Experimental and finite element study on the stress of thoracolumbar spine during backward fall

English Keywords:Fall backward  Finite element analysis  Thoracolumbar injury

English Abstract:

  【Abstract】 Objectives: To evaluate the local stress of thoracolumbar vertebra after falling by constructing real backward falling down model based on the finite element loading condition obtained from volunteers. Methods: A healthy volunteer (male, 27 years old, 175cm, and 70kg) was selected, and the torso of the volunteer was scanned by CT. Then the skeletal muscle model was established using the dynamic simulation software Anybody Modeling System. The volunteers stood at a backward tilt of 30° and fell backward to construct a human skeletal muscle model in the state of fall. The finite element model was established and optimized based on the CT data of the volunteer. Applied 7.5N·m moment to simulate the range of flexion, extension, left and right lateral bending and rotation, and validated the effectiveness of the model. The stress point, stress conduction direction and stress value in the stress area in the backward fall state were collected as loading conditions, and the finite element model of human thoracolumbar segment was given for finite element analysis. Results: In the backward fall experiment simulated by Anybody Modeling System, the volunteer fell backward unconsciously, and the sacrum was the first part to land; the total impact time between the hip and the force platform was 1.14s, and the maximum impact force was 4056N; the model took the ischial tubercle as the force loading point, and the sacral part was mechanically loaded to the upper vertebral body along the long axis of the spine. The finite element results showed that the stress conduction was mainly concentrated in the T11-L2 segment, in which the average stress at the anterior edge of the vertebral body was 16.6MPa, the average load of the upper and lower articular process was 25.4MPa, and the average stress concentration at the lamina and the connection between the pedicle and the vertebral body was 26.2MPa. Conclusions: During falling backward, there was higher stress on the thoracolumbar segment, and therefore the risk of fracture was higher.