Experimental

Contribution of Bone Tissue Properties to Strength of the Ageing Human Hip

SNF grant # 200365 with PSI and EMPA.
This study examines local variations in bone tissue quality at the proximal femur in relation to age. Ninety-four femurs were scanned with micro-CT, giving access to morphology and mineral content. After sample preparation, structure-property relationships were explored through histological staining and tensile tests on native and demineralized samples (Fig. 2). Age-related changes were observed in structural components such as increasing cement line density, while the organic fraction and mechanical properties remained age-independent. Synchrotron experiments with PSI explore bone ultrastructure and mechanical properties at the femoral neck. This project also improves a finite element model to simulate the hip’s mechanical behaviour from physiological loading up to a fall impact.

Femoral sample overview (a) with mounted sample for tensile tests (b) and image with automatic segmentation of bone micro-structural components (c).

Biomechanical Stability of Dental Implants and Bone Screws

with AO.
Immediate post-surgery loading is of high interest in dental implantology and orthopaedics. The MSB laboratory offers computational models validated by experiments to assess the primary stability of dental or orthopaedic implants in human bone tissue. Based on high-resolution μCT scans of specific anatomical sites, these models provide deep insights into implant behaviour according to their geometry, material and insertion protocols under various loads. Those models are typically used to develop new prototypes.

Role of Hip Soft Tissues in Fracture Risk

with MUG.
Trochanteric soft tissues attenuate the impact force on the femur following a sideways fall. A deeper understanding of the mechanical behaviour of these tissues during an impact and the use of appropriate measurement tools may improve hip fracture risk prediction. We examined the mechanical response of excised human trochanteric soft tissues at low force using a handheld device and at high impact force using a mechanical testing system. Finite element models of these structural experiments were created to identify material constants of these soft tissues.

Left: mechanical testing of a trochanteric soft tissue sample. Right: comparison of laboratory and clinical stiffness measurement modalities.

Biomechanical Testing

Mechanical testing was used in several research projects and Master’s thesis e.g., validating a preoperative marker for safe screw placement in bone conduction hearing implants, revealing correlations between the marker and mechanical properties. Areal bone mineral density (aBMD) and trabecular bone score (TBS) were measured in lumbar vertebrae compressed uni-axially to decipher the potential role of vertebral fractures in these standard clinical measures. Tissue properties of the human distal tibia were evaluated by nano-indentation to characterise different microstructural compartments for improved finite element analysis. In a computational study, intramedullary geometry of the human proximal femur was classified using a statistical shape modelling approach to help improve custom total hip arthroplasty.