Otosclerosis and Stapes Surgery - part 5 potx

Biomechanics of Stapedioplasty in Atmospheric Pressure Changes 147chain, these forces induce a gliding motion in the malleus-incus joint, and due toadditional gliding in the incudostaped

Merchant/Rosowski/McKenna 144

Future Directions

So far, we have not performed surgical repair of SSCD in patients withconductive hearing losses without disabling vertigo because of the risk ofsensorineural deafness as well as the potential risks of middle fossa surgery Wehave repaired SSCD for relief of vestibular complaints via a middle fossaapproach in 12 patients Although no case developed a severe or profound hear-ing loss in our series, a mild to moderate high-frequency sensorineural hearingloss at 4 and 8 kHz occurred in 2 of our 12 cases Our philosophy and recom-mendations may change as we accumulate more experience with surgical man-agement of this condition

The natural history and etiology of SSCD remain uncertain It is interesting

to note that 2 cases in our series with conductive hearing loss without vertigo arebrothers, each with bilateral SSCD, raising the possibility of a genetic predisposi-tion to SSCD We also do not understand why some patients with SSCD becomesymptomatic with primarily vestibular complaints, whereas others present withboth auditory and vestibular symptoms, and a third group has only auditorysymptoms We are hopeful that ongoing clinical and basic research will clarifysome of these issues in the future

2 Minor LB: Superior canal dehiscence syndrome Am J Otol 2000;21:9–19.

3 Minor LB, Carey JP, Cremer PD, Lustig LR, Streubel SO, Ruckenstein MJ: Dehiscence of bone overlying the superior canal as a cause of apparent conductive hearing loss Otol Neurotol 2003;24:270–278.

4 Halmagyi GM, Aw ST, McGarvie LA, Todd MJ, Bradshaw A, Yavor RA, Fagan PA: Superior circular canal dehiscence simulating otosclerosis J Laryngol Otol 2003;117:553–557.

semi-5 Mikulec AA, McKenna MJ, Ramsey MJ, Rosowski JJ, Herrmann BS, Rauch SD, Curtin HD, Merchant SN: Superior semicircular canal dehiscence presenting as conductive hearing loss with- out vertigo Otol Neurotol 2004;25:121–129.

6 Streubel SO, Cremer PD, Carey JP, Weg N, Minor LB: Vestibular-evoked myogenic potentials in the diagnosis of superior canal dehiscence syndrome Acta Otolaryngol Suppl 2001;545:41–49.

7 Rosowski JJ, Songer JE, Nakajima HH, Brinsko KM, Merchant SN: Clinical, experimental and theoretical investigations of the effect of superior semicircular canal dehiscence on hearing mech- anisms Otol Neurotol 2004;25:323–332.

11 Nakashima T, Ueda H, Furuhashi A, Sato E, Asahi K, Naganawa S, Beppu R: Air-bone gap and resonant frequency in large vestibular aqueduct syndrome Am J Otol 2000;21:671–674.

Arnold W, Häusler R (eds): Otosclerosis and Stapes Surgery.

Adv Otorhinolaryngol Basel, Karger, 2007, vol 65, pp 146–149

Clinical Significance of Stapedioplasty Biomechanics: Swimming, Diving,

Flying after Stapes Surgery

Copyright © 2007 S Karger AG, Basel

The middle ear, working as a highly sensitive pressure receptor, not onlytransmits the acoustic sound pressure to the inner ear, but is also exposed toenormous changes of ambient atmospheric pressures: the sound pressure at thepain threshold (114 dB) reaches 10 million ␮Pa, which corresponds to a staticpressure of 1 mm water column (daPa) However, atmospheric pressures of sev-eral 100 mm water column are tolerated by the ear without any problem Ourear is constantly exposed to these pressure changes in daily life, for exampleduring swallowing, with tubal opening, with wind gusts at the external ear, intympanometry or pneumatic otoscopy, during flying, or diving

