The aim of the research was to determine the optimal threadâ??s shape to be used in implants for direct skeletal attachment of limb\nprosthesis. In addition, by testing appropriate parametersâ?? modification of the suitable thread, an attempt was made to maximise its\neffectiveness. The analyses included three thread types described in the ISO standards: shallow, symmetrical, and asymmetrical. The\nobtained results suggest that shallow thread ensures the lowest equivalent and directional stress peaks generated in the bone as well\nas favourable stress patterns and profiles during implant loading in relation to symmetrical and asymmetrical threads. Moreover,\nshallow thread ensured the generation of single equivalent and directional stress peaks, while symmetrical and asymmetrical\nthreads provided additional stress peak for equivalent as well as for each of directional peaks. Subsequently, optimisation of the\nshallow threadâ??s shape was conducted by changing two relevant threadâ??s parameters (flank angle and rounding arc) which\ninfluence the generated stress distribution. The highest reduction of stress peaks was obtained while reducing the rounding arc\nby 0.2 mm. Therefore, it can be stated that the proposed modification of the HA thread can lead to obtaining a higher\nbiomechanical effectiveness of implants for direct skeletal attachment of limb prosthesis.
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