Proposed methods of treatment for this rare injury have included treatment of the symptoms for separations of less than one centimeter, use of a pelvic binder and absolute bed rest for painful disruptions of more than one centimeter, and even external fixation of the pelvis1-3,5-8. It has been proposed that diastasis of more than four centimeters during vaginal delivery causes tearing of the anterior sacro-iliac, sacrotuberous, and sacrospinous ligaments3,7. Injuries with this degree of separation following vaginal delivery resemble disruption of the pelvis as the result of traumatic anterior compression and may lead to rotational instability.
This reasoning, however, may not be valid when considering diastasis of the symphysis pubis due to vaginal childbirth. The injury, which radiographically may resemble a type-B1.3 injury (disruption of the pelvic ring as the result of anterior compression, with more than 2.5 centimeters of diastasis of the symphysis pubis, as defined by Tile)4, is the result of force applied from a point posterior to the symphysis pubis; this is in contrast to the more commonly seen situation in which the force is applied anterior to the symphysis pubis. This difference probably results in a different pattern of sacro-iliac injury, with preservation of the more important posterior sacro-iliac ligaments in the type of injury that we are reporting.
During pregnancy, ligamentous laxity increases because of the effects of progesterone and relaxin; this allows for greater elongation of the ligaments before they are rendered incompetent. Normally, the symphysis is widened only slightly (less than ten millimeters), but this, in conjunction with hard, precipitous labor; cephalopelvic disproportion; multiparity; or an abnormal presentation of the infant may, in rare instances, result in disruption of the symphysis pubis5. After delivery, the pelvic ligaments rapidly tighten so that the pelvis is stabilized sooner than it is after injuries that have a similar radiographic appearance but are the result of anterior-to-posterior trauma.
In our patient, the wound was irrigated vigorously and closed primarily. Another option would have been irrigation followed by packing and delayed primary closure. Disruption across a joint, the symphysis pubis, without cortical fracture or exposed bone ends and with covering by the articular cartilage may have helped to decrease the chance of wound infection in our patient.
This case report demonstrates that a large (4.7-centimeter) separation of the symphysis pubis associated with vaginal delivery can be treated satisfactorily without operative stabilization or prolonged bed rest.