Objective To discuss the effects of implants of different thread face angles on the primary stability of immediately loaded implant using the 3-dimensional finite element analysis with the models of the immediately loaded implants. Methods Using the commercial code of Pro/E software, Hypermesh software, and ABAQUS software we created 3-dimensional finite element models. The micromotions of the finite element models with different screw face angles (V-shape, buttress, square-shape and inverse buttress) were computed with the ABAQUS software. Results Concerning different thread face angles, the micromotion of buttress implant was the minimum and the micromotion of inverse buttress implant was the maximum with vertically loading; the micromotion of inverse buttress implant was the minimum and the micromotion of buttress implant was the maximum with horizontal loading. Conclusions Different screw-types have great influence on vertical interfacial micromotions but little influence on horizontal interfacial micromotions. There are two angles which are formed by top /bottom edge and the implants. The larger are the angles, the smaller are the vertical interfacial micromotions, but the weaker of the strength. Thus in designing the screw-type implants, we should consider the angles of thread faces and the strength.

Sit-stand movement is one of the most common movement behaviors of the human body. The knee joint is the main bearing joint of this movement. Thus, the dynamic analysis of knee joint during this movement has deeply positive influences. According to the principle of moment balance, the dynamics of the knee joint during the movement were analyzed. Furthermore, combined with the data obtained from optical motion capture and six-dimensional ground reaction force test, the curve of knee joint torque was calculated. To verify the accuracy of the analysis of dynamic, the human body model was established, the polynomial equations of angle and angular velocity were fitted according to the experimental data, and the knee joint simulation of the movement was carried out. The result revealed that in terms of range and trend, the theoretical data and simulation data were consistent. The relationship between knee joint torque and ground reaction force was revealed based on the variation law of knee joint torque. During the sit-stand movement, the knee joint torque and the ground reaction force were directly proportional to each other, and the ratio was 5 to 6. In the standing process, the acceleration first increased and then decreased and finally increased in reverse, and the maximum knee torque occurred at an angle of about 140°. In the sitting process, the torque was maximized in the initial stage. The results of the dynamics analysis of knee joint during sit-stand movement are beneficial to the optimal design and force feedback control of seated rehabilitation aids, and can provide theoretical guidance for knee rehabilitation training.
Humans ; Hip Joint ; Biomechanical Phenomena ; Movement ; Knee Joint ; Torque