2Malleus-Present, Stapes-Present Reconstruction

FThe most favourable defect pattern

When chronic ear disease breaks the ossicular chain, it usually does so at its most vulnerable link — the long process of the incus, which has the poorest blood supply and dissolves first. What disease tends to spare, by contrast, are the two sturdier ends of the chain: the handle of the malleus, anchored in the drum, and the arch of the stapes, set into the oval window. When the surgeon lifts the tympanomeatal flap and finds both of these survivors present and mobile, with only the incus sacrificed between them, the ear has handed the reconstructive surgeon the best possible starting hand.

This is the configuration that the Austin classification calls type A— malleus handle present, stapes superstructure present — and it is the most favourable of the four ossicular defect patterns [1971]. The task is no longer to rebuild a whole chain from a single survivor, but simply to span a small gapbetween two sound anchors. That gap can be bridged with the patient’s own sculpted incus, with bone cement when the defect is short, or with a short partial ossicular replacement prosthesis (PORP). Whichever is chosen, this is the defect pattern with the best prognosis in all of ossiculoplasty.

FWhy two good anchors matter

The advantage of type A is not luck; it is mechanics. The middle ear is a transformer that matches faint airborne sound to the dense fluids of the cochlea, and a large part of that matching is the ossicular lever— the malleus handle and the incus act as a lever arm that trades movement for force before delivering it to the stapes. A reconstruction that runs from the malleus handle down to the stapes preserves the direction and much of the advantage of that native lever; a column that ends instead on the bare drum behaves more like a simple piston and loses some of that levered amplification, particularly at low frequencies [1994].

Each surviving anchor earns its keep in a different way. The malleus is the more powerful of the two prognostically: it acts as a central tent-pole that gathers the vibration of the whole drum and channels it into the reconstruction, it gives the prosthesis firm lateral support so the construct does not tip or slip, and it aligns the vector of sound transmission. In one large long-term series, a present malleus made a successful result more than six times as likely, and it was the only factor that still independently predicted success five years after surgery [2006]. The black SPITE prognostic scheme likewise singles out the malleus as a critical surgical and prosthetic determinant [1992].

The stapes superstructureearns its keep differently. Its acoustic contribution may be modest in theory — most energy reaches the cochlea through the footplate either way — but in practice an intact, mobile arch lets the surgeon couple ashort prosthesis to the stapes head rather than balancing a tall column on the bare footplate. The short construct is far more stable, easier to seat and far less prone to displacement, which is why partial prostheses to a present superstructure reliably outperform total prostheses to the footplate [2001]. Two good anchors, in short, give a short bridge, a preserved lever and a stable construct — the three things that most strongly predict good hearing.

TChoosing the bridge: incus, cement or PORP

Because the anchors are sound, the decision in type A is simply what to span the gap with, and the answer is driven by how much of the incus survives and how long the defect is. Three options compete:

• Sculpted incus interposition.If the body of the incus is preserved and free of disease, it can be lifted out, notched to seat the stapes capitulum and grooved to receive the malleus handle, and reseated as a strut. This rebuilds the chain entirely from the patient’s own perfectly biocompatible bone, with a near-zero extrusion rate[2005].
• Bone cement rebridging.When the defect is short — a stump of incus long process remaining about 1–2 mm from the stapes — hydroxyapatite or glass-ionomer cement can be moulded across the gap to re-establish continuity without any prosthesis. For these short defects, cement can give slightly better hearing than interposition [2013].
• Short PORP.When the incus is destroyed beyond use, a manufactured partial prosthesis — usually titanium or hydroxyapatite — bridges the stapes head up to the malleus handle or drum. It needs no carving, has a known length, and is the modern default when the autograft is unavailable [2011].

A simple intra-operative rule follows. A short residual long process favours cement; a salvageable, disease-free incus body favours interposition; a destroyed or diseased incus favours a short PORP. What unites all three is that they couple to the stapes superstructure and lean on the malleus — they all exploit, rather than replace, the favourable type A anatomy.

