ABSTRACT
Objective To investigate the effect of hip protector on biomechanical response of the human pelvis-femur complex under lateral pelvic impacts during sideways falls using three dimensional (3D) finite element (FE) method. Methods Based on the model database of China Mechanical Virtual Human, a 3D FE model of the pelvis-femur-soft tissue complex including cortical bone, cancellous bone and soft tissue capsule and the pelvis-femur-soft tissue complex with a two layer hip protector were created, respectively. The rigid plane model was also constructed in the two models for ground simulation and constrained in all freedoms. The average hip lateral impact velocity of 2 m/s was applied to the two models, and the time for simulation analysis was set at 20 ms. The stress and strain distribution on the two models under lateral impacts could be obtained by the 3D FE calculation. The comparative analysis was performed to study the effect of the hip protector on biomechanical response of the pelvis-femur complex. Results The hip protector made the peak Von Mises stress appeared 4 ms more earlier in the pelvis-femur complex with a significant decrease in the stress and strain level. The average Von Mises stress peak was decreased by 67.88% and 69.34% in the cortical bone and in the cancellous bone, respectively, and the compressive principal strain peak was decreased by 63%. Conclusions Under lateral pelvic impacts, the two-layer hip protector could act as safeguard for pelvis-femur complex, thus effectively prevent the occurrence or reduce the risk of bone fracture.
ABSTRACT
Objective To investigate the biomechanical characteristics of the human pelvis-femur complex under lateral pelvic impacts during sideways falls using three dimensional (3D) finite element (FE) method. Methods Based on the model database of China Mechanical Virtual Human, a 3D FE model of the pelvis femur soft tissue complex was created, including cortical bone, cancellous bone and soft tissue capsule. A rigid plane model was also constructed for ground simulation and constrained in all freedoms. The average hip lateral impact velocity of 2 m/s was applied to the model and the time for simulation analysis was set at 20 ms. The stress and strain distribution on the pelvis-femur complex were obtained by the 3D FE calculation and analysis. ResultsOn the contact surface, the peak impact load reached to 7 656 N at 13 ms, while the maximum Von Mises stress on the soft tissue was 2.64 MPa. Simultaneously, the peak Von Mises stress of 142.64 MPa on the cortical bone occurred in the region of pubic symphysis, which was approximate to the yield stress on the cancellous bone. The Von Mises stress level was higher in the region of the femur neck and greater trochanter. At 13 ms, the peak Von Mises stress on the cortical bone of the femur neck was 76.49 MPa and that on the cancellous bone was 8.44 MPa with the peak compressive principal strain being 0.94%. The peak Von Mises stress on the cancellous bone of greater trochanter was 8.50 MPa, while the peak compressive principal strain was 0.93%. Conclusions Bone fractures of the pelvis-femur complex tend to occur in the region of the femur neck, greater trochanter and pubic symphysis under deceleration impacts during sideways falls.