15Planning for Intraoperative Surprises and Prosthesis Readiness

FWhy the decision waits for the microscope

A trainee’s instinct is to settle the operation in clinic: read the audiogram, look at the scan, decide on a prosthesis, and book the case. For ossiculoplasty that instinct is a trap. The single most important reconstruction decision — whichprosthesis to use, or whether to reconstruct at all today — is deliberately deferred until the surgeon has lifted the drum and palpated the ossicular chain under the microscope. Preoperative information narrows the possibilities; it almost never settles them.

The reason is that the things which decide success are mechanical and microscopic. Is the stapes truly mobile, or subtly fixed by a focus of tympanosclerosis you cannot see on a scan? Is the superstructure intact and load-bearing, or eroded to a fragile remnant? Is the mucosa healthy and the middle ear aerated, or fibrotic and airless? None of these is reliably answered by the audiogram or the CT, yet each can completely change the right construct. Modern outcome data make the same point from a different angle: success depends far more on the ear environment and the status of the ossicular remnants than on the brand of prosthesis chosen [2001, 2005].

So the experienced surgeon treats the consent conversation not as a commitment to one operation but as permission to perform the right one for whatever is found. The patient is consented for a range of contingencies, the back table is stocked for all of them, and the final choice is made in the few minutes after the chain is exposed. This module is about how that decision is made, and how to be ready for every branch of it.

FPalpation: the test the audiogram cannot replace

The defining manoeuvre is gentle palpation of the ossicular chain with a fine instrument. The surgeon presses the malleus handle and watches for transmitted movement of the stapes, then palpates the stapes head directly. Two observations matter above all others: whether the stapes moves, and whether that movement produces a round-window reflex— a visible shimmer of the round-window membrane as the footplate pistons and displaces perilymph.

A mobile stapes with a positive round-window reflex is the green light for an onlay reconstruction: a prosthesis bridging onto it will actually drive the cochlea. An immobilestapes head or footplate, or an absent reflex, is a red light — it tells you that no prosthesis resting on that platform will transmit sound, however neat the construct looks. This is why an audiogram showing a large conductive gap is necessary but not sufficient: it quantifies the problem but cannot distinguish a missing incus (fixable) from a fixed footplate (not fixable by a simple onlay). Palpation is the test that separates them, and it can only be done at the microscope.

Two further inspections complete the picture. The surgeon confirms the mucosa is healthy and the middle ear aerated, because a prosthesis placed into a fibrotic, unventilated ear is tethered and prone to extrusion. And the surgeon assesses the malleus— present and well-positioned, or foreshortened and retracted — because keeping the malleus in the reconstruction preserves a more physiological lever and improves long-term stability [1994]. Walk through the logic below.

TReading the defect: the Austin framework

Once palpation has confirmed a mobile stapes and an aerated, disease-free ear, the construct is chosen by what remains of the chain. The enduring shorthand is Austin’s classification, which sorts ossicular defects by the two structures that matter for coupling: the malleus handle and the stapes superstructure [1971]. Kartush later extended it to cover the malleus-absent variants and tied it to the Middle Ear Risk Index [1994].

• Malleus present, superstructure present(Austin Type A) — the favourable, common pattern of an eroded incus. Bridge stapes head to malleus with a partial ossicular replacement prosthesis (PORP) or a sculpted incus autograft, keeping the lever [2005].
• Malleus present, superstructure absent(Type B) — only the footplate remains medially. A total ossicular replacement prosthesis (TORP) spans malleus to footplate.
• Malleus absent(Types C/D) — the prosthesis must couple to the drum or a cartilage graft, losing the malleus lever; these ears carry a guarded prognosis and benefit from cartilage interposition for stability and to resist extrusion.

The governing principle is the same throughout: preserve the most physiological construct the anatomy allows. Incorporating the malleus and a mobile superstructure restores a partial lever and consistently outperforms a bare drum-to-stapes piston, especially at low frequencies. That is why, faced with a usable superstructure, the surgeon reaches for a PORP rather than sacrificing it for a TORP.

The hearing data behind that preference are striking. In Dornhoffer’s cartilage-capped prosthesis series, an excellent result — an air–bone gap of 10 dB or less — was achieved in roughly 69% of PORP reconstructions but only about 35% of TORPs [1998]. The construct that keeps more of the native chain simply hears better.

