Effects of Pelvic Volume Changes on Retroperitoneal and Intra-Abdominal Pressure in the Injured Pelvic Ring: A Cadaveric Model

Abstract

Pelvic ring injuries can be associated with severe blood loss and hemodynamic instability. The increase in pelvic volume in disrupted pelvic ring injuries is thought to cause accumulation of large volumes of blood in the retroperitoneal cavity. Extra abdominal compression for reduction of the pelvic ring may affect intrapelvic pressure. We examined the effects of pelvic volume changes on retroperitoneal pressures (RPP) and intra-abdominal pressures (IAPs) in the intact and unstable pelvic ring. In a cadaver study, unembalmed human torsos were used. Infusion lines were placed adjacent to the sacroiliac joint in the retroperitoneum and in the abdominal cavity. IAP and RPP measurements were performed with sequential infusion of crystalloid solution in 1,000 mL increments. Measurements were performed in the intact pelvic ring and after induction of unilateral and bilateral instability by disruption of the pubic symphysis, the sacroiliac joints, the sacrotuberous ligaments, and sacrospinous ligaments. After infusion of 4,000 mL of saline, we observed a pressure increase in the retroperitoneal cavity (RPP) of 19.64 mm Hg ± 6.43 mm Hg in the intact pelvis, 5.22 mm Hg ± 1.74 mm Hg in unilateral instability, and 2.78 mm Hg ± 0.57 mm Hg in bilateral instability. The RPP response in the case of instability decreased significantly (p = 0.019). The IAP showed a change of 4.63 mm Hg ± 2.64 mm Hg in the intact pelvis, 3.88 mm Hg ± 1.84 mm Hg in unilateral instability, and 2.30 mm Hg ± 0.36 mm Hg in bilateral instability. Further infusion revealed a close association between RAPs and IAPs. In the intact pelvis, RPP rises rapidly with increasing volume. The results seem to support the idea that disrupted pelvic ring fractures may lead to a significant volume uptake that is reversed during reduction.