ABSTRACT
Objective To establish the pushing transmission model of tendon-sheath system (TSS) for endoscopic flexible instrument, and study the key influencing factors of transmission efficiency. Methods The force and displacement transmission models of TSS in pushing configuration were built and simulated. The tendon-sheath transmission testing platform was designed to validate the model. The influencing factors, such as transmission velocity, tendon-sheath diameter ratio, curvature radius, were explored using this setup. Results There were obvious nonlinear phenomenon in force and displacement transmission. The model simulation results accorded quite well with the experiment results. Transmission velocity, tendon-sheath diameter ratio, curvature radius all had great effects on pushing force transmission of endoscopic flexible instrument, while they had a smaller effect on displacement transmission. Conclusions The proposed model can be used for calculating pushing force transmission of tendon-sheath system for endoscopic flexible instrument, so as to provide the doctors with force feedback at the tip of the end effector, and ensure the safe operation and improve the surgical effects. For better design and control of endoscopic flexible instrument, the transmission velocity, tendon-sheath diameter ratio, curvature radius must be comprehensively considered.
ABSTRACT
Objective To design a notched flexible articulation applied to electric stapler and study its turning performance. Methods The notched flexible articulation was designed and modeled. The kinematics and statics models of the articulation were established for simulation calculations. The stress, deflection angle, top displacement and driving force of the articulation with 3 different turning structures were studied under equal and variable stiffness of symmetrical notches by using finite element simulation. An experimental platform for performance test of the turning structure was built to verify the simulation results and the model. Results The theoretical model of the turning structure in bending process was basically consistent with the experimental results. With the optimization of symmetrical notch stiffness, the maximum stress of the articulation with variable stiffness was reduced by 20.64% and 39.20%, respectively. The articulation with variable stiffness required the smallest tensile force during bending, which was 33.41% lower than that of the articulation with equal stiffness, and the tip displacement (30.8 mm) along the bending plane was the smallest. The maximum deflection angle for the articulation with 3 different turning structures all could reach 90°. Conclusions The kinematics and statics models of the articulation can be used for the calculation of its tensile force and position changes. The turning performance of the articulation with variable stiffness using symmetrical notch is better than that with equal stiffness. The notched flexible articulation meets the design requirements and the turning needs of electric stapler.
ABSTRACT
Objective By developing a novel endoscopic succession closing device to overcome the shortcomings of existing devices that cannot deploy several clips at one time,to perform structural analysis on different clamp structures and to validate their performances in tissue closure through finite element analysis.Metbods Comparative analyses of 3 clamp structures,namely,the aligning tooth structure (original,clamp A),the staggered tooth structure (clamp B),a combination structure with page break angle and staggered tooth (clamp C),were performed to analyze pressure and its distribution on tissues when clamping the stomach wall.Displacement of 7.5 mm was then applied on the clamps to simulate the effect from operating procedures of the device and tissue kick-back.Results The maximum stresses of the clamp A and B were located on the first pair of teeth which was closest to the rotating shaft,with the stress of 10.39 kPa and 10.11 kPa,respectively.The maximum stress (11.35 kPa) of the clamp C was located on the second pair of teeth.For clamp A and B,the longer the distance to shaft,the larger pressure on stomach tissues.While for clamp C,the pressure on device-tissue interface showed little change along the path.Under tensile displacement,clamp A and B slipped off from the tissue when displacements reached to 5.0 mm and 6.5 mm,respectively,while clamp C did not slip off.Conclusions Clamp with page break angle and staggered tooth can exert the uniform maximum pressure to tissues and provide a larger contact area away from the rotating shaft,thus improving the anti-slippage and performance of the novel endoscopic closing device.