In vitro evaluation of a malleus head to stapes bead 'incus replica' prosthesis

An ossicular prosthesis produced by making a mould from a cadaveric incus a nd injecting ionomeric cement into it (incus replica prosthesis, IRP) has b een cemented to the malleus head and stapes head and evaluated in fresh hum an temporal bones using a laser vibrometer. Stapes velocity was recorded un der acoustic stimulation and foot plate displacements were derived. Fourtee n frequencies between 125 Hz and 8000 Hz have been used. Measurements were made with the ossicular chain intact, following removal of the incus, with the prosthesis cemented to the malleus, but not the stapes, and with the in cudo-stapedial joint cemented. Tn a second series of experiments the perfor mance of the TRP was compared with that of a Causse partial ossicular repla cement prosthesis, using the same experimental set-up. The results indicate that the prosthesis performs almost as well as the intact ossicular chain and that cementing the incudo-stapedial joint gives better sound transmissi on than leaving it uncemented. In addition the IRP outperforms the conventi onal partial ossicular replacement prosthesis.