A pressure change of ⫾400 mm H2O (daPa) displaces the tympanic brane and the malleus inwards and outwards up to 1 mm In the normal ossicular

mem-Middle Ear Mechanics and their Clinical Implications

Biomechanics of Stapedioplasty in Atmospheric Pressure Changes 147

chain, these forces induce a gliding motion in the malleus-incus joint, and due toadditional gliding in the incudostapedial joint, the stapes and consequently theinner ear are uncoupled due to the extensive displacement of the tympanic mem-brane The maximal piston-like inwards and outwards movement of the stapes inthe normal middle ear never exceeds 10–30 ␮m, regardless of the pressure in theexternal ear canal This limited displacement is also due to the construction

of the tympanic membrane with its prearranged radial collagen fibers Withincreasing pressure, these fibers with a high tensile strength stretch and limit fur-ther bulging of the tympanic membrane This results in a decrease of displace-ment of the tympanic membrane even with increasing pressure: the tympanicmembrane behaves like a solid wall at pressures above 500–600 mm water col-umn (daPa) [1]

Displacements of a Stapes Piston in Atmospheric

Pressure Changes

Contrary to the normal middle ear with the stapes solidly attached in theannual ligament, the replacement of the stapes by a piston eliminates this anchor-ing Atmospheric pressure changes, which induce displacements of the tympanicmembrane, can now move a piston practically unrestrictedly in the vestibule (fig 1)

In experiments with 9 fresh temporal bones, pressures of 400 mm H2O, like intympanometry, displaced the pistons an average of 232 ␮m inwards and out-wards In cases of an impaired gliding capacity of the ossicular joints, which isoften found in histological studies in otosclerotic middle ears, this displacement

pis-in revision surgeries for recurrent air-bone gap [2] A very long piston can comeinto contact with or even pierce the underlying structures of the membranouslabyrinth (utricle, saccule) at increased pressure in the external ear canal or with

a retraction of the tympanic membrane and cause vertigo

Considering these excessive displacements and the proximity of the piston

to the inner ear structures, surgery under local anesthesia is recommended Ifthe insertion depth of the piston is 0.5 mm, as has often been proposed in order

to prevent its outward dislocation with sneezing, a test with a gentle pressuredownward of the long process of the incus after positioning of the piston canidentify the maximal inward movement of the piston Shortening of the piston

is necessary, if the patient reports vertigo with this movement This contact ofthe lower end of the piston with the inner ear structures may explain, why incases of postoperative vertigo, even with nystagmus, removing of the tampon-ade of the external ear canal can immediately result in a disappearance of thesymptoms by lateralizing an inwardly displaced tympanic membrane togetherwith a piston Such an irritation by an impaling piston is confirmed, if the feel-ing of vertigo disappears instantly after a cautious valsalva maneuver

Considering these excessive movements, the scraps of connective tissuethat are often placed around the piston in the oval window niche not only serve

as a seal to prevent a perilymphatic leakage, but they can also attenuate thepressure-induced displacement of the piston after healing and scarring due to

Fig 2 Displacement of a piston in the vestibule in relation to the undersurface of the

footplate in tympanometry a ⫺400 mm H2O b ⫹400 mm H2O.

Biomechanics of Stapedioplasty in Atmospheric Pressure Changes 149

their frictional resistance The same applies to the venous or connective tissuegrafts under the piston in the fenestration [3]

Therefore, flying can be permitted approx 2 weeks after stapedioplasty,when this connective tissue seal has matured

Modern passenger jets, flying at an altitude of 12,000 m, keep the pressuredifferential relative to sea level in the cabin at 2,000 mm H2O (daPa) This pres-sure induces excessive displacements of the tympanic membrane even withrepeated tubal openings

