|Beitragstitel||Investigations of the prosthesis's angular position in stapes surgeries: A cadaveric temporal bone study|
In incus stapedotomy surgeries, the longitudinal axis of the piston prosthesis should ideally be perpendicular to the stapes footplate. However, some deviation from the ideal position is unavoidable due to anatomical constraints. This study aims to provide surgical guidelines for prosthesis placement.
A Kurz NiTiBond prosthesis (0.4 mm diameter) and fenestra sizes of 0.5 and 0.6 mm diameter in cadaveric temporal bones (n = 7 including 2 preliminary tests) were used. Angular position of the prosthesis relative to the footplate was modulated by rotating the stapes about its long and short axes. Prosthesis motion was measured using a Laser Doppler vibrometer. Furthermore, a micro-CT data analysis was done to reveal if the tolerances of the angular positions of the prosthesis covers possible positions of prosthesis crimping.
The results showed that changes of the angular position of the prosthesis relative to the stapes footplate do not cause significant changes of prosthesis motion until a certain angular position threshold, and sharply attenuate prosthesis motion beyond this threshold. The threshold of the angular position, as the tilting angle of the prosthesis from the direction normal to the stapes footplate, was 26.9 ± 2.5° with a fenestration hole of 0.5 mm diameter and 30.6 ± 3.0° with a fenestration hole of 0.6 mm diameter (n = 5, p < 0.01 for difference between the two fenestra sizes).
This study suggests that if an anterior offset of the stapes head and/or a thickened footplate is suspected, efforts to locate prosthesis crimping closer to the tip of incus and/or to make a sufficiently large fenestration is favorable.