The Ossiculoplasty Outcome Parameter Staging OOPS Index

Uncertain of the statistical validity of previously proposed systems, we examined over 200 ossiculo-plasties 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, preopera-tive 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

Table 20 -1 Ossiculoplasty Outcome Parameter Staging (OOPS) Index

Risk Factor

Risk Value

Middle ear factors

Drainage

None

0

Present >/50% of time

1

Mucosa

Normal

0

Fibrotic

2

Ossicles

Normal

0

Malleus/

1

Malleus -

2

Surgical factors

Type of surgery

No mastoidectomy

0

Canal-wall-up

1

mastoidectomy

Canal-wall-down

2

mastoidectomy

Revision surgery

No

0

Yes

2

Reprinted from Dornhoffer and Gardner,13 with permission.

Reprinted from Dornhoffer and Gardner,13 with permission.

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.

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 freestanding 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 cholestea-toma, 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 However, all our patients with abnormally thickened mucosa had similar outcomes to those without thickened mucosa when all other factors were held constant. We believe that the status of middle ear mucosa is similar to that of nasal mucosa, which shows improvement after sinus surgery. Thus, we believe the middle ear mucosa reverts to normal once the pathology is removed.

Utilization of the OOPS index is simple and (similar to the other scoring systems) easy to apply to the individual patient. Prior to surgery, each of the risk factors in the index is discussed with the patient and scored, and the total score places a patient into an appropriate risk group. This allows us to predict the outcomes of the planned ossiculoplasty with a good deal of confidence. In our cohort of 200 patients, we were able to demonstrate a linear relationship between the postoperative air-bone gap and the OOPS index score, which ranged from 1 to 9.

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