| Abstract [eng] |
Millions of people experience middle ear problems in their lifetime. In the case of defects in the middle ear's ossicular chain, replacing one or more of the ossicles with a prosthesis is often the only long-term solution. Modern middle ear prostheses can restore hearing to a high standard, but the biggest problem with these prostheses remains the long-term stability. A large proportion of prostheses move out of position or are pushed out of the ear after a while. Recent research is seeking to apply titanium's ability to integrate with human bone to increase long-term stability and reduce the risk of revision surgery. The aim of the project is to increase the long-term stability of the prosthesis. This has been done by designing several variations of the improved prosthesis and by testing their interaction with designed models of the stapes footplate using the finite element method. The results of the contact study were compared with a similar prosthesis described in the literature. When the prostheses are subjected to the same conditions, one of the variations of the improved prosthesis produced the best results with a 25.4% reduction in bone stresses due to the improved positioning of the prosthesis contact points. Using a variation of the prosthesis with the same contact point arrangement as the literature prosthesis, the calculated bone stresses were 8.9% lower than in the literature. Modal and harmonic response analyses were performed for the three prosthesis variations. No significant differences were observed between the three prosthesis variations when comparing the natural oscillation frequencies and displacement values. The values of the stresses in the prostheses were correlated with the results of the contact study. When the displacements of the prostheses were tested at frequencies of 100–5000 Hz, all prostheses reached a maximum displacement of 0.72 μm at 1500 Hz. The maximum displacements were achieved in the middle of the human spoken language frequency range and the distribution curve of the displacements corresponds to the distribution of displacements of healthy middle ear bones. Further studies are recommended to investigate the influence of the shape and dimensions of the prosthesis contact points on the stresses generated in the bone growth on the stapes footplate. |
