Prognostic significance of lower extremity long bone fractures after automobile versus pedestrian injuries.

Background: Fractures of the tibia and femur are common after automobile versus pedestrian (AVP) injuries. This study evaluates the effect of age on the type of fracture and the incidence and type of associated injuries.

Methods: All patients involved in an AVP crash from January 1, 1995, through June 30, 2006, were included in the study. Variables obtained from our trauma registry included age, gender, Injury Severity Score, Abbreviated Injury Scale, intra-abdominal and spine injuries, and mortality. Patients were divided into three age groups for analysis: younger than 15 years, 15 years to 55 years, and older than 55 years. The incidence and type of associated injuries were assessed according to the presence or absence of fractures of the tibia only, femur only, or combined femur and tibia fractures.

Results: A total of 6,652 patients had AVP crashes and 1,936 (29%) had tibia or femur fractures (tibia, 20%; femur, 7%; tibia/femur, 3%). The incidence of tibia fractures increased with age ranging from 13% in those younger than 15 years to 25% in those older than 55 (p < 0.001). Combined tibia and femur fractures were also more common in adults and isolated femur fractures were more common in children. Hollow viscus injury was 1.8% in those with lower extremity fractures and 0.9% in those without (p = 0.0013). Mortality was 10% in those with fractures and 6% in those without (p < 0.0001) and was 20% in those with tibia and femur fractures.

Conclusions: Age affects the incidence and type of lower extremity fractures after AVP injuries. The presence of lower extremity fracture is associated with a higher incidence of chest, spine, and intra-abdominal injuries. It is advisable that all patients with lower extremity fractures after AVP injuries be evaluated by a surgeon familiar with these injury patterns.