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Item type:Publication, Access status: with files , Dynamik der Hüftschaftimplantation(2026); In cementless hip arthroplasty, mallet blows are used to advance the rasp during the preparation of the femoral canal, to implant the prosthesis, and to join the implant components. The strength of the mallet blows is crucial for a stable press fit, while the dynamics of the involved instruments and the interaction with the femur-tissue system are complex and individual. Therefore, the aim of this study is to investigate the influence of patient- and surgical approach-specific characteristics on the dynamic behavior of the femur-tissue system as well as the force transmission of surgical instruments. The experimentally determined parameters of the femur-tissue system of the human bodies examined varied depending on the positioning on the operating table, which in turn depended on the surgical approach. However, for both surgical approaches examined, the values resulted in a relatively low natural frequency (lateral: 6.7 Hz, direct anterior: 9.6 Hz). Consequently, metal-on-metal mallet blows or comparable short impulses from automated surgical impaction tools lead to overcritical excitation. As a result, the implant is inserted into the femur before the bone itself even starts moving. The experimental and numerical analyses revealed a significant attenuation of the mallet force by the impactor. The design of the impactor had a significant influence on the force transmission: lighter impactors transmitted higher peak forces than heavier variants. Even minor design modifications resulted in differences in the transmitted force by a factor of two. Due to the overcritical excitation, it is not necessary to make intraoperative adjustments of the surgical technique to the patient's positioning or to the mass and stiffness of the surrounding soft tissue. However, the utilization of different impactors can lead to considerable deviations in force transmission. Without adequate briefing for orthopedic surgeons, changing the implant system, the associated instruments, or the surgical approach can increase the risk of complications such as periprosthetic fractures or aseptic loosening.Publicationtype: Doctoral Thesis49 36 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Die Rolle von Knochenpartikeln für die Verankerung zementfreier EndoprothesenPublicationtype: Doctoral Thesis33 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Patientenorientierte Implantatwahl in der RevisionsknieendoprothetikPublicationtype: Doctoral Thesis168 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 40 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Implantation zementfreier Hüftpfannen(2023); The most common reason for revision of a cementless hip arthroplasty in Germany is implant loosening, especially on the acteabular side. The primary stability of the press-fit cup is achieved by a force locking mechanism between the implant and the bone. For this purpose, the cavity is underreamed in relation to the cup diameter and the pressfit is gradually increased by manual implantation with mallet blows. Thus, primary stability is multifactorially influenced by the implant, the patients bone and the surgeon. Therefore, the implantation process is of great importance to achieve a sufficiently high primary stability. The aim of the study was to develop clinical recommendations for the successful implantation of cementless acetabular cups. Special attention was given to the influence of the viscoelastic behavior of bone. Within the first 600 s, the cups showed a reduction in deformation in the range of 10 – 30 % of the initial deformation achieved after implantation. In-silico, thin-walled, less rigid cup designs benefited from low relaxations, resulting in high primary stability relative to the implantation force. In-vitro, the thin-walled cup design showed the highest primary stability. The low implantation forces promoted fast and complete seating of the cup. In addition to cups with constant thin wall thickness, cups with wall thickness reduced at the pole and anatomically shaped cups can be recommended based on the numerical model. When reducing acetabular stiffness, a compromise with the allowable deformation must be made. In addition, care must be taken to use a bone-preserving technique during surgical implantation. To minimize bone damage, unnecessary blows are to be avoided. Here the surgeon can also benefit from the improved haptic and visual feedback of thin-walled designs. Automated impactor systems also offer the possibility of constant and objective energy input as well as high-frequency implantation. The latter showed an altered viscoelastic behavior of the bone between the blows compared to manually applicable frequencies and required significantly less implantation force with higher primary stability.Publicationtype: Doctoral Thesis76 41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Sicherheit bei der Implantation keramischer EndoprothesenkomponentenPublicationtype: Doctoral Thesis48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Towards automated age estimation of young individuals : a new computer-based approach using 3D knee MRIThe purpose of this work is to investigate the age estimation of living individuals on the basis of MRI sequences of the knee. Using a large data collective of young male subjects, a new AI-based approach is developed to automatically detect bone structures in the image and to learn the chronological age based on this information. With a mean absolute error (MAE) of 0.69 ± 0.47 years for the prediction of the age and an accuracy of 90.9% for the majority classification on the 18-year-limit, the results demonstrate the potential of this approach.Publicationtype: Doctoral Thesis333 1014 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Machine learning in cardiac CT image reconstructionThis dissertation focuses on the removal of cardiac CT imaging artifacts caused by motion and metal implants. A combination of model-based data synthesis and subsequent data-driven learning of image enhancement methods is proposed. Forward models for virtual artifact generation are developed by incorporating prior knowledge about the cardiac anatomy and CT imaging physics. They form the counterpart of resulting learning-based backward models, which achieve significant reduction of artifacts during testing on real data.Publicationtype: Doctoral Thesis469 678 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 93