A test applying tympanometric pressures of ⫾400 mm H2O (daPa) to theexternal ear with simultaneous recording of nystagmus can reveal, whether fly-ing or diving may be hazardous to patients after stapedioplasty If no vertigo nor

a pathologic eye movement is evoked with pressures of 400 mm H2O, evenlarger pressures should not cause an inner ear irritation, as the stiffening of theradial collagen fibers in the tympanic membrane prevents an increase of thedisplacement Therefore, a prosthesis will not be displaced significantly withfurther increasing pressure These experimental results are confirmed by expe-rience with military jet pilots who continued to fly without problems afterstapedioplasty [4] Stapedioplasty patients even performed diving, whichcauses much larger pressure changes, without any problem

Therefore, it does not seem justified to generally ban pilots, divers, chuters or other people who are exposed to excessive pressure variations fromperforming their work or sport after stapedioplasty A prerequisite for a safeexposure to excessive pressure variations is, however, a pressure test with tym-panometry without symptoms

University Hospital Dresden

Department of Otorhinolaryngology, Fetscherstrasse 74

DE–01307 Dresden (Germany)

Tel ⫹49 351 458 4420, Fax ⫹40 351 458 4326, E-Mail huettenb@rcs.urz.tu-dresden.de

Arnold W, Häusler R (eds): Otosclerosis and Stapes Surgery.

Adv Otorhinolaryngol Basel, Karger, 2007, vol 65, pp 150–154

Finite Element Model of the

Stapes-Inner Ear Interface

of cartilage and is inserted into the complete opened oval window during stapedectomy Our study shows that basilar membrane (BM) displacement is increased with an increasing stapes footplate area by a numerical simulation including the different geo- metries An increase in the footplate area leads to an increase in BM displacement equiva- lent to 13 dB Therefore, we recommend prostheses with areas as big as the normal stapes footplate area.

Copyright © 2007 S Karger AG, Basel

In the year 1958, a new surgical technique for the middle ear, i.e tomy, was introduced [1] It was suggested to be used in patients who sufferfrom otosclerosis, which is a disease impeding the normally most efficientmovement of the structures of the healthy ear It is caused by fixation of for-merly movable elastic or hinged connections of middle and inner ear struc-tures During the following years up to now, the surgeons who usedstapedotomy developed a surgical procedure where a small hole is drilled intothe stapes footplate and a small piston (0.6 mm in diameter) is placed into thehole Although clinical studies show improvements of hearing results with pis-tons of a larger diameter (0.6 mm compared to 0.4 mm [2, 3]), ear surgeonsprefer small prostheses either for practical reasons or because they are used tothem (fig 1)

stapedo-Finite Element Model of the Stapes-Inner Ear Interface 151

Methods

To study the differences between a small piston and a prosthesis with an area similar to the area of a normal stapes footplate (3.6 mm 2 ), an existing finite element model of the cochlea was used and enlarged (fig 2).

At first, an external pressure of 1 Pa [94 dB (SPL)] was applied to the small piston area of only 0.28 mm 2 Then, the same pressure was also applied to the large footplate area

of 3.6 mm 2 , as it was done in one of our former studies [4] However, because this figuration is not realistic, neither for the healthy ear nor for any case of middle ear recon- struction, the loading (1 Pa) was applied to a newly suggested stapes prosthesis shown in figure 3.

con-In this case, the external pressure (1 Pa) was applied to the small area (0.28 mm 2 ) on top

of the prosthesis, as it would be connected to the long process of the incus of the middle ear.

At first, only one harmonic signal of frequency (f ⫽ 2,500 Hz) was used Former studies had shown the maximum increase in basilar membrane (BM) displacement and therefore maxi- mum improvement of hearing for this frequency

c

Fig 1 a Normal b Stapedotomy c Stapedectomy.

Figure 5 shows the BM displacement in the case of a large-area prosthesissuch as that in figure 3 The maximum BM displacement increases to 0.0328 nm,which is equivalent to a gain of 13 dB compared to the small piston case Anotherinteresting fact is the basal shift of the maximum BM displacement in the cochlea(approx 1 mm) We point out that the cochlear model is linear and basal shift hasformerly been found in experiments with increased excitation levels at the eardrum.

