By puberty, a healthy woman’s pelvis should have a normal shape and size for a woman. To form a correct pelvis, the girl’s normal development during the prenatal period, prevention of rickets, good physical development and nutrition, natural ultraviolet radiation, injury prevention, normal hormonal and metabolic processes are necessary.

The pelvis (pelvis) consists of two pelvic, or nameless, bones, the sacrum (os sacrum) and the coccyx (os coccygis). Each pelvic bone consists of three fused bones: the ilium (os ilium), the ischium (os ischii) and the pubis (ospubis). The pelvic bones are connected in front by the symphysis. This inactive joint is a semi-joint in which the two pubic bones are connected by cartilage. The sacroiliac joints (almost immobile) connect the lateral surfaces of the sacrum and the ilia. The sacrococcygeal joint is a movable joint in women. The protruding part of the sacrum is called the promontory.

Measuring the size of the pelvis.

To assess pelvic capacity, 3 external dimensions of the pelvis and the distance between the femurs are measured. Measuring the pelvis is called pelvimetry and is carried out using a pelvimeter.

External dimensions of the pelvis:

1. Distancia spinarum - interspinous distance - the distance between the anterosuperior spines of the iliac bones (spine - spina), in a normal pelvis is 25-26 cm.
2. Distancia cristarum - intercrestal distance - the distance between the most distant points of the iliac crests (crest - crista), normally equals 28-29 cm.
3. Distancia trochanterica - intertubercular distance - the distance between the large tuberosities of the trochanters of the femurs (greater tuberosity - trochanter major), normally equals 31 cm.
4. Conjugata externa - external conjugate - the distance between the middle of the upper edge of the symphysis and the suprasacral fossa (the depression between the spinous process of the V lumbar and I sacral vertebrae). Normally it is 20-21 cm.

When measuring the first three parameters, the woman lies in a horizontal position on her back with her legs extended, and the pelvic meter buttons are placed on the edges of the size. When measuring the direct size of the wide part of the pelvic cavity. To better identify the greater trochanters, the woman is asked to bring her toes together. When measuring the external conjugate, the woman is asked to turn her back to the midwife and bend her lower leg.

Michaelis rhombus

- this is an expansion of the depression in the sacral region, the limits of which are: above - the fossa under the spinous process of the fifth lumbar vertebra (supracrigian fossa), below - the points corresponding to the posterosuperior spine of the iliac bones. The average length of a rhombus is 11 cm, and its diameter is 10 cm.

Diagonal conjugate

– the distance from the lower edge of the symphysis to the most protruding point of the promontory of the sacral bone is determined during vaginal examination. With normal pelvic sizes it is 12.5-13 cm.

The size of the true conjugate (direct size of the entrance to the small pelvis) is determined by subtracting 9 cm from the length of the external conjugate or subtracting 1.5-2 cm from the length of the diagonal conjugate (depending on the Solovyov index).

Solovyov index

- the circumference of the wrist-carpal joint, divided by 10. The index allows you to have an idea of ​​​​the thickness of a woman’s bones. The thinner the bones (index = 1.4-1.6), the greater the capacity of the small pelvis. In these cases, 1.5 cm is subtracted from the diagonal conjugate to obtain the length of the true conjugate. If the Solovyov index is 1.7-1.8, 2 cm is subtracted.

Pelvic tilt angle

– the angle between the plane of the entrance to the small pelvis and the horizon is 55-60 °. Deviations in one direction or another can negatively affect the course of labor.

The normal height of the symphysis is 4 cm and is measured with the index finger during vaginal examination. Pubic angle - with normal pelvic sizes is 90-100 °.

Small pelvis

- This is the bony part of the birth canal. The posterior wall of the small pelvis consists of the sacrum and coccyx, the lateral ones are formed by the ischium, and the anterior wall is formed by the pubic bones and the symphysis. The small pelvis has the following sections: inlet, cavity and outlet.

In the pelvic cavity there are wide and narrow parts. In this regard, four planes of the pelvis are determined:

1 – plane of entrance to the small pelvis.

2 – plane of the wide part of the pelvic cavity.

3 – plane of the narrow part of the pelvic cavity.

4 – plane of exit from the pelvis.

