Studies on dystocia in sheep I: A technique for radiographic pelvimetry in the ewe

Abstract

A method is described for measuring the pelvic dimensions of the ewe from one lateral and one ventro-dorsal radiograph. Estimates of the conjugate and transverse diameters of the pelvic inlet, and the distance separating the lateral ischial tuberosities, accurate to within 5% of post-mortem measurements, were obtained from 11 sheep by employing a large target-film distance and applying correction factors for each of the planes of interest. Estimates of the distance between the posterior promontories of the ischium agreed less well with post-mortem measurements, but this may be related to the difficulty in locating this point accurately at post mortem. The pelvic outlet was estimated poorly by radiographic pelvimetry (r = 0.68) and was considered to be of little value in predicting the size of the pelvic outlet at parturition.