Image-Based Optimization of Articular Cartilage Material Properties for the Entire Joint Structure in Porcine Hips

Articular cartilage has been considered unsuitable as a load-bearing structure with the properties measured by the conventional compression test. To measure the material properties of cartilage as a load-bearing structure, four porcine hip joints were used, and a compressive load of 650 N was applied in a standing position. Cartilage deformation over time was observed by performing CT scans five times at 3-min intervals while the load was applied. In order to secure the cartilage properties of the samples used in the test, a conventional compression test was performed using a cartilage plug taken from each sample. A 3D femoro-acetabular joint finite element model was created from the CT images to simulate the hip joint compression test and compared with experiments results. Then, the deformation of the cartilage obtained from the CT image was optimized as an objective function, and the measured cartilage properties obtained from the conventional compression test were compared with the optimized properties. The femoro-acetabular joint simulation to which the measured properties were applied failed to converge. Young's modulus and Poisson's ratio of cartilages optimized through optimization were approximately 19.6 and 1.7 times greater than the measured values, respectively. However, permeable parameters did not show significant differences between the optimized and measured values. Our results show this optimization method offers the potential to overcome the challenges associated with acquiring accurate boundary conditions for articular cartilage, ultimately facilitating the generation of realistic deformation patterns in in-vivo situations.