When the incus is eroded, broken or absent, the ossicular chain is reconstructed with an incus replacement prosthesis. The one depicted in the adjacent picture is a cylinder with a notch that fits under the handle of the malleus and a circular groove that sits on the head of the stapes.
When both the incus and malleus are eroded or absent, the ossicular chain is reconstructed with a partial ossicular replacement prosthesis (PORP). The one shown in the adjacent picture is a cylinder with a circular flange that fits under the drum. A piece of cartilage is removed from the tragus and inserted between the prosthesis and the inner surface of the drum to minimize rejection
EROSION OF INCUS AND STAPES
When the incus and arch of the stapes are eroded, or when the malleus, incus and arch of the stapes are absent, the ossicular chain is reconstructed with a total ossicular replacement prosthesis (TORP). The one depicted in the adjacent picture has a circular flange that fits under the drum and a slender shaft that is placed over the footplate of the stapes. Again, here, a piece of cartilage is inserted between the drum and the flange.
In this picture of a right tympano- mastoidectomy, a prosthesis has been interposed between the manubrium of the malleus and the capitulum of the stapes.
This picture has been tremendously magnified. In real life, the actual size of the prosthesis is as large as the letter "i" without the dot, seen on a screen at a resolution of 800x600.
In this picture of a left tympanoplasty, the patient's incus was removed, sculptured and interposed between the malleus and the stapes.
The horizontal portion of the facial nerve is seen medial to the head of the malleus. The stapedius tendon is also seen emerging from the pyramidal eminence.