Statistical Finite Element Analysis of the Mechanical Response of the Intact Human Femur Using a Wide Range of Individual Anatomies

This paper attempts to obtain an improved and more physiological distribution of the applied joint and muscle forces on the intact human femur and to gain an understanding of inter-subject variability on the mechanical response. A set of 109 CT-based femur models of individual anatomies were simulated using the Finite Element method during walking. Heterogeneous material properties, physiological boundary and loading conditions were applied to each femur model to form a reference initial load configuration [1]. To correct the imbalance in the force system, an optimisation scheme was adopted that iteratively updated the locations of both muscle and joint attachments across a 5-mm radius circle centred at the initially defined node in the reference load configuration [2, 3]. Across all patients, a 28–48% reduction in the resultant reaction force magnitude measured at the femoral head was achieved. A clear gender bias was present in terms of reaction forces and strains in both the initial and optimised models. The optimisation scheme mostly affected the medial-lateral component of the reaction force. The change in the average strain was found to be highly dependent upon the percentage reduction achieved in the optimisation process. This reduction was higher for males than females and is most likely due to size differences. Body weight and bone density highly influenced reaction forces and strains. Femoral anteversion linarly increased with reaction forces; ther anatomical parameters such as neck length, neck offset, and functional femoral length or CCD angle did not have a clear influence on these forces.

Keywords: Inter-subject variability Anatomy Femur Walking Finite Element Reaction force Strain Optimisation Statistical analysis