Учебники / Middle Ear Mechanics in Research and Otology Huber 2006

The postero-superior compartment of the middle ear cleft, situated above the diaphragm, includes the epi and retro-tympanum, aditus ad antrum, antrum and mastoid gas cell system. It is covered by a richly vascularized cuboidal epithelium, mainly devoted to gas exchange. It consists of a rigid chamber, and an open, non ventilated gas-pocket which communicates with the antero-inferior compartment by way of both openings. It is probably the site of predilection of viral haematogenous infections.

An inflammatory process involving the mucosa of the postero-supe- riormiddleearcleftcompartment,causesproblemsintheexchangeofgas, leading to the development of a “gas deficit” in the middle ear cleft and, later on, to the development of a tympanic membrane retraction pocket, which could eventually deteriorate into cholesteatoma.

3.2 Surgical inferences

Simple mastoidectomy is not su cient. An antro-attico-mastoidectomy, takingcaretopreservethescutumandtheposteriorbonycanalwall,and,if necessary, completed with the posterior tympanotomy, must be performed with the aim of restoring the function of gas exchange to the postero-supe- rior part of the middle ear cleft.

References

1.Ars B., Ars-Piret N., Morphofunctional partition of the middle ear cleft.ActaOto- Rhino-Laryngologica Belgica, 51 (1997) pp. 181–184

2.Ars B., Middle Ear Cleft: Three structural sets, two functional sets. Otorhinologaryngol. Nova, 8 (1998) pp. 273–276

3.Ars B., Ars-Piret N., L’ oreille moyenne: trois ensembles structurels; deux ensembles fonctionnels. Revue o cielle de la Société française d’O.R.L. 52(6) (1998)

328pp. 27–32

4.Ars B., Ars-Piret N., Compartimentation morpho-fonctionnelle de l’oreille moyenne. Journal français d’ Oto-Rhino-Laryngologie. (Lyon) 47(2) (1998) pp. 82–88

5.Ars B., Pathogenesis of Acquired Cholesteatoma, In: Pathogenesis in Cholesteatoma, edited by B. Ars, Kugler Pub., The Hague, The Netherlands (1999) pp. 1–18

6.Ars B., Middle Ear Cleft Atelectasis. In: Cholesteatoma & Ear Surgery, edited by J. Magnan, A. Chays, Label Production Pub. (2001) pp. 279–293

7.Ars B., Balance of Pressure Variation in the Middle Ear Cleft. In: Fibrocartilaginous eustachian tube – Middle ear cleft., edited by B. Ars, Kugler Pub., The Hague, The Netherlands (2003) pp. 57–66

8.Chatellier H. P., Lemoine J., Le diaphragme inter-attico-tympanique du nouveauné. Ann. Otolaryngol. Chir. Cervico-Fac. (Paris) 13 (1946) pp. 534–566

9.Proctor B., Attic-Aditus block and the tympanic diaphragm. Annals of Otology,

Rhinology and Laryngology 80 (1971) pp. 371–376

10. Palva T., Johnsson L. G., The epitympanic compartments, surgical considerations. Ann. J. Otol. 16 (1995) pp. 505–513

11. Proctor B., The development of the middle ear spaces and their surgical significance. J. Laryngol. Otol. 78(7) (1964) pp. 630–649

12. Ars B., Wuyts F., van de Heyning P., Miled J., Bogers J., Van Marck E., Histomorphometric study of the normal middle ear mucosa. ActaOtolaryngol.(Stockh)117 (1997) pp. 704–707

13. Matanda R., Van de Heyning P., Bogers J., Ars B., Behaviour of middle ear cleft mucosa during inflammation: Histomorphometric study. Acta Oto-Laryngol. 126 (2006) pp. 905–909

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LASER DOPPLER VIBROMETRY DATA OF THE CLIP PISTON MVP

A. Arnold, Ch. Stieger, R. Häusler

Dept. of Otorhinolaryngology, Inselspital, Universität Bern, 3010 Bern, Switzerland Email: Christof.Stieger@dkf.unibe.ch

