Evaluation of a cement incus replacement prosthesis in a temporal bone model

In reconstruction of the ossicular chain for a damaged incus. it is importa nt that the incus replacement prosthesis (IRP) length is ideal in order to provide optimal tension between the tympanic membrane or malleus and stapes head to achieve the best post-operative hearing result. Even though the le ngth of commercially available IRPs can be adjusted, it still may be diffic ult to achieve clinically. We describe: experiments in a human temporal bon e model using dental cement as an IRP after removal of the incus. This ceme nt IRP (CIRP) hardens in situ and becomes the length of the gap to be spann ed so that tension should be ideal. Two different CIRPs were studied. one n as a conventional rod-type CIRP connecting either the umbo or mid-malleus h andle to the stapes head. The second was a Y-shaped CIRP (Y-CIRP), connecti ng two sites on the malleus to the stapes head. The wide Y-CIRP connected t he malleus head and Limbo to the stapes head. while the narrow Y-CIRP conne cted the malleus neck and mid-handle to the stapes head. The acoustic perfo rmance of these experimental CIRPs was studied using a laser Doppler vibrom eter system in 12 fresh human temporal bones. The CIRP demonstrated better acoustic performance than conventional IRPs studied previously in the same model. While all the CIRPs showed similar function below 2.0 hHz, the narro w Y-CIRP appeared best above 3.0 kHz. A prosthesis of this type mag. have a n acoustic advantage over conventional IRPs.