Ossiculoplasty, also known as ossicular chain reconstruction, requires dexterity, precision, and a working knowledge of tympano-ossicular anatomy and physiology. In the following chapters of this surgical roundtable discussion, experts in the craft of ossiculoplasty will outline various techniques to manage the full spectrum of ossicular dysfunction found in the chronic ear. To properly grasp and apply the techniques described, it is critical that the reader understands a few essential concepts that dictate how ossiculoplasty is applied and how hearing outcomes should be judged. Furthermore, the material in Chapter 8 (Biomaterials in Tympanomastoid Surgery) and Chapter 9 (Middle Ear Mechanics in Hearing Reconstruction) will further augment the information presented here on ossiculoplasty.
26.2 Middle Ear Environment
Although several factors, such as surgical technique and the qualities of the prosthesis, can affect ossiculoplasty hearing outcomes, there is no question that the condition of the middle ear is the most important determinant of long-term results.1,2,3 Unfortunately, this is also the most difficult concept for both novice and experienced ear surgeons to understand. For example, even the most elegant and meticulously executed ossiculoplasty will be relegated to a poor hearing result if the middle ear space is not aerated postoperatively. By considering these factors during the preoperative assessment, patient stratification, realistic expectations, and informed consent are facilitated.
Although there is no universal agreement as to which factors are most important for success in ossiculoplasty, a review of the available classification schemes on middle ear risk and other reports on long-term ossiculoplasty outcomes will reveal certain trends.1,2,4,5 Specifically, revision surgery, middle ear fibrosis, active middle ear drainage, and underlying untreated Eustachian tube dysfunction appear to impart a worse prognosis. As such, control of some of these factors should be pursued in the preoperative period if possible.
The extent of damage to the ossicular chain will also impact outcomes in that there is an apparent trend toward worse outcomes if the malleus manubrium is absent, even when statistically corrected for underlying disease severity.1,2,5 Benefits of the intact malleus manubrium may include preserved tympanic blood supply, more rapid tympanic membrane healing, a lower rate of eardrum lateralization, and possibly improved acoustic gain if the malleus is incorporated into the ossiculoplasty scheme. Although the status of the stapes superstructure is frequently mentioned as being an important factor due to the stability that it can afford, this is controversial and the role of the superstructure in determining hearing outcomes is not nearly as well established in the literature as that of the malleus manubrium.2,6
26.3 Judging Ossiculoplasty Outcomes
Is a 17-dB air-bone gap a good result after ossiculoplasty? Conventional teaching might say “yes” since many reports in the literature traditionally present hearing outcomes within the premise that success is judged by the percentage of subjects having a postoperative air-bone gap <20 dB. Although the traditional application of bracketed air-bone gap subgroups (≤10 dB, 11–20 dB, 21–30 dB, >30 dB) may be useful in reporting results of stapes surgery where the middle ear environment is consistently favorable, it is not an ideal way to assess ossiculoplasty outcomes in chronic ear disease due to middle ear variability. Reality is that judgment of a 17-dB air-bone gap can only be made within the context of the underlying ear. In a severely affected chronic ear with fibrocystic sclerosis of the mucosa, tympanosclerotic fixation of the ossicular chain, and a previous canal wall-down mastoidectomy, such a result would be quite good. On the other hand, a 17-dB air-bone gap after simple ossiculoplasty in an aerated and stable middle ear cleft should not be considered a particular success.