Chapter 20

The roots of ossiculoplasty began in Germany with Wullstein.1 Despite the contemporary belief that any effort to reconstruct the hearing mechanism was doomed to failure, Wullstein was encouraged by results with Teflon prostheses in stapes surgery. His first ossiculoplasty attempts in 1951 utilized a vinyl acrylic prosthesis,² but, due to frequent extrusions, results with allografts were poor. Attention was then focused on the autograft incus, due to its widespread availability and inherent biocompatibility, and the extrusion rate decreased significantly. Based on results with the autograft incus, Wullstein published his now-famous work on the classification of tympanoplasty and established autograft incus as the standard in ossiculoplasty.¹

As this technique gained rapid acceptance worldwide, it was soon discovered that a number of patients did not have an adequate incus for reconstruction. Because of this, utilization of homograft ossicles gained a great deal of popularity by the late 1960s. These ossicles could be banked for a period of time and presculpted for various situations. The first account of such a procedure is from Wehrs³ in 1967. In this review, the homograft incus was used to replace the missing ossicular chain. Results over the next 20 years established the homograft incus as a reliable option for ossicular reconstruction.⁴ In the mid-1980s, however, fears regarding the possible transmission of HIV or prions brought homograft use in the United States to a near halt. Newer sterilization techniques have emerged since that time,⁵ and there is today a renewed interest in homografts as a source of reconstruction material.

Despite initial failures, interest in allograft sources for ossiculoplasty reappeared in 1956 with the work of Shea and Treace.⁶ Like Wullstein’s adaptation of stapes materials, Shea’s first alloplastic implant was based on attempts by Treace to make a stapes implant from Teflon. This first implant was actually composed of Polyethylene 90 and, like Wullstein’s implant, was fraught with complications from extrusion and migration in the middle ear. However, the risk of extrusion using alloplastic implants was reduced to the level obtained with autografts with the invention of Plastipore in 1976 and the addition of cartilage over the prosthesis.⁶

Given that allograft prostheses are easily stored and manipulated, the selection among this group of implants has continued to expand. The list of materials used for allograft prostheses includes hydroxylapatite (HA) (dense and porous), Plasti-pore, Ceravital (E. Leitz Wetzlar GmBh; Wetzlar, Germany), titanium, gold, or any combination of the above. Short-term hearing results with all of these materials have been universally acceptable, with only minor differences in published findings. In a recent review by Goldenberg and Emmet,⁷ alloplastic implants were the most frequently utilized by otologic surgeons performing ossiculoplasty, with the HA prosthesis being the most popular.

The first attempt to stratify patients was performed by Wullstein.1 His classification provided five groups of patients with essentially increasing disease severity based on the amount of ossicular chain remaining. Similarly emphasizing the role of the ossicular chain in predicting outcome, Austin⁸ in 1985 revised Wullstein’s classification to focus on the status of the malleus and stapes. Retrospective data to support his stratification of patients is included in this chapter. Another set of predictive factors was identified by Bellucci⁹ in 1973. Over his many years of experience, Bellucci recognized preoperative drainage as a result of eustachian tube dysfunction and therefore identified drainage as a likely predictor of ossiculoplasty failure. The Bellucci system graded the amount of drainage as none (I), occasional (II), continual (III), and drainage with craniofacial anomalies (IV).

The first attempt to tie multiple patient factors together to predict outcomes and group patients for analysis was that of Kartush.¹⁰ His system examined multiple components of the patient history and surgical findings to stratify results. Although he incorporated the work of Austin and Bellucci, Kartush also included whether or not the surgery was a revision, the status of the middle ear mucosa, the presence of cholesteatoma, the presence of perforation, and the type of surgery performed. All of these factors were scored separately and then summed to produce a total patient score. Unfortunately, results supporting the validity of this scoring system have yet to be published.

Since the work of Kartush, a number of similar systems and multifactorial analyses have been proposed. In 1992, Black¹¹ examined 535 ossiculoplas-ties and produced what was called the SPITE (surgical, prosthetic, infection, tissue, eustachian) method. Significant factors in this review were the complexity of surgery, status of the malleus and stapes, presence of infection, status of the middle ear mucosa, and presence of eustachian tube dysfunction. In 1998, Albu et al¹² reviewed over 500 tympanoplasties and found a similar group of patient factors to be significant in predicting outcomes.

THE OSSICULOPLASTY OUTCOME PARAMETER STAGING (OOPS) INDEX

Uncertain of the statistical validity of previously proposed systems, we examined over 200 ossiculoplasties at our own institution, all of which had been performed by the same surgeon, to determine which factors best predicted outcome. These results were organized into the Ossiculoplasty Outcome Parameter Staging (OOPS) Index, as shown in Table 20–1.¹³ Parameters examined included age, diagnosis, perforation, Bellucci classification score, Austin classification, middle ear mucosa status, preoperative audiogram, canal wall status, surgical procedure, revision status, ossicular status, type of prosthesis used (PORP or TORP), and presence or absence of drainage or fibrosis at the time of surgery. A multivariate analysis of variance was then performed to identify the factors to be most significant in predicting postoperative air bone gaps. Pair-wise comparisons were made to identify the individual factors that were significant. These significant factors were then placed in a multiple linear regression to weigh each factor in its prediction of postoperative air bone gaps. It is important to note that the multivariate analysis allowed all of the parameters to be examined for any significant correlation among them. As we had some concerns that patients with revision surgery might all have significant fibrosis, establishing these factors as independent variables was critical.

Reprinted from Dornhoffer and Gardner,¹³ with permission.

Factors found to be significant were the type of surgical procedure, whether the surgery was a revision, presence or absence of the malleus, presence or absence of drainage, and presence or absence of fibrosis in the middle ear.¹³ Without question, the most heavily weighted of these factors was the presence of middle ear fibrosis at the time of surgery, defined as any mucosal disruption or adhesion between two adjacent structures. Based on these results, all attempts are now made at our institution to minimize fibrosis in the middle ear space, including minimal manipulation of the middle ear mucosa regardless of thickness, minimal use of Gelfoam, and the nearly exclusive use of free-standing prostheses. The least significant of the examined factors was the presence of occasional to severe drainage. As removal of the offending pathology and re-creation of an air-containing middle ear space improves middle ear mucosa, it is to be expected that the effect of drainage on outcome would be minimized when compared to other factors. Our results showed that no two factors identified to be significant in our analysis also had significant multicollinearity.

Many factors considered to be significant by previously published reports were absent in our scoring system. The most notable of these was the status of the stapes in determining outcome. Because the superstructure presents no acoustical advantage, this result seems logical. Another factor noticeably absent from the OOPS index was the diagnosis that led to the surgical intervention. We listed cholesteatoma, chronic otitis, atelectasis, perforation, conductive hearing loss, and any combination of the above as diagnostic parameters. No single diagnosis predicted outcome, unlike the Austin/Kartush system. Another factor absent from the OOPS index was magnitude of the preoperative air bone gap. Although common sense would dictate that a better hearing ear would have fewer comorbidities, and thus a better surgical outcome, than an ear with poorer hearing, there was no trend in the data to support this. As a number of patients undergoing ossiculoplasty have incus necrosis from previous insults or a slipped prosthesis from a previous surgery, outstanding results in the face of a maximal conductive hearing loss negate the preoperative air bone gap as a factor.

The fourth parameter absent from our staging system was the presence of abnormally thickened mucosa. A number of studies to date include thickened or granular mucosa as a poor predictor in hearing outcomes.^10,12

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