The distance between stapedial footplate and incus in otosclerosis surgery

Background: The measurement of the piston length during stapedotomy is important and it may have significant effects on the surgical outcome.Objective: To determine the piston length in a group of otosclerosis patients who underwent primary stapedotomy.Material and methods: Between Sep 2013 and Sep 2014, 85 patients with diagnosed otosclerosis underwent primary stapedotomy. Teflon prosthesis of 0.6 mm of diameter was used in all patients. The distance between medial surface of the long process of incus and center point of the stapedial footplate measured. The piston length calculated by adding 0.25 mm for the thickness of footplate and 0.50 mm for placement of the prosthesis into the vestibule.Results: The distance between stapedial foot plate and incus ranged from 3.50 to 4.50 mm. The mean distance was 3.95 ± 0.16 mm. In majority of cases(74.1%) piston length was 4.75 mm followed by 4.50 mm in 15.3% and 5.00 mm in 5.9%. Piston length was 4.25 mm in 3.5% and5.25 mm in only 1.2% of patients. There was no significant post-operative complication and air bone gap closure obtained in all patients.Conclusion: The most common distance between foot plate and incus is 4.00 mm. No case needed a piston longer than 5.25 mm or shorter than4.25 mm.