OTA 1999 Posters

*Loading and Protection of the Lower Leg in Vehicle Accidents

Oliver Pieske, MD (a-BMW AG/Munich); Günter C. Lob, MD; Georg Messner, Dipl. Ing. BMW; Wolfgang Lange, Dipl. Ing. BMW, Klinikum Grohadern, Ludwig-Maximilians-University Munich, Germany

Purpose: International studies show that in passenger car frontal collisions head and thorax are protected by seat-belt and airbag, whereas lower leg injuries are increasing relatively. Until recently their injury mechanism was not clarified and was investigated by this study. Possible protection strategies were evaluated.

Methods: Our analysis of over 534 car accidents since 1990 included 64 frontal collisions with serious lower leg injuries (AIS 2+). The technical analysis of the accident cars contained, among others, the measurement of the footwell (8 defined intrusion points), pedal deformation and the graduation of the energy equivalent speed (EES). Medical evaluation was based on x-rays, CT-scans and medical documentation.

Results: It could be demonstrated that longitudinal forces caused by forward movement of the occupant (inertia) and footwell/dashboard intrusion occur in frontal collsions of high overlapping type (>50%). Corresponding injuries are compression fractures typically located at the calcaneus, talus, distal tibia and tibial plateau. Opposite lateral forces are predominant in frontal collisions of low overlapping type (<50%). In these cases the footwell is intruded laterally and might lead to pedal deformation. Typical rotatory injuries of the ankle and contusion of the mid- and forefoot occur.

Discussion: Severe lower leg injuries lead to a high degree of invalidism with high socioeconomic costs. To avoid lower leg injuries in frontal car collisions seat and seating position have to be optimised individually in correlation to occupant's anthropometric size.

Although belt and airbag use lead already to a significant reduction of loading of the lower leg in frontal car collisions, further safety measures should be carried out by the automobile industry to minimize footwell intrusion and pedal deformation.

Conclusion: With this study we could demonstrate the injury mechanism of lower leg injuries in car accidents. The results should not only influence the general education of car occupants but also the safety development of the automobile industry. In our opinion, accident prevention should be an increasing topic of concern of orthopaedic surgery in terms of our fundamental aim of injury reduction.