The plane of entry into the pelvis passes through the upper inner edge of the pubic arch, the innominate lines and the apex of the promontory. The following dimensions are distinguished in the entrance plane:

1. Direct size - the distance from the sacral protrusion to the point that protrudes most on the upper inner surface of the symphysis - this is the obstetric, or true conjugate, equal to 11 cm.
2. Transverse size is the distance between the distant points of the arcuate lines, which is 13-13.5 cm.
3. Two oblique dimensions - from the iliosacral junction on one side to the iliopubic tubercle on the opposite side of the pelvis. They are 12-12.5 cm.

The plane of the wide part of the pelvic cavity passes through the middle of the inner surface of the pubic arch, on the sides through the middle of the trochanteric cavity and behind - through the connection between the II and III sacral vertebrae.

In the plane of the wide part of the small pelvis there are:

1. Direct size - from the middle of the inner surface of the pubic arch to the junction between the II and III sacral vertebrae. It is 12.5 cm.
2. The transverse dimension runs between the middles of the acetabulum. It is 12.5 cm.

The plane of the narrow part is through the lower edge of the pubic joint, on the sides - through the gluteal spines, in the back - through the sacrococcygeal joint.

In the plane of the narrow part they are distinguished:

1. Straight size - from the lower edge of the symphysis to the sacrococcygeal joint. It is equal to II.5cm.
2. The transverse dimension between distant points of the inner surface of the ischial spines. It is equal to 10.5 cm.

The plane of exit from the small pelvis passes in front through the lower edge of the symphysis, from the sides - through the tops of the gluteal tuberosities, and from behind - through the crown of the coccyx.

In the plane of exit from the small pelvis there are:

1. Straight size - from the tip of the coccyx to the lower edge of the symphysis. It is equal to 9.5 cm, and when the fetus passes through the pelvis it increases by 1.5-2 cm due to the deviation of the apex of the coccyx of the presenting part of the fetus.
2. Transverse size - between distant points of the internal surfaces of the ischial tuberosities; it is equal to 11cm.

The line connecting the midpoints of the straight dimensions of all planes of the pelvis is called the leading axis of the pelvis, and has the shape of a concave line forward. It is along this line that the leading point passes through the birth canal.

Table of contents of the topic "The pelvis from an obstetric point of view. Physiology of the female reproductive system.":

2. Dimensions of the plane of the wide part of the small pelvis. Dimensions of the plane of the narrow part of the small pelvis.
3. Wired pelvic axis. Pelvic inclination angle.
4. Physiology of the female reproductive system. Menstrual cycle. Menses.
5. Ovaries. Cyclic changes in the ovaries. Primordial, preantral, antral, dominant follicle.
6. Ovulation. Yellow body. Female hormones synthesized in the ovaries (estradiol, progesterone, androgens).
7. Cyclic changes in the uterine mucosa (endometrium). Proliferation phase. Secretion phase. Menstruation.
8. The role of the central nervous system in the regulation of menstruation. Neurohormones (luteinizing hormone (LH), follicle-stimulating hormone (FSH).
9. Types of feedback. The role of the feedback system in the regulation of menstrual function.
10. Basal temperature. Pupil symptom. Karyopyknotic index.

Big pelvis for the birth of a child is not significant. The bony basis of the birth canal, which represents an obstacle to the fetus being born, is the small pelvis. However, by the size of the large pelvis one can indirectly judge the shape and size of the small pelvis. The inner surface of the large and small pelvis is lined with muscles.

Rice. 2.7. Female pelvis (sagittal section).
1 - anatomical conjugate;
2 - true conjugate;
3 - direct dimension of the plane of the wide part of the pelvic cavity;
4 - direct dimension of the plane of the narrow part of the pelvic cavity;
5 - direct size of the pelvic outlet with the normal position of the coccyx;
6 - direct size of the pelvic outlet with the tailbone bent posteriorly;
7 - wire axis of the pelvis.

Pelvic cavity is the space enclosed between the walls of the pelvis, limited above and below by the planes of inlet and outlet of the pelvis. It has the appearance of a cylinder, truncated from front to back, with the front part facing the womb almost 3 times lower than the back part facing the sacrum. Due to this shape of the pelvic cavity, its various parts have different shapes and sizes. These sections are imaginary planes passing through identification points of the inner surface of the pelvis. In the small pelvis, the following planes are distinguished: the entrance plane, the wide part plane, the narrow part plane and the exit plane (Table 2.1; Fig. 2.7).

