Reliability of vacuum phenomenon in the sacroiliac joint as a sign of traumatic injury.
OBJECTIVE
To determine whether a vacuum phenomenon in the sacroiliac joint is a reliable sign of pelvic injury in trauma patients.


METHODS
Prospective data were collected over a 1-year period for 107 patients with pelvic trauma and 104 nontrauma patients. Age ranges were 13-93 years in the trauma group and 19-83 years in the nontrauma group. All the patients had pelvic CT scans. The cases were assessed with regard to gas in the sacroiliac joint, osseous pelvic injuries, and mechanism of injury, and demographic data were analyzed. Injuries were caused by motor vehicle accidents in 67 cases, pedestrians being struck by a motor vehicle in 20, falling from a height in 18, gunshot wound in 1, and crush injury in 1. The indications for CT scan in the nontrauma patients were pain in 33 cases, infection in 31, cancer in 29, transplant in 5, bleeding in 4, and abnormal liver function tests in 2.


RESULTS
Gas in the sacroiliac joint was present in 11 out of 107 trauma patients (10%) and 12 out of 104 nontrauma patients (12%). There was no statistical difference in the incidence of the vacuum phenomenon between the two patient populations according to the Chi(2) test. Degenerative sacroiliac changes were evident in 18 out of 107 trauma patients (17%) and 32 out of 104 nontrauma patients (41%).


CONCLUSIONS
Gas in the sacroiliac joint is not a reliable indicator of sacroiliac joint injury.
Sze
Michael J
MJ
Department of Diagnostic Radiology, University of Maryland School of Medicine, 22 S. Greene Street, Baltimore, MD 21201, USA.
Mulligan
Michael J E
MJ