Discussion

Our study shows the dependence of the BM displacement on the area of thestapes footplate by modelling the cochlea and numerical evaluation At first, theexamination was limited to one frequency (f ⫽ 2,500 Hz) The consequence ofour results is the recommendation of stapes footplate prostheses which are assimilar to the normal stapes footplate as possible Of course, there are practicallimitations to this, i.e the prosthesis might be tilted during the insertion, and itsunavoidable removal would cause a severe acoustic trauma to the patient

Finite Element Model of the Stapes-Inner Ear Interface 153

An interesting result is the basal shift of the maximum BM displacementwith increasing footplate area Therefore, an enlargement of the stapes footplate

is equivalent to an increase in the excitation level applied at the tympanic brane, because this also leads to a basal shift of the maximum BM displace-ment This was proven by direct measurements of BM displacement with theMössbauer technique [6] Another possibility to verify this result is by psy-choacoustic examinations These should not only verify the decrease in thepure-tone threshold level with increasing footplate areas, but might additionallyshow differing sensation of tone heights with varying size of the prostheses

mem-Fig 3 Stapes prosthesis with a large footplate area.

Böhnke/Arnold 154

Further studies should include all parts of the middle ear, which were ted in this study for simplification These are the tympanic membrane, the threeossicles (malleus, incus, stapes), the three tendons of the malleus, the two ten-dons of the incus and two middle ear muscles (musculus tensor tympani andmusculus stapedius) Of course, these studies should include the whole fre-quency spectrum of hearing and the nonlinear properties of the signal transmis-sion of the middle ear

omit-References

1 Shea JJ Jr: Fenestration of the oval window Ann Otol 1958;67:932–951.

2 Böheim K, Nahler A, Schlögel H, Filzmoser P: Ergebnisse mit Goldpistons bei der Stapedektomie mit kleiner Fensterung Otorhinolaryngol Nova 1997;7:235–240.

3 Teig E, Lindeman HH: Stapedotomy piston diameter: is bigger better? Otorhinolaryngol Nova 1999;9:252–256.

4 Arnold W, Böhnke F, Scherer E: Der Einfluss der Stapesfussplattenfläche auf den Druck in der Perilymphe und die Auslenkung der Basilarmembran Otorhinolaryngol Nova 1999;9:81–86.

5 Böhnke F, Arnold W: Finite element model of the stapes-inner ear interface Int Symp Politzer Soc Otosclerosis Stapes Surg, 2004.

6 Johnstone B, Sellick P, Patuzzi R: Mössbauer measurements of nonlinear basilar membrane placement in guinea pigs Hear Res 1986;147–153.

dis-Frank Böhnke

Department of Otorhinolaryngology

Technical University of Munich, Ismaninger Strasse 22

DE–81675 Munich (Germany)

Tel ⫹49 89 4140 4196, Fax ⫹49 89 4140 4971, E-Mail frank.boehnke@lrz.tum.de

Arnold W, Häusler R (eds): Otosclerosis and Stapes Surgery.

Adv Otorhinolaryngol Basel, Karger, 2007, vol 65, pp 155–157

The Influence of the

Footplate-Perilymph Interface on

Postoperative Bone Conduction

Wolfgang Arnolda, Elefterios Ferekidisb, Karl-Friedrich Hamanna

a Department of Otolaryngology, Head and Neck Surgery, Technical University of Munich, Klinikum rechts der Isar, Munich, Germany; b Department of Otolaryngology, Head and Neck Surgery, University of Athens, Athens, Greece

we recommend total stapedectomy using a Schuknecht steel wire connective tissue prosthesis, which offers a stapes-perilymph interface similar to the normal stapes.