Plane of entry into the pelvis passes through the upper inner edge of the pubic arch, the innominate lines and the apex of the promontory. In the entrance plane, the following dimensions are distinguished (Fig. 2.8).

Straight size- the shortest distance between the middle of the upper inner edge of the pubic arch and the most prominent point of the cape. This distance is called true conjugata (conjugata vera); it is equal to 11 cm. It is also customary to distinguish the anatomical conjugate - the distance from the middle of the upper edge of the pubic arch to the same point of the promontory; it is 0.2-0.3 cm longer than the true conjugate (see Fig. 2.7).

Transverse size- the distance between the most distant points of the nameless lines of opposite sides. It is equal to 13.5 cm. This size intersects the true conjugate at a right angle eccentrically, closer to the cape.

Rice. 2.8. Dimensions of the plane of entry into the small pelvis.
1 - direct size (true conjugate);
2 - transverse size;
3 - oblique dimensions.

Oblique dimensions - right and left. The right oblique dimension goes from the right sacroiliac joint to the left iliopubic tubercle, and the left oblique dimension goes from the left sacroiliac joint to the right iliopubic tubercle. Each of these sizes is 12 cm.

As can be seen from the given dimensions, the entrance plane has a transverse oval shape.

The plane of the wide part of the pelvic cavity passes in front through the middle of the inner surface of the pubic arch, on the sides - through the middle of the smooth plates located under the fossae of the acetabulum (lamina acetabuli), and behind - through the articulation between the II and III sacral vertebrae.

Table 2.1 Planes and dimensions of the small pelvis

SMALL PELVIS Planes and dimensions of the small pelvis. The pelvis is the bony part of the birth canal. The posterior wall of the small pelvis consists of the sacrum and coccyx, the lateral ones are formed by the ischial bones, and the anterior wall is formed by the pubic bones and the symphysis. The posterior wall of the pelvis is 3 times longer than the anterior one. The upper pelvis is a continuous, inflexible ring of bone. In the lower section, the walls of the small pelvis are not solid; they contain obturator foramina and sciatic notches, bounded by two pairs of ligaments (sacrospinous and sacrotuberous). In the small pelvis there are the following sections: inlet, cavity and outlet. In the pelvic cavity there are a wide and a narrow part. In accordance with this, four planes of the pelvis are considered: I – the plane of the entrance to the pelvis, II – the plane of the wide part of the pelvic cavity, III – the plane of the narrow part of the pelvic cavity, IV – the plane of the exit of the pelvis.

I. The plane of entrance to the small pelvis has the following boundaries: in front - the upper edge of the symphysis and the upper inner edge of the pubic bones, on the sides - innominate lines, behind - the sacral promontory. The entrance plane has the shape of a kidney or a transverse oval with a notch corresponding to the sacral promontory. At the entrance to the pelvis there are three sizes: straight, transverse and two oblique. Straight size - the distance from the sacral promontory to the most prominent point on the inner surface of the pubic symphysis. This size is called the obstetric, or true, conjugate (conjugata vera). There is also an anatomical conjugate - the distance from the promontory to the middle of the upper inner edge of the symphysis; the anatomical conjugate is slightly (0.3-0.5 cm) larger than the obstetric conjugate. The obstetric or true conjugate is 11 cm. The transverse size is the distance between the most distant points of the nameless lines. This size is equal to 13-13.5 cm. There are two oblique sizes: right and left, which are equal to 12-12.5 cm. The right oblique size is the distance from the right sacroiliac joint to the left iliopubic tubercle, the left oblique size is from left sacroiliac joint to the right iliopubic tubercle. In order to more easily navigate in the direction of the oblique dimensions of the pelvis in a woman in labor, M.S. Malinovsky and M.G. Kushnir suggests the following technique. The hands of both hands are folded at right angles, with the palms facing upward; the ends of the fingers are brought closer to the outlet of the pelvis of the lying woman. The plane of the left hand will coincide with the left oblique size of the pelvis, the plane of the right hand will coincide with the right.

