Preoperative air-bone gap predicts thick stapes footplate requiring microdrill fenestration in otosclerosis

Objective To evaluate whether preoperative audiometry or computed tomography (CT) findings are associated with intraoperative microdrill conversion for a thick stapes footplate during primary stapedotomy for otosclerosis. Methods Retrospective cohort study of 136 adult primary stapedotomies (2016–2025). Cases were grouped as laser-only (n = 94) versus microdrill conversion due to thick footplate (n = 30); conversions for other reasons were analyzed descriptively (n = 12). Multivariable logistic regression and receiver operating characteristic (ROC) analysis were performed. Results Thick-footplate microdrill conversion cases had a larger preoperative air–bone gap (ABG) than laser-only cases (44.1 ± 9.2 vs 39.4 ± 10.7 dB; p = 0.023). ABG was independently associated with microdrill conversion (adjusted OR 1.05 per dB; AUC 0.64). In the CT subset (n = 72), fissula ante fenestram radiodensity was not predictive (p = 0.83). Operative time was longer with microdrill conversion (75.3 ± 21.5 vs 65.3 ± 15.0 min; p = 0.018). Conclusion Larger preoperative ABG was statistically associated with thick-footplate microdrill conversion, but discriminative performance was modest and should not be used for individual-level prediction. Postoperative hearing outcomes remained favorable with either technique.