Copyright © 2007 S Karger AG, Basel

Smyth and Hassard [1] reviewed 800 stapedectomies and reported that interms of hearing the small fenestra technique and the total footplate removalwere virtually the same concerning results for air conduction Persson et al [2]compared the findings in 437 ears from patients with otosclerosis who hadundergone partial stapedectomy, total stapedectomy and stapedotomy Partialstapedectomy was performed on 70 ears (16%) and total stapedectomy was per-formed on 205 ears (47%) In both groups, the House steel wire prosthesis onfascia was used On the remaining 262 ears (37%), stapedotomy was performedusing the Fisch 0.4-mm Teflon platinum piston Persson et al [2] reported thatnone of these patients in these series presented with sensorineural hearing loss

Arnold/Ferekidis/Hamann 156

(⬎15 dB) The comparison between the three groups postoperatively showedthat the air-bone gap was smaller for partial and total stapedectomy than forstapedotomy for all frequencies except at 4 kHz Partial and total stapedectomyalso showed a larger improvement in bone conduction thresholds comparedwith stapedotomy for all frequencies except 4 kHz At the 3-year follow-up, thehearing gain for all frequencies (250 Hz to 8 kHz) was larger for partial andtotal stapedectomy than for stapedotomy In 2002, House et al [3] stated thatthe success in stapes surgery depends more on the experience and skill of thesurgeon than on the type of prosthesis used

Since the age of the patients which undergo stapes surgery is increasingworldwide, we have more and more patients who additionally to the loss of airconduction have a moderate to severe sensorineural hearing loss According tothe investigation of Böhnke and Arnold (pp 150–154), there is a rational proofthat the size of contact between the prosthesis and the perilymph has an impor-tant influence on bone conduction

Methods

In a prospective study, the first author performed 165 total stapedectomies using a Schuknecht steel wire connective tissue prosthesis The other authors performed 152 stape- dotomies using a 0.6-mm Teflon platinum piston Six weeks and 3 months after surgery, the postoperative values of bone conduction were measured at the frequencies 250 Hz, 500 Hz,

1 kHz, 1.5 kHz, 2 kHz, 3 kHz and 4 kHz The pre- and postoperative bone conduction data were collected from both groups and a statistical analysis was performed by the Institute of Medical Statistics of the Technical University of Munich

Results

The statistical analysis of pre- and postoperative bone conduction olds from 165 patients with total stapedectomy and 152 patients with stapedo-tomy reveals a significantly better outcome of the total stapedectomy group Thedifference of postoperative gain of bone conduction is demonstrated in figure 1

thresh-Discussion

Our study shows that the size of the footplate-perilymph interface has aninfluence on the gain of bone conduction Since the size of the footplate has adirect influence on sound pressure in the inner ear and on the extension of thebasilar membrane movement, it is obvious that the larger the footplate-perilymph

Influence of the Footplate-Perilymph Interface on Postoperative Bone Conduction 157

interface the larger the gain in bone conduction This effect has also been shown

by à Wengen [4] and Persson et al [2]

We therefore recommend a total stapedectomy using a prosthesis with aninterface to the perilymph similar to the normal stapes At the moment, this isgiven with the ‘old’ Schuknecht wire connective tissue prosthesis

Department of Otolaryngology, Head and Neck Surgery

Technical University of Munich, Klinikum rechts der Isar, Ismaninger Strasse 22

DE–81675 Munich (Germany)

Tel ⫹49 8941 40 23 70, Fax ⫹49 8941 40 48 53, E-Mail W.Arnold@lrz.tum.de

Arnold W, Häusler R (eds): Otosclerosis and Stapes Surgery.