II. The plane of the wide part of the pelvic cavity has the following boundaries: in front - the middle of the inner surface of the symphysis, on the sides - the middle of the acetabulum, in the back - the junction of the II and III sacral vertebrae. In the wide part of the pelvic cavity, two sizes are distinguished: straight and transverse. Direct size - from the junction of the II and III sacral vertebrae to the middle of the inner surface of the symphysis; equal to 12.5 cm. Transverse size - between the apices of the acetabulum; equal to 12.5 cm. There are no oblique dimensions in the wide part of the pelvic cavity because in this place the pelvis does not form a continuous bone ring. Oblique dimensions in the widest part of the pelvis are conditionally allowed (length 13 cm).

III. The plane of the narrow part of the pelvic cavity is limited in front by the lower edge of the symphysis, on the sides by the spines of the ischial bones, and behind by the sacrococcygeal joint. There are two sizes: straight and transverse. The straight dimension goes from the sacrococcygeal joint to the lower edge of the symphysis (apex of the pubic arch); equal to 11-11.5 cm. The transverse dimension connects the spines of the ischial bones; equal to 10.5 cm.

IV. The plane of exit of the small pelvis has the following boundaries: in front - the lower edge of the symphysis, on the sides - the ischial tuberosities, in the back - the apex of the coccyx. The exit plane of the pelvis consists of two triangular planes, the common base of which is the line connecting the ischial tuberosities. There are two sizes of the pelvic outlet: straight and transverse. The direct size of the pelvic outlet goes from the apex of the coccyx to the lower edge of the symphysis; it is equal to 9.5 cm. When the fetus passes through the small pelvis, the coccyx moves away by 1.5-2 cm and the direct size increases to 11.5 cm. The transverse size of the pelvic outlet connects the internal surfaces of the ischial tuberosities; equal to 11 cm. Thus, at the entrance to the pelvis, the largest dimension is the transverse one. In the wide part of the cavity, the straight and transverse dimensions are equal; the largest size will be the conventionally accepted oblique size. In the narrow part of the cavity and the pelvic outlet, the straight dimensions are larger than the transverse ones. In addition to the above (classical) pelvic cavities, parallel planes of the pelvis (Goji planes) are distinguished. The first (upper) plane passes through the terminal line (I. terminalis innominata) and is therefore called the terminal plane. The second is the main plane, running parallel to the first at the level of the lower edge of the symphysis. It is called the main one because the head, having passed this plane, does not encounter significant obstacles, since it has passed a solid bone ring. The third is the spinal plane, parallel to the first and second, crossing the pelvis in the spina oss area. ischii. The fourth, the exit plane, represents the pelvic floor (its diaphragm) and almost coincides with the direction of the coccyx. Wired axis (line) of the pelvis. All planes (classical) of the pelvis border in front with one or another point of the symphysis, and in the back - with different points of the sacrum or coccyx. The symphysis is much shorter than the sacrum and coccyx, so the planes of the pelvis converge anteriorly and fan out posteriorly. If you connect the middle of the straight dimensions of all the planes of the pelvis, you will get not a straight line, but a concave anterior (towards the symphysis) line. This conditional line connecting the centers of all direct dimensions of the pelvis is called the wire axis of the pelvis. The wire axis of the pelvis is initially straight; it bends in the pelvic cavity according to the concavity of the inner surface of the sacrum. In the direction of the wire axis of the pelvis, the born fetus passes through the birth canal.

The angle of inclination of the pelvis (the intersection of the plane of its entrance with the plane of the horizon) when a woman is standing can vary depending on the body type and ranges from 45-55°. It can be reduced by forcing a woman lying on her back to strongly pull her thighs towards her stomach, which leads to elevation of the womb. It can be increased by placing a roll-shaped hard pillow under the lower back, which will lead to a downward deviation of the womb. A decrease in the angle of inclination of the pelvis is also achieved if the woman is given a semi-sitting position, squatting.

Structure and purpose of the bony pelvis

The birth canal includes both the bony pelvis and the soft tissues of the birth canal (uterus, vagina, pelvic floor and external genitalia).

1. Bone pelvis. (Pelvis)

It is a combination of 4 bones:

2 x unnamed (ossa innominata)

Sacrum (os sacrum)

Coccyx (os coccygeum)

The innominate bones are connected to each other through the pubic articulation (symphysis), to the sacrum through the right and left sacroiliac joints (articulatio sacroiliac dextra et sinistra).

