The role of standard roentgenograms in the evaluation of instability of pelvic ring disruption.

Anteroposterior pelvic roentgenograms of 154 patients with pelvic ring disruptions were evaluated to assess their value in the determination of pelvic instability. Three different categories of stability were roentgenographically recognizable: (1) stable, characterized by impacted vertical fracture of the sacrum, nondisplaced fracture of the posterior sacroiliac complex, and/or subtle fractures of the upper sacrum evidenced by asymmetry of the sacral arcuate lines; (2) unstable, characterized by hemipelvic cephalad displacement exceeding 0.5 cm, sacroiliac joint diastasis exceeding 1 cm and/or sacral or iliac diastatic fracture exceeding 0.5 cm; and (3) indeterminate (that is, suspicious but not diagnostic of pelvic instability), characterized by cephalad hemipelvic displacement of less than 0.5 cm, sacroiliac joint diastasis less than 1 cm, and/or diastatic fracture of the sacrum or ilium of less than 0.5 cm. Correlation of the standard roentgenographic, computed tomographic, and clinical orthopedic examinations revealed that pelvic stability was accurately evaluated on the standard pelvic roentgenograms in 88% of cases. Disruptions were stable in 70%, unstable in 18%, and suspect in 12% of patients, for whom adjunct roentgenographic and clinical examinations were required. Determination of pelvic stability in the manner described allows immediate identification of patients with a stable or unstable pelvic injury, as well as identification of those with indeterminate stability requiring further clinical or roentgenologic evaluation. Immediate recognition of pelvic instability on standard pelvic roentgenograms obviates the need for additional diagnostic studies that unnecessarily delay the institution of emergency therapeutic measures designed to control associated hemorrhage.