Pelvic
The pelvis ( pelves or pelvises) is the lower part of an anatomical trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis or pelvic skeleton)
The pelvic region of the trunk is the lower part of the trunk, between the abdomen and the thighs.
Types Of Pelvic:
There are four types of pelvic
The size of the pelvis varies not only in the two sexes, but also in different members of the same sex. The height of the individual does not appear to influence the size of the pelvis in any way, as women of short stature, in general, have a broad pelvis. Nevertheless, the pelvis is occasionally equally contracted in all its dimensions, so much so that all its diameters can measure 1.25 cm less than the average. This type of pelvis, known as a ‘justominor’ pelvis, can result in normal labour and birth if the fetal size is consistent with the size of the maternal pelvis. However, if the fetus is large, a degree of cephalopelvic disproportion will result. The same is true when a malpresentation or malposition of the fetus exists.
The principal divergences, however, are found at the brim and affect the relation of the anteroposterior to the transverse diameter. If one of the measurements is reduced by 1 cm or more from the normal, the pelvis is said to be contracted and may give rise to difficulty in labour or necessitate caesarean section.
Classically, pelvis have been described as falling into four categories: the gynaecoid pelvis, the android spelvis, the anthropoid pelvis and the platypelloid pelvis.
The Gynaecoid Pelvis:
This is the best type for childbearing as it has a rounded brim, generous forepelvis, straight side walls, a shallow cavity with a well-curved sacrum and a subpubic arch of 90°.
The Android Pelvis:
The android pelvis is so called because it resembles the male pelvis. Its brim is heart-shaped, it has a narrow forepelvis and its transverse diameter is situated towards the back. The side walls converge, making it funnel-shaped, and it has a deep cavity and a straight sacrum. The ischial spines are prominent and the sciatic notch is narrow. The subpubic angle is less than 90°. It is found in short and heavily built women, who have a tendency to be hirsute.
Because of the narrow forepelvis and the fact that the greater space lies in the hindpelvis, the heart-shaped brim favours an occipitoposterior position. Furthermore, funnelling in the cavity may hinder progress in labour. At the pelvic outlet, the prominent ischial spines sometimes pre- vent complete internal rotation of the head and the anteroposterior diameter becomes caught on them, causing a deep transverse arrest. The narrowed subpubic angle can’t easily accommodate the biparietal diameter and this displaces the head backwards. Because of these factors, this type of pelvis is the least suited to childbearing.
The Anthropoid Pelvis:
The anthropoid pelvis has a long, oval brim in which the anteroposterior diameter is longer than the transverse diameter. Straight pelvic side wall. The side walls diverge and the sacrum is long and deeply concave. The ischial spines are not prominent and the sciatic notch and the subpubic angle are very wide. Women with this type of pelvis tend to be tall, with narrow shoulders. Labour does not usually present any difficulties, but a direct occipitoanterior or direct occipitoposterior position is often a feature and the position adopted for engagement may persist to birth.
The Platypelloid Pelvis:
The platypelloid (flat) pelvis has a kidney-shaped brim in which the anteroposterior diameter is reduced and the transverse diameter increased. The sacrum is flat and the cavity shallow. The ischial spines are blunt, and the sciatic notch and the subpubic angle are both wide. The head must engage with the sagittal suture in the transverse diameter, but usually descends through the cavity without difficulty. Engagement may necessitate lateral tilting of the head, known as ‘asynclitism, in order to allow the biparietal diameter to pass the narrowest anteroposterior diameter of the brim.
Other Pelvic Variations:
High assimilation pelvis occurs when the 5th lumbar vertebra is fused to the sacrum and the angle of inclination of the pelvic brim is increased. Engagement of the head is difficult but, once achieved, labour progresses normally.Malformed pelvis may result from a developmental anomaly, dietary deficiency, injury or disease.