Results:
Fig1. The average postoperative AC-PTA was 46.4dB, which is significantly better compared to the61.5dB preoperative value. ABG-PTA also significantly improved after the surgical intervention:15.9dB vs 31.1dB. No significant difference could be seen between pre- and postoperative BC-PTAs, 30.4dB vs 30.5dB.The minimum of 30dB AC-PTA was achieved in 44% of the cases. In 56%, at least 10 dB ABG gain was achieved, while the 10dB or better ABG closure was 44%, ABG closure between 10-20dB prevailedin 20%. Fig2 Intratympanicfibrosis wasthe most common finding during revision; with a prevalence of 64%, in 32% it was the main reason behind compromised ossicular chain mobility. In the remaining 36%,the main problem was due to surgical failures. The most common prosthesis-related complication was the disconnection between the piston loop and the LPI. Both fibrosis and surgical failure was noticed in 32% (fig2). According tofig2, the highest hearing gains were accomplished in cases where the cause of failure was LPI-prothesis disconnection, while in the cases with adhesions as the primary cause of failure, the hearing gains were the lowest. Fig3
Althought in the presence of intratympanic fibrosis mean ABGgain and hearing gain was lower compared to other cases (fig3a), no statistically significant difference could be found (p=0,087;p=0.095). On this basis,TOST test was performed to determine equivalence. Concerning hearing gain and ABGgain,equivalence was rejected, and the non-inferiority of the intratympanic fibrosis associated negative effect was shown compared to the other group(p=0.94 upper tailed; p=0.037 lower tailed and p=0.94; p=0.03 respectively).
There was no statistically significant difference between preoperative (after primarystapes surgery) ABG and AC PTA levelsacross ’fibrosis’ and ’no fibrosis’ groups (fig3b) (p=0.44 and p=0.96 respectively).