Field Data Study of the Effect of Knee Airbags on Lower Extremity Injury in Frontal Crashes 2021-01-0913

Knee airbags (KABs) are one countermeasure in newer vehicles that could influence lower extremity (LEX) injury, the most frequently injured body region in frontal crashes. To determine the effect of KABs on LEX injury for drivers in frontal crashes, the analysis examined moderate or greater LEX injury (AIS 2+) in two datasets. Logistic regression considered six main effect factors (KAB deployment, BMI, age, sex, belt status, driver compartment intrusion). Eighty-five cases with KAB deployment from the Crash Injury Research and Engineering Network (CIREN) database were supplemented with 8 cases from the International Center for Automotive Medicine (ICAM) database and compared to 289 CIREN non-KAB cases. All cases evaluated drivers in frontal impacts (11 to 1 o’clock Principal Direction of Force) with known belt use in 2004 and newer model year vehicles. Results of the CIREN/ICAM dataset were compared to analysis of a similar dataset from NASS-CDS (5441 total cases, 418 KAB-deployed). KABs were associated with a reduced rate of LEX injury in the CIREN/ICAM dataset (OR = 0.612, p=0.065), but were inconclusive in the NASS-CDS dataset (OR=0.946, p=0.761). KABs were associated with a reduced rate of knee/thigh/hip injury in CIREN/ICAM (OR = 0.555, p = 0.035) but had no measurable effect on below knee injury in CIREN/ICAM (OR = 0.928, p = 0.765) or NASS-CDS (OR=1.102, p=0.641). In conclusion, KABs were associated with reduced rates of LEX and knee/thigh/hip injury in the CIREN/ICAM dataset and had no measurable effect on below knee injury for drivers in frontal crashes in either dataset.