TWhen the stapes will not move, or the ear is not ready

The hardest intraoperative surprises are the ones that veto the planned reconstruction. The first is an immobile stapes. If palpation reveals a fixed superstructure or footplate with no round-window reflex, neither a PORP nor a standard TORP-on-footplate will help, because the platform itself does not move. The correct response is restraint: confirm the fixation, resist the temptation to force-mobilizean inflamed footplate — which risks fracture, perilymph fistula and sensorineural loss for a usually transient gain — and plan a separate, staged stapes-targeted procedure once the ear is healed and dry.

The second is an ear that is simply not ready: residual cholesteatoma matrix, granulation, dense fibrosis, or a middle ear that will not aerate. A prosthesis placed into this environment is liable to be displaced, extruded, or acoustically tethered by scar, so a technically perfect insertion still fails. Here the disciplined move is to stage— clear the disease, graft the drum, often place Silastic sheeting to preserve a middle-ear space, and return at a planned second stage to reconstruct the chain in a healed, aerated, disease-free ear [2001]. The Bellucci otorrhoea grade and the appearance of the mucosa, confirmed under the microscope, are the cues that tip an ear into the staging pathway [1973].

There is also a useful fallback for the awkward in-between ear. When the superstructure is present but distorted, tilted, or partly eroded so that a PORP will not seat reliably, a TORP placed tympanic-membrane-to-footplate bypassing the superstructurecan give a dependable result independent of the remnant arrangement — one series reported air–bone gap closure to within 20 dB in over 80% of such ears [2021]. Knowing this option exists keeps the surgeon flexible when the anatomy refuses to match the plan.

CArriving armed: prosthesis and back-table readiness

Deferring the decision only works if every plausible branch is already catered for when the drum is lifted. Discovering you need a TORP, or a sculpting burr for an incus autograft, after the ear is open is poor planning. Readiness is the price of flexibility. A well-prepared ossiculoplasty back table therefore carries, as a minimum, PORPs and TORPs in a range of lengths, cartilage harvested and ready to cap a prosthesis or to interpose, a sculpting burr and diamond for an autograft, sizing rods or calipers, and Silastic sheeting for the ear that must be staged.

Cartilage deserves special mention because it solves two problems at once. A cartilage cap between an alloplastic prosthesis and the drum markedly reduces extrusion and improves coupling, and a perichondrial or cartilage shield can protect the oval window during placement [1998]. Length and tension are equally a readiness matter: the aim is the loosest stable construct, firmly seated yet freely mobile, and getting there means having a spread of lengths to try rather than forcing a single prosthesis to fit.

Readiness is also cognitive. The surgeon who has rehearsed each branch — what to do for a mobile superstructure, for footplate-only anatomy, for a fixed stapes, for a hostile ear — makes calm decisions at the microscope instead of improvising. The back table is the physical expression of a decision tree the surgeon already holds in mind.

CChoosing well under pressure

Pulling it together, a few principles separate a confident intraoperative decision from an anxious one. Let palpation, not the plan, have the final word. If the consented PORP meets a fixed stapes, the consent does not oblige you to place it; it obliged you to do the right operation, and the right operation has just changed. The discipline to abandon a plan that the anatomy has vetoed is a mark of maturity, not failure.

Prefer the most physiological construct the ear allows, but no more. Keep the malleus, keep a mobile superstructure, reach for a PORP or autograft incus over a TORP when you can — the hearing gradient between them is real [1998, 2005]. Yet do not contort the anatomy to force a more elegant construct; a dependable TORP bypassing a distorted superstructure beats an unstable PORP [2021].

Respect the ear that is not ready. Active disease, poor mucosa and an unaerated middle ear are reasons to stage, not to press on. A second-stage reconstruction in a healed, dry ear is a planned success; a single-stage reconstruction into a hostile bed is an avoidable failure [2001, 1973]. And throughout, counsel the patient before surgery that the construct — and the possibility of staging — will be settled at the microscope. The patient who understands that the decision waits for palpation is rarely surprised by it, and the surgeon who has arrived armed for every scenario is rarely caught out by it.