Simulation of Occipitoatlantoaxial Injury Utilizing a MADYMO Model 2004-01-0326
Injuries of the Occipitoatlantoaxial (Occ-C2) region (also known as atlanto-occipital injuries) are the most common form of cervical injury in children aged ten years and younger. The crash studied in this paper is unique in that there were three children ages 3, 6 and 7 involved in a frontal crash with a delta V of 28mph with each child receiving a nonfatal Occ-C2 injury of varying degrees. The 3 and 6 year-old children were remarkably similar in height and weight to the 3 and 6 year-old Hybrid III ATD's. Also, unique to this case is the fact that the right rear 6 year-old occupant likely sustained an Occ-C2 injury prior to impact with the frame of the front passenger seat.
This crash environment was recreated utilizing MADYMO occupant simulation software. The models for the Hybrid III 3 and 6 year-old ATDs were used to represent the occupants in this crash. The modeled neck loads were near or exceeded the neck injury criteria specified by FMVSS 208 for 3 and 6 year-old dummies interacting with inflating airbags. The non-contact Nij values peaked before significant head rotation, while neck tension peaked later in the event. These criteria for the neck represent a 3-5% risk of AIS≥3 neck injury as indicated by evidence of hemorrhage into the condylar synovial capsules and soft tissue of the Occ-C2 complex. In this crash all three children were injured with AIS=2 injuries. They showed hemmorhage around the tectorial membrane, suggesting that these children were at or near the tolerance limit for an unstable neck injury. This correlates with the model results.