Pelvimetry

Biometry of the pelvis is known as pelvimetry. Pelvimetry is of great importance as it marks the difference between normal and abnormal parturition. Dimensions of the pelvis vary from animal to animal and breed to breed.

In herbivores animals parturition depends upon the relationship between the shoulder diameter of the fetus (Bi shoulder Dimensions) to the sacro pubic/vertical diameter of the pelvis of the mother.

Clinical Importance of Pelvimetry:

• To predict dystocia
• It gives an idea about the internal growth of the pelvis

Pelvimetry consist of:

• Internal pelvimetry
• External pelvimetry

Internal Pelvimetry

This is done by manual examination of the interior of the pelvis through vagina or rectum. The hand may be employed in ascertaining the differential diameter by spans. The horizontal diameter of the inlet is 2.5-3 spans. Vertical diameter is around 4 spans. The internal pelvimetry can also be done using an instrument called Rice pelvimeter.

External Pelvimetry

To measure the Pelvic dimensions, a “Pelvimeter” devised by Hadia and Sane (1963) was used with modifications. It consists of three graduated linear scales of 50 cm long of which two of them were fixed at right angles at one end, while the third was so devised that it could slide freely.

Pelvic Measurements

• The distance between the two external angles of ilia (A)
• The distance between two ventral ischial tuberosities (B)
• The vertical distance from the hip joint to the level of point of croup was measured (C)

The dimensions of the inlet and outlet of pelvis were arrived on the basis of the formula suggested by Arloing as cited by Craig (1930) according to which the transverse diameter of outlet is equal to ¼ of the sum of the distance between the two external angles of ilia and the two ischial tuberosities, and the superor-inferior diameter of outlet is equal to three fourth of the vertical distance between the hip joint and the point of croup.

The sacropubic diameter of inlet is equal to 13/10 of the supero-inferior diameter of the outlet, and the transverse diameter of the inlet is equal to 12.2/10 of the transverse diameter of outlet.

Besides the above standard measurements, the distance from the external and internal angles of ilia to the dorsal ischial tuberosity was measured. The average of the two distances was considered as the length of the pelvic cavity.

Sinking of Sacrosciatic ligaments

The following procedure was adopted to measure the sinking of the pelvic ligaments. A scale was placed horizontally from the tuber-sacrale to the dorsal ischial tuberosity. Another scale was placed vertically at two different levels, mid and posterior points so that the distance between the skin and the horizontal scale could be measured directly. The measurements were taken in pregnant animals from 5^th month of pregnancy until parturition.