The coccyx is connected to the sacrum through the sacrococcygeal joint (acticulatio sacro-coccygeum).

The pelvis is divided into large and small

a) The pelvis is that part of the bone canal that is located above its innominate or border line (linea innominata, s. terminalis). The lateral walls are the iliac fossa of the innominate bones (fossa iliaca dextra et sinistra). The large pelvis is open in front, and limited in the back by the lumbar part of the spine (IV and V vertebrae).

The size of the small pelvis is judged by the size of the large pelvis.

b) The pelvis is that part of the bone canal that is located below the innominate or border line. Most important in an obstetric sense. Knowing its size is necessary to understand the biomechanism of childbirth. Moving in the pelvis, the fetus is subjected to the greatest loads - compression, rotation. Deformation of the bones of the fetal head is possible.

The walls of the small pelvis are formed: in front - by the inner surface of the symphysis pubis, on the sides - by the inner surfaces of the innominate bones, in the back - by the inner surface of the sacrum.

Classic pelvic planes

Pelvic planes:

a) plane of entrance to the pelvis;

b) the plane of the wide part;

c) the plane of the narrow part;

d) the plane of the pelvic outlet.

I. The boundaries of the plane of entrance to the small pelvis are the promontory of the sacrum, the innominate line and the upper edge of the symphysis.

Dimensions of the entrance to the pelvis:

1) Straight - true conjugata (conjugata vera) - from the most protruding point of the inner surface of the womb to the promontory of the sacrum - 11 cm.

2) Transverse size - connects the most distant points of the border line - 13-13.5 cm.

3) Two oblique dimensions: right - from the right sacroiliac joint to the left iliopubic tubercle (eminentia-iliopubica sinistra) and left - from the left sacroiliac joint to the right iliopubic tubercle.

Oblique dimensions are 12-12.5 cm.

Normally, the oblique dimensions are considered the dimensions of the typical insertion of the fetal head.

II. The plane of the wide part of the pelvic cavity.

The front boundaries are the middle of the inner surface of the symphysis pubis, the back is the line of connection of the 2nd and 3rd sacral vertebrae, the sides are the middle of the acetabulum (lamina accetabuli).

Dimensions of the wide part of the pelvic cavity:

straight size - from the upper edge of the 3rd sacral vertebra to the middle of the inner surface of the symphysis - 12.5 cm;

transverse size - between the midpoints of the acetabulum 12.5 cm;

oblique dimensions - conventionally from the upper edge of the greater sciatic notch (incisura ischiadica major) on one side to the groove of the obturator muscle (sulcus obturatorius) - 13 cm.

III. The plane of the narrow part of the pelvic cavity.

Borders: in front - the lower edge of the pubic symphysis, behind - the apex of the sacrum, on the sides - the ischial spines (spinae ischii).

Dimensions of the narrow part of the pelvic cavity:

straight size - from the apex of the sacrum to the lower edge of the symphysis pubis (11-11.5 cm);

transverse size - line connecting the ischial spines - 10.5 cm.

IV. The plane of exit of the small pelvis.

Borders: in front - the pubic arch, behind - the apex of the coccyx, on the sides - the inner surfaces of the ischial tuberosities (tubera ischii).

Pelvic outlet dimensions:

straight size - from the lower edge of the pubic symphysis to the apex of the coccyx - 9.5 cm, with deviation of the coccyx - 11.5 cm;

transverse size - between the inner surfaces of the ischial tuberosities - 11 cm.

Pelvic wire line (pelvic axis).

If you connect the centers of all direct dimensions of the pelvis with each other, you get a concave anterior line, which is called the wire axis, or the pelvic line.

The wire axis of the pelvis first goes in the form of a straight line until it reaches the plane intersecting the lower edge of the symphysis, the so-called main one. From here, a little lower, it begins to bend, crossing at right angles a successive series of planes that go from the lower edge of the symphysis to the sacrum and coccyx. If this line is continued upward from the center of the entrance to the pelvis, it will cross the abdominal wall at the navel; if it is continued downwards, it will pass through the lower end of the coccyx. As for the axis of exit of the pelvis, then, being continued upward, it will cross the upper part of the first sacral vertebra.

The fetal head, when passing through the birth canal, cuts through a series of parallel planes with its circumference until it reaches the pelvic floor with a wire point. These planes through which the head passes are called parallel planes by Goji.

