2018 Volume 24 Pages 149-157
Proximal femur fractures due to osteoporosis are one of the serious health issues in aging societies. Osteosynthesis employing pin-or screw-type implants is widely used for femoral neck fracture treatment in Japan. Unfortunately, complications such as secondary fractures may occur during the postoperative rehabilitation period. In order to reveal the potential cause of the postoperative fracture from the viewpoint of biomechanics, this study explores and proposes a novel dynamic stress analysis of the treated proximal femur based on finite element (FE) analysis via ABAQUS. A new subject-specific 3D left hip joint FE model was constructed from the CT images of an elderly female volunteer. The model consists of the pelvis, proximal femur, cartilage, and Dual SC Screw (DSCS). Dynamic loading and boundary conditions were applied to the model for simulating gait motion. The time-dependent loading forces acting around the hip joint were obtained by the inverse dynamic analysis of human gait using an in-house lower-limb musculoskeletal model. These loading and boundary conditions for simulating the gait motion are the major technical advantages of the proposed dynamic FE analysis over the conventional static FE analysis. The simulation results successfully demonstrated the detailed time-dependent stress distribution and excessive local stress concentration for the DSCS treatment ; the excessive local stress concentration is the potential cause of subtrochanteric fractures during the postoperative rehabilitation period. The proposed dynamic FE analysis has proved effective in assessing the postoperative fracture risk of osteosynthesis with implants.
