Female pelvis in point of obstetrics

Female pelvis in point of obstetrics

1. FEMALE PELVIS IN POINT OF OBSTETRICS Divided into large and small pelvis Border between them goes along the innominate line ( linea innominate) Large pelvis is bounded on the side by wings of ilia and posteriorly by the spine

2. Small pelvis is formed by pubic bones branches from the front, by part of the bones forming the femoral fossa on the sides by the sacral and pelvic bones from behind Small pelvis defines the dimensions, forms and direction of the parturient canal, to which the fetus moves and must conform, changing its own configuration Measurement of the pelvis usually involves measuring the external dimensions, three transverse and one straight This is done by the use of pelvimeter Distantia spinarum is the distance between the anterosuperior axes of the ilia (25cm) Distantia cristarum is the distance between the most distant part points of the iliac crest (28 cm on average) Distantia trochanterica is the distance between the greater trochanters (21 cm)

3. Conjugate externa is the straight dimension of the pelvis (20cm) Dimention of small pelvis is of great importance in obstetrics but most can not be measured directly The small pelvis cavity is the space between its walls, limited from above and from below by the area of brim and pelvis outlet Looks like a cylinder with the anterior part directed towards the womb and posterior part to the sacral bone

4. Four planes in the pelvic cavity; area of the brim, pelvic plane of greatest dimensions, the third parallel pelvic plane and the area of pelvic outlet Area of the brim borders posteriorly by the promontory of sacral bone Laterally by terminal lines of hip bones Anteriorly by upper margin of pubic bone and symphysis Four dimensions can be identified in the brim True or obstetric conjugate ( conjugata vera ) is measured from the promontory of sacral bone to the most protruding point of superointernal margin of symphysis (11cm)

5. Conjugata anatomica is the distance from the promontory of sacral bone to upper margin of symphysis (0.3 cm) Transverse dimention is the distance between utmost points of the arcuate lines of ilia ( linea innominate). (13 cm) Oblique dimension ( left and right) distance from left sacroiliac joint to the right iliopubic eminence and vice versa .(12 cm)

6. Pelvic plane of greatest dimension borders Posteriorly by the junction of the second and third sacral vertebrae Lateral-middle of femoral fossa Anteriorly-middle of internal surface of symphysis Two dimensions are differentiated in this plane, straight and transverse Straight makes 12.5 cm Transverse makes 12.5cm

7. The third parallel pelvis Borders ; anteriorly–inferior margin of symphysis , posteriorly – sacrococcygeal joint, laterally – axes of ischial bone Two dimensions ; straight (11 cm) and transverse (10.5cm) Area of pelvic outlet Borders; anteriorly- inferior margin of symphysis , posteriorly- pelvic bone apex, lateral- internal surface of ischial tuberosity. Dimensions are straight and transverse Straight dimension- midline of inferior margin of symphysis to pelvic to the pelvic bone apex. (9.5 cm) Transverse dimension-between internal surfaces of ischial tuberosities . (11 cm) Dimension of the pelvic outlet can be measured directly

8. Diagonal conjugate = 12.5 cm i.e. 1.5 cm longer than the true conjugate. From the tip of sacral promontory to the lower border of symphysis pubis. External conjugate = 20 cm from the depression below the last lumbar spine to the upper anterior margin of the symphysis pubis measured from outside by the pelvimeter . It has no true obstetric importance.