NILAX Sensor system for the determination of knee laxities

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The aim of this project is the development and testing of a universal, easy-to-use diagnostic system, based on highly elastic strain gauges, for the objective assessment of cruciate ligament injuries and their healing process. The project result is a sensor system which can be worn on the patient in the form of a stretchable sock, which allows dynamic measurements. The device is intended to support the decision process for an operation or therapy of the knee in everyday clinical practice. The simple applicability also makes measurements in the patient's home environment possible for the control of the treatment outcome. This project builds upon the experiences of a prior DFG pre-study into the development of a highly elastic polymer strain gauge. In that study, a process was established for the construction of strain gauges and read-out electronics for use in obtaining measurements from a simulated knee. This lays the groundwork for future clinical studies. The first phase of the project is to adapt the existing sensor system for a clinical study on cruciate ligament. The development of the system is carried out based on the preliminary work, including the results of measurements on probands and patients, and taking into account the characteristics of the sensor system already developed. The final sensor design is optimized at the already established in vitro test stand. Initially, static comparative measurements are performed with simple measuring strips with the help of probands. These results were used for optimization of the sensor system. The first functional patterns of the sensor system are used to carry out further tests in healthy probands. In the second project phase, a clinical study will be carried out with the optimized sensor system. The ap-laxity is measured in combination with the rotational laxity (rotational slide) of the knee joint under physiologically dynamic conditions in real time. In addition, work is being carried out to increase the specificity and sensitivity of the measuring system and to automate sensor production. The system holds an advantage over conventional methods in that the three components of knee laxity (anterior-posterior, lateral-medial, rotation and slipping) can be simultaneously monitored, whereas the conventional methods can only individually determine one at a time. Additionally, the orthosis enables monitoring during normal motion. The project will be carried out in close cooperation between the Department of Microsystems Engineering (IMTEK) and the Department for Orthopedics and Traumatic Injuries at the University Medical Center Freiburg.