8Managing Malleus Head Fixation and Epitympanic Disease

FThe chain that moves at the wrong end

Most ossiculoplasty modules deal with a chain that has been broken— an eroded incus, a lost stapes arch, a gap that needs a strut. Malleus and epitympanic fixation is the mirror-image problem: the chain is anatomically continuous, yet sound still does not reach the cochlea because part of it is locked solid. The classic site is the epitympanum — the attic above the level of the drum, where the bulky head of the malleus and the body of the incus sit suspended by ligaments. When that bony mass becomes welded to the surrounding attic wall, the manubrium and drum can still vibrate, but the energy is damped against an immovable fulcrum and a conductive hearing loss results [2002].

The result is a deceptively normal-looking ear: an intact, mobile-appearing tympanic membrane, an aerated middle ear, and an air–bone gap that the trainee instinctively blames on the stapes. Recognising that the obstruction lies abovethe drum — in the malleus head or incus body rather than the footplate — is the first and most important step, because the surgical answer is completely different from a stapedotomy. Bony fixation of the malleus head to the anterior epitympanic wall is found in roughly 1.6% of primary stapedectomy explorations, so every otologist who opens an ear for conductive loss will eventually meet it[1976].

FWhere the epitympanic mass gets tethered

Fixation is not one disease but a final common pathway. Histopathological series resolve it into a few recurring patterns [2002, 2006]:

• Anterior mallear ligament fixation.The anterior mallear ligament, which normally suspends the malleus head and runs to the anterior epitympanic wall, becomes scarred and then calcified. The ligament hardens into a rigid tether even when the bone itself looks normal — the commonest acquired mechanism [2002].
• Bony bridge to the attic wall. New bone or a tympanosclerotic plaque welds the malleus head directly to the lateral or anterior epitympanic wall (the scutum and cog region), producing frank bony ankylosis [2006].
• Tympanosclerotic encasement of the incudomallear joint. Chalky tympanosclerotic deposits, the burnt-out scar of chronic otitis media, encase the incus body and incudomallear joint, fixing the whole epitympanic complex as a single immobile block [2015].

The underlying causes span a spectrum: post-inflammatory remodelling after chronic otitis media, tympanosclerosis, healed cholesteatoma, and an apparently congenital or idiopathicform in ears with no inflammatory history. Otosclerosis deserves special mention — the same otospongiotic process can stiffen the anterior and superior mallear ligaments, so a fixed malleus and a fixed footplate sometimes coexist, a trap that explains persistent gaps after an otherwise perfect stapedotomy [1999].

TSuspecting fixation before and during surgery

Malleus fixation is notoriously hard to diagnose preoperatively, and much of the literature is a catalogue of surprises found at surgery [1999]. Still, a pattern can raise suspicion. The audiogram shows a conductive air–bone gap— usually moderate, often largest in the low and mid frequencies — behind an intact tympanic membrane with no history pointing to discontinuity. Tympanometry is the useful discriminator: a shallow, stiff type A_S trace suggests fixation, in contrast to the deep, hypercompliant type A_D of an interrupted chain. Acoustic reflexes are typically absent on the affected side [2002].

High-resolution CT may show a sclerotic focus or a bony bridge in the attic, but its sensitivity for subtle ligamentous fixation is limited, so a normal scan never excludes it. The diagnosis is therefore usually confirmed in theatre by direct palpation. The decisive manoeuvre is to test the ossicles segmentally: gently displace the malleus handle and watch the stapes. A normal chain transmits the movement all the way to a visibly pistoning footplate; a fixed malleus head moves stiffly or not at all while the freed stapes below is mobile. Crucially, the surgeon must palpate each ossicle in isolation— testing the stapes alone, then the malleus — because a chain that is fixed above and free below can otherwise be mistaken for a wholly mobile or a wholly fixed system [2004].

TRelease or remove: working the mass free

Once fixation is confirmed, the governing principle is conservation: if the malleus and incus can be liberated without breaking the chain, a released native chain outperforms any prosthetic reconstruction. Access is the first requirement. An atticotomy— curetting or drilling away the lateral attic wall (scutum) — exposes the malleus head, the incus body and the fixation point. A wide, inferiorly based tympanomeatal flap gives the same view from below [1976].

