11Ossiculoplasty in Tympanosclerosis

FWhat tympanosclerosis is, and why it matters

Tympanosclerosisis the scarred end-stage of chronic or recurrent middle-ear inflammation. After repeated bouts of otitis media, the collagen of the submucosa and the tympanic membrane’s fibrous layer undergoes hyalinization and then calcification, laying down chalky white plaques. On the drum these look like a horseshoe of dense white tissue — the familiar “myringosclerosis” — but the plaques that matter for hearing are the ones that creep into the middle ear itself, around the ossicles and the oval-window niche [1999]. It is a post-inflammatory healing process, not a tumour and not an infection, and crucially it is quite distinct from otosclerosis, which is a primary bony remodelling of the otic capsule. Tympanosclerosis is plaque on the chain; otosclerosis is disease of the bone.

The clinical problem is mechanical. A normal ossicular chain is a delicately suspended lever that must move freely to transmit sound. Tympanosclerotic plaque stiffens and ultimately fixesthat chain — welding the malleus head and incus body into the attic, or cementing the stapes footplate into the oval window[1993]. The result is a conductive hearing loss with an intact, often dry drum. Because the chain is fixed rather than broken, this is a problem of too much stiffness, the mirror image of the discontinuity defects covered elsewhere in this chapter. And because the underlying disease is a scarring tendency that does not switch off, the chain has an unwelcome habit of re-fixing after surgery— the single fact that shapes everything about how these ears are managed.

FRecognising fixation before you open the ear

The diagnosis is usually suspected long before surgery. The patient has a conductive hearing lossin an ear that is dry and intact, frequently with visible chalky plaques on otomicroscopy and a history of childhood ear infections or grommets. The audiogram shows an air–bone gap; tympanometry typically shows a reduced-compliance type As curve, because a stiff chain damps the drum’s movement. This is the key contrast with ossicular discontinuity, which classically gives a normal or hypermobile (type Ad) tympanogram and a large gap. Fixation stiffens; discontinuity loosens.

Two pitfalls are worth flagging. First, do not over-rely on a Carhart notch— a dip in bone conduction around 2 kHz — to localise the problem; it is classically a sign of stapes fixation but is far more characteristic of otosclerosis and is unreliable in tympanosclerosis. Second, plaque is multifocaland you frequently cannot tell from the audiogram alone whether the malleus, the stapes, or both are fixed. High- resolution CT may show dense material in the attic or oval-window niche and helps rule out other causes, but the definitive map of fixation is made at surgery, by palpating the chain. The honest pre-operative position is: this is fixation, the cause is probably tympanosclerosis, and the precise level will be confirmed once the chain is exposed.

TMapping the level of fixation

Because the surgical plan turns entirely on where the chain is fixed, it helps to think in the terms of the classic Wielinga–Kerr classification [1993]. Type I disease is confined to the drum and is of cosmetic rather than acoustic interest. The three that matter for ossiculoplasty are:

• Type II — attic fixation, mobile stapes. Plaque fixes the malleus head and/or incus body in the epitympanum, but the footplate moves freely.
• Type III — footplate fixation.Plaque fixes the stapes footplate in the oval window, with a relatively mobile (or absent) malleus–incus complex.
• Type IV — combined fixation. Both the malleus–incus complex andthe footplate are fixed — the most demanding pattern.

The single most important intraoperative manoeuvre is to establish footplate mobility. A fixed attic with a mobile footplate (type II) is a fundamentally different problem from a fixed footplate (types III and IV), and the two demand different operations. Reconstructing a chain onto a fixed footplate achieves nothing, because there is no mobile window for the sound to drive [2000]. The explorer below lets you step through each level and see the strategy it implies.

TThe operation: clear, confirm, reconstruct

The reconstruction follows a logical sequence, and most of the difficulty lies in the tension between two competing demands: you must clear enough plaque to free the chain, yet every scrap of denuded bone and stripped mucosa feeds the scarring that drives refixation. The art is in doing just enough.

