Mechanical Analysis of Single Shoulder Airbag External Fixator for Clavicle Fractures / 医用生物力学

Objective In view of the problems existing in traditional external fixator, to invent a novel single shoulder airbag external fixator, and evaluate the reductional stretch force produced by it. Methods The three-dimensional finite element model of human clavicle was established. The loading conditions of the single shoulder airbag external fixator and the reductional stretch force produced by the external fixator were analyzed comprehensively and systematically. The actual loading conditions of the single shoulder airbag external fixator and the traditional eight-figure bandage external fixator were compared and analyzed by experiment. Results Reductional stretch force produced by the single shoulder airbag external fixator was more uniform and larger than that produced by traditional external fixator, and could be adjusted by the patient himself. Conclusions The force and the loading method of the single shoulder airbag external fixator on the shoulder were more favorable for the stretched reduction of clavicle fractures and maintaining the position of clavicle fractures, and it could make the patients with clavicle fractures more comfortable.

Simulation analysis on optimial loading scheme of resetting tensile stress for clavicular fracture / 医用生物力学

Objective To investigate the optimal scheme about the external loading of resetting tensile stress for clavicular fracture,so as to provide some mechanical references for optimal design of external fixators for clavicular fracture.Methods The shoulder CT scanning data from a volunteer were used to establish the three-dimensional model of human left shoulder by Mimics software.In order to better simulate the actual human shoulder,the ligament tissues were added in the model and the constraints of muscles were considered,and the experimental model for simulation analysis on resetting tensile stress was established.By 3 simulation experiments,the impacts from directions of resetting tensile stress,positions of action points and value ranges were simulated and analyzed,respectively.The resetting tensile stresses obtained from clavicle of the shoulder model under various external loading cases were simulated by orthogonal test methods.Results When the θ (angle between the horizontal plane projection of shoulder force which was loaded by external fixator and the coronal axis) was greater than 45°,clavicle could obtain the resetting tensile stress,which became greater with the angle θ increasing.When η (angle between the sagittal plane projection of shoulder force which was loaded by external fixator and the sagittal axis) was 30°-45°,the resetting tensile stress of clavicle was the maximum.The farther the position on which the loads from external fixator was exerted from the horizontal position of clavicle,the larger the resetting tensile stress of clavicle was.Conclusions The results of orthogonal test show that the optimal resetting tensile stress is produced with parameter combination of θ =65°,η =50°,acting on the center of humerus head of the shoulder.