Purpose: To provide a CT-based description of the anatomic specifics of LC-1 pelvic ring disruptionsand to describe injury severity to other body systems, and their correlation with fracture anatomy.

Method: We identified a consecutive series of 100 patients with Young and Burgess LC-1 pelvic ring disruptions. The CT scan was reviewed for each patient. Sixteen categories were reviewed for each patient. Sacral fractures were graded based on severity. The age, ISS, and six categories of AIS were recorded for each patient. A statistical analysis was performed to test the associations between fracture characteristics and injury severity.

Results: All patients but three had one or more rami fractures, and all but two had a sacral fracture. Of the 98 anterior sacral injuries, there were nine (9.2%) buckles, 39 (39.8%) simple fractures, and 50 (51.0%) comminuted fractures. Of these 98 anterior sacral injuries, 47 (48.0%) were complete, passing through the sacrum and exiting the posterior cortex. Increasing severity of anterior sacrum fracture was associated with the presence of a complete sacral fracture (p value < 0.0001). Of the 98 sacral fractures, 50 (50.0%) were Denis type I, 41 (41.8%) Denis type II, and 7 (7.1%) Denis type III. Higher Denis types had higher likelihood of complete fractures of the sacrum (p value < 0.0001). There was a significant association between the presence of a comminuted rami fracture and a complete sacrum injury (p = 0.003), and a trend to higher rates in Nakatani two superior rami fractures (p = 0.169). There was a trend to higher mean ISS scores (p = 0.2287), and significantly higher abdominal AIS scores (p = 0.0014), in those with a complete sacral fracture. Those with comminuted and complete sacral fractures were more likely to be symptomatic and require posterior ring stabilization (p-value 0.003 and 0.043 respectively).

Conclusion: LC-1 fractures of the pelvic ring represent a spectrum of injuries, with a large proportion having complete disruption of the sacrum. This complete injury of the sacrum is predicted by Denis type, severity of anterior ring disruption, Abdominal AIS, and potentially location of rami fracture and ISS. CT scanning best defines these injuries.