A force plate measurement system to assess hindlimb weight support of spinal cord injured rats

This paper describes a force plate system for quantitative measurement of the hindlimb weight support of rats. The system is built around a microcontroller and uses strain gauges to measure individually the weight applied by each limb and also the general hindquarters of the rat. The sum of weights on the individual force plates adds up to the total weight of the rat. Mathematical comparison of the weights of the different force plates allows calculation of the weight percentage of the hindquarters (W%HQ=(hindquarters weight/total weight)x100%). When hindlimb impairment is high, the W%HQ is high and vise versa, allowing hindlimb weight support to be evaluated by the W%HQ. An actual laboratory embodiment is demonstrated and real experiments are performed on spinal cord damaged rats. W%HQ results are compared with Basso, Beattie, Bresnahan (BBB) locomotor behavioural test results on the same rats at approximately the same time. When a rat is placed in the correct position of the test chamber, the user can use a local keypad/LCD display (standalone mode) or the PC keyboard/display to control the system and access the current data. Comparing our results with those of the BBB method confirms the proposed hardware and W%HQ metric represent very well the recovery of a rat after spinal cord injury. Medical investigators report that under actual use, the presented system is stable, accurate and easy to use. Additional advantages of the presented force plate system include stand-alone capability, non-dependence on subjective human judgement and quantitative results.