After elevating a tympanomeatal flap and mapping the plaque, the fixed components are freed by careful dissection and, where needed, diamond-burr drilling. Once the attic is cleared the chain is frequently found to be disrupted— the fragile incus long process rarely survives the disease and the dissection intact. The surgeon then confirms footplate mobility and chooses the path. For a mobile footplate (type II), reconstruct from the mobile stapes to the malleus or drum with a partial ossicular replacement prosthesis or a sculpted autograft incus, and interpose cartilageunder the drum to resist extrusion in these scarred, poorly aerated ears. For a genuinely fixed footplate (types III–IV), the chain reconstruction alone cannot restore hearing, and a stapedotomyis performed to create a new mobile window — the preferred option over footplate mobilization, which tends to re-fix[2002].

A word on mobilization versus replacement. It is tempting, having freed a fixed but otherwise intact ossicle, simply to leave it mobilized in place. In tympanosclerosis this is a false economy: a mobilized ossicle sits in the same disease that fixed it, and refixation by re-scarring is common. The more durable strategy is to remove the diseased fixation and reconstruct with a prosthesis or autograft, accepting a bigger operation now to avoid a recurrence later [2007]. The same logic makes stapedotomy preferable to stapes mobilization when the footplate is fixed.

CWhat the outcomes show

Tympanosclerosis surgery works, but its results are good rather than spectacular, and they decline as fixation becomes more extensive. The largest long-term series — 203 consecutive ears followed for up to nine and a half years — reported a mean pre-operative air–bone gap of about 31 dB improving to a post-operative mean of about 17 dB, with the gap closed to within 20 dB in roughly two-thirds of patients and, importantly, no dead ears [2002].

The level of fixation is the dominant prognostic factor. In a classified series, the mean post-operative gap was narrowest for attic fixation with a mobile stapes and progressively wider for footplate and then combined fixation [2000]. Where the footplate is fixed, stapedotomyis both safe and effective in experienced hands: gap closure to within 20 dB in about 70% of cases with preserved bone conduction and no significant sensorineural loss in the great majority [2002]. The recurring theme across all of this work is that the middle-ear environment— mucosa, aeration and a dry ear — predicts durable success more reliably than the choice of implant, which is precisely why a scarred tympanosclerotic ear is a difficult host [2001].

CThe high refixation risk and staging

The defining hazard of this operation is refixation. Tympanosclerosis is an ongoing scarring tendency, so a chain that is mobile on the table can stiffen again as the ear heals, and the air–bone gap can drift upward months or years later. This is why mobilization alone is discouraged, why a cartilage shield is used to buttress the reconstruction, and why staging earns its place [2007].

Staging is the deliberate decision to split the work across two operations. It is most attractive in the hardest ears: combined (type IV) fixation, a wet or poorly aerated middle ear, or extensive plaque that leaves large areas of denuded bone. At the first stage the surgeon clears disease, re-lines raw surfaces and re-establishes aeration; at a planned second look some months later, with the ear settled and the mucosa recovered, the definitive — and now more stable — reconstruction is performed. Combining a freshly-opened vestibule (stapedotomy) with a complex chain reconstruction in one sitting, on a hostile ear, is the situation many surgeons most prefer to avoid [2002].

All of this must reach the patient as honest counselling. The message is realistic optimism: hearing improves in most, occasionally dramatically, but the result is variable, the chain can re-fix, and revision or a planned second stage may be needed — outcomes that are stable in the medium term but never guaranteed for life [2002, 2007]. Set against amplification, surgery remains a sound option for a motivated patient with a correctable conductive loss; it simply comes with a clearer-eyed conversation than most ossiculoplasties require. The discipline that defines the whole module is the same throughout: find the level of fixation, clear only what you must, confirm the footplate, reconstruct rather than merely mobilize, protect the repair with cartilage and aeration, and counsel for the long game.