TTechnique: length, angle and tension

Favourable anatomy is not a licence for careless carpentry; in type A the surviving anchors make geometry both possible and decisive. The aim is a bridge that sits as close to perpendicular to the drum as the anatomy allows, so that the prosthesis drives the stapes in a clean piston-like axial motion rather than shoving it obliquely. The head of the construct should sit toward the centre of the drum, near the umbo or the malleus handle, where the membrane vibrates with the greatest amplitude; an eccentric head out near the annulus couples poorly and is less stable [1994].

Length and tensionare the commonest ways to fail a favourable ear. Too short, and the bridge loses contact and the air-bone gap persists; too long, and it splints the chain, stiffening it or even subluxing the stapes, so that the footplate can no longer rock freely. The seated construct should rest with gentle, stable contact at both ends — firm enough not to fall, loose enough to move. Where the malleus is awkwardly medialised or foreshortened, the surgeon may divide the tensor tympani tendon to lateralise the handle and improve alignment, or accept coupling to the drum instead. Finally, when an alloplastic head meets the drum it should be protected by a cartilage interposition— a thin shield that resists extrusion and stabilises the construct — sized to cover the head without smothering the central, most vibratile part of the membrane.

CHearing results and what really drives them

How well does type A reconstruction work? Across the literature, all three bridges give good results in this favourable setting. Sculpted incus interposition closes the air-bone gap to within 20 dB in about two-thirds of ears with no extrusions and stable long-term hearing[2005]; bone cement reaches roughly three-quarters to within 20 dB for the short defects it suits [2013]; and short partial prostheses in intact malleus-and-stapes ears close around 70% to within 20 dB [2011]. These are the best figures anywhere in ossiculoplasty, and they hold up across materials and techniques.

Two cautions keep the numbers honest. First, the series above are not a single head-to-head trial; their case mixes differ, and apparent differences partly reflect which ears each bridge was chosen for. In the Vincent series a tall TORP combined with deliberate malleus relocation and Silastic banding actually edged out the short PORP (about 87% versus 70% within 20 dB), a reminder that meticulous technique and tension can matter as much as the choice of construct, even in a favourable defect [2011]. Second, and more important, the ear matters more than the implant. Staging studies built from large ossiculoplasty series show that the surviving ossicular elements — above all the present malleus and mobile stapes that define type A — together with middle-ear aeration and the absence of active disease, predict hearing far more powerfully than whether the bridge is bone, cement or titanium [2001]. A poorly aerated, inflamed type A ear can still disappoint; a clean, well-aerated one rewards almost any sound reconstruction.

CPitfalls and the modern default

The favourable label can lull. The first pitfall is to sacrifice the survivors: a healthy mobile stapes arch should never be removed to drop in a total prosthesis, because doing so converts the best defect pattern into a worse one. The second is a hidden stapes problem— a superstructure that looks intact but is in fact fixed by tympanosclerosis or otosclerosis will not move however perfect the bridge, so the surgeon must palpate and confirm stapes mobility before reconstructing. The third is reimplanting disease: an incus involved by cholesteatoma must not be reused untreated, since gross inspection cannot exclude microscopic matrix; sterilise it or reach for an alloplastic prosthesis instead.

Which bridge should be the default? In a clean, well-aerated type A ear with a salvageable, disease-free incus, the patient’s own sculpted bone remains an excellent, durable, cost-free reconstruction whose hearing rivals a modern prosthesis. When the incus is destroyed or diseased, or operative time is at a premium, a short cartilage-shielded PORP is the pragmatic modern default, and bone cement is the neat answer to the short residual defect. The unifying principle is conservative and worth stating plainly: in the malleus-present, stapes-present ear, preserve and use the survivors, span the gap with the least elaborate construct that the anatomy allows, and let the favourable mechanics — not the choice of material — do the work [2001, 1994].