Adv Otorhinolaryngol Basel, Karger, 2007, vol 65, pp 158–163

A Checklist for Surgical Exposure in

Stapes Surgery: How to Avoid

Misapprehension

Thomas E Lindera, Ugo Fischb

a Department of Otorhinolaryngology, Head and Neck Surgery, Kantonsspital Luzern, Luzern, and b ORL-Zentrum, Klinik Hirslanden, Zürich, Switzerland

Abstract

The goal of middle ear exploration in stapes surgery is to identify impairments of tion along the entire ossicular chain The endaural approach with an extended tympa- nomeatal flap and an almost routinely performed anterosuperior canalplasty allow adequate exposure to identify the anterior malleal ligament and process (1), the inferior incudomalleal joint (2), the entire stapes including the pyramidal process (3), and the round window niche (4) With this checklist at hand the otologic surgeon can define the exact location of the hear- ing impairment and choose the proper technique for hearing reconstruction in primary and revision surgeries.

func-Copyright © 2007 S Karger AG, Basel

A variety of surgical approaches to the middle ear have been proposed toperform ossiculoplasties Whereas the retroauricular approach is nowadaysrarely employed, most otologists either use an endaural approach or a transcanalapproach through the ear speculum In a typical otosclerosis patient with a wideexternal ear canal, a straightforward endaural or transcanal procedure may pro-vide sufficient exposure to perform conventional stapes surgery However, athorough appreciation of the normal or impaired mobility of the entire ossicularchain and rare middle ear abnormalities may be overlooked or misinterpretedand their correction remain impossible if the exposure is limited to the ovalwindow niche High-resolution CT scans prior to surgery may already provideinformation on the size and location of the otosclerotic focus and careful analy-sis of each section in the axial and coronal plane can rule out further middleand/or inner ear malformations (e.g dehiscence of the superior semicircular

Stapes Surgery: Development and Techniques

Checklist for Surgical Exposure in Stapes Surgery 159

canal) The surgeon’s appreciation of the intraoperative situs remains the ‘goldstandard’ for evaluating the functional impairment within the middle ear Theanalysis depends on his expertise and the appropriate surgical exposure.Whereas the surgeon’s experience develops over time and increases with hiscaseload, the proper exposure is a matter of technique

In stapes surgery, we have adopted a checklist which is routinely used in allmiddle ear explorations to appreciate the function or impairment of ossicularmovements Based on this checklist, the senior author (U.F.) has modified theendaural approach for stapes surgery as outlined below

Checklist in Stapes Surgery

The following steps are key elements in the evaluation of middle ear tion and are explored and tested routinely in all cases of suspected otosclerosis

func-(1) The Anterior Malleal Process and Ligament

The learning experience from revision stapes surgeries has led to therecognition of total or partial fixation of the anterior malleal ligament Thisclinical entity has been neglected for many years, but has gained attention onlyrecently [1, 2] Histology of temporal bone specimens confirmed its presence inpatients with otosclerosis and it was estimated that in up to 30% of primarystapes surgeries for otosclerosis we may also observe a fixation of the malleustowards the anterior tympanic spine [3] Whereas a total fixation of the anteriormalleal ligament is easily appreciated, a partial fixation is difficult to verify.The only way to test its mobility is visualizing the movements within the liga-ment upon palpation of the malleus in an anteroposterior and mediolateraldirection Normal mobility or total fixation is a straightforward decision Oncepartial impairment of its movements is suggested, separation of the incud-ostapedial joint is performed (see next checklist steps) and the mobility isreevaluated In the presence of a partial or total fixation of the anterior mallealligament in combination with an otosclerotic stapes fixation, a malleostapedo-tomy procedure is performed The analysis of 80 patients undergoing revisionsurgery after stapes surgery demonstrated that partial malleus fixation was pre-sent in 38% [4], indicating that this entity was most likely overlooked at thetime of primary surgery

A perfect view is mandatory to visualize and palpate the anterior mallealligament In the majority of the ear canals in western countries (e.g far morefrequently than in India), the anterior tympanosquamous suture is a prominentbony wall and groove where the skin of the ear canal is tightly attached andthe height of the bone regularly impairs the surgeon’s view onto the anterior

