Diseases of the ossicular chain most often occur as an aftermath of infection and less commonly due to trauma or tumor. Conductive hearing loss may result from either discontinuity of the chain or its fixation due to fibrosis or dystrophic calcification (tympanosclerosis). In chronic otitis media, with or without cholesteatoma, the portions of the chain most vulnerable to erosion are the long process of the incus followed by the stapedial arch. The stapes footplate is seldom breached by infection, although it may be involved by cholesteatoma, by inflammation (granulation tissue or polypoid mucosa), or both. In chronic otitis media, the umbo is often medially rotated narrowing the tympanic cavity or even compartmentalizing it into anterior and posterior segments. Before ossiculoplasty, the malleus should be forcibly lateralized. Dividing the tensor tympanic tendon helps maintain the lateral position after repair.

Most frequently disrupted in blunt trauma are the incudostapedial joint followed by massive dislocation of the incus (both incudostapedial and incudomalleolar joints) and less commonly stapes arch fracture. The malleus and stapes footplate are not commonly fractured. A rule of thumb is that in both trauma and chronic otitis media, the incus is most vulnerable.

The most common biocompatible materials used in ossiculoplasty today are titanium and hydroxyapatite. Plastics (e.g., porous polyethylene) were popular in the past but are not commonly used today. Autologous bone such as a reshaped incus body or malleus head are generally less stable and give less reliable results than more mechanically stable artificial prostheses. Most surgeons would prefer not to reposition an ossicle which had been involved with cholesteatoma for fear of residual disease. As a general rule to reduce the chance of extrusion, cartilage should be interposed between the tympanic membrane and ossicular replacement prostheses. It is prudent to use a large piece of cartilage designed to completely underlay the posterior-superior quadrant of the tympanic membrane.

There are myriad designs of ossicular replacement prostheses. Thematically, most are either partial (replacing malleus and incus and connecting to the stapes superstructure) or total (replacing all three ossicles and resting on the stapes footplate). Partial prostheses, which clasp onto the capitulum of the stapes, are generally more stable. Total prostheses which sit on top of the oval window are inherently less stable. To enhance stability, some surgeons place a cartilage block in the oval window niche with a hole to seat the prosthesis. Some two-component total systems use a footplate shoe. While the importance of a remaining malleus handle is debated, some use prostheses designed to attach to the umbo which may afford greater stability. However, the malleus handle in chronic otitis media is often medialized and anteriorly rotated to an unfavorable angle. Other prostheses span minimal defects such as the incudostapedial connection, a defect sometimes repaired with glue which hardens into a rigid solid.

In contrast to the high success rates with tympanoplasty, durable hearing improvement with ossicular chain reconstruction is less reliably achieved. Failure may be early or late. Early malfunctions are most often from a lack of mechanical stability. Properly sized and positioned prostheses remain vulnerable displacement from even minor head trauma or forced ear inflation until they are locked into place by an enveloping mucosal membrane which takes several weeks to develop. Late deterioration may result from scar displacement, fixation of the prosthesis by scarring or dystrophic calcification, or further biological impairment of the middle ear cavity due to recurrent infection. While substantial hearing improvement is achieved in approximately 80% of partial and 50% or total reconstructions, early improvements all too often deteriorate over time. Most of the “long-term” outcomes reported are with only 1 or 2 years in follow-up with few studies reporting outcomes of ≥5 years.

Ossicular fixation, which may occur with or without concomitant tympanic membrane perforation, is a special problem. Epitympanic fixation of the malleus head and/or incus body due to scarring from infection has a high risk or refixation if it is merely mobilized by breaking its adhesive bands. It is better to remove the lateral ossicles, leaving the umbo in place and reconstructing directly to the stapes. Tympanosclerotic stapes fixation is considered in Chapter 4, section 4.9 Tympanosclerotic Stapes Fixation.

Success with ossiculoplasty is related to the health of the middle ear mucosal envelope. This is why results are superior after traumatic ossicular injuries than those associated with infection, which often has an underlying tendency to recur. When the middle ear mucosal lining is compromised, many surgeons stage the procedure preferring to undertake ossiculoplasty months later when the mucosal envelope has improved.

6.2 Patterns of Ossicular Deficiency

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