Of the parallel planes, the most important are the following four, which are spaced from each other at almost equal distances (3-4 cm).

The first (upper) plane passes through the terminal line (linea terminalis) and is therefore called the terminal plane.

The second plane, parallel to the first, intersects the symphysis at its lower edge - the inferior parallel plane. It is called the main plane.

The third plane, parallel to the first and second, intersects the pelvis in the spinae ossis ischii region - this is the spinal plane.

Finally, the fourth plane, parallel to the third, represents the pelvic floor, its diaphragm and almost coincides with the direction of the coccyx. This plane is usually called the output plane.

Pelvic inclination is the ratio of the plane of the entrance to the pelvis to the horizontal plane (55-60 degrees). The angle of inclination can be slightly increased or decreased by placing a cushion under the lower back and crosses for the lying woman.

Pelvic floor

The pelvic floor is a powerful muscular-fascial layer consisting of three layers.

I. Bottom (outer) layer.

1. Bulbocavernosus (m. bulbocavernosus) compresses the vaginal opening.

2. Ischio-cavernosus (m. ischocavernosus).

3. Superficial transverse muscle of the perineum (m. transversus perinei superficialis).

4. external sphincter of the anus (m. sphincter ani externus).

II. The middle layer is the urogenital diaphragm (diaphragma urogenitale) - a triangular muscular-fascial plate located under the symphysis, in the pubic arch. Its posterior part is called the deep transverse muscle of the perineum (m. transversus perinei profundus).

III. The upper (inner) layer - the pelvic diaphragm (diaphragma pelvis) consists of a paired muscle that lifts the ani (m. levator ani).

Functions of the muscles and fascia of the pelvic floor.

1. They provide support for the internal genital organs and help maintain their normal position. During contraction, the genital fissure closes, narrowing the lumen of the rectum and vagina.

2. They support the viscera and participate in the regulation of intra-abdominal pressure.

3. During labor and expulsion, all three layers of the pelvic floor muscles stretch and form a wide tube, which is a continuation of the bony birth canal.

Obstetric (anterior) perineum - part of the pelvic floor between the posterior commissure of the labia and the anus.

The posterior perineum is the part of the pelvic floor, between the anus and the tailbone.

LITERATURE:

BASIC:

1. Bodyazhina V.I., Zhmakin K.N. Obstetrics, M., Medicine, 1995.

2. Malinovsky M.R. Operative obstetrics. 3rd ed. M., Medicine, 1974.

3. Serov V.N., Strizhakov A.N., Markin S.A. Practical obstetrics. M., Medicine, 1989. - 512 p.

4. Chernukha E.A. Maternity block. M., Medicine, 1991.

ADDITIONAL:

1. Abramchenko V.V. Modern methods of preparing pregnant women for childbirth. S. Petersburg., 1991. - 255 p.

2. Directory of a doctor at the antenatal clinic. Ed. Gerasimovich G.I.

In the pelvic cavity there are conventionally 4 classical planes.

I plane- entry plane:

front-upper edge of symphysis

behind– cape

from the sides- unnamed line.

Straight Entry Size(between the middle of the upper inner edge of the symphysis and the promontory) coincides with the true conjugate (conjuqata vera) = 11 cm. (or obstetric conjugate)

Transverse size– distance between the most distant points of the border line = 13 cm.

Two oblique sizes– from the sacroiliac joint to the opposite iliopubic tubercle = 12 cm.

The distance from the middle of the upper edge of the pubic arch to the promontory = 11.5 cm and is called anatomical conjugate.

The plane of entrance to the small pelvis has a transverse oval shape.

II plane– plane of the wide part:

front– the middle of the inner surface of the womb

behind- articulation of the II and III sacral vertebrae

from the sides– projections of the acetabulum

Straight size– the distance between the middle of the inner surface of the pubic symphysis to the articulation of the II and III sacral vertebrae = 12.5 cm

Transverse size– connects the plates of the acetabulum = 12.5 cm

This plane has a rounded shape.

III plane – the plane of the narrow part of the pelvis.

front– lower edge of the symphysis

behind- sacrococcygeal joint

from the sides– ischial spines

Straight size– between the lower symphysis and the sacrococcygeal joint = 11cm

Transverse size– between the inner surfaces of the ischial spines = 10.5 cm

This plane has the shape of a longitudinal oval.

