Session I - Upper Extremity

Fractures of the Upper Extremity in Restrained Car Drivers

Martinus Richter MD; Michael Blauth, MD; Dietmar Otte; Kaneschka Jahanyar; Harald Tscherne, MD, Medical School Hannover, Hannover, Germany

Hypothesis/Purpose: In motor vehicles, the extremities are not specially secured. However, the "restraining effects" of safety belts and cushioning of the airbag have lowered the collision impact for the extremities. In our study, the actual frequency of upper extremity fractures in restrained car drivers was evaluated first and then injury origin, type and extent were evaluated. The aim of our study is to analyze the accident mechanism of upper extremity fractures, to create a basis for developing prophylactic devices. Only restrained drivers were examined as a representative collective since driver restraint status was greater than 90% with a car occupation quota of 1.3.

Summary of Methods/Results: 12,428 injured persons in 9,380 car crashes were evaluated between 1985 and 1995. Scientific teams had been informed directly via police radio and arrived at the accident scenes quickly in their own operation vehicles. In addition to technical indications and an evaluation of the damage to the car, the files also included medical details concerning injuries to persons and the degree of their seriousness. Pictures of the vehicular collision scene and the cars from outside and inside as well as of the clinical aspects of the injuries and the relevant radiographs or CT scans were also included. The injury severity was classified upon the Abbreviated Injury Scale (AIS) for the upper extremity. The location and morphology of fractures to the long tubular bones were classified according to the AO fracture classification, which is similar to the OTA classification. The soft tissue injuries were classified according to the Tscherne classification.

Among 3,620 restrained injured drivers, 711 (21.8%) sustained fractures. A total of 179 (5.5%) fractures were located at the upper extremity (hand 23%, wrist 21%, forearm 23%, elbow 10%, humerus shaft 11%, shoulder 11%). Men were affected twice as often as women (m=120, w=59), although 41% of the injured were female drivers. Only 10 (5.6%) of the injured were airbag protected, which was released in 4 cases at the crash. Due to the low proportion of airbag-protected injured, no comparison with the entire collective was performed. AIS 2 injuries appeared in 67% of all cases, AIS 1 in 17% and AIS 3 in 16%. The AO/OTA fracture pattern was Type A in 47%, Type B in 27% and Type C in 26%. The classification based upon Tscherne showed minor injury to soft-tissue in closed fractures, meaning Type Fr. C I, in 50% of the cases. The arm fractures were mainly caused by frontal collisions (n = 92, 52%) or multiple collisions (n = 60, 34%). In 63% of the cases the impulse angles ranged in the groups 30°, 0° or 330°. This corresponds to an impact vector that affected the vehicle from the front to the rear. In 74% of the crashes delta-v exceeded 30 km/h. A lower delta-v resulted mainly in fractures affecting shoulder and wrist.

Discussion/Conclusion: Since over half of all arm fractures resulted from a direct impact to the hand and/or arm, modifications are necessary in order to improve the energy absorption of the dashboard and the inner door. The force of lateral deformation on the door is also a major factor in the cause of injury. Side- and front- airbags could contribute to lowering the risk of fractures involving the upper extremities. Due to low case number of airbag-protected injured with fractures of the upper extremity, the preventive effect of airbags for the upper extremity is not evident, so far. Future investigations should reveal what additional stress airbag deployment induces.