Clinical study of vacuum phenomenon in closed pelvic fracture

BACKGROUND: This study aimed to examine the prevalence and clinical findings of the vacuum phenomenon (VP) in closed pelvic fractures. METHODS: We retrospectively reviewed 352 patients with closed pelvic fractures who presented to our institution from January 2017 to December 2020. Pelvic fractures were diagnosed by plain radiography and computed tomography (CT). The default “bone window” was used for inspection in the cross section. Electronic medical records were consulted by two orthopedic physicians to obtain patient information. The VP of pelvic fracture, fracture classification, injury mechanism, and image data were evaluated, and the demographic parameter data were statistically analyzed. The follow-up time was 12–18 months. RESULTS: Among them, 169 were males and 183 were females with ages ranging from 3 to 100 years, with an average of 49.6 ± 19.3 years. VP in pelvic fractures was detected by CT in 109 (31%) of the 352 patients with pelvic fractures. Patients were divided into the high-energy trauma group (278 cases) and fragility fractures of the pelvis (FFP) group (74 cases) according to the injury mechanism. In the high-energy trauma group, 227 cases were treated surgically and 201 cases had bony healing. The healing time was 9.8 ± 5.3 weeks. In the FFP group, 54 cases were treated surgically and 49 cases had bone healing. The healing time was 9.3 ± 3.8 weeks. Fractures progressed in nine patients. VP was mostly located in the sacroiliac joint in our study. CONCLUSIONS: The incidence of VP in pelvic fractures is statistically high and is affected by many factors, such as examination technique, joint position, population composition, etc. Therefore, the VP is not a reliable sign of pelvic injury. Clinically, we need to determine the nature of VP in conjunction with gas patterns, laboratory tests, history, and physical examination.