A computer-controlled electromechanical hammer to quantify tendon reflex

Spasticity is very common in spinal cord injured individuals. It causes disability and can be quite painful. Many of the prevailing drug treatments have significant adverse side effects and it is thus necessary to establish a method to quantify spasticity so that appropriate drug dose can be prescribed. In addition, a reliable and sensitive method will help evaluate various modes of treatment and analyze characteristics of spasticity. An electromechanical hammer was designed to provide more accurate evaluation of tendon reflex. The electromechanical hammer is powered by a linear actuator which produces a quick tap on muscle tendons to evoke stretch reflex at the knee or other joints. The performance of the linear actuator is regulated by a PID controller implemented in an IBM PC. To evaluate the device, a number of experiments have been done on both normal and spastic subjects. The computer-controlled linear actuator can apply precisely-controlled, more repeatable tapping onto muscle tendons, which provides us a reliable tool to quantify tendon reflex and spasticity. The tendon hammer can be used to quantify differences in limbs with various degrees of spasticity, ranging from non-spastic to severely spastic. It can also be used to evaluate the effects of anti-spasticity drug and rehabilitation progress