Relation Between Sacroilium and Other Pelvic Fractures Based on Real-World Automotive Accidents

The study firstly aimed at looking whether sacroilium (SI) fractures could be sustained as unique pelvic injuries in side impact real world automotive accidents. Secondarily, the sacroilium fractures observed in conjunction with other pelvic fractures were analyzed to investigate the existence of injury association patterns. Two real world accident databases were searched for SI fractures. The occupants selected were front car passengers older than 16, involved in side, oblique or frontal impact, with AIS2+ pelvic injuries. In frontal impact, only the belted occupants were selected. The cases were sorted by the principal direction of force (dof) and the type of pelvic injury, namely SI, pubic rami, iliac wing, acetabulum, pubic symphysis, and sacrum injuries. The relation between SI and pubic rami injuries were investigated first. The first database is an accident database composed of cases collected in France by car manufacturers over a period of approximately 40 years. In total it contains approximately 28 000 occupants involved in all types of accident configurations. The occupant injuries, as well as the vehicle deformations, are described in detail. The second database gathered accident cases from 7 zones monitored in Great Britain over a period ranging from 1998 to 2005. All the cases collected include at least one towed away vehicle with at least one injured occupant. In total the database contains approximately 15 000 occupants. The occupant injuries are described in details and autopsy reports were screened when available. Results - In the French database, 39 occupants sustained SI fractures. Out of 39 SI fractures, 32 were associated with pubic rami fractures and 5 additional were associated with other pelvis ring fractures. In the UK database, 46 occupants sustained SI fractures. Out of 46 SI fractures, 34 were associated with pubic rami fractures and 8 additional were associated with other pelvis ring fractures. In side impact (dof 2, 3, 4, 8, 9 or 10 o'clock), in the cases where the side is known for both the SI fractures and pelvic ring injuries, both injuries were on the same side in 70% of the cases. Overall, out of 85 SI fractures cases, only one was clearly identified as occurring with no other pelvic injury and 3 with pelvic injuries other than pelvic ring injury. Conclusions - Overall, from the real world automotive accidents selected at any dof, SI fractures were observed to be associated with other pelvic ring fractures in 96% of the cases. On the reverse, in side impact (dof 2, 3, 4, 8, 9 or 10 o'clock in the LAB database), 89% of the pubic rami fractures occurred without any SI fractures. From a mechanical standing point, it suggests that the SI fractures is a structure more resistant than the rest of the pelvic ring. Overall, 70% of SI fractures were observed in various types of side impacts and 30% in frontal impacts.