A multi-body dynamics study on a weight-drop test of rat brain injury

Abstract

Traumatic brain injury (TBI), induced by impact of an object with the head, is a major health problem worldwide. Rats are a well-established animal analogue for study of TBI and the weight-drop impact-acceleration (WDIA) method is a well-established model in rats for creating diffuse TBI, the most common form of TBI seen in humans. However, little is known of the biomechanics of the WDIA method and, to address this, we have developed a four-degrees-of-freedom multi-body mass-spring-damper model for the WDIA test in rats. An analytical expression of the maximum skull acceleration, one of the important head injury predictor, was derived and it shows that the maximum skull acceleration is proportional to the impact velocity but independent of the impactor mass. Furthermore, a dimensional analysis disclosed that the maximum force on the brain and maximum relative displacement between brain and skull are also linearly proportional to impact velocity. Additionally, the effects of the impactor mass were examined through a parametric study from the developed multi-body dynamics model. It was found that increasing impactor mass increased these two brain injury predictors.

Keywords:

• Traumatic brain injury
• rat brain injury model
• multi-body dynamics

Notes

1. The peak acceleration data reported in papers Li et al. (2011a) and (2011b) are slightly different. Referring to Li et al. (2011b), the ratio of the mean peak accelerations would be 0.734.

2. Instead of using the drop height, the measured initial velocity of 6.14 m/s (Li et al. (2011a)) and the second equation in Equation (3(3) ) for the skull were used in the estimation. The velocity loss was due to the dragging of the accelerometer cable and friction between the impactor and the tube as explained in Li et al. (2011a). Without such a loss, the second equation in Equations (3(3) ) and (4(4) ) would be identical.