Investigation of the safety effects of knee bolster air bag deployment in similar real-world crash comparisons.
OBJECTIVE
The lower extremity is the most frequently injured body region and knee-thigh-hip (KTH) injuries account for half of these injuries. Knee bolster air bags (KBABs) have been incorporated in some vehicles to serve as an additional restraint for the occupant's knees and reduce KTH injuries. To investigate the safety benefits of KBABs, similar frontal crashes with opposing KBAB deployment were selected from the Crash Injury Research and Engineering Network (CIREN) database.


METHODS
An 8-point similarity scoring algorithm was used to quantify crash and occupant similarity and select case comparisons. A total of 183 cases without a KBAB were scored for similarity to 9 KBAB cases. These similarity scores were used to select 31 final case comparisons. The effect of KBAB deployment on occupant injury patterns was investigated with a particular focus on KTH injuries.


RESULTS
Over half of the occupants exposed to a KBAB sustained no KTH injuries and a reduction in femur fractures was observed in KBAB occupants (P = .036). However, increases in proximal tibia/fibula and foot/ankle fractures were observed in KBAB occupants (P = .022 and .002, respectively). Mildly significant decreases in pelvic fractures and Abbreviated Injury Scale (AIS) 2+ head injuries were observed in the KBAB occupants, supporting the notion that KBABs reduce forward occupant excursion (P = .094 and .055, respectively). Investigation of each case comparison yielded further insight into the reasons for injury pattern differences between cases with opposing KBAB deployment. In addition to KBAB deployment status, differences in occupant factors (age, height, and weight) and crash factors (delta V and belt use) between the cases for a particular comparison could explain variation in injury patterns.


CONCLUSIONS
The current study presents a preliminary in-depth qualitative and quantitative assessment of KBAB safety benefits. However, further investigation is recommended to provide conclusive evidence of KBAB effectiveness.
Virginia Tech-Wake Forest University Center for Injury Biomechanics, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
Ashley A
AA
Weaver
Kathryn L
KL
Loftis
Joel D
JD
Stitzel
D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D017278:Air Bags; D000465:Algorithms; D016208:Databases, Factual; D025981:Hip Injuries / Q000517:prevention & control; D006801:Humans; D007718:Knee Injuries / Q000517:prevention & control; D010388:Pelvis / Q000293:injuries; D036301:Qualitative Research; D012449:Safety; D013848:Thigh / Q000293:injuries; D014947:Wounds and Injuries / Q000517:prevention & control*