Changes of incudostapedial joint angle in stapedotomy: does it impact hearing outcomes?

Purpose The aims of this article are: (1) is there an ideal incudostapedial joint (ISJ) angle after stapedotomy? (2) is there any difference between pre- and postoperative ISJ angle? and (3) what is the significance of the ISJ angle in postoperative hearing outcomes? Methods Forty six ears from 39 different adult patients (28 women and 11 men; 21 left and 25 right ears) with a mean age of 39 years with clinical otosclerosis who underwent stapedotomy between May 2017 and May 2019 were retrospectively registered, including seven bilateral surgery cases. ISJ angle and intravestibular depth of the stapes prosthesis were measured from multiple planar reconstruction-computed tomography images and the length of the prosthesis was measured during surgery. Relationships between the ISJ angle parameters and postoperative hearing outcomes and parameters of the prosthesis were analyzed. Results The mean ISJ angle was 93.3 degrees +/- 8.8 degrees preoperatively and 101.9 degrees +/- 6.3 degrees postoperatively, increasing by 8.6 degrees during stapedotomy (p < 0.01). There were weak and negative correlations between ISJ angle changes and postoperative air conduction gains at frequencies <= 1 kHz and bone conduction gains at 0.5 kHz. When the postoperative ISJ angle changed more than 20 degrees, the success rate of the procedure decreased to 0%. Conclusion The stapedotomy operation increased the ISJ angle. The success of postoperative auditory outcomes had more to do with the ISJ angle change than the value of the angle itself, indicating there is no universal ideal ISJ angle that surgeons should aim for during stapedotomy.