A research project at the Technische Hochschule Mittelhessen is about “determining the loosening of hip endoprostheses using sound emission”. The state of Hesse is supporting the project with 35,000 euros. The project manager is Dr. Jörg Subke, Professor of Biomechanics at the Gießen Department of Life Science Engineering. Cooperation partners are Prof. Dr. Burkhard Ziegler from the Mechanical and Energy Engineering Department at THM , the University Hospital in Gießen and the company BoneDias in Greifenstein.

More than 200,000 people in Germany receive a hip prosthesis every year. An increasing number of younger patients have joint degeneration that requires an operation. About every tenth operation is a replacement operation, which is necessary in most cases because the prosthesis has become loose. For orthopedic reasons, it is only possible to insert a hip prosthesis twice. It is therefore important to delay the exchange as long as possible in order to prevent an imminent loss of mobility.

A prerequisite for determining the right time is an accurate diagnosis of how far the loosening has progressed. The researchers want to use acoustic emission analysis for this. This process takes advantage of the fact that mechanical stress causes changes in the structure of a material, which lead to the emission of noise. “The potential of acoustic emission analysis has already been shown in the analysis of the cartilage layers in the knee joint and the determination of the crack formation limit in the human femur. We expect that we will also get the same results when analyzing the loosening of the hip prosthesis in the thigh," says Subke.

In order to establish the procedure, fundamental investigations are necessary. First of all, the types of stress that led to the fracture should be determined for different types of fractures between the bone and the prosthesis. In-vitro samples from femurs and endoprostheses are broken up in a specially designed testing device. The acoustic emission signals obtained in this way are the basis for further developing the procedure with examinations on patients.

The research project has a duration of twelve months. It is supported as part of the "Research for Practice" funding programme. With this, the state government subsidizes practical projects at Hessian universities for applied sciences.