# Prediction of Appropriate Prosthesis Length Using Preoperative Computed Tomography in Stapes Surgery With Transcanal Endoscopic Ear Surgery

## TL;DR

This study shows that using preoperative CT scans to estimate prosthesis length can improve hearing outcomes in stapes surgery using TEES.

## Contribution

A novel method for estimating appropriate prosthesis length using preoperative CT in TEES for stapes surgery is proposed.

## Key findings

- In three out of four cases with poor hearing outcomes, the actual prosthesis was shorter than the estimated length from CT.
- Postoperative CT showed inadequate prosthesis positioning in the remaining patients with poor outcomes.
- Preoperative CT-based estimation of prosthesis length may improve surgical outcomes in TEES.

## Abstract

Background

Transcanal endoscopic ear surgery (TEES) is becoming increasingly popular in otologic surgery and can be considered the first choice for stapes surgery. In this study, we analyzed a case series of TEES for stapes surgery, focusing on the estimation of appropriate prosthesis length using preoperative CT based on postoperative hearing results.

Methods

We retrospectively examined 31 patients who underwent TEES using a rigid endoscope for stapes surgeries. Postoperative hearing results were good in 27 cases (87.1%) and poor in four cases (12.9%). We reviewed the preoperative CT scans of all the patients and measured the straight-line distance from the incudostapedial joint to the oval window in the coronal images, assuming it to be the estimated appropriate prosthesis length (eAPL).

Results

The actual length of the prosthesis inserted during the operation was shorter than the eAPL in three of the four cases without postoperative hearing improvement. In the remaining patients, postoperative CT indicated that the prosthesis position was inadequate.

Conclusion

The measurement of the APL using preoperative CT could contribute to improving postoperative hearing outcomes after stapes surgery using TEES.