IY plane– plane of exit of the small pelvis.

Front– lower edge of the symphysis

Behind– edge of the coccyx

From the sides– ischial tuberosities

Straight size– from the lower edge of the symphysis to the coccyx = 9.5 cm, the coccyx moves away during childbirth by 1.5-2 cm

Transverse size– between the inner surfaces of the sit bones = 10.5 cm

This plane has the shape of a longitudinal oval at the origin of the coccyx.

Wired line, or pelvic axis, passes through the intersection of the straight and transverse dimensions of all planes.

Internal dimensions of the pelvis can be measured using ultrasonic pelviometry, but is not yet widely used.

At vaginal examination the correct development of the pelvis can be assessed. If the promontory is not reached during examination, this is a sign of a capacious pelvis, and if it is reached, then measure diagonal conjugate(the distance between the lower outer edge of the symphysis and the promontory), which is normally d.b. at least 12.5-13cm.

Measuring diagonal conjugates.

The internal dimensions of the pelvis and the degree of narrowing are judged by true conjugate(direct size of the entry plane), which in a normal pelvis is at least 11 cm

The true conjugate is calculated using 2 formulas:

Ø true conjugate = outer conjugate minus 9-10cm

Ø true conjugate = diagonal conjugate minus 1.5-2cm

(for thick bones, the maximum number is subtracted, for thin bones, the minimum).

To assess bone thickness, it is proposed Solovyov index(wrist circumference)

If the index is less than 14-15 cm, the bones are considered thin,

if more than 15cm - thick.

The size and shape of the pelvis can also be judged by

shape and size of the Michaelis rhombus, which

corresponds to the projection of the sacrum.

Its upper angle corresponds to the suprasacral

fossa, lateral – posterosuperior iliac spines

nym bones, the lower one - the apex of the coccyx.

The dimensions of the exit plane, as well as the external dimensions of the pelvis, can also be measured using a pelvis gauge.

Pelvic tilt angle– the angle between the plane of its entrance and the horizontal plane. When a woman is in a vertical position, it = 45-55 o. it decreases if the woman squats or lies in a gynecological position with her legs bent and drawn towards her stomach (a possible position during childbirth). The same provisions allow you to increase the direct size of the exit plane. The angle of inclination of the pelvis increases if a woman lies on her back with a bolster under her back, or if she bends backward in an upright position. The same happens if a woman lies on a gynecological chair with her legs down (Walcher position). The same provisions allow you to increase the direct size of the entrance.

Pubic corner measured in the pregnant position

on the gynecological chair. Thumbs

both hands are placed along the descending branches

pubic bone. Normally, the pubic angle is 90-100 o

Straight pelvic outlet size- distance between

the middle of the lower edge of the symphysis pubis and the ver-

coccyx. During the examination, the patient lies

on the back with legs apart and half-bent at the hip and knee joints. One button of the pelvis gauge is installed in the middle of the lower edge of the symphysis pubis, the other - at the top of the coccyx. The direct size of the pelvic outlet = 11 cm, 1.5 cm larger than the true one due to the thickness of the soft tissues. Therefore, it is necessary to subtract 1.5 cm from the resulting figure of 11 cm in order to find the direct size of the outlet of the pelvic cavity, which is equal to 9.5 cm.

Transverse size of the pelvic outlet- distance

between the inner surfaces of the ischial

mounds. It is determined in the pregnant position

noah on her back, she presses her legs as close as possible to

stomach. The measurement is made with a special pelvis or measuring tape, which is applied not directly to the ischial tuberosities, but to the tissues covering them; therefore, to the resulting dimensions of 9-9.5 cm, it is necessary to add 1.5 - 2 cm (thickness of soft tissues). Transverse size of the pelvic outlet = 11 cm.

To clarify the shape of the narrowing, data from additional measurements can be used:

- side Kerner conjugates– the difference in values ​​between both conjugates indicates asymmetry of the pelvis, and a symmetrical decrease in the conjugate indicates the presence of a pelvic plane

- oblique dimensions– a difference between the right and left sizes of more than 1.5 cm has diagnostic significance, which indicates pelvic asymmetry

- pelvic circumference – between the trochanters and paddle iliac bones of the pelvis (85 cm or more).