Development of techniques for measuring the mobility of knee joints in children with Cerebral Palsy

Abstract: Cerebral Palsy, commonly referred to as CP, is a neurological disorder that results in loss or impairment of motor function, which affects body movement, muscle control, muscle coordination and balance. In Sweden, about 200 children are diagnosed with Cerebral Palsy every year and the disorder can cause imbalances between the muscles. These imbalances can lead to contractures which is equiva- lent to permanent shortening of muscles and stiffness of joints. This can severely affect the mobility of the child and the quality of life. Today, the only way for physicians or physiotherapists to evaluate the movement of the joints, is during a patient’s short visits to the hospital. The purpose of this project was to develop a device that was able to measure the range of motion of the knee during a longer period of time, which could help customize the child’s rehabilitation. The initial approach was to implement two inertial measurement units (IMUs) and find the angle between the sensors. Different solutions on finding the angle was tested without being able to obtain stable data and the project members chose a new approach. Instead of IMUs, a potentiometer was used and stable data was obtained. A prototype was developed in an iterative and incremental product development process and data was collected during different types of physical exercise. The final prototype was wireless, able to collect data during ordinary life activities and had a battery life of over 30 hours. The data was analyzed and the results were accurate but showed that the prototype probably hindered some of the natural movement of the knee. The developed prototype is a step towards being able to measure the knee range of motion during a longer period of time, and could be a tool for physicians and other medical staff when evaluating and rehabilitating children with CP.