9Tympanic Membrane Elevation and Annulus Management

FWhy the drum must be lifted

The ossicular chain lives behind a closed door. To inspect the incudostapedial joint, palpate the stapes, or seat a prosthesis, the surgeon must first open that door — and the door is the tympanic membrane itself, anchored at its rim and gripping the malleus handle down its centre. Elevation is the controlled manoeuvre that lifts the membrane off the malleus and out of the bony groove that holds it, swinging it medially as a hinged flap so the middle ear comes into view. Done well, it is invisible in the result: the drum heals back in place and works as before. Done carelessly, it leaves a perforation, a scarred and stiffened membrane, a numb tongue, or a hearing result worse than the disease that prompted surgery.

That tension — exposure versus preservation— is the whole subject of this module. The membrane the surgeon lifts is also the membrane reconstruction depends on: it must remain mobile, correctly tensioned, and seated in an acute anterior angle to transmit sound efficiently [2016]. Every decision about how far to elevate, where to start, and what to spare is a decision about whether the rebuilt ear will hear. The diagram below frames the central judgement: how much of the annular ring actually needs to be lifted for the task in hand.

FThe anatomy that elevation negotiates

The pars tensa is held at its periphery by the fibrous annulus, a thickened fibrocartilaginous ring that sits in the bony tympanic sulcuslike a watch-glass seated in its bezel. Lifting the annulus out of this sulcus is the act that opens the middle ear. The sulcus is not complete: superiorly the bone is deficient at the notch of Rivinus, where there is no true fibrous annulus and the pars flaccida instead attaches to bone through the anterior and posterior malleal folds[2016]. That superior gap explains why attic and pars flaccida access is raised differently from the pars tensa flap, and why the notch is a favoured site of retraction and cholesteatoma.

Centrally, the membrane is bound to the malleus handle along its whole length, fusing at the umbo. Elevation must therefore free the drum both peripherally (from the sulcus) and centrally (from the malleus), and the relationship to the manubrium matters mechanically as well as surgically: a preserved malleus is among the strongest predictors of a good long-term ossiculoplasty result, so the handle is freed and conserved rather than sacrificed for convenience [2006]. Posteriorly, two landmarks govern safe entry: the posterior tympanic spine, beneath which the chorda tympani crosses, and the close proximity of the facial recess and oval window deep to the posterosuperior annulus.

TRaising the tympanomeatal flap

A tympanomeatal flapis a sleeve of canal skin in continuity with the membrane, raised together so the annulus can be lifted without tearing the drum. After infiltration of the canal skin, two vertical incisions are made in the bony canal — classically at roughly the 6 and 12 o’clock positions for a posterior flap — and joined by a circumferential incision a few millimetres lateral to the annulus. The skin is elevated medially towards the sulcus until the surgeon reaches the annular sulcus, then a fine elevator slips beneath the fibrous annulus and lifts it out of the groove, beginning superiorly behind the posterior tympanic spine where the plane is most reliable [2003].

Three principles distinguish a clean elevation. First, start where the anatomy is forgiving: the posterosuperior sulcus is deep and the annulus well defined, so the plane is entered there and carried inferiorly. Second, stay in the subannular plane— lifting the annulus as a unit with its skin sleeve, not stripping skin off the annulus, which shreds the flap. Third, identify the chorda tympani before it is put on stretch, freeing it from the undersurface of the flap as the annulus comes up. The endoscope has changed the ergonomics of this step: a transcanal endoscopic view of the annulus and posterosuperior recess can be obtained with little or no canalplasty, and with less instrument crowding around the chorda than a microscope down a narrow canal allows[2016].

TThe chorda tympani in the field

The chorda tympaniis the structure most reliably encountered — and most reliably injured — during posterosuperior elevation. It enters the tympanum through the iter chordae posterius near the posterior tympanic spine, runs forward across the medial surface of the membrane between the malleus handle and the long process of the incus, and leaves anteriorly; for much of that course it is adherent to the undersurface of the very flap the surgeon is lifting. Carrying taste from the anterior two-thirds of the tongue, its injury produces dysgeusia, a metallic taste, or oral dryness that patients find genuinely troublesome [2011].

The clinically important point is that severity scales with handling. Pooled and comparative data show taste disturbance rising as the nerve goes from intact, to manipulated, to stretched, to transected, and most symptoms in a preserved nerve resolve over the following year [2011]. Because manipulation is the driver, techniques that reduce it — gentle subannular dissection, freeing rather than retracting hard, and the wider, less crowded endoscopic view — lower the injury rate, with one comparison reporting markedly fewer chorda-related symptoms after endoscopic than microscopic tympanoplasty [2021]. The chart below makes the gradient explicit; deliberate transection is reserved for the rare case where the nerve genuinely bars access to disease, after counselling.

THow far to elevate: single- vs second-stage

The extent of elevation is dictated by the task, not by the approach or the type of mastoidectomy. In single-stage surgery, where a perforated or atelectatic drum must be grafted at the same sitting as the chain is rebuilt, wide elevation is usually required so the graft can be laid as an underlay and supported all round; the anterior edge in particular must be tucked precisely and packed to prevent anterior failure [1967]. The underlay temporalis fascia technique that makes this possible — the membrane elevated, the graft re-draped beneath it — is the foundation of modern tympanoplasty and the reason elevation and grafting are planned as one coordinated operation [2022].

In second-stage ossiculoplasty, by contrast, the drum is already healed and the goal is simply to reach the chain and seat a prosthesis. Here elevation is deliberately conservative, limited to the posterosuperior quadrant or whatever arc the reconstruction demands. Preserving the membrane’s remaining attachment to the sulcus maintains its tension and stability, gives the lateral end of the prosthesis a firm bed, and keeps the natural transformer mechanism intact [2016]. The general rule holds across both settings: lift only as much annulus as the job needs.

CRe-draping, blunting and the anterior angle

Elevation is judged at the end, not the beginning. Once the chain is reconstructed, the membrane is re-drapedinto its sulcus and the flap laid back so the drum heals in its original plane and tension. Two complications dominate the clinician’s attention, and both are functions of how the annulus was handled. The first is lateralisation: a membrane or graft that heals too far laterally, off the malleus, loses its coupling to the chain and the hearing gain is lost. The second is anterior blunting— obliteration of the acute angle between the drum and the anterior canal wall — which stiffens the membrane and dampens its vibration[1967].

Both are most often provoked by disturbing the anterior annulus, the arc between roughly 2 and 4 o’clock on a right ear. The practical doctrine follows directly: do not elevate the anterior annulus unless the reconstruction requires it. For posterior chain work it is left wholly undisturbed; for anterior or subtotal grafting it is lifted last, replaced exactly into its sulcus, and supported with packing to recreate the acute anterior angle rather than allowing the graft to bridge across it[2003]. The anterior tympanomeatal angle is, in this sense, the most unforgiving few millimetres in the operation.

The wider lesson connects elevation to outcome. Long-term ossiculoplasty audits find that most late failures trace not to the prosthesis but to the middle-ear environment and the membrane — recurrent disease, retraction, lateralisation, a foreshortened or stiffened drum [2006]. Elevation is where the surgeon either protects or jeopardises that environment. A flap raised in the right plane, only as far as needed, with the chorda freed and the anterior angle untouched, hands the reconstruction the membrane it needs to succeed; a flap raised wider or rougher than the task demanded mortgages the result before a single prosthesis is placed.