~~"ZOOM" SEMINAR
SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Wednesday, December 16, 2020 at 14:00

The mechanical response of human humeri

Gal Dahan
Ph.D. student under the supervision of Prof. Zohar Yosibash

Proximal humerus fractures are the 3rd most common fracture in osteoporotic patients. Since osteoporosis is a systemic disease, often clinicians are faced with the question on the risk of fracture of a specific patient and the need for drug prescription. Finite element models based on quantitative computed tomography (QCT-based FE) can serve as a biomechanical-based quantitative tool that can assist in clinical decision-making process. In particular,  the individual intact bone strength or stability assessment of the fractured bone if fracture occurred (should be quantified  to decide whether a surgery is required, or a conservative treatment is sufficient). QCT-based FEs have been shown to provide accurate predictions for femurs and this study is aimed to extend the current capabilities to the humeri.
In the current study we present the enhancement and validation of QCT-based FE models by experiments conducted on fresh frozen humeri. Validation was performed by means of strain gauges (SGs) strain measurements and enhanced using digital image correlation (DIC) enabling full field displacement and strain evaluation.
Following experiments in the elastic regime, the humeri were loaded to obtain a fracture in their proximal part. Two different physiological fractures were realized in the experiments, in both anatomical and surgical neck of the bones. Fracture criteria based on maximum principal strains computed by the QCT-based FE models were checked experimentally both in terms of the load to fracture and the fracture locations. This research opens the door to the novel use of FE analysis in clinical practice in endocrinology and orthopedic treatment of the humeri. 

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https://zoom.us/j/96584758181?pwd=WC9PMXdsYzJ3NFdEN2Q5ZUtOZEVjdz09 The meeting will be recorded and made available on the School’s site.

"ZOOM" SEMINAR

SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Monday, November 30, 2020 at 14:00

Implants in the human proximal femur:

A combined experimental-computational study

Yekutiel Katz

Ph.D. student under the supervision of Prof. Zohar Yosibash

Hip replacement is a common orthopedic surgical procedure. Long-term survival of hip implants is of increasing relevance due to rising life expectancy. The biomechanical effect of strain shielding as a result of implant's presence may lead to bone resorption, thus increasing the risk for implant loosening and periprosthetic hip fractures. Studies on patient-specific finite element (FE) models based on quantitative computed tomography (QCT) showed that the mechanical response of intact femurs can be well predicted. The current study improves these methods and extends their application to femurs inserted with hip implants, focusing mainly on cemented implants.

To enable the use of FE in clinical practice for: femoral fracture risk assessment, pre-operative optimal implant selection and periprosthetic fracture risk prediction, QCT based FEAs must be proven reliable trough a thorough ex-vivo experimental procedure. A combined experimental-computational study on fresh frozen human femurs, in both intact and implanted states with different implants is presented, aiming at validating patient specific QCT based FE models.

The current study incorporates digital image correlation (DIC) full field measurements on human tissues with curved surfaces leading to new insights on the biomechanics of  the femoral neck. This area’s response was misrepresented in previous studies.

The validated FE models were used to develop a systematic algorithm for strain shielding quantification. Different strain measures were examined suggesting the volumetric strain to be the most appropriate for strain shielding quantification, that may assist surgeons to choose the optimal patient specific implant.

Join Zoom Meeting
 

https://zoom.us/j/96584758181?pwd=WC9PMXdsYzJ3NFdEN2Q5ZUtOZEVjdz09 The meeting will be recorded and made available on the School’s site.