A General Kinematic Brain Injury Criterion Combining Translational and Rotational Effects

The human brain typically experiences both translational and rotational motions during impact. Existing kinematic brain injury criteria often consider only one of these effects, or lack a reasonable combination of both, which may lead to significant misjudgments. This study proposes a general injury criterion (GIC) that uses the widely accepted injury criterion of maximum principal strain (MPS) as an intermediary variable and comprehensively accounts for both translational and rotational effects.

A total of 178 head impact cases were established, considering different impact types, locations, directions, and velocities. Corresponding finite element models were constructed based on the THUMS model. The translational and rotational effects were quantitatively analyzed. Using MPS as an intermediate variable, the GIC was carefully developed and compared with existing injury criteria. On this basis, an application demonstration was performed by combining simulation results with clinical outcomes from existing literature.

The quantitative analysis results of translational and rotational effects show that their contributions to the MPS are often comparable, and their effects on brain injury need to be considered simultaneously. GIC, combining the translational and rotational effects, has the highest linear correlation with MPS. It shows a 17% higher linear correlation than the second-best criterion. In addition, for 24 clinically diagnosed TBI cases, the classification accuracy of GIC reaches 58 and 92% when the MPS injury thresholds are set at 0.2 and 0.35, respectively.

The proposed GIC achieves the highest goodness of fit with MPS among the kinematic criteria evaluated in this study and demonstrates the feasibility of predicting traumatic brain injury with case studies of impacts. It provides a practical tool for rapid kinematics-based brain injury assessment in bioengineering and safety engineering.