal);
• subcutaneously
  (eng. subcutaneous);
• intramuscularly
  (eng. intramuscular);
• intravenously
  (eng. intravenous); intracubital (lat. intra-inside, lat. venae cubitalis - cubital veins) intravenous injection into the veins of the cubital fossa;

Causes of pathological changes in the sagittal size of the canal

The sagittal size in the vast majority of cases decreases; expansion is possible only as a result of very severe spinal injuries that cause a violation of the integrity of the vertebrae. Such situations arise after strong mechanical impacts and cause extremely negative consequences, including general paralysis or death.

Spinal stenosis

A decrease in sagittal size parameters is caused by structural disorders of the vertebrae, which have a different nature of appearance. Negative changes can appear both as a result of congenital pathologies, and against the background of acquired diseases or the consequences of an unhealthy lifestyle. The primary pathological process is accompanied by anomalies in the development of vertebral arches, dysplasia, the formation of cords and other abnormalities in the development of the young body. Such pathologies should be identified in the early stages of development; a timely diagnosis allows medicine to completely eliminate the risks of negative consequences.

Consequences of changes in sagittal size

The first studies on narrowing of the spinal canal were published by the journal Portal in 1803. The pathology was discovered in patients with rickets and venereal diseases at a late stage. With the development of medical science and the expansion of the number of cases studied, the classification of painful conditions caused by a decrease in the sagittal dimensions of the canal has changed. If they are caused by sequestration and disc herniation, then these conditions of the body do not belong to stenosis. Stenosis, according to modern definitions, is a long-term and slow-in-area narrowing of the canal. At the same time, negative consequences accumulate gradually; doctors have time to use effective modern treatment methods. Based on the actual values ​​of the sagittal size of the canal, the narrowing criteria are determined and the final diagnosis is made.

Spinal stenosis - diagram

Table. Main types of stenosis.

Taking into account the specific area of ​​the spine where the decrease in sagittal size is localized, the stenosis can be spinal, lateral or central.

Spinal stenosis is a chronic process characterized by pathological narrowing of the central spinal canal

Outpatient diagnostics aims to clarify not only the degree of narrowing of the canal, but also the geometry of the pathology and its nature. Taking into account these in-depth examinations, the type of stenosis is determined: total or intermittent, polysegmental or monosegmental, symmetrical on both sides of the vertebrae or unilateral.

1. Total . The pathological narrowing permanently compresses the spinal cord. The situation is very difficult, the organs for which the compressed area of ​​the brain is responsible are completely paralyzed.
2. Intermittent . The decrease in sagittal size is point-like; areas with a normal cross-section alternate with areas with a reduced cross-section. The pathology affects the spinal cord over a relatively large extent.
3. Monosegmental . The pathology concerns only one vertebra; neighboring areas have normal physiological indicators.
4. Polysegmental . Deviations are found in two or more segments of the spine; the causes can be either congenital or acquired.
5. Symmetrical . The spinal cord is compressed symmetrically on both sides or along the entire circumference. The pathology narrows the sagittal lumen in a ring-like manner.
6. One-sided . The spinal cord is compressed in only one area, on the left or right side, in front or behind.

There are several types of stenosis

Symptoms of a decrease in the sagittal size of the canal

Depending on the specific location where pathologies appear, the symptoms of the disease also change. But in all cases there is pain, it can be aching or shooting, local or diffuse, strong or weak. Increased compression causes increased pain; in the future, patients cannot do without painkillers.

If there is a problem in the lumbar spine, lameness, numbness in the legs, muscle weakness and impaired reflexes of vital functions appear. In complex cases, paresis of the limbs and dysfunction of the pelvic organs develop. In the last stages, neurodystrophic changes increase, and vegetative-vascular disorders begin. The last fourth stage of reduction in sagittal size leads to complete paralysis of the limbs.

Symptoms of lumbar stenosis

Movements[ | ]

The term flexion

,
flexio
, denote the movement of one of the bone levers around
the frontal axis
, at which the angle between the articulating bones decreases.
For example, when a person sits down, bending the knee joint decreases the angle between the thigh and shin. Movement in the opposite direction, that is, when the limb or torso is straightened and the angle between the bone levers increases, is called extension
,
extensio
.

An exception is the ankle (supratalar) joint, in which extension is accompanied by upward movement of the fingers, and when bending, for example, when a person stands on tiptoes, the fingers move downward. Therefore, foot flexion is also called plantar flexion.

, and extension of the foot is referred to as
dorsiflexion
.

Movements around the sagittal axis

are
adduction
,
adductio
, and
abduction
,
abductio
. Adduction is the movement of the bone towards the midplane of the body or (for fingers) to the axis of the limb; abduction characterizes movement in the opposite direction. For example, when the shoulder is abducted, the arm rises to the side, and the fingers are brought together to close them.

Under rotation

,
rotatio
, understand the movement of a body part or bone around its
longitudinal axis
.
For example, turning the head occurs due to the rotation of the cervical spine. Rotation of the limbs is also designated by the terms pronation
,
pronatio
, or
inward rotation
, and
supination
,
supinatio
, or
outward rotation
.
With pronation, the palm of the freely hanging upper limb turns backward, and with supination, it turns forward. Pronation and supination of the hand are carried out thanks to the proximal and distal radioulnar joints. The lower limb rotates around its axis mainly due to the hip joint; pronation orients the toe of the foot inward, and supination orients it outward. If, when moving around all three axes, the end of the limb describes a circle, such a movement is called circular
,
circumductio
.

Another type of movement is elevation

,
elevatio
- raising (abduction) of the arm above the horizontal level, which occurs with the participation of the movement of the entire girdle of the upper limb (scapula and collarbone), while raising the arm to the horizontal level occurs only in the shoulder joint.

Anterograde

movement along the natural flow of fluids and intestinal contents is called, while movement against the natural flow is called
retrograde
.
Thus, the movement of food from the mouth to the stomach is anterograde
, and with vomiting it is retrograde.

Mnemonic rules[ | ]

To remember the direction of movement of the hand during supination and pronation, an analogy with the phrase “I’m carrying soup, I spilled soup”

.

The student is asked to extend his hand forward with the palm up (forward with the limb hanging) and imagine that he is holding a plate of soup on his hand - “I’m carrying soup.”

- supination.
Then he turns his hand palm down (backward with the limb hanging freely) - “he spilled the soup”
- pronation.

Diagnostics

An accurate diagnosis can be found only after a special outpatient examination of the patient. They necessarily include methods that allow you to visually see the state of the channel. Depending on the patient’s condition, radiography, computed tomography or magnetic resonance imaging may be prescribed. Based on the images obtained, an experienced doctor can draw the right conclusions and develop effective treatment regimens. We must remember that in some cases the disease can only be localized by surgical methods. These are very complex operations and have high risks of negative consequences.

MRI of the spine