Keywords: malleus grip stapedectomy, malleo-vestibulopexy, prosthesis, laser Doppler vibrometry

Introduction: A new malleus handle prosthesis for malleo-vestibulopexy and revision stapedotomy has been used successfully for the last two years. A CliP®-mechanism facilitates attachment to the malleus handle and a ball joint provides easy position adjustment intra-operatively. The present study was devised to determine if the ball joint of the CliP Piston MVP specially developed by Haeusler causes a loss of sound transfer from the malleus grip to the vestibulum.

Methods: A middle ear model was set up, consisting of a vibrator normally used in an active implantable hearing device with a metal arm in the shape and size of an actual malleus handle, where the CliP Piston MVP was attached with the ball joint bent to an angle of about 120°. The piston was dipped into the hole of a plastic container filled with water, simulating a piston hole in the footplate. A second hole served as the round

330window.Theexcitationlevelwasmorethan110 dBSPLforfrequenciesbetween100Hz –10000 Hz. The movements were picked up at di erent spots above and below the ball joint with a laser Doppler vibrometer. Vaseline simulated slight fibrosis around the piston in a second measurement.

Results:The overall characteristics of sound transfer were virtually identical above and below the ball joint (di erence < 3dB). Additionally, biphasic resonance peaks (5-10 dB) were observed around 1000 Hz.

Discussion: Our results show very stable transfer properties over the frequency band. Theresonancepeaksof5–10dBareveryprobablybelowalevelofsignificanceinclinical pure tone audiometry. This is in accordance with our clinical practice experience.

Conclusion: The ball joint of the CliP Piston MVP has good transfer characteristics with virtually no loss.

1. Introduction

Malleo-vestibulopexyormalleusgripstapedotomyisemployedforpatients with otosclerosis, either as a primary procedure or as a revision stapes surgery.

Thetechniqueofmalleusgripstapedotomyiscomplicatedbythevarying angle and distance of the malleus handle and the distance from the oval window. This is in contrast to a standard incus stapedotomy, where the incus prosthesis is clamped onto the long process of the incus and oriented vertically to the oval window.

The new malleus handle prosthesis for malleo-vestibulopexy and revision stapedotomy has been developed in our department and used successfully during the last two years. The piston prosthesis features a ball joint for easy and accurate positioning of the piston on the oval window intra-operatively. The CliP®-mechanism, modified from the àWengen Clip [1], facilitates attachment to the malleus handle.

The study was devised to determine if the specially developed ball joint of the CliP Piston MVP causes a loss of sound transfer from the malleus grip to the vestibulum.

2. Material and Methods

2.1 MVP cliP prosthesis

The MVP CliP Piston by Häusler is a new malleus grip prosthesis and is characterized by the following features: 1) a clip which obviates the need for the usual crimping and can easily accommodate the malleus handle; the rear of the clip bears a convenient tab for easy grasping with forceps and sliding for secure attachments; 2) a ball joint connection bendable for adjustment of the angle; 3) rounded piston edges to minimize connective tissue adhesion and trauma to surrounding tissues; and 4) titanium con-

struction (ASTM F67 medical grade), diameters of 0.4 mm and 0.6 mm 331 and length from 5.25 to 6.25 mm (0,25mm-increments). The prosthesis is grasped by the tab on the rear end of the clip and carefully slid onto the malleus handle. Once the attachment is secure, the angle is adjusted by stabilizing the upper component and pushing the piston medially towards the

oval window. In this experiment a piston of 0.4 mm in diameter and 5.25 mm in length was used.

Fig. 1 CliP Piston MVP by Haeusler.

