Actual CT scanners overestimate stapes piston size, and do not represent a valuable technique for their follow-up, especially in case of complication. Ultra-high resolution has not yet been evaluated in this setting.

Modern temporal bone imaging systems, using 0.5 mm slice thickness, are reputed not yet able to depict the stapes piston position with a sufficient degree of accuracy, as high-resolution CT measurements consistently overestimated intravestibular piston dimensions (width by 44%, length by 6.25%) and vestibular intrusion (by 39%) because of metallic artifacts. . The exact limits of intravestibular depth are also unclear. The "safe" intravestibular prosthesis depth varies widely between studies and has been reported to range from 0.2 to 2.5 mm, so 39% may represent up to 0.9 mm of misestimation. Ultra-high resolution CT (UHR-CT) has improved spatial resolution to 0.12 mm by using ultra-small detector elements (0.25 x 0.25 mm), allowing better visualization of temporal bone structures compared to high-resolution temporal bone CT (HR-CT). However, this technique has not been described for stapes prosthesis measurement.

Inclusion Criteria:

- stapes prosthesis Ultra-high resolution CT available

Exclusion Criteria:

no materiovigilance report available

patients with otosclerosis who underwent stapes replacement by a prosthesis and underwent ultra high resolution CT for follow-up

because CT-scanner are the patient's proprety