The thick layer of subcutaneous fat almost completely hides the junction between abdomen and pelvis, which is indicated only by a slight indentation above the fold of the flank.
The landmarks of the pelvic skeleton are not immediately visible, but the positions of the coxal and ischial tubers are readily discoverable on palpation, which reveals the small size of the girdle in relation to the overall dimensions of the hindquarters.
The body and tuber of the ischium unite in very few pigs, and while the tuber remains unfused, there is a risk of its becoming detached by the pull of the powerful hamstring muscles that arise from it. Young sows are most commonly affected and are unable to rise when this happens; the condition is very painful, and there is no cure but slaughter.Interest in the bony pelvis is inevitably concentrated on aspects relevant to parturition. From a lateral view, the pelvic floor and the iliac shaft meet at an angle that approaches 180° (Figure 35-1). This brings the pelvic inlet, which is large and oval, into a plane that faces almost directly ventrally into the abdomen; it also carries the “vertical diameter” caudally, to intersect the part of the sacrum composed of bones not yet fused and therefore allowed some mobility. The pelvic floor slopes caudoventrally. The pelvic canal is a little higher than it is wide (Figure 35-1); the spines of the ischia are bent slightly inward to narrow the passage. If the birth canal is actually somewhat less than the skeleton suggests on account of soft tissue structures also occupying space, some compensation is to be found in the slackening of the sacrosciatic ligament, which completes the lateral wall of the pelvic cavity, and in the slackening of the joints of the girdle about the time of farrowing.