2.2 Model

A middle ear model was set up. It consists of the vibrator of an active implantable hearing device [2]. A hermetically sealed electro-mechanical system drives a tiny rod which features a metal arm in the shape and dimension of an actual malleus handle. The CliP Piston MVP was attached on this artificial malleus handle with the ball joint bent to an angle of approximately120°.Thepiston was dippedintoaholewhich has asizecomparable to that of a stapedotomy piston hole. A plastic container filled with water representedtheinnerearfluid,thusthepistonwasdirectlycoupledtofluid, representing qualitative simulation of the cochlear impedance. A second hole served as the round window (Fig. 2).

In order to simulate the higher impedance of a slight fibrosis around

332the stapedotomy site in a second set of measurements, the piston was sealed with Vaseline at the piston hole.

2.3 Laser Doppler Vibrometer (LDV) measurements

To investigate the performance of the ball joint the Clip piston MVP was mechanicallyexcitedandthevibrationsaboveandbelowtheballjointwere measured. The excitation level was more than 110 dB SPL for frequencies between 100 Hz–10000 Hz. Displacements above and below the ball joint were measured with a Laser Doppler Vibrometer (Polytec, HLV). Measurementswereaveragedfiftytimes.Theresultswereconfirmedwithrepetition of the experiment for each setup (without and with Vaseline). Noise floor was measured at the end of the experiments.

Fig. 2 Setup of the Laser Doppler Vibrometer measurements.

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3. Results

Figure 3 and 4 show the displacement amplitude above and below the ball joint,withrepeatedtestsforeachsitemeasured.Infigure3,theMVPpiston Clip was not sealed with Vaseline at the point in which it was sealed in figure 4. In both cases, the measurements above and below the ball joint were virtually the same (mean deviation < 3dB for frequencies above 300 Hz). A resonancepeakwasobservedat1500Hz.Anadditionalbiphasicresonance peak (5–10 dB) was observed around 1000 Hz when the CliP piston MVP was not sealed with Vaseline. The dotted line denotes the idealized stapes displacementforanexcitationof100dBSPL.AllMVPmeasurementswere above the noise.

Fig. 3 Displacement above (bold grey lines) and below (black lines) the ball joint of the CliP Piston MVP and idealized middle ear function at 100 dB SPL (dotted line). Single test repetition is shown by two lines for each site measured. Noise floor is depicted by the lowest line.

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Fig. 4 Displacement above (bold grey lines) and below (black lines) the ball joint of the CliP Piston MVP with Vaseline applied around the piston and idealized middle ear function at 100 dB SPL (dotted line). Single test repetition is shown by two lines for each site measured. Noise floor is depicted by the lowest line.

4. Discussion

Ourresultsshownoevidentloss ofball jointsoundtransferof theCliPpiston MVP by Haeusler over the entire frequency band. The resonance peak at 1500 Hz is in accordance with the resonance peak of the vibrator. The biphasicresonancepeakat1000Hzisprobablycausedbytheflexuralmode of the CliP piston MVP. However fibrosis (scarring) at the oval window, which was simulated using Vaseline around the piston, seems to dampen resonance peaks and to reduce the loss in the ball joint.

The additionally noticed resonance peaks of 5–10 dB are very probably below levels of significance in clinical pure tone audiometry. This is in accordance with our clinical practice experience.

5. Conclusion

TheballjointoftheCliPPistonMVPhasgoodtransfercharacteristicswith virtually no loss.

References

1.Grolman W., Tange R.A., First experience with a new stapes clip piston in stapedotomy. Otol Neurotol. Jul; 26(4) (2005) 595–8

2.Stieger C., Bernhard H., Haller M., Kompis M., Häusler R., A novel implantable hearing system with direct acoustical cochlear stimulation (DACS). In: EMBEC; 2005; Prague: IFMBE Proceedings, Vol. 11; 2005

3.Voss S.E., Rosowski J.J., Merchant S.N., Peake W.T., Acoustic responses of the human middle ear. Hear Res. 150(1–2) (2000) 43–69

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