Understanding fracture mechanisms of the upper extremities in car accidents

The aim of this study was to understand injury mechanisms behind fractures of the upper extremities in car accidents. Volvo Car Corporation initiated this project based on the fact that no safety system today focuses on preventing injuries to the upper extremity. A literature study was undertaken focusing on the basic anatomy of the upper extremity, different fracture types and fracture mechanisms. Three subsets, from 1998 – January 2009, were selected from Volvo’s statistical accident database: 1) all occupants involved in an accident 2) all occupants with a MAIS2+ injury 3) all occupants with an upper extremity fracture. These subsets were used in a comparison, using frequency analyses. The comparison analysis showed that frontal impact is the dominating accident type for all three subsets. The comparison analysis also indicated that the risk for upper extremity fractures follows the pattern of MAIS2+ injury risk. An in-depth study using 92 selected cases, including 80 occupants, was also performed. All available information, such as medical records, questionnaires completed by the occupants and photographs from the accident scene was collected and analysed. The analysis of the in-depth study, together with knowledge retrieved from the literature study, resulted in six different mechanism groups that were used to categorise fractures. The groups were then analysed individually in regard to accident type and fractured segment of the upper extremity. Analysis of the mechanism groups showed that frontal impact is the dominating accident type in these subsets as well. It could also be seen that the fractures occurring in the in-depth study are quite evenly distributed along the upper extremities. Upper extremity injuries are relatively infrequent in car accidents but may result in long-term disability, including chronic deformity, pain, weakness and loss of motion. More attention is therefore necessary in order to develop a safer environment for car occupants