(3) Exposure of the Stapes and the Pyramidal Process

Visualization of the entire oval window niche requires bone removal of theposterosuperior canal wall, extending anteriorly to the exposure of the lowerthird of the incudomalleal joint and inferiorly to the entrance of the chordatympani into the tympanic bone Sufficient bone removal is achieved once theentire stapes tendon and the pyramidal process are identified This canalenlargement not only provides space to illuminate the oval window niche usingthe microscope light source, but also allows enough room to insert the cruro-tomy scissors to cut through the posterior crus once the stapes piston is fixed tothe incus

(4) Visualization of the Round Window

The final point on the checklist is the identification of the round windowniche and membrane The anteroinferior displacement of the tympanomeatalflap allows access to the round window area If possible, the chorda tympaninerve is left attached to the flap in order to keep the chorda away from the sur-gical field until the piston is firmly attached to the incus When removing thestapes suprastructure, the chorda may be separated from the flap to introducethe 2.5-mm hook to fracture the anterior crus The brief identification of theround window niche allows to exclude obliterative otosclerosis reaching theround window membrane and to rule out the rare instance of a congenital roundwindow atresia [6]

Checklist for Surgical Exposure in Stapes Surgery 161

The checklist is summarized in figure 1 The goal of the surgical approach

is to see all 4 elements with only one position of the operating microscope, tered on the stapes footplate To achieve this goal, an enlarged tympanomeatalflap is required and ample bone removal of the antero- and posterosuperiorexternal canal wall becomes necessary The endaural approach with an extendedtympanomeatal flap and a partial canalplasty is therefore our technique of choice

cen-in stapes surgery

The Endaural Approach

The endaural approach requires only a minimal helicotragal skin incisionwhich becomes almost invisible over time [7] Separating the soft tissue fromthe underlying bone enables the placement of two endaural retractors andallows the surgeon to work with both hands without stabilizing any speculumwith his fingers The tympanomeatal flap consists of two parts: the meatal skinflap is elevated before the tympanic membrane is lifted from the sulcus Anysubsequent bony work is finished before entering the middle ear space to avoidcontamination from debris within the external ear canal The meatal skin flaphas been modified to enable access to the anterior malleal ligament (fig 2) Theanterior limb is incised using a No 11 blade anteriorly to the anterior tympanicspine (at 3 o’clock in a right ear, 9 o’clock in a left ear), then medially andcourses in a spiral way laterally over the tympanosquamous suture to end in theendaural incision at the lateral end of the tympanic bone at the 12 o’clock posi-tion (fig 3) The posterior limb of the triangular flap begins at 8 o’clock (rightear) ascending spirally from the tympanic sulcus to the lateral edge of the exter-nal ear canal Once the skin is separated from the bone, any bony overhang

Fig 1 Necessary exposure to evaluate

middle ear function prior to stapedotomy.

Linder/Fisch 162

which may impair the visualization of the anterior tympanic spine is removedwith the drill (or curette) This partial canalplasty has become almost a routineeven in primary stapes surgeries The elevation of the tympanic annulus fromthe sulcus begins at the posterior tympanic spine and includes the pars flaccidauntil the anterior tympanic spine is identified Exposing the short process of themalleus keeps the extended tympanomeatal flap away and allows early determi-nation of the mobility of the ossicles Further removal of bone covering the ovalwindow niche and inferior third of the incudomalleal joint using curettes ordiamond burrs provides the necessary exposure of the middle ear to follow thechecklist before proceeding with the stapes surgery

Conclusion

The endaural approach with an extended tympanomeatal flap and analmost routinely performed anterosuperior canalplasty allows sufficient expo-

Fig 3 New type of endaural incision

providing sufficient exposure to go through the checklist prior to the continuation of the ossiculoplasty.

Fig 2 Previous incision providing

not enough exposure to identify the anterior malleal ligament.