Relationship with sex-based anatomical differences to lower extremity injury severity in frontal crashes

Multiple studies have demonstrated an increased risk of lower extremity injuries for females in frontal crashes. This study aimed to investigate whether sex-based anatomical differences, as measured on computed tomography (CT) scans of the abdomen and pelvis, contribute to lower extremity injury risk. The Crash Injury Research and Engineering Network (CIREN) database (2017–2023) was queried for frontal collisions. Cases were included if the occupant was an adult (≥18 years), seated in the front row, properly restrained, and had an analyzable CT scan of the abdomen and pelvis. Anatomical measurements included soft tissue over the anterior superior iliac spine (ASIS) along three vectors, thigh diameter, thigh anterior soft tissue, subcutaneous adipose tissue (SAT) area, psoas area, lumbar spine bone mineral density (BMD), femur cortical thickness, height, weight, and body mass index (BMI). Ordinal regression analysis was employed to examine the individual associations between these measurements and the highest Abbreviated Injury Scale (AIS) injury severity of the lower extremities, after adjusting for age, change in velocity (delta-V), knee bolster intrusion, toe pan intrusion, seat track position, airbag deployment, and sex. The same analysis was repeated for the highest AIS injury severity in the hip-thigh-knee and the lower leg regions. A total of 195 occupants were included, of which 114 (58%) were female. Among the anatomical measurements from the computed tomography (CT) scans, significant differences between the sexes were observed only in the SAT and psoas areas, with the SAT area being higher in females and the psoas area being higher in males. Ordinal regression analysis revealed that SAT area, weight, and BMI were significantly associated with the severity of lower extremity injuries. These three variables were also significantly associated with hip-thigh-knee injuries but not with injuries to the lower leg. Further analysis indicated that SAT area is a significant mediator of the effect of sex on lower extremity injury severity. The area of subcutaneous tissue at the level of the ASIS was significantly associated with increased severity of lower extremity injuries, especially in the hip-thigh-knee region. This measurement was higher in females and may account for some of the observed differences in injury risk between sexes.