With the mass exposed, two strategies compete:

• Free the chain in situ. Where fixation is a discrete ligamentous or bony bridge, a discreet osteotomy divides it and a small gap is created between the malleus head and the attic wall to discourage re-ankylosis. Armstrong showed this preserves chain continuity in over 90% of cases [1976]. A refinement uses a KTP laser combined with light drilling to vaporise the fixation and carve a 1.5–2 mm clearance around the freed bone, again without removing any ossicle or inserting a prosthesis[2004].
• Mobilise dense tympanosclerosis. When chalky plaque encases the joint, it is carefully peeled or drilled away with a diamond burr under irrigation, cleaning the sclerotic foci off the ossicle without fracturing it — the “canalplasty” technique for isolated malleus fixation [2015].

Two hazards demand respect. First, drilling on a coupled chain transmits vibration to the cochlea; an inadvertent burr touch on a mobile ossicle can cause sensorineural loss, so many surgeons recommend disarticulating the incudostapedial joint first, or using the laser, to protect the inner ear. Second, over-mobilisationcan fracture or luxate the chain. When the mass cannot be freed safely — dense diffuse tympanosclerosis, or bone too welded to divide — the pragmatic choice is to remove the fixed malleus head and incus and reconstruct, accepting that one good problem (fixation) has been traded for a familiar one (a gap to bridge) [2015].

CReconstructing after mobilisation

If the chain has simply been releasedand remains continuous and in line, no prosthesis is needed at all — the great attraction of the laser and osteotomy approaches[2004]. The reconstructive question only arises when the epitympanic mass has been removed. Here the surgeon is back on familiar ground, with one important anatomical asset: the malleus handle and the stapes are usually intact and mobile. That makes a partial ossicular replacement prosthesis (PORP) from the manubrium to the stapes head the natural reconstruction, preserving the malleus-anchored lever that gives the best low-frequency gain.

Several practical points follow. After atticotomy the manubrium may sit slightly displaced, so the prosthesis should be coupled in as vertical and in-line a column as possible; where the handle is medialised, the relocation manoeuvre (sectioning the tensor tympani and anterior mallear ligament to swing it into the stapes axis) restores a clean columella. Because a freshly drilled attic leaves raw, denuded bone— fertile ground for re-ankylosis or for extrusion of an exposed prosthetic head — the freed surface or the prosthesis head should be protected with cartilage or fascia, and the atticotomy reconstructed to restore a ventilated epitympanum [2015]. The non-negotiable prerequisite is a mobile stapes footplate: if the same disease has also fixed the footplate, no amount of malleus work will close the gap, and the plan must add a stapedotomy or be staged[1999].

COutcomes, refixation and judgement

The reward for getting this right is good, durable hearing. Conservative release closes the air–bone gap in the great majority of ears: Armstrong preserved the chain and resolved the loss in over 90% of patients [1976]; the laser-release series brought the mean gap from 33 to 13 dB with no refixation over one to seven years [2004]; and a large incudomallear-ankylosis series closed 77% of ears to within 10 dB[1999]. Where dense tympanosclerosis forced canalplasty-style cleaning rather than simple release, 80% of ears still reached a gap of 20 dB or less at a year[2015].

Three judgements separate success from disappointment. First, do not miss a second fixation: a coexisting fixed footplate (otosclerotic or tympanosclerotic) is the classic reason a released malleus fails to restore hearing, so the stapes must always be tested in its own right [1999]. Second, respect refixation: tympanosclerosis is a scarring disease, and a mobilised joint sitting against raw bone in a poorly aerated ear will often re-ankylose — which is why creating a gap, interposing cartilage, and (when the mass is dense) removing rather than mobilising it are all sound strategies. Third, as everywhere in ossiculoplasty, the ear governs the outcome more than the manoeuvre: aeration, mucosal health and Eustachian function decide durability, and a single well-chosen release in a healthy, well-ventilated cleft outlasts a heroic mobilisation in a hostile one [2006].