Females have a greater prevalence of neck injuries than males in motor vehicle rear impacts, and have more flexible necks and osteoligamentous cervical spinal columns. In addition, gender-specific static or dynamic computational models do not exist. However, varying sized physical models (dummies) have been designed to account for gender/size differences for crashworthiness studies.

The effect of gender bias on three-dimensional cervical vertebral geometry was investigated using computed tomography images of 109 normal adult healthy volunteers. Groups were separately size-matched for stature, sitting height, and head circumference. Analysis of variance techniques were used to identify gender effects. Vertebral level was also investigated. Support areas at each level were evaluated for gender bias using simple and multiple regression analyses that included variables such as body mass, stature, sitting height, and head and neck circumferences. Briefly, significantly (p<0.05) smaller vertebral geometry in females may account for the increased kinematics of the cervical column. These results underscore the need to differentiate mathematical models based on gender to predict accurate biomechanical responses under physiologic and traumatic loadings.

Responses of the 5th percentile female and 50th and 95th percentile male dummies were investigated in rear impact acceleration loading using sled tests. The effects of head restraint height and backset on each dummy response were analyzed using overall kinematics and parameters such as head and T1 accelerations, forces and moments at the head-neck junction, head-neck rotations, and various neck injury criteria. Briefly, peak accelerations and forces and moments did not follow the expected trend, that is, increasing dummy size increases the metric. The 50 th percentile male dummy responded with expected increases in injury criteria for all backsets and head restraint heights. A similar trend was not true for the 5th percentile female and 95th percentile male dummies. Peak head rotations were higher with the greatest backset for both head restraint heights. Peak head rotations increased with increasing backset and head restraint height, and this phenomenon was true for all dummies. This simple metric may be an efficacious parameter for use in rear impact crashworthiness.

The effect of gender bias in cervical vertebral geometry and non uniform responses among the three sizes of dummies emphasize the need to include gender and size variables in computational and physical models for rear impact injury assessments.