Obliquity of the stapes in otosclerosis: intra-operative observations and implications in stapes surgery

Abstract

Objective: To establish the prevalence of stapes obliquity as observed in otosclerosis patients during stapes surgery by a simple method of intra-operative measurement.

Design: Prospective observational study.

Results: Intra-operative measurements showed that the mean distance (± standard deviation) between the horizontal segment of the facial nerve and stapes crura in 10 cases of otosclerosis was 0.74 mm (± 0.21 mm), whereas in 10 cases of non-otosclerosis the same distance was 0.20 mm (± 0.00). There was no gap (0 mm) between the stapes crura and inferior border of the oval window niche in otosclerotic ears, whereas in non-otosclerotic ears the same distance was 0.13 mm (± 0.05 mm). The differences were statistically significant (p < 0.0001).

Conclusion: Obliquity and downward displacement of the stapes occurs in otosclerosis. It has diagnostic value as a new clinical sign in otosclerosis. The findings correlate with late complications and failures in stapes surgery. Methods to avoid these have been suggested.

Keywords: Anatomy; Otosclerosis; Stapes.