Effects of Fenestra Size and Piston Diameter on the Outcome of Stapes Surgery for Clinical Otosclerosis

Abstract

Objectives: We determined the effect of piston diameter (0.8 or 0.6 mm) and fenestra size (total, three-quarter, or half removal or calibrated stapedotomy) on hearing gains after stapes surgery for clinical otosclerosis. Methods: We analyzed the mean air conduction hearing gains at various frequencies in a sample of 911 strictly consecutive patients who underwent 1,168 stapes procedures with piston reconstruction carried out by the same surgeon between 1963 and 1979. Assiduous follow-up of patients was attempted for at least 10 years, and in some cases for 20 years. Results over time at the various audiometric frequencies were stored for computer analysis. Results: There is no apparent advantage of one piston diameter (0.8 or 0.6 mm) over another for hearing gains at 0.25, 0.5, 1, 2, 3, and 4 kHz. The slim piston appeared to have a significant advantage for 6 and 8 kHz at 5 to 10 years after operation, but interpretation here requires caution, because the slim piston was usually chosen for cases with a small fenestra. Of the various sizes of footplate fenestras, total removal of the stapes footplate had significantly worse air conduction results, most clearly demonstrated at higher frequencies. Below 2 kHz, there is only weak evidence that the means differ significantly at all for the different sizes of fenestra. Small fenestras (stapedotomies) appear to offer advantages for hearing gains, particularly at the higher frequencies of 3 to 8 kHz, and for at least 10 years. Conclusions: The diameter (0.6 or 0.8 mm) of the pistons selected for reconstruction after stapes surgery appears to have little effect on the outcome, except perhaps at 6 and 8 kHz, where the slim piston appeared to have a significant advantage. The size of the footplate fenestra is of paramount importance to the outcome. A small footplate fenestra has statistically significant advantages for hearing gain over all other sizes of fenestra (ie, total, three-quarter, or half removal of the footplate), at least for the first 10 years after surgery, at frequencies of 2 kHz and above. Total stapedectomy has given the worst results for hearing gain at frequencies above 2 kHz, and the rate of deterioration of gain over time seems to be more rapid than after small-fenestra techniques. Small fenestras are recommended as the preferred technique in all cases of surgically treatable otosclerosis.